Authors:WendyPowers,MichiganStateUniversity(LeadAuthor)BrentAuvermann,TexasA&MUniversityN.AndyCole,USDAAgriculturalResearchServiceCurtGooch,CornellUniversityRichGrant,PurdueUniversityJerryHatfield,USDAAgriculturalResearchServicePatrickHunt,USDAAgriculturalResearchServiceKristenJohnson,WashingtonStateUniversityAprilLeytem,USDAAgriculturalResearchServiceWeiLiao,MichiganStateUniversityJ.MarkPowell,USDAAgriculturalResearchService
Contents:5 QuantifyingGreenhouseGasSourcesandSinksinAnimalProductionSystems..............5‐5
5.1 Overview...........................................................................................................................................................5‐55.1.1 OverviewofManagementPracticesandResultingGHGEmissions.........................5‐55.1.2 SystemBoundariesandTemporalScale............................................................................5‐125.1.3 SummaryofSelectedMethods/Models/SourcesofData...........................................5‐125.1.4 OrganizationofChapter/Roadmap......................................................................................5‐14
5.2 AnimalProductionSystems....................................................................................................................5‐185.2.1 DairyProductionSystems........................................................................................................5‐185.2.2 BeefProductionSystems..........................................................................................................5‐225.2.3 SheepProductionSystems.......................................................................................................5‐255.2.4 SwineProductionSystems......................................................................................................5‐255.2.5 PoultryProductionSystems....................................................................................................5‐28
5.3 EmissionsfromEntericFermentationandHousing.....................................................................5‐305.3.1 EntericFermentationandHousingEmissionsfromDairyProductionSystems.......
.............................................................................................................................................................5‐315.3.2 EntericFermentationandHousingEmissionsfromBeefProductionSystems.5‐445.3.3 EntericFermentationandHousingEmissionsfromSheep.......................................5‐525.3.4 EntericFermentationandHousingEmissionsfromSwineProductionSystems......
.............................................................................................................................................................5‐535.3.5 HousingEmissionsfromPoultryProductionSystems................................................5‐605.3.6 EntericFermentationandHousingEmissionsfromOtherAnimals......................5‐645.3.7 FactorsAffectingEntericFermentationEmissions.......................................................5‐665.3.8 LimitationsandUncertaintyinEntericFermentationandHousingEmissionsEstimates.........................................................................................................................................................5‐73
5.4 ManureManagement.................................................................................................................................5‐75
Chapter 5Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
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5.4.1 TemporaryStackandLong‐TermStockpile.....................................................................5‐775.4.2 Source:U.S.EPA(2011).Composting..................................................................................5‐815.4.3 AerobicLagoon.............................................................................................................................5‐855.4.4 AnaerobicLagoon,RunoffHoldingPond,StorageTanks............................................5‐865.4.5 AnaerobicDigesterwithBiogasUtilization......................................................................5‐915.4.6 CombinedAerobicTreatmentSystems..............................................................................5‐935.4.7 Sand‐ManureSeparation..........................................................................................................5‐945.4.8 NutrientRemoval........................................................................................................................5‐945.4.9 Solid–LiquidSeparation............................................................................................................5‐955.4.10 ConstructedWetland.................................................................................................................5‐975.4.11 Thermo‐ChemicalConversion................................................................................................5‐985.4.12 LimitationsandUncertaintyinManureManagementEmissionsEstimates......5‐99
5.5 ResearchGaps............................................................................................................................................5‐1055.5.1 EntericFermentation..............................................................................................................5‐1055.5.2 ManureManagement..............................................................................................................5‐106
Appendix5‐A:EntericCH4fromFeedlotCattle–MethaneConversionFactor(Ym)..............5‐109Appendix5‐B:FeedstuffsCompositionTable...........................................................................................5‐113Appendix5‐C:EstimationMethodsforAmmoniaEmissionsfromManureManagementSystems.....................................................................................................................................................................5‐123
5‐C.1 MethodforEstimatingAmmoniaEmissionsUsingEquationsfromIntegratedFarmSystemModel...............................................................................................................................5‐123
5‐C.1.1RationaleforSelectedMethod...............................................................................5‐1235‐C.1.2ActivityData..................................................................................................................5‐1235‐C.1.3AncillaryData...............................................................................................................5‐124
5‐C.2 MethodforAmmoniaEmissionsfromTemporaryStack,Long‐TermStockpile,AnaerobicLagoons/RunoffHoldingPonds/StorageTanks,andAerobicLagoons.....5‐1245‐C.3 MethodforEstimatingAmmoniaEmissionsfromCompostingUsingIPCCTier2Equations....................................................................................................................................................5‐128
5‐C.3.1RationaleforSelectedMethod...............................................................................5‐1285‐C.3.2ActivityData..................................................................................................................5‐1295‐C.3.3AncillaryData...............................................................................................................5‐129
5‐C.4 MethodforAmmoniaEmissionsfromComposting..................................................5‐1295‐C.5 UncertaintyinAmmoniaEmissionsEstimates...........................................................5‐129
Appendix5‐D:ManureManagementSystemsShapeFactors( )...................................................5‐131Appendix5‐E:ModelReview:ReviewofEntericFermentationModels.......................................5‐134Chapter5References..........................................................................................................................................5‐139
SuggestedChapterCitation:Powers,W.,B.Auvermann,A.Cole,C.Gooch,R.Grant,J.Hatfield,P.Hunt,K.Johnson,A.Leytem,W.Liao,J.M.Powell,2014.Chapter5:QuantifyingGreenhouseGasSourcesandSinksinAnimalProductionSystems.InQuantifyingGreenhouseGasFluxesinAgricultureandForestry:MethodsforEntity‐ScaleInventory.TechnicalBulletinNumber1939,OfficeoftheChiefEconomist,U.S.DepartmentofAgriculture,Washington.DC.606pages.July2014.Eve,M.,D.Pape,M.Flugge,R.Steele,D.Man,M.Riley‐Gilbert,andS.Biggar,Eds.
USDAisanequalopportunityproviderandemployer.
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Acronyms,ChemicalFormulae,andUnitsAA AminoacidsAD AnaerobicdigestionADF AciddetergentfiberAGP AntibioticgrowthpromotersASABE AmericanSocietyofAgricultural andBiological EngineersB0 MaximummethaneproductioncapacitiesbLS backwardLagrangianstochasticBNR BiologicalnitrogenremovalBW BodyweightCH4 MethaneCNCPS CornellNetCarbohydrateandProteinSystemCO2‐eq CarbondioxideequivalentsCP CrudeproteinCSTR ContinuousstirredtankreactorDDGS DrieddistillersgrainswithsolublesDE DigestibleenergyDFM DirectfedmicrobialsDGS DistillersgrainswithsolublesDIP DietarycrudeproteinDMI DrymatterintakeDRC Dry‐rolledcornEF Emissionfactorg GramsGg GigagramsGEI GrossenergyintakeGHG GreenhousegasHCW HotcarcassweightHMC High‐moisturecornIFSM IntegratedFarmSystemModelkcal Kilocaloriekg Kilogramslb(s) Pound(s)LCA LifecycleanalysisLU Livestockunitm MetersMCF MethaneconversionfactorME Metabolizableenergymg MilligramMGA MelengestrolacetateMJ MillijoulesNE NetenergyNex NitrogenexcretedN NitrogenN2O NitrousoxideNDF NeutraldetergentfiberNFC Non‐fibercarbohydrateNH3 AmmoniaNPN Non‐proteinnitrogen
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NSP Non‐starchpolysaccharideO2 OxygenOM Organicmatterppb partsperbillionppm partspermillionRDP RuminaldegradableproteinRFI ResidualfeedintakeRMSPE ResidualmeansquarepredictionerrorSF6 SulfurhexafluorideSFC Steam‐flakedcornTAN TotalammoniacalnitrogenTDN TotaldigestiblenutrientsTKN TotalKjeldahlnitrogenTMR TotalmixedrationUASB UpflowanaerobicsludgeblanketUP UnprocessedU.S.EPA U.S.EnvironmentalProtectionAgencyVFA VolatilefattyacidsVS VolatilesolidsWDGS WetdistillersgrainswithsolublesYm Methaneconversionfactor,percentofgrossenergyinfeedconverted
tomethane
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5 QuantifyingGreenhouseGasSourcesandSinksinAnimalProductionSystems
Thischapterprovidesguidanceforreportinggreenhousegas(GHG)emissionsassociatedwithentity‐levelfluxesfromanimalproductionsystems.Inparticular,itfocusesonmethodsforestimatingemissionsfrombeefcattle(cow‐calf,stocker,andfeedlotsystems),dairycattle,sheep,swine,andpoultry(layers,broilers,andturkey).Informationprovidedisbasedonavailabledataatthetimeofwriting.Inmanycasessystemsareoversimplifiedbecauseoflimiteddataavailability.Itisexpectedthatmoredatawillbecomeavailableovertime.Thischapterprovidesinsightintothecurrentstateofthescienceandservesasastartingpointforfutureassessments.
Section5.1summarizesanimalmanagementpracticesandtheresultingGHGemissions. Section5.2presentsanoverviewofeachproductionsystemandageneraldiscussionof
commonmanagementsystemsandpractices.
Section5.3describesthemethodsforestimatingGHGemissionsfromentericfermentationandhousing(entericfermentationbeingamuchmoresignificantemissionssourcethan
housing).
Section5.4describesmethodsforestimatingGHGsfrommanuremanagementsystems. Section5.5identifiesresearchgapsthatexistforquantifyingGHGsfromanimalproduction
systems.Theintentofidentifyingresearchgapsistohighlightwhereimprovementsin
knowledgecanbestimprovetheusefulnessofthisdocumentatfarm‐,regional‐,and
industry‐scales.
5.1 Overview
ThissectionsummarizesthekeypracticesinanimalmanagementandtheresultingGHGemissionsthatarediscussedindetailinthischapter.Theagriculturalpracticesdiscussedincludethoserequiredtobreedandhouselivestock,includingthemanagementofresultantlivestockwaste.Emissionsconsideredhereincludethosefromentericfermentation(resultingfromlivestockdigestiveprocesses),livestockwasteinhousingareas,andlivestockwastemanagedinsystems(suchasstockpiles,lagoons,digesters,solidseparation,andothers).OptionsformanagementchangesthatmayresultinchangesinGHGemissionsarealsodiscussed.
5.1.1 OverviewofManagementPracticesandResultingGHGEmissions
Animalproductionsystemsincludeagriculturalpracticesthatinvolvebreedingandrearinglivestockformeat,eggs,dairy,andotheranimalproductssuchasleather,wool,fur,andindustrial
AmmoniaEmissionsinAnimalProductionSystems
Ammonia(NH3),althoughnotaGHG,isemittedinlargequantitiesfromanimalhousingandmanuremanagementsystemsandisanindirectprecursortonitrousoxide(N2O)emissionsaswellasanenvironmentalconcern.Insidebarnsandhousingunits,NH3isconsideredanindoorairqualityconcernbecauseitcanhaveanegativeimpactonanimalhealthandproduction.Volatilizedammoniacanreactwithothercompoundsintheairtoformparticulatematterwithadiameterof2.5microns.Thisfineparticulatemattercanpenetrateintothelungs,causingrespiratoryandcardiovascularproblems,andcontributetotheformationofhaze.
InformationaboutammoniahasbeenincludedinthischapterandproposedquantificationmethodsarepresentedinAppendix5‐C.
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productslikeglueoroils.Farmersandotherfacilityownersraiseanimalsineitherconfined,semi‐confinement,orunconfinedspaces;thepracticesusedtoraisethemaredependentonanimaltype,region,landavailability,andindividualpreferences(e.g.,conventionalor“organic”standards).Regardlessoftheconditionsinwhichanimalsareraisedandhoused,theyproduceGHGemissions.Themagnitudeofemissionsdependsprimarilyonthequalityofthediet,theanimals’requirementsandintake(e.g.,grazing,pregnant,lactating,performingwork),andthetypesofsystemsinplacetomanagemanure.Theprimarysourceofmethane(CH4)emissionsfromanimalproductionsystemsisentericfermentation,whichisaresultofbacterialfermentationduringdigestionoffeedinruminantanimals.Thesecondlargestsourceofemissionsfromanimalproductionsystemsisfromthemanagementoflivestockmanure.Methaneemissionsalsooccurfromthedigestiveprocessesinmonogastricanimals;however,thequantityissignificantlylessthantheseothertwosources.Forsimplicity,inthereport,thetermentericfermentationreferstoemissionsfromthedigestiveprocessofbothruminantandmonogastricanimals.
Manuremanagementisthecollection,storage,transfer,andtreatmentofanimalurineandfeces.Storageofanimalmanurehasbecomeincreasinglypopularasitallowssynchronizationoflandapplicationofmanurenutrientswithcropneeds,reducestheneedforpurchasedcommercialfertilizer,andreducespotentialforsoilcompactionduetopoortimingofmanureapplication.Dependingonthestorageandtreatmentpractices,manuremanagementhastheaddedbenefitofreducingairandwaterpollution.However,manurestoredinanaerobicconditionsresultsintheproductionandpotentialreleaseofGHGsandodors.Greenhousegasemissionsfromthreesolidmanurestorage/treatmentpractices(temporarystackandlong‐termstockpile,composting,andthermo‐chemicalconversion)andeightliquidmanurestorage/treatmentpractices(aerobiclagoon,anaerobiclagoon/runoffholdingpond/storagetanks,anaerobicdigestion,combinedaerobictreatmentsystem,sand‐manureseparation,nutrientremoval,solid‐liquidseparation,andconstructedwetland)areconsideredinthereport.
Figure5‐1providesanoverviewoftheconnectionsbetweenfeed,animals,manure,andGHGemissionsinananimalproductionsystem.Atthetopoftheconceptualmodel,livestockarefedavarietyofdiets.Ruminantanimalseatfeedstuffsand,throughfermentationbytheruminalmicrobes,CH4isproduced.Poultryandswine,althoughtheydonotreleaseasignificantamountofCH4throughentericfermentation,depositmanureintobedding,anduponmanuredecomposition,mayreleasenitrousoxide(N2O),CH4andammonia(NH3)intotheatmosphere.Methodologytoestimateemissionsfrombeddinganddrymanureinhousingissimilarto,andoftenparallelto,themethoddescribedfordrymanurehandlingandstoragesystems.Manurefromgrazinglivestockisleftonfieldsorpaddocks,andthemanuremaybecollectedtobetreatedandstored.Manurethathasbeencollectedandstoredcanbeappliedtocroplands.GHGemissionsfromgrazinglandsandcroplandsareaddressedinChapter3,QuantifyingGreenhouseGasSourcesandSinksinCroplandandGrazingLandSystems.
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Figure5‐1:ConnectionsBetweenFeed,Animals,Manure,andGHGforAnimalAgriculture
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5.1.1.1 ResultantGHGEmissions
Forthisreport,methodsarecategorizedaccordingtothosefromentericfermentation,housing,andmanuremanagementsystems.Thehousingdiscussionincludesemissionsfrommanuredepositedinthehousingunitandmanurethatismanagedinsidethoseareas(suchasinteriorstockpiles).Manuremanagementincludesemissionsfrommanaged,treated,andstoredmanure.1
EntericFermentationandHousingEmissionsMethane‐producingmicroorganisms,calledmethanogens,existinthegastrointestinaltractofmanyanimals.However,thevolumeofCH4emittedbyruminantsisvastlydifferentfromthatofotheranimalsbecauseofthepresenceandfermentativecapacityoftherumen.Intherumen,CH4formationisadisposalmechanismbywhichexcesshydrogenfromtheanaerobicfermentationofdietarycarbohydratecanbereleased.Controlofhydrogenionsthroughmethanogenesisassistsinmaintenanceofefficientmicrobialfermentationbyreducingthepartialpressureofhydrogentolevelsthatallownormalfunctioningofmicrobialenergytransferenzymes(Morgavietal.,2010).TheonlyGHGofconcernresultingfromentericfermentationisCH4.RespirationchambersequippedwithN2OanalyzersindicatethatentericfermentationdoesnotresultintheproductionofN2O(Reynoldsetal.,2010).Methanecanalsoarisefromhindgutfermentation,butthelevelsassociatedwithhindgutfermentationaremuchlowerthanthoseofforegutfermentation.
Becausethemagnitudeofentericemissionsissogreatand,therefore,asignificantcontributortomanycountries’GHGemissions,decadesofresearchhavegoneintocharacterizing,understanding,andattemptingtomitigateentericCH4emissions.Afundamentalchallengeinthistypeofresearchhasbeenthemeasurementoftheseemissions.
Methane,N2O,carbondioxide(CO2),andNH3areproducedfromlivestockfecesandurine,andsomegaseousformsareemittedsoonaftermanureexcretion.Indry‐lotsituations,fecesandurinearedepositedonthepensurfaceandaremixedviaanimalhoofaction.MicroorganismsinthefecesorunderlyingsoilmetabolizenutrientsinthemanuretoproduceGHGs.Infeedlots,wheremanureisnormallycleanedfrompensonceortwiceperyear,distinctive,hard‐packedlayersofmanureandsoilmaydevelopthatproducemicroenvironmentsfavorabletooxidativeandreductiveprocesses(Woodburyetal.,2001;Coleetal.,2009b).Periodsofrainfallordryconditionsmayalterthemicrobialandchemicalnatureofthepensurface.ProductionofCH4andN2Ooccurintheunderlyingmanure/soillayersandinwater‐saturatedareaswhereoxygenislimited,suchaswetareasofthepenaroundwatertroughsanddepressionsthatcollectrainwaterandsnowmelt.Incontrast,mostNH3producedinthepenprobablycomesfromfreshurinespotsonthepensurface.Todate,fewmeasurementsofGHGemissionsfromfeedlotordry‐lotpensurfaceshavebeenmade.
Runofffromdry‐lotandfeedlotpensisnormallycollectedinretentionponds(moretypicalinfeedlots),orlagoons(morecommonindairies).Insomecases,runoffmayundergopartialremovalofsuspendedsolidsinsettlingbasins(feedlotsanddairies)orinmechanicalseparators(dairiesonly)thatparallelstreatmentofmanurecollectedinthesesamesystems.LossesofGHGsandNH3
1EmissionsfrommanuredepositedongrazinglandsareaddressedinChapter3:CroplandsandGrazingLands.
Background:Ruminants
Ruminantsareanimalsthathavefour‐chamberedstomachs,whichallowforeasierdigestionofhigh‐fiber,hard‐to‐digestfeedstuffs.Theyinclude: Cattle Goats Sheep Deer AmericanBison
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fromthesefacilitiesdependuponclimaticfactorsandtheoxidative‐reductivepotential,pH,andchemistryoftheeffluentinthepondorlagoon.AlimitednumberofstudieshavemeasuredGHGorNH3emissionsfromretentionpondsorlagoons.
ManureManagementManureismanagedinawidevarietyofsystems.TheresultingGHGemissionsdifferbyGHGandmagnitudeofemissionsperquantityofmanure.Table5‐1providesanoverviewoftheliquidandsolidmanuresystemsconsideredinthisreportandtheresultingGHGs.
Table5‐1:OverviewofManureManagementSystemsandAssociatedGreenhouseGases
StorageandTreatmentPractices
EstimationMethod Description
CH4 N2O NH3a
SolidManure
Temporaryandlong‐termstorage
Manuremaybestoredtemporarilyforafewweekstoavoidlandapplicationduringunfavorableweatheroritcanbestoredforseveralmonths.
Composting
Compostinginvolvesthecontrolledaerobicdecompositionoforganicmaterialandcanoccurindifferentforms.Estimationmethodsareprovidedforinvessel,staticpile,intensivewindrow,andpassivewindrowcomposting.
Thermo‐chemicalconversion
Thermo‐chemicalconversioninvolvesthecombustionofanimalwaste,convertingCH4toCO2.Pyrolysis/gasificationisonemethodthathasreceivedmuchinterest.NomethodisprovidedasGHGsareconsiderednegligible.
LiquidManure
Aerobiclagoon Aerobiclagoonsinvolvethebiologicaloxidationofmanureasaliquidwithnaturalorforcedaeration.
Anaerobiclagoon/runoffholdingponds/storagetanks
Anaerobiclagoonsareearthenbasinsthatprovideanenvironmentforanaerobicdigestionandstorageofanimalwaste.Lagoonsmaybecoveredoruncoveredandhaveacrustornocrustformation.Runoffandholdingpondsareconstructedtocaptureandstorerunofffromfeedlotsanddry‐lots.Insomecaseswashwaterfromdairyparlorsmaybestoredinholdingponds.Storagetankstypicallystoreslurryorwastewaterthatwasscrapedorpumpedfromhousingsystems.
Combinedaerobictreatmentsystem
Thisprocessinvolvesremovingsolidsusingflocculationandthencompostingthesolidstreamandaeratingtheliquidstreamofmanure.
Anaerobicdigester
Anaerobicdigestersaremanuretreatmentsystemsdesignedtomaximizeconversionoforganicwastesintobiogas.Thesecanrangefromcoveredanaerobiclagoonstohighlyengineeredsystems.MethanegasleakageisthemainsourceofGHGemissions;NH3andN2Oleakageisnegligible.
Sand–manureseparation
Manureisseparatedfromsandandbeddingbymechanicalandsedimentationseparation.Nomethodisprovidedasemissionsarenegligible.Separatedliquidsandsolidscouldbeinputsintootherstoragesystems.
Nutrientremoval
Therearefourmainnitrogenremovalapproaches:biologicalnitrogenremoval,Anammox(i.e.,anaerobicammoniumoxidation),NH3stripping,ionexchange,andstruvitecrystallization.NomethodisprovidedduetolimitedquantitativeinformationonGHGgenerationfromnutrientremovalsystems.
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StorageandTreatmentPractices
EstimationMethod Description
CH4 N2O NH3a
Solid–liquidseparation
Mechanicalseparationofliquidsandsolidsthroughscreens,centrifuges,pressing,filtration,ormicroscreening.Separatedliquidsandsolidscouldbeinputsintootherstoragesystems.
Constructedwetland
Typicallyconsistofwetlandplantsgrowinginabedofhighlyporousmedia.Nomethodisprovidedasemissionsarenegligible;GHGsinksarenotedtolikelybegreaterthanemissions.
aAlthoughNH3isconsideredinthischapterasanimportantprecursortoparticulateformulation(affectingradiationbalance)andGHGsandisakeyelementofdiscussion,NH3itselfisnotaGHG.Therefore,methodsforestimatingNH3emissionsareprovidedinAppendix5‐C.
AnentitycanreduceitsGHGemissionsfrommanurebyutilizingalternativetreatmentoptionsand/ormanagementsystems.AnaerobicdigestersdonotreducetheamountofCH4releasedbutofferanoptiontocaptureandconverttheCH4toCO2andenergythroughcombustion.DigestersofferbothCH4reductionsaswellasGHGavoidancebyreducinganentity’selectricitydemand.
5.1.1.2 ManagementInteractions
Table5‐2depictsthekeytypesofinformationdesiredforestimatingGHGemissionsfromananimalproductionfacility.Thistableillustratestheattributesofasystemthathavethegreatestinfluenceoveremissionswithineachcomponent.AnumberofexistingmodelscanbeusedtoestimateGHGemissionsthatutilizethekeyactivitydataindicatedinTable5‐2.
Table5‐2:DesiredActivityandAncillaryDataforEstimatingGHGEmissionsfromAnimalProductionSystems
GeneralCategory SpecificData
CattleSheep Swine Poultry Goats
Amer.BisonCow–
calfStockers Feedlot Dairy
Animal
Characteristics Bodyweight ● ● ● ● ● ● ● ● ●
Bodyconditionscore ● ● ● ●
Stageofproduction(dry,lactating,pregnant)
● ● ●
Dieta
ry
Facto Dietintake(orfactorsthatcanbeusedtopredictintake)
● ● ● ● ● ● ● ● ●
CombinedAerobicTreatmentComparedtoAnaerobicLagoons
Acombinedaerobictreatmentsysteminvolvesthetreatmentofamanurestreamwithflocculantstoremovethemajorityofsolidsfromthestream.Thesolidsportioniscompostedwhiletheremainingliquidistransferredtoastoragetankwhereitisaerated.MethaneisavoidedbyaerobicallytreatingthesolidsviacompostingwhileNH3inthewastewaterisavoidedvianitrification.TheGHGsresultingfromacombinedaerobictreatmentareonly10percentofwhatwouldbeemittedfromananaerobiclagoon,thuscombinedaerobictreatmentsrepresentapotentialmitigationoptionforentities.
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GeneralCategory SpecificData
CattleSheep Swine Poultry Goats
Amer.BisonCow–
calfStockers Feedlot Dairy
Typeofforage(conservedorgrazed,pasturecomposition,stageofplantgrowth)
● ● ● ● ● ●
Dietdrymatterintake,crudeprotein,neutraldetergentfiber,aciddetergentfiber,non‐structuralcarbohydrates,fiber,fat,energycontent
● ● ● ● ● ● ● ● ●
Dietdigestibilityand/orrateofpassage
● ● ● ● ● ●
Degradabilityofcarbohydratesandproteins
● ● ●
Supplementationpractices– type(e.g.,grains,protein,liquid,dryblocks,non‐proteinnitrogen)andquantity
● ● ● ● ●
Supplementalordietionophoreconcentration
● ● ● ●
Dietarybeta‐agonists ● ●
Nutrient
Excretion:
Quantity
Carbon,nitrogen,andvolatilesolids
● ● ● ● ● ● ● ● ●
Other
Animal
Factors
Growthpromotingimplants
● ●
ManureManagem
entFactors
Animalmanagementregimenusedtospreadmanureoverpasturetoreduceconcentrationnearwaterorfeedsources
● ● ● ● ● ●
Soiltype ● ● ● ● ● ● ● ● ● Practicestocontrolrunofffrompastures/lots/fields
● ● ● ● ● ● ● ● ●
Ifhoused,thelengthoftimetheyarehoused,animalconcentration,manurehandlingprocedures
● ● ● ● ● ● ● ● ●
Typeofmanurecollection/storagesystem
● ● ● ● ●
Frequencyofmanurecollectionsandcomposition
● ● ● ● ●
Bedding/litteruseandsource
● ● ● ● ●
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5.1.2 SystemBoundariesandTemporalScale
Systemboundariesaredefinedbythecoverage,extent,andresolutionoftheestimationmethods.ThemethodsinthisreportcanbeusedtoestimateGHGemissionsourcesthatoccurwithintheproductionareaofananimalproductionsystem,includingtheanimals,animalhousing,andmanurehandling,treatment,andstorage.Methaneemissionsfromentericfermentation,aswellastheCH4andN2Oemissionsfrommanuremanagementsystemsormanurestoredinhousing,areconsideredinthisreport.Ammonia,whilenotaGHG,isaprecursortoN2Oformationandis,therefore,included,primarilyinAppendix5‐C.Theactoftransportingmanuretothefieldforlandapplicationisincludedintheproductionareaboundary,butemissionsfromvehicletransportarenotincludedinthescopeofthisreportastherearemanyvariablesthatwoulddetermineemissionsfromvehicles(ageofvehicle,type,fuelefficiency,idletime),andtheyarenotdirectagriculturalemissionsandcouldinsteadbeconsideredpartofthetransportsector(off‐road).Additionally,thisreportdoesnotencompassafulllifecycleanalysis(LCA)ofGHGemissionsfromanimalproductionsystems.TheadjacenttextboxsummarizesseveralstudiesonLCAsforanimalproductionsystems;however,theyarenotutilizedinthisreport.EmissionsthatresultfollowingmanureapplicationareaddressedseparatelyinChapter3,QuantifyingGreenhouseGasSourcesandSinksinCroplandandGrazingLandSystems.
Foremissionsfromanimalproductionsystems,themethodsprovidedhavearesolutionofindividualherdswithinanentity’soperation.Aherdisdefinedasagroupofanimalsthatarethesamespecies,grazeonthesameparcelofland(samedietcomposition),andutilizethesamemanuremanagementsystems.Emissionsareestimatedforeachindividualherdwithinanoperationandthenaddedtogethertoestimatethetotalanimalproductionemissionsforanentity.Theanimalproductiontotalsarethencombinedwithemissionsfromcroplands,grazinglands,andforestrytodeterminetheoverallemissionsfromtheoperationbasedonthemethodsprovidedinthisdocument.Emissionsareestimatedonanannualbasis.
5.1.3 SummaryofSelectedMethods/Models/SourcesofData
TheIntergovernmentalPanelonClimateChange(IPCC,2006)hasdevelopedasystemofmethodologicaltiersrelatedtothecomplexityofdifferentapproachesforestimatingGHGemissions.Tier1representsthesimplestmethods,usingdefaultequationsandemissionfactorsprovidedintheIPCCguidance.Tier2usesdefaultmethods,butemissionfactorsthatarespecifictodifferentregions.Tier3usescountry‐specificestimationmethods,suchasaprocess‐basedmodel.ThemethodsprovidedinthisreportrangefromthesimpleTier1approachestothemostcomplexTier3approaches.Higher‐tiermethodsareexpectedtoreduceuncertaintiesintheemissionestimates,ifsufficientactivitydataandtestingareavailable.
EstimatingCH4emissionsfromentericfermentationinswine,goats,Americanbison,llamas,alpacas,andmanagedwildlifeuseTier1methods.EntericemissionsfromsheepareestimatedusingtheHowdenequation(Howdenetal.,1994),andemissionsfromdairyproductionsystemsareestimatedusingtheMitscherlich3(Mits3)equation(Millsetal.,2003)asprovidedintheDairyGasEmissionsModel(DairyGEM)(Rotzetal.,2011a).EmissionsfrombeefcowsareestimatedusingtheIPCCTier2approach.EmissionsfromfeedlotsareestimatedusingamodificationoftheIPCCTier2approach.
QualitativeDiscussiononManureSources
Estimationmethodsarenotavailableforsomesources.Qualitativediscussionisprovidedfor:
Sand‐ManureSeparation NutrientRemoval Solid‐LiquidSeparation ConstructedWetlands Thermo‐chemicalConversion
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
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Formanuremanagement,theIPCCTier2methodologyisusedforCH4emissionsfromtemporarystackandlong‐termstockpile,CH4andN2Oemissionsfromcomposting,andN2Oemissionsfromaerobiclagoons.TheSommermodelisusedtoestimateCH4emissionsfromanaerobiclagoons.
Allmethodsincludearangeofdatasourcesfromoperation‐specificdatatonationaldatasets.Operation‐specificdatawillneedtobecollectedbytheentityandgenerallyareactivitydatarelatedtothefarmandlivestockmanagementpractices(e.g.,dietaryinformation,volatilesolidscontentofmanure).Nationaldatasetsarerecommendedforancillarydatarequirements,suchasclimatedataandsoilcharacteristics.
AsummaryofproposedmethodsandmodelsforestimatingGHGemissionsfromanimalproductionsystemsisprovidedinTable5‐3.
Life Cycle Analysis of Cattle Production Systems
Petersetal.(2010)reportedthattheestimatedcarbonfootprintofcattleproductionsystemsaroundtheworldrangedfrom8.4kgofCO2‐eq(kgHCW)‐1(HCW=hotcarcassweight)inanAfricanpastoralsystemto25.5kgCO2‐eq(kgHCW)‐1inanintensiveJapanesegrainfeedingsystem.FiveNorthAmericanstudies(Vergeetal.(2008)andBeaucheminetal.(Sweeten,2004;2010)inCanada,Pelletieretal.(2010)andLupoetal.(2013)intheU.S.Midwest,andStackhouseetal.(2012)andStackhouse‐Lawsonetal.(2012)inCalifornia)estimatedthecarbonfootprintofvariousbeefcattleproductionsystems:Thecarbonfootprintforthetotalbeefproductionsystemsrangedfrom10.4to19.2kgCO2‐eq(kgfinalbodyweight)‐1(or16.7to32.5kgCO2‐eq(kgHCW)‐1).Sixtyfourto80percentofthetotalCO2‐eqwasproducedinthecow‐calfsectorofproduction;whereas8to20percentofCO2‐eqwasproducedinthestockerphase,andonly12to16percentwasproducedduringthefinishingphase.Themajority(55to63percent)ofthetotalCO2‐eqwasentericCH4,18to23percentwasmanureN2O,and14to24percentwasfromfossilenergyuseandsecondaryemissions.
Ingeneral,thedailycarbonfootprintwasgreaterduringthegrazing(stocker)phasethanduringthefeedlotfinishingphase.BothPelletieretal.(2010)andStackhouseetal.(2012)reportedthatthecarbonfootprintwasslightlylowerforcalvesthatwereweanedandwentdirectlytothefeedlot(21.1and23.0kgCO2‐eq(kgHCW)‐1or2,382and3,493kghead‐1,respectively)thanforcattlethatwentthroughastockergrazingphasebeforeenteringthefeedlot(22.6and26.1kgCO2‐eq(kgHCW)‐1or2,904and4,522kgCO2‐eqhead‐1,respectively).Pelletieretal.(2010)andLupoetal.(2013)bothreportedthatthecarbonfootprintofgrass‐finishedcattlewasgreaterthanforcalvesthatwereweanedandwentdirectlytothefeedlot.Thesedifferencesaredueinparttoslowerweightgainandlighterfinalbodyweightsandcarcassweightsofgrass‐fedcattlethancattlefinishedongrain‐andbyproduct‐baseddietsinthefeedlot.
MostLCAsassumethatcarbonsequestrationisminimalinestablished,unfertilizedpastures.Phetteplaceetal.(2001)andLiebigetal.(2010)suggestedtheremaybesomesmallnetcarbonsequestration,inestablishednativepastures.However,Liebigetal.(2010)notedthatfertilized,improvedpastureshadnetCO2‐eqemissions;primarilybecauseofincreasedlossesofN2Ofromfertilizernitrogen.Lupoetal.(2013)notedthattheassumedcarbonsequestrationofpastures(equilibriumvs.netsequestration)affectedthecarbonfootprintofgrass‐finishedcattle;however,regardlessofthecarbonsequestrationassumption,grass‐finishedcattlehadagreatercarbonfootprintthangrain‐finishedcattle.
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Table5‐3:SummaryofSourcesandProposedGHGEstimationMethodsforAnimalProductionSystems
Section Source Method
AnimalProductionSystems,IncludingEntericFermentationandHousingEmissions5.3.1.2 DairyCattle Mits3equation; ASABEStandardD384.2andIPCCTier2(housing)5.3.2.2 BeefCattle ModifiedIPCCTier2 (entericandhousing);ASABEStandardD384.2
(housing)5.3.3.2 Sheep Howdenequationforgrazingsheep(Howden etal.,1994)andBlaxterand
Clapperton(1965)forfeedlotsheep5.3.4.2 Swine IPCCTier1 (entericmethane);ASABEStandardD384.2andIPCCTier2
(housing)5.3.5.2 Poultry IPCCTier1;ASABEStandardD384.2andIPCCTier2(housing)5.3.6.1 Goats IPCCTier15.3.6.2 AmericanBison,
Llamas,Alpacas,andManagedWildlife
IPCCTier1
ManureStorageandTreatmentTemporaryStack&Long‐TermStockpile5.4.1.2 Methane IPCCTier2usingU.S.EPAInventoryemissionfactors(EFs)anddiet
characterization5.4.1.4 NitrousOxide IPCCTier2usingU.S.‐basedEFsandmonthlydataComposting5.4.2.2 Methane IPCCTier2withmonthlydata5.4.2.4 NitrousOxide IPCCTier2AerobicLagoon5.4.3.2 Methane MethaneConversionFactor foraerobictreatmentisnegligibleandwas
designatedas0%inaccordancewithIPCC5.4.3.4 NitrousOxide IPCCTier2usingIPCCEFsAnaerobicLagoon,RunoffHoldingPond,StorageTanks5.4.4.2 Methane Sommermodelbasedon fractionsofvolatilesolids(Mølleretal.,2004)5.4.4.4 NitrousOxide FunctionoftheexposedsurfaceareaandU.S.‐basedemissionfactorsAnaerobicDigestion5.4.5.2 Methane IPCCTier2usingCleanDevelopmentMechanismEFsfordigestertypesto
estimateCH4leakagefromdigestersCombinedAerobicTreatmentSystems5.4.6.25.4.6.2
MethaneNitrousOxide
10%ofemissionsfromestimationofliquidmanurestorageandtreatment–anaerobiclagoon,runoffholdingpond,storagetanks
OtherTreatmentMethods5.4.7 Sand–Manure
SeparationNomethodprovidedbecause GHGemissionsarenegligible
5.4.8 NutrientRemoval Notestimatedduetolimitedquantitativeinformation5.4.9 SolidLiquid
SeparationNomethodprovidedbecause GHGemissionsarenegligible
5.4.10 ConstructedWetland Nomethodprovidedbecauseemissionsarenegligible;GHGsinksarenotedtolikelybegreaterthanemissions
5.4.11 Thermo‐chemicalConversion
NomethodprovidedasGHGemissionsarenegligible
5.1.4 OrganizationofChapter/Roadmap
Theremainderofthischapterisorganizedintofourprimarysections,asillustratedinFigure5‐2.Section5.2providesoverviewsofdairycattle,beefcattle,sheep,swine,andpoultryproduction
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systemsandprovidesinformationondietandhousing.Section5.3providesthemethodsforestimatingGHGsfromhousing,primarilyfocusingonGHGsfromentericfermentation.MethodsarealsoprovidedforallthespeciesdescribedinSection5.2,plusadditionalanimaltypes(i.e.,goats,Americanbison,llamas,alpacas,andmanagedwildlife).Section5.4providesthemethodologyforestimatingemissionsfromdifferentmanuremanagementsystems.MethodologyisprovidedtoestimateCH4andN2Ofromtemporarystackandlong‐termstockpiles,composting,aerobiclagoons,anaerobiclagoons,andcombinedaerobictreatmentsystems.Section5.4alsoprovidesmethodsforestimatingCH4fromanaerobicdigestion.Aqualitativediscussionisprovidedforsand‐manureseparation,nutrientremoval,solid‐liquidseparation,constructedwetlands,orthermo‐chemicalconversion.Section5.5presentsresearchgapsforbothentericfermentationandmanuremanagement.
Therearefiveappendicestotheanimalproductionsystemschapterofthisreport.Appendix5‐AprovidesYmadjustmentfactorsforcalculatingentericCH4fromfeedlotcattle.Appendix5‐Bprovidesnutritionalinformationaboutanimalfeedstuffs(Ewan,1989;Preston,2013).Appendix5‐CdiscussesavailablemethodologiesforestimatingNH3emissionsfromanimalproductionsystems.Appendix5‐DdescribestheshapefactorsandrelatedequationsthatcanbeappliedinAppendix5‐Ctomoreaccuratelyestimateemissionsfrommanurestockpilesthatareshapeddifferently(assurfaceareapartiallydeterminesemissions).Appendix5‐Eprovidesadetailedreviewofmodelsevaluatedforsuitabilityforestimatingemissionsfromanimalproductionsystems.
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Figure5‐2:AnimalProductionSystemsRoadMap
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5.2 AnimalProductionSystems
Thissectionprovidesdiscussionontheproductionsystemsforbeefanddairycattle,sheep,swine,andpoultry.ThisprovidesthebackgroundnecessaryforunderstandingSection5.3,whichcoversGHGemissionsfromanimalproductionsystems.
5.2.1 DairyProductionSystems
5.2.1.1 OverviewofDairyProductionSystems
TheU.S.dairyproductionsystemiscomprisedofseveralkeyprocessesfordairycattle,theirmanure,andtheirendproducts(meat,dairy)asdepictedinFigure5‐3.Thisconceptualmodelprovidesanoverviewofthetypicaldairysystem,followingcattlefrombirthtoslaughterandfollowingmanurefromtheanimalthroughamanagementsystem.Manureisproducedduringeachstage,anddependingonthelocation,ismanageddifferently.ThemanagementoftheresultantmanurehasimplicationsonthequantityofGHGemissionsandsinks;thekeypracticesarediscussedindetailbelow.Theestimationmethodsinthischapterincludediscussionsforemissionsfromentericfermentation,housing,andmanuremanagementandarenotafullLCA.
TheU.S.dairyindustryiscomposedprimarilyoffourmajorsegmentsofproduction:1)calfrearing;2)replacementheifers;3)lactatingcows;and4)nonlactating(dry)cows.TheU.S.dairycattlepopulationin2012consistedofapproximately9.2millionmilkcowsandfirstcalfheifersandapproximately4.6millionreplacementheifers.ThemajorityofdairycattleintheUnitedStatesareHolstein(Holstein‐Friesian),followedbyJersey,withsmallernumbersofGuernsey,BrownSwiss,andAyrshire.Overthelast65yearstherehavebeendramaticincreasesinmilkproductionperanimal,duetochangesinherdmanagement,nutrition,composition,andbreedingprograms.Present‐daydairyherdsaredominatedbyHolsteincows(90percent)asopposedtoamixofthefivemostcommonbreeds(Jersey,Guernsey,Ayrshire,BrownSwiss,andHolstein)aswascommoninthe1940s.Withachangeinbreeddominanceandenhancedgenetics,thetypicalmilkproductionpercowhasincreasedfrom2,074to9,193kgofmilkperyear(Capperetal.,2009).
5.2.1.2 DietsforDairyCattle
Cowsinintensivedairyproductionsystemsarefeddietsthatreflectregionallyavailablefeedsandtypicallycontainbetween40and60percentconcentrates,suchasfeedgrains,proteinsupplements,andbyproductssuchasdistiller’sgrains.Typicaldietsincludecornsilage,alfalfaorgrasssilage,alfalfahay,groundorhigh‐moistureshelledcorn,soybeanmeal,fuzzywholecottonseed,andoftenbyproductfeeds(e.g.,corngluten,distiller’sgrains,soybeanhulls,citruspulp,beetpulp).Byproductfeedsmaymakeupalargeportionofthedietcomposition,providingkeynutrientsandameansofdisposalforotherwiselandfilledingredients.Proximitytocropprocessingplantsandindustriesmaydictatetheavailabilityofbyproductfeedsbyregion.
GrowingHeifersDietsforgrowingheifersareformulatedbasedongrowthrateandstageofrumendevelopment.Dietsrangefromliquiddiets(e.g.,milkormilkreplacer)innewborncalvestopelletedcompletefeedsinthegrowingcalf(e.g.,calfstarter)todietsthataresimilartothatofferedtolactatingcowsasthecowsgrowandrumensdevelop.Roughagecontentofthedietincreasesastherumendevelopswithhayorsilageoftenofferedinconjunctionwithacalfstarterduringatransitionperiod.Followingthattransition,typicalfeedsincludethoselistedabove.FeedsareoftenmixedtogetherinamixerandfedasaTotalMixedRation(TMR).Insomecases,feednotconsumedbythelactatingherdisfedtogrowingheiferswhentherumenisfullydeveloped(>9monthsofage).
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Figure5‐3ConceptualModelofDairySystemsintheUnitedStates
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LactatingCowsDietsforlactatingcowsareformulatedbytargetmilkproductionorstageoflactation,whichreflectsthedifferencesinenergyandproteinrequiredfordifferentamountsofmilkproduced.Peaklactationoccursabout60daysaftercalving,andproductionslowlydeclinesoverthenextseveralmonths.FeedstuffsarecommonlyblendedtogetherinamixerandfedasaTMR.
DryCowsDrycowdietsareoftenformulatedintotwostages:far‐offdryandclose‐updry.Duringthefar‐offdryperiod,cowsarefeddietswithhighforagecontent(>60%)usingingredientssimilartothatfedtothelactatingherd.Asdrycowsapproachcalving,energycontentofthedietincreasesbydecreasingforagetoincludemoreconcentratefeedsandmineralformulationchangesinordertoavoidpre‐andpost‐partummetabolicdisordersthatoftencenteraroundcalciummobilizationasthecowbeginstolactate.FeedstuffsarecommonlyblendedtogetherinamixerandfedasaTMR
5.2.1.3 DairyHousingandManureHandling
TwogeneraldairyfarmtypescanbedistinguishedintheUnitedStates:confinementfeedingsystems(includingbarnsanddry‐lots)andpasture‐basedsystems(USDA,2004a).Typicalhousingsystemsforconfinementfeedingoperationsincludetiestallbarns,freestallbarns,freestallbarnswithdrylotaccess,anddrylots.Drylotsystemsconsistofhousinganimalsinpenssimilartobeefcattlefeedlots,butatalowerstockingdensity.Inpasture‐basedsystems,cattlegrazepastureforperiodsoftime,basedonfeedavailabilityandenvironmentalconditions,andarehousedinbarnsandfedstoredfeedwhenpastureisnotavailable.Thedairycattlelifecycleproductionphaseisgenerallydividedintothreesegments:growinganimals(calvesandreplacementheifers),lactatingmaturecows,anddrymaturecows.Nutrientneeds,andthereforediets,andintakeareverydifferentbetweenthedifferentlifecyclephases:growingcattle(calvesandheifers),lactatingcows,anddrycows.Housingandmanuremanagementsystemsvaryconsiderablythroughoutthecountryandcandifferinaregionandbythesizeoftheherd.Incaseswherehousingandmanuremanagementvariesbyanimalgroup(e.g.,heifers,dry,andlactatingcows),estimatesofGHGemissionsfromonegrouparenotapplicabletoothergroups.Whenhousingandmanuremanagementaresimilarbetweengroups(e.g.,allcattleondry‐lots),dietandintakeadjustmentfactorscanbeusedtocompareGHGemissionsforthedifferentgroups.
Withtheexceptionofcalves,replacementheifersanddrycowsmaybehousedandmanagedinsimilarwaysaslactatingcows.Whenthisisthecase,muchofthediscussionisrelevanttothethreegroups.Incaseswherethelactatingherdismanagedinconfinementbutreplacementanddryanimalsaremanagedonpastureorindry‐lots,emissionsfromlactatingcattlearenotapplicablenotonlyduetodifferencesindietandintakebutalsoduetohousingdifferences.Therearenoreadilyavailablestudiesthathavefocusedstrictlyonemissionsfromdairycalfmanagementandhousing.Summarizedbelowarekeycharacteristicsofdifferenceinhousingbylifecyclephaseofadairycow.
Growing(calvesandreplacementheifers).Followingbirth,calvesareusuallyremovedfromthecowwithinafewhoursandaretypicallyrearedonmilkormilkreplacerincalfhutchesorbarnsforthreetosevenweeksuntilweaning.Femalecalves(replacementheifers)aretypicallymovedtogrouphousing(e.g.,superhutches,transitionbarns,openhousing,orpasture)untiltheyreachappropriatebreedingweightatabout14to15monthsofage.Somereplacementsarecontract‐rearedbyheifergrowersorsold.Followingbreeding,heifersareoftenraisedinlots,pasture,orbarnsuntiltheyarereadytocalve.Manureingrouphousingmaybehandledasasolid(beddedpackorcompostbarn)orasaslurry,similartothatdescribedbelowforlactatingcowsinfreestallbarns.
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LactatingCows.Heiferstypicallyhavetheirfirstcalfatabout23to24monthsofage,afterwhichtheyjointheproductionherd.Acowtypicallyremainsintheherduntilaboutfiveyearsofage,althoughmanycowsarecapableofremainingproductiveintheherdfor12to15years.Eachperiodofproductionorlactationlastsfor11to14monthsorlongerandspansthetimeperiodfromcalvingtodry‐off,whichiswhenmilkingisterminatedabout40to60daysbeforethenextanticipatedcalving.Thus,cowsarebredwhiletheyareproducingmilk,usuallybeginningatabout60daysaftercalving,tomaintainayearlycalvingschedule.Followingthe35to60‐daydryperiod,thecowcalvesagain,andthelactationcyclebeginsanew.Cowsaverageabout2.8lactations,althoughmanyremainproductiveconsiderablylonger(Hareetal.,2006).
Lactatingcowsmaybehousedintiestall(stanchion)barns,whichlimitthecows’mobilitybecausethecowsaretethered,fed,andmilkedinthestalls.Agutterisusedtoremovethemanurebyabarncleaner,whichtypicallyplacesthemanuredirectlyintoamanurespreaderorinatemporarystoragepile.Freestallbarnsallowthecowstomovefreelyinandoutofstalls,andthecowsaremovedtoaseparatearea(milkingcenterorparlor)formilking.Manuretypicallyaccumulatesinalleywaysandisremovedviascraping,vacuuming,orflushingwitheithercleanorrecirculatedwater.Somefreestallbarnshaveslottedfloorswithlong‐termmanurestoragebelowthefloors.Manureisgenerallyworkednaturallythroughtheslotsbythecows’feetandwithassistanceviamechanicalscrapingequipment.Dairyfacilitiesmayalsousepasturesanddry‐lotstohouselactatingcows.Lotsarescrapedperiodically,asarepasturesoccasionally,andthesolidmanureiscollected.Althoughnotprevalent,somedairyfacilitiesmayhouselactatingcowsinbeddedpackorcompostbarns,againhandlingmanureasasolidmaterial.
DryCows.Muchlikegrowingcows,housingoptionsfordrycowsarethesameasdescribedaboveforlactatingcows.Thekeydeterminantismanagementpreferenceforthefarmownerand/orfacilityavailability.
Manureandsoiledbeddingfrombarnscanbehandledinanumberofways.Manurecanberemovedfromthebarnsmechanicallyanddirectlyloadedintomanurespreaders,althoughthisisnotcommononmediumandlargefarms.Manurecanalsobeprocessedinananaerobicdigesterwherebacteriacanbreakdownmanuretoproducebiogasthatcanbeflaredorcapturedforenergypurposespriortostorageofdigestereffluent.Whenmanurehasalowersolidscontent,itmaybestoredinatankorpitasaslurry,ortransportedtoasolid‐liquidseparationsystemwiththeliquidfractionconveyed(pumpedorbygravity)toalong‐termstoragepond,whilethesolidscanbedewaterednaturallyandreusedasbedding,composted,land‐applied,and/orsold.Indry‐lotsystems,themanureinthepensistypicallystackedandfollowingstorageiseitherland‐appliedorcomposted.Lotrunoffandmilkingparlorwashwaterispumpedtoastoragepond.Therearesomedry‐lotdairiesthatuseaflushsystemtocleanmanurefromalleywaysbehindthefeedbunks;thiswashwateriseventuallystoredinawastewaterpond.Openfreestalldairieshaveacombinationofbarnswithexerciseyardsbetweenthebarns,andthereforemanureishandledsimilarlyasinatraditionalfreestallbarnanddry‐lotproductionsystem.Wastewaterfrommilkingcenters(manure,clean‐in‐placewater,andfloorwashdownwater)istypicallycombinedwithbarnmanuredestinedforlong‐termstorage,andmaygothroughasolid‐liquidseparationprocessfirst.Inpasture‐basedsystems,manureisdepositeddirectlyontothepastureandthereforenotintensivelymanaged,butmayaccumulateinareaswhereanimalstendtocongregate(e.g.,wateringareas,shade).
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5.2.2 BeefProductionSystems
5.2.2.1 OverviewofBeefProductionSystems
TheU.S.beefproductionsystemiscomprisedofseveralkeycomponentsforbeefcattle,theirwaste,andtheirendproducts,asdepictedinFigure5‐4.Thisconceptualmodelprovidesanoverviewofthetypicalbeefprocessingsystems,followingthesegmentsofthebeefcattleindustry(i.e.,cow‐calf,stocker,feeder/finisher,andpacker)frombirthtoslaughterandfollowingwastefromtheanimalthroughamanagementsystem.Wasteisproducedduringeachstageofactivityoccurringinthesystem,anddependingonthelocation,ismanageddifferently.
Ofthe90millionbeefcattleintheUnitedStates,approximately50millionarematurecowsandtheircalvesoncow‐calfoperations(USDANASS,2012),whichrangeinsizefromafewcowstoseveralthousandcows.Theseoperationsarenormallybasedonforages,eitherimprovedpasturesornativerange,andvaryinsizefromafewacrestohundredsofsections.Typically,whencalvesare150to220daysofagetheyareweanedandmovedtopastureforperiodsof60to200days(thestockerphase),althoughsomemaymovedirectlytoafeedlot.Thepasturesmaybenativerange,improvedperennialpastures,orannualssuchaswheatpasture,forage‐sorghums,andcropresiduessuchascornstalks.Afterthestockerphase,calvesnormallymovetofeedlotswheretheyarefedgrain‐andbyproduct‐baseddietsfor110to160days,untiltheyarereadyforharvest.Inaddition,steersandcullheifersfromdairyoperationsarealsofed.Approximately23millioncattlearefedinfeedlotsannuallyintheUnitedStates.Feedlotsrangeinsizefromafewhundredheadtomorethan100,000headcapacity.
5.2.2.2 DietInformationforBeefCattle
Cow‐CalfandBullsGrazingpasturesmaybenativerange,improvedperennialpastures,orannualssuchaswheatpasture,forage‐sorghums,andcropresiduessuchascornstalks.Beefcowsandbullsaretypicallyfedsupplementalfeedsduringtimeswhenpastureorrangeforagedoesnotmeettheirnutritionalrequirements,usuallyinwinter.Arecentsurveyofthebeefcow‐calfindustryfoundthat74percentofoperationsfedaproteinsupplementand51percentfedanenergysupplement(USDA,2010).Overallproteinwassupplementedforanaverageof173days(SE=9.6)andenergyfor162days(SE=12.7),butthiswashighlyvariableacrossregionsofthecountry.Ninety‐sevenpercentofoperationsinthesurveysupplementedthecowherdwithroughageforanaverageof154days(SE=7.0).Theproteinsupplementswerereportedasplantproteinorurea‐based.Cornwasreportedastheprimaryenergysupplement.Theamountofsupplementfedperheadperdaywasnotincludedinthereport.
StockersStockersgrazeforage,includingwheatpasture,improvedpastures,range,andcropresidues.Stockercattlemayalsoreceivesupplementalproteinorenergyfeedstoincreaseperformanceand/orextendpastureforage.Supplementsmayormaynotcontainanionophore.Somestockercalvesmaybeimplantedwithagrowthpromotingimplant;othersarenot.
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Figure5‐4ConceptualModelofBeefProductionSystemsintheUnitedStates
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FeedlotCattletypicallyenterfeedyardsbetweentheagesof100and350daysweighing200to350kg,andgotoslaughterweighingbetween500to700kg.Theyarefedhigh‐concentrateorhigh‐byproductdietsfor100to200days.Ofthecattlefed,approximately55percentarebeefsteers,25to30percentarebeefheifers,and12to20percentaredairysteersandheifers.ThevastmajorityofcattlefedarebeefbreedsofBritishorContinentalbreeding.However,manycattlewithBrahmangeneticsarealsofed,mostlyinthesouthernplains.Inareaswithasignificantdairyindustry,steersandheifersofdairybreeding(mostlyHolstein)arealsofed.
Typicalfeedlotdietscontainhighconcentrationsofgrain(75percentormore)and/orbyproductssuchasdistillersgrainsandglutenfeed.Theyarenormallybalancedforprotein,energy,vitamins,andminerals(VasconcelosandGalyean,2007).Becausemanybyproductscontainhighconcentrationsofproteinandmineralssuchasphosphorusandsulfur,whenthesebyproductsarefed,dietaryconcentrationsofproteinandsomemineralsmayexceedanimalrequirements.FeedingofionophoressuchasmonensiniscommonintheUnitedStates,asistheuseofgrowth‐promotingimplants.Thedietsfedinfeedyardstendtodifferbetweenthenorthernandsouthernplains.Finishingdietsbasedondry‐rolledcorn(DRC)andhigh‐moisturecorn(HMC)dominateintheNorth,whereasdietsbasedonsteam‐flakedcorn(SFC)dominateintheSouth.Theuseofbioethanolco‐productssuchasdistiller’sgrainsandcorn‐millingco‐productssuchascornglutenfeedinfinishingdietsisgreaterinthenorthernplainsbecauseofthegreateravailabilityoftheseco‐products,buttheiruseisincreasinginthesouthernplains.
5.2.2.3 BeefCattleHousingandManureHandling
Cow‐CalfandBullsCowherdsandreplacementheifersaremostoftenhousedonpasture.Fecesandurinearedepositedonpasturesandrangelandandmaybeconcentratedinareasinwhichfeedingorwateringtakesplace.
StockersStockersareusuallyhousedonpastureandthusnomanurehandlingisusedandGHGemissionsareapartofthecroplandssection(seeChapter3,QuantifyingGreenhouseGasSourcesandSinksinCroplandandGrazingLandSystems).Calvestobeusedasstockerscanbehousedforshortperiodsoftimeindry‐lots.
FeedlotHousingandmanuremanagementatmostbeefcattlefeedingoperationsdiffergreatlyfromthoseusedinotherlivestockspecies,withthevastmajoritybeingfinishedindry‐lotpenswithsoilsurfaces.Manureisnormallydepositedonthepensurfaceandscrapedfromthepensaftereachgroupofcattlegoestomarket.Partofthemanuremaybestackedinthepentoprovidemoundsthatimprovependrainageandassurethatcattlehaveadryplacetolieafterrains.Manureremovedfromthepenmaybeimmediatelyappliedtofieldsnearthefeedlot,stockpiledforlateruse,orcompostedinwindrows.Manurescrapedfromthepensnormallyhasamoisturecontentof30to50percentandmaycontainsomesoilfromthepen.Becausethemanuremayremaininthepenorinstockpilesforseveralmonthsbeforeitisappliedtothefield,aportionofthenitrogenandcarbonmaybelostbeforethemanureiscollectedorappliedtoland.Runofffrompensisnormallycollectedinretentionponds.Settlingbasinsmaybeusedtolimitthequantityofmanuresolidsandsoilparticlesthatreachtheretentionpond.
IntheNorthernUnitedStates,andinareaswithhighrainfall,cattlemaybefedinnaturallyventilatedbarnswithslottedfloorsforcollectionofurineandfecesorindeep‐beddedbarnswithconcretefloorsinwhichthemanureandbedding(normallystraworstalks)areallowedto
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accumulateduringthefeedingperiod(Spiehsetal.,2011).Addingbeddingwillincreasethequantityofcarbon(andpossiblynitrogen)availabletobemetabolizedbymicrobesinthepen.Thesefacilitiesarecharacterizedbytheabsenceofrunoffcontrolsystems.
5.2.3 SheepProductionSystems
5.2.3.1 OverviewofSheepProductionSystems
Thereare81,000sheepandlamboperationsintheUnitedStates,withaninventoryof5.53millionsheepandlambsasofJanuary1,2011(USDANASS,2011).Mostbreedingflocksaresmallandconsistoflessthan100headofewes.Thelambfeedingindustryisalsodiverseinsize,withsmallfeedlotslocatedthroughoutthefarmflockareasandlargefeedingoperationslocatedincloseproximitytolocalgrainproductioncapacity(Shiflett,2011).
5.2.3.2 Diets,Housing,andManureHandlingforSheep
Lambingseasonmayoccuratvarioustimesduringtheyear,dependingonproductionobjectives,feedresources,environmentalconditions,andmarkettargets.Whenlambingoccurs,JanuarythroughMarch,ewesaregenerallyhousedinbeddedbarns.Beddingisremovedandspreadafteranimalsareturnedoutonpasture.EwesaregenerallybredonpastureinSeptemberthroughNovemberand,dependingonweather,willbemovedintobarnspriortolambing—orearlierasforageavailabilityandweatherdictate.Dietsconsistofpastureorgrazingcropresiduefromspringturnoutthroughearly‐andmid‐gestation.Whengrazedforageisnolongeravailable,ewesarehousedormovedtodry‐lotsandfedhayand/orhayandgraindietsasgestationrequirementsdictate.Theprimaryforagesourceisalfalfa,andcornisthepredominantgrain.Dietsrangefrom100percenthayto60:40percentforage:concentratewhilelactating.Mostlambsareweanedatapproximately90daysand41kgandsenttofeedlotsforfinishing.
Pasturelambingisanotherfarmflockproductionsystemthatisusedtomaximizenutrientsprovidedbygrazedforages.InthiscasetheeweisbredinNovemberorDecembertolambonpastureinAprilorMay.Lambsareweanedatapproximately120daysand32kgandmaybesenttothefeedlotorfinishedongrass.Ewesarenotfedgrain,andharvestedforageisprovidedonlywhengrowingseasonsandweatherdictate.Theseflockswillbehousedinbeddedbarnsinareasrequiringprotectionfromwinterweatherconditions.RangeproductionsystemsincludelambinginAprilorMay,wheremost(andinsomecasesall)dietsareprovidedbygrazedforages.Supplementationwithharvestedfeedsorgrainsisusuallyinresponsetounpredictableweatherandenvironmentalconditions.
Mostlambsarefinishedinfeedlotsandfeddietscontaining85to90percentgrain.Lengthoffeedingperiodswillrangefromweekstomonthsdependingonin‐weightsandtimerequiredtoreachfinalweight(industryaveragefinalweight=61kg).Sheepfeedlotsareprimarilydry‐lots,andmanureisscrapedfromthepenssimilarlytobeefcattlefeedlots.
5.2.4 SwineProductionSystems
5.2.4.1 OverviewofSwineProductionSystems
Theconceptualmodel(Figure5‐5)oftheU.S.swineproductionsystemprovidesanoverviewoftypicalproductionsystems,followinganimalsfrombirthtoharvestandfollowingmanurefromtheanimalthroughamanagementsystem.Manureisproducedduringeachstageofproductionoccurringinthesystem,anddependingonthelocation,ismanageddifferently.ThishasimplicationsonthequantityofGHGemissionsandsinks,someofwhicharediscussedindetailintheemissionsdiscussionsection(Section5.3.4).
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Figure5‐5:ConceptualModelofSwineProductionSystemsintheUnitedStates
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SwineproductionintheUnitedStatesremainsimportanttoboththenation’sdietandeconomy(Davies,2011),withsignificantlevelsofconsumption,imports,andexports.AccordingtotheU.S.DepartmentofAgriculture’sNationalAgriculturalStatisticsService,the2011populationwasnearly66millionhead(USDANASS,2012).
Swinearepredominantlygrownwithproductionofporkoccurringinatwo‐stageorthree‐stagesystem:
Stage1:Sowoperation,pigletsleaveatweaning. Stage2(optional):Nurseryoperation,weaning(10daysofage/17lbs)to42daysofage/45
lbs. Stage3:Severaloptions:
− Afinishingoperation(16‐weekproductionsitewherepigletsaredeliveredfromanurserysiteatapproximately42daysofage/45lbsandstayuntil154daysofage(22weeks)or
− Awean‐to‐finishoperation(24‐weekproductionsitewherepigsaredeliveredatweaningdirectlyfromasowoperation(10daysofage/17lbs)andstayuntil178daysofage(25.5weeks)).
Themanuremanagementsystemsassociatedwiththeseproductionoperationsallhavethebasicelementsofcollection,storage,treatment,transport,andutilization.Mostswinefacilitieshandlemanureasaslurryeitherwithinthebuilding(deeppitfinishingbarnsorshallowpitnursery,gestationorfinishingbarns)orinoutsidestorage(pull‐plugsystemsfornurseries,sows,orfinishingpigs).Collectionandstorageisgenerallyaccomplishedbystorageofthewasteunderthefacility,dischargetoaseparatestoragetank,orflushingtoananaerobiclagoon.Inthecaseofin‐housemanurestorage,littlewaterisaddedtothestoragestructure,andanaerobicconditionsprevailwithlittlebiologicalprocessingofmanuretakingplace.Outsidestoragestructuresthatcontainslurrywithlittledilutionwaterofferminimalbiologicaltreatmentaswell.However,lagoonsystemswheremanureisflushedfromhousingandadditionaldilutionwaterisaddedoffermoretreatment.Drysystemsordeep‐beddedsystemsexisttoamuchlesserextent,primarilyforsoworfinishingproduction.Inthesecasesbeddingmaterial,oftenstraw,isprovidedandmanureplusbeddingishandledassolidmaterial,sometimescomposted.
IntheMidwest,thesystemofmovingstoredswinewastetocropfieldsiswelldefinedandunderstood(HatfieldandPfeiffer,2005;Maloneetal.,2007;Jareckietal.,2008;Vanottietal.,2008;BrooksandMcLaughlin,2009;Jareckietal.,2009;Agnewetal.,2010;Cambardellaetal.,2010;Lovanhetal.,2010).Yetthesesystemscontinuetoevolvetoaddressbotholdandnewissues,suchasfrozenground,applicationtiming,andemissionsassociatedwithsoilapplicationvianewequipment.AllofthemanuremanagementsystemsresultinGHGemissions,buttheyvaryintermsofpointandnon‐pointsources.
5.2.4.2 DietInformationforSwine
Theswineindustryfeedsprimarilyacorn‐soybeanmealbaseddiet.Drieddistillersgrainswithsolubles(DDGS)areoftenfedtobothsowsandfinishingpigsand,asavailabilityofthisfeedincreases,theamountfedincreasestoasmuchas40percentofdietdrymatterintake(DMI).Similarly,whensyntheticaminoacidsourcespricecompetitivelywithfeedproteinsources,thenumberofsyntheticaminoacidsincludedinfinishingpigdietsincreases.Two(lysineandmethionine)ormore(threonine,perhapstryptophan)syntheticaminoacidsarefedcommonlytodaywiththebenefitofreducingtotalnitrogenfed,andthereforeexcreted,byswine.
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5.2.4.3 SwineHousingandManureHandling
Mostcommercially‐raisedfinishingswinearehousedindoorstoprovideabiosecureenvironmentandreducediseasepressures.Manureishandledasslurrywithlittleornobeddingaddedtothesystemandminimaladditionofwater.Asmallbutgrowingportionofthecommercialswineindustryhousebothfinishingpigsandsowsinhoopbarns.Inthesecases,beddingmaterial,oftenstraw,isprovided,andmanureplusbeddingishandledassolidmaterial.
5.2.5 PoultryProductionSystems
5.2.5.1 OverviewofPoultryProductionSystems
TheU.S.poultryproductionsystemiscomprisedofseveralkeyprocessesforpoultry,theirmanure/litter,andtheirendproducts(meat,eggs)asdepictedinFigure5‐6.
Thefigureprovidesanoverviewofthetypicalproductionsystems,followingboththelayerandbroilerphases.Thisconceptualmodelprovidesanoverviewofthetypicalpoultryproductionsystems,followingbirdsfrombirthtoslaughterandfollowingmanurefromtheanimalthroughamanagementsystem.Manureisproducedduringeachstageofactivitiesoccurringinthesystem,anddependingonthelocation,ismanageddifferently.TheemissionsfrommanuremanagementarediscussedindetailinSection5.3.
TheU.S.poultryindustryistheworld'slargestproducerandsecondlargestexporterofpoultrymeat.TheU.S.isalsoamajoreggproducer.Thepoultryandeggindustryisamajorfeedgrainuser,accountingforapproximately45.4billionkg(100billionlbs)offeedyearly.
Theeggincubationperiodforachickenis21days.Followinghatch,broilerchickensarerearedfor42to49days(sixtosevenflocksperyear),dependinguponthemarketintent(e.g.,roasters).U.S.eggoperationsproducemorethan90billioneggsannually.Morethan75percentofeggproductionisforhumanconsumption(thetable‐eggmarket).Theremainderofproductionisforthehatchingmarket.Theseeggsarehatchedtoprovidereplacementbirdsfortheegg‐layingflocksandtoproducebroilerchicksforgrow‐outoperations.Followinga16to22weekgrowthperiod,hensstartlayingeggs.
TheU.S.turkeyindustryproducesmorethanone‐quarterofabillionbirdsannually,withtheliveweightofeachbirdaveragingmorethan25lbs.Theeggincubationperiodforaturkeyis28days.Followinghatch,turkeypoultsarerearedfor15to22weeks(onetothreeflocksperyear)dependingonthemarketintent(e.g.,roasters).
5.2.5.2 DietandGrowthInformationforPoultry
Dietsformeatbirdsconsistlargelyofcornandsoybeanmeal(commonly85to92percentofthediet);however,alternateingredientssuchasdrieddistillersgrainswithsolubles(DDGS)andotherco‐products,andsyntheticaminoacidsareincreasinglyused.Hendietsaremostcommonlycomposedofcornandsoybeanmeal.Otheringredients,suchasDDGS,maybeincluded(rarelymorethan20percentofthediet).Ingredientvariabilityislargelyinsourcesofsupplementalenergy,minerals,andadditivestoimproveanimalhealthandperformance.Dietsareformulatedbasedongrowthrateandeggproductionandfedaseitheramashorapellet.Bonestrengthisanimportantcharacteristicofmeatbirdqualitythereforeprovisionofmineralssuchascalciumandphosphorusarecarefullyconsideredwhendietsareformulated.Similarly,eggshellqualityiskeyforlayinghens,andasaresult,calciumutilizationisakeyelementindietformulation.
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Figure5‐6:ConceptualModelofPoultryProductionSystemsintheUnitedStates
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Poultrybreedschangerapidly,demonstratingimprovedproductionefficiency,andassuch,dietsareincreasinglydensewithenergyandprotein.Thesechangesareduetoacombinationofgeneticsandmanagement,includingdietformulation.2WhiledietandgeneticinfluenceswereconsideredinastudybyHavensteinetal.(2007),theresultssuggestthatthedietchangesthatoccurredbetween1966and2003interactedwithotherfactors(flockage,ambienttemperature)toinfluencebirdgrowth.Someestimatethat85percentoftheimprovementinthegrowthrateofbroilerchickensisattributabletogenetics(Havensteinetal.,2003).3
IntheUnitedStatesthereisnoban,atpresent,onuseofantibioticgrowthpromoters(AGPs)inpoultryproduction(meatbirds).However,thetrendistowardconsumerswantingproductsthathavenotusedAGP.FindingreplacementsforAGPwilllikelyinvolvetheuseofmultipleproductsinthediet,eachwithsomeofthebenefitsofAGP,andmanagementchangeswillplayakeyroleinmaintaininganimalproductivityintheirabsence.Itisunlikelythatasinglereplacementwillbefoundthatwillprovetobeeconomicallyviable(DibnerandRichards,2005).
5.2.5.3 PoultryHousingandManureHandling
Thevastmajorityoftheindustryraisesbirdsonlitterinmechanicallyventilatedornaturallyventilatedhouses.Reuseoflitterandnumberofflocksgrownonthesamelitterisvariableacrossthecountry,andcanrangefromaslowasasingleflocktoasmanyas18flocksonthesamelittersource.Litterdrymattercontentcanvaryfrom40to80percent,dependingonmanagement.
Layinghenandpullethousingtypesrangefromhigh‐risehouseswherehensareincagesandmanureaccumulatesinabasementunderthecagesandisremovedannually,toamanure‐belthousewherehensareincagesandmanureisremoveddailyormorefrequentlyfromthebasementtoanexternalshedandstackedbeforeperiodicremovalforlandapplication(onceortwiceperyear),toaviarieswherehensareraisedonlitter(inlargeroomsasopposedtocages)thatisremovedfromtheaviaryannuallyormorefrequently.Whenmanureisremovedfromthehouseitmaybeimmediatelyappliedtofields,stockpiled,orcomposted.Moisturecontentmayvaryfrom80percentmoisturedownto20percentmoisture(aviaries).
5.3 EmissionsfromEntericFermentationandHousing
Emissionsfromanimalproductionsystemsincludethosefrombothentericfermentationandfromanimalhousing(includinganimalmanureinhousingareasthatmayultimatelybeflushedorscrapedandthentransportedtoanexternalmanuremanagementsystem).TheproductionofGHGsinlivestocksystemsoriginatesfromavarietyofsources,includingdirectlyfromtheanimalsthemselves;manureinlotsandbarns;stockpiledandcompostingmanures;manureslurriesorwatersintanks,pits,lagoons,retentionponds,settlingcells,etc.;andfromsoilsaftermanureapplication.Emissionsfromthesesourcesdependonanimalsizeandage,diet,manureproduction,handlingandstoragesystem,lotsurfaceandsoilcharacteristics,andambientweatherconditions(i.e.,temperature,wind,humidity,andprecipitation).Foreachanimaltype,thissectionsummarizes2Havensteinetal.(2007)compared1966strainsto2003strainsandobserveda20percentbettercumulativefeedconversionratiointhe2003tomturkeyfeda2003dietrelativetoa1966tomfedadiettypicalof1966.Feedefficiencyto11kgbodyweightwasapproximately50percentbetter(2.13at98daysofagein2003toms,comparedwith4.21at196daysfor1966toms).
3Havensteinetal.(2003)comparedthe1957Athens‐CanadianRandombredControlstrainandthe2001Ross308strainofbroilerswhenfedrepresentative1957and2001diets.The42‐dayfeedconversionsfortheRoss308birdsfedthe2001and1957feedswere1.62and1.92,respectively(withaveragebodyweightof2,672and2,126g).The42‐dayfeedconversionsfortheAthens‐CanadianRandombredControlwere2.14and2.34(averagebodyweightof578and539g,respectively).
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thecurrentunderstandingofentericfermentationandlivestockhousingemissionsandpresentsrecommendedmodelsforestimatingsuchemissions,includingtherationaleforselectingmethods.
ActualfieldmeasurementsofGHGsfromentericfermentationoverthepastseveraldecadeshavebeeninstrumentalinimprovingourunderstandingoftheunderlyingscienceandtheresultingmodelspresentedinthissection.Fordairyanimals,mostoftheemissionsestimatesavailablerepresentthelactatinganimal.Theequationsforgrowingbeefanimalsarelikelyappropriateforgrowingdairyanimalsifdietcompositionisconsidered.Thetextboxesonthefollowingpagessummarizeseveralofthekeytechniquesthathavebeenusedinmeasurementstudiesforbothindividualanimalsandgroupsofanimals.FurtherstudiesofthistypewillbeneededtoaddressresearchgapsinSection5.5.
ThissectionprovidestherecommendedmethodforestimatingGHGsfromentericfermentationandapplicablehousingemissions.Quantitativemethodsareprovidedfordairy,beef,sheep,swine,poultry,andotheranimals(i.e.,goats,Americanbison,llama,alpacas,andmanagedwildlife).Foreachsection,backgroundinformationisprovidedontherangeofemissionsandexistingmodelsforestimatingemissionsandtherationaleforthemethodselected.Forestimatingemissionsfromentericfermentation,theactivitydataisthesameforallanimaltypes.Ancillarydataincludesthepropertiesofthediets(e.g.,crudeprotein(CP),digestibleenergy(DE),neutraldetergentfiber(NDF)).Forsimplicity,activitydataandancillarydataarelistedinTable5‐2andarenotrepeatedbelowforeachanimaltype.
5.3.1 EntericFermentationandHousingEmissionsfromDairyProductionSystems
Althoughthedairyindustryisprimarilycomposedofthreelivestocktypes[growing(i.e.,calves,replacementheifers),lactatingcows,anddrycows],mostofthelimitedemissionsresearchconductedtodatehasbeentargetedatlactatingcows,whichtypicallyproduceatleast50percentmoreentericCH4perheadthanotherdairycattle.Fewemissionsdataexistforcalves,heifers,anddrycows.Therefore,thediscussionherefocusesprimarilyonlactatingcows.
Dataneededtoestimateemissionsincludehousingsystem(pasture,barntype,dry‐lot),animalcharacteristics(breed,bodyweight,growthpotential,stageoflactation,milkingfrequency,andmilkproduction)andpopulation,dietaryinformation(DMI,dietaryCP—alsoNDF,fat,DE,metabolizableenergy(ME),netenergy(NE),nutrientexcretion(N,C,andvolatilesolids),useofrecombinantbovinesomatotropin,useofmonensin,typeofmanurehandlingsystem,frequencyofmanureremoval,typeofbedding,andmanurecharacteristics(totalammoniumnitrogen,pH).
EntericFermentationEntericCH4productionvarieswithproductionstageindairycattle,withthehighestratesbeingproducedbylactatingcows(Table5‐4).Thistableillustrates,conceptually,theobservedvariationincattleatdifferentstagesofmaturityandactivity,butitisnotintendedtoprovideadepictionofabsolutedifferences.TherearemanyfactorsthataffectentericCH4production,andthereforealteringdairycattledietscouldhaveanimpactonentericCH4production.Foranin‐depthdiscussionofdietaryeffectsonentericCH4production,seeSection5.3.7(FactorsAffectingEntericFermentationEmissions).However,theresultsinTable5‐4clearlyillustratethedifferenceinentericemissions;inparticular,emissionsfromdairycattlearerelativelyhigherthanthosefromgrowing(i.e.,heifers)anddrycattle.
Table5‐4:ExamplesofCH4EmissionsMeasuredinDairyCattle
AnimalType CH4EmissionMethodUsedto
MeasureEmissions Reference
Dairycattle 260ganimal‐1day‐1CalculatedBlaxterandClapperton Crutzenetal.(1986)
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AnimalType CH4EmissionMethodUsedto
MeasureEmissionsReference
Heifer6‐24month 140gLU‐1day‐1 SeeaboveDairycattle,dryperiod 139gLU‐1day‐1 Respirationcalorimetry
Holter&Young(1992)Dairycattle,lactating 268gLU‐1day‐1 Seeabove
Dairycattle 257gLU‐1day‐1 Respirationcalorimetry Kirchgessneretal.(1991)
Dairycattle,lactating 429ganimal‐1 day‐1 WindtunnelSunetal.(2008)
Dairycattle,dryperiod 290ganimal‐1 day‐1 WindtunnelDairycattle,lactating 538–648ganimal‐1day‐1 Respirationcalorimetry Aguerreetal.(2011)LU,livestockunit=500kg
MethodsforMeasuringCH4 EmissionsfromEntericFermentation
IndividualAnimalsThestandardmethodofmeasuringCH4emissionsfromruminantsisbyrespirationcalorimetrychambers.Othertechniques,includingheadboxes,internaltracers,micrometeorology,isotopedilution,andpolyethylenetunnels,havebeenused(Kebreabetal.,2006;Harperetal.,2011).Severalnewtechnologieshavebeendevelopedtomeasureindividualanimalemissions.ToaddressthedifficultyinmeasuringentericCH4frommanyanimalsonpasture,alternatemethodsaresought.Asoneexample,Goopyetal.(2011)hasproposedaportablestaticchambermethodtomeasuredailyCH4production.Untilvalidated,resultsusingalternatemethodsshouldbeviewedwithcaution.
AvarietyofrespirationchambershavebeendevelopedtomeasureentericCH4lossesand/ortotalenergymetabolismoftheanimal.Ingeneral,airispulledfromthechamberataknownrateandreplacedwithoutsideair.FlowofairandconcentrationsofCH4,CO2,andoxygen(O2)intheairenteringandleavingthechamberaremeasuredtodeterminetotalCO2andCH4productionandO2consumption.Whenproperlycalibratedandused,respirationchambersgivehighlyaccurate,precisemeasurements.However,theyareexpensivetobuildandoperate,andrequiresignificantknowledge,skill,andlabor.
Feedintakeandproductionareusuallydepressedinanimalsinchambersandthemeasurementsdonotnecessarilyreflectintakeandproductionfromtypicalcommercialoperations.Thislimitationcanbepartiallyovercomebyfeedinganimalsatdifferentlevelsofintakeandmeasuringtheeffectsofintakelevel.Headboxesusethesameprinciplesasrespirationcalorimetry,andhavemanyofthesamelimitations.In‐barnchambersusingdrop‐downcurtainshavebeenusedtomeasure,atrelativelylowcost,emissionsofNH3,CH4,andothergassesfromgroupsofdairycows(Powelletal.,2007;Powelletal.,2008;Aguerreetal.,2011).
Internaltracertechniquessuchasthesulfurhexafluoride(SF6)tracermethod(Johnsonetal.,1994)weredevelopedtoallowmeasurementsfromfree‐ranginganimals,suchasthosemanagedunderpasturesituations,orwhenreal‐worldlevelsoffeedintakeareneeded.Thelimitationstothismethodaretheneedfortrainedanimals,theneedforlargersamplesizes(comparedwithchambers)todetecttheinfluenceofmitigationtechniques,andconcernsaboutinconsistentreleasesoftracergasfromSF6permeationtubesmanufacturedforlargereleaserates.Additionally,theSF6techniquegenerallyresultsinemissionestimatesthatarelowerthanchambermeasurements;possiblybecausetheSF6methoddoesnotmeasurealllowergutCH4production(McGinnetal.,2006).TheadvantagesandshortcomingsoftheSF6methodhavebeenrecentlyreviewed(Lasseyetal.,2011).
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Methods for Measuring CH4 Emissions from Enteric Fermentation
Group of Animals
MicrometeorologymethodshavebeenusedextensivelytomeasureCH4andNH3emissionsfrompastures,wholefeedyards,orportionsofthefeedyard(pens,retentionponds,manurestockpiles,etc.).Thesemethodshavebeenreviewed(Fowleretal.,2001;Fleschetal.,2005;Harperetal.,2011).Laubacketal.(2008)comparedtheSF6methodwiththreemicrometeorologicalmethods(integratedhorizontalflux,fluxgradient,andbackwardLagrangianstochastic(bLS))usingsteersgrazingpaddocks.Ingeneral,themicrometeorologicalmethodsgavehigherCH4measurementsthantheSF6method,withthedifferencebeinggreaterwhenanimalswerewithin22metersoftheCH4sampler.Thiseffectwasespeciallytrueforthefluxgradientmethod.ThelowervaluesfortheSF6methodcouldbedueinparttothefactthattheSF6methoddoesnotmeasureemissionsfromthelowergutorfromfermentationoffecesonthepaddocksurface.
Tomkinsetal.(2011)comparedentericCH4emissionsofsteersonpastureusingthebLSmethodandrespirationchambers.EmissionsestimatedusingthebLSmodelwereslightlygreaterthanwithrespirationchambers(136.1vs.114.3gheaddaily‐1).HoweveremissionspergramofDMIweresimilar(29.7vs.30.1gCH4kgDMI‐1,respectively),suggestingthatthebLSmodelmaybesuitableforestimatingentericemissions.
Mostdispersionmodelsandmicrometeorologicalmethodsassumethatemissionsareuniformlydistributedoverthesourcearea.Insomecases,suchasforindividualcattleinapenorfield,thisisnottrue.Therefore,McGinnetal.(2011)developedamethodthatusedapoint‐sourcedispersionmodelandatmosphericCH4concentrationsmeasuredusingmultipleopen‐pathlaserstomeasureCH4emissionsfromapaddockcontaining18cattle.MeasuredentericCH4emissionsweresimilartovaluesmeasuredusingothertechniques.However,recoveriesofknownCH4releasesaveragedonly77percentusingthismethod.Themethodgavemorereliablemeasurementsduringthedaytimewhenatmosphericconditionswereunstablethanatnightwhenatmosphericconditionswerestable.
Methods for Measuring Emissions from Manure
Estimatingemissionsfromlargeopensourceareastypicallyassociatedwithbothdairyandbeefcattleproductionisverychallenging,duetotheinabilitytocontainandmeasurethesourcearea.Instrumentsandtechniquestomeasureambientatmosphericgasesfromtheselargesourceareas(i.e.,dry‐lotbeefanddairycattleyards,freestalldairieswithnaturallyventilatedcurtainsidewallbarns,andgrazingland)mustbeabletodetectlowerconcentrationsthanthoseencounteredintypicalenclosedconfinedanimalproductionsystems,becauseofthelowconcentrationsandhighvariabilityresultingfromhighandvariableventilationrates.Alargerchallengewithmeasuringemissionsfromopenfacilitiesistheabilitytoestimateairflowduetothelackofadefined,constantairinletandairoutlet.ReportedbackgroundNH3concentrationstypicallyrangefrom<1.3to53.3partsperbillion(ppb)(Toddetal.,2005),backgroundatmosphericN2Oconcentrationsnearfeedyardsaverageabout319ppb(Michaletal.,2010),andbackgroundCH4concentrationstypicallyrunintheareaof1,780ppb(Michaletal.,2010).
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Methods for Measuring Emissions from Manure (Continued)
NumerousfactorscanaffectatmosphericconcentrationsofNH3andGHGnearlivestockoperationsincludingsamplingheight,atmosphericstability,windspeed,backgroundconcentrations,stockingdensity,samplingsite,samplingtime,temperature,andwinddirection(fetch).AveragedailyNH3concentrationsmeasuredatavarietyofsimilarsourceareasrangedfromapproximately100to2,000µgm‐3.Measuredmaximumconcentrationsrarelyexceed2,000µgm‐3.Ammoniaconcentrationsdecreaserapidlydownwindofsourceareas(Miner,1975),approachingbackgroundconcentrationsinlessthan800meters(McGinnetal.,2003;Sweeten,2004).
AtmosphericCH4concentrationsmeasuredatfeedlotsanddrylotdairieshaverangedfrom3.3to4.7partspermillion(ppm)(Michaletal.,2010),andfrombackground(approximately1.78ppm)to6.20ppm(Bjornebergetal.,2009),respectively.Nitrousoxideconcentrationsmeasuredatfeedlotsrangedfrom319ppb(background)to443ppbandaveraged396±16ppb(Michaletal.,2010).Nitrousoxideconcentrationswerehighestfollowingarainfallevent.Afterarain,CH4concentrationsaveraged3.7±0.1ppm.Atdry‐lotdairies,medianN2Oconcentrationsrangedfrom314ppbto330ppb,whichareveryclosetoglobalbackgroundvalues(Bjornebergetal.,2009).
SmallfluxchambersandwindtunnelshavebeenusedtoestimateemissionsofNH3,CH4,andN2Ofromfarmlands,pastures,pensurfaces,lagoons,andretentionponds(HutchinsonandMosier,1981;Ventereaetal.,2009;Venterea,2010;Harperetal.,2011;Hristovetal.,2011).Ingeneral,chambersalterthemicroenvironmentofthesurfaceandmayalteremissions.Thus,theaccuracyofthesemethodsfordeterminingemissionfactorsforsomegases(especiallyNH3)hasbeenquestioned(GaoandYates,1998;Harper,2005;Ventereaetal.,2009;Parkeretal.,2010;Venterea,2010;Harperetal.,2011).MeasuresofNH3emissionsusingfluxchambersandwindtunnelsarehighlydependentuponairflowandairturnoverratesinthechamber(Coleetal.,2007b;Parkeretal.,2010).Basedontheconventionaltwo‐filmmodelusedtodescribevolatilizationfromasolute‐solventmixture(Parkeretal.,2010),manygaseousemissionsarecontrolledbythegasfilmabovetheliquidortheupperportionoftheliquid(liquidfilm)definedbytheHenry’slawconstant.Ifvolatilizationisinhibitedbyhighconcentrationsinthegasphase(i.e.,gas‐filmcontrolled),increasesingaseousconcentration—suchaswithfluxchambers—willleadtosignificantunderestimationoftrueflux.Venterea(2010)reportedthatemissionsofN2Oestimatedusingstaticchamberswereunderestimatedbyapproximatelythreeto38percent,dependinguponsoilwatercontent,typeofregressionperformed(linearvs.quadraticvs.nonlinear),andotherfactors.Thepercentageofunderestimationtendedtobegreaterwithdrysoils,probablybecauseN2Ofluxislowerwhensoilsaredry.Sommeretal.(2004)reportedthatGHGemissionsfromcompoststockpilesmeasuredusingstaticchamberswereonly12to22percentofvaluesmeasuredusingtheintegratedhorizontalfluxmethod.
Becauseofthesefactors,fluxchambersshouldbeusedtoexaminerelativedifferences,ratherthanemissionfactorsofNH3,CH4,andN2Oemissionsfrompensurfaces,lagoons,retentionponds,manurestockpiles,orcompostwindrows.Inaddition,thesurfaceofpasturesandfeedlotpensistemporallyandspatiallyheterogeneous,withdryareas,areaswithfreshfeces,andareaswithurineofdifferentages(Woodburyetal.,2001;Coleetal.,2009a;Coleetal.,2009b).Toadequatelyrepresentthesurface,thenumberofchambermeasurementsrequired(estimatedasthecoefficientofvariationsquared/100:Kienbusch,1986)canbeverylarge(i.e.,onechamber/quaremeter:Coleetal.,2007b).
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HousingThereareawidevarietyofdairycattlehousingsystemsduetovariationsinherdsizeandregionalpractices.InthenortheasternUnitedStates,herdsizetendstobesmallerandcattlearehousedinfreestallandtie‐stallbarnsandonpasture;inthewesternpartofthecountry,herdsizestendtobelargerandanimalsarehousedinfreestallbarnsordry‐lotswithfewproducersusingpasture‐basedsystems.ThesedifferencesinhousingcanleadtodifferencesinbothGHGandNH3emissions.ExamplesofreportedemissionsfromvaryinghousingsystemsarepresentedinTable5‐5.
Table5‐5:ExamplesofReportedOn‐FarmEmissionEstimatesforCH4,N2O,andNH3fromaVarietyofDairyCattleHousingSystems
Housing CountryEmissions(gcow‐1d‐1)
ReferenceCH4 N2O NH3
Barn Germany 402 64.8 Sahaetal.(2014)Tiestallbarn Austria 170‐232a 0.14‐1.2a 4‐7.4a Amonetal.(2001)Barn Germany 256 1.8 14.4 Jungbluthetal.(2001)Dry‐lot U.S. 41‐140 Casseletal.(2005)Hardstanding UK 0.03b 0.01 11 Ellisetal.(2001)Open‐freestall U.S. 410 22 80 Leytemetal.(2013)Tiestallbarn Canada 390 Kinsmanetal.(1995)Pasture NZ 300‐427 Laubach&Kelliher(2005)Dry‐lot U.S. 490 10 130 Leytemetal.(2011)Standoffpad NZ 1.66b 0.03 Luo&Saggar(2008)Barn Denmark 256 1.2 16 Zhangetal.(Zhangetal.,2005)Dry‐lot China 397 37 Zhuetal.(Zhuetal.,2014)Barn Sweden 216‐312a 21‐27a Ngwabieetal.(2009)Barn Germany 464 45 92.4 Sameretal.(Sameretal.,2011)Pasture Uruguay 372 Dinietal.(Dinietal.,2012)
*DenotesmeasurementsingLU‐1d‐1,whereaLU(livestockunit)=500kg.†MeasurementsdonotincludeentericCH4production.
Variationsinemissionsfromhousingareduetofactorssuchastemperature,dietcomposition,waterconsumption,ventilationflowrates,typeofmanurehandlingsystems,manureremovalfrequency,feces,andurinecharacteristics(i.e.,pHandtotalammoniacalnitrogen(TAN)),andtypeofbeddingused.Althoughdifferencescanbegreatbetweenemissionrates,therearesomeemissioncharacteristicsthatareconsistentacrossmoststudies.ManystudieshavereportedstrongdieltrendsinemissionsofCH4andNH3,withemissionstendingtobelowerinthelateeveningandearlymorningandthenhigherthroughoutthedaytillearlyevening(Amonetal.,2001;Casseletal.,2005;Powelletal.,2008;Sunetal.,2008;Bjornebergetal.,2009;Fleschetal.,2009;Ngwabieetal.,2009;Aguerreetal.,2011;Leytemetal.,2011).Thisstrongdieltrendinemissionscanbeassociatedwithwindspeedandtemperature,aswindstendtobelightinthelateeveningandearlymorningandthen,inmostinstances,steadilyincreasethroughoutthedaytoreachapeakinthelateafternoon.Temperaturealsoincreasesfromearlymorningtolateafternoon,andthendecreasesagain.Additionally,cattleactivitytendstoincreasefrommorningtolateafternoonasanimalswakeandbegintoeat,drink,ruminate,defecate,andurinate.Astheseactivitiesincrease,onewouldexpectanincreaseinCH4(andNH3)emissions.Therearealsoseasonaltrendsinemissions,themostprominentbeinginNH3emissions,withthelowestratesinwintercomparedwiththeotherseasons(Amonetal.,2001;Powelletal.,2008;Bjornebergetal.,2009;Fleschetal.,2009;Aguerreetal.,2011;Leytemetal.,2011).Powelletal.(2008),Fleschetal.(2009),andAguerreetal.(2011)reportedthatbarnemissionsofNH3inWisconsinwerelowestinwinter,withwinterratesaboutone‐halftoone‐thirdlowerthanthoseinthespringandsummer,whichwas
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-36
Ammonia Emissions in Dairy Cattle Housing
Asmentionedearlier,ammoniaisnotagreenhousegas,however,ammoniaemissionsareestimatedaspartofthenitrogenbalanceapproach.EmissionsofNH3fromdairycattlehousingsystemshavebeenstronglylinkedtodietarynitrogenintake,asthisaffectstheamountofureanitrogenexcretedinurine.Ofthenitrogeninthetotalcrudeprotein(CP)typicallyconsumedbyadairycowoncommercialdairyfarms,20to35percentissecretedinmilkandtheremainingnitrogenfromCPisexcretedaboutequallyinfecesandurine.Feednitrogen(N=CP÷6.25)useefficiency(percentageoffeednitrogensecretedasmilknitrogen)andthe50:50fecalnitrogen:urinarynitrogenexcretionratiocanbeinfluencedgreatly,however,bywhatisfedtothecow.Feedingnitrogeninexcessofnutritionalrequirementshasveryfewsignificantimpactsonmilkproductionorquality;itdecreasesfeednitrogenuseefficiencyandincreasestherelativeamountofureanitrogenexcretedinurine.Theureanitrogencontainedincowurine(whichis55to80percentofthenitrogencontainedinurine,dependingonconcentrationsofCPintheration)isthemajorsourceofNH3emissionfromdairyfarms.Ureaisproducedwhennitrogen‐richproteinsand/ornon‐proteinnitrogensourcesbreakdown(mainlyinthecowrumen),formingNH3gasthatmaybeusedbyruminalmicrobestoproducemicrobialproteinsorcanbeabsorbedthroughtheruminalwalltothebloodstream.Inthekidney,bloodNH3fromthedigestivetractortissuemetabolismiseventuallyconvertedtoureabeforebeingexcretedintheurine.Ureaseenzymes,whicharepresentinfecesandsoil,rapidlyconvertexcretedureatoammonium,whichcanbehydrolyzedquicklyintoNH3gasandlosttotheatmosphere.Thus,theincreaseinureanitrogenexcretionduetoexcessiverationCPincreasesNH3emissionsduringthecollection,storage,andlandapplicationofmanure(Rotz,2004;Misselbrooketal.,2005;Powelletal.,2008;Arriagaetal.,2010).
Pauletal.(1998)examinedtheeffectsofalteringdietaryCPonNH3lossesfromdairycows.TheyreportedthatNH3emissionsduringthefirst24hoursfollowingmanureexcretionwere38and23percentofthetotalmanurenitrogenfromdietswith16.4and12.3percentCPconcentrations,respectively,and22and15percentoftotalmanurenitrogenfromdietscontaining18.3and15.3percentdietaryCP,respectively.Misselbrooketal.(Misselbrooketal.,2005)reportedthatreducingdietaryCPcontentresultedinlesstotalnitrogenexcretionandasmallerproportionoftheexcretednitrogenbeingpresentinurine;urinenitrogenconcentrationwas90percentgreaterforthehigh‐CPthanthelow‐CPdiet.
However,Lietal.(2009)foundnoeffectofloweringdietaryCPinlactatingdairycattleonNH3emissionsfromthefloorofanaturallyventilatedfreestalldairybarnatlowandmoderatetemperatures(0to20°C).ThislackofresponsetoCPislikelyduetothefactthatureaseactivityisnegligibleattemperaturesbelow10°C(Bluteauetal.,2009).FactorsthatareessentialindeterminingNH3emissionsaremanureorurinepHandthetotalammoniacalnitrogencontent,bothofwhicharerelatedtothedietaryCPlevel.
ThemajorityofNH3emissionsfromhousingsystemsareduetothevolatilizationofNH3fromurinedeposition.Asdiscussedabove,nitrogenintakedrivestheamountofureathatisexcretedintheurine.Asthisurineisdepositedonbarnfloors,pastures,ordry‐lots,itmixeswithureasefromeitherfecesorsoilandisthenhydrolyzedtoammoniumand,viaeffectsofpH,convertedtoNH3andlosttotheatmosphere.ThelossofNH3happensrapidly,withmostNH3lossesoccurringwithin24hoursfollowingdeposition.Therefore,estimationofNH3emissionsneedstotakeintoaccounttheamountofureageneratedbythecow,pH(urine,manure,orsoil),temperature,andairflowoverthesource.StrategiesthatreducenitrogenexcretionwillbeverybeneficialinreducingNH3emissionsfromhousing/pasturesystems.
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
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attributedtocoldwintertemperatures.Ingeneral,N2Oemissionsfromhousingwerefoundtobelowandshowednodiscernibledielorseasonaltrends(Bjornebergetal.,2009;Ngwabieetal.,2009;Adviento‐Borbeetal.,2010;Leytemetal.,2011),suggestingthattheseemissionsfromthissectoroftheproductionsystemareofrelativelylittleconcern.ThereareconsistentreportsofbothdielandseasonalvariationsinbothCH4andNH3emissions,soitisimperativethatthesefactorsbecapturedinanyestimationofemissionsforagivenproductionsystem.
EmissionsofCH4aredominatedbyentericfermentationinhousing/pasturesystems.Amonetal.(2001)examinedCH4emissionsfromatie‐stalldairybarninAustriausingeitheraslurry‐basedsystemorstraw‐basedsystem.Inbothsystems,about80percentofthenetCH4emissionswereduetoentericfermentation,withtheremainingamountcomingfromthemanure.Sunetal.(2008)measuredCH4emissionfromdairycowsandfreshmanureinchambers,andreportedthatfreshmanurealonedidnotproducenoticeableCH4fluxes.Insomedairyproductionsystems,manureisremovedfromtheanimalhousingareafrequently;therefore,CH4emissionsfromanimalhousingareasofadairycanbelargelyattributedtoentericemissions.
N2Oemissionstendtobenegligiblefrombothanimalsandfreshmanure.ThemajorityofN2Oemissionsresultfrommanurestorage,pasture,andlandapplicationofmanures.Therefore,themainsourcesofN2Oemissionsfromanimalhousingwouldbefromdry‐lotdairiesandstand‐offpads,becausethereispotentialfordepositednitrogentobenitrifiedanddenitrifiedunderwetconditionsandlostasN2O.LuoandSaggar(2008)measuredN2OandCH4emissionsfromadairyfarmstand‐offpadinNewZealandandreportedN2Ofluxesfrom0to3gN2O‐Nday‐1,whichtheyattributedtotheconcentrationsofwaterandnitrateinthepadmaterials.Overall,only54gofN2O‐Nwasemittedfromthepadoverthetimeofuse,representing~0.01percentoftheexcretanitrogendepositedonthepad.
Whiletherehavebeenoverallimprovementsinmilkproductionwithbreedingprograms,thereisnoevidencethatanybreedofdairycowproduceslessentericCH4.MüngerandKreuzer(MüngerandKreuzer,2008)measuredentericCH4productionfromHolstein,Simmental,andJerseycowsandfoundnopersistentdifferencesinCH4yields,withaverageentericCH4beingapproximately25gCH4kgDMI‐1.
5.3.1.1 MethodforEstimatingEmissionsfromDairyProductionSystems
Methodfor Estimating CH4 Emissions from Enteric Fermentation in Dairy Cows
Millsetal.(2003)developedaseriesofsubmodelstoestimateentericCH4emissionsfromdairyandbeefcattle.TheoptimalmodelappearedtobeanonlinearMits3equation,whichisutilizedbytheDairyGEMModel(asubsetofIFSM)(Rotzetal.,2011b)andisshowninEquation5‐1(Mits3equation)isbasedprimarilyonmetabolizableenergyintake,aciddetergentfiber(ADF),andstarchcontentofdiet.
Datasourcesareuserinputondietaryintake,aswellasdietarydatafromtheFeedstuffsCompositionTable(Ewan,1989;Preston,2013).
UseoftheDairyGEM/Mits3equationisrecommendedovertheIPCCTier2equation(IPCC,2006)becauseithasproventobemoreaccurate,ingeneral,fordairycows.
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-38
TheEmaxisconstantforallanimalsat45.98MJ/head/day.Theshapeparameter“c”iscalculatedfromthedietarynon‐fibercarbohydrate(NFC)toaciddetergentfiber(ADF)ratioinEquation5‐2.
Millsetal.(2003)notedthatnonlinearmodelshavetwoadvantagesoverlinearmodels:1)amaximumemissionisset;and2)itisexplainablefromabiologicalsense.Thefeedstuffcharacteristicsneededtocalculateemissionsfromdairycattleareincludedintheexamplebelow(Ewan,1989;Preston,2013).ThefulltablecanbefoundinAppendix5‐B.
Table5‐6:ExampleFeedstuffsTablea
FeedstuffDM%
Energy Protein FiberEE%
ASH%
Ca%
P%
K%
Cl%
S%
ZnppmTDN
%NEm NEg NEl
(Mcal/cwt.)
DE(%ofGE)*
CP%
UIP%
CF%
ADF%
NDF%
eNDF%
AlfalfaCubes
x91 57 57 25 57 18 30 29 36 46 40 2.0 11 1.30 0.23 1.9 0.37 0.33 20
Alfalfadehydrated17%CP
92 61 62 31 61 65.16 19 60 26 34 45 6 3.0 11 1.42 0.25 2.5 0.45 0.28 21
Alfalfafresh
24 61 62 31 61 62.54 19 18 27 34 46 41 3.0 9 1.35 0.27 2.6 0.40 0.29 18
Source:Preston(2013).
Equation5‐1:Non‐LinearMits3Equation
exp .
Where:
CH4 =Entericmethaneemissionsperday(kgCH4head‐1day‐1)
Emax =MaximumpossibleCH4emissions(MJhead‐1day‐1)
c =Shapeparameterdeterminingemissionchangewithincreasingmetabolizableenergyintake(seeEquation5‐2)
x =Metabolizableenergyintake(MJhead‐1day‐1)
0.018=ConversionofMJtokgofCH4(kgCH4MJ‐1)
Equation5‐2:CalculatingShapeParameter
. .
Where:
c =Shapeparameterdeterminingemissionchangewithincreasingmetabolizableenergyintake(unitless)
NFC =[(100‐NDF+CP+EE)/100]xDMI(kghead‐1day‐1)
DMI =Drymatterintake(kgdryfeedanimal‐1day‐1)
ADF =AcidDetergentFiber(kghead‐1day‐1)
NDF =NeutralDetergentFiber(%)
CP =CrudeProtein(%)
EE =Etherextract(%)
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-39
aColumnheadings:DM =Drymatter GE = Grossenergy ASH =AshTDN =Totaldigestiblenutrients CP =Crudeprotein Ca =CalciumNEm =Netenergyformaintenance UIP = Undegradableintakeprotein P =PhosphorousNEg =Netenergyforgrowth CF = Crudefiber K =PotassiumNEl =Netenergyforlactation ADF = Aciddetergentfiber Cl =ChlorineMcal =Megacalories NDF = Neutraldetergentfiber S =Sulfurcwt =Centumweight(hundredweight) eNDF = effectiveneutraldetergentfiber Zn =ZincDE =Digestibleenergy EE = Etherextract ppm =partspermillion
MethaneEmissionsfromDairyCows’Housing
TheDairyGEMModel(Rotzetal.,2011a)calculatesCH4emissionsfrombarnfloorsusinganempiricalmodeldevelopedfromthreefreestallbarns(Chianeseetal.,2009c).
Whenmanureisallowedtoaccumulateasastockpile,onadry‐lot,orinapitbelowtheanimalconfinement,theDairyGEMmodelusestheIPCC(2006)Tier2methodtoestimateCH4emissions(Equation5‐4).Thisisthesameequationusedforestimatingemissionsfrommanurethatismanagedoutsideofhousing(seeSection5.4.1TemporaryStackandLong‐TermStockpileand5.4.2 Composting for details).
Methodfor Estimating Dairy Cows’ GHG Emissions from Housing
Methane
TheDairyGEMModel(asubsetofIFSM)(Rotzetal.,2011a)calculatesCH4emissionsfromhousingsurfaces.
DairyGEMusestheIPCC(2006)Tier2methodtoestimateCH4emissionswhenmanureisallowedtoaccumulateinthehousing.
NitrousOxide
NitrogenexcretedestimatedusingequationsprovidedinASABED384.2. IPCC(2006)Tier2approachforN2Oemissionsfrommanureinhousing.
Equation5‐3:CalculatingCH4EmissionsfromBarnFloors (Chianeseetal.,2009c)
. , .
Where:
CH4=Methaneemissionsperday(kgCH4head‐1day‐1)
T =Barntemperature(˚C)
Abarn =Areaofthebarnfloorcoveredwithmanure(m2)
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-40
ThemaximumCH4producingcapacity(B0)formanurevariesbyanimalcategoryandisprovidedinTable5‐19.TheCH4conversionfactors(MCF)formanuredepositedonadry‐lot,storedinadeeppit,orfromcattlebeddingcanbefoundinTable5‐7.TheMCFsformanurestoredasastockpileareprovidedinTable5‐20throughTable5‐22.TheMCFsformanurecompostedwithinhousingareprovidedinTable5‐24.
Table5‐7:MethaneConversionFactorsforDry‐Lots,PitStorageBelowAnimalConfinement,andCattle/SwineBedding
Temperature Dry‐Lot
PitStorageBelowAnimalConfinementand
Cattle/SwineDeepBedding
<1month >1month
Cool
≤10°C
1% 3%
17%11°C 19%12°C 20%13°C 22%14°C 25%
Tem
perate
15°C
1.5% 3%
27%16°C 29%17°C 32%18°C 35%19°C 39%20°C 42%21°C 46%22°C 50%23°C 55%24°C 60%25°C 65%
Warm 26°C
2% 30%71%
27°C 78%≥28°C 80%
Source:IPCC(2006).
Equation5‐4:IPCCTier2ApproachforEstimatingCH4 EmissionsinHousing
.
Where:
ECH4 =CH4emissionsperday(kgCH4day‐1)
m =Totaldrymanureperdaya(kgdrymanureday‐1)
VS =Volatilesolids(kgVS(kgdrymanure)‐1)
B0 =MaximumCH4producingcapacityformanure(m3CH4(kgVS)‐1)
MCF =CH4conversionfactorforthemanuremanagementsystem(%)
0.67 =Conversionfactorofm3CH4tokgCH4
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-41
TheSommermodelisusedtoestimateemissionsfromanyliquidmanure(lessthan10percentdrymatter)storedinhousing.TheestimationmethodforliquidmanurecanbefoundinSection5.4.4AnaerobicLagoon,RunoffHoldingPond,StorageTanks.
NitrousOxideEmissionsfromDairyCows’Housing
Toestimatenitrogenlossesfromhousing,theamountofnitrogenexcreted(Nex)byeachanimalcategoryisfirstestimated.Equation5‐5,Equation5‐6,andEquation5‐7aretheequationsrecommendedbytheAmericanSocietyofAgriculturalandBiologicalEngineers(ASABE)forestimatingNex.
SomeofthenitrogenexcretedisvolatilizedasNH3,hence,theestimationofNH3lossesisnecessarytoestimateN2Oemissionsusinganitrogenbalanceapproach.TheNH3lostfrommanureinhousingisestimatedasafractionofNex,KoelschandStowell(2005)provideestimatesonthetypicalNH3lossfromdifferenthousingfacilitiesandanimalspeciesasafractionofNex(seeTable5‐8).Arange
Equation5‐5:ASABEApproachforEstimatingNitrogenExcretionfromLactatingCows
. . . ..
Where:
Nex =Totalnitrogenexcretionperanimalperday(gNanimal‐1day‐1)
Milk=Milkproductionperanimalperday(kgmilkanimal‐1day‐1)
DIM =Daysinmilk(days)
DMI =Drymatterintake(kganimal‐1day‐1)
CCP =Concentrationofcrudeproteinoftotalration(gcrudeprotein(gdryfeed)‐1)
BW =Averagelivebodyweight(kg)
Equation5‐6:ASABEApproachforEstimatingNitrogenExcretionfromDryCows
. . .
Where:
Nex =Totalnitrogenexcretionperanimalperday(gNanimal‐1day‐1)
DMI =Drymatterintake(kgdryfeedanimal‐1day‐1)
CCP =Concentrationofcrudeproteinoftotalration(gcrudeprotein(gdryfeed)‐1)
Equation5‐7:ASABEApproachforEstimatingNitrogenExcretionfromHeifers
. .
Where:
Nex =Totalnitrogenexcretionperanimalperday(gNanimal‐1day‐1)
DMI =Drymatterintake(kgdryfeedanimal‐1day‐1)
CCP =Concentrationofcrudeproteinoftotalration(gcrudeprotein(gdryfeed)‐1)
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-42
ofvalueshasbeenprovidedforeachfacilitytype;thelowervaluesshouldbeusedduringthewinter,thehighervaluesshouldbeusedduringthesummer,andintermediatevaluesshouldbeusedforthespringandautumn.
Table5‐8:TypicalAmmoniaLossesfromDairyHousingFacilities(PercentofNex)
FacilityDescription %Loss FacilityDescription %Loss
Opendirtlots(cool,humidregion) 15‐ 30 Roofedfacility(shallowpitunderfloor) 10‐ 20Opendirtlots(hot,aridregion) 30‐ 45 Roofedfacility(beddedpack) 20‐ 40Roofedfacility(flushedorscraped)Roofedfacility(dailyscrapeandhaul)
5‐15Roofedfacility(deeppitunderfloor‐includesstorageloss)
30‐40
Source:KoelshandStowell(2005).
N2Oislostfromtheexcretednitrogen.AquantitativemethodforestimatingN2OemissionsfromsolidmanureistheIPCCTier2approach,whichisalsousedfortheU.S.GreenhouseGasInventory(Equation5‐8).ThisestimationmethodisthesameasthemethodpresentintheTemporaryStackandLong‐TermStockpileandthe
Compostingsections(SeeSections5.4.1and0).Thisequationwillover‐estimatetheemissionsfromanimalhousingifsomeofthenitrogenexcretedismanagedoutsideofhousing(i.e.,theequationaccountsfornitrogenlossduetoNH3emissionsbutdoesnotaccountforthequantityofnitrogenthatismanagedinmanuremanagementsystems).
Formanureindeeppits,dry‐lots,ormixedwithbedding,theemissionfactorsareprovidedinTable5‐9.TheN2OemissionfactorsformanureinhousingthatisstoredinastockpileareprovidedinTable5‐23.TheemissionfactorsformanurethatiscompostedwithinahousingareaareprovidedinTable5‐25.
Table5‐9:N2OEmissionFactorsforManureStoredinHousing
Category N2OEmissionFactor(kgN2O‐N/kgN)CattleandSwineDeepBedding(ActiveMix) 0.07CattleandSwineDeepBedding(NoMix) 0.01PitStorageBelowAnimalConfinements 0.002Dry‐Lot 0.02
Source:IPCC(2006).
Equation5‐8:IPCCTier2ApproachforEstimatingN2OEmissionsfromHousing
, % /
Where:
EN2O,housing =Nitrousoxideemissionsfromhousingperday(kgN2Oday‐1)
N =Numberofheadoflivestockspecies(animal)
Nex =Totalnitrogenexcretionperanimalperday(gNanimal‐1day‐1)
%NH3loss =PercentofNexlostasNH3inanimalhousing‐seeTable5‐8
EFN2O =N2Oemissionfactorformanureinhousing(kgN2O‐NkgN‐1)
=ConversionofN2O‐NemissionstoN2Oemissions
=Conversionofgramstokilograms
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-43
TheremainingnitrogenexcretedthatisnotlostasN2OorvolatilizedasNH3inhousingthenentersmanurestorageandtreatment.Ifdataarenotavailabletotrackthenitrogenthatistransferredalongwiththemanure‐to‐manurestorageandtreatment,thenitrogencanbeestimatedasdescribedinEquation5‐9.However,thisequationisoverestimatingthenitrogentransferringtomanurestorageandtreatmentassomenitrogenwillbelostinhousing.ThisremainingtotalnitrogenvalueisaninputintotheN2Oequationsformanurestoredortreated.
TheDairyGEMModelprovidesdailyestimates;userscanrefertothatmodelforamorein‐depthanalysisoftheiremissions.
5.3.1.2 RationaleforSelectedMethodforEstimatingEmissionsfromDairyProductionSystems
Thereareavarietyofmethodsandmodelsavailabletoestimateemissionsfromdairyproductionsystems,rangingfromsimplecarbonfootprintmodelstohighlycomplexprocess‐basedmodelsforthedeterminationofNH3andGHGemissions.TheIPCCTier1methodologyprovidesasimplisticmethodusedforcountryinventorypurposes.Whenadditionaldataareavailable,thereareaseriesofequationsthatcanbeusedtodevelopIPCCTier2estimates.Thedatausedfortheseestimatesaretypicallyeasilyobtainablefromtheproductionfacilityoravailableinalookuptable.Whilethesemethodsprovideestimatesforemissionsthatmaybesuitableforaroughdeterminationofemissionsinventories,theyareinsomecasesbasedonverylimiteddataandmaynotbeveryrepresentativeofemissionsatthefarmlevel.Thedevelopmentofprocess‐basedmodelshasprovidedawaytoobtainamoredetailedanalysisofemissionsatthefarmscale.
Awidevarietyofmodelsapplicabletodairyproductionfacilitieswereidentifiedandevaluated,including:CarbonAccountingforLandManagers;ClimateFriendlyFoodCarbonCalculator;CoolFarmTool;CPLAN;DairyGEM;DairyWise;FarmingEnterpriseGHGCalculator;FarmGHG;Holos;IntegratedFarmSystemModel(IFSM);ManureAndNutrientReductionEstimator(MANURE);ManureDeNitrification‐DeComposition(ManureDNDC);OVERSEER;andSIMSDairy.
ThesemodelswereevaluatedtodeterminetheirsuitabilityforusetodetermineemissionsestimatesfordairyproductionfacilitiesintheUnitedStates.ElevencriteriawereusedtoidentifymodelsthatcouldbeusedtoestimateCH4fromentericCH4productionandCH4,N2O,andNH3fromanimalhousingsystems.Twoofthecriteriawereconsideredcritical:themodelhadtoberelevanttoU.S.climateanddairyproductionsystemsandithadtobepublicallyavailable.Ifthemodelsmetthesetwocriteriatheywerefurtherrankedbasedontheremainingninecriteria.Fourofthemodelsconsideredmetthecriticalcriteria:DairyGEM,IFSM,CoolFarmTool,andMANURE.AlthoughDairyGEMisasubsetofIFSM,itwasincludedseparatelybecauseDairyGEMonly
Equation5‐9:TotalNitrogenEnteringManureStorageandTreatment
% /
Where:
TNstorage =Totalnitrogenenteringmanurestorage(kgNday‐1)
N =Numberofheadoflivestockspecies(animal)
Nex =Totalnitrogenexcretionperanimalperday(gNanimal‐1day‐1)
%NH3loss =PercentofNexlostasNH3inanimalhousing‐seeTable5‐8
=Conversionofgramstokilograms
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-44
estimatesemissionsfromtheanimalhousingandmanurestoragearea.Therefore,itislesscumbersometouseandrequiresfewerinputs.
Outofthesefourmodels,DairyGEMhadthemostflexibilityfordescribingtheproductionsystemandmetallofthespecifiedcriteria.Inaddition,thismodelimplementsemissionestimatemethodologiesthatareadvancedbeyondtheIPCCTier2determinations.ItmodelsCH4emissionsfromentericfermentationandmanuremanagementandthenitrogenbalanceassociatedwithnitrogenexcretedinmanure.TheunderlyingmethodsintheDairyGEMmodelarerecommendedfordeterminingCH4emissionsfromentericfermentationandhousingsystemsfordairycattle(seefurtherdiscussioninAppendix5‐E,Table5‐E‐1,andsubsequentrelevanttext).Theestimatesgeneratedfromthismodelcouldthenbemodifiedtoaccountformitigationstrategiesthatcouldaltertheemissionscurrentlybeinggeneratedon‐farm.Somemitigationstrategiesarealreadyembeddedinthemodel,suchasalternativefeeding,manurehandling/storage,andtheuseofbovinesomatotropin,whileotherscouldbeusedbydevelopingatablewithmodifiersbasedonliteraturevaluestodeterminehowon‐farmemissionscouldchangewiththeimplementationofthesestrategies.ForN2Oemissions,anitrogenbalanceapproach(basedontheconceptsinDairyGEM)usingnitrogenexcretionequationsfromASABEStandardD384.2isrecommended.TheuseoftheASABEequationstakesintoaccounttheimpactofdietarychangesonnitrogenexcretion.
5.3.2 EntericFermentationandHousingEmissionsfromBeefProductionSystems
Becauseofdifferencesinthediets,animalphysiologicalstateandage,andmanurehandling,theproportionsandsourcesofGHGsdifferamongthecow‐calf,stocker,andfinishingsegmentsofthebeefcattleindustry.AprimarysourceofGHGsfromthebeefcattleindustryisentericCH4,producedprimarilyintherumen,althoughsomeCH4isalsoproducedinthelowergut.Inaddition,CH4andN2Omaybeproducedfromfecesandurineonpasturesandfeedlotpensurfaces.Emissions
Model Evaluation Criteria for Dairy Production Systems
1. Themodelisbasedonwell‐established,scientificallysoundrelationshipsamongfarmmanagementinputs,emissionsoutputs(process‐based/mass‐balancemodelpreferable).
2. ThemodelisrelevanttoU.S.climateanddairyproductionsystems.3. ThemodelcanestimateCH4,andN2O,andNH3emissionsfromdairyhousingsystems
(includingentericCH4production).4. Thereisflexibilityinthemodeltodescribetheproductionsystem(animals,feed,
housing,andin‐housemanuremanagement).5. Themodeliseasytouseandisdesignedtouseeasilyobtainablefarminformationto
determineemissionsestimates.6. ModelemissionestimatesforbothentericCH4productionandemissionsassociated
withcattlehousingareeasilycaptured.7. Themodelincludessomemitigationstrategiesforreducingemissionsandproduces
realisticchangesinemissionsvalueswhenthesechangesaremadewithintheproductionsystem.
8. Thereistransparencyinthemodelcalculations,andtechnicalguidelinesareavailabletoelaboratethemethodologiesusedtoobtaintheemissionsestimates.
9. Themodelhasbeentested/validatedwithon‐farmdata.10. Themodelworksreliably(littletonoerrorsorprogramcrashes).11. Themodelispubliclyavailableandaccessible.
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-45
fromhousingandmanurehandling(priortoenteringamanagementsystem)arediscussed,andequationsforstockpiledmanure(Section5.4)canbeappliedforemissionestimation.
Phetteplaceetal.(2001)estimatedGHGemissionsfromsimulatedbeefanddairy4systemsintheUnitedStatesusingmodificationsoftheIPCC(1997)methodology.Thesystemswerecomprisedofabaseherdofmaturecowspluscalvesandreplacements,stockercalves,afeedlot,andadairywith100lactatingcows.Theyalsoevaluatedemissionsfromcalvesthatwentthroughtheentirecow‐calf,stockerandfeedlotsystem(cow‐calftofeedlot).Greenhousegasemissionshead‐1(CO2‐eq)fromPhetteplaceetal.(2001)arepresentedinTable5‐10(withtheexceptionofthedairyherd).
Table5‐10:SimulatedGHGEmissionsforRuminantSystems(kgCO2‐eq/head/year)
Item Cow‐calf Stocker Feedlot Cow‐calfThroughFeedlot
DietaryTDN,% 62 57 88 62GHG(kgCO2‐eq/head/year)
EntericCH4 1,140 1,725 743 1,167ManureCH4 34 48 12 34TotalCH4 1,175 1,773 755 1,201N2O 1,487 1,721 1,294 1,490CO2 127 380 1,245 252
TotalCO2‐eq 2,788 3,874 3,294 2,944Source:Phetteplaceetal.(2001).
Elsewhere,Beaucheminetal.(2010)usedtheHolosmodel(Littleetal.,2008)toconductalife‐cycleassessmentofbeefproductioninwesternCanada.OftotalCO2‐eq,63percentwasfromentericCH4.5TheseareverysimilartovaluesreportedbytheU.S.DepartmentofAgriculture(2004b).Sixty‐onepercentofCO2‐eqemissionswerefromthecow‐calfherd,19percentwerefromreplacementheifers,eightpercentwerefrombackgroundingoperations,and12percentwerefromfeedlots.SeventyninepercentofentericCH4losseswerefromthecowherd,threepercentfrombulls,twopercentfromcalves,sevenpercentfrombackgrounders,andninepercentfromfeedlots.N2Ocontributions(CO2‐eq)asapercentoftotalGHGemissionswereasfollows:feedlotmanure–twopercent,feedlotsoil–twopercent,cow‐calfherdsoil–twopercent,andcow‐calfherdmanure–20percent.
Cow‐CalfandBullsThereisnoevidencethatanybreedofbeefcowproduceslessentericCH4thananother.Thereareafewreportssuggestingthatefficientcattle(thoseselectedforfeedefficiencyorresidualfeedintake(RFI))mayproducelessentericCH4(Nkrumahetal.,2006;Hegartyetal.,2007).However,FreetlyandBrown‐Brandl(2013)reportedthatcattlewithgreaterfeedefficiencyactuallyproducedmoreCH4;thusraisingsomequestionsaboutthegeneticfactorsassociatedwithfeedefficiencyandCH4emissions.Itisunclearwhetherthechangesobservedarearesultofalteredfeedintakeorareassociatedwithachangeinalteredruminalmicrobialpopulation.Additionally,recentinformationindicatesthatthereisaninteractionbetweendietqualityandfeedefficiencyonentericCH4emissions,whereefficientcowsproducelessCH4whengrazinghigh‐qualitypasturebutnotwhengrazingpoor‐qualityforage(Jonesetal.,2011).Residualfeedintakeismoderatelyheritable—(0.28to0.58;Mooreetal.,2009),thusitmightbepossibletogeneticallyselectforanimalswithlowerentericCH4production.AnexaminationofthevalueforselectionforlowentericCH4productionhasbeenconductedwithsheepinNewZealandandAustralia.Simulationsusingpublisheddata
4DiscussionofemissionsfromdairyproductionsystemscanbefoundinSection5.3.1.55%ofemissionswerefrommanureCH4,23%frommanureN2O,4%fromsoilN2O,and5%fromenergyCO2.
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indicatethatwithoutaccuratefeedintakeinformationandamethodbywhichmanyanimalscanbescreenedforCH4emissions,selectionforlowerentericCH4productionisnotlikelytobeeconomicallyviable(Cottleetal.,2011).
MeasurementofentericCH4fromgrazingcattlehasbeenconductedprimarilyfromanimalsgrazingimprovedpasturesusingmicrometeorologicalmethodsandtracertechniques.Lassey(2007)summarizedmuchoftheCH4emissionsdatathathadbeencollectedusingtheSF6tracertechnique.Intakewaseithercalculatedfromarequirementsmodelorfromuseofmarkers(Cr2O3orYb2O3).Estimatedforagedigestibility(invitro)rangedfrom48.7to83percent,whichresultedinestimatedCH4conversionfactors[i.e.,entericCH4asapercentageofgrossenergyintake(GEI)]rangingfrom3.7to9.5percent.ThemeanYmfromallofthestudieswas6.25andagreesreasonablywellwiththatusedbyIPCC(2006)forcattleonpasture.Methaneemissionsfromcowsgrazingimprovedpasture,Kentuckyfescue,andBermudagrassinthesouthernUnitedStateswerereportedbyPavao‐Zuckermanetal.(1999)andDeRamusetal.(2003).InbothofthesestudiessignificantreductionsinentericCH4unit‐1ofanimalweightgainresultedfromtheimplementationofbestmanagementpracticesdesignedtoimprovepasturequality.
Entericemissionsestimatescanbemadeusingmicrometeorologicalmethodsandtracertechniques.OnereportinwhichCH4emissionsweremeasuredfrombeefcowsgrazingnativerangeinOctoberandMayillustratedalargevariationinentericemissions.InOctober,whencowswerelosingBW,theyproduced87gCH4headdaily‐1,andonthesamepastureinMaytheyproduced252gCH4headdaily‐1(Olsonetal.,2000).Westbergetal.(2001)measuredCH4fromcowsgrazingthesamepastureacrossseasonsandfoundsimilarresults,withhigherCH4emissionsfromcowsgrazinglushspringgrowthandthelowestemissionsfromgrazingstockpiledfallpasture.ThesedifferencesareattributabletodifferencesinbothDMIandforagequality.Ingeneral,asforagequalityincreases,DMIalsoincreases.Some"rulesofthumb"forDMIonpastureincludethefollowing:
Poorqualitypasture‐DMI=1to1.75percentofbodyweight; Mediumqualityforage‐DMI=1.75to2.25percentofbodyweight; HighqualityforageDMI=2.25to3percentofbodyweight.
StockersEntericCH4emissionsofstockerswhilegrazinghavebeenmeasuredbyLaubachetal.(2008),Tomkinsetal.(2011),McGinnetal.(2011),andBoadietal.(2002),usingavarietyoftechniquesincludingtheSF6tracer,andseveralmicrometeorologicalapproaches.ThesamefactorsthataffectCH4emissionsfromgrazingbeefcowsareimportantinstockercattle.Thosefactorsareleveloffeedintake,digestibilityofforageconsumed,supplementation,andthechemicalcompositionoftheplantsconsumed.Entericemissionsestimatescanbemadeusingmicrometeorologicalmethodsor,tracertechniquesorcanbepredictedfromIPCCTier2methods(seeentericdiscussion).Criticalvariablesincludemeasurementsorestimationsoffeedintakeandfeedquality(chemicalcomposition).Manyoftheequationscurrentlyavailablemaynotaccuratelypredictmeasuredentericemissionsfromgrazingcattle(Tomkinsetal.,2011).
FeedlotMostestimatesofentericmethaneemissionfromfinishingbeefcattlearebasedonworkusinganimalsconfinedtorespirationchambers,althoughafewstudieshaveusedmicrometeorologicalmethodsinopenfeedlots.EntericCH4lossesfromfinishingbeefcattlenormallyrangefrom50to200Lhead‐1daily(JohnsonandJohnson,1995;McGinnetal.,2004;Beaucheminetal.,2008;Lohetal.,2008;Halesetal.,2012;2013;Halesetal.,2014;Toddetal.,2014a;Toddetal.,2014b).InmoststudiesintheU.S.,dietshavebeenbasedonDRCorSFC;whereasmoststudiesinCanadathedietsarebasedonbarley.TheIPCCTier2(2006)entericCH4conversionfactor(Ym)forfeedlotcattleis
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-47
3±1percentofGEI.TherearefewstudiesthathavemeasuredemissionsofCH4andN2Ofromfeedlotpensurfacesandrunoffcontrolstructures.Theprimaryfactorsthatcontrolentericmethaneemissionsinfeedlotcattlearefeedintake,graintype,grainprocessingmethod,dietaryroughageconcentrationandcharacteristics,anddietaryfatconcentration.
5.3.2.1 MethodforEstimatingEmissionsfromBeefProductionSystems
aCalculatedusingEqn10.3inIPCC(2006)basedonbodyweight(“BW”).bCalculatedusingEqn10.4inIPCC(2006)basedonNEaandfeedingsituation.cCalculatedusingEqn10.8inIPCC(2006)basedonmilkproduction(“milk”)andmilkfat(“fat”).dCalculatedusingEqn10.11inIPCC(2006)basedoninformationondailyhoursofwork(“work”).eCalculatedusingEqn10.13inIPCC(2006)basedonNEmandpregnancystatus.fCalculatedusingEqn10.14inIPCC(2006)basedonDE.gCalculatedusingEqn10.13inIPCC(2006)basedonbodyweight,matureweight(“MW”),anddailyweightgain(“WG”).hCalculatedusingEqn10.15inIPCC(2006)basedonDE.
MethodforEstimatingCH4EmissionsfromEntericFermentationinBeefCattle
IPCCTier2approach,withsomeadjustmentfactors,basedondiet,animalweight,pregnancy/lactation,activity(IPCC,2006).
Datasourcesareuserinputsondietaryintake,lactationandpregnancyrates,animalweight,housing,andtheFeedstuffsCompositionTable(Ewan,1989;Preston,2013).
Althoughtheequationsutilizedarethesameasexistinginventorymethods,themethodtakesintoaccountalargedatabaseoffeedtypes(foundinAppendix5‐B,FeedstuffCompositionTable),aswellasreportingatthemonthly,ratherthanannual,temporalscale.
Equation5‐10:IPCCTier2EquationforCalculatingGrossEnergyRequirementsforBeefCattle
GE
NE NE NE NE NEREM
NEREG
DE%100
Where:GE =Grossenergy(MJday‐1)
NEm =Netenergyrequiredbytheanimalformaintenance(MJday‐1)a
NEa =Netenergyforanimalactivity(MJday‐1)b
NEl =Netenergyforlactation(MJday‐1)c
NEwork=Netenergyforwork(MJday‐1)d
NEp =Netenergyrequiredforpregnancy(MJday‐1)e
REM =Ratioofnetenergyavailableinadietformaintenancetodigestibleenergyconsumedf
NEg =Netenergyneededforgrowth(MJday‐1)g
REG =Ratioofnetenergyavailableforgrowthinadiettodigestibleenergyconsumedh
DE =Digestibleenergyexpressedasapercentofgrossenergy(%)
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TheDEultimatelyusedintheIPCCTier2equation(inEquation5‐11)willbeweightedbasedonportionoftotalfeedintakefromaparticularfeedtype.TheDEdataforparticularfeedstuffscanbefoundinAppendix5‐B.TherecommendedYmforbeefreplacementheifers,steerstockers,heiferstockers,beefcows,andbullsis6.5percentforallregionsofthecountry.Forfeedlotcattle,theIPCC(2006)Ymof3percentisadjustedbasedondiets.AllfeedlotcattleinitiallystartwithabaselineYmofthreepercent(IPCC,2006).ThecorrectionfactorstoYmforfeedlotcattlefordifferentscenariosareprovidedbelow(seeAppendix5‐Aforadditionaldetails).TheYmusedforcalculatingemissionsforthesecattleismodifiedbasedonanimaldiets,asindicatedinTable5‐11.
Table5‐11:DeterminationofAdjustedMethaneConversionFactor(Ym)forFeedlotCattle
Variable Ym(asa%ofGEI)BaselineYm(IPCC,2006) 3%Ionophoreindiet(Tedeschietal.,2003;Guanetal.,2006): Yes Nochange
No IncreaseYmby4%(Ym=3%x1.04=3.12%ofGEI)
FatContent(ZinnandShen,1996;Beaucheminetal.,2008;Martinetal.,2010)(Foreachpercentofaddedfat(assupplementalfatorinbyproductssuchasdistillersgrainthatcontainabout10percentfat),decreasebyfourpercenttoamaximumofa16percentdecrease)
1%supplementalfatDecreaseYmby4%
(Ym=3%x0.96=2.88%)
2%supplementalfatDecreaseYmby8%
(Ym=3%x0.92=2.76%)
Fourorhigheraddedfatcontent DecreaseYmby16%(Ym=3%x0.84=2.52%)
GrainType(BeaucheminandMcGinn,2005;Archibequeetal.,2006;Halesetal.,2012): Graininanimaldietissteamflaked(SF)orhighmoisture(HM) NoChange
Graininanimaldietisunprocessed(UP)ordryrolled(DR)IncreaseYm20%
(Ym=3%x1.2=3.6%)
GrainindietisbarleyratherthancornorsorghumIncreaseYm30%
(Ym=3%x1.3=3.9)GrainConcentration(seeAppendix5‐A fordetailsandreferences): Dietcontainsmorethan60percentgrain NoChange
Dietcontains45to60percentgrain IncreaseYm10%(Ym=3%x1.1=3.3%)
Dietcontainslessthan45percentgrainIncreaseYm40%
(Ym=3%x1.40=4.2%)
Equation5‐11:IPCCTier2EquationforCalculatingEntericCH4 EmissionsfromBeefCattle
/.
Where:
DayEmit =Emissionfactor(kgCH4head‐1day‐1)
GE =Grossenergyintake(MJhead‐1day‐1)
Ym =CH4conversionfactor,whichisthefractionofGEinfeedconvertedtoCH4(%)
55.65 =Afactorfortheenergycontentofmethane(MJkgCH4‐1)
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EmissionsfromFeedlotPenSurfacesTherearefew,ifany,studiesthathavemeasuredCH4orN2Oemissionsfrombeefcattlefeedlotpensurfacesandretentionponds.ThestudyofToddetal.(2014a;2014b)suggeststhereislittleCH4productionfromfeedlotpensurfaces.TheuseoftheIPCC(2006)methodologiesisrecommendedtoestimateemissionsfromfeedlotpensandretentionponds.
InordertoestimateCH4emissionsfrombeeffeedlotpensurfaces,thequantityofvolatilesolidsexcretedisfirstestimated.ThesecanbeestimatedbylabtestingsamplesfromthefacilityorusingvaluesfromtheASABEStandardD384.2(ASABE,2005).6CH4emissionsfromthepensurfacecanbeestimatedusingtheIPCC(2006)Tier2approachasoutlinedinsection5.4.1.2.Forcattlefeedlots,amaximumCH4productioncapacity(B0)of0.33m3/kgvolatilesolidsisassumed(Table5‐19)andtheCH4conversionfactorforpensurfacesrangesfrom1to2percentofB0,dependinguponenvironmentaltemperature(Table5‐20).Oncemanureisscrapedfromthepensandremoved,themethodsdescribedinsection5.4.1canbeusedtoestimateCH4emissionfrommanurethatiscompostedorstoredinstockpiles.
InordertoestimateN2Oemissionsfromthepensurfacesofbeeffeedlotsthequantityofnitrogenexcretedontothepensurfacemustbeknown.ThiscanbeestimatedusingEquation5‐12fromtheASABEStandardD384.2.Forabeeffeedlot,adefaultvalueof0.069kgofNkgdrymanure‐1canbeusedifNexisnotcalculated.
6Volatilesolidsvaluescanbeestimatedfromequations(1)or(2)insection4.3.1ofASABED384.2.DefaultvolatilesolidsvaluesarealsopresentedinTable5‐32ofthisdocument.
Methodfor Estimating Beef Cattle GHG Emissions from Housing
Methane
TheIPCC(2006)Tier2methodcanbeusedtoestimateCH4emissionswhenmanureisallowedtoaccumulateonfeedlotpensurfacesasdescribedbelow.
NitrousOxide
NitrogenexcretedestimatedusingequationsprovidedinASABED384.2. IPCC(2006)Tier2approachforN2Oemissionsfrommanureinhousing.
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5-50
SomeofthenitrogenexcretedisvolatilizedasNH3,hence,theestimationofNH3lossesisnecessarytoestimateN2Oemissionsusinganitrogenbalanceapproach.TheNH3lostfrommanureinhousingisestimatedasafractionofNex.KoelschandStowell(2005)provideestimatesonthetypicalNH3lossfromdifferenthousingfacilitiesasafractionofNex(seeTable5‐12).Arangeofvalueshasbeenprovidedforeachfacilitytype;thelowervaluesshouldbeusedduringthewinter,thehighervaluesshouldbeusedduringthesummer,andintermediatevaluesshouldbeusedforthespringandautumn.
Table5‐12:TypicalAmmoniaLossesfromBeefCattleHousingFacilitiesExpressedasaPercentofNex
FacilityDescription %Loss FacilityDescription %Loss
Opendirtlots(cool,humidregion) 30–45 Roofedfacility(beddedpack) 20‐40
Opendirtlots(hot,aridregion) 40–60Roofedfacility(deeppitunderfloor,includingstorageloss)
30‐40
Source:KoelshandStowell(2005).
AnalternativeapproachistousetheequationofToddetal.(2013)whichcalculatesmonthlyfeedlotNH3emissionsasafunctionofdietarycrudeproteinandaveragemonthlytemperature(Equation5‐13).
Equation5‐12:ASABEApproachforEstimatingNitrogenExcretionfromBeefCattle
..
..
.
.
.
Where:
Nex =Totalnitrogenexcretionperanimalperday(gNanimal‐1day‐1)
DMIx=DryMatterIntakeforrationx(kgdryfeedanimal‐1day‐1)
CCP‐x =Concentrationofcrudeproteinoftotalration(gcrudeproteingdryfeed‐1)
DOF =Daysonfeedforanindividualration(days)
BW =Livebodyweightatfinishoffeedingperiod(kg)
BW =Livebodyweightatthestartoffeedingperiod(kg)
DOFT=Totaldaysonfeedfromstarttofinishoffeedingperiods(days)
SRW =Standardreferenceweightforexpectedfinalbodyfat(kg)
x =Rationnumber
n =Totalnumberofrationsfed
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5-51
N2OemissionsarecalculatedusingtheIPCC(2006)Tier2methodanddry‐lotemissionfactorsdescribedinEquation5‐8andTable5‐9.ThequantityofnitrogenthatleavesthefeedlotpensinmanurecanthenbecalculatedusingEquation5‐9.N2O‐NlossesfrommanurecollectedandremovedfromthepenscanbedeterminedfrommanurenitrogenusingEquation5‐27andEquation5‐29andtheemissionfactorsinTable5‐23andTable5‐25foundinSection5.4ManureManagement.NH3lossesfrommanurenitrogenremovedfromthepenscanbecalculatedasdescribedinAppendix5‐C.1and5‐C.3.
5.3.2.2 RationaleforSelectedMethodforEstimatingEmissionsfromBeefProductionSystems
Cow‐Calf,Bulls,andStockersThemostappropriatepredictionsavailableforentityscaleestimationareIPCCTier2methodsforgrazingcattle.Criticalvariablesthatareimportanttodefineinordertogeneratepredictionmethodsincludemeasurementsorestimationsoffeedintakeandfeedquality(chemicalcomposition)forpastureorrangelands.Iftheintakeisnotknown,intakepredictionequations/modelssuchasNRC(2000)canbeused.TheNRC(2000)providesanequationforthecalculationofDMIforgrazingbeefcowsandforstockercattle:NEmintake=SBW0.75*(0.04997*NEm2+0.04631)whereNEmistheestimatedMcalkg‐1ofthepasture,andSBWistheaverageshrunkbodyweightfortheperiodofgrazing(kg).TherequirementforknowledgeoftheNEmconcentrationofthepasturemaylimittheusefulnessofthepredictioninsomesituations.
Insituationsinwhichtheherdishousedinadry‐lotorbarnfacility,emissionfactorsforCH4andN2Oassociatedwithpensurfaces,manurestorage,andanimalmovement/manuredisturbancewouldbeappropriate.
FeedlotEllisetal.,(2009)reportedthatseveralequationsappearedtobegoodpredictorsofentericCH4lossesfromfeedlotcattlebasedonCanadianstudies.However,manyofthoseequationstendtogreatlyoverestimateentericlosseswhencomparedwithdatafromcattlefedatypicalsouthernplainsfinishingdiet(Halesetal.,2012;2013;Toddetal.,2014a;Toddetal.,2014b).AlthoughKebreabetal.(2008)reportedthatMOLLYandIPCCTier2(2006)gavepredictedvaluessimilartomeasuredvalueswithfeedlotcattle,therewasalargevariabilityinindividualanimalswitherrorsof75percentorgreater.Kebreabetal.(2008)notedtheaverageYm(MJentericCH4MJGEI‐1)forfeedlotcattlebasedonexperimentaldatawas3.88percentofGEI(range3.36to4.56),whichwashigherthantheIPCC(2006)valueof3.0percentandtherecentlyobtainedvalueswithtypicalfinishingdietsof2.85percent(Halesetal.,2012;2013).
Equation5‐13:MonthlyBeefFeedlotNH3 EmissionsasaFunctionofDietaryCrudeProteinandMonthlyTemperature
. .
Where:
NH3 =NH3emissionfromhousingperday(gNH3head‐1day‐1)
T =Averagemonthlytemperature(K)
CP =Dietarycrudeproteinasafractionofdrymatter(%)
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-52
Currently,IPCCTier2maybethemostusefulmethodologyforpredictionofentericemissionsfromfeedlotbeefcattle.Unfortunately,theTier2methoddoesnotallowforestimatingchangesinentericemissionsrelatedtochangesindietormanagement.
Therefore,amodifiedIPCC(2006)methodisrecommendedtoestimateentericCH4emissionsfrombeefcattlefedhighconcentratefinishingdiets.TheCH4conversionfactor(Ym)willbeadjustedbyfactorsintheanimals’dietsasdescribedinSection5.3.2.1.AbaselinescenariobasedontypicalU.S.beefcattlefeedingconditionsisestablished,andtheYmvaluesareadjustedbasedonpublishedresearch.Emissionvaluesaremodifiedusingcorrectionfactorsthatarebasedonchangesinanimalmanagementandfeedingconditionsfromthebaselinescenario.
5.3.3 EntericFermentationandHousingEmissionsfromSheep
GHGemissionsassociatedwithsheepproductionincludeentericCH4emissions,manureandbeddingemissions,andemissionsassociatedwithgrazingandmanureapplicationtoland.
TheNewZealandMinistryfortheEnvironment(2010)estimatedthatsheepyoungerthanayearofageemit5.1percentofGEIasentericCH4,andadultsheepemit6.3percentoftheirGEIasCH4.Theseemissionfactors,whencombinedwithpopulationestimates,resultinbaselineentericemissionsof11.60kgCH4head‐1year‐1.Sheeparealsoestimatedtodeposit15.9kgNhead‐1year‐1.
Lassey(2007)summarizedtheentericemissionsmeasurementsfromgrazingsheeptrialsfromNewZealandandAustraliainwhichtheSF6tracertechniquewasused.Foragecharacteristicsrangedfromlush(invitrodigestibilityestimateof82percent)topoorquality(called“dead,”withaninvitrodigestibilityof54percent).Intakewasmeasuredusingcompletefecalcollectionoramarker(n‐alkane).EntericCH4emissionsrangedfrom11.7gday‐1forsheepfedforageofhigherquality(6.9percentofGEI)to35.2gday‐1forsheepfedforageoflowerquality(6.3percentofGEI).Theaverageentericemissionswere5.39percentofGEI,or23.5gday‐1.Ingeneral,lowerforagequalityresultedinagreateramountofCH4emittedasaproportionoftheenergyintakethandidhigherforagequality.
NewZealandpasturesgrazedbysheephadelevatedN2Oemissions(7.4gN2O‐Nha‐1day‐1vs.3.4gN2O‐Nha‐1day‐1)comparedwithcontrol,butsignificantlylessthanthatobservedwhencattlegrazed(32.0gN2O‐Nha‐1day‐1)(Saggaretal.,2007).ThedatawereusedtoevaluatetheNZ‐DNDCmodel,aprocess‐basedNewZealandwholefarmmodel.ToourknowledgetherearenopublishedestimatesofGHGemissionfromsheepmanuresystems.
5.3.3.1 MethodforEstimatingEmissionsfromSheep
MethodforEstimatingEntericFermentationCH4 EmissionsfromSheep
Howdenequation(Howdenetal.,1994),basedondietaryDMI. TheequationfromHowdenetal.(1994)estimatesemissionsbasedsolelyonDMI;hence,
emissionfactorsnotutilized.
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-53
ThedrymatterdataforparticularfeedstuffscanbeobtainedfromAppendix5‐B.
Noemissionsestimationmethodshavebeenprovidedforhousingasmostsheeparekeptonpastureandminimalemissionsareexpected.
5.3.3.2 RationaleforSelectingMethodforEstimatingEmissionsfromSheep
Howdenetal.(1994)generatedanequationfromwhichtopredictCH4emissionsfromsheep.Equation5‐7resultedfromalinearextrapolationofDMItoemissions.IthassincebeenevaluatedandfoundtoberobustenoughtobetheequationusedintheAustralianNationalGreenhouseGasInventory.KleinandWright(2006)measuredCH4fromsheepinrespirationchambersandcomparedtheirresultstotheHowdenetal.(1994)equation.ActualCH4averaged1.1ghead‐1(SE±0.05)andpredictedCH4was1.1ghead‐1(SE±0.02).ApotentialconcernregardingtheHowdenequationisthatmuchofthedataincludedintheanalysiswasbasedontropicalforages.Nonetheless,whenintakedataareavailable,theHowdenequationpresentsthebestmethodbywhichtoestimatesheepentericemissions.Whenintakeisnotavailable,theIPCCTier2methodofestimationshouldbeused.EmissionsfromfeedlotsheepshouldusetheYmvaluesfromBlaxterandClapperton’soriginalpaper(1965)inwhichtheymeasuredCH4emissionsfromsheepwithrespirationcalorimetrychambers.Sheepfedhighlydigestibledietsatthreetimesmaintenanceproduced35percentlessCH4(kcal100Kkcaloffeedenergy‐1)thanthosefedsimilardietsatmaintenance;thus,areducedYmvalueiswarranted.TheequationisCH4=1.3+[0.112×(%digestibility/100)]+[MEintake/maintenanceMErequirement]×[2.37‐0.050×(%digestibility/100)].
5.3.4 EntericFermentationandHousingEmissionsfromSwineProductionSystems
SourcesofGHGemissionsincludeentericfermentation;manurestoredwithintheanimalhousing,whetheritisstoredasaliquidormixedwithbedding;emissionsthatoccurduringthetransportofmanuretoanexternalmanurestoragestructure;theoutsidemanurestoragestructure;emissionsthatoccurduringtransportofmanuretothefield;andemissionsfollowinglandapplicationofmanure.BecauseGHGmitigationhasnotbeenafocusofU.S.researchfortheswineindustrynorahighpriorityforswineproducers,dataarenotreadilyavailabletoidentifythemagnitudeofeachoftheabovepointsofemissionwithinafarm.However,emissionsofCH4areexpectedtooccurprimarilyduringmanurestorage,andemissionsofN2Oareexpectedtopredominatefollowinglandapplicationofmanure.7Oftenmanureisstoredunderneaththepighousinginadeeppit.Forthisreason,emissionsdiscussioninthissectionincludesin‐housemanurestorageandcomparisonofin‐housemanurestoragesystemswithsystemsthatstoremanureexternally.Becauseswinefeedsaredry,emissionsofGHGfromfeedstorageareasarebelievedtobenegligible.
7GreenhousegasemissionsresultingfollowinglandapplicationareaddressedseparatelyinthesectionsonChapter3:CroplandsandGrazingLands.
Equation5‐14:EquationforEntericFermentationEmissionsfromSheep(Howdenetal.,1994)
. .
Where:
CH4 =Methaneemissions(kgCH4head‐1day‐1)
Intake =DryMatterIntake(kghead‐1day‐1)
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5-54
Greenhousegasemissiondatafromswinefacilitiesissomewhatlimited.Liuetal.(2011a)reportedthatgrow/finishpigsemitted42to79mgCH4kgBW‐1dailyfromchamberswherepigswerehousedwithmanure.DailyemissionsofN2Orangedfrom11.4to12.4mgN2OkgBW‐1(Lietal.,2011).ThesevaluesaresomewhathigherthandatausedbyVergeetal.(2009)incalculatingGHGemissionsfromCanadianporkproduction(43mgCH4kgBW‐1and4mgN2OkgBW‐1).Philippeetal.(2007)observedGHGemissionsintherangereportedbyLietal.(2011)thoughtheirobservationswereinEuropeandeeplitterandslattedfloorsystems.Thereportedgaseousemissionsfrompigsraisedontheslattedfloorandonthedeeplitterwere,respectively,0.54and1.11gpig‐1day‐1forN2O,and16.3and16.0gpig‐1day‐1forCH4.
Liuetal.(2011a)conductedameta‐analysistoidentifyfactorsthatcontributetoGHGemissionsfromswineproduction.Findings,showninTable5‐13,illustratethattypeofemissionsource(swinebuildingsormanurestoragefacilities)wasnotsignificantforCH4andN2Oemissions.Swinecategory(stageofproduction)andgeographiclocationwassignificantforbothoftheGHGgases.Neithertemperaturenorsizeofoperationwassignificantintheoverallanalysis.
Withinthemeta‐analysis,Liuetal.(2011a)foundthatswinebuildingswithstraw‐flowsystemsgeneratedthelowestCH4andN2Oemissionsofsystemscompared,whilepitsystemsgeneratedthehighestCH4emissions,andbeddingsystemsgeneratedthehighestN2Oemissions.Emissionsfromlagoonsandslurrystoragebasin/tankswerecompared;lagoonsgeneratedsignificantlyhigherN2Oemissionsthanslurrystoragebasin/tanks,whileCH4emissionswerenotdifferent.Straw‐basedbeddingresultedinnumericallyhigherCH4butlowerN2Oemissionswhencomparedwithsawdustorcornstalkbeddingsystems.Liuetal.(2011a)observedanincreasingtrendforCH4emissionsasmanureremovalfrequencydecreased(P=0.13).DeeppitsandpitsflushedusinglagooneffluentalsogeneratedrelativelyhighCH4emissions.ResultsforN2Oemissionsshowedveryhighuncertainties(P=0.49).DeeppitsandpitswithmanureremovedeverythreeorfourmonthshadrelativelyhigherN2Oemissions.Asummaryofotherfindingsfromthemeta‐analysisconductedbyLiuetal.(2011a)showedthatCH4emissionsfromslurrystoragefacilitieswithoutcoversweresignificantlyhigherthanfromthosewithcovers.
ThehighestCH4emissionswerefromfarrowingswine,andweresignificantlyhigherthanthosefromfinishingandnurseryswine.Comparedwithfarrowingswine,thegestatingswinehadsignificantlylowerCH4emissions.ThehighestN2Oemissionswerefromgestatingswineandweresignificantlyhigherthanthosefromfinishingswine.
NorthAmericanstudiesreportedsignificantlyhigherCH4emissionsfromswineoperationsthanEuropeanandAsianstudies(Liuetal.,2011a).Thisisprobablyduetothedifferentprevailingmanurehandlingsystemsanddifferentmanurehandlingpracticesindifferentregions.EmissionsofCH4fromlagoonsandmanurestoragefacilitiesincreasedwithincreasingtemperature.Forswinebuildings,temperaturewasnotasignificantfactor.
Table5‐13:PValuesofMainEffectsonGHGEmissionsfromSwineOperations
CauseofVariation CH4(n=76)N2O
(n=53)Emissionsource 0.94 0.93Swinecategory 0.05 <0.01Geographicregion 0.04 0.02Temperature 0.20 0.95Sizeofoperation 0.89 0.24Source:Liuetal.(2011a).
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5.3.4.1 MethodforEstimatingEmissionsfromSwineProductionSystems
MethaneEmissionsfromSwineHousingTheIPCC(2006)Tier2equationisusedtoestimateCH4emissionswhenmanureisallowedtoaccumulateinapitbelowtheanimalconfinement.TheestimationmethodisprovidedinEquation5‐4.ThemaximumCH4producingcapacityforswineisprovidedinTable5‐19.TheMCFsformanurestoredinadeeppitorfromswinebeddingisprovidedinTable5‐7.
NitrousOxideEmissionsfromSwineHousingToestimatenitrogenlossesfromswinehousing,theamountofnitrogenexcreted(Nex)foreachanimalclassesarefirstestimated.Equation5‐16describestherelationshipbetweennitrogenintake,retention,andexcretionforswine.Equation5‐17,Equation5‐18,Equation5‐19,andEquation5‐20providethemethodsforestimatingthenitrogenintakeandretentionforthedifferentswineclassesasrecommendedbytheASABE.
MethodforEstimatingEntericFermentationCH4 EmissionsfromSwine
IPCCTier1approach,usingU.S.emissionfactorof1.5kgCH4/head/year.(IPCC,2006). SoledatasourceistheIPCCTierIemissionfactorforswine.Userinputistotalnumber
ofhead,regardlessofclassorweight.
Equation5‐15:EquationforEntericFermentationEmissionsfromSwine(IPCC,2006)
.
Where:
CH4 =Methaneemissionsperday(kgCH4day‐1)
Population =Numberofswine(head)
0.00411 =DailyCH4emissionsfromeachanimal(kghead‐1day‐1)
Methodfor Estimating Swine GHG Emissions from Housing
Methane
TheIPCC(2006)Tier2methodisusedtoestimateCH4emissionswhenmanureisallowedtoaccumulatebelowtheanimalconfinementasdescribedbelow.
NitrousOxide
Nitrogenintake,retention,andexcretionestimatedusingequationsprovidedinASABED384.2.
IPCC(2006)Tier2approachforN2Ofrommanureinhousing.
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Equation5‐16:ASABEApproachforEstimatingNitrogenExcretionfromSwine
Where:
Nex =Totalnitrogenexcretionperanimal(ganimal‐1)
Nintake =Nitrogenintakeperfinishedanimal(ganimal‐1)
Nretention =Nitrogenretainedperfinishedanimal(ganimal‐1)
Equation5‐17:ASABEApproachforEstimatingNitrogenExcretionfromGrow‐FinishPigs
. .
..
Where:
Nintake =Nitrogenintakeperfinishedanimal(ganimal‐1)
Nretention =Nitrogenretainedperfinishedanimal(ganimal‐1)
ADFIG =Averagedailyfeedintakeoverfinishingperiod(gday‐1)
CCP =Concentrationofcrudeproteinoftotal(wet)ration(%)
DOFG =Daysonfeedtofinishanimal(grow‐finishphase)(days)
BW =Final(market)bodyweight(kg)
DPF =Averagedressingpercent(yield)atfinalweight(%)
BW =Initialbodyweight(kg)
FFLPF =Averagefat‐freeleanpercentageatfinalweight(%)
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aRecommendedvaluesare:350gday‐1forhighleangrowthcapacitypigs;325gday‐1forhigh‐moderateleangrowthcapacitypigs;and300gday‐1formoderateleangrowthcapacitypigs.
aAssumedtobe115days.bRecommendedvaluefromASABEis19.205kg.
Equation5‐18:ASABEApproachforEstimatingNitrogenExcretionfromWeaningPigs
.
.
Where:
Nintake =Nitrogenintakeperfinishedanimal(ganimal‐1)
Nretention =Nitrogenretainedperfinishedanimal(ganimal‐1)
ADFIG =Averagedailyfeedintakeoverfinishingperiod(gday‐1)
CCP =Concentrationofcrudeproteinoftotal(wet)ration(%)
DOFN =Daysonfeedtofinishanimal(nurseryphase)(days)
FFLGG =Averagefat‐freeleangainfrom20to120kg(gday‐1)a
BW =Finalbodyweightinnurseryphase(kg)
BW =Initialbodyweightinnurseryphase(kg)
Equation5‐19:ASABEApproachforEstimatingNitrogen ExcretionfromGestatingSows
. .
Where:
Nintake =Nitrogenintakeperfinishedanimal(ganimal‐1)
Nretention =Nitrogenretainedperfinishedanimal(ganimal‐1)
ADFIS =Averagedailyfeedintakeduringgestation(gday‐1)
CCP =Concentrationofcrudeprotein(%)
GL =Gestationperiodlength(days)a
GLTG =Gestationleantissuegain(kg)b
LITTER =Numberofpigsinlitter(head)
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aRecommendedvaluefromASABEis‐4.20kg.
SomeofthenitrogenexcretedisvolatilizedasNH3,hence,theestimationofNH3lossesisnecessarytoestimateN2Oemissionsusinganitrogenbalanceapproach.TheNH3lostfrommanureinhousingisestimatedasafractionofNexaccordingtotherangesprovidedinTable5‐14.Arangeofvalueshasbeenprovidedforeachfacilitytype;thelowervaluesshouldbeusedduringthewinter,thehighervaluesshouldbeusedduringthesummer,andintermediatevaluesshouldbeusedforthespringandautumn.
Table5‐14:TypicalAmmoniaLossesfromSwineHousingFacilities(PercentofNex)
FacilityDescription %Loss FacilityDescription %LossRoofedfacility(flushedorscraped)Roofedfacility(dailyscrapeandhaul)
5‐15 Roofedfacility(beddedpack) 20‐40
Roofedfacility(shallowpitunderfloor) 10‐20Roofedfacility(deeppitunderfloor‐includesstorageloss) 30‐40
Source:KoelshandStowell(2005).
TheIPCC(2006)Tier2approachisusedforN2Oemissionsfrommanurestoredinhousing.TheestimationmethodisprovidedinEquation5‐8.TheN2OemissionfactorscanbefoundinTable5‐9.
TheremainingnitrogenexcretedthatisnotlostasN2OorvolatilizedasNH3inhousingthenentersmanurestorageandtreatment.Ifdataarenotavailabletotrackthenitrogenthatistransferredalongwiththemanuretomanurestorageandtreatment,thenitrogencanbeestimatedasdescribedinEquation5‐9.However,thisequationisoverestimatingthenitrogentransferringtomanurestorageandtreatmentassomenitrogenwillbelostinhousing.ThisremainingtotalnitrogenvalueisaninputintotheN2Oequationsformanurestoredortreated.
N2O‐NlossesfrommanurecollectedandremovedfromhousingcanbedeterminedfrommanurenitrogenusingequationsfromSection5.4ManureManagementfortheappropriatemanuremanagementsystem.NH3lossesfrommanurenitrogenremovedfromhousingcanbecalculatedusingthemethodologypresentedinAppendix5‐C.1and5‐C.3.
Equation5‐20:ASABEApproachforEstimatingNitrogenExcretionfromLactatingSows
. .
Where:
Nintake =Nitrogenintakeperfinishedanimal(ganimal‐1)
Nretention =Nitrogenretainedperfinishedanimal(ganimal‐1)
ADFILACT =Averagedailyfeedintakeduringlactation(gday‐1)
CCP =Concentrationofcrudeprotein(%)
LL =Lactationlength(daystoweaning)(days)
LLTG =Lactationleantissuegain(kg)a
LWEAN =Litterweightatweaning(kg)
LWBIRTH =Litterweightatbirth(kg)
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5.3.4.2 RationaleforSelectingMethodforEstimatingEmissionsfromSwine
Milesetal.(2006)suggestthatarobustmodelforentericandhousingemissionswouldincludefactorssuchashousemanagement,animalsizeandage,pH,andmanuremoisture.Duetothecurrentdatalimitations,anNH3andGHGestimationmodelshouldminimallyincludenumberofanimals,excretamoisturecontent,dietproteinandfibercontent,andexcretapH.Thechallengeisthatthesecriteriamaynotbereadilyavailabletothefarmmanager.
Liuetal.(2011a)comparedliteraturevalueswithIPCCvaluesandconcludedthatthevariationofthemeasuredCH4andN2OhousingemissionrateshasnotbeenadequatelycapturedbytheIPCCapproaches.ForCH4emissions,thedifferencesbetweentheIPCC‐estimatedemissionratesandmeasuredvaluesweresignificantlyinfluencedbytypeofemissionsource,geographicregion,andmeasurementmethods.LargerdifferencesbetweenestimatedandmeasuredCH4emissionrateswereobservedinNorthAmericanstudiesthaninEuropeanstudies.InNorthAmericanstudies,theresultsofmeta‐analysisindicatedanoverestimationbytheIPCCapproachesforCH4emissionsfromlagoons(pooledrelativedifference:‐33.9%;95%CI:‐66.8%to‐0.01%),andthediscrepancybetweentheIPCC‐estimatedemissionsandthemeasuredvaluesoccurredmainlyatlowertemperatures.InEuropeanstudies,theresultsindicatedanoverestimationoftheIPCCapproachesinswinebuildingswithpitsystems.ForN2Oemissionsfromswineoperations,anoverallunderestimationoftheIPCCapproacheswasobservedinEuropeanstudiesbutnotinNorthAmericanstudies.InEuropeanstudies,thepooledN2Oemissionfactorsforswinebuildingswithpitsystemswas1.6%(95%CI,0.6%to2.7%),whiletheIPCCdefaultemissionfactorforpitsystemsis0.2%.LargeruncertaintieswereobservedformeasuredN2Oemissionsfrombeddingsystemsandfromstrawflowsystems.
InordertoconsideranalternativetotheIPCCapproach,awidevarietyofmodelsapplicabletoswineproductionfacilitieswereidentifiedandevaluated,including1)CARLivestock,2)ManureAndNutrientReductionEstimator(MANURE),3)COOLFarmTool,4)CarbonAccountingforLand
Model Evaluation Criteria for SwineProduction Systems
1. Themodelisbasedonwell‐establishedscientificallysoundrelationshipsbetweenfarmmanagementinputsandemissionsoutputs(process‐basedmodelormass‐balancemodelpreferable);
2. ThemodelisrelevanttoU.S.climateandswineproductionsystems;3. ThemodelcanestimateCH4,N2O,andNH3emissionsfromentericfermentationand
swinehousingsystems;4. Thereisflexibilityinthemodeltodescribetheproductionsystem(animals,feed,
housing,andin‐housemanuremanagement);5. Themodeliseasytouseandisdesignedtouseeasilyobtainablefarminformationto
determineemissionsestimates;6. Themodelincludessomemitigationstrategiesforreducingemissions,andproduces
realisticchangesinemissionsvalueswhenthesechangesaremadewithintheproductionsystem;
7. Thereistransparencyinthemodelcalculations,andtechnicalguidelinesareavailabletoelaboratethemethodologiesusedtoobtaintheemissionsestimates;
8. Themodelhasbeentested/validatedwithon‐farmdata;9. Themodelworksreliably(littletonoerrorsorprogramcrashes);and10. Themodelispubliclyavailableandaccessible.
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Managers,5)FarmingEnterpriseGHGCalculator,6)CPLAN,and7)Holos.Thesemodelswereevaluatedby10criteria(seebox)todeterminetheirsuitabilityforuseindeterminingemissionsestimatesforswineproductionfacilitiesintheUnitedStates.Twoofthesecriteriawereconsideredtobecritical,inthatiftheywerenotmetbythemodel,theycouldnotbeconsideredforuse(i.e.,themodelhadtoberelevanttoU.S.climateandswineproductionsystemsandhadtobepubliclyavailable).
TheHolosmodelconsidereddiet(standard,lowcrudeprotein,orhigh‐digestibilityfeeds)andmanurehandlingoptions(anaerobicdigestion,coveredoruncoveredslurrystorage,deeppit,orsolidstorage).Inaddition,theHolosmodelprovidedanestimateofuncertaintyforthemodeloutput.TheMANUREmodel(WRI,2009)collectedthemostcomprehensivedataandallowedforeasycomparisonoftheimpactofchangesinmanurehandlinganduseonemissionsofNH3,N2O(directandindirect),andCH4.Ontheanimalside,MANUREbaseditscalculationssolelyonanimalnumbers;feedingwasnotconsidered.Theothermodelsconsidered,whilemeetingminimumcriteria,lackedanyimprovementsovertheIPCCapproach.Consequently,theIPCCmethodwasselected(i.e.,HolosutilizestheIPCCTier1approachforhousing)withnitrogenexcretionestimatedusingASABEequationsthataccountfordiets.
5.3.5 HousingEmissionsfromPoultryProductionSystems
MeatBirdsGreenhousegasemissionswithinthefarmboundaryofabroilerchickenfarmwilloriginatealmostexclusivelyfromtheanimalhousing,whichalsoservesasthestoragelocationformanure.Liuetal.(2011a)reportedthatfora20‐weekgrow‐outofturkeysonlitter,averagedailyN2Oemissionswere0.045g(kgbodyweight)‐1,anddailyCH4emissionswere0.08g(kgbodyweight)‐1.EmissionsourcesexternaltothehousingincludeGHGemissionsfromfarmvehicles.Ifahouseiscleanedordecaked(removalofthetop,crustedportionofthelitter)andstoredonthefarm,GHGandNH3productionandemissionscouldoccur;Appendix5‐CprovidesfurtherdiscussiononNH3emissionsfromhousing.Practicestodecakeandthetimingoflandapplicationofcakeandlittervaryfromsitetositeandmayormaynotincludefurthercomposting.
LayingHensGreenhousegasemissionswithinthefarmboundaryofaneggfarmmayoriginatefromthehousingorthemanurestoragelocation.EmissionsourcesexternaltothehousingincludeGHGemissionsfromfarmvehicles.Externaltothefarmitself,GHGemissionsresultfromlandapplicationoflitterorstockpilingofthelitterinfieldspriortolandapplication.
Layinghenhousingsystemswithoutlitterwouldlikelyexhibitgreateremissionsthanlittersystems,butcomparisonofestimatesaresparse.Layinghenhousestypicallystoreexcretainabasementormaymoveexcretaoutofthehousefrequently(dailyormoreoften);thiswouldrelocateemissionstoastorageshedratherthanchangethecumulativeemissionsunlesssomeformofprocessing(drying)tookplacepriortostorage.Lietal.(2010)reporteddailyCH4emissionsof39.3to45.4mghen‐1andN2Oemissionsof58.6mghen‐1(henbodyweightaverage=1.9kg)inabasement‐typesystem.Thiscomparestoalittersystemfora20‐weekgrow‐outofturkeyswhereaveragedailyN2Oemissionswere0.045gkg‐1bodyweightanddailyCH4emissionswere0.08gkg‐1bodyweight(Liuetal.,2011a).Basedonthecomparisonofthesetwostudies,differencesinGHGemissionsfromdrylittersystemsandwetter,stackedlayinghensystemswouldbeexpected.
ManagementpracticestoreducelittermoistureofferthemostpromiseforreducingemissionsofCH4andN2O.Quantitativeestimatesofhowemissionsvarywithlittermoisturearenotavailable,butwouldlikelyfollowsimilardynamicsassoilmoisturecontent.Reuseoflitteranddecaking
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proceduresmightalsobeusedasstrategiestoreduceemissionsinthefuture.However,dataarenotavailableatpresenttouseaspartofasystemsmodel.
Ammonia Emissions in Poultry Housing
Asmentionedearlier,ammoniaisnotagreenhousegas,however,ammoniaemissionsareestimatedaspartofthenitrogenbalanceapproach.Meatbirdsaretypicallyraisedinlittersystems.Littertemperature,pH,andmoisture,alongwiththeammoniumcontentandhouseventilationratearerecognizedasmajorfactorscontrollingNH3lossfrombroilerlitter(ElliotandCollins,1982;Carretal.,1990;Mooreetal.,2010).Thereareseasonalvariationsinemissions,withlossestendingtobegreaterinsummer(warmermonths)thaninwinter(Coufaletal.,2006).Birdage/sizecanaffectlittertemperature,whichmayinfluenceseasonaleffectsonemissions(Milesetal.,2008).Inaddition,theformationofcakeinthehousecanhavealargeimpactonemissions.Milesetal.(2008)reportedthatextremelycakedareasofthehousehadvirtuallynofluxesofNH3.AreasoflitterwhereanaerobicconditionsdevelopsuppressNH3formationandrelease(Carretal.,1990).Mooreetal.(2011)determinedthatNH3emissionsfrombroilerhousesaveraged37.5gbird‐1,or14.5gkgbirdmarketed‐1(50‐dayoldbirds).Thesameauthorsestimatedthatofthetotalnitrogenoutputfromtypicalbroilerhouses,approximately22percentcanbeassociatedwithNH3emissions,56percentfromharvestedbirds,and21percentfromlitterpluscake.Theadditionofaluminumsulfate(alum)atarateequivalenttofiveto10percentbyweight(alum/manure)reducesNH3emissionfrombroilerhousesby70percent(Mooreetal.,2000)andresultsinheaverbirds,betterfeedconversion,andlowermortality(Moore,2013).EmissionsofN2OandCH4aredependentuponlitterconditionsthatfavorananaerobicenvironment.LimiteddataareavailabledocumentinglittermoisturecontenteffectsonN2OandCH4emissions.Milesetal.(2011)demonstratedthatincrementalincreasesinlittermoisturecontentincreasedNH3volatilization.Similarly,CabreraandChiang(1994)demonstratedarangeinNH3volatilizationof32percentto139percentofinitialammoniumcontentaslitterwatercontentincreased.LittertemperatureisanotherfactorthatmayinfluenceGHGemissions.Milesetal.(2006)demonstratedthatlittertemperatureaffectedNH3flux,butthestudydidnotmeasureothergases.Milesetal.(2011)observedthatorganicbeddingmaterialsgeneratedtheleastamountofNH3attheoriginalmoisturecontentwhencomparedwiththeinorganicmaterials.Theinfluenceofbeddingmaterialatincreasedmoisturelevelswasnotclearacrossthetreatmentstested.ButthefindingssuggestthatchoiceofbeddingmaterialmayalsoinfluenceN2Oand/orCH4emissionsandcouldpotentiallybeusedasamitigationstrategy.
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5.3.5.1 MethodforEstimatingEmissionsfromPoultryProductionSystems
NitrousOxideandAmmoniaEmissionsfromPoultryHousingToestimatenitrogenlossesfromhousing,theamountofnitrogenexcreted(Nex)byeachanimalcategoryisfirstestimated.Equation5‐22andEquation5‐23aretheequationsrecommendedbytheAmericanSocietyofAgriculturalEngineers(ASABE)forestimatingNexfrombroilers,turkeys,ducks,andlayinghens.
Methodfor Estimating Emissions from Poultry Production Systems
Methane
IPCCTier1approach,utilizingbarncapacityandmanureCH4emissionsfactorsperpoultrytype.
IPCCemissionfactorforpoultryentericCH4productionis0.Emissionsfromhindgutfermentationaresmallandgenerallyconsideredpartofhousingemissions.
NitrousOxide
NitrogenexcretionestimatedusingequationsprovidedinASABED384.2. IPCC(2006)Tier2approachforN2Ofrommanureinhousing.
Equation5‐21:MethaneEmissionsfromPoultryHousing(IPCC,2006)
_
Where:
CH4 =Methaneemissionsperyear(kgCH4year‐1)
Rate =Manuremethaneemissions(kgCH4head‐1year‐1)
Barn_Capacity=Capacityofbarn(head)
Equation5‐22:ASABEApproachforEstimatingNitrogenExcretionfromBroilers,Turkeys,andDucks
.
Where:
Nex =Totalnitrogenexcretionperfinishedanimal(gN(finishedanimal)‐1)
FIx =Feedintakeperphase(gfeed(finishedanimal)‐1)
CCP‐X =Concentrationofcrudeproteinoftotalrationineachphase(gcrudeprotein(g(wet)feed)‐1)
NRF =Retentionfactorfornitrogen(fraction)
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aDefaulteggweightis60gforlightlayerstrainsand63gforheavylayerstrains.bDefaultfractionis0.80.
TheNH3lostfrommanureformeatandegg‐producingbirdsisestimatedasafractionofNex.KoelschandStowell(2005)provideestimatesonthetypicalNH3lossfromdifferenthousingfacilitiesasafractionofNex(seeTable5‐15).Arangeofvalueshasbeenprovidedforeachfacilitytype;thelowervaluesshouldbeusedduringthewinter,thehighervaluesshouldbeusedduringthesummer,andintermediatevaluesshouldbeusedforthespringandautumn.
Table5‐15:TypicalAmmoniaLossesfromPoultryHousingFacilities(PercentofNex)
FacilityDescriptionApplicableSpecies %Loss FacilityDescription
ApplicableSpecies %Loss
Roofedfacility(litter)Meat
producingbirds
25‐50Roofedfacility(stackedmanureunderfloor‐includesstorageloss)
Egg‐producingbirds
25‐50
Source:KoelshandStowell(2005).
N2O can also be lost from the excreted nitrogen. A quantitative method for estimating N2O emissions from solid manure is the IPCC Tier 2 approach, which is also used for the U.S. Greenhouse Gas Inventory (Equation 5-8). This estimation method is the same as the method present in the Temporary Stack and Long-Term Stockpile and the Composting sections (see sections 5.4.1 and 5.4.2 for more details). The N2O emission factors for poultry manure in housing is 0.001 (kg N2O-N/ kg N) for poultry manure with or without bedding IPCC (2006).
TheremainingnitrogenexcretedthatisnotvolatilizedasNH3orlostasN2Oinhousingthenentersmanurestorageandtreatment.Ifdataarenotavailabletotrackthenitrogenthatistransferredalongwiththemanuretomanurestorageandtreatment,thenitrogencanbeestimatedasdescribedinEquation5‐9.However,thisequationisoverestimatingthenitrogentransferringtomanurestorageandtreatmentassomenitrogenwillbelostinhousing.ThisremainingtotalnitrogenvalueisaninputintotheN2Oequationsformanurestoredortreated.
5.3.5.2 RationaleforSelectingMethodforEstimatingEmissionsfromPoultryProductionSystems
Milesetal.(2006)suggestthatarobustmodelwouldincludefactorssuchashousemanagement,birdsizeandage,cakemanagement,pH,andlittermoisture.Duetocurrentdatalimitations,anNH3andGHGestimationmodelshouldminimallyincludenumberofanimals,litter/excretamoisturecontent,dietaryproteinandfibercontent,andlitter/excretapH.Avarietyofmodelsapplicableto
Equation5‐23:ASABEApproachforEstimatingNitrogenExcretionfromLayingHens
..
Where:
Nex =Totalnitrogenexcretionperanimalperday(gNanimal‐1day‐1)
FI =Feedintake(gfeed(finishedanimal)‐1)
CCP =Concentrationofcrudeproteinoftotalration(gcrudeprotein(g(wet)feed)‐1)
Egg =Eggweighta(g)
Egg =Fractionofeggsproducedeachdayb(eggshen‐1day‐1)
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poultryproductionfacilitieswereidentifiedandevaluated,includingCarbonAccountingforLandManagers;CFFCarbonCalculator;CPLAN;and4)Holos.Thesemodelswereevaluatedwithrespectto10criteria(seebox)todeterminetheirsuitabilityforuseindeterminingemissionsestimatesforpoultryproductionfacilitiesintheUnitedStates.
Twoofthesecriteriawereconsideredtobecritical,inthatiftheywerenotmetbythemodel,theycouldnotbeconsideredforuse(i.e.,themodelhadtoberelevanttoU.S.climateandpoultryproductionsystemsandhadtobepubliclyavailable).TheHolosmodeldidconsiderwetordrymanurehandlingforlayinghenoperations.Forallpoultrytypes,theCarbonAccountingforLandManagersmodelrequestedinformationrelatedtoburningofmanureandtimebirdsspendinafree‐rangesystem.Thisinformationwasthenusedtocalculatethemassofmanureavailablefordirectandindirectemissions.Nomodelrequestedinformationondietorin‐houselittermanagementpractices.ForCH4emissions,onlytheHolosmodelprovidedanestimateofconfidenceofmodeloutput.SpecifictoestimatesofpoultrymanureCH4emissions,themodelhadanuncertaintyunder20percentforbroilers,turkeys,layersinwetmanurehandlingsystems,andlayersindrymanurehandlingsystems.Consequently,theIPCCmethodwasselected(i.e.,HolosutilizestheIPCCTier1approachforhousing).ForN2Oemissions,theIPCCTier2wasusedwithnitrogenexcretionestimatedusingASABEequationsthataccountfordiets.
5.3.6 EntericFermentationandHousingEmissionsfromOtherAnimals
AlthoughthemajorityofemissionsfromlivestockintheUnitedStatesarefromcattle,sheep,swine,andpoultry,emissionsfromotheranimalscanalsobeimportanttoconsider,particularlyattheentitylevel.Overall,populationsoftheanimalsdiscussedinthissection(goats,Americanbison,llamas,alpacas,andmanagedwildlife)aremuchfewerthanthoseoftheanimalsdiscussedinpriorsections.However,theavailabilityofresearchonemissionsfromtheseanimalsallowsustoexplorethematleastatanintroductorylevel.Attheentitylevel,populationsoftheseanimalsmaybesignificantenoughtowarrantcalculatingtheiremissions.ThisreportrecommendsmethodsforestimatingCH4emissionsfromgoatsandAmericanbison(Equation5‐24andEquation5‐25).
Model Evaluation Criteria for Poultry Production Systems
1. Themodelisbasedonwell‐establishedscientificallysoundrelationshipsbetweenfarmmanagementinputsandemissionsoutputs(process‐basedmodelormass‐balancemodelpreferable).
2. ThemodelisrelevanttoU.S.climateandproductionsystems.3. ThemodelcanestimateCH4,N2O,andNH3emissionsfrompoultryhousingsystems.4. Thereisflexibilityinthemodeltodescribetheproductionsystem(animals,feed,
housing,andin‐housemanuremanagement).5. Themodeliseasytouseandisdesignedtouseeasilyobtainablefarminformationto
determineemissionsestimates.6. Themodelincludessomemitigationstrategiesforreducingemissionsandproduces
realisticchangesinemissionsvalueswhenthesechangesaremadewithintheproductionsystem.
7. Thereistransparencyinthemodelcalculations,andtechnicalguidelinesareavailabletoelaboratethemethodologiesusedtoobtaintheemissionsestimates.
8. Themodelhasbeentested/validatedwithon‐farmdata.9. Themodelworksreliably(littletonoerrorsorprogramcrashes).10. Themodelispubliclyavailableandaccessible.
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5.3.6.1 Goats
EntericemissionsfromgoatproductionsystemswereestimatedbyU.S.EPA(U.S.EPA,2011)usingIPCC(2006)methodstobe16GgCH4(ofatotalof6,655Gg).EmissionsofmanureCH4andN2OfromgoatproductionweremadeusingIPCC(2006)methods.Goatswereassociatedwith1GgofmanureCH4(ofatotalof2,356Gg)andlessthan0.5GgofN2O.
TheimpactofdietonJapanesegoatentericCH4emissionswasmeasuredbyBhattaetal.(2007).Goatsfedarangeofdietsfrom100percentforageto80percentconcentrateproducedfrom16.4to22gCH4day‐1(5.0to8.2percentofGEI).
TheIPCC(2006)Tier1equation,presentedinEquation5‐24,forestimatingentericfermentationemissionsfromgoatsisthebestoptionforcalculatingemissionsattheentitylevel.
5.3.6.2 AmericanBison,Llamas,Alpacas,andManagedWildlife
Galbraithetal.(1998)measuredentericCH4fromgrowingbison(n=5),wapiti(n=5),andwhite‐taileddeer(n=8)fedalfalfapelletsinthewinter‐spring(February‐March)andspring(April‐May)usingrespirationcalorimetrychambers.Thebisonproducedanaverageof86.4gday‐1(6.6percentGEI),thewapiti,62.1gday‐1(5.2percentGEI),andthedeer23.6gday‐1CH4(3.3percentGEI).Usingadetailedmethodofcalculationtoestimatehistoricalbisonemissions,KelliherandClark(2010)estimatedthatgrazingbisonwouldproduce72kgCH4year‐1or197gCH4day‐1.Hristov(2012)estimatedpresentdaybisonproduce21gCH4(kgDMI)‐1day‐1,eatapproximately12.8kgDMday‐1,andproduce268gCH4day‐1.Thedifferencesbetweentheseestimatesaredifferencesinanimalweights,DMI,limitedmeasurementsofbisonemissions,andassumedCH4conversionfactors.TheU.S.EPAusesIPCCTier1methodologiestoestimatebisonemissions,andcurrentlyTier1isthebestoptiontoestimateentericemissions.
TheIPCC(2006)Tier1equationforestimatingentericfermentationemissionsfromAmericanbisonisbasedontheemissionfactorforbuffaloandhasbeenmodifiedasrecommendedbyIPCCtoaccountforaverageweightasseeninEquation5‐25.
Equation5‐24:Tier1EquationforCalculatingMethaneEmissionsfromGoats
Where:
CH4 =Methaneemissionsperday(kgCH4day‐1)
Pop =Populationofgoats(head)
EFG =Emissionfactorforgoats(0.0137kgCH4head‐1day‐1)
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TheNewZealandMinistryfortheEnvironment(2010)usesafactorof6.4percentofGEItopredictentericCH4emissionsfromfarmedreddeerandprojectsanemissionrateperyearof23.7kgCH4
head‐1year‐1.Deerarealsoestimatedtoexcrete31.0kgNhead‐1year‐1contributingtowardN2Oproduction.ThevaluesusedtomakethesecalculationsarefrommeasurementsofdeerCH4emissionsusingtheSF6tracermethod.Elk,white‐tailed,andmuledeerentericemissionswereestimatedbyHristov(2012)tobe86.4,16,17gCH4head‐1day‐1respectively.IPCCTier1istherecommendedmethodbywhichtheseemissionsshouldbeestimated.
Adultllamasfedoathayinastudydesignedtodefineenergyrequirementswerefoundtolose7.1percentofGEIasentericCH4(Carmeanetal.,1992).Pinares‐Patinoetal.(2003)comparedentericCH4emissionsmeasuredwithrespirationcalorimetrychambersfromalpacaandsheepfedalfalfadietsandfoundthealpacaproduced14.9gCH4day‐1(5.1percentofGEI)andthesheepproduced18.8gCH4day‐1(4.7percentofGEI).Whengrazingaperennialryegrass/whitecloverpasture,thealpacaproduced22.6gCH4day‐1(9.4percentGEI)comparedto31.1gCH4day‐1(7.5percentGEI)forsheep.TheauthorsattributethehighconversionofGEItoCH4fromthealpacatograzingselectivityonpasture;thealpacawereobservedtoselect“morestructuralplantparts.”
5.3.7 FactorsAffectingEntericFermentationEmissions
AnumberoffactorsmayinfluenceentericfermentationandresultingCH4emissions.Athoroughreviewofsuchfactorsisoutsidethescopeofthisdocument,butkeyfactorshavebeenreviewedbyothers(Montenyetal.;(2006),Beaucheminetal.;(2008),Eckardetal.;(2010),andMartinetal.;(2010))andarediscussedbrieflybelow.
Benchaaretal.(2001)usedtherumendigestionmodelofDijkstraetal.(1992),asmodifiedbyBenchaaretal.(1998),andtheCH4predictionsystemofBaldwin(1995)toestimatetheeffectsofdietarymodificationsontheentericCH4productionofa500kgdairycow.ThemodelpredictedentericCH4productionbasedonaruminalHbalance.Inputsintothemodelincludedthefollowing:dailyDMI;chemicalcompositionofthediet;solubilityanddegradabilityofproteinandstarchinthediet;degradationratesofprotein,starch,andNDF;ruminalvolume;andfractionalpassageratesofsolidsandliquidfractionsfromtherumen.ValuesmodifiedinthesimulationswereDMI,dietaryforage,concentrateratio,starchavailability(barleyvs.corn),stageofmaturityofforage,formofforage(hayorsilage),particlesizeofalfalfa,andammonizationofcerealstraw.ThemodeledeffectsofdietarychangesonentericCH4emissionsindietsfedtodairycowsarepresentedinTable5‐16.
Equation5‐25:Tier1EquationforCalculatingMethaneEmissionsfromAmericanBison
Where:
CH4 =Methaneemissionsperday(kgCH4head‐1day‐1)
Pop =PopulationofAmericanbison(head)
EFAB=EmissionfactorforAmericanbison(kgCH4head‐1day‐1)
EFABistheIPCCemissionfactorforbuffalo(0.15kgCH4head‐1day‐1),adjustedforAmericanbisonbasedontheratioofliveweightsofAmericanbison(513kg)tobuffalo(300kg)tothe0.75power.
.
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TherearemanyfactorsthataffectentericCH4emissionsbutthemostcriticalfactorsarethelevelofdrymatterintake,thecompositionofthediet,andthedigestibilityofthedrymatter,asillustratedinTable5‐16.
Table5‐16:SummaryofEffectsofVariousDietaryStrategiesonEntericCH4ProductioninDairyCowsusingModeledSimulations
StrategyCH4Variation(perunitofGEI)
CH4Variation(perunitofDE)
IncreasingDMI ‐9to‐23% ‐7to‐17%Increasingconcentrateproportioninthediet ‐31% ‐40%Switchingfromfibrousconcentratetostarchyconcentrate ‐24% ‐22%Increasedforagematurity +15% ‐15%Alfalfavs.timothyhay +28% ‐21%Methodofforagepreservation(ensiledvsdried) ‐32% ‐28%Increasedforageprocessing(smallerparticlesize) ‐21% ‐13%Ammoniatedtreatmentofpoorqualityforage(straw)a x5 x2Proteinsupplementationofpoorqualityforage(straw) ×3 ×1.5
Source:Benchaaretal.,(2001),Table12.aEffectsareduetosignificantincreaseinhaydigestibilitywithnochangeinDMintake.
DietaryFat:ManystudieshavedemonstratedthatsupplementalfatcandecreaseentericCH4emissionsinruminants.Inareviewofstudies,Beaucheminetal.(2008)notedthatentericCH4emissions(g[kgDMI]‐1)decreasedbyapproximately5.6percentforeachonepercentincreaseinfataddedtothediet.Inalargerreview,Martinetal.(2010)reportedadecreaseof3.8percent(g[kgDMI]‐1)witheachonepercentadditionoffat.Lovettetal.(2003)reportedthattotaldailyemissionsdecreasedfrom0.19to0.12kgCH4head‐1(reportedas260to172LCH4head‐1)(6.6and4.8percentofGEI)fromsteersfeddietscontaining0or350gofcoconutoil,respectively.Thiseffectwasconsistentregardlessofdietaryforageconcentration(65,40,and10percentofDM).
AlthoughaddedfatmayreduceentericCH4emissions,ruminantshavealowtolerancefordietaryfat.Thus,totalfatlevelinthedietmustbemaintainedbeloweightpercentofdietaryDM.Somesourcesoffatappeartohavesomeprotectionagainstbiohydrogenationbyruminalmicrobesandthusmaybebettertolerated(Corriganetal.,2009;VanderPoletal.,2009).
GrainSource,GrainProcessing,StarchAvailability:GrainsourceandgrainprocessingmethodcanalsoaffectentericCH4losses.Ingeneral,thegreatertheruminalstarchdigestibility,thelowertheentericCH4emissions.Atconstantenergyintake(2xmaintenance),Halesetal.(2012)reportedapproximately20percentlower(2.5vs.3.0percentofGEI)entericCH4emissionincattlefedtypicalhigh‐concentrate(75percentcorn)steamflakedcorn(SFC)basedfinishingdietsthaninsteersfeddry‐rolledcorn(DRC)basedfinishingdiets.BasedontherumenstoichiometryofWolin(1960),ZinnandBarajas(1997)estimatedthatCH4productionperunitofglucoseequivalentfermentedintherumenalsodecreasedwithmoreintensivegrainprocessing(i.e.,coarse,medium,orfineflakes).Similarresponseswerenotedwiththefeedingofhigh‐moisturecorncomparedwithDRC(Archibequeetal.,2006).Somewhatincontrast,BeaucheminandMcGinn(2005)reportedlowerentericCH4emissionsfromfeedlotcattlefedDRC‐baseddiets(2.81percentofGEI)thanfromcattlefedsteam‐rolledbarley‐baseddiets(4.03percentofGEI),possiblytheresultoflowerruminalpHonthecorn‐baseddiet(5.7vs.6.2,respectively;(VanKesselandRussell,1996)and/orhigherNDFinthebarleydiet.EntericCH4emissionswere38percent(barley)to65percent(corn)lowerinhigh‐concentrate(ninepercentsilage)finishingdietsthanongrower(70percentsilage)diets.
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FeedingCoproductIngredients:Distillersgrainswithsolubles(DGS)andothercoproductsofthemillingandethanolindustriesarewidelyusedascattlefeeds.Theeffectsoffeeding30to35percentDGS(DMbasis)onentericCH4emissionhavebeenvariable,rangingfromasignificantdecreaseof25to30percent(McGinnetal.,2009)tonoeffect(Halesetal.,2012),toanincrease(Halesetal.,2013).Thesedifferingresultswereprobablyduetodifferencesinforageandfatintake.InthestudybyMcGinnetal.(2009)thedietcontained65percentsilage,anddietaryfatintakeincreasedbyapproximatelythreepercentageunits8whendriedDGSwereaddedtothediet.Incontrast,Halesetal.(2012;2013)feddietsthatcontainedonly10percentforageandwereequalintotalfatconcentration.
RoughageConcentrationandForm:TheconcentrationandformofroughageinthedietwillaffectbothentericandmanureCH4production(Halesetal.,2014).Usingaruminalvolatilefattyacids(VFA)stoichiometrymodel,Dijkstraetal.(2007)suggestedthatCH4lossesfromcarbohydratessubstrates(gkg‐1substrate)inaconcentratedietwithruminalpHvariationandapHof6.5were2.11,3.18,3.38,and3.10forstarch,solublesugars,hemicellulose,andcellulose,respectively.Similarly,withdairycows,MoeandTyrrell(1979)reportedthatentericCH4productionperunitcarbohydratedigestedwasthreetimesgreaterforcellulosethanforhemicellulose.Aguerreetal.(2011)foundthatlactatingdairycattleemittedmoreCH4whentheforage:concentrateratiowaschangedfrom47:53to68:32,0.54kgCH4day‐1vs.0.65kgCH4day‐1respectively.
Ingeneral,astheconcentrationofforageinthedietincreases,entericCH4productionincreasesandthequantityofvolatilesolidsexcretedincreases.Usingamicrometeorologicalmassdifferencemethod,Harperetal.(1999)reportedCH4emissionsof230ganimal‐1daily(7.7to8.1percentofGEI)infeedercattleonpasture,butonly70ghead‐1daily(1.9to2.2percentofGEI)incattlefedhigh‐concentratediets.MeasuredCH4lossesforpasturecattlewerehigherthanvaluespredictedusingtheIPCC(1997;2006)CH4conversionfactors(MCForYm),orAustralianmethodology(NGGIC,1996).Incontrast,measuredCH4lossesforfeedlotcattlewereabout67percentofthoseestimatedusingtheIPCC(2006)YmofthreepercentofGEIortheAustralianmethodology(NGGIC,1996),butweresimilartovaluesreportedbyBranineandJohnson(1990),BlaxterandWainman(1964),andHalesetal.(2012;2013;Halesetal.,2014).
EntericfermentationoftropicalgrassesandlegumesmayalsobedifferentthanpredictedbyIPCCornationalGHGinventorymethods.KennedyandCharmley(2012)measuredentericCH4productionofcattlefedAustraliantropicalgrassesandlegumestobe5.0to7.2percentofGEintakewhichissimilartoIPCC(2006)Tier2estimates(5.5to7.5percentofGEintake)ofcattlefedforagedietsbutsomewhatlowerthantheAustralianNationalGreenhouseAccountsNationalInventoryReport(2007)of8.7to9.6percentofGEintake.
BlaxterandWainman(1964)comparedtheeffectsoffeedingdietswithsixvaryinghay:flakedcornratios(100:0,80:20,60:40,40:60,20:80,5:95)onentericCH4emissionswhenfedattwotimesthemaintenancelevelofintake.CH4emissionsasapercentageofGEIincreasedslightlybetweenthe100:0diet(7.44percent)andthe60:40diet(8.17percent),thendecreasedtothe5:95diet(3.4percent).
InIreland,Lovettetal.(2003)reportedtotaldailyentericCH4emissionsof0.15,0.19,and0.12kghead‐1(reportedas207,270,and170Lhead‐1)forheifersfeddietscontaining65,40,and10percentforage(theremainderasconcentrate),respectively.AsapercentageofGEI,losseswere6.1,6.6,and4.4percent,respectively.
8Theterm“percentageunits”inthisdocumentisusedtorefertochangesindietsoremissionsthatarenotproportionaltotheirbaselines.Forexample,areductioninemissionsfromthreepercenttoonepercentisa2“percentageunit”reductionora67percentreduction.
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Usingsteersfedall‐foragediets,Ominskietal.(2006)reportedthat,withintherangeofforagequalitiestested(alfalfa‐grasssilagecontaining61,53,51,or46percentNDF,DMbasis),entericCH4emissionsofsteers,asapercentageofGEI,werenotsignificantlyaffectedbyNDFcontent(5.1to5.9percent),althoughdailyCH4productiontendedtobehighestforthe53percentNDFdiet(0.12,0.15,0.13,and0.14kghead‐1day‐1,respectively).Similarly,usinggrazingsheep,MilanoandClark(2008)reportednoeffectofforagequality(ryegrass–52or47percentNDF,77or67percentorganicmatter[OM]digestibility)onentericCH4emissions.
AlthoughdietaryforagequalitymaysometimesnotaffectentericCH4emissions,itwillaffectforagedigestibilityandthusfecalexcretionofvolatilesolids.Thus,feedingmoredigestibleforagesorconcentratesmaydecreaseGHGemissionsfrommanure.
LevelofIntake:BlaxterandWainman(1964)comparedtheeffectsoffeedingsixdietsattwolevelsofintake.EntericCH4emissions,asapercentofGEI,were23percentgreaterinsteersfedatmaintenancethaninsteersfedat2Xmaintenance(8.1vs.6.6percentofGEI,respectively).However,inastudyevaluatingemissionsfromcattlefedryegrassdiets,MilanoandClark(2008)reportedthatasDMIincreasedfrom0.75percentofmaintenanceto2Xmaintenance,entericCH4emissions(gday‐1)increasedlinearly(r2=0.80to0.84).EmissionsasapercentageofGEIwerenotaffectedbyDMI,andrangedfrom4.9to9.5percentofGEI(15.9to30.4g[kgDMI]‐1).
Usingahigh‐forage(70percentbarleysilage)ormedium‐forage(30percentsilage)dietfedatlevelsfrom1Xtoapproximately1.8Xmaintenance,BeaucheminandMcGinn(2006b)notedthatentericCH4emissions,asapercentofGEI,decreasedbyapproximately0.77percentageunitsforeachunitincreaseinfeedintake(expressedasleveloffeedintakeabovemaintenance).ThiswaslessthantheestimateusingtheBlaxterandClapperton(1965)equation(0.93to1.28percentpercentageunits)orthe1.6percentageunitssuggestedbyJohnsonandJohnson(1995).
FeedAdditivesandGrowthPromoters:Cooprideretal.(2011)notedthatthedailyCH4andmanureN2Oproductionofcattlefedthrougha“natural”programwithnouseofantibiotics,ionophores,orgrowthpromotersweresimilartocattlefedinmoretraditionalsystemsthatusedanabolicimplantsanddietsthatcontainedionophoresandbeta‐agonists.However,typicalcattlehadgreateraveragedailyweightgain(1.85vs.1.35kgday‐1)andthustook42fewerdaystoreachthesameendpoint(596kgbodyweight[BW]).Thus,overall,cattlefedusingmoderngrowthtechnologieshad31percentlowerGHGemissionsperhead.CH4emissionskgofBWgain‐1was1.1kggreaterforthe“natural”cattle(5.02vs.3.92CO2‐eqkgBWgain‐1)thanthetraditionalcattle.
MonensindecreasesentericCH4emissionsinfinishingcattleby10to25percent(Tedeschietal.,2003;McGinnetal.,2004).However,infeedlotcattletheeffectsappeartobetransitory,lastingfor30daysorless(Guanetal.,2006).Incontrast,Odongoetal.(2007)reportedthatmonensin(24ppm)indairydietsdecreasedentericCH4byseventoninepercentforuptosixmonths.Waghornetal.(2008)foundnoeffectofmonensincontrolled‐releasecapsulesonCH4productionofpasture‐feddairycows,andHamiltonetal.(2010)alsofoundnochangeinentericCH4productionfrommonensinfedtodairycowsofferedatotalmixedration.
AnumberofstudieshavedemonstratedthatavarietyofhalogenatedanalogueshavethepotentialtodramaticallydecreaseruminalCH4production(Johnson,1972;Treietal.,1972;Johnson,1974;ColeandMcCroskey,1975;TomkinsandHunter,2004;Tomkinsetal.,2009).Ingeneraltheeffectwasgreaterincattlefedhigh‐foragedietsthanincattlefedhigh‐concentratediets.WhenCH4lossesweredramaticallyreduced,asignificantquantityofhydrogencouldbelost(onetotwopercentofGEI)viaeructation,suggestinganalternativeelectronsinkisalsoneeded.Ingeneral,thecompoundsdidnotimproveproductionefficiencysignificantly.Inaddition,thepotentialtoxicityofthesecompoundsmadethemimpracticalforroutineuse.
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Anumberofnitrocompounds(nitropropanol,nitroethane,nitroethanol)havealsosignificantlydecreasedruminalCH4productioninvitro(Andersonetal.,2003),withaconcomitantincreaseinhydrogenproduction/release.Theeffectappearedtobeenhancedwhenanitratereducingbacteriumwasaddedtotheculture(AndersonandRasmussen,1998).
SeveralstudieshavesuggestedthatfeedingofcondensedtanninscandecreaseentericCH4productionby13to16percent;eitherthroughadirecttoxiceffectonruminalmethanogensorindirectlyviaadecreaseinfeedintakeanddietdigestibility(Eckardetal.,2010).Tanninsmayalsoshiftnitrogenexcretionawayfromurinetofecesandinhibitureaseactivityinfeces,whichcouldpotentiallydecreaseNH3andN2Oemissionsfrommanure(Powelletal.,2009;Powelletal.,2011).
Feedingyeastcultures,enzymes,dicarboxylicacids(fumarate,malate,acrylate),andplantsecondarycompounds,suchassaponins,maydecreaseentericCH4emissionsundersomefeedingconditions(McGinnetal.,2004;BeaucheminandMcGinn,2006a;Ungerfeldetal.,2007;Beaucheminetal.,2008;Eckardetal.,2010;Martinetal.,2010).
NovelMicroorganismsandtheirProducts:KlieveandHegarty(1999)notedthatentericCH4productionmaybebiocontrolleddirectlybyuseofvirusesandbacteriocins.Leeetal.(2002)reportedthatabacteriocin(BovicinHC5)fromStreptococcusbovisreducedinvitroCH4productionbyupto50percent.Itappeared,thatincontrasttoresultswithmonensin,theruminalmicroorganismsdidnotadapttothebacteriocin.
AustralianresearchershavesuggestedthatvaccinatingagainstmethanogenscandecreaseCH4emissions.However,theresultshavenotbeenconsistent(Wrightetal.,2004;Eckardetal.,2010)becauseefficacyisdependentonthespecificmethanogenpopulationandthatisdependentondiet,location,andotherfactors.
Genetics:Aspreviouslynoted,severalstudieshavesuggestedthatcattleselectedforlowerRFI(i.e.,increasedfeeduseefficiency)tendtohavelowerruminalentericCH4production(Nkrumahetal.,2006;Hegartyetal.,2007),althoughtheeffectmaydependonstageofproduction(lactationvs.dryandpregnant)and/orqualityofthedietconsumed(Jonesetal.,2011).RFIismoderatelyheritable(0.28to0.58)(Mooreetal.,2009),thusitmightbepossibletogeneticallyselectforanimalswithlowerentericCH4production.However,FreetlyandBrown‐Brandl(2013)foundhigherCH4emissionsfrommoreefficientanimals.Thus,moreinformationisneededtodefineunderwhatconditionsCH4emissionsarerelatedtofeedefficiencyortogenetics.
FactorsAffectingEmissionsfromSheepSheep,likecattle,areruminantanimalsandthusthesamedietaryfactorswillpositivelyornegativelyaffectemissionsfromentericfermentation.
FactorsAffectingEmissionsfromSwineDietarymodificationscaneffectivelyreducenitrogenexcretionsandmitigateairemissions(especiallyNH3,aprecursorforN2O)fromlivestockoperations(Suttonetal.,1996;Canhetal.,1998b).FeedingstrategiestoreducenitrogenexcretionsincludereducedCPdietssupplementedwithsyntheticaminoacids(AA)(Panettaetal.,2006),andmodifyingthedietaryelectrolytestoreduceurinarypH(Canhetal.,1998a).Inbothhogandpoultryoperations,reductionsinNH3emissionshavebeenreportedbysupplementingwithAAandreducingCPindiets.
ReducingdietaryCPcontenthasbeenshowntobeaneffectivewaytoreducetheamountofnitrogenexcreted(Lenis,1993;HartungandPhillips,1994).ThiscanbeachievedwithoutanynegativeeffectonanimalperformancebysupplementingwithanimprovedsyntheticAAbalance,resultinginareductionofexcessCPexcreted(Canhetal.,1998b;Ferketetal.,2002).InU.S.‐typediets(corn‐soybeanmealbased)themostlimitingaminoacidsareLysine,Methionine,Threonine,
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andTryptophan,followedbyIsoleucine,Valine,andHistidine(Outor‐Monteiroetal.,2010).Suttonetal.(1996)reportedthatnitrogenexcretiondecreasedby28percentwhendietCPcontentdecreasedfrom13percentto10percent(corn‐soybeanmeal)forgrowing‐finishingpigdietssupplementedwithLys,Met,Thr,andTrp.SeveralstudiesreportedreductionsinnitrogenexcretionandsubsequentdecreasesinNH3emissionsinnon‐ruminants(swineandpoultry)(HartungandPhillips,1994;Canhetal.,1997;Canhetal.,1998a;Canhetal.,1998b;Hayesetal.,2004).Powersetal.(2007)observedthat,asaresultoffeedingreducedCPdietswithincreasedamountsofsyntheticAA,NH3emissionswerereducedby22percent(threeAA)and48percent(fiveAA)comparedwiththecontroldietcontainingonlyoneAA,anddiethadnoeffectonpigperformance.
Canhetal.(1998b)andNdegwaetal.(2008)reportedthatsomenitrogenexcretioncouldbeshiftedfromurinetofecesbyincreasingdietaryfibercontent,orbyreducingdietarynitrogencontent,withnosignificantdifferencesinanimalperformanceorgrowth.Urinarynitrogenispredominantlyinorganicinnatureandfecalnitrogenismostlyorganic.TheconversionofureafromurinetoNH3isafastprocess,whileconversionoforganicnitrogentovolatileNH3infecesisaslowprocess.
ThereductioninNH3emissionassociatedwithlowerCPdietsnotonlycomesfromreductioninnitrogenexcretion,butalsofromlowermanurepH.Portejoieetal.(2004)reportedthatslurrypHdecreasedby1.3unitswhendietaryCPdecreasedfrom20to12percent,andslurryfrompigsfedthelowerCPdiethadahigherDMcontentandlowerTANandTKNcontents.Leetal.(2008),Hannietal.(2007),andCanhetal.(1998b)alsoreportedthatlowermanurepHresultedfromfeedinglowerCPindiets.Itshouldbenotedthatwaterintakewasoftenrestrictedinearlierstudies.
AarninkandVerstegen(2007)summarizedfourdietarystrategiestoreduceNH3emissions:1)loweringCPintakeincombinationwiththeadditionoflimitingAA;2)shiftingnitrogenexcretionfromurinetofecesbyincludingfermentablecarbohydratesinthediet;3)loweringurinarypHwiththeadditionofacidifyingsaltstothediet;and4)loweringfecespHwiththeinclusionoffermentablecarbohydratesinthediet.Theyclaimedthatbycombiningthesestrategies,NH3emissionsingrowing‐finishingpigscouldbereducedbyatotalof70percent.Toreduceodorfrompigmanure,Leetal.(2007)suggestthatdietarysulfur‐containingAAshouldbeminimizedtojustmeettherecommendedrequirements.
CurrentresearchhasconcentratedonfarmproductionefficiencyandreducingNH3emissions;littlehasfocusedonGHGemissionsmitigation(Bhattietal.,2005).BallandMöhn(2003)showedthatlowCPdietscanreducetotalGHGemissionsfromgrowingpigsby25to30percent(directlyfromtheanimalsaswellasfromthemanureafterexcretion)andfromsowsby10to15percent.Atakoraetal.(2003)reporteda27.3percentdecreaseinCH4emissionsinpigsfed16percentCP(supplementedwithAA)diets,comparedwith19.0percentCPdiets.Atakoraetal.(2004)reportedthattheCO2equivalentsemittedbyfinishingpigsandsowsfedwheat‐barley‐canoladietswerereducedby14.3to16.5percentwhenfeedingthereducedCP,AA‐supplementeddiets,andweresimilarforfinishingpigsandsows.Thereductionwasonly7.5percentwhenfeedingthecorn‐soybeanmeal‐basedreducedCPdiet.Misselbrooketal.(1998)foundthatCH4emissionsduringstoragewerelessatlowthanatahighdietaryCPcontent.TheemissionofCH4wassignificantlyrelatedtocontentofdrymatter,totalcarbon,andVFAinthemanure.Misselbrooketal.(1998)claimedthatthe50percentreductioninCH4emissionfromtheslurryobservedwhenpigswerefedthelowerCPdietwasprobablytheresultofthereducedvolatilefattyacids(VFA)contentoftheslurry,andCH4emissionsweremorecloselyrelatedtoVFAcontentthantototalcarboncontent.ThereappearstobeacloserelationshipbetweenfermentablecarbohydratesinthedietandCH4production(Kirchgessneretal.,1991).ManurepHalsoinfluencesCH4production.Kimetal.(2004)noteda14percentreductioninCH4emissionwhenidealpHwasreducedoneunitthroughaddition
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ofacidogeniccalciumandphosphorussourcestopigdiets.IncreasingfermentablecarbohydratelevelsinthediettolowerthepHofmanure,withthegoalofreducingNH3emissions,mightincreaseCH4production(AarninkandVerstegen,2007).Canhetal.(1998a)observedthatforeach100‐gincreaseintheintakeofdietarynon‐starchpolysaccharide(NSP),theslurrypHdecreasedbyapproximately0.12unitsandtheNH3emissionfromslurrydecreasedby5.4percentwhendietaryNSPrangedfrom150to340gNSPkgDM‐1.
Feedingofdrieddistillersgrainswithsolubles(DDGS)hasbecomecommonpracticeintheswineindustry.Lietal.(2011)demonstratedthatfeedingdietscontaining20percentDDGSincreasedemissionsofCH4butnotN2OwhencomparedtocontroldietswithoutDDGS.ObservedincreasesinCH4emissionsapproximated18percent.Ammoniaemissionsresultingfromfeeding20percentDDGSwereeitherhigherorlowerthandietswithoutDDGS,dependingontheformoftracemineralsincludedinthediet.DietsincludinginorganicformsoftracemineralshadsevenpercentgreaterNH3emissions,whilefeedingorganicformsoftracemineralsdecreasedNH3emissionsalmost20percentcomparedtocontroldiets(Liuetal.,2011a).
Inarecentmeta‐analysis,Liuetal.(2011a)used32datapointsinasubgroupofstudiesthatincludeddietCPinformationtoanalyzetheeffectofdietCPonGHGemissions.Threefactors(dietCP,geographicregion,andswineproductionphase)wereconsideredintheregressionanalysis.DietCPwasnotasignificantfactor.EmissionsofCH4arepositivelycorrelatedwithdietcrudeproteininswineproduction,mostsignificantlyforlagoonandslurrystoragesystems(Liuetal.,2011a).Clarketal.(2005)determinedthatreducingdietaryCPmayactuallyincreaseCH4emissions,soresultsarevaried.IthadbeenexpectedthatalowerCPdietmayresultinlowernitrogenexcretion,andthusmightbeabletoreduceN2Oemissionsfrommanure.However,thishypothesiswasnotsupportedbytheresultsofthemeta‐analysis.
Dietformulationateachstageofthelifecycleinfluencesnutrientsexcretedinmanure,aswellasemissionsthatresultfromthatmanureduringstorageandpotentiallyfollowinglandapplication.Fromamodelingperspective,thefocusneedstobeonmanagementfactors,includingdietformulationandmanurehandlingpractices.
Feedefficiencyimprovementscanreduceemissionsthroughouttheentirefoodproductioncyclebyreducingtheamountoffeedneededformeatproduction,therebyreducinginputsintofeedproductionaswellasreducingmanurenutrientsthatmustbemanaged.Feedefficiencyistheproductofgeneticsandenvironment(management).Geneticdifferencesaredifficulttoassess,becausethisinformationisretainedbycompanies.Geneticimprovementsarenotinsignificantovertimeandmayinfactbealargercontributortogainsthanmanagement.However,fromamodelingperspective,thefocusneedstobeonmanagementfactors,includingdietformulationandin‐housemanure/litterpractices.FeedefficiencycouldbeamodelcomponentinthefutureoncemoredataontheimpactsoffeedefficiencyonGHGemissionsareavailable.
FactorsAffectingEmissionsfromMeatBirdsEmissionsofbothN2OandNH3canberestrictedbyreducingthelitternitrogencontentthroughdietmodification.Fergusonetal.(1998a;1998b)fedreduceddietaryproteindietstobroilerchickens.Althoughperformancewashinderedinbothstudies,NH3concentrationandlitternitrogencontentwerereducedsignificantlyasaresultofthelow‐proteindiets.Applegateetal.(2008)reportedsimilarlitternitrogeneffectswhenturkeytomswerefedreduced‐proteindiets.Noperformancedifferenceswereobserved.ThesedietswerethenfedtoturkeytomsbyLiuetal.(2011a),whoobserveda12percentreductioninNH3emissionsasaresultofreducingcumulativenitrogenintakeby9percent.FeedingspecificAAallowedforsimilarnitrogenintakesacrosstreatments,butreducedNH3emissionsby25percent(Liuetal.,2011a)andnitrogeninlitterby12percent(Liuetal.,2011b),becausenitrogenwasbetterutilizedbythebirds.Acrossalldiets,N2O
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emissionsmadeuplessthanonepercentofnitrogenoutput(Liuetal.,2011b),suggestingthatreducingdietarynitrogenmayhavelessinfluenceonN2Oemissionsthanotherfactors.
FactorsAffectingEmissionsfromLayingHensDietfactorscanalterairemissionsfromlayinghenfacilities.MuchoftheworktodatehasfocusedonreducingNH3emissions.Robertsetal.(2007)showedthatinclusionofdietarycornDDGS,wheatmiddlings,orsoyhullsloweredtheseven‐daycumulativemanureNH3emissionfrom3.9gkgofdrymanure‐1forthecontrolto1.9,2.1,and2.3gkgofdrymanure‐1,respectively;italsoloweredthedailyNH3emissionrate.ReducingtheCPcontentbyonepercenthadnomeasurableeffectonNH3emission.Wu‐Haanetal.(2007b)fedareduced‐emissionsdietcontaining6.9percentofaCaSO4‐zeolitemixtureandslightlyreducedproteinto21‐,38‐,and59‐week‐oldHy‐LineW‐36hens;theyobservedthatdailyNH3emissionsfromhensfedthereduced‐emissionsdiets(185.5,312.2,and333.5mgbird‐1)werelessthanemissionsfromhensfedthecontroldiet(255.1,560.6,and616.3mgbird‐1)fortrials1,2,and3,respectively.Totalnitrogenexcretionfromhensfedthecontrolandreduced‐proteindietswasnotdifferent(Wu‐Haanetal.,2007a).Becauseoftheacidifyingnatureofthediets,themassofnitrogenremaininginexcretafollowingathree‐weekstorageperiodwaslessfromhensfedthecontroldietthanfromhensfedthereduced‐proteindiet(Wu‐Haanetal.,2007a).Lietal.(2010)foundthatfeedingcornDDGSdecreasedthemassofNH3emitteddailyby80mghen‐1(592vs.512mghen‐1day‐1forzeropercentand20percentDDGS,respectively),andby14percentpereggproduced,anddailyCH4emissionsby13to15percent(39.3vs.45.4mghen‐1day‐1;and0.70vs.0.82mggegg‐1day‐1).
5.3.8 LimitationsandUncertaintyinEntericFermentationandHousingEmissionsEstimates
Attheentitylevel,uncertaintyinentericCH4productionincattletypicallyresultsfrom,lackofprecisioninestimatingenergyintake,feedtypeandintake,characteristicsofparticularfeedstuffs(i.e.,aciddetergentfiber,starch,etc.),DE,maximumpossibleCH4emissions,CH4conversionfactors(Ym),synergiesorcountereffectsbetweenmitigationoptions,andnetenergyexpenditurebytheanimal.TheassumptionsaboutimplicationsofdietarychangesonentericCH4productionarebasedonliteraturevalues(includingempiricalfieldstudies)andmaynotbeindicativeoftruechangesinemissionsforparticularanimaltypes,asthiswillvarydependingonanindividualanimal’shealth,managementpractices,animalactivities,andbaselinediet.Forswine,goats,AmericanBison,llamas,alpacas,andmanagedwildlife,therecommendedestimationmethodsforemissionsfromentericfermentationarebasedontheIPCCTier1approach,whichhasanuncertaintyof30to50percent.
MethaneemissionsfromdairycattlehousingareasareestimatedusingequationsfromDairyGEM(IFSM).Inpredictingemissions,uncertaintywillresultfromalackofprecisioninestimatingexcretedvolatilesolidsandnitrogenexcreted,pH,temperature,airvelocity,andsurfaceareaofexposedmanure,beddingpack,CH4conversionfactors(MCFs),andmaximumCH4‐producingcapacityformanures.Comparisonofmodeledvalueswithon‐farmevaluationshasfoundthemodelpredictson‐farmemissionswithinfiveto20percent(unpublisheddata).
MethaneemissionsfrompoultryhousingareasareestimatedusingtheIPCCTier1method.Uncertaintyinpredictionsofemissionsresultfromalackofprecisioninestimatingfeedintake,nitrogenexcretedandvolatilesolids,MCF,volatilizationfraction,andinsomeinstancesemissionfactorsthatwerechoseninthemodel.UnfortunatelythereisalackofpublishedinformationrelatedtoGHGemissionsfrompoultryandtothebestofourknowledgethismodelhasnotbeenvalidated/testedusingon‐farmdata.
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Muchofthepublisheduncertaintyinformationininventoryguidance,suchasIPCCGoodPracticeGuidance(IPCC,2000)andintheU.S.NationalGHGInventory(U.S.EPA,2013),focusonuncertaintiespresentincalculatinginventoriesattheregionalornationalscale,manyofwhichdonottranslatetotheentitylevel.Someofthesourcesofuncertaintyattheregionalornationalscaleincludedvariabilityinnativevegetationeatenbygrazinganimals,assumptionsaboutthetypesoffeedfarmersprovideforanimals(includingthepracticeofincludingnutritionalsupplements),managementpracticessuchashousingoptionsanddailyanimalactivity,averageanimalweights,andanimalpopulations.Thequantityofuncertaintyatlargerscalesisdifficulttodefine,dependentonboththeaccuracyinreportingpracticesandexperts’understandingoftheimplicationsofmanagementpracticesandtheaccuracyofparticularestimationmethodologies.Consistentimprovementinreportingpracticescanhelpremovesomeofthisuncertainty.
AvailabledefaultvaluesanduncertaintyinformationisincludedinTable5‐17.
Table5‐17:AvailableUncertaintyDataforEmissionsfromHousingandEntericFermentation
Parameter
Abbreviation/Sym
bol
DataInputUnit
EstimatedValue
Relativeuncertainty
Low(%)
Relativeuncertainty
High(%)
EffectiveLowerLimit
EffectiveUpperLimit
DataSource
DailyMilkProduction Milkkg
milk/animal/day
3% 5% ExpertAssessment
SupplementalFat(feedlot) S.Fat Percent 2 4 ExpertAssessment
Maximumdailyemissionsfordairycows Emax MJ/head 45.98 Millsetal.(2003)
TypicalAmmoniaLossesfromDairyHousingFacilities–Opendirtlots(cool,humidregion)
NH3loss
PercentofNex 15% 30%KoelshandStowell
(2005)TypicalAmmoniaLossesfromDairyHousingFacilities–Opendirtlots(hot,aridregion)
NH3loss
PercentofNex 30% 45%KoelshandStowell
(2005)TypicalAmmoniaLossesfromDairyHousingFacilities–Roofedfacility(flushedorscraped)Roofedfacility(dailyscrapeandhaul)
NH3loss
PercentofNex 5% 15%KoelshandStowell
(2005)
TypicalAmmoniaLossesfromDairyHousingFacilities–Roofedfacility(shallowpitunderfloor)
NH3loss
PercentofNex 10% 20%KoelshandStowell
(2005)
TypicalAmmoniaLossesfromDairyHousingFacilities–Roofedfacility(beddedpack)
NH3loss
PercentofNex 20% 40%KoelshandStowell
(2005)TypicalAmmoniaLossesfromDairyHousingFacilities–Roofedfacility(deeppitunderfloor,includesstorageloss)
NH3loss
PercentofNex 30% 40%KoelshandStowell
(2005)
TypicalAmmoniaLossesfromBeefHousingFacilities–Opendirtlots(cool,humidregion)
NH3loss
PercentofNex 30% 45%KoelshandStowell
(2005)
TypicalAmmoniaLossesfromBeefHousingFacilities–Opendirtlots(hot,aridregion)
NH3loss
PercentofNex 40% 60%KoelshandStowell
(2005)
TypicalAmmoniaLossesfromBeefHousingFacilities–Roofedfacility(beddedpack)
NH3loss
PercentofNex 20% 40%KoelshandStowell
(2005)
TypicalAmmoniaLossesfromBeefHousingFacilities–Roofedfacility(deeppitunderfloor,includesstorageloss)
NH3loss
PercentofNex 30% 40%KoelshandStowell
(2005)
TypicalAmmoniaLossesfromSwineHousingFacilities–Roofedfacility(flushedorscraped)Roofedfacility(dailyscrapeandhaul)
%NH3loss
PercentofNex 5% 15%KoelshandStowell
(2005)
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Parameter
Abbreviation/Sym
bol
DataInputUnit
EstimatedValue
Relativeuncertainty
Low(%)
Relativeuncertainty
High(%)
EffectiveLowerLimit
EffectiveUpperLimit
DataSource
TypicalAmmoniaLossesfromSwineHousingFacilities–Roofedfacility(shallowpitunderfloor)
%NH3loss
PercentofNex 10% 20%KoelshandStowell
(2005)
TypicalAmmoniaLossesfromSwineHousingFacilities–Roofedfacility(beddedpack)
%NH3loss
PercentofNex 20% 40%KoelshandStowell
(2005)TypicalAmmoniaLossesfromSwineHousingFacilities–Roofedfacility(deeppitunderfloor,includesstorageloss)
%NH3loss
PercentofNex 30% 40%KoelshandStowell
(2005)
TypicalAmmoniaLossesfromPoultryHousing–Roofedfacility(litter)(MeatProducingbirds)
%NH3loss
PercentofNex 25% 50%KoelshandStowell
(2005)TypicalAmmoniaLossesfromPoultryHousing–Roofedfacility(stackedmanureunderfloor,includesstorageloss)(Egg‐producingbirds)
%NH3loss
PercentofNex 25% 50%KoelshandStowell
(2005)
MethaneEmissionsfromGoats–Emissionfactorforgoats
EFGkg
CH4/head/day0.0137 IPCC(2006)
5.4 ManureManagement
Useofmanureasasourceofplantnutrientsreducestheneedforpurchasedcommercialfertilizer.Manurestorageallowsformanureapplicationstolandtobesynchronizedwithcropculturalneeds.Thispracticereducesthepotentialforsoilcompactionduetopoortimingofmanureapplication(wetsoilconditions)andmakesmoreefficientuseoffarmlabor.ManyanimalmanurestorageortreatmentstructurescreateanaerobicconditionsthatresultintheproductionandreleaseofGHGsandodors.Manurethatisrecycledtothelandbasecanhavepotentialnegativeeffectsonwaterquality(bothsurfaceandgroundwater).
Manurestorageandtreatment,asacomponentofmanuremanagementsystems,playsacriticalroleinGHGemissions.Attheentitylevel,variousmanurestorageandtreatmentapproacheswillleadtodifferentamountsofGHGemission.Animalmanurecanbeclassifiedintotwocategoriesbasedontheirphysicalproperties:solid,definedasdrymatterabove15percent;andliquid,definedasdrymatteroflessthan15percent(includingliquidmanurewithadrymatteroflessthan10percentandslurrymanurewithadrymatterbetween10and15percent).Threesolidmanurestorage/treatmentpractices(temporarystack/long‐termstockpile,composting,andthermo‐chemicalconversion)andeightliquidmanurestorage/treatmentpractices(aerobiclagoon,anaerobiclagoon/runoffholdingpond/storagetanks,anaerobicdigestion,combinedaerobictreatmentsystem,sand‐manureseparation,nutrientremoval,solid‐liquidseparation,andconstructedwetland)wereevaluatedandtheemissionestimationmethodsarepresented.Atthefarmentitylevel,severalpracticesareoftenstrategicallycombinedtotreatmanure.Inordertoprovidetoolstoevaluatethesescenarios,activitydata(i.e.,massflowdataandchemicalandphysicalcharacteristicsofinfluentandeffluent,environmentaltemperature,pH,andtotalnitrogen)fromindividualpracticeswillbeusedtolinkpracticesinthecombinedsystemforindividualfarmentities.AschematicstructureofpossiblecombinationsofmanurestorageandtreatmentpracticesattheentitylevelispresentedinFigure5‐7.Asillustratedinthefigure,manurecanbehandledasasolidorliquid.Foreachstream,themanurecanbeapplieddirectlytoland,stored,ortreatedbeforestorageorlandapplication.Insomepractices,solidsareseparatedfromtheliquidmanurestreamandtreatedusingasolidshandlingsystem.
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Figure5‐7:SchematicStructureofPossibleCombinationofManureStorageandTreatmentPractices
Note:Individualpracticescouldbecombinedtogethertotreatmanurebasedontheneedattheentitylevel.
Eachmanuremanagementpracticeisdescribedasanindividualunitpracticeinthisdocument.ThereferencesforestimationofGHGemissionforindividualpracticearelistedinTable5‐18.
Table5‐18:ListofIndividualManureStorageandTreatmentPractices
Section StorageandTreatmentPracticesMajorReferencesforGHG
EstimationSolidmanure5.4.1 Temporaryandlong‐termstorage IPCC(2006);U.S.EPA(2011)0 Composting IPCC(2006);U.S.EPA(2011)Liquidmanure5.4.3 Aerobiclagoon IPCC(2006);U.S.EPA(2011)
5.4.4Anaerobiclagoon/runoffholdingponds/storagetanks
Sommeretal.(2004)
5.4.5 Anaerobicdigestionwithbiogasutilization IPCC(2006);CDM(2012)
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Section StorageandTreatmentPracticesMajorReferencesforGHG
Estimation5.4.6 Combinedaerobictreatmentsystem Vanottietal.(2008)5.4.7 Sand–manureseparation5.4.8 Nutrientremoval5.4.9 Solid–liquidseparation FordandFleming(2002)
5.4.10 ConstructedwetlandSteinetal.(2006;2007b)Stoneetal.(2002;2004)
5.4.11 Thermo‐chemicalconversion
TheremainderofthissectionpresentsthemethodforestimatingGHGsfromthesourceslistedinTable5‐18.ForeachsourceofGHGswithanestimationmethod,thefollowinginformationisprovided:
OverviewoftheGHGSourceandtheResultingGHGs.Thissectionprovidesanoverviewofmanuremanagementtechnology,theresultingGHGemissions,andthemethodologyproposedforestimatingtheemissions.
RationaleforSelectedMethod.Thissectionpresentsthereasoningfortheselectionofthemethodrecommendedinthisreport.
ActivityData.ThissectionliststheactivitydatarequiredforestimatingGHGsattheentitylevel.
AncillaryData.ThissectionlistsancillarydatasuchasCH4conversionfactors(MCF)andmaximumCH4productioncapacity(B0).
Method.Thissectionprovidesdetaileddescriptions,includingequationsfortheselectedmethods.
ForeachsourceofGHGswithoutanestimationmethod,aqualitativeoverviewisprovided.MethodsforestimatingNH3emissionsareprovidedinAppendix5‐C.
5.4.1 TemporaryStackandLong‐TermStockpile
5.4.1.1 OverviewofTemporaryStackandLong‐TermStockpiles
Managementmethodsforstoredmanurearedifferentiatedbythelengthoftimetheyarestockpiled(i.e.,temporarystackandlong‐termstorage).Temporarystackisashort‐termmanurestoragemethodthatisusedtotemporarilyholdsolidmanurewhenbadweatherprohibitslandapplication,and/orwhenthereislimitedavailabilityofcroplandformanureapplication.Withtemporarystack,
MethodforEstimatingEmissionsfromManureStorageandTreatment–TemporaryStackandLong‐TermStockpile
Methane
IPCCTier2approachusingIPCCandU.S.EPAInventoryemissionfactors,utilizingmonthlydataonvolatilesolidsanddrymanure.Volatilesolidscontentcanbeobtainedfromsamplingandlabtesting.
Methodisonlyreadilyavailablemethod.
NitrousOxide
IPCCTier2approachusingU.S.‐basedemissionfactorsandmonthlydataonvolatilesolids,totalnitrogen,anddrymanure.
Nospecificmodelsexist;methodistheonlyreadilyavailablemethod.
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themanureisremovedandappliedtolandwithinafewweeksofpiling.Temporarystorageisnotapreferredmethodtostoremanurebecauseitrequiresthemanuretobehandledtwice.
Long‐termstorageisapermanentmanurestoragemethodinwhichsolidmanureispiledonaconfinedareaorstoredinadeeppitforlongerthansixmonths.Inlow‐rainfallareas,thestockpilecanbepiledonthefieldwiththeinstallationofnutrientrunoffcontrol.Inhigherrainfallareas,aconcretepadandwallareconstructedtostoresolidmanureandpreventnutrientrunofffromheavyrain.
Greenhousegasesgeneratedfrombothstoragemethodshaveapatternsimilartothatofentericfermentation.CarbonandnitrogencompoundsinmanurearebrokendownbymicrobestoCH4,andN2O.ThemainfactorsinfluencingGHGemissionsfromstoragearetemperatureandstoragetime.Duetothelongerstoragetime,long‐termstockpilesolidmanurestoragegeneratesasignificantamountofGHGs.Temporarystack,asashort‐termmanurestoragemethod,generateslessGHGsthanthelong‐termstockpilesolidstorage.However,itisstillnecessarytoquantitativelydelineatetheemissionsinordertoassistlivestockandpoultryfarmsinevaluatingtheirmanuremanagementoperations.Temporarystackandlong‐termstockpilesofmanurealsoproduceNH3;proposedmethodstoestimateNH3emissionsarepresentedinAppendix5‐C.
TheIPCCTier2methodologyisprovidedforestimatingCH4emissionsfromtemporarystacksorlong‐termstockpiles.ThismethodologyusesacombinationofIPCCandcountry‐specificemissionfactorsfromtheU.S.EPAGHGInventory.Theamountofmanure,volatilesolidscontent,andtemperaturearespecifictotheentity.ThemethodforcalculatingN2OemissionsisthesameastheequationpresentedintheU.S.GHGInventory.
RationaleforSelectedMethodTheIPCCequationsaretheonlyavailablemethodsforestimatingCH4,andN2Oemissionsfromtemporarystackandlong‐termstockpiles.Thesemethodologiesbestdescribethequantitativerelationshipamongactivitydataattheentitylevel.
ActivityDataInordertoestimatethedailyCH4emissions,thefollowinginformationisneeded:9
Animaltype Totaldrymanure Volatilesolidsofdrymanure10 Temperatures(localambienttemperatureandmanuretemperature)
InordertoestimatethedailyN2Oemission,thefollowinginformationisneeded:
Totaldrymanure Totalnitrogencontentofthemanure
ThetotalnitrogencontentofthemanureenteringstoragesystemscanbeestimatedaccordingtothenitrogenbalancemethodasdescribedinEquation5‐9:TotalNitrogenEnteringManureStorageandTreatmentThefractionofnitrogenexcretedbyananimalthatisnotemittedasagasistheportionthatentersstorage.
9Althoughdailyestimatesfortheactivitydataareoptimal,trackingthislevelofdetailwouldbeburdensome.Annualestimatesdon’tallowforseasonalvariationindietsandclimate.Consequently,disaggregationofthedatabyseasonorbyperiodsofmajorshiftsinanimalpopulationissuggested.
10Volatilesolids,totalnitrogencontent,andammonia‐nitrogencontentshouldbeobtainedthroughsamplingandlabtesting.
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AncillaryDataTheancillarydatausedtoestimateCH4emissionfortemporarystorageandlongtermstockpilesare:maximumCH4producingcapacities(B0)andMCFs.TheB0valuesforsolidmanurestorageareobtainedfromtheIPCCandlistedinTable5‐19.Methaneconversionfactorsfordifferentmanuremanagementsystems(includingtemporarystorageofsolidmanure)arealsoobtainedfromtheIPCCandlistedinTable5‐20and5‐16.
TheancillarydatausedtoestimateN2OemissionsfortemporarystorageandlongtermstockpilesaretheN2OemissionfactorsforsolidmanurestoragesystemsarepresentedinTable5‐23(U.S.EPA,2011).
5.4.1.2 Method
MethaneEmissionsfromTemporaryStackandLong‐TermStockpileTheTier2approachbytheIPCCmodelisrecommendedtoestimateCH4emissionsandisdescribedinEquation5‐26(IPCC,2006).DailyCH4emissionisestimatedasafunctionofthevolatilesolidsinmanureplacedintothestorageandtheanimal‐specificMCF.
aDrymanurereferstomaterialremainingafterremovalofwater.Itisdeterminedthroughtheevaporationofwaterfromthemanuresampleat103‐105°C.Forcedairovenisthemostcommonequipmenttomeasurethedrymatter.
Table5‐19:MaximumCH4ProducingCapacities(B0)fromDifferentAnimals
Animal
MaximumCH4
ProducingCapacity(B0)
(m3/kgVS)
Animal
MaximumCH4
ProducingCapacity(B0)
(m3/kgVS)Beefreplacementheifers 0.33b Breedingswine 0.48Dairyreplacementheifers 0.17b Layer(dry) 0.39Maturebeefcows 0.33b Layer(wet) 0.39Steers(>500lbs) 0.33b Broiler 0.36Stockers(All) 0.17b Turkey 0.36Cattleonfeed 0.33b Duck 0.36Dairycow 0.24b Sheep 0.19bCattle 0.19b Feedlotsheep 0.36bBuffalo 0.1a Goat 0.17b
Marketswine 0.48Horse 0.3Mule/Ass 0.33
aTherearenodataforNorthAmericaregion;thedatafromWesternEuropeareusedtocalculatetheestimation.bNumbersarefromtheEPAU.S.Inventory:1990‐2009(U.S.EPA,2011).OthernumbersarefromIPCC(2006).
Equation5‐26:IPCCTier2ApproachforEstimatingCH4 Emissions
.
Where:ECH4 =CH4emissionsperday(kgCH4day‐1)m =Totaldrymanureperdaya(kgdrymanureday‐1)VS =Volatilesolids(kgVS(kgdrymanure)‐1)B0 =MaximumCH4producingcapacityformanure(m3CH4(kgVS)‐1)MCF =CH4conversionfactorforthemanuremanagementsystem(%)0.67=Conversionfactorofm3CH4 tokgCH4
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5-80
Table5‐20:MethaneConversionFactorsforTemporaryStorageofSolidManurefromDifferentAnimals
AnimalMethaneConversionFactor(%)
Temp=10‐14°C Temp=15‐25°C Temp=26‐28°CDairycow 1 1.5 2Cattle 1 1.5 2Buffalo 1 1.5 2Marketswine 1 1.5 2Breedingswine 1 1.5 2Layer(dry) 1.5 1.5 1.5Broiler 1.5 1.5 1.5Turkey 1.5 1.5 1.5Duck 1 1.5 2Sheep 1 1.5 2Goat 1 1.5 2Horse 1 1.5 2Mule/Ass 1 1.5 2
Source:IPCC(2006).
Table5‐21:MethaneConversionFactorsforLong‐TermStockStorageofSolidManurefromDifferentAnimals
AnimalMethaneConversionFactor(%)
Temp= 10‐14°C Temp=15‐25°C Temp=26‐28°CDairycow 2 4 5Cattle 2 4 5Buffalo 2 4 5Marketswine 2 4 5Breedingswine 2 4 5Layer(dry) 1.5 1.5 1.5Broiler 1.5 1.5 1.5Turkey 1.5 1.5 1.5Duck 1 1.5 2Sheep 1 1.5 2Goat 1 1.5 2Horse 1 1.5 2Mule/Ass 1 1.5 2
Source:IPCC(2006).
Table5‐22:MethaneConversionFactorsforLong‐TermStorageofSlurryManurefromBuffalo
Temperature(°C)Methane Conversion
Factor(%)Temperature(°C)
MethaneConversionFactor(%)
10 17 20 4211 19 21 4612 20 22 5013 22 23 5514 25 24 6015 27 25 6516 29 26 7117 32 27 7818 35 28 8019 39
Source:IPCC(2006).
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NitrousOxideEmissionsfromTemporaryStackandLong‐TermStockpileNitrousoxideemissionsaredependentonnitrificationanddenitrification.ManurestorageisoneofthemainsourcesofU.S.overallN2Oemissions.TheonlyquantitativemethodforestimatingN2OemissionsfromsolidmanureistheIPCCTier2approach,whichisalsousedfortheU.S.Inventory.ThisapproachisbasedontheuseofemissionfactorsfromthemostrecentIPCCGuidelinesandtotalnitrogenvaluesareestimatedaccordingtoEquation5‐9.Equation5‐27presentstheequationtoestimatetheN2Oemissionsforsolidmanure.
aDrymanurereferstomaterialremainingafterremovalofwater.Itisdeterminedthroughtheevaporationofwaterfromthemanuresampleat103‐105°C.Forcedairovenisthemostcommonequipmenttomeasurethedrymatter.
Table5‐23:N2OEmissionFactorsforSolidManureStorageTypeofStorage N2OEmissionFactor(kgN2O‐N/kgN)
Temporarystorageofsolid/slurrymanure 0.005
Long‐termstorageofsolidmanure 0.002
Long‐termstorageofslurrymanure 0.005Source:U.S.EPA(2011).
5.4.2 Composting
5.4.2.1 OverviewofComposting
Equation5‐27:IPCCTier2ApproachforEstimatingN2OEmissions
Where:
EN2O =Nitrousoxideemissionperday(kgN2Oday‐1)
m =Totaldrymanureperdaya(kgdrymanureday‐1)
EFN2O=N2Oemissionfactor(kgN2O‐NkgN‐1)
TN =Totalnitrogenatagivenday(kgN(kgdrymanure)‐1)
=ConversionofN2O‐NemissionstoN2Oemissions
MethodforEstimatingEmissionsfromManureStorageandTreatment–Composting
Methane
IPCCTier2approach,utilizingmonthlydataonvolatilesolidsanddrymanure.Volatilesolidscontentcanbeobtainedfromsamplingandlabtesting.
Methodistheonlyreadilyavailablemethod.
NitrousOxide
IPCCTier2approach,utilizingdataonanitrousoxideemissionfactor,totalinitialnitrogen,anddrymanure.
Methoddependsonwhetherthesystemisinvessel,staticpile,intensivewindrow,orpassivewindrow.
Methodisonlyreadilyavailablemethod.
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Compostingisthecontrolledaerobicdecompositionoforganicmaterialintoastable,humus‐likeproduct(USDANRCS,2007).Animalmanuremaybecompostedinavarietyofdifferentsystems,includingin‐vesselsystems,windrows,orstaticpiles.In‐vesselsystemshandlecompostinaclosedsystemsuchasarotarydrumorboxthatincorporatesregularmovementtoensureproperaeration.Thelargestcompostingoperationsdivideupthecompostintolongheapsforwindrowcompostingorintoonelargepileforaeratedstaticpilecomposting.Intheformermethod,properoxygenflowcanbemaintainedviamanualturningorpipesystems,whereasinthelattermethod,itismaintainedthroughpipesystems.Compostinghasbecomeapopularmethodinsomeregionstodecreasethevolumeandweightoflivestockmanureandtoproduceaproductthatisoftenmoreacceptabletofarmersasafertilizer.Duringa100‐to120‐daycompostingperiod,theweightandvolumeofmanuremaybedecreasedby15to70percent(Eghballetal.,1997;Inbaretal.,1993;Lopez‐Real&Baptista,1996).Furthermore,theheatgeneratedthroughthecompostingprocesscankillparasites,pathogens,andweedseedsfoundinanimalwaste,creatingasaferproductforcropapplication.
ThequantityofGHGemissionsisaffectedbythecompostingmethodemployed.Haoetal.(2001)reportedthatGHGemissionsfromcattlemanurecompostincreasedabouttwofoldwhenthecompostwasactivelycompostedratherthanpassivelycompostedinwindrows.Activewindrowswereturnedsixtimes(days14,21,29,50,70,and84).Passivewindrowswereneverturned,butairwasintroducedintothewindrowsbyaseriesofopen‐endedperforatedsteelpipes.TotheextentthattherateofGHGformationdependsonoxygensaturationintheporespace,aerationmethod(i.e.,forced‐airvs.passive/convective)andrate(orturningfrequency)willaffectthemagnitudeofGHGemissionsduringthecompostingprocess.
Eghballetal.(1997)reportedthat19to45percentofthenitrogenpresentinmanurewaslostduringcomposting,withthemajorityofthispresumablyasNH3.Usingchangesinthenitrogen:phosphorusratiooffeedlotmanurethatwasplacedincompostwindrowsandthenitrogen:phosphorusratioof“finished”compost,Coleetal.(2011)estimatedthat10to20percentofnitrogenwaslostduringcomposting.TheU.S.EPAcurrentlyassumesthatoneto10percentofnitrogenenteringcompostsystemsislostasN2O(IPCC,2006;U.S.EPA,2009).
TheIPCCTier2methodologyisprovidedforestimatingCH4andN2Oemissionsfromcomposting.Thismethodologyusescountry‐specificemissionfactorsfromtheU.S.EPAGHGInventory.Theamountofmanure,volatilesolidscontent,andtemperaturearespecifictotheentity.TheGHGestimationmethodformanurecompostingdoesnotconsiderotherorganiccarbonsourcesthatmightbeaddedintomanurecomposting.
RationaleforSelectedMethodTheIPCCequationsaretheonlyavailablemethodsforestimatingCH4andN2Oemissionsfromcomposting.Thesemethodologiesbestdescribethequantitativerelationshipamongstactivitydataattheentitylevel.
5.4.2.2 ActivityData
InordertoestimatethedailyCH4emissions,thefollowinginformationisneeded:
Animaltype Totaldrymanure Volatilesolidsofdrymanure Temperatures(localambienttemperatureandmanuretemperature)
InordertoestimatethedailyN2Oemissions,thefollowinginformationisneeded:
Totaldrymanureinthestorage
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Totalnitrogeninmanure
ThetotalnitrogencontentofthemanureenteringstoragesystemscanbeestimatedaccordingtothenitrogenbalancemethodasdescribedinEquation5‐9:TotalNitrogenEnteringManureStorageandTreatmentThefractionofnitrogenexcretedbyananimalthatisnotemittedasagasistheportionthatentersstorage.
5.4.2.3 AncillaryData
TheancillarydatausedtoestimateCH4emissionsformanurecompostingare:maximumCH4producingcapacities(B0)andMCFs.TheB0valuesareobtainedfromtheIPCC(2006)andlistedinTable5‐19.TheMCFvaluesareobtainedfromEPA(U.S.EPA,2011)andlistedinTable5‐24.
TheancillarydatausedtoestimateN2OemissionformanurecompostingaretheN2Oemissionfactors(Table5‐25).
5.4.2.4 Method
MethaneEmissionsfromCompostingTheTier2approachintheIPCCmodelisadaptedwithcountry‐specificfactorstoestimateCH4emissionsfromcompostingofsolidmanure.DailyCH4emissionsareestimatedasafunctionofthevolatilesolidsinmanureplacedintothestorageandtheMCF.
aDrymanurereferstomaterialremainingafterremovalofwater.Itisdeterminedthroughtheevaporationofwaterfromthemanuresampleat103‐105°C.Forcedairovenisthemostcommonequipmenttomeasurethedrymatter.
TheB0valuesforcompostingsolidmanureareobtainedfromtheIPCC(2006)andarelistedinTable5‐19.MethaneconversionfactorsfordifferentapproachesofcompostingsolidmanureareobtainedfromIPCC(2006).
Equation5‐28:IPCCTier2ApproachforCalculatingMethaneEmissionsfromCompostingSolidManure
.
Where:
ECH4 =Methaneemissionsperday(kgCH4day‐1)
m =Totaldrymanurea(kgdrymanureday‐1)
VS =Volatilesolids(kgVS(kgdrymanure)‐1)
B0 =MaximumCH4producingcapacityformanure(m3CH4(kgVS)‐1)(seeTable5‐24)
MCF =Methaneconversionfactorforthemanuremanagementsystem(%)
0.67 =Conversionfactorofm3CH4tokgCH4
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Table5‐24:MethaneConversionFactorsforCompostingSolidManure
AnimalMethaneConversionFactor(%)
CoolClimate TemperateClimate
WarmClimate
Manurecomposting–invessel 0.5 0.5 0.5
Manurecomposting–staticpile 0.5 0.5 0.5Manurecomposting–intensivewindrow
0.5 1 1.5
Manurecomposting–passivewindrow 0.5 1 1.5Source:IPCC(2006).
NitrousOxideEmissionsfromCompostingATier2IPCCmodelisadaptedtoestimateN2Oemissionsfromcompostingofsolidmanure.Equation5‐29presentstheequationforestimatingN2Oemissionsfromcompostingofsolidmanure.EmissionfactorsfordifferentcompostingmethodsarelistedinTable5‐25andtotalnitrogenisestimatedaccordingtoEquation5‐9.11
aDrymanurereferstomaterialremainingafterremovalofwater.Itisdeterminedthroughtheevaporationofwaterfromthemanuresampleat103‐105°C.Forcedairovenisthemostcommonequipmenttomeasurethedrymatter.
Table5‐25:N2OConversionFactors(EFN2O)forCompostingSolidManure
Category N2OEmissionFactor(kgN2O‐N/kgTN)CattleandSwineDeepBedding(ActiveMix) 0.07
CattleandSwineDeepBedding(NoMix) 0.01
PitStorageBelowAnimalConfinements 0.002Source:IPCC(2006).
11SomestudieshavebeenconductedontherateofN2Oemissionsforswine(Fukummotoetal.,2003;Szantoetal.,2006)butthisdataislimitedandfurtherresearchisnecessary.SeeSection0ResearchGapsforfurtherdiscussion.
Equation5‐29:IPCCTier2ApproachforEstimatingN2OEmissionsfromCompostingofSolidManure
Where:
EN2O =Nitrousoxideemissionsperday(kgN2Oday‐1)
m =Totaldrymanurea(kgday‐1)
EFN2O=N2Oemission(loss)relativetototalnitrogeninmanure(kgN2O‐N(kgTN)‐1)
TN =Totalnitrogenintheinitial(fresh)manure(kgTN(kgdrymanure)‐1)
=ConversionofN2O‐NemissionstoN2Oemissions
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5.4.3 AerobicLagoon
5.4.3.1 OverviewofAerobicLagoons
Aerobiclagoonsareman‐madeoutdoorbasinsthatholdanimalwastes.Theaerobictreatmentofmanureinvolvesthebiologicaloxidationofmanureasaliquid,witheitherforcedornaturalaeration.Naturalaerationislimitedtoaerobiclagoonswithphotosynthesisandisconsequentlyshallowtoallowforoxygentransferandlightpenetration.Thesesystemsbecomeanoxicduringlow‐sunlightperiods.Duetothedepthlimitation,naturallyaeratedaerobiclagoonshavelargesurfacearearequirementsandareimpracticalforlargeoperations.
TheIPCCTier2methodologyisprovidedforestimatingCH4andN2Oemissionsfromaerobiclagoons.ThismethodologyusesacombinationofIPCCandcountry‐specificemissionfactorsfromtheU.S.EPAGHGInventory.AerobicconditionsresultintheoxidationofcarbontoCO2,notthereductionofcarbontoCH4,thusCH4emissionsfromaerobiclagoonsisconsiderednegligibleandisdesignatedaszeroinaccordancewithIPCC.ThemethodforcalculatingN2Oemissionsaccountsforthevolumeofthelagoonaswellasthetotalnitrogencontentofthemanure.
5.4.3.2 RationaleforSelectedMethods
TheIPCCequationsaretheonlyavailablemethodsforestimatingCH4,andN2Oemissionsfromaerobiclagoons.Thesemethodologiesbestdescribethequantitativerelationshipamongactivitydataattheentitylevel.
5.4.3.3 ActivityData
Noactivitydataareneeded(MCF=0)fortheestimationofCH4gasemissions.
InordertoestimatethedailyN2Oemissions,thefollowinginformationisneeded:
Surfaceareaoflagoon Volumeofthematerialinthelagoon Totalnitrogencontentofthemanure
ThetotalnitrogencontentofthemanureenteringstoragesystemscanbeestimatedaccordingtothenitrogenbalancemethodasdescribedinEquation5‐9.Thefractionofnitrogenexcretedbyananimalthatisnotemittedasagasistheportionthatentersstorage.
5.4.3.4 AncillaryData
TheancillarydatausedtoestimateN2OemissionsforaerobiclagoonareN2Oemissionfactors(U.S.EPA,2011).
MethodforEstimatingEmissionsfromManureStorageandTreatment–AerobicLagoon
Methane
TheMCFforaerobictreatmentisnegligibleandisdesignatedaszeropercentinaccordancewiththeIPCCGuidance.
NitrousOxide
IPCCTier2methodutilizingIPCCemissionfactors. Methodtakesintoaccountthevolumeofthelagoonandthetotalnitrogencontentof
themanure. Methodistheonlyreadilyavailablemethod.
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5.4.3.5 Method
MethaneEmissionsfromAerobicLagoonTheMCFforaerobictreatmentisnegligibleandwasdesignatedaszeropercentinaccordancewiththeIPCC(2006).ThesolidsfromthebottomofthelagoonhavesignificantvolatilesolidsandB0associatedwithlivestocktype;thecharacteristicsofthesolidsshouldbemeasuredandusedastheinputstoestimateemissionsofGHGsforsubsequentstorageandtreatmentoperations.
NitrousOxideEmissionsfromAerobicLagoonTheTier2approachintheIPCCmodelisadaptedtoestimateN2Oemissionsfromaerobiclagoons.TheN2OconversionfactorsfordifferentaerationsystemarelistedinTable5‐26.TheestimationmethodforN2OemissionsisprovidedinEquation5‐30.
5.4.4 AnaerobicLagoon,RunoffHoldingPond,StorageTanks
5.4.4.1 OverviewofAnaerobicLagoons,RunoffHoldingPonds,andStorageTanks
Table5‐26:N2OConversionFactors(EFN2O)forAerobicLagoons
AerationTypeN2OConversion Factor
(kgN2O‐N/kgN)Naturalaeration 0.01Forcedaeration 0.005Source:IPCC(2006).
Equation5‐30:CalculatingN2OemissionsfromAerobicLagoons
Where:
EN2O =Nitrousoxideemissionsperday(kgN2Oday‐1)
V =Totalvolumeofthelagoonliquid(m3day‐1)
EFN2O=Nitrousoxideemission(loss)relativetototalnitrogeninthelagoonliquid (kgN2O‐N(kgTN)‐1)
TN =Totalnitrogeninthelagoonliquid(kgTNm‐3)
=ConversionofN2O‐NemissionstoN2Oemissions
MethodforEstimatingEmissionsfromManureStorageandTreatment–AnaerobicLagoons,RunoffHoldingPonds,StorageTanks
Methane
Sommermodel(Sommeretal.,2004)isusedwithdegradableandnondegradablefractionsofvolatilesolidsfromMølleretal.(2004).
Thismethodwasselectedasitaccountsformanuretemperatureandtotalvolatilesolidscontentofmanure.Volatilesolidscontentcanbeobtainedfromsamplingandlabtesting.
NitrousOxide
EmissionsareafunctionoftheexposedsurfaceareaandU.S.‐basedemissionfactors. Methodistheonlyreadilyavailableoption.
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Themostfrequentlyusedliquidmanurestoragesystemsareanaerobiclagoons(intheSouthernportionoftheUnitedStates),earthenorearthen‐linedstorages(intheNorthernportionofthecountry),runoffholdingponds,andabove‐gradestoragetanks.Anaerobiclagoonsareearthenbasinsthatprovideanenvironmentforanaerobicdigestionandstorageofanimalwaste.BoththeAmericanSocietyofAgriculturalandBiologicalEngineersandU.S.DepartmentofAgricultureNaturalResourcesConservationServicehaveengineeringdesignstandardsforconstructionandoperationofanaerobiclagoons.Inmostfeedlotsaholdingpondisconstructedtocollectrunoffforshort‐termstorage.Storagetanksrangefromlower‐costearthenbasinstohigher‐cost,glass‐linedsteeltanks.Themanurethatentersthesesystemsisusuallydilutedwithflushwater,waterwastedatstalls,andrainwater.
Allofthesestoragesystems(withoutaeration)arebiologically‐anaerobiclagoons,whichmeanthattheyhavesimilarpotential,aswithentericfermentation,toproduceCH4andN2O.DuetothelargequantityofliquidmanureproducedintheUnitedStates,liquidmanurestoragecanbeamajorsourceofGHGemissionsfromanimaloperations.IntermsofestimationofGHGemissionfromanaerobiclagoon/runoffholdingpond/storagetanks,thesestoragesystemsareclassifiedintofourcategories:1)coveredstoragewithacrustformedonthesurface;2)coveredstoragewithoutacrustformedonthesurface;3)uncoveredstoragewithacrustformedonthesurface;and4)uncoveredstoragewithoutacrustformedonthesurface.
ThealgorithmsforcalculatingCH4emissionsdescribedbySommeretal.(2004)arerecommendedforestimatingemissionsattheentity‐level.Themodelconsidersvolatilesolidstobethemainfactorinfluencingemissionsfrommanureandrelatesemissionstothecontentofdegradablevolatilesolids.Nitrousoxideisestimatedasafunctionoftheexposedsurfaceareaofthemanurestorageandwhetheracrustispresentonthesurface.
RationaleforSelectedMethodsTheSommeralgorithmslinkcarbonturnover,volatilesolids,temperature,andstoragetimetoCH4emissionsestimatesandisthebestavailablemethodforestimatingCH4emissionsattheentitylevel.ThemethodprovidedforN2Oistheonlyavailablemethodforestimatingemissions.Thesemethodologiesbestdescribethequantitativerelationshipamongactivitydataattheentitylevel.
5.4.4.2 ActivityData
InordertoestimatethedailyCH4emissions,thefollowinginformationisneeded:
Animaltype Totaldrymanure Volatilesolidsinthestorage Temperatures(localambienttemperatureandmanuretemperature)
InordertoestimatetheN2Oemission,thefollowinginformationisneeded:
Totaldrymanure Totalnitrogencontentofthemanure Theexposedsurfaceareaofthemanurestorage
ThetotalnitrogencontentofthemanureenteringstoragesystemscanbeestimatedaccordingtothenitrogenbalancemethodasdescribedinEquation5‐9.Thefractionofnitrogenexcretedbyananimalthatisnotemittedasagasistheportionthatentersstorage.
5.4.4.3 AncillaryData
TheancillarydatausedtoestimateCH4emissionsforanaerobiclagoons,runoffholdingponds,andstoragetanksarethemaximumCH4producingcapacities(B0),potentialCH4yield(ECH4,pot),rate
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correctingfactors(b1andb2),Arrheniusconstant(A),activationenergy(E),gasconstant(r),andcollectionefficiency(η)forliquidmanurestoragefromdifferentanimals.ThesedataareavailablefromtheIPCC(2006)andSommeretal.(2004)andarelistedinTable5‐27.
TheancillarydatausedtoestimateN2Oemissionsforanaerobiclagoons,runoffholdingponds,andstoragetanksistheN2OemissionfactorfromTable5‐29(U.S.EPA,2011).
5.4.4.4 Method
MethaneEmissionsfromAnaerobicLagoons,RunoffHoldingPonds,StorageTanksTheSommermodel(Sommeretal.,2004)isusedastheestimationmethodforCH4emission(Rotzetal.,2011b).DailyCH4emissionsareestimatedasafunctionofmanuretemperatureandthevolatilesolidsinmanureplacedintoliquidstorages.TheparametersfortheestimationarelistedinTable5‐28.
aDrymanurereferstomaterialremainingafterremovalofwater.Itisdeterminedthroughtheevaporationofwaterfromthemanuresampleat103‐105°C.Forcedairovenisthemostcommonequipmenttomeasurethedrymatter.
ThedegradablefractionofthevolatilesolidsisdependentonthepotentialCH4yieldandthemaximumCH4producingcapacitiesandcanbecalculatedusingEquation5‐32.Thefractionofnondegradablevolatilesolids(materialthatisnotbrokendownbymicroorganisms)iscalculatedfromthetotalvolatilesolidscontentanddegradablefractionofthevolatilesolids,asdescribedbyEquation5‐33.TheB0valuesareobtainedfromtheIPCC(2006)andarelistedinTable5‐19.
Equation5‐31:UsingtheSommerModeltoCalculateDailyCH4Emissions
.
Where:
ECH4 =Methaneemissionperday(kgCH4day‐1)
m =Totaldrymanureperday(kgdrymanureday‐1)a
0.024 =DimensionlessfactortomodifytheSommermodelbasedonVS
VSdandVSnd =DegradableandnondegradableVSinthemanure,respectively (kg(kgdrymanure)‐1)
b1andb2 =Ratecorrectingfactors(dimensionless)
A =Arrheniusparameter(gCH4(kgVS)‐1hr‐1)
E =Activationenergy(Jmol‐1)
R =Gasconstant(JK‐1mol‐1)
T =Storagetemperature(K)
η =Collectionefficiencyofdifferentliquidstoragecategories
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Thecollectionefficiency(η)dependsondifferentliquidstoragecategoriesof:1)coveredstoragewithacrustformedonthesurface;2)coveredstoragewithoutacrustformedonthesurface;3)uncoveredstoragewithacrustformedonthesurface;and4)uncoveredstoragewithoutacrustformedonthesurface.AcrustallowsairandCH4toberetainedonthesurfaceofthemanurestorageandincreasesthepotentialforoxidationofCH4(Hansenetal.,2009;Nielsenetal.,2010).Whenacrustdoesnotform,CH4isdirectlyemittedwithoutrapidoxidation.Forcattleslurryandpigslurry,degradableandnondegradablevolatilesolids(asafractionofVST)aregiveninTable5‐28.
Table5‐27:ParametersforEstimatingCH4EmissionfromLiquidManureStorage
Parameters Cattle Swine
Arrheniusconstant(ln(A))–gCH4(kgVS)‐1hr‐1 43.33 43.21
Activationenergy(E)–Jmol‐1 1.127×105 1.127×105
Gasconstant(R)–JK‐1mol‐1 8.314 8.314
RatecorrectionfactorforVSd(b1) 1 1
RatecorrectionfactorforVSnd(b2) 0.01 0.01
Potentialmethaneyieldofthemanure(ECH4,pot)(kgCH4/kgVS) 0.48 0.50
Collectionefficiency(η)
Coveredstoragewithacrustformonthesurfacea 1 1
Coveredstoragewithoutacrustformonthesurfacea 1 1
Uncoveredstoragewithacrustformonthesurfaceb 0 0
Uncoveredstoragewithoutacrustformonthesurfacec ‐0.4 ‐0.4Source:Sommeretal.(2004)andIPCC(2006).aCH4gasfromcoveredstoragewithacrustformonthesurfaceiscollectedandflared.bUncoveredstoragewithacrustformonthesurfaceisusedforthederivationofEquation5‐22.cTheemissionforuncoveredstoragewithoutacrustis40percentgreaterthanuncoveredstoragewithacrust,sothecollectionefficiencyforthiscaseis‐40percent.
Equation5‐32:CalculatingtheDegradableFractionoftheVolatileSolids
,
Where:
VSd =DegradableVSfractionsinthemanureonagivenday(kg(kgdrymanure)‐1)
VST =Volatilesolidscontentinthestorageonagivenday(kg(kgdrymanure)‐1)
B0 =MaximumCH4producingcapacities(kgCH4(kgVS)‐1)
ECH4,pot =PotentialCH4yieldofthemanure(kgCH4(kgVS)‐1)
Equation5‐33:CalculatingtheNon‐DegradableFractionoftheVolatileSolids
Where:
VSdandVSnd =DegradableandnondegradableVSfractionsinthemanureonagivenday (kg(kgdrymanure)‐1),respectively
VST =Volatilesolidscontentinthestorageonagivenday (kg(kgdrymanure)‐1)
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Table5‐28:DegradableandNondegradableVolatileSolidsforCattleandSwineManure
TypeofManure VSd/VST VSnd/VST
Cattleliquidmanure 0.46 0.54
Swineliquidmanure 0.89 0.11Source:Mølleretal.(2004).
NitrousOxideEmissionsfromAnaerobicLagoon,RunoffHoldingPond,StorageTanksNitrousoxideemissionsfromliquidmanurestoragetypicallyrepresentarelativelysmallportionoftheN2Oemissionsfromfarms.MoststudiesindicatethecriticalityofthecrustfortheformationandemissionofN2O(PetersenandSommer,2011).Therefore,N2Oemissionsfromliquidmanurestorageareestimatedasafunctionoftheexposedsurfaceareaofthemanurestorageandthepresenceofacrustonthesurface.
TheemissionfactorofN2Oisdependentoncrustformationontheliquidstorage.Thecrustallowsairtoberetainedonthesurfaceofthemanurestorageandincreasesthepotentialfornitrificationanddenitrification(Hansenetal.,2009;Nielsenetal.,2010).Whenacrustdoesnotform,oxygenisnotretainedontheliquidsurfacewithnitrogenouscompounds,andthereforenoN2Oisformedandemitted.TheemissionfactorsofN2OfordifferentliquidstoragemethodsarelistedinTable5‐29.
Table5‐29:EmissionFactorofN2OforLiquidStoragewithDifferentCrustFormation
TypeofLiquidStorage EFN2O,man(gN2O/m2/day)
Uncoveredliquidmanurewithcrust 0.8
Uncoveredliquidmanurewithoutcrust 0
Coveredliquidmanure 0Source:Rotzetal.(2011a).
Equation5‐34:CalculatingN2OEmissionsfromLiquidManureStorage
Where:
EN2O =Nitrousoxideemissionsperday(kgN2Oday‐1)
EFN2O =EmissionrateofN2O(gN2Om‐2day‐1)
Asurface =Exposedsurfaceareaofthemanurestorage(m2)
1,000 =Conversionfactorforgramstokilograms
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5.4.5 AnaerobicDigesterwithBiogasUtilization
5.4.5.1 OverviewofAnaerobicDigesterwithBiogasUtilization
OneofthemostcommonlydiscussedwastemanagementalternativesforGHGreductionandenergygenerationisanaerobicdigestion.Anaerobicdigestionisanatural,biologicalconversionprocessthathasbeenproveneffectiveatconvertingwetorganicwastesintobiogas(approximately60percentCH4and40percentCO2).Biogascanbeusedasafuelsourceforengine‐generatorsets,producingrelativelycleanelectricitywhilealsoreducingsomeoftheenvironmentalconcernsassociatedwithmanure.Thedigestercanbeassimpleasacoveredanaerobiclagoon(Gould‐WellsandWilliams,2004)orassophisticatedasthermophilicormediamatrix(attachedgrowth)digesters(Cantrelletal.,2008a).Thereareawidevarietyofanaerobicdigestionconfigurations,suchascontinuousstirredtankreactor(CSTR),coveredlagoon,plug‐flow,temperaturephased,upflowanaerobicsludgeblanket(UASB),packed‐bed,andfixedfilm.Thedigestionisalsocategorizedbasedonculturetemperature:thermophilicdigestioninwhichmanureisfermentedatatemperatureofaround55°C,ormesophilicdigestionatatemperatureofaround35°C.Amongthesetechnologies,CSTR,plug‐flow,andcoveredlagoon,allundermesophilicconditions,arethemostoften‐usedmethods.
Duringanaerobicdigestion,agroupofmicrobesworktogethertoconvertorganicmatterintoCH4,
CO2,andothersimplemolecules.Themainadvantagesofapplyinganaerobicdigestiontoanimalmanuresareodorreduction,electricitygeneration,andthereductionofGHGemissionsandmanure‐bornepathogens.Anaerobicdigestionisalsoanexcellentpre‐treatmentprocessforsubsequentmanuretreatmenttoremoveorganicmatterandconcentratephosphorus.ConsideringthesmallamountofN2Oexistinginbiogas,N2Oemissionsarenotestimatedfortheanaerobicdigestionofliquidmanure.
Thechallengesassociatedwithanaerobicdigestionrelatetoinitialcapitalcost,operation,andmaintenanceandothergasesthatmaybegenerated(e.g.,nitricoxides).Theeconomicsrelatetoaccesstotheelectricalgridandsufficientgreen‐electricityoffsetstomaketheoperationprofitable.Profitableconditionsarerelativelyscarce.Finally,thedigestersludgemustbemanaged.Anotherconversionalternativewithenergycreationpotentialisthermochemicalconversion(Cantrelletal.,2008a).Systemsthatusethermochemicalconversionstosyngases,bio‐oil,andbiocharforelectricityandfuelareemerging,butarenotyetestablished.
SinceananaerobicdigestionsystemconvertsorganiccarboninmanureintoCH4andsubsequentlycombustsCH4intoCO2,theGHGemissionsfrommanureanaerobicdigestionoperationaremainly
MethodforEstimatingEmissionsfromManureStorageandTreatment–AnaerobicDigesterwithBiogasUtilization
Methane
IPCCTier2usingCleanDevelopmentMechanismEFsfordigestertypestoestimateCH4leakagefromdigesters.
AnaerobicdigestersystemsconvertorganicmatterinmanureintoCH4andsubsequentlycombustCH4intoCO2.
GasleakagefromdigestersisthemainsourceofGHGemission. LeakageofCH4fromtheanaerobicdigestersystemisestimated.
NitrousOxide N2Oleakagefromdigestersisfairlysmallandnegligible.
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fromtheleakageofdigesters.TheleakageofCH4canbeestimatedbasedontheIPCCTier2approachincombinationwithtechnology‐specificemissionfactors.
5.4.5.2 RationaleforSelectedMethod
TheIPCCequationistheonlyavailablemethodforestimatingCH4emissionfromdigesters.Thismethodologybestdescribesthequantitativerelationshipamongactivitydataattheentitylevelandtakesintoaccountthespecifictechnologyemployed.
5.4.5.3 ActivityData
InordertoestimatetheCH4leakagefromanaerobicdigestion,thefollowinginformationisneeded:
Animaltype Totaldrymanureintothedigester Volatilesolidsinthemanure Digestertemperatures
5.4.5.4 AncillaryData
AncillarydataforanaerobicdigestioneffluentareneededforfurtherestimationofCH4andN2Oemissionsfrompost‐treatmentapproachessuchasaerobicoranaerobiclagoons,nutrientremovaloperations,etc.Thus,thenecessarydatafortheeffluentincludeeffluentflowrate,totalsolids,volatilesolids,chemicaloxygendemand,effluenttemperature,environmentaltemperature,liquid/solidseparationmethods,andtotalnitrogen.
5.4.5.5 Method
Equation5‐35describestheIPCCTier2approachforestimatingCH4emissionsforanaerobicdigesters.TheCH4generatedfromdigestersisassumedtobeflaredorusedasabiogas;theonlyemissionsfromdigestersarefromsystemleakage.
TheB0valuesareobtainedfromtheIPCC(2006)andarelistedinTable5‐19.TheemissionfactorsfortheamountofCH4leakagebytechnologyarelistedinTable5‐30.
Equation5‐35:IPCCTier2ApproachforEstimatingCH4 Emissions
.,
Where:
ECH4 =CH4emissionsperday(kgCH4day‐1)
m =Totaldrymanureperday(kgday‐1)
VS =Volatilesolids(kgVS(kgdrymanure)‐1)
B0 =MaximumCH4producingcapacityformanurefromdifferentanimal (m3CH4(kgVS)‐1)
0.67 =Conversionfactorfromweighttovolumeofmethane(kgCH4m‐3)
EFCH4,leakage=EmissionfactorforthefractionofCH4producedthatleaksfromtheanaerobicdigester(%)
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Table5‐30:EmissionFactorsfortheFractionofMethaneLeakingfromDigesters
DigesterConfigurations EFCH4,leakage(%)
Digesterswithsteelorlinedconcreteorfiberglassdigesterswithagasholdingsystem(eggshapeddigesters)andmonolithicconstruction
2.8
UASBtypedigesterswithfloatinggasholdersandnoexternalwaterseal 5Digesterswithunlinedconcrete/ferrocement/brickmasonryarchedtypegasholdingsection;monolithicfixeddomedigesters 10
Otherdigesterconfigurations 10Source:CDM(2012).
5.4.6 CombinedAerobicTreatmentSystems
Dealingwiththetotaltreatmentofwastewaterfromeitherswineordairyiscomplex,becausetheliquidandsolidphasesmustbetreated.Inmunicipalsewagetreatmentsystems,thewastewaterisverydilutesothetreatmentofthebiochemicaloxygendemandbyaerationisafundamentalprocess.Incontrast,thesolidscontentoflivestockwastewaterisquitehigh,asisthebiochemicaloxygendemand.Consequently,thecostofstabilizingthebiochemicaloxygendemandwithaerationhasproventobeuneconomical.AsuccessfulsolutiontothisproblemwasdevelopedbyVanottietal.(2007),whousedpolyacrylamideflocculationtoremovemorethan90percentofthesolids(VanottiandHunt,1999;Vanottietal.,2002).Thesolidfractionwasthencomposted(Vanotti,2006).Theremainingliquidwastransferredtoaseparatedwatertankwhereitwassubsequentlyaerated(VanottiandHunt,2000;Vanottietal.,2007;VanottiandSzogi,2008).Duringthesetwophasesoftreatment,morethan90percentoftheGHGemissionsfromstandardanaerobiclagoontreatmentwereavoided(Vanottietal.,2008).Theavoidancewasachievedbyaerobictreatmentofthesolidsviacompostingandnitrification/denitrificationintheliquideffluent.
Afternitrification/denitrification,thetreatedeffluentmovestothesettlingtankandsubsequentlyintothephosphorustreatmentchamber.Herethewastewater,whichhaslowalkalinity,isamendedwithliquidlime,andthepHisraisedtoapproximately10.InthepresenceofhighpHandcalcium,thephosphorusisprecipitatedandthepathogensarekilled(Vanottietal.,2003;Vanottietal.,2005;Vanottietal.,2009).Thetreatedwastewateristhenrecycledintothehouses.Thisprocessprovidesahealthierenvironmentforthepigs(Vanottietal.,2009).Thesystemmustbeoperatedtoensureproperandtimelyflushingofthehouse.Thepolyacrylamideadditionandthesolidsseparationunitsmustbeoperatedproperly.Aerationofthenitrificationtankmustbemaintained,asmusttheadditionofliquidlime.Thepumpsthatmaintaintheinternalrecyclingmustalsobemaintainedandoperatedcorrectly.ThissystemistheonlytreatmentsystemtomeetandbecertifiedforexpansionofswineproductioninNorthCarolina.
MethodforEstimatingEmissionsfromCombinedAerobicTreatmentSystems
Methodistoutilize10percentoftheemissionsresultingfromestimationofemissionsfromLiquidManureStorageandTreatment–AnaerobicLagoons,RunoffHoldingPonds,andStorageTanks.
Methodbasedonresearchfindingsthatsystemsavoid90percentoftheGHGemissionsfromstandardanaerobiclagoontreatment.
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Toestimateemissionsforcombinedaerobictreatmentsystems,themethodologyforanaerobiclagoons,runoffholdingponds,andstoragetanksisappliedtothesystem.GasemissionsofCH4andN2Oareestimatedusing10percentofthevaluesforemissionsfromanaerobiclagoontreatment.
5.4.7 Sand‐ManureSeparation
Sandisoneofthestandardmaterialsfordairycowbedding.Itprovidessuperiorcowcomfort,environmentforudderhealth(andconsequentlybettermilkquality),andtractionwhencomparedwithorganicbeddingmaterials.Sandseparationsystemscanbeclassifiedasmechanicalseparationandsedimentationseparation.Sedimentationseparationusesdilutionwaterandgravitytoallowsandtopassivelysettleinsandtraps.Duetothehighorganicmaterialcontentcontainedinthesettledsand,thesandrecoveredfromthesandtrapneedstobedrainedmultipletimesanddriedpriortoreuse.Mechanicalsand‐manureseparationsystemsuserecycledliquidmanureandaerationtosuspendmanuresolids,settlesandatthebottomoftheseparator,andrecoverthesandusingaheavydutyauger.Sandisgenerallydischargedwithlessthantwopercentorganicmatter.Themechanicallyseparatedsandcanbereusedforbedding.
Sincesand‐manureseparationisrelativelyquick(comparedwithotherstorageandtreatmentmethods),GHGemissionsfromtheoperationareminimal.TheprocessofseparatingsandandmanureisnotassumedtocontributetoGHGemissions.Aftersand‐manureseparation,theseparatedliquidmanureistreatedastheinfluentforthenextstepofstorageandtreatmentoperations.ThevariousstorageandtreatmentoperationoptionsareshowninFigure5‐7.Theparametersofvolatilesolids,totalnitrogen,organicnitrogen,andmanuretemperatureoftheseparatedliquidmanureshouldbemeasured,andusedastheinputstoestimateemissionsofGHGs.
5.4.8 NutrientRemoval
Nitrogenandphosphorusaretheprimaryelementsthatcauseeutrophicationinsurfacewaters.WithincreasedFederal,Stateandlocalattentiononnon‐pointwastesources,moreandmoreanimaloperationswilllikelyusenutrientremovalapproachestotreatliquidmanurebeforelandapplicationandotheruses.Comparedtophosphorus,nitrogeninmanurecontributestoN2Oemission;removingitcansignificantlyalleviateemissions.NitrogeninmanurecomprisesNH3,particulateorganicnitrogen,andsolubleorganicnitrogen.Fivemainnitrogenremoval
MethodforEstimatingEmissionsfromLiquidManureStorageandTreatment–Sand/ManureSeparation
NomethodisprovidedasGHGemissionsarenegligiblefromthesand/manureseparationprocess.However,resultingvolatilesolids,totalnitrogen,organicnitrogen,andmanuretemperatureoftheseparatedliquidmanureshouldbemeasuredandusedastheinputstoestimateemissionsofGHGsforsubsequentstorageandtreatmentoperations.
MethodforEstimatingEmissionsfromLiquidManureStorageandTreatment–NutrientRemoval
NotestimatedduetolimitedquantitativeinformationonGHGsfromnitrogenremovalprocesses.
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approaches—BiologicalNitrogenRemoval(BNR),Anamox,NH3stripping,ionexchange,andstruvitecrystallization—havebeenappliedformunicipalandindustrialwastewater,aswellasforanimalwastestreams.BecauseN2Ooriginatesfromnitrogensources,quantificationofnitrogenremovalisimportanttoestimateemissionsfromanimalmanure.
Becausemostnitrogenremovalmethodsforliquidmanurearecurrentlyintheresearchanddevelopmentstage,verylittlequantitativeinformationisavailableonthenitrogenremovalmethodsmentionedaboveforanimalmanureunderdifferentoperationconditions.Thesuggestedestimationmethodistoconsidertheliquidmanureafternutrientremovalastheinfluentforstorageandtreatmentapproachesthatentitieswillusetofurthertreatliquidmanure.Measurementsofvolatilesolids,totalnitrogen,organicnitrogen,andmanuretemperatureofthetreatedliquidmanureareneededtoestimateCH4andN2Oemissions.
5.4.9 Solid–LiquidSeparation
Solid–liquidmanureseparationhasbeenusedwidelybydairyfarms.Onepurposeofsolid–liquidseparationistophysicallyseparateandremovethelargersolidsfromliquidmanureinordertostoreandtreatthemseparately.Theavailablecommercialmethodsincludegravitysedimentationandmechanicalseparation(withorwithoutcoagulationflocculation).Sedimentationandmechanicalseparationwithoutcoagulationflocculationarethemostpopularmethodsusedbyanimalfarms.Similartosand–liquidmanureseparation,GHGemissionsfromtheoperationareminimal;however,separationhasanimpactonnutrientdistributioninseparatedsolidandliquidmanure,whichwillinfluenceGHGemissionsfromthenextstageofmanurestorageandtreatmentforsolidandliquidmanure.Theseparatedliquidmanureistreatedastheinfluentforthenextstepofstorageandtreatmentoperations.ThepossiblestorageandtreatmentoptionsaredelineatedinFigure5‐7.
Theparametersoftotalsolids(drymanure),totalnitrogen,organicnitrogen,andmanuretemperatureoftheseparatedliquidandsolidmanureshouldbemeasured,andusedastheinputstoestimateGHGsemissioninthesubsequentstorageandtreatmentoperations.Thedistributionoftotalsolidsaftersolid–liquidseparationfortypicalmechanicalseparatorsarelistedinTable5‐317(FordandFleming,2002).
Table5‐31:EfficiencyofDifferentMechanicalSolid‐LiquidSeparation
SeparationTechnique
ManureType
ScreenSize(mm)
Influent(%DM)
TotalSolidRemoval
Efficiency(%)Source
ScreenStationaryinclinedscreen
Swine 1.0 0.0‐0.7 35.2 Shuttetal.(1975)Beef 0.5 0.97‐4.41 1‐13 Heggetal.(1981)Dairy 1.5 3.83 60.9 Chastainetal.(2001)
Vibratingscreen
Swine 0.39 0.2‐0.7 22.2 Shuttetal.(1975)Beef 0.52‐1.91 5.5‐7.4 4‐44 GilbertsonandNienaber(1978)
MethodforEstimatingEmissionsfromLiquidManureStorageandTreatment–Solid–LiquidSeparation
NomethodisprovidedasGHGemissionsarenegligible.However,resultingvolatilesolids,totalnitrogen,organicnitrogen,andmanuretemperatureoftheseparatedliquidandsolidmanureshouldbemeasuredandusedastheinputstoestimateemissionsofGHGsandNH3forsubsequentstorageandtreatmentoperations.
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SeparationTechnique
ManureType
ScreenSize(mm)
Influent(%DM)
TotalSolidRemoval
Efficiency(%)Source
Beef 0.64‐1.57 1.55‐3.19 6‐16 Heggetal.(1981)Dairy 0.64‐1.57 0.95‐1.9 8‐16 Heggetal.(1981)Swine 0.64‐1.57 1.55‐2.88 3‐27 Heggetal.(1981)Swine 0.10‐2.45 1.5‐5.4 11‐67 Holmbergetal.(1983)
Rotatingscreen
Beef 0.75 1.56‐3.68 4‐6 Heggetal.(1981)Dairy 0.75 0.52‐2.95 0‐14 Heggetal.(1981)Swine 0.75 2.54‐4.12 4‐8 Heggetal.(1981)
In‐channelflightedconveyorscreen
Dairy 3 7.1 4.22 Mølleretal.(2000)
Swine 3 5.66 25.8 Mølleretal.(2000)CentrifugalCentrifuge Beef 7.5 25 Glerumetal.(1971)Centrisieve Swine 5‐8 30‐40 Glerumetal.(1971)
Decantercentrifuge
Beef 6.9 64 Chiumentietal.(1987)Beef 6.0 45 Chiumentietal.(1987)Swine 7.58 66 Glerumetal.(1971)Swine 1.9‐8.0 47.4‐56.2 Sneathetal.(1988)
Liquidcyclone
Swine 26.5 Shuttetal.(1975)
Filtration/pressing
RollerpressSwine 5.2 17.3 Posetal.(1984)Dairy 4.8 25 Posetal.(1984)Beef 4.5 13.3 Posetal.(1984)
BeltpressDairy 1‐2 7.1 32.4 Mølleretal.(2000)Swine 1‐2 5.7 22.3 Mølleretal.(2000)
Screwpress
Swine 5 16 Chastainetal.(1998)Swine 1‐5 15‐30 Converseetal.(1999)Dairy 1‐10 15.8‐47 Converseetal.(1999)Dairy 2.6 23.8 Converseetal.(1999)Dairy 4.9 33.4 Converseetal.(1999)
Fournierrotarypressa
Swine 85 FordandFleming(2002)Fournier(2010)
Rotaryvacuumfilter Swine 7.5 51 Glerumetal.(1971)
Pressurefilter Beef 7 76 Chiumentietal.(1987)ContinuousBeltMicroscreeningUnit
Swine 2‐8 40‐60 Fernandesetal.(1988)aWithpolymeraddition.
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5.4.10 ConstructedWetland
Globally,constructedwetlandsareusedforthetreatmentofwastewaters,captureofsediments,
anddrainagewaterabatement(Hammer,1989;KadlecandKnight,1996;Tanneretal.,1997;Huntetal.,2002;Huntetal.,2003;Piceketal.,2007;HarringtonandMcInnes,2009;Mustafaetal.,2009;Soosaaretal.,2009;Elgoodetal.,2010;HarringtonandScholz,2010;VanderZaagetal.,2010;Chenetal.,2011;Lockeetal.,2011;TannerandHeadley,2011;TannerandSukias,2011;Vymazal,2011).Constructedwetlandsaregenerallyclassifiedassub‐surfaceorsurfaceflowwetlands(KadlecandKnight,1996).Thesub‐surfacewetlandstypicallyconsistofwetlandplantsgrowinginabedofhighlyporousmedia,suchasgravelorwoodchips.Theyarecommonlyusedtoimprovedrainagewaterquality.Thesewetlandsaregenerallyrectangularinshapeandonetotwometersindepth.Thereislackofagreementabouttherelativeimpactofmicrobialandplantprocessesinthefunctionofsubsurfacewetlands,includingGHGproductionandemissions.However,itisaccuratetosaythatplantsandmicrobesaretypicallyinterdependentlyinvolved(Piceketal.,2007;Zhuetal.,2007;Wangetal.,2008;Faubertetal.,2010;Luetal.,2010;TannerandHeadley,2011).Themicrobialcommunityadvancesbiogeochemicalprocesses(Tanneretal.,1997;Huntetal.,2003;Zhuetal.,2007;Dodlaetal.,2008;Faulwetteretal.,2009),whiletheplantcommunityadvancestransportedoxygenintothedepthofthewetlands,providesrootsurfacesforrhizospherereactions,andventsgasestotheatmosphere.Theplantprocessesaresignificantlyaffectedbyplantcommunitycompositionandweatherconditions(Towleretal.,2004;SteinandHook,2005;Steinetal.,2006;Zhuetal.,2007;Wangetal.,2008;Tayloretal.,2010).
Surfaceflowwetlandshaveamuchmoredirectinterchangewiththeatmosphereforthesupplyofoxygenandnitrogen,aswellastheemissionsofGHGs.Theycanbevariableinshapeandaregenerallylessthan0.5metersdeep.Surfacewetlandsminimizecloggingproblems,buttheycanhavesignificantlossoftreatmentasaresultofchannelflow.Therearereasonablyfunctionalmodelsforwetlanddesignoptimizedforeithercarbonornitrogenremoval(Stoneetal.,2002;Stoneetal.,2004;Steinetal.,2006;Steinetal.,2007a).ThemanagementofGHGs(principallyCH4andN2O)fromtreatmentwetlandsissomewhatsimilartomanagingGHGsinrice(Freemanetal.,1997;Tanneretal.,1997;Feyetal.,1999;Johanssonetal.,2003;Manderetal.,2005a;Manderetal.,2005b;TeiterandMander,2005;Piceketal.,2007;Maltais‐Landryetal.,2009;Wuetal.,2009).
Ofparticularimportanceisthemaintenanceofwetlandoxidative/reductivepotentialconditionssufficientlypositivetoavoidCH4production(Tanneretal.,1997;InsamandWett,2008;SeoandDeLaune,2010).Thisrequireshigherlevelsofoxygenandlowerlevelsofavailablecarbon.IthasbeenreportedthatthefluxesofN2OandCH4fromtreatmentwetlandsaregenerallybelow10mgN2O‐Nm‐2d‐1and300mgCH4‐Cm‐2d‐1(Manderetal.,2005a;Søviketal.,2006).ThemanagementofN2Oemissionsiscomplicatedbythefactthatnitratesareoftenpresentinthewastewatersordrainagewaters.Thisnitratewillbedenitrifiedundertheprevailinganaerobicconditionofthetreatmentwetlands—itisoneoftreatmentwetland’scriticalfunctions.However,itisimportantthatthepreponderanceofdenitrificationproceedstocompletion,withtheultimateproductionofinertdi‐nitrogengas.Completedenitrificationrequireshighercarbon/nitrogenratios
MethodforEstimatingEmissionsfromLiquidManureStorageandTreatment–ConstructedWetland
Currentlynomethodisprovidedtoestimategasemissionfromconstructedwetlandofanimalmanure,althoughGHGsinksarenotedtolikelybegreaterthanCH4andN2Oemissions,whichareconsiderednegligible.
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(Klemedtssonetal.,2005;Hwangetal.,2006;Huntetal.,2007).Thus,thereisanimportantbalancebetweensufficientcarbonforcompletedenitrificationandcopiouscarbonthatcandrivewetlandsintothelowreduction/oxidationconditionsassociatedwithCH4production.
Estimationmethodsareverycomplicatedandcase‐based.Inanapproximateestimationmannerthatconsiderswetlandsverysimilartocropland,treatmentwetlandsofanimalmanureareGHGsinksmorethansources.TheCH4andN2Oemissionfromwetlandtreatmentofanimalmanurecouldbenegligible.Thecriticalactivitydataincludehydraulicload;inflowwatercomposition,especiallycarbonandnitrogen;pretreatmentssuchassolidsremovalornitrification;amendments;anddryingcycles.Criticalancillarydataincluderainfall,temperature,windspeed,stormevents,changesinlivestockstockingrates,cropping/tillagesystems,andfertilizationtiming/rates.
5.4.11 Thermo‐ChemicalConversion
Combustion,themostprimitiveandexothermicformofthermochemicaltreatmentoflivestockwaste,hasbeeninusesinceantiquity;however,itsuseforlarge‐scalelivestockwastetreatmenthasgenerallybeenhamperedbyeconomic,health,andenvironmentalqualityissues(Florinetal.,2009).Principalamongtheseissueshasbeencomponentsthatdegradeairquality,includingGHGs(mainlyCO2).Nonetheless,thermochemicaltreatmentoflivestockmanurehasattributesthatcontinuetoattracteffortstomakeiteconomicallyandenvironmentallyeffective(Ramanetal.,1980;Heetal.,2000;Heetal.,2001;Ocfemiaetal.,2006;Roetal.,2007;Cantrelletal.,2008a;Cantrelletal.,2008b;Powlsonetal.,2008;Cantrelletal.,2009;Dongetal.,2009;Jinetal.,2009;Roetal.,2009;Xiuetal.,2009;Cantrelletal.,2010a;Cantrelletal.,2010b;Stoneetal.,2010;Wangetal.,2011;Xiuetal.,2011).
Recently,pyrolysis/gasificationhasreceivedmuchinterestforitstreatmentoflivestockwaste.Therehavealsobeenadvancesinthecleaningofexhaustgases(Heetal.,2001;Roetal.,2007;Cantrelletal.,2008a;Dongetal.,2009;Xiuetal.,2009;Xiuetal.,2011).Pyrolysis/gasificationoffersthreeprincipalendproducts:syngas,bio‐oil,andbiochar(Cantrelletal.,2008a;Xiuetal.,2011).Thequalityandquantityofendproductswillvarywithfeedstock,exposuretime,andpyrolysis/gasificationtemperature.Thesyngascanbeusedfordirectcombustionortorunanelectricalgenerator(Roetal.,2010).ItcanalsobeusedviaFischer‐Tropschconversionforproductionofliquidfuel(Cantrelletal.,2008a).Pyrolysis/gasificationforsyngasandeventualliquidfuelproductionisaveryattractivepotentialbusinessmodelforspecificagriculturalfuels.
IntermsofGHGemission,treatmentoffluegasfromcombustionandutilizationofsyngasfrompyrolysis/gasificationarecritical.Thethermalprocesseswithafluegasclean‐upunitandsyngasutilizationunitshouldminimizetheGHGemissionfromthethermalconversionprocesses.
InordertoestimatethedailyemissionsofCH4andN2Othefollowinginformationisneeded:typeofthermalconversionprocesses;detailedinformationontheprocess,suchaswith/withoutfluegasclean‐upunitorsyngasutilizationunit;inflowcomposition,suchasmoisture,carbon,andnitrogen;andmassflowthroughtheprocess,includingmassin,fluegas/syngas,andash/biochar.Themeasurementscanbebasedondietarychangesorseasonaltimeframe,whichisdecidedbyindividualfarmentity.However,duetothedynamicnatureofmanurepilesandtherapidchangesthatcanoccurinchemicalandphysicalcomposition,frequentmeasurementsarerecommendedtoensureaccuracyoftheestimation.Thetotalenergybalanceofthesystemshouldalsobeknown.For
MethodforEstimatingEmissionsfromSolidManureStorageandTreatment–ThermochemicalConversion
NomethodisprovidedasCH4andN2Oemissionsareconsiderednegligible.
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instance,thecarboncreditsofbiocharcannotbeclaimedwhileignoringtheenergyrequiredtocreatethebiochar.Theeffectivenessoftheexhaustgascleaningprocessinremovingairqualitydegradingcomponentsmustbecertified.
Duetothenatureofthermalconversion,muchloweremissions(CH4andN2O,)aregeneratedfromthethermalconversioncomparedwithotherstorageortreatmentmethods.TheCH4andN2Oemissionsfromcompletethermalconversionprocessesarerelativelysmallandnegligible.
5.4.12 LimitationsandUncertaintyinManureManagementEmissionsEstimates
Fortemporaryandlong‐termstorage,composting,andaerobiclagoons,theIPCCTier2methodologyisusedtoestimateCH4emissions.ThemaximumCH4productioncapabilities(B0)forruminantanimalsareU.S.specificvaluesfromtheU.S.EPAInventoryofU.S.GHGEmissionsandSinks.IPCCestimatesthattheuncertaintyassociatedwiththesecountry‐specificfactorsis±20percent.B0valuesforotheranimalvaluesareIPCCdefaultsandhaveanassociateduncertaintyof±30percent.TheMCFsprovidedintheGuidelinesforsolid,slurry,andsolid/slurrymanurearefromtheIPCCGuidanceandhaveanestimateduncertaintyof±30percent.TheB0andMCFvaluesprovidedareintendedforuseatthenationallevel,thusapplicationofthesefactorsattheentitylevelmayresultinhigheruncertainty.
AmodifiedTier2approachisprovidedforestimatingCH4emissionsfromanaerobicdigesters.TheleakratesfordifferentdigestertypesistakenfromtheCleanDevelopmentMechanism’smethodologicaltoolforprojectandleakageemissionsfromanaerobicdigesters(CDM,2012).TheCleanDevelopmentMechanism’sleakratesarebasedonIPCC(2006),Fleschetal.(2011),andKurup(2003).TheleakageratetakenfromFleschetal.(2011)isbasedonmeasurementstakenfromanIntegratedManureUtilizationSysteminstalledinAlberta,Canada.Thesystemprocesses100metrictonsofmanuredailyandwasthemosttechnologicallyadvancedsystemavailableatthetimeofthestudy.ThestudiesperformedbyKurup(2003)werebasedonasystemlocatedinKerala,India.Nouncertaintyestimatesareprovidedfortheseleakrates;however,theactualleakrateofanentitymaydifferduetodifferencesintechnology,maintenance,orotherfactors.
TheSommermodel(Sommeretal.,2004)isrecommendedforestimatingCH4emissionsfromanaerobiclagoons,runoffholdingponds,andstoragetanks.SimilartotheIPCCTier2methodsusedforstockpiles,composting,andaerobiclagoons,theSommermodelrequiresB0valuesfromIPCC.ThedegradableandnondegradablevolatilesolidscanbecalculatedusingtheB0andpotentialCH4yieldoradefaultvaluefromMølleratal.(2004).ThedefaultvaluespresentedarebasedontypicalconcentrationsonDanishcattleandpigslurries;valuesdonotdifferentiatebetweentypeofcattleordietoftheanimalandthusthereishigherrelativeuncertaintyassociatedwithusingthedefaultvalues.
Sommeretal.(2004)performedananalysistodeterminethesensitivityofemissionestimatestowardsdifferentfactors.OnefactorconsideredistheeffectofslurrystoragetemperatureonCH4emissions.Sommeretal.(2004)appliedaveragemonthlytemperaturesforsevendifferentlocations(allNordiccountries)atconstantvolatilesolidsandmanagement.WhencomparedtothemodelresultsforDenmark(whicharecalibratedtocorrespondwithIPCCmethodology),theemissionsestimatesvariedfrom‐1to+36percentforpigslurryand‐23to+1percentforcattleslurry.GiventhattheclimaticconditionsoftheUnitedStatesdiffersfromNordiccountries,thevariationasaresultofslurrystoragetemperatureisexpectedtobegreater.
IPCCmethodologyormodifiedmethodologyisusedtoestimatetheN2Oemissionsfromtemporarystackandlong‐termstorage,composting,andaerobiclagoons.IPCCreportslargeuncertaintieswiththedefaultemissionfactorsapplied(‐50percentto+100percent).Theseemissionfactorswereintendedforuseatthenationallevelanddonottakeintoaccountvaryingtemperature,moisture
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content,aeration,manurenitrogencontent,metabolizablecarbon,durationofstorage,andotheraspectsoftreatmentfordifferententities,thustheuncertaintyisexpectedtobehigherthanreportedbyIPCC.
Themethodsrecommendthattheusersendmanuresamplestoalaboratorytoobtainanestimateofthevolatilesolids,NH3,andnitrogencontentofmanure.Ameasurementofmanurecharacteristicscanhelpminimizeuncertaintybyprovidinganentity‐specificvaluethattakesintoaccountanimalanddietcharacteristics.Iflaboratory‐testedvolatilesolidsvaluesarenotavailable,defaultvaluesfromtheAmericanSocietyofAgriculturalandBiologicalEngineers(ASABE)canbeapplied.ASABEprovidesdefaultmanurecharacteristicsbasedondatafrompublishedandunpublishedinformation.Thesevaluesarearithmeticaveragesandmaynotrepresentthedifferencesinanimalage,diet,usage,productivity,andmanagement.ThereisahigheramountofuncertaintyassociatedwiththeuseofASABEvaluesbutthereisnoquantifieduncertaintyprovidedforthesevalues.Notethatwithinthestandardcitedbelowthereareequationsprovidedthatallowforfarm‐specificvaluestobedeterminedbasedonanimalcharacteristicsanddietcomposition.Thetablebelowisintendedtoprovide‘average’values,butwherefarmdataareavailable,equationsshouldbeusedinordertoprovidemoreestimatesthatbetterreflectfarmconditionsandpractices.
AvailabledefaultvaluesanduncertaintyinformationisincludedinTable5‐32.
Table5‐32:AvailableUncertaintyDataforEmissionsfromManureManagement
Parameter
Abbreviation/Sym
bol
DataInputUnit
EstimatedValue
RelativeuncertaintyLow
(%
)
RelativeuncertaintyHigh
(%)
EffectiveLowerLimit
EffectiveUpperLimit
DataSource
TotalDryManure–BeefFinishingCattle
kgdrymanure/animal/day 2.4 ‐20 20 ASABE(2005)
TotalDryManure–BeefCow(confinement)
kgdrymanure/animal/day 6.6 ‐20 20 ASABE(2005)
TotalDryManure–BeefGrowingcalf(confinement)
kgdrymanure/animal/day 2.7 ‐20 20 ASABE(2005)
TotalDryManure–DairyLactatingcow
kgdrymanure/animal/day 8.9 ‐20 20 8.7 11.3 ASABE(2005)
TotalDryManure–DairyDrycow kgdrymanure/animal/day 4.9 ‐20 20 8.8 11.2 ASABE(2005)
TotalDryManure–DairyHeifer kgdrymanure/animal/day 3.7 ‐20 20 ASABE(2005)
TotalDryManure–DairyVeal118kg kgdrymanure/animal/day 0.12 ‐20 20 ASABE(2005)
TotalDryManure–HorseSedentary500kg
kgdrymanure/animal/day 3.8 ‐20 20 ASABE(2005)
TotalDryManure–HorseIntenseexercise500kg
kgdrymanure/animal/day 3.9 ‐20 20 ASABE(2005)
TotalDryManure–PoultryBroiler kgdrymanure/animal/day 0.03 ‐20 20 ASABE(2005)TotalDryManure–PoultryTurkey(male)
kgdrymanure/animal/day 0.07 ‐20 20 ASABE(2005)
TotalDryManure–PoultryTurkey(females)
kgdrymanure/animal/day 0.04 ‐20 20 ASABE(2005)
TotalDryManure–PoultryDuck kgdrymanure/animal/day 0.04 ‐20 20 ASABE(2005)TotalDryManure–Layer kgdrymanure/animal/day 0.02 ‐20 20 ASABE(2005)TotalDryManure–SwineNurserypig(12.5kg)
kgdrymanure/animal/day 0.13 ‐20 20 ASABE(2005)
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Parameter
Abbreviation/Sym
bol
DataInputUnit
EstimatedValue
RelativeuncertaintyLow
(%
)
RelativeuncertaintyHigh
(%)
EffectiveLowerLimit
EffectiveUpperLimit
DataSource
TotalDryManure–SwineGrowfinish(70kg)
kgdrymanure/animal/day 0.47 ‐20 20 ASABE(2005)
TotalDryManure–Swinegestatingsow200kg
kgdrymanure/animal/day 0.5 ‐20 20 ASABE(2005)
TotalDryManure–SwineLactatingsow192kg
kgdrymanure/animal/day 1.2 ‐20 20 ASABE(2005)
TotalDryManure–SwineBoar200kg
kgdrymanure/animal/day 0.38 ‐20 20 ASABE(2005)
Volatilesolids–BeefFinishingcattle VS kgVS/kgdrymanure 0.81 ‐25 25 ASABE(2005)Volatilesolids–BeefCow(confinement)
VS kgVS/kgdrymanure 0.89 ‐25 25 ASABE(2005)
Volatilesolids–BeefGrowingcalf(confinement)
VS kgVS/kgdrymanure 0.85 ‐25 25 ASABE(2005)
Volatilesolids–DairyLactatingcow VS kgVS/kgdrymanure 0.84 ‐25 25 ASABE(2005)Volatilesolids–DairyDrycow VS kgVS/kgdrymanure 0.85 ‐25 25 ASABE(2005)Volatilesolids–DairyHeifer VS kgVS/kgdrymanure 0.86 ‐25 25 ASABE(2005)
Volatilesolids–DairyVeal118kg VS kgVS/kgdrymanure ‐25 25 ASABE(2005)
Volatilesolids–HorseSedentary500kg
VS kgVS/kgdrymanure 0.79 ‐25 25 ASABE(2005)
Volatilesolids–HorseIntenseexercise500kg
VS kgVS/kgdrymanure 0.79 ‐25 25 ASABE(2005)
Volatilesolids–PoultryBroiler VS kgVS/kgdrymanure 0.73 ‐25 25 ASABE(2005)Volatilesolids–PoultryTurkey(male)
VS kgVS/kgdrymanure 0.8 ‐25 25 ASABE(2005)
Volatilesolids–PoultryTurkey(females)
VS kgVS/kgdrymanure 0.79 ‐25 25 ASABE(2005)
Volatilesolids–PoultryDuck VS kgVS/kgdrymanure 0.58 ‐25 25 ASABE(2005)Volatilesolids–Layer VS kgVS/kgdrymanure 0.73 ‐25 25 ASABE(2005)Volatilesolids–SwineNurserypig(12.5kg)
VS kgVS/kgdrymanure 0.83 ‐25 25 ASABE(2005)
Volatilesolids–SwineGrowfinish(70kg)
VS kgVS/kgdrymanure 0.8 ‐25 25 ASABE(2005)
Volatilesolids–Swinegestatingsow200kg
VS kgVS/kgdrymanure 0.9 ‐25 25 ASABE(2005)
Volatilesolids–SwineLactatingsow192kg
VS kgVS/kgdrymanure 0.83 ‐25 25 ASABE(2005)
Volatilesolids–SwineBoar200kg VS kgVS/kgdrymanure 0.89 ‐25 25 ASABE(2005)Totalnitrogenatagivenday–beeffinishingcattle
kgN/kgdrymanure 0.07 ASABE(2005)
Totalnitrogenatagivenday–beefcow(confinement)
kgN/kgdrymanure 0.03 ASABE(2005)
Totalnitrogenatagivenday–beefgrowingcalf(confinement)
kgN/kgdrymanure 0.05 ASABE(2005)
Totalnitrogenatagivenday–dairylactatingcow
kgN/kgdrymanure 0.05 ASABE(2005)
Totalnitrogenatagivenday–dairydrycow
kgN/kgdrymanure 0.05 ASABE(2005)
Totalnitrogenatagivenday–dairyheifer
kgN/kgdrymanure 0.03 ASABE(2005)
Totalnitrogenatagivenday–dairyveal118kg
kgN/kgdrymanure 0.13 ASABE(2005)
Totalnitrogenatagivenday–HorseSedentary500kg
kgN/kgdrymanure 0.02 ASABE(2005)
Totalnitrogenatagivenday–HorseIntenseExercise
kgN/kgdrymanure 0.04 ASABE(2005)
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Parameter
Abbreviation/Sym
bol
DataInputUnit
EstimatedValue
RelativeuncertaintyLow
(%
)
RelativeuncertaintyHigh
(%)
EffectiveLowerLimit
EffectiveUpperLimit
DataSource
Totalnitrogenatagivenday–poultry,broiler
kgN/kgdrymanure 0.04 ASABE(2005)
Totalnitrogenatagivenday–poultry,turkey(male)
kgN/kgdrymanure 0.06 ASABE(2005)
Totalnitrogenatagivenday–poultry,turkey(females)
kgN/kgdrymanure 0.06 ASABE(2005)
Totalnitrogenatagivenday–poultry,duck
kgN/kgdrymanure 0.04 ASABE(2005)
Totalnitrogenatagivenday–layer kgN/kgdrymanure 0.07 ASABE(2005)Totalnitrogenatagivenday–swinenurserypig(12.5kg)
kgN/kgdrymanure 0.09 ASABE(2005)
Totalnitrogenatagivenday–swinegrowfinish(70kg)
kgN/kgdrymanure 0.08 ASABE(2005)
Totalnitrogenatagivenday–swinegestatingsow200kg
kgN/kgdrymanure 0.06 ASABE(2005)
Totalnitrogenatagivenday–swinelactatingsow192kg
kgN/kgdrymanure 0.07 ASABE(2005)
Totalnitrogenatagivenday–swineboar200kg
kgN/kgdrymanure 0.07 ASABE(2005)
MethaneConversionFactor(MCF)a–DairyCow
MCF % ‐30 30 IPCC(2006)
MethaneConversionFactora–Cattle MCF % ‐30 30 IPCC(2006)MethaneConversionFactora–Buffalo MCF % ‐30 30 IPCC(2006)MethaneConversionFactora–MarketSwine
MCF % ‐30 30 IPCC(2006)
MethaneConversionFactora–BreedingSwine
MCF % ‐30 30 IPCC(2006)
MethaneConversionFactora–Layer(Dry)
MCF % ‐30 30 IPCC(2006)
MethaneConversionFactora–Broiler MCF % ‐30 30 IPCC(2006)MethaneConversionFactora–Turkey MCF % ‐30 30 IPCC(2006)MethaneConversionFactora–Duck MCF % ‐30 30 IPCC(2006)MethaneConversionFactora–Sheep MCF % ‐30 30 IPCC(2006)MethaneConversionFactora–Goat MCF % ‐30 30 IPCC(2006)MethaneConversionFactora–Horse MCF % ‐30 30 IPCC(2006)MethaneConversionFactora–Mule/Ass
MCF % ‐30 30 IPCC(2006)
MethaneConversionFactora–Buffalo MCF % ‐30 30 IPCC(2006)MethaneConversionFactora–Invesselmanurecomposting
MCF % ‐30 30 IPCC(2006)
MethaneConversionFactora–Staticpilemanurecomposting
MCF % ‐30 30 IPCC(2006)
MethaneConversionFactora–Intensivewindrow
MCF % ‐30 30 IPCC(2006)
MethaneConversionFactora–Passivewindrow
MCF % ‐30 30 IPCC(2006)
MaximumMethaneProducingCapacities–BeefReplacementHeifers
Bo m3CH4/kgVS 0.33 ‐20 20 U.S.EPA(2011)
MaximumMethaneProducingCapacities–DairyReplacement Bo m3CH4/kgVS 0.17 ‐20 20 U.S.EPA(2011)
MaximumMethaneProducingCapacities–MatureBeefCows
Bo m3CH4/kgVS 0.33 ‐20 20 U.S.EPA(2011)
MaximumMethaneProducingCapacities–Steers(>500lbs)
Bo m3CH4/kgVS 0.33 ‐20 20 U.S.EPA(2011)
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Parameter
Abbreviation/Sym
bol
DataInputUnit
EstimatedValue
RelativeuncertaintyLow
(%
)
RelativeuncertaintyHigh
(%)
EffectiveLowerLimit
EffectiveUpperLimit
DataSource
MaximumMethaneProducingCapacities–Stockers(All)
Bo m3CH4/kgVS 0.17 ‐20 20 U.S.EPA(2011)
MaximumMethaneProducingCapacities–CattleonFeed
Bo m3CH4/kgVS 0.33 ‐20 20 U.S.EPA(2011)
MaximumMethaneProducingCapacities–DairyCow
Bo m3CH4/kgVS 0.24 ‐20 20 U.S.EPA(2011)
MaximumMethaneProducingCapacities–Cattle
Bo m3CH4/kgVS 0.19 ‐20 20 U.S.EPA(2011)
MaximumMethaneProducingCapacities–Buffalob
Bo m3CH4/kgVS 0.1 IPCC(2006)
MaximumMethaneProducingCapacities–MarketSwine Bo m3CH4/kgVS 0.48 ‐30 30 IPCC(2006)
MaximumMethaneProducingCapacities–BreedingSwine
Bo m3CH4/kgVS 0.48 ‐30 30 IPCC(2006)
MaximumMethaneProducingCapacities–Layer(dry) Bo m3CH4/kgVS 0.39 ‐30 30 IPCC(2006)
MaximumMethaneProducingCapacities–Layer(wet)
Bo m3CH4/kgVS 0.39 ‐30 30 IPCC(2006)
MaximumMethaneProducingCapacities–Broiler Bo m3CH4/kgVS 0.36 ‐30 30 IPCC(2006)
MaximumMethaneProducingCapacities–Turkey
Bo m3CH4/kgVS 0.36 ‐30 30 IPCC(2006)
MaximumMethaneProducingCapacities–Duck Bo m3CH4/kgVS 0.36 ‐30 30 IPCC(2006)
MaximumMethaneProducingCapacities–Sheep
Bo m3CH4/kgVS 0.19 ‐20 20 IPCC(2006)
MaximumMethaneProducingCapacities–Feedlotsheep Bo m3CH4/kgVS 0.36 ‐20 20 IPCC(2006)
MaximumMethaneProducingCapacities–Goat
Bo m3CH4/kgVS 0.17 ‐30 30 IPCC(2006)
MaximumMethaneProducingCapacities–Horse Bo m3CH4/kgVS 0.3 ‐30 30 IPCC(2006)
MaximumMethaneProducingCapacities–Mule/Ass
Bo m3CH4/kgVS 0.33 ‐30 30 IPCC(2006)
EmissionfactorforthefractionofCH4producedthatleaksfromtheanaerobicdigester–Digesterswithsteelorlinedconcreteorfiberglassdigesterswithagasholdingsystem(eggshapeddigesters)andmonolithicconstruction
EFCH4,leakage
% 2.8 CDM(2012)
EmissionfactorforthefractionofCH4producedthatleaksfromtheanaerobicdigester–UASBtypedigesterswithfloatinggasholdersandnoexternalwaterseal
EFCH4,leakage
% 5 CDM(2012)
EmissionfactorforthefractionofCH4producedthatleaksfromtheanaerobicdigester–Digesterswithunlinedconcrete/ferrocement/brickmasonryarchedtypegasholdingsection;monolithicfixeddomedigesters
EFCH4,leakage
% 10 CDM(2012)
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Parameter
Abbreviation/Sym
bol
DataInputUnit
EstimatedValue
RelativeuncertaintyLow
(%
)
RelativeuncertaintyHigh
(%)
EffectiveLowerLimit
EffectiveUpperLimit
DataSource
EmissionfactorforthefractionofCH4producedthatleaksfromtheanaerobicdigester–Otherdigesterconfigurations
EFCH4,leakage
% 10 CDM(2012)
Temporarystorageofliquid/slurrymanure–N2Oemissionfactorc
EFN20 kgN2O‐N/kgN 0.005 ‐50 100 U.S.EPA(2011)
Long‐termstorageofsolidmanure–N2Oemissionfactorc
EFN20 kgN2O‐N/kgN 0.002 ‐50 100 U.S.EPA(2011)
Long‐termstorageofslurrymanure–N2Oemissionfactorc
EFN20 kgN2O‐N/kgN 0.005 ‐50 100 U.S.EPA(2011)
CattleandSwineDeepBedding(ActiveMix)‐N2Oemissionfactorc
EFN20 kgN2O‐N/kgN 0.07 IPCC(2006)
CattleandSwineDeepBedding(NoMix)‐N2Oemissionfactorc
EFN20 kgN2O‐N/kgN 0.01 IPCC(2006)
PitStorageBelowAnimalConfinements‐N2Oemissionfactorc
EFN20 kgN2O‐N/kgN 0.002 IPCC(2006)
Naturalaerationaerobiclagoons–N2Oconversionfactorc
EFN20 kgN2O‐N/kgN 0.01 ‐50 100 IPCC(2006)
Forcedaerationaerobiclagoons–N2Oconversionfactorc
EFN20 kgN2O‐N/kgN 0.005 ‐50 100 IPCC(2006)
N2Oemissionfactorforliquidstorage–uncoveredliquidmanurewithacrustc
EFN20 kgN2O‐N/kgN 0.8 ‐50 100 IPCC(2006)
N2Oemissionfactorforliquidstorage–uncoveredliquidmanurewithoutacrustc
EFN20 kgN2O‐N/kgN 0 ‐50 100 IPCC(2006)
N2Oemissionfactorforliquidstorage–coveredliquidmanurec
EFN20 kgN2O‐N/kgN 0 ‐50 100 IPCC(2006)
ManureManagement–MultipleSources–collectionefficiency,coveredstorage(withorwithoutcrust)
η Percentage 1 Sommeretal.(2004)
ManureManagement–MultipleSources–collectionefficiency,uncoveredstoragewithcrustformation
η Percentage 0
Sommeretal.(2004)
ManureManagement–MultipleSources–collectionefficiency,uncoveredstoragewithoutcrustformation
η Percentage ‐0.40
Sommeretal.(2004)
ManureManagement–MultipleSources–Ratecorrectingfactors(b1)
b1 Dimensionless 1 Sommeretal.(2004)
ManureManagement–MultipleSources–Ratecorrectingfactors(b2)
b2 Dimensionless 0.01Sommeretal.(2004)
ManureManagement–MultipleSources–Arrheniusparameter,cattle
A gCH4/kgVS/hr 43.33 Sommeretal.(2004)
ManureManagement–MultipleSources–Arrheniusparameter,swine
A gCH4/kgVS/hr 43.21Sommeretal.(2004)
Potentialmethaneyieldofthemanurecattle
ECH4,pot‐
kgCH4/kgVS 0.48 Sommeretal.(2004)
Potentialmethaneyieldofthemanure‐swine
ECH4,pot
kgCH4/kgVS 0.5Sommeretal.(2004)
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5-105
Parameter
Abbreviation/Sym
bol
DataInputUnit
EstimatedValue
RelativeuncertaintyLow
(%
)
RelativeuncertaintyHigh
(%)
EffectiveLowerLimit
EffectiveUpperLimit
DataSource
Temporarystackandlong‐termstockpile–Ratiodegradablevolatilesolidstototalvolatilesolids‐cattleliquidmanure
VSd/VST
Unitless 0.46 Mølleretal.(2004)
Temporarystackandlong‐termstockpile–Ratiodegradablevolatilesolidstototalvolatilesolids‐swineliquidmanure
VSd/VST
Unitless 0.89 Mølleretal.(2004)
Temporarystackandlong‐termstockpile–RatioNon‐degradablevolatilesolidstototalvolatilesolids‐cattleliquidmanure
VSnd/VST
Unitless 0.54 Mølleretal.(2004)
Temporarystackandlong‐termstockpile–Rationon‐degradablevolatilesolidstototalvolatilesolids–swineliquidmanure
VSnd/VST
Unitless 0.11 Mølleretal.(2004)
aThevaluesformethaneconversionfactor(MCF)varydependingonthetemperatureandthemanuremanagementsystem.IPCC(2006)providesestimateduncertaintyrangesfortheseMCFs.bTherearenodataforNorthAmericaregion;thedatafromWesternEuropeareusedtocalculatetheestimation.Thereisnoreporteduncertaintyforthisadaptedvalue.cIPCC(2006)reportslargeuncertaintieswithdefaultN2Oemissionfactors.TheN2OEFvaluesvarydependingontheanimalspeciesandtemperatureofthemanuremanagementsystem.
5.5 ResearchGaps
Researchgapshavebeenidentifiedforanimalproductionsystems,coveringactivitydata,aswellaskeyareasthatwouldfacilitatemoreaccurateestimationofemissionsfromentericfermentationandmanuremanagementsystems.Recommendationsarediscussedbelow.
5.5.1 EntericFermentation
CattleFutureresearchrelatedtoimprovingemissionsestimatesshouldbeaimedatexpandingtheoptionswithinexistingmodelstobetterdescribeanindividualfarmsystemandincorporatemoreoptionsformitigationstrategiestoseehowemissionsmightchangewithimplementationofthesestrategiesaswellasconsidertheinteractiveeffectsofmultiplestrategies.
BeefCow‐Calf,Bulls,Stocker,andSheepKeydataneedsincludemeasurement/predictionoffeedintakeonpasture,measurement/predictionofCH4fromgrazinganimals(largernumbersofanimals),andmethodsbywhichtocharacterizerangeforageandintakeunderproductionconditions.
FeedlotThereisaneedforequationsandmodelstoaccuratelypredictentericCH4emissionsfromcattleandsheepfedhigh‐concentratefinishingdiets.
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DairyOneofthelargestresearchgapsisthelackofbasicdatarelatedtoemissionsfromcalves,heifers,anddrycowhousingsystems.Inaddition,thereisaneedforequallyconsistentandreliablemethodsformeasuringrelativedifferencesinemissionsassociatedwiththeimplementationofavarietyofmanagementpractices.Furthermodeldevelopmentforestimatingemissionsshouldincludeanexpansionofoptionstodescribetheproductionfacilityandinclusionofmanagementpracticesthatcanbeadoptedtomitigateemissions.
SwineFutureresearchrelatedtoimprovingemissionsestimatesshouldbeaimedatexpandingtheoptionswithinthesemodelstobetterdescribeanindividualfarmsystemandincorporatemoreoptionsformanagementandmitigationstrategiestoseehowemissionsmightchangewithimplementationofdifferentpractices.Minimally,thedietconsiderationsinHolosneedtobeincorporatedintotheMANUREmodelandexpandedtoreflectproductionphase.
PoultryFutureresearchrelatedtoimprovingemissionsestimatesshouldbeaimedatexpandingtheoptionswithinthesemodelstobetterdescribeanindividualfarmsystemandincorporatemoreoptionsformanagementandmitigationstrategiestoseehowemissionsmightchangewithimplementationofdifferentpractices.
5.5.2 ManureManagement
Greenhousegasemissionsfromavarietyofmanuremanagementsystemshavebeendevelopedfromalimitednumberofstudiesandalimitednumberofpotentialvariationsinmanagementandtheenvironmentalconditionsaroundaparticularmanuremanagementsystem.ThelargestdeficiencyinthecurrentGHGstudiesisthelackofcharacterizationofthetemporalvariationintheGHGemissionsfromdifferentsystemsandthespatialvariationinGHGemissionsinducedbymeteorologicalconditionsamongspecificlocations.Ingeneral,theresearchneededtodevelopamorecompleteunderstandingoftheGHGemissionscanbesummarizedas:
Developdatabasesfromresearchobservationsofcommercialfacilitiesthatcharacterizethestoragesystem,timeinstorage,environmentalconditionsandlocation,andtheattributesofthemanuresource,e.g.,typeofanimal,diet,loadingrate.
UtilizethedatabasestoderivesimulationmodelstoquantifytheGHGemissionsfromdifferentmanuremanagementsystems.
ValidatethemodelsusingindependentobservationsfrommanuremanagementsystemsdistributedaroundtheUnitedStates.
Developoperationalmodelscapableofbeingappliedtoproductionscalesystemswhichutilizesimpleparametersasinputvariablesandproduceresultsinagreementwiththemorecomplexsimulationmodels.
UtilizethesemodelstodeveloppotentialstrategieswhichcouldbeemployedtomitigateGHGemissionsfrommanuremanagementsystems.
TemporaryStackandLong‐TermStockpileMethaneemissiondatafromsolidstoragesindifferentregionsunderdifferentclimatesarelimited.InordertodevelopamoreaccuratemodeltoestimatetheCH4emissionfromsolidmanurestorages,in‐depthstudiesareneededtointegratetemperature,storagetime,storagemethod,andmassflowwithCH4emissionindifferentregions.AsforN2Oemission,systematicallycollectingmoreintensedata(avarietyofspatialandtemporalscales)fromdifferentregionswillbeagoodfirststeptowardaccurateN2Oemissionmodels.Oncethesedataarecollectedandusedtodevelop/validatemodels,workwilllikelybeneededtodevelopfarmer‐friendlymodelsusing
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simplefarmparametersasinputvariables,resultinginemissionsestimatesthatarecorrelatedwiththoseofmorecomplexmodels.Forexample,thesemodels,ifsynchronized,couldformpartofacomprehensivemanurestewardshiptoolkit.
ThereisapaucityofdataonCH4andN2Oemissionsfromopenlot(beeffeedlotsanddairies)pensurfacesandrunoffcontrolstructuresandonthechemicalandphysicalfactorscontrollingthoseemissions.
CompostingGreenhousegasemissionsdatafromcompostingindifferentregionsunderdifferentoperationalconditionsarelimited.AgoodfirststeptowardanaccurateGHGemissionsmodelwouldbetocollectmoredatafromdifferentregionsanddifferentoperationalconditions.Consequently,in‐depthstudiesintegratingcompostpilesize/surfacearea,pileshape,aerationrate,storagetime,compostingtemperature,etc.,withGHGemissionsneedtobeconductedtodevelopcomplexmodelsdescribingGHGemissionsfromcomposting.Furthermore,workwilllikelybeneededtodevelopfarmer‐friendlymodelsusingsimplefarmparametersasinputvariables,resultinginemissionestimationsthatarecorrelatedwiththoseofmorecomplexmodels.
TherehavebeensomestudiesperformedtoestimatetheemissionfactorsforN2Ofromcompostingmanureindifferentsystemsandfordifferentlivestockcategories.(Fukummotoetal.,2003;Szantoetal.,2006)haveconductedstudiesoncompostingswinemanureatspecificambienttemperatures.Factorshavebeenpresentedinthestudiesbutthereissignificantuncertaintyduetothelimiteddataavailable.Furtherresearchisneededtorefinetheseemissionfactorsaswellasdevelopfactorsforotheranimals.
AerobicLagoonIn‐depthstudiesareneededtointegratelagoondepths,aerationrate,pH,temperature,andnutrientconditionsofmanurewithGHGemissions,whichwillfacilitatethedevelopmentofcomprehensivemodelstopredictGHGemissionsunderdifferentoperationalandclimateconditions.Simplifiedandfarm‐friendlymodelsusingfarmoperationalparametersasinputsshouldbedevelopedtohelpfarmsestimatetheGHGemissionsattheentitylevel.
AnaerobicLagoon,RunoffHoldingPond,andStorageTanksAllmodelstoestimateGHGemissionsfromliquidmanurestoragearerelativelyinaccurate,duetothecomplexityandvarietyoflivestockmanureoperations.Inordertodevelopamoreaccuratemodeltoestimateemissionsfromliquidmanurestorages,in‐depthstudiesareneededtointegratemanurestorageconfiguration,temperature,storagetime,storagemethod,massflow,andsurfaceturbulencewithemissionsindifferentregions.Inaddition,systematicallycollectingmoredatafromdifferentregionswillbeveryhelpfultodevelopmorestatisticallyaccuratemodelstoestimateGHGemissions.
AnaerobicDigestionChangesinchemicaloxygendemand,volatilesolids,totalsolids,andnitrogenintheanaerobicdigestionprocessareindirectlylinkedtoGHGemissionsfrompost‐treatmentofanaerobicdigestioneffluent.TheeffectivenessofanaerobicdigestionatmitigatingGHGemissionshasbeenstudiedintensively.However,anaerobicdigestioneffluentcanleadtoGHGemissions.Morein‐depthstudiesareneededtodevelopintegratedmodelsthatcanaccuratelypredicttheoverallGHGemissionfromthecombinationofanaerobicdigestionandpost‐treatmentapproaches.
CombinedAerobicTreatmentSystemsMethodsandtechniquestoreducethecapitalandoperatingcostsareneeded.Thereisalsoaneedtodevelopbetterwaystoconserveandderiveenergyfromthewastematerial.Thereisapaucityof
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dataonGHGemissionsfromthesesystemsanddevelopmentofemissionmodelswillrequireintegrationofdatacharacterizingthesesystemsandtheclimaticconditionsinordertodevelopthesemodels.Thesemodelswillneedtobevalidatedagainstobserveddata.
NutrientRemovalVariousmethodsofnitrogenremoval,suchasbiologicalnitrogenremoval,Anamox,NH3stripping,ionexchange,andstruvitecrystallization,shouldbeinvestigatedatcommercial‐scaleanimaloperationsunderdifferentclimateconditions.Characteristicsofmanure,massflow,andgasemissionsshouldbecloselymonitoredinordertoprovidethedataneededtoconstructrelativelypreciseestimationmodels.Inaddition,furtherresearchisneededtopilotinnovativebeefanddairyGHGemissionreductionstrategiesinfeedlotsanddairies.
ConstructedWetlandAlthoughtherearenumerouspaperspublishedaboutvariousaspectsoftreatmentwetlandeffectivenessandemissions,therecurrentlyisnotanestablishedmethodforcalculationofGHGemissionsfromanyofthetreatmentwetlandtypes.Moreover,therearenotsufficientunifyingpublicationstosuggestthatareliablemethodcouldbeestablishedwithinthescopeofthisreport.AmorerobustandextensivedatabaseonGHGemissionsfromtreatmentwetlandsisneeded.Concomitantly,thereisaneedforbetterpredictiveequationandmodels.
Thermo‐ChemicalConversionMorestudiesareneededontheeffectsofthermalconversionofanimalmanureonGHGemissioninordertoconcludedetailedemissionprofilescorrespondingtodifferenttypeofmanure.ThesestudieswouldentaildetailedobservationsofthemanureconversionsystemalongwithGHGemissionsandinformationontheenvironmentalconditions.
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Appendix5‐A:EntericCH4fromFeedlotCattle–MethaneConversionFactor(Ym)AsnotedintheBeefProductionSystemssection(Section5.3.2.2),amodifiedIPCC(2006)methodisproposedtoestimateentericCH4emissionsfromfinishingbeefcattle.Forthisreport,abaselinescenariobasedontypicalU.S.beefcattlefeedingconditionswasestablishedandbaselinevaluesweresetbasedonpublishedresearch.Toestimatemethaneemissions,emissionvaluesaremodifiedusingadjustmentfactorsthatarebasedonchangesinanimalmanagementandfeedingconditionsfromthebaselinescenario.Thisappendixpresentsbackgroundinformationonthebaselinescenarioandadjustmentfactors.
ThefollowingbaselinescenariosareestablishedforbeefcattleinU.S.feedlots:
1. Mediumtolargeframesteer(orheifer)yearlingsarefedahighconcentratefinishingdietcontaining<=10percentforageindietdrymatter(=to8to18percentNDF)indry‐lot,soil‐surfacedpens.
2. Thegrainportionofthedietisatleast70percentofdietdrymatter.3. Thegrainsourceissteamflaked(SFC)orhighmoisturecorn(HMC).4. Thedietarycrudeproteinconcentrationis12.5to13.5percentofdietdrymatter
(VasconcelosandGalyean,2007).5. Thedietaryruminallydegradableprotein(DIPorRDP)concentrationis7.5to9percentof
dietdrymatter(VasconcelosandGalyean,2007).6. Thedietcontainsmonensin(Rumensin,ElancoAnimalHealth)atrecommended
concentrations(VasconcelosandGalyean,2007).7. Dietsforheiferscontainmelengestrolacetate(MGA)attherecommendedconcentrations
(VasconcelosandGalyean,2007).8. Cattleareimplantedwithanestrogenicimplantthroughoutthefeedingperiod(Vasconcelos
andGalyean,2007).9. Nobeta‐agonistisfed.10. Thedietcontainsnosupplementalfat(vegetableoil,yellowgrease,etc.)andhasatotalfat
concentrationoflessthan4.5percentofdietdrymatter.11. EntericCH4emissionisthreepercentofgrossenergyintake(GEI:(IPCC,2006).12. Thedietaryforageischoppedalfalfa,sorghum,orgrasshayatsevento10percentofdiet
drymatter.13. Thedietcontainsmineralsandvitaminsattherecommendedlevel(NRC,2000).14. Temperaturesaremild/moderateduringthefeedingperiod.15. Cattleareslaughteredatanaveragebodyweightofapproximately582kg(1,280lb.)(KSU,
2012).16. Averagedressingpercentis61percent.17. Cattlearefed150days.
TheYmadjustmentfactorsforfeedlotcattlefedhigh‐concentratedietsinTable5‐11weredeterminedbasedonthefollowingliteraturereviewsandanalyses.
Ionophores:Onaverage,thefeedingofionophoresdecreasesDMIbyaboutfivepercent(Delfinoetal.,1988;Vogel,1995;RobinsonandOkine,2001;Tedeschietal.,2003)anddecreasesADGbyabouttwopercent(Delfinoetal.,1988;Tedeschietal.,2003).Feedingionophoresdecreasesentericmethaneemissionsapproximately20percentforthefirsttwotofourweeksonfeed(Tedeschietal.,2003;Guanetal.,2006).Therefore,overa150‐dayfeedingperiod,overallentericmethane
Chapter 5: Quantifying Greenhouse Gas Sources and Sinks in Animal Production Systems
5-110
emissionsaredecreasedapproximately4percent.Becauseofanincreaseinthegain:feedratio,entericmethaneemissionsperunitofproductionaredecreasedwhenionophoresarefed.
SupplementalFat:Foreachonepercentincreaseinsupplementalfat(uptoamaximumoffourpercentaddedfat),entericmethaneemissions(asapercentageofgrossenergyintake)decreaseapproximately3.8to5.6percent(ZinnandShen,1996;Beaucheminetal.,2008;Martinetal.,2010).AconservativevalueoffourpercentperonepercentincreaseinsupplementalfatisrecommendedbecausemanyfatsourcesusedintheindustryarepartiallysaturatedandmayhavelesseffectonentericCH4productionthanthehighlyunsaturatedfatsusedinmoststudies.Forexampleifthreepercentsupplementalfatisaddedtothediet,thenCH4productionisdecreased12percent(threepercentaddedfattimesfourpercentisequivalenttoa12percentdecrease).TherevisedentericCH4emissionis2.64percentofGEI(threepercentbaseline*0.88=2.64percentofGEI).Manydistiller’sgrainscontainapproximately8to12percentfat.Additionofdistiller’sgrainmayserveasasourceofsupplementalfat,andthusdecreaseentericCH4(McGinnetal.,2009).HoweverHalesetal.(2013)notedthatfeedingincreasingconcentrationsofWetDistillersGrainswithSolubles(WDGS)inequal‐fatdietsincreasedentericCH4,likelyduetotheincreasedNDFintake.12
Grainprocessing&Grainsource:GrainprocessingdirectlyaffectsentericCH4productionviaitseffectsonruminalfermentation.EntericCH4emissions,asapercentofGEI,are20percentgreaterwithdietsbasedonDRCthanindietsbasedonsteam‐flakedcorn(SFC)orhighmoisturecorn(HMC)(Archibequeetal.,2006;Halesetal.,2012).Moreextensivegrainprocessingmayalsoimprovethegain:feedratioabout10percent(Owensetal.,1997;ZinnandBarajas,1997)andmay,decreasemanureCH4emissionsviadecreasedfecalstarchexcretion(ZinnandBarajas,1997;Halesetal.,2012).EntericCH4emissionsare20to40percentgreaterwithfinishingdietsbasedonbarleythandietsbasedoncorn;presumablybecauseofthelowerstarchandhigherfibercontentofbarley(Benchaaretal.,2001;BeaucheminandMcGinn,2005).Amean(30%)forthesestudiesisrecommendedforabarleyadjustmentfactor.
DietaryForageandGrainConcentrationeffects:LimiteddataexiststoevaluateeffectsofdietaryforageandgrainconcentrationonentericmethaneproductionfrombeefcattlethatarefedtypicalU.S‐based,highconcentratefinishingdiets.EquationsfromEllisetal.(2007;2009)illustratetheeffectsofdietaryforage,NDF,andstarchonentericCH4production.Inparticular,thefollowing10equationsillustratetherelationships:
CH4(MJ/day)=3.96+0.561×DMI(kg/day) CH4(MJ/day)=4.79+0.0492×Forage(%) CH4(MJ/day)=5.58+0.848×NDF(kg/day) CH4(MJ/day)=5.70+1.41×ADF(kg/day) CH4(MJ/day)=2.29+0.670×DMI(kg/day) CH4(MJ/day)=4.72+1.13×Starch(kg/day) CH4(MJ/day)=‐1.01+2.76×NDF(kg/day)+0.722×Starch(kg/day) CH4(MJ/day)=2.68–1.14(Starch:NDF)+0.786×DMI(kg/day) CH4(MJ/day)=2.50=0.367×Starch(kg/day)+0.766×DMI(kg/day) CH4(MJ/day)=2.70+(1.16×DMI(kg/day))–(15.8×etherextract(kg/day))
12Ymisadjustedfordistillergrainsbychangesinfatcontentandgrainconcentration.Forexample,a30percentconcentrationofdistillergrainsinthefinishingdietwilltypicallyincreasethedietaryfatlevelby2to3percentanddecreasethegraincontentby25to30percent.TheresultingchangeinYmisadecreaseby8percenttoaccountforincreaseinfatcontentandanincreaseof10percenttoaccountforadecreaseingraincontent(i.e.,Ym=3%x0.92x1.10=3.036%).
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Todevelopadjustmentfactorsforgrainconcentrationsindiets,artificialdatasetswerecreatedthatvariedinforage(rangeof5to25percent),NDF(range10to20percent),fat(rangeof3to6percent),andstarch(rangeof30to60percentofdietdrymatter)content.Usingthesedatasets,entericCH4emissionswereestimatedusingtheappropriateequation(s)ofEllisetal.(2007;2009).EffectsofdietarychangesonentericCH4werethendeterminedbylinearregressionanalysis.Onaverage,entericCH4production(MJ/day)increasedfivepercentforeachonepercentincreaseindietaryforageconcentration;increased13percentforeachonekgincreaseindietaryNDFintake,increasedfivepercentforeachonekgincreaseinstarchintakeanddecreasedfivepercentforeachoneunitincreaseinthedietarystarch:NDFratio.SmallincreasesinforageconcentrationfromthebaselinevaluehadsmalleffectsonYm;whereas,greaterincreaseshadalargereffect(Halesetal.,2012;Halesetal.,2014).AnevaluationofthesefactorsindicatedanentericCH4Ymadjustmentfactorof10%forsmallincreasesinforage(anddecreasesingrainconcentration)andalargercorrectionfactorof40percentforgreaterchanges(dietconcentratelessthan45percent).Thesefactorsarerecommendedforaccountingforthegrainconcentrationinfinishingdiets.
NoYmadjustmentfactorwasexplicitlymodeledtoaccountforthefollowingdietarymanagementfactors:13
Beta‐agonists:Beta‐agonistsdonotdirectlyaffecttheYm(i.e.,entericCH4emissionsperunitofgrossenergyintake),thereforenoadjustmentfactorisrecommended.However,becauseofa4percentincreaseinfeedefficiency,a2.5to3.5%increaseinhotcarcassweight(HCW),andanincreaseinlivebodyweight(Vasconcelosetal.,2008;Elametal.,2009;Montgomeryetal.,2009;Delmoreetal.,2010;Radunz,2011),entericCH4emissionsperunitofproductionaredecreasedwhenbeta‐agonistsarefed.
Melengestrolacetate(MGA:heifersonly):FeedingMGAtoheifersdoesnotdirectlyaffectentericCH4emissions.However,becauseofaninepercentincreaseinthegain:feedratio(Hilletal.,1988;KreikemeierandMader,2004)entericCH4emissionsperunitofproductionaredecreasedwhenMGAisfed.
DirectFedMicrobials:MostdirectfedmicrobialsdonotappeartodirectlyaffectentericCH4emissionsandeffectsonanimalperformancearesomewhatvariable(Krehbieletal.,2003).Noadjustmentfactorisrecommendedforthefeedingofdirectfedmicrobials.
DietaryCrudeProteinandRuminalDegradableProtein(RDP):DietaryproteinmaypotentiallyaffectanimalperformanceandentericCH4emissionsviaeffectsonruminalfermentation.However,thereisnoreadilyavailabledatawithmodernfeedlotdietswithwhichtocompare(BergerandMerchen,1995;RobinsonandOkine,2001;Gleghornetal.,2004;Coleetal.,2006;Wagneretal.,2010).ThereisnorecommendedYmadjustmentfactorfordietaryprotein.Dietaryproteinmayaffectemissionsofmanuregreenhousegases(N2O)anddefinitelyaffectsNH3emissions(Toddetal.,2013).
Implantingregimens:ImplantsdonotdirectlyaffectentericCH4emissions.Howeverbecauseofanincreaseinfeedefficiency,livebodyweight,andHCW(Herschleretal.,1995;RobinsonandOkine,2001;Wilemanetal.,2009),entericCH4emissionsperunitofproductionaredecreasedwhenimplantsareused.
Ambienttemperature:ColdandhottemperaturesmaypotentiallyaffectentericCH4emissionduetoeffectsonfeedintake,ruminaldigestionandrateofpassage(Young,1981);however,theactualeffectsarenotclear.Thereforenoadjustmentfactorforenvironmentaltemperatureisused.ColdtemperaturesmaydecreaseCH4,N2OandNH3lossesfrompen
13AlthoughthesemanagementfactorsarenotmodeledtoimpactYm,someofthemdoimpactentericCH4perunitofproduction.Hence,inevaluatingmethaneintensityperunitofproduction,thesefactorswouldhaveanimpact.
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surfacesviaeffectsonmicrobialactivityinthemanure.Conversely,warmtemperaturesmayincreaseemissionsfrommanureviaincreasedmicrobialactivity.
TheIPCCTier2modeliscurrentlythemostusefulforpredictingemissionsfromcow‐calfandstockerproduction,aswell,asnotedintheearliercow‐calfandstockerSections(5.3.2.2).EntericemissionsfromallcattleotherthandairycowsanddairyheifersareestimatedusingtheIPCCTier2equationorthemodifiedIPCCTier2previouslydiscussedforfeedlotcattle.Tousetheseequations,itisnecessarytomakesuretheinputstotheequationsareasaccurateaspossible.ForDE(asapercentageofGE),werecommendusingthefeedstuffscompositiontableprovidedinNRC(1989)andEwan(1989).SeveralfeedstuffsfromthetableareincludedinTable5‐C‐1.Afterreviewofthemodels,theirstrengthsandlimitations,modelsbasedontheMillsequations(e.g.,DairyGEM,COWPOLL,IFSM)appeartobethemostusefulforpredictingemissionsfromdairycattle.TheMits3equationrecommendedforcalculatingentericCH4emissionsfromdairycowsanddairyheifers(usedinDairyGEM/IFSM)requiresdifferentdietaryinputinformationthanthatrequiredfortheIPCCTierIIequation.Specifically,DairyGEM/IFSMrequiresthestarchandADFcontentoffeeds.BecausestarchisnearlyequivalenttoNFC(whichisstarch+sugar+pectin)inhighforagediets(dairydiets),weuseNFCintheMits3equation(NFC=100–(NDF+CP+EE+Ash)).ThesevaluescanbefoundinAppendix5‐B.
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Appendix5‐B:FeedstuffsCompositionTableThistableprovideddatainputsforentericfermentationemissionscalculationsforcattleandsheep.
Table5‐B‐1:FeedstuffsCompositionTable(Preston2013,exceptwherenotedfordigestibleenergy)
Feedstuff DM %
Energy Protein Fiber
EE%
ASH%
Ca %
P %
K %
Cl%
S %
Zn ppmTDN
% NEm NEg NEl
(Mcal/cwt.)
DE (% of
GE)a
CP%
UIP%
CF%
ADF%
NDF%
eNDF%
Alfalfa Cubes x91 57 57 25 57 18 30 29 36 46 40 2.0 11 1.30 0.23 1.9 0.37 0.33 20
Alfalfa Dehydrated
17% CP 92 61 62 31 61 65.16 19 60 26 34 45 6 3.0 11 1.42 0.25 2.5 0.45 0.28 21
Alfalfa Fresh 24 61 62 31 61 62.54
b 19 18 27 34 46 41 3.0 9 1.35 0.27 2.6 0.40 0.29 18
Alfalfa Hay Early Bloom
90 59 59 28 59 63.72 19 20 28 35 45 92 2.5 8 1.41 0.26 2.5 0.38 0.28 22
Alfalfa Hay Midbloom
89 58 58 26 58 61.79 17 23 30 36 47 92 2.3 9 1.40 0.24 2.0 0.38 0.27 24
Alfalfa Hay Full Bloom
88 54 54 20 54 55.71 16 25 34 40 52 92 2.0 8 1.20 0.23 1.7 0.37 0.25 23
Alfalfa Hay Mature
88 50 50 12 49 54.18 13 30 38 45 59 92 1.3 8 1.18 0.19 1.5 0.35 0.21 23
Alfalfa Seed Screenings
91 84 92 61 87 34 13 15 10.7 6 0.30 0.67
Alfalfa Silage 30 55 55 21 55 60.71
c 18 19 28 37 49 82 3.0 9 1.40 0.29 2.6 0.41 0.29 26
Alfalfa Silage Wilted
39 58 58 26 58 60.71
d 18 22 28 37 49 82 3.0 9 1.40 0.29 2.6 0.41 0.29 26
Alfalfa Leaf Meal
89 60 60 30 60 26 15 16 24 34 35 3.0 10 2.88 0.34 2.2 0.32 39
Alfalfa Stems 89 47 47 7 46 11 44 44 51 68 100 1.3 6 0.90 0.18 2.5
Almond Hulls 89 56 56 23 56 59.90 3 60 16 29 36 100 3.1 7 0.24 0.10 2.0 0.03 0.07 20
Ammonium Chloride
99 0 0 0 0 163 0 0 0 0 0 0.0 0.00 0.00 0.0 66.00 0.00 0
Ammonium Sulfate
99 0 0 0 0 132 0 0 0 0 0 0.0 24.15
Apples 17 70 73 44 71 3 10 7 9 25 10 2.2 2 0.06 0.60 0.8
Apple Pomace Wet
20 68 70 41 69 5 10 18 27 36 27 5.2 3 0.13 0.12 0.5 0.04 11
Apple Pomace Dried
89 67 69 40 68 56.69 5 15 18 28 38 29 5.2 3 0.13 0.12 0.5 0.04 11
Artichoke Tops (Jerusalem)
27 61 62 31 61 6 18 30 41 40 1.1 10 1.62 0.11 1.4
Avocado Seed Meal
91 52 52 16 51 20 19 24 1.2 16
Bahiagrass Hay 90 53 53 18 53 54.85 6 37 32 41 72 98 1.8 7 0.47 0.20 1.4 0.21
Bakery Product Dried
90 90 100 68 94 81.31 11 30 3 9 30 0 11.5 4 0.16 0.27 0.4 2.25 0.15 33
Bananas 24 84 92 61 87 4 4 5 0.8 3 0.03 0.11 1.5 8
Barley Hay 90 57 57 25 57 60.89 9 28 37 65 98 2.1 8 0.30 0.28 1.6 0.19 25
Barley Silage 35 59 58 26 58 12 22 34 37 58 61 3.0 9 0.46 0.30 2.4 0.22 28
Barley Silage Mature
35 58 58 26 58 12 25 30 34 50 61 3.5 9 0.30 0.20 1.5 0.15 25
Barley Straw 90 44 44 1 43 43.98 4 70 42 55 78 100 1.9 7 0.32 0.08 2.2 0.67 0.16 7
Barley Grain 89 84 92 61 87 12 28 5 7 20 34 2.1 3 0.06 0.38 0.6 0.18 0.16 23
Barley Grain, Steam Flaked
85 90 100 70 100 12 39 5 7 20 30 2.1 3 0.06 0.35 0.6 0.18 0.16 23
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Feedstuff DM %
Energy Protein Fiber
EE%
ASH%
Ca %
P %
K %
Cl%
S %
Zn ppmTDN
% NEm NEg NEl
(Mcal/cwt.)
DE (% of
GE)a
CP%
UIP%
CF%
ADF%
NDF%
eNDF%
Barley Grain Steam Rolled
86 84 92 61 87 12 38 5 7 20 27 2.1 3 0.06 0.41 0.6 0.18 0.17 30
Barley Grain 2-row
87 84 92 61 87 12 6 8 24 34 2.3 2 0.05 0.31 0.6 0.18 0.17
Barley Grain 6-row
87 84 92 61 87 11 6 8 24 34 2.2 3 0.05 0.36 0.6 0.18 0.15
Barley Grain Lt. Wt. (42-44
lb/bu) 88 78 83 54 80 13 30 9 12 30 34 2.3 4
Barley Feed Pearl Byproduct
90 74 78 49 76 15 25 12 15 3.9 5 0.05 0.45 0.7 0.06
Barley Bran 91 59 59 28 59 12 28 21 27 36 6 4.3 7
Barley Grain Screenings
89 71 74 46 73 12 9 11 2.6 4 0.35 0.33 0.9 0.15
Beans Navy Cull
90 84 92 61 87 84.52 24 25 5 8 20 0 1.4 5 0.15 0.60 1.4 0.06 0.26 45
Beet Pulp Wet 17 77 82 53 79 75.09 9 35 20 25 45 30 0.7 5 0.65 0.08 0.9 0.40 0.22 21
Beet Pulp Dried 91 76 81 52 78 79.81 9 44 21 26 46 33 0.7 5 0.65 0.08 0.9 0.40 0.22 21
Beet Pulp Wet with Molasses
24 77 82 53 79 11 25 16 21 39 33 0.6 6 0.60 0.10 1.8 0.42 11
Beet Pulp Dried with Molasses
92 77 82 53 79 82.52 11 34 17 23 40 33 0.6 6 0.60 0.10 1.8 0.42 11
Beet Root (Sugar)
23 80 86 56 83 4 5 7 16 0.4 3
Beet Tops (Sugar)
19 58 58 26 58 14 11 14 25 41 1.3 24 1.10 0.22 5.2 0.20 0.45 20
Beet Top Silage 25 52 52 16 51 12 12 2.0 32 1.38 0.22 5.7 0.57 20
Bermudagrass Coastal
Dehydrated 90 62 63 33 63 16 40 26 29 40 10 3.8 7 0.40 0.25 1.8 0.72 0.23 18
Bermudagrass Coastal Hay
89 56 56 23 56 53.05 10 20 30 36 73 98 2.1 6 0.47 0.21 1.5 0.70 0.22 16
Bermudagrass Hay
89 53 53 18 53 50.79 10 18 29 37 72 98 1.9 8 0.46 0.20 1.5 0.70 0.25 31
Bermudagrass Silage
26 50 50 12 49 10 15 28 35 71 48 1.9 8 0.46 0.20 1.5 0.72 0.25 31
Birdsfoot Trefoil Fresh
22 66 68 38 67 21 20 21 31 47 41 4.4 9 1.78 0.25 2.6 0.25 31
Birdsfoot Trefoil Hay
89 57 57 25 57 16 22 31 38 50 92 2.2 8 1.73 0.24 1.8 0.25 28
Biuret 99 0 0 0 0 248 0 0 0 0 0 0.0 0 0.00 0.00 0.0 0.00 0.00 0
Blood Meal, Swine/Poultry
91 66 68 38 67 92 82 1 2 10 0 1.4 3 0.32 0.28 0.2 0.30 0.70 22
Bluegrass KY Fresh Early
Bloom 36 69 71 43 70 75.62 15 20 27 32 60 41 3.9 7 0.37 0.30 1.9 0.42 0.19 25
Bluegrass Straw 93 45 45 3 44 6 40 50 78 90 1.1 6 0.20 0.10
Bluestem Fresh Mature
61 50 50 12 49 56.82 6 34 2.5 5 0.40 0.12 0.8 0.05 28
Bread Byproduct
68 90 100 68 94 14 24 1 2 3 0 3.0 3 0.10 0.18 0.2 0.76 0.15 40
Brewers Grains Wet
23 85 93 62 88 62.66 26 52 13 21 45 18 7.5 4 0.30 0.58 0.1 0.15 0.32 78
Brewers Grains Dried
92 84 92 61 87 60.43 25 54 14 24 49 18 7.5 4 0.30 0.58 0.1 0.15 0.32 78
Brewers Yeast Dried
94 79 85 55 81 48 3 1.0 7 0.10 1.56 1.8 0.41 41
Bromegrass Fresh Immature
30 64 65 36 65 78.57 15 22 28 33 54 40 4.1 10 0.45 0.34 2.3 0.21 20
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FeedstuffDM %
Energy Protein Fiber
EE%
ASH%
Ca %
P %
K %
Cl%
S %
Zn ppmTDN
%NEm NEg NEl
(Mcal/cwt.)
DE (% of
GE)a
CP%
UIP%
CF%
ADF%
NDF%
eNDF%
Bromegrass Hay
89 55 55 21 55 62.19
e 10 33 35 41 66 98 2.3 9 0.40 0.23 1.9 0.40 0.19 19
Bromegrass Haylage
35 57 57 25 57 11 26 36 44 69 61 2.5 8 0.38 0.30 2.0 0.20 19
Buckwheat Grain
88 75 79 50 77 72.27 12 13 17 2.8 2 0.11 0.36 0.5 0.05 0.16 10
Buttermilk Dried 92 88 98 65 91 34 0 5 0 0 0 5.0 10 1.44 1.00 0.9 0.09 44
Cactus, Prickly Pear
23 61 62 31 62 5 16 20 28 2.1 18 4.00 0.10 1.5 0.20
Calcium Carbonate
99 0 0 0 0 0 0 0 0 0 0.0 99 38.50 0.04 0.1 0.00 0
Canarygrass Hay
91 53 53 18 53 9 26 32 34 67 98 2.7 8 0.38 0.25 2.7 0.14 18
Canola Meal, Solv. Ext.
90 72 75 47 74 41 30 11 19 29 23 2.0 8 0.74 1.14 1.1 0.07 0.78 68
Carrot Pulp 14 62 63 33 63 6 19 23 40 0 7.8 9
Carrot Root Fresh
12 83 90 60 86 92.29 10 9 11 20 0 1.4 10 0.55 0.32 2.5 0.50 0.17
Carrot Tops 16 73 77 48 75 13 18 23 45 41 3.8 15 1.94 0.19 1.9
Cattle Manure Dried
92 38 40 0 36 30.58 15 35 42 55 0 2.5 14 1.15 1.20 0.6 1.78 240
Cheatgrass Fresh Immature
21 68 70 41 69 16 23 2.7 10 0.60 0.28
Citrus Pulp Dried
90 78 83 54 80 7 38 13 20 21 33 2.9 7 1.81 0.12 0.8 0.04 0.08 14
Clover Ladino Fresh
19 69 71 43 70 73.22 25 20 14 33 35 41 4.8 11 1.27 0.38 2.4 0.20 20
Clover Ladino Hay
90 61 62 31 61 63.40 21 25 22 32 36 92 2.0 9 1.35 0.32 2.4 0.30 0.20 17
Clover Red Fresh
24 64 65 36 65 18 21 24 33 44 41 4.0 9 1.70 0.30 2.0 0.60 0.17 23
Clover Red Hay 88 55 55 21 55 58.33 15 28 30 39 51 92 2.5 8 1.50 0.25 1.7 0.32 0.17 17
Clover Sweet Hay
91 53 53 18 53 16 30 30 38 50 92 2.4 9 1.27 0.25 1.8 0.37 0.46
Coconut Meal, Mech. Ext.
92 76 81 52 78 79.66 21 56 13 21 56 23 6.8 7 0.40 0.30 1.0 0.33 0.04
Coffee Grounds 88 20 36 0 16 13 41 68 77 10 15.0 2 0.10 0.08
Corn Whole Plant Pelleted
91 63 64 34 64 9 45 21 24 40 6 2.4 6 0.50 0.24 0.9 0.14
Corn Fodder 80 65 66 37 66 9 45 25 29 48 100 2.4 7 0.50 0.25 0.9 0.20 0.14
Corn Stover Mature (Stalks)
80 54 54 20 54 5 30 35 43 70 100 1.3 7 0.45 0.15 1.2 0.30 0.14 22
Corn Silage, Milk Stage
26 65 66 37 66 8 18 26 32 54 60 2.8 6 0.40 0.27 1.6 0.11 20
Corn Silage, Mature Well
Eared 34 72 75 47 74 72.88 8 28 21 27 46 70 3.1 5 0.28 0.23 1.1 0.20 0.13 22
Corn Silage, Sweet Corn
24 65 66 37 66 11 20 32 57 60 5.0 5 0.24 0.26 1.2 0.17 0.16 39
Corn Grain, Whole
88 88 98 65 91 88.85 9 58 2 3 9 60 4.3 2 0.02 0.30 0.4 0.05 0.14 18
Corn Grain, Rolled
88 88 98 65 91 9 54 2 3 9 34 4.3 2 0.02 0.30 0.4 0.05 0.14 18
Corn Grain, Steam Flaked
85 93 104 71 97 95.44 9 59 2 3 9 40 4.1 2 0.02 0.27 0.4 0.05 0.14 18
Corn Grain, High Moisture
74 93 104 71 97 91.64 10 42 2 3 9 0 4.0 2 0.02 0.30 0.4 0.06 0.14 20
Corn Grain, High Oil
88 91 102 69 95 8 54 2 3 8 60 6.9 2 0.01 0.30 0.3 0.05 0.13 18
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Feedstuff DM %
Energy Protein Fiber
EE%
ASH%
Ca %
P %
K %
Cl%
S %
Zn ppmTDN
% NEm NEg NEl
(Mcal/cwt.)
DE (% of
GE)a
CP%
UIP%
CF%
ADF%
NDF%
eNDF%
Corn Grain, Hi-Lysine
92 87 96 64 90 12 58 4 4 11 60 4.4 2 0.03 0.24 0.4 0.05 0.11 18
Corn and Cob Meal
87 82 89 59 85 83.15 9 52 9 11 26 56 3.7 2 0.06 0.27 0.5 0.05 0.13 16
Corn Cobs 90 48 48 9 47 53.18 3 70 36 39 88 56 0.6 2 0.12 0.04 0.8 0.27 5
Corn Screenings
86 91 102 69 95 10 52 3 4 9 20 4.3 2 0.04 0.27 0.4 0.05 0.12 16
Corn Bran 91 76 81 52 78 11 10 17 51 0 6.3 3 0.04 0.15 0.1 0.13 0.08 18
Corn Germ, Full-fat
97 135 198 160 198 12 55 6 11 36 20 44.9 2 0.02 0.28 0.1 0.02 0.17 60
Corn Gluten Feed
90 80 86 56 83 78.47 22 25 9 12 38 36 3.2 7 0.11 0.84 1.3 0.25 0.47 84
Corn Gluten Meal 41% CP
91 85 93 62 88 46 63 5 9 32 23 3.2 3 0.13 0.55 0.2 0.07 0.62 35
Corn Gluten Meal 60% CP
91 89 99 67 93 75.29 67 65 3 6 11 23 2.5 2 0.06 0.54 0.2 0.10 0.90 40
Corn Cannery Waste
29 68 70 41 69 8 15 28 36 59 0 3.0 5 0.10 0.29 1.0 0.13 25
Cottonseed, Whole
91 95 107 73 99 23 38 27 37 47 100 19.4 5 0.16 0.64 1.0 0.06 0.24 34
Cottonseed, Whole, Delinted
90 95 107 73 99 24 39 19 28 40 100 22.9 5 0.12 0.54 1.2 0.24 36
Cottonseed, Whole,
Extruded 92 87 98 67 91 26 50 32 44 53 33 9.5 5 0.17 0.68 1.3 0.24 38
Cotton Gin Trash (Burrs)
91 42 43 0 40 9 35 50 70 100 2.0 14 1.40 0.18 1.9 0.14 25
Cottonseed Hulls
90 45 45 3 44 44.30 5 45 48 70 87 100 1.8 3 0.15 0.08 1.0 0.02 0.05 10
Cottonseed Meal, Solv. Ext.
41% CP 90 77 82 53 79 72.85 47 42 13 18 25 23 1.5 7 0.22 1.23 1.6 0.05 0.44 66
Cottonseed Meal, Mech. Ext. 41% CP
92 79 85 55 81 71.71 46 50 13 19 31 23 5.0 7 0.21 1.18 1.6 0.05 0.42 64
Crab Waste Meal
91 29 37 0 30 32 65 11 13 3.0 43 15.00 1.88 0.5 1.63 0.27 107
Crambe Meal, Solv. Ext.
91 81 88 58 84 31 45 25 35 47 23 1.4 8 1.27 0.86 1.1 0.70 1.26 44
Crambe Meal, Mech. Ext.
92 88 98 65 91 28 50 24 33 42 25 17.0 7 1.22 0.78 1.0 0.65 1.18 41
Cranberry Pulp Meal
88 49 49 11 48 7 26 47 54 33 15.7 2
Crawfish Waste Meal
94 25 36 0 29 35 74 12 15 42 13.10 0.85
Curacao Phosphate
99 0 0 0 0 0 0 0 0 0 0.0 95 34.00 15.00
Defluorinated Phosphate
99 0 0 0 0 0 0 0 0 0 0.0 95 32.60 18.07 1.0 100
Diammonium Phosphate
98 0 0 0 0 115 0 0 0 0 0 0.0 35 0.52 20.41 0.0 2.16
Dicalcium Phosphate
96 0 0 0 0 0 0 0 0 0 0.0 94 22.00 18.65 0.1 1.00 70
Distillers Grains, Wet
25 91 102 69 95 28 52 8 18 40 4 9.6 5 0.10 0.70 1.0 0.20 0.60 95
Distillers Grain, Barley
90 75 79 50 77 30 56 16 20 44 4 8.5 4 0.15 0.67 1.0 0.18 0.43 50
Distillers Grain, Corn, Dry
91 95 106 72 99 76.86 30 58 8 16 44 4 9.5 4 0.09 0.75 0.9 0.14 0.70 65
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Feedstuff DM %
Energy Protein Fiber
EE%
ASH%
Ca %
P %
K %
Cl%
S %
Zn ppmTDN
% NEm NEg NEl
(Mcal/cwt.)
DE (% of
GE)a
CP%
UIP%
CF%
ADF%
NDF%
eNDF%
Distillers Grain, Corn, Wet
36 97 109 74 102 30 47 8 16 44 4 9.5 4 0.09 0.75 0.9 0.14 0.70 65
Distillers Grain, Corn with Solubles
89 98 111 76 103 81.50 30 54 8 16 38 4 11.9 6 0.20 0.75 0.9 0.18 0.80 85
Distillers Dried Solubles
93 87 96 64 91 79.45 31 47 4 7 22 4 13.0 8 0.35 1.20 1.8 0.28 1.10 91
Distillers Corn Stillage
7 92 103 70 96 22 55 8 10 21 0 8.1 5 0.14 0.72 0.2 0.60 60
Distillers Grain, Sorghum, Dry
91 84 92 61 87 72.85 33 62 13 20 44 4 10.0 4 0.20 0.68 0.3 0.50 50
Distillers Grain, Sorghum, Wet
35 86 95 63 89 33 55 13 19 43 4 10.0 4 0.20 0.68 0.3 0.50 50
Distillers Grain, Sorghum with
Solubles 92 85 93 62 88 33 53 12 18 42 4 10.0 4 0.23 0.70 0.5 0.70 55
Elephant (Napier) Grass Hay, Chopped
92 55 55 21 54 9 24 46 63 85 2.0 10 0.35 0.30 1.3 0.10
Fat, Animal, Poultry,
Vegetable 99 195 285 230 285
80.08f
0 0 0 0 0 99.0 0 0.00 0.00 0.0
Feather Meal Hydrolyzed
93 67 69 40 68 87 68 1 14 42 23 7.0 3 0.48 0.45 0.1 0.20 1.82 90
Fescue KY 31 Fresh
29 64 65 36 65 15 20 25 32 64 40 5.5 9 0.48 0.37 2.5 0.18 22
Fescue KY 31 Hay Early
Bloom 88 60 60 30 60 53.57 18 22 25 31 64 98 6.6 8 0.48 0.36 2.6 0.27 24
Fescue KY 31 Hay Mature
88 52 52 16 51 11 30 30 42 73 98 5.0 6 0.45 0.26 1.7 0.14 22
Fescue (Red) Straw
94 43 44 0 41 4 41 1.1 6 0.00 0.06
Fish Meal 90 74 78 49 76 66 60 1 2 12 10 9.0 20 5.55 3.15 0.7 0.76 0.80 130
Flax Seed Hulls 91 38 40 0 36 9 32 39 50 98 1.5 10
Garbage Municipal Cooked
23 80 86 56 83 16 9 50 59 30 20.0 10 1.20 0.43 0.6 0.67
Glycerol (Glycerin)
88 90 100 68 94 0 0 0 0 0 0 0.0 6 4.00
Grain Screenings
90 65 66 37 66 14 14 5.5 9 0.25 0.34 30
Grain Dust 92 73 77 48 75 10 11 2.2 10 0.30 0.18 42
Grape Pomace Stemless
91 40 42 0 38 27.50 12 45 32 46 54 34 7.6 9 0.55 0.07 0.6 0.01 24
Grass Hay 88 58 58 26 58 10 30 33 41 63 98 3.0 6 0.60 0.21 2.0 0.20 28
Grass Silage 30 61 62 31 61 11 24 32 39 60 61 3.4 8 0.70 0.24 2.1 0.22 29
Guar Meal 90 72 75 47 74 39 34 16 3.9 5
Hominy Feed 90 89 99 67 93 11 48 5 8 21 9 6.5 3 0.04 0.55 0.6 0.06 0.10 32
Hop Leaves 37 49 49 11 48 15 15 3.6 35 2.80 0.64
Hop Vine Silage 30 53 53 18 53 15 21 24 3.1 20 3.30 0.37 1.8 0.22 44
Hops Spent 89 35 39 0 33 23 26 30 4.6 7 1.60 0.60
Kelp Dried 91 32 38 0 29 54.67 7 7 10 0.5 39 2.72 0.31
Kenaf Hay 92 48 48 9 47 10 31 44 56 98 2.9 12
Kochia Fresh 29 55 55 21 55 65.11 16 23 1.2 18 1.10 0.30
Kochia Hay 90 53 53 18 53 14 27 1.7 14 1.00 0.20
Kudzu Hay 90 54 54 20 54 16 33 2.6 7 3.00 0.23
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FeedstuffDM %
Energy Protein Fiber
EE%
ASH%
Ca %
P %
K %
Cl%
S %
Zn ppmTDN
%NEm NEg NEl
(Mcal/cwt.)
DE (% of
GE)a
CP%
UIP%
CF%
ADF%
NDF%
eNDF%
Lespedeza Fresh Early
Bloom 25 60 60 30 60 16 50 32 2.0 10 1.20 0.24 1.1 0.21
Lespedeza Hay 92 54 54 20 54 14 60 30 3.0 7 1.10 0.22 1.0 0.19 29
Limestone Ground
98 0 0 0 0 0 0 0 0 0 0 0.0 98 34.00 0.02 0.03
Limestone Dolomitic Ground
99 0 0 0 0 0 0 0 0 0 0 0.0 98 22.30 0.04 0.4
Linseed Meal, Solv. Ext.
91 77 82 53 79 38 36 10 18 25 23 1.7 6 0.43 0.91 1.5 0.04 0.47 60
Linseed Meal, Mech. Ext.
91 82 89 59 85 37 40 10 17 24 23 6.0 6 0.42 0.90 1.4 0.04 0.46 59
Meadow Hay 90 50 50 12 49 63.37 7 23 33 44 70 98 2.5 9 0.61 0.18 1.6 0.17 24
Meat Meal, Swine/Poultry
93 71 74 46 73 56 64 2 7 48 0 10.5 24 9.00 4.42 0.5 1.27 0.48 190
Meat and Bone Meal,
Swine/Poultry 93 72 75 47 74 56 24 1 5 34 0 10.0 29 13.50 6.50
Milk, Dry, Skim 94 87 96 64 90 36 0 0 0 0 0 0.9 8 1.36 1.09 1.7 0.96 0.34 41
Mint Slug Silage 27 55 55 21 55 14 24 1.8 16 1.10 0.57
Molasses Beet 77 75 79 50 77 91.95 8 0 0 0 0 0 0.2 12 0.14 0.03 6.0 1.64 0.60 18
Molasses Cane 77 74 78 49 76 86.63 6 0 0 0 0 0 0.5 14 0.95 0.09 4.2 2.30 0.68 15
Molasses Cane Dried
94 74 78 49 76 82.12 9 0 2 3 7 0 0.3 14 1.10 0.15 3.6 3.00 30
Molasses, Cond.
Fermentation Solubles
43 69 71 43 70 16 0 0 0 0 0 1.0 26 2.12 0.14 7.5 2.73 0.93 30
Molasses Citrus 65 75 79 50 77 84.11 9 0 0 0 0 0 0.3 8 1.84 0.15 0.2 0.11 0.23 137
Molasses Wood,
Hemicellulose 61 70 73 44 71 1 0 1 2 4 0 0.6 7 1.10 0.10 0.1 0.05
Monoammonium Phosphate
98 0 0 0 0 70 0 0 0 0 0 0.0 24 0.30 24.70 0.0 1.42 81
Mono-Dicalcium Phosphate
97 0 0 0 0 0 0 0 0 0 0.0 94 16.70 21.10 0.1 1.20 70
Oat Hay 90 54 54 20 54 59.36 10 25 31 39 63 98 2.3 8 0.40 0.27 1.6 0.42 0.21 28
Oat Silage 35 60 60 30 60 64.00
g 12 21 31 39 59 61 3.2 10 0.34 0.30 2.4 0.50 0.25 27
Oat Straw 91 48 48 9 47 49.64 4 40 41 48 73 98 2.3 8 0.24 0.07 2.5 0.78 0.22 6
Oat Grain 89 76 81 52 78 75.63 13 18 11 15 28 34 5.0 4 0.05 0.41 0.5 0.11 0.20 40
Oat Grain, Steam Flaked
84 88 98 65 91 13 26 11 15 30 32 4.9 4 0.05 0.37 0.5 0.11 0.20 40
Oat Groats 91 91 102 69 95 88.29 18 15 3 6.6 2 0.08 0.47 0.4 0.10 0.20
Oat Middlings 90 91 102 69 95 16 20 4 6 6.0 3 0.07 0.48 0.5 0.23
Oat Mill Byproduct
89 33 38 0 30 7 27 37 2.4 6 0.13 0.22 0.6 0.24
Oat Hulls 93 38 40 0 36 38.39 4 25 33 41 75 90 1.6 7 0.16 0.15 0.6 0.08 0.14 31
Orange Pulp Dried
89 79 85 55 81 9 9 16 20 33 1.8 4 0.71 0.11 0.6 0.05
Orchardgrass Fresh Early
Bloom 24 65 66 37 66 60.13 14 23 30 32 54 41 4.0 9 0.33 0.39 2.7 0.08 0.20 21
Orchardgrass Hay
88 59 59 28 59 64.29
h 10 27 34 40 67 98 3.3 8 0.32 0.30 2.6 0.41 0.20 26
Pea Vine Hay 89 59 59 28 59 11 32 50 62 92 2.0 7 1.25 0.24 1.3 0.20 20
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FeedstuffDM %
Energy Protein Fiber
EE%
ASH%
Ca %
P %
K %
Cl%
S %
Zn ppmTDN
%NEm NEg NEl
(Mcal/cwt.)
DE (% of
GE)a
CP%
UIP%
CF%
ADF%
NDF%
eNDF%
Pea Vine Silage 25 58 58 26 58 16 29 44 55 61 3.3 8 1.25 0.28 1.6 0.29 32
Pea Vine Straw 89 51 51 14 50 49.62 7 41 49 72 98 1.4 7 0.75 0.13 1.1 0.15
Peas Cull 88 85 93 62 88 23 22 7 9 12 0 1.4 4 0.14 0.46 1.1 0.06 0.26 30
Peanut Hulls 91 22 36 0 18 23.17 7 63 65 74 98 1.5 5 0.20 0.07 0.9
Peanut Meal, Solv. Ext.
91 77 82 53 79 71.90 51 27 9 16 27 23 2.5 6 0.26 0.62 1.1 0.03 0.30 38
Peanut Skins 92 0 0 0 0 17 13 20 28 0 22.0 3 0.19 0.20
Pearl Millet Grain
87 82 89 59 85 68.04 13 2 6 18 34 4.5 3 0.03 0.36 0.5
Pineapple Greenchop
17 47 47 7 46 8 24 35 64 41 2.4 7 0.28 0.08
Pineapple Bran 89 71 74 46 73 72.43 5 20 33 66 20 1.5 3 0.26 0.12
Pineapple Presscake
21 71 74 46 73 5 24 35 69 20 0.8 3 0.25 0.09
Potato Vine Silage
15 59 59 28 59 15 26 3.7 19 2.10 0.29 4.0 0.37
Potatoes Cull 21 80 86 56 83 10 0 2 3 4 0 0.4 5 0.03 0.24 2.2 0.30 0.09
Potato Waste Wet
14 82 89 59 85 7 0 9 11 18 0 1.5 3 0.16 0.25 1.2 0.36 0.11 12
Potato Waste Dried
89 85 93 62 88 95.85 8 0 7 9 15 0 0.5 5 0.16 0.25 1.2 0.39 0.11 12
Potato Waste Wet with Lime
17 80 86 56 83 5 0 10 12 16 0 0.3 9 4.20 0.18
Potato Waste Filter Cake
14 77 82 53 79 5 0 2 7.7 3 0.10 0.19 0.2
Poultry Byproduct Meal
93 79 85 55 81 62 49 2 14.5 17 4.00 2.25 0.5 0.58 0.56 129
Poultry Manure Dried
89 38 40 0 36 67.83 28 22 13 15 35 0 2.1 33 10.20 2.80 2.3 1.05 0.20 520
Prairie Hay 91 50 50 12 49 55.53 7 37 34 47 67 98 2.0 8 0.40 0.15 1.1 0.06 0.06 34
Pumpkins, Cull 11 80 86 56 83 15 14 21 30 0 8.9 9 0.24 0.43 3.3
Rice Straw 91 40 42 0 38 51.16 4 38 47 72 100 1.4 13 0.23 0.08 1.2 0.11
Rice Straw Ammoniated
87 45 45 3 44 9 39 53 68 100 1.3 12 0.25 0.08 1.1 0.11
Rice Grain 89 79 85 55 81 83.86 8 30 10 12 16 34 1.9 5 0.07 0.32 0.4 0.09 0.05 17
Rice Polishings 90 90 100 68 94 14 4 5 14.0 9 0.05 1.34 1.2 0.12 0.19 28
Rice Bran 91 71 74 46 73 66.64 14 30 13 18 24 0 16.0 11 0.07 1.70 1.8 0.09 0.19 40
Rice Hulls 92 13 35 0 8 15.91 3 45 44 70 81 90 0.9 20 0.12 0.07 0.5 0.08 0.08 24
Rice Mill Byproduct
91 39 41 0 37 7 32 50 60 0 5.7 19 0.25 0.48 2.2 0.30 31
Rye Grass Hay 90 58 58 26 58 66.07
i 10 30 33 38 65 98 3.3 8 0.45 0.30 2.2 0.18 27
Rye Grass Silage
32 59 59 28 59 14 25 22 37 59 61 3.3 8 0.43 0.38 2.9 0.73 0.23 29
Rye Straw 89 44 44 1 43 33.72 4 44 55 71 100 1.5 6 0.24 0.09 1.0 0.24 0.11
Rye Grain 89 80 86 56 83 84.83 14 20 3 9 19 34 2.5 3 0.07 0.55 0.5 0.03 0.17 33
Safflower Meal, Solv. Ext.
91 56 56 23 56 57.72 24 33 41 57 36 1.3 6 0.35 0.79 0.9 0.21 0.23 65
Safflower Meal Dehulled, Solv.
Ext. 91 75 79 50 77 70.55 47 11 20 27 30 0.8 7 0.38 1.50 1.2 0.18 0.22 36
Safflower Hulls 91 14 35 0 34 4 58 73 90 100 3.7 2
Sagebrush Fresh
50 50 50 12 49 59.04
j 13 25 30 38 9.2 10 1.00 0.25 0.22
Sanfoin Hay 88 61 62 31 62 14 60 24 3.1 9
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Feedstuff DM %
Energy Protein Fiber
EE%
ASH%
Ca %
P %
K %
Cl%
S %
Zn ppmTDN
% NEm NEg NEl
(Mcal/cwt.)
DE (% of
GE)a
CP%
UIP%
CF%
ADF%
NDF%
eNDF%
Shrimp Waste Meal
90 48 48 9 47 50 60 11 5.5 25 8.50 1.75 1.15
Sodium Tripolyphosphat
e 96 0 0 0 0 0 0 0 0 0 0.0 96 0.00 25.98 0.0 0.00
Sorghum Stover 87 54 54 20 54 5 33 41 65 100 1.8 10 0.50 0.12 1.2
Sorghum Silage 32 59 59 28 59 65.58 9 25 27 38 59 70 2.7 6 0.48 0.21 1.7 0.45 0.11 30
Sorghum Grain (Milo), Ground
89 82 89 59 85 11 55 3 6 15 5 3.1 2 0.04 0.32 0.4 0.10 0.14 18
Sorghum Grain (Milo), Flaked
82 90 100 68 94 11 62 3 6 15 38 3.1 2 0.04 0.28 0.4 0.10 0.14 18
Soybean Hay 89 52 52 16 51 54.10 16 33 40 55 92 3.5 8 1.28 0.29 1.0 0.15 0.24 24
Soybean Straw 88 42 43 0 40 45.98 5 44 54 70 100 1.4 6 1.59 0.06 0.6 0.26
Soybeans Whole
88 92 103 70 96 41 28 8 11 15 100 18.8 5 0.27 0.64 1.9 0.03 0.34 56
Soybeans Whole,
Extruded 88 93 104 71 97 40 35 9 11 15 100 18.8 5 0.27 0.64 2.0 0.03 0.34 56
Soybeans Whole, Roasted
88 93 104 71 97 40 48 9 11 15 100 18.8 5 0.27 0.64 2.0 0.03 0.34 56
Soybean Hulls 90 77 82 52 79 66.86 13 28 39 48 62 28 2.3 5 0.60 0.19 1.3 0.02 0.12 38
Soybean Meal, Solv. Ext. 44%
CP 89 84 92 61 87 79.50 49 35 7 10 15 23 1.5 7 0.36 0.70 2.2 0.07 0.41 62
Soybean Meal, Solv. Ext. 49%
CP 89 87 96 64 90 54 36 4 6 8 23 1.3 7 0.28 0.71 2.2 0.08 0.45 61
Soybean Mill Feed
90 50 50 12 49 15 36 46 1.9 6 0.46 0.19 1.7 0.07
Spelt Grain 88 75 79 50 77 77.18 13 27 10 17 21 34 2.1 4 0.04 0.40 0.4 0.15 47
Sudangrass Fresh Immature
18 70 73 44 71 73.27 17 23 29 55 41 3.9 9 0.46 0.36 2.0 0.11 24
Sudangrass Hay
88 57 57 25 57 62.67 9 30 36 43 67 98 1.8 10 0.50 0.22 2.2 0.80 0.12 26
Sudangrass Silage
31 58 58 26 58 60.29 10 28 30 42 64 61 3.1 10 0.58 0.27 2.4 0.52 0.14 29
Sunflower Meal, Solv. Ext.
92 65 66 37 66 44.89 40 27 18 22 36 23 2.8 8 0.44 0.97 1.1 0.15 0.33 55
Sunflower Meal with Hulls
91 57 57 25 57 31 35 27 32 44 37 2.4 7 0.40 1.03 1.0 0.30 85
Sunflower Seed Hulls
90 40 42 0 38 4 65 52 63 73 90 2.2 3 0.00 0.11 0.2 0.19 200
Sugar Cane Bagasse
91 39 41 0 37 52.15 1 49 60 86 100 0.6 4 0.90 0.29 0.5 0.10
Tapioca Meal, Cassava
Byproduct 89 82 89 59 85 1 5 8 34 0.8 3 0.03 0.05
Timothy Fresh Pre-Bloom
26 64 65 36 65 11 20 31 36 59 41 3.8 7 0.40 0.28 1.9 0.57 0.15 28
Timothy Hay Early Bloom
88 59 59 28 59 60.75 11 22 32 39 63 98 2.7 6 0.58 0.26 1.9 0.51 0.21 30
Timothy Hay Full Bloom
88 57 57 25 57 58.68 8 30 34 40 65 98 2.6 5 0.43 0.20 1.8 0.62 0.13 25
Timothy Silage 34 59 59 28 59 59.32 10 25 34 45 70 61 3.4 7 0.50 0.27 1.7 0.15
Tomatoes 6 69 71 43 70 16 9 11 4.0 6 0.14 0.35 4.2
Tomato Pomace Dried
92 64 65 36 65 53.98 23 26 50 55 34 10.6 6 0.43 0.59 3.6
Triticale Hay 90 56 56 23 56 10 34 41 69 98 0.30 0.26 2.3 25
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Feedstuff DM %
Energy Protein Fiber
EE%
ASH%
Ca %
P %
K %
Cl%
S %
Zn ppmTDN
% NEm NEg NEl
(Mcal/cwt.)
DE (% of
GE)a
CP%
UIP%
CF%
ADF%
NDF%
eNDF%
Triticale Silage 34 58 58 26 58 14 30 39 56 61 3.6 0.58 0.34 2.7 0.28 36
Triticale Grain 89 85 93 62 88 83.82 14 25 4 5 22 34 2.4 2 0.07 0.39 0.5 0.17 37
Turnip Tops (Purple)
18 68 70 41 69 18 10 13 2.6 14 3.10 0.40 3.0 1.80 0.27
Turnip Roots 9 86 95 63 89 92.94 12 0 11 34 44 40 1.6 9 0.65 0.31 3.1 0.65 0.43 40
Urea 46% N 99 0 0 0 0 288 0 0 0 0 0 0.0 0 0.00 0.00 0.0 0.00 0.00 0
Vetch Hay 89 58 58 26 58 59.44 18 14 30 33 48 92 1.8 8 1.25 0.34 2.4 0.13
Wheat Fresh, Pasture
21 71 74 46 73 76.07 20 16 18 30 50 41 4.0 13 0.35 0.36 3.1 0.67 0.22
Wheat Hay 90 57 57 25 57 62.73 9 25 29 38 66 98 2.0 8 0.21 0.22 1.4 0.50 0.19 23
Wheat Silage 33 59 59 28 59 63.99 12 21 28 37 62 61 3.2 8 0.40 0.28 2.1 0.50 0.21 27
Wheat Straw 91 43 44 0 41 45.77 3 60 43 57 81 98 1.8 8 0.17 0.06 1.3 0.32 0.17 6
Wheat Straw Ammoniated
85 50 50 12 49 9 25 40 55 76 98 1.5 9 0.15 0.05 1.3 0.30 0.16 6
Wheat Grain 89 88 98 65 91 86.45
k 14 23 3 4 12 0 2.3 2 0.05 0.43 0.4 0.09 0.15 40
Wheat Grain Hard
89 88 98 65 91 88.54
l 14 28 3 6 14 0 2.0 2 0.05 0.43 0.5 0.16 45
Wheat Grain Soft
89 88 98 65 91 89.96
m 12 23 3 4 12 0 2.0 2 0.06 0.40 0.4 0.15 30
Wheat Grain, Steam Flaked
85 91 102 69 95 14 29 3 4 12 0 2.3 2 0.05 0.39 0.4 0.15 40
Wheat Grain Sprouted
86 88 98 65 91 12 18 3 4 13 0 2.0 2 0.04 0.36 0.4 0.17 45
Wheat Bran 89 70 73 44 71 71.16 17 28 11 14 46 4 4.4 7 0.13 1.32 1.4 0.05 0.24 96
Wheat Middlings
89 80 86 56 83 18 22 8 11 36 2 4.7 5 0.14 1.00 1.3 0.05 0.20 98
Wheat Mill Run 90 76 81 52 78 79.11 17 28 9 12 37 0 4.5 6 0.11 1.10 1.2 0.07 0.22 90
Wheat Shorts 89 78 83 54 80 19 25 8 10 30 0 5.3 5 0.10 0.93 1.1 0.08 0.20 118
Wheatgrass Crested Fresh Early Bloom
37 60 60 30 60 79.78 11 25 26 28 50 41 1.6 7 0.46 0.32 2.4
Wheatgrass Crested Fresh
Full Bloom 50 55 55 21 55 65.89 10 33 33 36 65 41 1.6 7 0.39 0.28 2.1
Wheatgrass Crested Hay
92 54 54 20 54 56.51 10 33 33 36 65 98 2.4 7 0.33 0.20 2.0 32
Whey Dried 94 82 89 59 85 91.47
n 14 15 0 0 0 0 0.9 10 0.98 0.88 1.3 1.20 0.92 10
Yeast, Brewer's 92 79 85 55 81 73.76 47 30 3 4 0 0.9 7 0.13 1.49 1.8
DM =Drymatter ADF = AciddetergentfiberTDN =Totaldigestiblenutrients NDF = NeutraldetergentfiberNEm =Netenergyformaintenance eNDF = effectiveneutraldetergentfiberNEg =Netenergyforgrowth EE = EtherextractNEl =Netenergyforlactation ASH =AshMcal =Megacalories Ca =Calciumcwt =Centumweight(hundredweight) P =PhosphorousDE =Digestibleenergy K = PotassiumGE =Grossenergy Cl =ChlorineCP =Crudeprotein S =SulfurUIP =Undegradableintakeprotein Zn =ZincCF =Crudefiber ppm =partspermillionaDE(%ofGE)valuesfromEwan(1989)bAverageoffresh,latevegetative;fresh,earlybloom;fresh,midbloom;fresh,fullbloomcAverageofsilagewilted–earlybloom;silagewilted–midbloom;silagewilted–fullbloomdAverageofsilagewilted–earlybloom;silagewilted–midbloom;silagewilted–fullbloom
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eAverageofhay–sun‐cured,latevegetative;hay–sun‐cured,latebloomfAverageoffat,animalpoultry;oil,vegetablegAverageofsilage,latevegetative;silage,doughstagehAverageofhay,sun‐cured,earlybloom;hay,sun‐cured,latebloomiAverageofryegrass,ItalianLoliummultiflorum:hay,sun‐cured,latevegetative;hay,sun‐cured,earlybloom;averageofryegrass,perennialLoliumperenne:hay,sun‐curedjAverageofsagebrush,bigArtemisiatridentate:browse,fresh,stem‐cured;sagebrush,budArtemisiaspinescens:browse,fresh,earlyvegetative;browse,fresh,latevegetative;andsagebrush,fringedArtemisiafrigida:browse,fresh,midbloom;browse,fresh,maturekAverageofwheat,DurumTriticumdurumandwheatTriticumaestivumgrainlAverageofgrain,hardredspring;grain,hardwintermAverageofgrain,softredwinter;grain,softwhitewinter;grain,softwhitewinter,pacificcoastnAverageofdehydrated(cattle)andlowlactose,lowlactose,dehydrated(driedwheyproduct)(cattle)
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Appendix5‐C:EstimationMethodsforAmmoniaEmissionsfromManureManagementSystemsThisappendixpresentsmethodsforestimatingNH3frommanuremanagementsystems.NH3,althoughnotaGHG,isemittedinlargequantitiesfromanimalhousingandmanuremanagementsystemsandisanindirectprecursortonitrousoxide(N2O)emissionsaswellasanenvironmentalconcern.
5‐C.1 MethodforEstimatingAmmoniaEmissionsUsingEquationsfromIntegratedFarmSystemModel
Ammoniaemissionsfrommanurestoragearemainlyfromtotalammoniacalnitrogen(TAN).Formanyanimalconfinementsystems,ithasbeenreportedthatmostoftheureainmanurehasbeenconvertedtoTANandlostasNH3bythetimemanureistransferredtostorage(Rotzetal.,2011b);therefore,onlyorganicnitrogeninthemanureatthestoragestage,whichismineralizedtoTAN,isusedtoestimateNH3release.TherearefourmainstepsrelatedtoNH3releasetotheatmosphere:diffusion,dissociation,aqueoustogaspartitioning,andmasstransportawayfromthemanuresurface(Rotzetal.,2011b).Forsolidmanure,diffusionthroughthemanureisamainconstrainttotheemissionrate.Forliquidmanure,NH3emissionsareafunctionoftheoverallmasstransferrateandthedifferenceintheNH3concentrationbetweenthelagoonandthesurroundingatmosphere.
5‐C.1.1 RationaleforSelectedMethod
Ammoniaemissionsfromtemporarystackandlongtermstockpiles,aerobiclagoons,anaerobiclagoons,runoffholdingponds,andstoragetankscanbecalculatedusingequationsfromtheDairyGEMModel(asubsetoftheIntegratedFarmSystemModel)(Rotzetal.,2011b).TheequationsfromRotzetal.aretheonlyavailablemethodsforestimatingNH3emissionsfromthesesystemsandbestdescribesthequantitativerelationshipamongstactivitydataattheentitylevel.
5‐C.1.2 ActivityData
InordertoestimatethedailyNH3emissionfromtemporarystack,long‐termstockpiles,anaerobiclagoons,runoffholdingponds,andstoragetanks,thefollowinginformationisneeded:
Totalnitrogencontentofmanure ManuretotalNH3‐Ncontent Surfaceareaofmanurepile Temperatures(localambienttemperatureandmanuretemperature) Localambientairvelocity Foraerobiclagoons,thepHofthelagoonisalsoneeded.
Thetimingofmeasurementscanbebasedondietarychangesorseasonaltimeframe,whichisdecidedbyindividualfarmentity.However,duetothedynamicnatureofmanurepilescausingthe
Ammonia
Methodisafunctionofthesurfaceareaofthestorageunit,resistancetomasstransfer,ambientairvelocity,totalNH3andorganicnitrogencontent,rateoforganicnitrogentransformationtototalammoniacalnitrogen,andmanuretemperatureasdefinedbyRotzetal.(2011b).
Ammoniaandorganicnitrogencontentcanbeobtainedfromsamplingandlabtesting.
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changesofthevariables,frequentmeasurementsofmanurecharacteristicsarerecommendedtoensureaccuracyoftheestimation.
5‐C.1.3 AncillaryData
TheancillarydatausedtoestimateNH3emissionfortemporarystoragearekinematicviscosityofair,massdiffusivityofNH3,andresistancetomasstransfer.ThekinematicviscosityofairatstandardatmosphericpressureislistedinTable5‐C‐1.ThemassdiffusivityofNH3isobtainedfromreferences(PaulandWatson,1966;Baker,1969)andlistedinTable5‐C‐2.TheresistancetomasstransferfordifferentsolidmanurestoragesareobtainedfromtheDairyGEMmodel(Rotzetal.,2011a).
5‐C.2 MethodforAmmoniaEmissionsfromTemporaryStack,Long‐TermStockpile,AnaerobicLagoons/RunoffHoldingPonds/StorageTanks,andAerobicLagoons
TemporaryStack,Long‐TermStockpile,andAnaerobicLagoons/RunoffHoldingPonds/StorageTanksAsindicatedinEquation5‐C‐1,NH3emissionsareafunctionoftheoverallmasstransferrateandthedifferenceinNH3concentrationbetweenthemanureandsurroundingatmosphere.ThemeanambientairNH3concentrationis1.3µg/m3basedonpassivemeasurementsfrom35locationsacross24StatesintheU.S.withoneyearormoreofmeasurements(AmmoniaMonitoringNetwork,NationalAtmosphericDepositionProgram).TheHenry’sLawconstantisusedtodefinetheratioofNH3concentrationinasolutioninequilibriumwithgaseousNH3concentrationinairandisexponentiallyrelatedtotemperature.
aAmmoniaconcentrationinambientaircanbeobtainedfromNationalAtmosphericDepositionProgram(nadp.sws.uiuc.edu/amon/).bShapefactors( )arelistedinAppendix5‐D.
Equation5‐C‐2describesthecalculationforHenry’sLawConstant.Themanuretemperatureiscalculatedastheaverageambienttemperatureovertheprevious10days.
Equation5‐C‐1:AmmoniaEmissionsfromTemporaryStack,LongTermStockpiles,andAnaerobicLagoons/RunoffHoldingPonds/StorageTanks
Where:
ENH3 =NH3emissionsperday(kgNH3day‐1)
24 =Hoursperday(hrday‐1)
3,600 =Secondsperhour(shr‐1)
Asurface =Footprintofmanurestorage(m2)×shapefactorb
K =Overallmasstransfercoefficient(ms‐1)asdefinedinEquation5‐C‐3
TANm =Totalammoniacalnitrogeninthemanure(kgm‐3)
TANa =NH3concentrationinambientaira(kgm‐3)
H =Henry’sLawconstantasdefinedinEquation5‐C‐2
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Theoverallmasstransfercoefficientisexpressedasthereciprocaloftheoveralleffectiveresistanceofthemanure.ThemasstransfercoefficientthroughgaseousphaseonthetopofmanureiscalculatedusingEquation5‐C‐3.TheresistancetomasstransferiscalculatedinEquation5‐C‐5.IthasbeenreportedthatthemasstransfercoefficientthroughmanurehasrelativelylittleeffectonthemasstransferofNH3(Ni,1999)andthusthe1/Klisconsiderednegligibleinthefollowingequation.
Themasstransfercoefficientthroughgaseousphase(Equation5‐C‐4)isestimatedfromtheairfrictionvelocityandSchmidtnumberofair.TheTurbulentSchmidtnumberisdependentonthecharacteristicsofthegasandthescalesofatmosphericturbulence.Sinceturbulenceishighlydependentonmanycomplexinteractions,theTurbulentSchmidtnumberwasapproximatedbyonlyaccountingforthegascharacteristics.ThesecharacteristicsareexpressedinthemolecularSchmidtnumber,definedasSC=ν/D,whereνisthekinematicviscosityofair(m2s‐1),andDisthemassdiffusivityofNH3(m2s‐1).InordertocalculateSchmidtnumber,thedynamicviscosityofair,thedensityoftheair,andthemassdiffusivityofNH3aregivenbasedonairtemperatureinTable5‐C‐1andTable5‐C‐2.
Equation5‐C‐2:CalculationHenry’sLawConstant
..
Where:
H=Henry’sLawconstantforNH3(aqueoustogas)
T=Manuretemperature(Kelvindegree)
Equation5‐C‐3:OverallMassTransferCoefficient
Where:
K =Overallmasstransfercoefficient(ms‐1)
H =Henry’sLawconstantforNH3(aqueoustogas)
Rm =Resistancetomasstransfer(sm‐1)
Kg =Masstransfercoefficientthroughgaseousphaseonthetopofmanure(ms‐1)
Kl =Masstransfercoefficientthroughmanure(ms‐1)
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ThemasstransfercoefficientthroughmanurehaslittleeffectonthemasstransferofNH3,soitisnegligible.Theresistancetomasstransferisthesumoftheresistancethroughthemanureandtheresistanceofcovermaterialsoverthemanure(Equation5‐C‐5).ThevaluesforresistancetomasstransferthroughthemanureandresistancetomasstransferthroughthecoverarelistedinTable5‐C‐3fortemporarystackandlong‐termstockpileandinTable5‐C‐4foranaerobiclagoons,runoffholdingponds,andstoragetanks.
Table5‐C‐3:ResistancetoMassTransferforSolidManureStorageTypeofManureStorage Rs(sm‐1) Rc(sm‐1)
Uncoveredsolidmanure(drymatter>15%) 3×105 0Coveredsolidmanure(drymatter>15%) 3×105 2×105Uncoveredslurrymanure(drymater,10‐15%) 2×105 0
Table5‐C‐1:KinematicViscosityofAiratDifferentTemperatureatStandard
AtmosphericPressure
Temperature(°C)KinematicViscosity
(m2/s)x10‐5‐40 1.04‐20 1.170 1.325 1.3610 1.4115 1.4720 1.5125 1.5630 1.6040 1.6650 1.76
Source:White(1999).
Table5‐C‐2:Mass DiffusivityofAmmoniaatStandardAtmosphericPressure
Temperature(°C)DiffusivityofAmmonia
(m2/s)x10‐4‐40 0.1060 0.11030 0.20040 0.20950 0.233
Source:PaulandWatson (1966)andBaker(1969).
Equation5‐C‐4:CalculatingMassTransferCoefficientthroughGaseousPhase
. . . . .
Where:
Kg=Masstransfercoefficientthroughgaseousphaseonthetopofmanure(ms‐1)
Va=Ambientairvelocity(ms‐1)thatcanbeobtainedfromNationalWeatherServicebysearchingthetargetlocation
SC=TurbulentSchmidtnumberofNH3intheairabovemanuresurface(dimensionless)
Equation5‐C‐5:CalculationofResistancetoMassTransfer
Where:
Rm=Resistancetomasstransfer(sm‐1)
Rs=Resistancetomasstransferthroughthemanure(sm‐1)
Rc=Resistancetomasstransferthroughthecover(sm‐1)
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TypeofManureStorage Rs(sm‐1) Rc(sm‐1)Coveredslurrymanure(drymater,10‐15%) 2×105 2×105
Source:Rotzetal.(2011b).Table5‐C‐4:ResistancetoMassTransferForAnaerobicLagoons,RunoffHoldingPonds,andStorageTanks
TypeofCover Rs(sm‐1) Rc(sm‐1)Uncoveredliquidmanure 0 0
Coveredliquidmanure 0 2×105Source:Rotzetal.(2011a).
AerobicLagoonsThemethodforestimatingNH3emissionsfromaerobiclagoons(Equation5‐C‐6)issimilartothatforstockpilesandanaerobiclagoonsbutaccountsfortheconcentrationofNH3intheliquid.
TheoverallmasstransfercoefficientiscalculatedusingEquation5‐C‐3withresistancetomasstransferassumedtobezero.Henry’sLawConstantiscalculatedusingEquation5‐C‐2andthemasstransfercoefficientthroughagaseousphaseiscalculatedusingEquation5‐C‐4.ThemasstransferthroughtheliquidfilmlayeriscalculatedusingEquation5‐C‐7.
Equation5‐C‐8describestheestimationmethodforNH3concentrationintheliquid.TheNH3fractionofTANinthelagoonliquidisafunctionofpHandadissociationconstantaccordingtoEquation5‐C‐9.
Equation5‐C‐6:ResistancetoMassTransferforSolidManureStorage(Rotzetal.,2011b)
Where:
ENH3 =NH3emissionsperday(kgday‐1)
24 =Hoursperday(hrday‐1)
3,600=Secondsperhour(sh‐1)
K =Overallmasstransfercoefficient(ms‐1)
Asurface=Surfaceareaoflagoon(m2)
NH3 =Concentrationintheliquid(kgm‐3)
Equation5‐C‐7:CalculatingtheMassTransferCoefficientthroughtheLiquidFilmLayer
Kl 1.417 10‐12 T4
Where:
Kl=Masstransfercoefficientthroughtheliquidfilmlayer(ms‐1)
T=Manuretemperature(Kelvin)
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5‐C.3 MethodforEstimatingAmmoniaEmissionsfromCompostingUsingIPCCTier2Equations
Compostingisthecontrolledaerobicdecompositionoforganicmaterialintoastable,humus‐likeproduct(USDANRCS,2007).Eghballetal.(1997)reportedthat19to45percentofthenitrogenpresentinmanurewaslostduringcomposting,withthemajorityofthispresumablyasNH3.
5‐C.3.1 RationaleforSelectedMethod
TheIPCCmethodisadaptedforestimatingNH3emissionsandincorporatesNH3emissionfactorsfromastudyofcompostingcattleandswinemanure(HellebrandandKalk,2000).TheIPCCequationistheonlyavailablemethodforestimatingNH3emissionsfromcomposting.Thismethodologybestdescribesthequantitativerelationshipamongstactivitydataattheentitylevel.
Equation5‐C‐8:CalculatingtheAmmoniaConcentrationintheLiquid
Where:
NH3 =Concentrationintheliquid(kgm‐3)
F =NH3ofTANinthelagoonliquid
TAN =Totalammonianitrogeninthemanureliquid(kgm‐3)
Equation5‐C‐9:CalculatingtheAmmoniaFractionofTANintheLagoonLiquid
Where:
F =NH3ofTANinthelagoonliquid
pH =Hydrogenionconcentration
Ka =Dissociationconstant,whereK 10 .
T =Temperature(Kelvin)
Ammonia
IPCCTier2approachadjustedtoestimateNH3emissionsutilizingdataonanNH3emissionfactor,totalinitialnitrogen,anddrymanure.
TheNH3emissionfactorisobtainedfromastudyofcompostingmixtureofcattleandswinemanurebyHellebrandandKalk(2000).
Nitrogencontentcanbeobtainedfromsamplingandlabtesting. Methodistheonlyreadilyavailablemethod.
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5‐C.3.2 ActivityData
InordertoestimatethedailyNH3emissions,thefollowinginformationisneeded:
Totaldrymanureinthestorage Totalnitrogeninmanure
Thetimingofmeasurementscanbebasedondietarychangesoronaseasonaltimeframe,whichisdecidedbyindividualfarmentity.However,duetothedynamicnatureofmanurestoragecausingchangesinthevariables,frequentmeasurementsofmanurecharacteristics(e.g.,volatilesolids,temperature,totaldrymanure)arerecommendedtoimproveaccuracyoftheestimation.
5‐C.3.3 AncillaryData
TheancillarydatausedtoestimateNH3emissionformanurecompostingisNH3emissionfactor(HellebrandandKalk,2000).
5‐C.4 MethodforAmmoniaEmissionsfromComposting
Ammoniaemissionsfromcompostingaredependentonvolatilizationandmineralizationafternitrification,decompositionoforganicnitrogencompounds,orureahydrolysis.AnIPCCTier2approachforestimatingN2OemissionsisadaptedtoestimateNH3emissionsfromcompostingofsolidmanure.TheNH3emissionfactorof0.05isobtainedfromastudyofcompostingmixtureofcattleandswinemanure(HellebrandandKalk,2000).Equation5‐C‐10providestheequationsforestimatingNH3emissions.
5‐C.5 UncertaintyinAmmoniaEmissionsEstimates
EstimationmethodsfromRotzetal.(2011b)areusedtoestimateNH3emissionsfromtemporarystackandlong‐termstockpilesandaerobiclagoons.Rotzetal.takesintoaccounttheamountofemissivesurfaceareaofthepileorlagoon.Giventhedifficultyofmeasuringthesurfaceareaofamanurepile,shapefactorshavebeendevelopedtoapproximatesurfaceareabasedongeneralshapeandfootprint.Theseshapefactorsprovideanestimatetotalsurfaceareaonly;thereisassociateduncertaintybasedontheaccurracyofthefootprintmeasurementsandhowwelltheshapeofthepilematchestheshapefactorsdefined.
TheRotzetal.equationsrequiretheNH3concentrationintheambientaironsite.NationaldataonambientNH3concentrationsareavailablefromtheNationalAtmosphericDepositionProgram.The
Equation5‐C‐10:IPCCTier2ApproachforCalculatingNH3 EmissionsfromCompostingofSolidManure
Where:
ENH3 =NH3emissionsperday(kgNH3day‐1)
m =Totaldrymanure(kgday‐1)
EFNH3 =NH3emission(loss)relativetototalnitrogeninmanure(kgNH3‐N(kgTN)‐1;=0.05)
TN =Totalnitrogenintheinitial(fresh)manure(kgTN(kgdrymanure)‐1)
=ConversionofNH3tonitrogen
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ProgramprovidesambientNH3concentrationsfromapproximately60activemonitoringsitesacrossthecountry.Giventhedearthofmonitoringsitesandthepotentiallylongdistancesbetweentheentityandthenearestmeasurement,therecanbealargeamountofuncertaintyassociatedwiththeambientairNH3concentrationsusedforestimatingNH3emissions.
Table5‐C‐5:AvailableUncertaintyDataforAmmoniaEmissionsEstimates
ParameterAbbreviation/Sym
bol
DataInputUnit
EstimatedValue
RelativeuncertaintyLow
(%
)
RelativeuncertaintyHigh
(%)
EffectiveLowerLimit
EffectiveUpperLimit
DataSource
pH pH ‐ 7.5 6.5 8.5 ExpertAssessment
Totalammonianitrogeninthemanure–beefearthenlot
TAN kgNH3/m3 0.1 0 0.02 ASABE(2005)
Totalammonianitrogeninthemanure–poultry,leghornpullets
TAN kgNH3/m3 0.85 0.66 1.04 ASABE(2005)
Totalammonianitrogeninthemanure–poultry,leghornhen
TAN kgNH3/m3 0.88 0.54 1.22 ASABE(2005)
Totalammonianitrogeninthemanure–poultry,broiler
TAN kgNH3/m3 0.75 ASABE(2005)
Ammoniaconcentrationintheliquid–dairylagooneffluent
NH3 kgNH3/m3 0.08 ASABE(2005)
Ammoniaconcentrationintheliquid–dairyslurry(liquid)
NH3 kgNH3/m3 0.14 ASABE(2005)
Ammoniaconcentrationintheliquid–SwineFinisher‐Slurrywet‐dryfeeders
NH3 kgNH3/m3 0.5 ASABE(2005)
Ammoniaconcentrationintheliquid–SwineSlurrystorage‐dryfeeders
NH3 kgNH3/m3 0.34 0.19 0.49 ASABE(2005)
Ammoniaconcentrationintheliquid–Swineflushbuilding
NH3 kgNH3/m3 0.14 ASABE(2005)
Ammoniaconcentrationintheliquid–Swineagitatedsolidsandwater
NH3 kgNH3/m3 0.05 ASABE(2005)
Ammoniaconcentrationintheliquid–SwineLagoonsurfacewater
NH3 kgNH3/m3 0.04 ASABE(2005)
Ammoniaconcentrationintheliquid–SwineLagoonsludge
NH3 kgNH3/m3 0.07 ASABE(2005)
Composting–Ammoniaemission(loss)relativetototalnitrogeninmanure
EFNH3 kgNH3‐N/kgN 0.05 HellebrandandKalk(2000)
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Appendix5‐D:ManureManagementSystemsShapeFactors( )Factorscanbeappliedtoaccountforthedifferencesinemissivesurfaceareasfordifferentshapesofmanurepiles.Theequationsprovidedbelowprovideestimatesforthesurfaceareaforcommonpileshapes;theseestimatesareappliedforcalculatingNH3emissionsfromtemporarystacks.
Figure5‐D‐1:EquationsforCalculatingtheShapeFactorfora2‐SidedStorageBinwithQuarter‐ConePile
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Figure5‐D‐2:EquationsforCalculatingtheShapeFactorfora3‐SidedStorageBin
Figure5‐D‐3:EquationsforCalculatingtheShapeFactorforaConicalManurePile
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Figure5‐D‐4:EquationsforCalculatingtheShapeFactorforaFree‐Standing,TruncatedConicalStack
Figure5‐D‐5:EquationsforCalculatingtheShapeFactorforaWindrowwithTriangularCrossSection
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Appendix5‐E:ModelReview:ReviewofEntericFermentationModelsAnumberofempiricalandmechanisticmodelshavebeendevelopedtoestimateentericCH4
production(Table5‐E‐1).TwoofthefactorsthataffectentericCH4productiontothegreatestextentaredietcompositionandlevelofintake.PredictionequationsandmodelsconstructedtopredictentericCH4aregenerallybasedonthesefactors.MoststatisticalequationsdevelopedtoestimateentericCH4emissionshavebeendevelopedusingdatasetsofanimalsfedhigh‐foragedietsormixeddiets;fewstudieshavefedhigh‐concentratedietstypicaloftoday’sU.S.feedlots.
Table5‐E‐1:ModelsPotentiallyUsefulinEstimatingEntericCH4EmissionsfromTypicalU.S.RuminantAnimals
Reference Variablemodeled Inputs/CommentsEmpiricalModels
IPCC(2006) EntericCH4No.ofanimals,animalspecies,animaltype,emissionfactorforeachanimaltype(Tier2CH4conversionfactor;Ym)
Kriss(1930) EntericCH4 Drymatterintake(DMI)Axelsson(1949) EntericCH4 DMIBratzler&Forbes(1940)
EntericCH4 Digestedcarbohydrate
Millsetal.(2003) EntericCH4Metabolizableenergy(ME)intake,starchandaciddetergentfiber(ADF)intake
Blaxter&Clapperton(1965)
EntericCH4Digestibleenergy(DE)(%)atmaintenanceintake,grossenergyintake(GEI),feedinglevel(multipleofmaintenance)
Moe&Tyrrell(1979) EntericCH4Digestiblesolublecarbohydrates,digestiblehemicellulose,digestiblecellulose
Holter&Young(1992) EntericCH4Digestiblesolublecarbohydrates,cellulose,hemicellulose,fatintake
Yanetal.(2009) EntericCH4Digestibleenergy,silage,andtotalDMI,silage,anddietADF
Ellisetal.(2007) EntericCH4 Metabolizableenergyintake,ADF,ligninintake
Ellisetal.(2009) EntericCH4Metabolizableenergyintake,cellulose,hemicellulose,andfatintake;non‐fibercarbohydrate,neutraldetergentfiber(NDF),andDMI
Millsetal.(2001) EntericCH4 DMIHolos(Littleetal.,2008)
EntericCH4,manureCH4
BasedonIPCC(2006)
CNCPS(2010)
EntericCH4,DMI,nutrientexcretion,urinenitrogenexcretion;
UsesequationofMillsetal.(2003)fordairyandEllisetal.(2007)forbeef.Animalcharacteristics,dietnutrientcomposition,feedproteinfractions,animalperformance,animalmanagement,insitudegradabilityoffeeds
IntegratedFarmSystemModel(Rotzetal.,2011b)
EntericCH4,nutrientexcretion,urinenitrogen,DMI,manureNH3,CH4,andN2O
UsestheMits3equationofMillsetal.(2003)forentericCH4,IPCC(2006)formanureCH4,andeitherDAYCENT(Chianeseetal.,2009d)orIPCC(2006)formanureN2O
Phetteplaceetal.(2001)
EntericCH4,manureCH4
Animalclass,animalageandbodyweight,quantityofmeat/mileproduced,feedtype,feedintake,manuremanagement
Process‐basedModels
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Reference Variablemodeled Inputs/Comments
Kebreabetal.,(2004;2009)
EntericCH4,nutrientexcretion
DMI,NDF,degradableNDF,totalstarch,degradablestarch,solublesugarsindiet,dietnitrogen,NHx‐Nindiet,indigestibleprotein,rateofdegradationofstarch,andprotein
COWPOLL(Dijkstraetal.,1992;Millsetal.,2003;Banninketal.,2006;Kebreabetal.,2008)
EntericCH4
DMI,NDF,degradableNDF,totalstarch,degradablestarch,solublesugarsindiet,dietnitrogen,NHx‐Nindiet,indigestibleprotein,rateofdegradationofstarch,andprotein
MOLLY(Baldwin,1995)
EntericCH4 SimilartoCOWPOLL
Predictionmodelsforentericemissions.Thefollowingisabriefsummaryofthemodelsevaluatedandtheirstrengthsandlimitations.
SimpleRegressionModelBasedonDigestibleEnergy.BlaxterandClapperton(1965)developedasimpleregressionequationtoestimateentericCH4basedondigestibleenergy,feedintakeasapercentageofmaintenanceandGEI.Thedatasetusedtocreatethisempiricalmodelwascomposedmostlyofdatafromsheepfedlow‐concentratedietsinrespirationchambers,whichmayaccountforitslimitedaccuracyinpredictingCH4emissionsacrossruminantdiets(Johnsonetal.,1991).
EmpiricalModel.MoeandTyrrell(1979)developedanempiricalmodeltoestimateentericCH4emissionfromdairycowsbasedondietcomposition.Thisempiricalmodelwasdevelopedwithhigh‐foragedietsindairycowsfedinrespirationchambers;itsuseforestimatingbeefcattleentericemissionsisthereforelimited.
RegressionModel.Yanetal.(2000)developedregressionequationstopredictentericCH4emissionsfrombeefanddairycattlefeddietsbasedongrasssilage.Concentratesrepresentedfrom0to81.5percentoftheDMI,withameanof46.7percentofdietDMI.Whencorrectedtoequalfeedintakes,animalbodyweighthadnoeffectonentericCH4emissions.(Yanetal.,2000)validatedtheirequationsusingdatafromtheliterature,mostlydairystudieswithalldietsbasedongrasssilage.
RegressionEquations.Ellisetal.(2009)developedregressionequationstoestimateentericCH4productionfrombeefcattlebasedonstudiesinwhichcattlewerefedhigh‐concentrateormoderate‐concentrate(50percent)diets.Theseequationswerecomparedwith14equationsdevelopedearlierbyEllisetal.(2007),sevendevelopedbyMillsetal.(2003),theBlaxterandClapperton(1965)equation,andtheMoeandTyrrell(1979)equation.ThemeanentericCH4production(MJday‐1andpercentofGEI)inall12ofthestudieswasgreaterthanvaluesnotedmorerecently(Halesetal.,2012),possiblybecauseofdifferencesindietarygraincontentandfatsupplementation.However,someoftheEllis(2007;2009)equationsestimatedCH4emissionssimilartothosereportedbyToddetal.(2014a;2014b)inopenlotfeedlots.
Thelinearmodelwiththelowestresidualmeansquarepredictionerror(RMSPE)wasEquation5‐E‐1asfollows:
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Apossibleadvantagetousingthisequation,comparedwithotherempiricalequations,isthatthevariablesrequiredforthecalculationscanbereadilyobtainedwithsometraininginnutrition.Anotheristhattheindependentvariablesinthemodel(energy,fiber,andfatintake)aretheprimarydifferencesthatwouldoccurinvariousbeefanddairycattlediets.However,amajorconcernwiththeiruseforfinishingcattleisthatanumberofthestudiesusedtodeveloptheequationswerehigh‐foragedietsand/ordidnotuseeithersupplementalfatormonensininthediet.Aspreviouslynoted,whencomparedwithemissionsfromcattlefedtypicalfinishingdietsbasedonsteam‐flakedcorn(SFC)ordry‐rolledcorn(DRC),thisequationgreatlyoverestimatedCH4emissions(Halesetal.,2012).Linearequationsusingnutrientratios(starch:NDF,etc.)werealsodeveloped,butallhadgreaterRMSPEthanthepreviousequation(Ellisetal.,2009).Nonlinearequationswerealsodeveloped.Despitebeingmorebiologicallydefendable,thenonlinearequationsallhadgreaterRMSPEthanthelinearequation.
Inalaterstudy,Yanetal.(2009)developedadditionalequationsusingadatabaseof108measurementsforbeefsteersofvariedbreedinginrespirationchambersandfeddietsthatrangedfrom100to30percentroughage.Theyalsocomparedanumberofequationsdevelopedelsewhere.Equationswere“validated”usingone‐thirdoftheoriginaldataset.Emissionswerehighlycorrelatedtolivebodyweight,DMI,andGEI,butlivebodyweightwasapoorpredictorofentericCH4emissions.TheabilityofanumberofequationstopredictentericCH4measuredinthestudywasvaried(eightpercentoverpredicted,to33percentunderpredicted).ThepoorestresultswerewithfourlinearequationsdevelopedbyEllisetal.(2007)thatusedDMI,MEI,and/orforageintakeasindependentvariables.TheyattributedthepoorresponsetothefactthatagoodportionofthedataforEllisetal.(2007)wasfromgrazinganimalsusingtheSF6technique,whichwouldnotincludeCH4fromthelowergut.TheBlaxterandClapperton(1965)equationdidarespectablejob(93percentofactualwithR2=0.69;meanpredictionerror=0.12;and63percentofmeanssquarepredictionerrorduetorandomeffects,and29percentduetoameanbias).
EmpiricalandMechanisticModel.TheIFSMModel(anditssubsetDairyGEM)(Rotzetal.,2005;Chianeseetal.,2009b;2009c;2009a;2009d)isacombinationempiricalandmechanisticmodelofwholefarmnutrientmanagement.ThesubmodeltoestimateentericCH4emissionsfrombeefordairycattleusestheMits3equationofMillsetal.(2003).Ellisetal.(2007)reportedthattheMillsetal.(2003)equationswerepooratpredictingCH4frombeefcattle,probablybecausetheyweredevelopedfromdairydata.Infact,oneequationthatworkedwellwithdairycowsactuallypredictednegativeCH4emissionsfrombeefcattlefedhigh‐concentrate,low‐foragediets.Thus,thecurrentIFSMmaynotbeappropriatetoestimateentericCH4emissionsfrombeefcattle,especiallyfeedlotcattle.
MechanisticModels.MOLLY(Baldwinetal.,1987;Baldwin,1995)isamechanisticmodelthatestimatesruminalCH4productionbasedonahydrogenbalancewithintherumen.Input
Equation5‐E‐1:LinearModelwiththeLowestRMSPE
. . . . .
Where:
CH4 =Methaneperday(MJday‐1)
MEintake=MEintakein(MJday‐1)
CELL =Celluloseintake(kgday‐1)
HC =Hemicelluloseintake(kgday‐1)
Fat =Fatintake(kgday‐1)
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parameterstothemodelaredailyDMI,chemicalcompositionofthediet,solubilityofproteinandstarch,degradability,ruminalpassagerates,ruminalvolume,andruminalpH.COWPOLL(Dijkstraetal.,1992;Millsetal.,2001)isanothermechanisticmodel.InputparameterstothemodelaresimilartoMOLLY.MOLLYandCOWPOLLbothuseanH‐balancetoestimateentericCH4production.However,theyusedifferentVFAstoichiometrysubmodels.Bothmodelsrequiresignificantinputsthatareprobablybeyondthescopeoftypicalproducers.However,theyareexcellentresearchtools.
TheCornellNetCarbohydrateandProteinSystemmodel(CNCPS,2010)calculatesnutrientrequirements,nutrientinputs,animalproduction(weightgainand/ormilkproduction),andnutrientexcretioninbeefanddairycattle.Itrecentlyaddedasubmodel(VanAmburghetal.,2010)tocalculateentericCH4emissions.ThesubmodelusesanequationofMillsetal.(2003)toestimateentericemissionsfromdairycowsandanequationofEllisetal.(2007)toestimateentericemissionsfrombeefcattle.Atpresent,toourknowledgetherearenocomparisonsorindependentvalidationsofthenewsubmodelsthathavebeenpublished,andtheextenttowhichthemodelisresponsivetomitigationstrategiesisunclear.
ComparativeAnalysesusingIndependentDataSets.SeveralstudieshaveattemptedtoevaluatethepredictiveabilityofentericCH4modelsbyusinganindependentdataset.Benchaaretal.(1998)comparedtwomechanistic(Baldwinetal.,1987;Dijkstraetal.,1992;Baldwin,1995);andtwolinear(BlaxterandClapperton,1965;MoeandTyrrell,1979)modelswithadatasetof32dietsfrom13publicationsintheliterature.Theynotedthatthemechanisticmodelswerebetterpredictorsthantheregressionequations.Thelinearregressionmodelscouldonlyexplain42to57percentofthevariationinpredictedvalues,whereasthemechanisticmodelsexplainedmorethan70percentofthevariation.ThemodelofDijkstraetal.(1992)tendedtounderestimateactualCH4
production(meanerror=0.30Mcalday‐1),withtheerrorbeinggreaterathigherCH4productions.ThemodelofBaldwin(Baldwinetal.,1987;Baldwin,1995)overestimatedCH4productionbyabout0.93Mcalday‐1,primarilyduetoahighintercept.TheequationsofMoeandTyrrell(1979)andBlaxterandClapperton(1965)tendedtooverestimateCH4production,especiallyatlowproductionrates.
ComparativeAnalysis/LactatingandNonlactatingCows.Wilkersonetal.(1995)comparedseveralpublishedequations(Kriss,1930;BratzlerandForbes,1940;Axelsson,1949;BlaxterandClapperton,1965;MoeandTyrrell,1979;HolterandYoung,1992)fortheirabilitytopredictentericCH4productionfromlactatingandnonlactatingHolsteincows.Ingeneral,equationsthatwerebasedontotalDMIoronintakeofdigestedcellulose,hemicellulose,andnonfibercarbohydrates,providedthehighestcorrelationandlowesterrorsofprediction.PredictionequationsthatusedaquadraticfunctionofDMIwerepooratpredictingentericCH4.Ingeneral,theequationspredictedemissionsfromnonlactatingcowsmoreaccuratelythanfromlactatingcows.
ComparativeAnalysisLinearModels.Kebreabetal.(2006)comparedtwolinearmodels(MoeandTyrrell,1979;Millsetal.,2003),anonlinearmodel(Millsetal.,2003),theIPCCTier1andTier2models(IPCC,1997),andadynamicmechanisticmodel(Kebreabetal.,2004)usingdatafromstudiesconductedinNorthAmerica.Theyrecommendedthatthelinearmodelsbeusedwhenthereislimitedinformationonnutrientintakeandwhentheexpectedemissionsarewithintherangeofdatafromwhichthemodelwasdeveloped.ThenonlinearmodelofMillsetal.(2003)couldbeusedforextrapolatingbeyondtherangeofdatausedtodeveloptheequation,butthemechanisticmodelwasrecommendedforevaluationofmitigationoptions.TheIPCCTier1modelwasfoundtobeadequateforgeneralinventorypurposes.ThepredictiveabilityoftheTier2model,whilemostuseful,waslimited.
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ComparativeAnalysisMechanisticModels.Kebreabetal.(2008)alsocomparedtwomechanisticmodels,MOLLY(Baldwinetal.,1987;Baldwin,1995)andCOWPOLL(Dijkstraetal.,1992;Millsetal.,2001;Banninketal.,2006),totheIPCCTier2(2006)andlinearequationofMoeandTyrrell(1979).Usingabeefcattledataset,MOLLYandIPCCtendedtobemoreaccuratethantheothermodels,althoughMOLLYwasmoreprecise.MOLLYandIPCCTier2hadminimalmeanbias,whereasCOWPOLLandtheMoeandTyrrell(1979)equationgreatlyoverpredictedaverageemissions.COWPOLL,whichisbasedontheentericCH4predictionequationsofMillsetal.(2001)andtheupdatedrumenstoichiometryforlactatingcows(Banninketal.,2006),hadthepoorestabilitytopredictentericCH4emissionfromfeedlotcattleandtendedtooverpredictCH4emissions(MJday‐1)byasmuchas50percent.AlthoughonaverageMOLLYandIPCCTier2(2006)gavepredictedvaluessimilartomeasuredvalues,therewasalargevariabilityinindividualanimals,witherrorsof75percentorgreater.Thelargevariabilityinpredictedvaluesindicatesthattherecanbelargeanimal‐to‐animalvariationinentericCH4production,evenwhenanimalsarefedthesamedietsatsimilarfeedintakes.
ComparativeAnalysis/Feedlots.McGinnetal.(2008)comparedmeasured(usingbLSmodel)CH4emissions(entericpluspensurface)fromfeedlotsinAustraliaandCanadawithestimatesusingtheIPCCTier1,IPCCTier2,BlaxterandClapperton(1965),andMoeandTyrrell(1979)equations.TheTier2methodunderestimatedCH4atbothlocations.EstimatesusingtheIPCCTier1methodswereclosetomeasuredvaluesinAustralia;however,Tier1underestimatedvaluesfortheCanadafeedlot.EstimatesmadeusingtheBlaxterandClapperton(1965)andMoeandTyrrell(1979)equationswereclosetomeasuredvaluesinCanada,butoverestimatedvaluesinAustralia.Methaneemissionshadasignificantdielpatternindicatingthatshort‐termmeasurementofCH4emissionsatfeedlotsmayoverestimateorunderestimatedailyemissions.
ComparativeAnalysisofStoichiometricModels.Alemuetal.(2011)comparedentericCH4emissionsfromdairycowsusingavarietyofstoichiometricmodelsofruminalfermentation(Murphyetal.,1982;Banninketal.,2006;Sveinbjornssonetal.,2006;Nozièreetal.,2010),andnotedthatmechanisticmodelssuchasBanninketal.(2006)aremoreaccurateforpredictingentericCH4fromdairycowsthantheIPCCTier2(2006)method.However,thesemodelsrequiredaconsiderablequantityofdataregardingtheanimalsandtheirdiet.
ComparativeAnalysisMeasurementDataandModels.Tomkinsetal.(2011)measuredentericCH4emissionsofsteersonpastureusingamicrometeorologicalmethodandrespirationchambers.EmissionsestimatedusinganEllis(2009)equation(CH4,MJday‐1=3.272+0.736(DMI,kgday‐1))weresimilar(112.7gday‐1)tomeasuredemissions.EstimatesusingtheequationsofKuriharaetal.(1999)asmodifiedbyHunter(2007)(109.1gday‐1),Yanetal.(2009)(105.6gday‐1),andCharmleyetal.(2008)(2008:NABCEMS;100.2gday‐1)wereslightlylower,butnotaslowastheIPCC(2006)model(82.7gday‐1).
ComparativeAnalyses/Models.Legesseetal.(2011)comparedentericCH4emissionestimatesusingMOLLY,COWPOLL,IPCCTier2,andoneequationofEllisetal.(2007)undervariousCanadianbeefcow‐calfmanagementsystems.Differencesamongthemodels(26to35percent)weremuchgreaterthandifferencesamongmanagementsystems(threetofivepercent).Theauthorssuggestedthatthesedifferenceslimitedthemodel’sutilityinpredictingCH4emissionfrombeefcowsystems.
EvaluationofModels.Yanetal.(2000;2009)notedthatCH4production(percentofGEIordigestibleenergy)decreasedwithincreasingDMI(asmultiplesofmaintenance)andwithincreasingforageinthediet.Thus,theysuggestedthatmodelsthatdonotconsiderfeedinglevelwillunderpredictCH4atlowplanesofnutritionandoverpredictentericCH4athighlevelsoffeeding.Similarly,Kebreabetal.(2006)notedthatlinearmodelstendtogiveunrealisticallyhigh
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emissionvalueswhenDMIincreases,whereasnonlinearmodelsgavevaluesapproachingthetheoreticalmaximumemission,whichisbiologicallyreasonable.
AlthoughseveralequationsofEllisetal.(2009)appearedtobegoodpredictorsofentericCH4lossesfromfeedlotcattlebasedonCanadianstudies,whencomparedwithdatafromcattlefedatypicalcorn‐basedfinishingdiet(Halesetal.,2012)mosttendedtogreatlyoverestimateentericlosses.Atthepresenttime,theIPCCTier2modelwithsomemodificationsmaybethemostusefulforpredictionofentericemissionsfromfeedlotbeefcattle.
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