Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
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Rilis augiati siscilit venis nim
M e t h o d o l o g i e s & W o r k i n g p a p e r s
ISSN 1681-4789
ISSN 1977-0375
2011 edition
M e t h o d o l o g i e s a n d W o r k i n g p a p e r s
Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
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and nutrient balances
Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances This document is the result
of the DireDate project's task 3. DireDate stands for 'Direct and
indirect data needs linked to the farms for agri-environmental
indicators'. The DireDate project is a study financed by Eurostat,
European Commission, and undertaken by a consortium led by ALTERRA
(NL) (Service Contract 40701.2009.001-2009.354). The general
objective of DireDate is “to create a framework for setting up a
sustainable system for collecting a set of data from farmers and
other sources that will serve primarily European and national
statisticians for creating the agreed 28 agri-environmental
indicators (AEIs) and thus serve policy makers, but as well
agricultural and environmental researchers, observers of climate
change and other environmental issues linked to agriculture”.
Authors and affiliation
Barbara Amon, Nicholas Hutchings Stefan Pietrzak Finn P. Vinther
Per K. Nielsen Hanne D. Poulsen Ib S. Kristensen
Department of Sustainable Department of Agro-ecology Institute for
Land Reclamation Agricultural Systems, and Environment and
Grassland Farming University of Natural Resources University of
Aarhus IMUZ and Applied Life Sciences, Denmark Falenty, Poland
Wien, Austria
Editors
Johan Selenius, Ludivine Baudouin, Anne Miek Kremer -
Eurostat
The views expressed in this document are those of the authors and
do not necessarily reflect the views of the European Commission
and/or of the institutions or countries in which authors work.
Neither the European Commission nor authors are responsible for the
use that may be made of the information contained in this
document.
4Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
Table of Contents
1.2 Nitrogen and phosphorus
balances...........................................................................
8
1.4 Conclusions and Recommendations
.......................................................................
12 1.4.1
Methodologies.............................................................................................
12 1.4.2 Importance of
coefficients...........................................................................
12 1.4.3 Detailed procedures needed for emission abatement
strategies ............... 12 1.4.4 Data collection
............................................................................................
13
2 Introduction
...........................................................................................................................
14
3 Data requirements in relation to emissions of greenhouse gases
and ammonia................. 15
3.1
Aim...........................................................................................................................
15
4 Analysis of data necessary to estimate emissions of greenhouse
gases and CLTRP compounds from manure
management................................................................................
18
4.1 Basic
Data................................................................................................................
18
4.3 CH4 emissions from manure
management..............................................................
20
4.4 N2O from manure
management...............................................................................
22
4.6 NH3 emissions from manure
management..............................................................
23
4.7 Data requirements to estimate NH3 and GHG
emissions........................................ 24 4.7.1 Data
requirements
......................................................................................
24 4.7.2 Data collection
............................................................................................
27
5 Data necessary for the calculation of N and P balances
...................................................... 31
5Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
5.1 General
....................................................................................................................
31
5.3 Data requirements for N and P balances
................................................................ 38
5.3.1 Farm nitrogen
balance................................................................................
38 5.3.2 Soil nitrogen balances
................................................................................
40 5.3.3 Phosphate balances
...................................................................................
41
6 Coefficients related to emissions of GHG, ammonia and N
balances.................................. 45
6.1 Gaseous emission coefficients
................................................................................
45
6.2 Nitrogen
excretion....................................................................................................
45 6.2.1 Estimating nitrogen retained in animal
products......................................... 46 6.2.2
Estimating nitrogen consumed in feed
....................................................... 46 6.2.3
Calculating nitrogen excretion
....................................................................
47
7 Sampling strategy
.................................................................................................................
50
7.1 Disaggregation of emissions of GHG and NH3, and of N balances
........................ 50
7.2 Stratified sampling strategy
.....................................................................................
50
8 Conclusions and
recommendations......................................................................................
52
References
..................................................................................................................................
53
6Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
1 Summary
Agriculture has relatively large shares in the total emissions of
ammonia (NH3) and the greenhouse gases methane (CH4) and nitrous
oxide (N2O) into the atmosphere. These gases have also relatively
large ecological impacts, including (e.g. Sutton et al.,
2011):
• A decline in human health, due to NH3 induced formation of
particle matter (PM2.5) and smog;
• Plant damage through high NH3 concentrations in air;
• A decrease in species diversity of natural areas due to N
enrichment through atmospheric deposition of NH3;
• Acidification of soils because of deposition of NH3;
• Global warming because of emission of CH4 and N2O; and
• Stratospheric ozone destruction due to N2O
Nitrogen (N) and phosphorus (P) are the main crop growth limiting
nutrients in agriculture. Losses of N and P into the wider
environment have major ecological impact, including the
abovementioned impacts, and
• Pollution of ground water and drinking water due to nitrate
leaching;
• Eutrophication of surface waters due to N P enrichment, leading
to excess and possibly toxic algal blooms and a decrease in faunal
and floristic species diversity.
Moreover, the production of N fertilizers is energy-intensive and
accompanied by large CO2 emissions. Phosphorus fertilizers are
produced from scarce rock phosphate resources, which will be
depleted within decades unless appropriate measures are taken.
Hence, N and P balances are key agri-environmental
indicators.
There are various diffuse sources of NH3, CH4 and N2O in
agriculture. Estimating these sources accurately is not without
difficulty. Also, N and P balances of agricultural systems are not
easy to assess. Because of the importance and complexities involved
in the accounting of ammonia and greenhouse gas emissions, and of N
and P balances of agricultural systems, a special task (Task 3) of
DireDate related to analysing the methodologies for calculating
NH3, CH4, N2O emissions and N and P balances. Particular emphasis
was given to the coefficients used in the calculations and the
underlying data needs, and to identify best practices for these
calculations, based on available scientific research.
The purpose of this Report is to briefly summarize the results of
Task 3 of the DireDate Project. The objective of Task 3 is:
• To analyze the methodologies for calculating greenhouse gas and
ammonia emission and nutrient balances (nitrogen and phosphorus),
with particular stress on the coefficients used in the calculations
and the underlying data needs, and
• To identify best practices for these coefficient calculations,
based on available scientific research.
1 Summary
7Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
1.1 Greenhouse gas and ammonia emissions
Greenhouse gas emissions from agriculture occur from a number of
sources. Dominant sources of methane (CH4) are enteric
fermentation, manure management and wetlands, including paddy rice
fields (Figure 1). Direct sources of nitrous oxide (N2O) are manure
management and agricultural soils. Indirect sources of N2O are the
emission of ammonia (NH3) and the leaching of nitrate (NO3) from
agriculture (Figure 1).
Figure S1: Schematic representations of the main sources of NH3,
CH4, and N2O emissions in agricultural systems
Emissions of greenhouse gases are within the scope of the UN
Framework Convention on Climate Change (UNFCCC) whereas those of
ammonia are within the scope of the UN Convention on Long- Range
Transboundary Air Pollution (CLTRP). Guidance on the methodologies
for calculating greenhouse gas and ammonia emissions is provided in
the IPCC Guidelines (‘the Guidelines’) and the EMEP/EEA Air
Pollution Emission Inventory Guidebook (‘the Guidebook’)
respectively. The trend seen within both UNFCCC and CLRTP is for
emission limits to be progressively reduced over time. For both
greenhouse gas and ammonia emissions, agriculture represents a
major source. When faced with the need to reduce emissions,
countries are usually faced with a choice between a number of
different abatement measures. The implementation of abatement
measures will often result in an increased cost to agriculture and
to the environmental authority that must monitor compliance.
Identifying the most cost-effective abatement measures for
agriculture requires a range of activity data to be
collected.
Emissions are estimated by multiplying activity data with emission
factors. Compiling the national inventory therefore comprises two
main steps: (i) obtaining national activity data and (ii) choosing
emission factors (either default or country specific emission
factors).
Agricultural emissions strongly depend on the animal housing, and
on the manure management system (MMS) distribution. These data are
a mandatory pre-requisite for accurate emission estimates, with a
low range of uncertainty. The impact of mitigation measures on the
national emissions reported under UNFCCC and CLRTP must be
documented and this is only possible if representative data on the
MMS distribution are available. A lack of these data leads to two
major disadvantages:
1 Summary
8Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
1. Country-specific values can only to a small extent be integrated
in the national emission inventory. Major parts of the inventory
must be set up with default values that misrepresent the processes
typically found in the respective country.
2. Due to the lack of activity data, the effect of mitigation
measures cannot be included in the national emission
inventory.
1.2 Nitrogen and phosphorus balances
The gross nitrogen and phosphorus balances provide holistic
indicators of the related environmental pressure exerted by
agriculture. For N, significant losses occur to the atmosphere in
the form of ammonia, nitrous oxide, nitric oxide (NO) and
dinitrogen (N2). Ammonia, nitrous oxide and nitric oxide are
pollutants, whereas the emission of dinitrogen reduces the
effectiveness of manure and fertilisers and the fertility of soils.
Nitrogen is lost to aquatic environments in the form of nitrate,
ammonium and dissolved organic N, all of which can lead to
pollution and all of which reduce the fertility of the soil. The
nitrogen flows and losses in agricultural systems are schematically
shown in Figure 2.
Unlike greenhouse gas and ammonia emissions, countries are not
required to report N and P balances for agriculture as part of any
international conventions. As a consequence, there is no
organisation equivalent to the IPCC or UNECE who has responsibility
for standardising and improving the methodology to calculate such
balances. However, OECD has established a de facto standard for
gross N balances, and the soil N balance calculated by the CAPRI
model has gained acceptance in European policymaking. Furthermore,
the Task Force on Reactive Nitrogen (TFRN), established under
CLRTP, is currently establishing national N balances that include
agriculture. As an organisation established within an international
convention and dedicated specifically to N, we consider that that
in the long term, the TFRN is the appropriate organisation to
standardize and improve the methodology related to N balances. We
note, however, that while the scientific community is strongly
represented in the TFRN, the number of statisticians is low. We
would therefore encourage representatives of national statistical
bureau to become more involved in the work of this
organisation.
Figure S2: Schematic representations of the main nitrogen flows and
losses in agricultural systems.
1 Summary
9Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
1.3 Data needs and data collection
The data needs for calculating NH3, CH4, N2O emissions and N and P
balances are relatively large, especially for large emissions
sources, because of the required accuracy for estimates of large
sources. Currently, these data are not always available in Member
States.
Based on experiences in various countries, it is suggested that
farm structure surveys should be carried out every five years for
collecting information about housing systems, manure storage
systems and manure application techniques. Table 1 presents the
list of data that should be collected. Table 1 distinguishes the
following main NH3, CH4 and N2O emissions sources:
1. housing (cattle, pigs, and poultry),
2. water management,
4. slurry and farmyard manure application techniques, and
5. the diets of the animals.
Table 1 qualifies data requirements into “optimum” and “minimum”
data collection requirements. Activity data listed under “minimum
requirement” must be collected, because without these data, a
proper inventory reporting is not possible. The effect of
mitigation measures cannot be shown in the inventory and the cost
effectiveness of mitigation measures cannot be assessed. Activity
data listed under “optimum requirement” should be collected for
more accurately estimating inventories. They offer more
possibilities for country-specific and cost-effective mitigation
measures and enable the assessment of environmental impacts of farm
management practices. For most of these data, the additional effort
for collecting them is small and the additional effect is
large.
1 Summary
10Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
Table S1: Data to be collected through surveys at farm level
Activity data collection Reasoning Housing cattle - minimum
requirement
Liquid / solid system Tied / loose housing
EF* differ between both systems, system has great influence on
subsequent losses
Grazing Necessary for estimation a consistent N flow, necessary for
NH3 and N2O emission estimates, IPCC requires data on grazing
Housing cattle – optimum requirement Subcategory of housing systems
prevalent in the country Floor system Yard
Considerable differences in emissions; easy to answer for the
farmer; necessary for the assessment of mitigation measures
Housing pigs - minimum requirement
Liquid / solid system EF differ between both systems, system has
great influence on subsequent losses
Housing pigs – optimum requirement Subcategory of housing systems
prevalent in the country Floor system Yard Air scrubber
Considerable differences in emissions; easy to answer for the
farmer; necessary for the assessment of mitigation measures
Housing poultry - minimum requirement Housing system Manure
treatment
Considerable differences in EF; easy to answer for the farmer
Housing poultry - optimum requirement Drinkers
Frequency of manure removal from the house
Considerable differences in emissions; easy to answer for the
farmer; necessary for the assessment of mitigation measures
Water management – optimum requirement Cleaning of the house, water
addition to slurry Diluted slurry emits less NH3
Slurry storage - minimum requirement
Slurry store cover Great influence on NH3 emissions; cost effective
mitigation measure; likely to become mandatory in the future
Slurry storage - optimum requirement Store size
Slurry treatment
Slurry storage during warm and cold season
Considerable differences in emissions; Easy to answer for the
farmer; necessary for the assessment of mitigation measures
FYM storage - optimum requirement Size of the store and duration of
storage FYM treatment Direct FYM application Duration of FYM
storage Cover of FYM stores
Considerable differences in emissions; easy to answer for the
farmer; necessary for the assessment of mitigation measures
1 Summary
11Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
Activity data collection Reasoning Slurry application - minimum
requirement
Application technology
NH3 emissions after slurry application are by far the largest
contributors to total NH3 emissions. Emissions can be effectively
abated by low emission application techniques. Some countries give
subsidies for low emission application techniques. Environmental
effect of these subsidies does not show up if activity data are
unavailable.
Application to grassland or arable land Differences in EF
Slurry application – optimum requirement Timing and amount of
application
Incorporation after application
Considerable differences in emissions; easy to answer for the
farmer; necessary for the assessment of mitigation measures; esp.
timing and amount of application are low cost or even no cost
mitigation measures. They will only show up in the inventory if
activity data are available.
FYM application - minimum requirement Application to grassland or
arable land Differences in EF
Incorporation after application Drastically reduces NH3 emissions;
only measure available to reduce NH3 emissions after FYM
application.
Animal diet – optimum requirement
Components of cattle diet
Important influence on N excretion and CH4 emissions from enteric
fermentation; information will greatly help to improve national
defaults on CH4 emissions from enteric fermentation, N and VS
excretion; all mitigation measures set at the beginning of the
chain will have the largest potential to reduce emissions
Components of pig diet
Important influence on N and VS excretion; information will greatly
help to improve national defaults N and VS excretion; all
mitigation measures set at the beginning of the chain will have the
largest potential to reduce emissions
Phase feeding for pigs
One of the most effective measures to reduce N emissions from pig
manure; measure can be implemented a low or no costs; farmers might
even gain by reducing N content in the pig diets.
Farm-scale data - minimum requirements Number of livestock present,
with major livestock categories identified separately
Required for calculating NH3 and N2O emissions and for calculating
or checking N and P balances
Import of N fertiliser Required for calculating NH3 emission and N
balances Import of protein supplements Import of energy supplements
Export of protein-rich cereals Export of other cereals
Required for calculating or checking N and P balances
Farm-scale data -optimum requirements Import of animal manure
Import of other organic manure Import of bedding material Export of
animal manure Export of straw
These data enable a more accurate calculation of N and P balances
and are necessary if N and P balances are to be disaggregated below
the national scale.
* Emission Factors
1 Summary
12Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
1.4 Conclusions and Recommendations
1.4.1 Methodologies
The methodologies for calculation of greenhouse gas and ammonia
emissions are enshrined in international law, so are not for
discussion. In nearly all European states, agriculture is defined
as a key source with regards to greenhouse gas and ammonia
emissions. As such, Member States are obliged to use a Tier 2
methodology for inventory reporting. Tier 2 methodologies require
data that are both detailed and respect the relationships between
emission sources. These data can only be collected by sampling at
the farm scale.
The methodologies for calculating N balances are not enshrined in
international law. The OECD/EUROSTAT gross N balance represents the
difference between the inputs and outputs of N to agriculture,
divided by the land area occupied. As such, it is equivalent to a
farm N balance and represents a holistic indicator of the potential
environmental impact. The current methodology requires the
estimation of the input of N by livestock excretion and the output
of N in crop products used by livestock on the same farm, both of
which are difficult to obtain. Since there are no significant
gaseous N emissions from the animals themselves, these inputs and
outputs could be replaced by the N in imported animal feed and the
N exported in animal products, where these can be estimated with
greater accuracy.
The impact of agricultural N on the aquatic environment is likely
to be more closely related to a soil N balance than to a farm N
balance. When calculating a soil N balance, it is recommended to
use the country-specific N excretion values reported under UNFCCC
and the Tier 2 methodology of the EMEP/EEA Air Pollutant Emission
Inventory Guidebook for calculating the gaseous emissions of N in
animal housing and manure storage, and after field application of
manure or fertiliser.
1.4.2 Importance of coefficients
Obtaining accurate values for the coefficients used in calculating
emissions or nutrient balances is essential. The default values
provided in the IPCC Guidelines and the EMEP/EEA Guidebook are
intended to be reasonable estimates for the specified geographic
area. These default values often disguise a wide geographic
variation in actual values, either due to variations in climate or
to regional variations in agricultural practices. In addition, the
default values presented in the various guidance documents
generally relate to situations where no abatement measures have
been implemented. Member States are encouraged to use nationally or
regionally appropriate values of the coefficients. It is good
practice to support the use of these coefficients with empirical
measurements. The consequences of relatively small errors in
coefficients can be significant. It is important that the source of
the coefficients used is documented. Where default values are used,
the source should be indicated.
The value of some coefficients varies with agricultural practice.
For example, the emission of ammonia following field application of
animal manure depends on the manure application method used. The
coefficients may need to be updated periodically to take account of
significant changes in agricultural practices.
1.4.3 Detailed procedures needed for emission abatement
strategies
The trend seen within both UNFCCC and CLRTP is for emission limits
to be progressively reduced over time. For both greenhouse gas and
ammonia emissions, agriculture represents a major source. As
noted
1 Summary
13Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
above, for implementing abatement measures the use of Tier 3
methodologies is generally recommended. The implementation of
abatement measures will often result in an increased cost to
agriculture and environmental authority that must monitor
compliance.
Identifying the most cost-effective abatement measures for
agriculture usually requires data that exceeds that which is
necessary to support a Tier 2 approach for calculating emissions.
This is because the complex and very varied nature of agriculture
results in large differences in the abatement measures that are
available and their associated costs.
1.4.4 Data collection
Agricultural emissions strongly depend on the animal housing, and
on the manure management system distribution. These data are a
mandatory pre-requisite for accurate emission estimates that with a
low range of uncertainty. The impact of mitigation measures on the
national emissions reported under UNFCCC and CLRTP must be
documented and this is only possible if representative data on the
manure management system are available. It is recommended to
collect activity data via surveys at farm level every five
years.
Development of cost-effective mitigation measures relating to
greenhouse gas and ammonia emissions or nitrate leaching require
relational statistics that can only be obtained by a farmer
surveys. Since farm management of nutrients tend to vary
systematically with farm type (cattle, pig etc) and size, such
surveys can be usefully stratified according to farm type and
size.
Some European countries have already collected activity data at
farm level. The data surveys were carried out with great success
and the national inventories could be improved. Country specific
mitigation options and potentials were identified. It was found
that the only way forward towards a more sustainable and
environmentally friendly, yet at the same time economically viable,
agriculture was to gain better knowledge of farm management
practices. Only then can practically feasible, efficient and
economic mitigation measures be proposed and implemented.
2 Introduction
14Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
2 Introduction
Agriculture exerts various effects on the environment. These
effects depend on both the agricultural activities and the
environmental conditions. Agriculture in the European Union (EU) is
highly diverse and also dynamic, as agriculture responds to changes
in markets, technological developments and governmental policy. As
a consequence14, effects of agriculture on the environment are
spatially diverse and change over time.
The Common Agricultural Policy (CAP) and Rural Development and
Environmental Regulations and Directives of the EU have a strong
influence on agriculture and its effects on the environment. The
general objectives of these policies are to making EU agriculture
more productive, competitive and environmental sound, whilst
safeguarding the livelihoods and natural values of rural areas.
Member States of the EU are required to report regularly to the
European Commission on the effectiveness of the aforementioned
policies. Agri-environmental indicators (AEIs) increasingly play a
role in assessing the effectiveness of agri-environmental policy
measures.
At present much data and information is collected by Member States
as input for the agreed 28 agri- environmental indicators (AEIs).
Each AEI consists of one or more parameters/data/coefficients that
together provide the AEI. The AEIs are supposed to reflect the
state or trend of a certain agri- environmental variable. However,
at present agricultural statistics mainly focus on economic and
production issues and less on agri-environmental issues.
Consequently, agricultural statistics are used, or modified
towards, the objectives of the AEIs. The usefulness of this
practice depends on the geo- reference of the data (‘Does the data
reflect spatially explicit activities/trends?’), geo-physical
setting of the farm (‘Does the data reflect differences in farm
strategies?’) and continuity of data collection (‘Is the data
collected in a consistent and systematic monitoring
protocol?’).
The general objective of the service contract ‘DireDate’ is “to
create a framework for setting up a sustainable system for
collecting a set of data from farmers and other sources that will
serve primarily European and national statisticians for creating
the agreed 28 agri-environmental indicators and thus serve policy
makers, but as well agricultural and environmental researchers,
observers of climate change and other environmental issues linked
to agriculture”. DireDate is carried out by a consortium of 5
research institutions from 5 Member States and has 9 different
tasks.
The objective of task 3 is to
To analyze the methodologies for calculating greenhouse gas and
ammonia emission and nutrient balances (nitrogen and phosphorus),
with particular stress on the coefficients used in the calculations
and the underlying data needs, and
To identify best practices for these coefficient calculations,
based on available scientific research.
3 Data requirements in relation to emissions of greenhouse gases
and ammonia
15Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
3 Data requirements in relation to emissions of greenhouse gases
and ammonia
3.1 Aim
• calculate accurate emissions and
• identify cost-effective abatement measures.
3.2 General
Emissions of greenhouse gases are within the scope of the UN
Framework Convention on Climate Change (UNFCCC) whereas those of
ammonia are within the scope of the UN Convention on Long- Range
Transboundary Air Pollution (CLTRP). Guidance on the methodologies
for calculating greenhouse gas and ammonia emissions is provided in
the IPCC Guidelines (‘the Guidelines’) and the EMEP/EEA Air
Pollution Emission Inventory Guidebook (‘the Guidebook’)
respectively.
Following the recent revision of the Guidebook, both the Guidelines
and Guidebook use a Tier approach. In this approach, minor emission
sources may be calculated using the simple Tier 1 methodologies
whereas more important (‘key‘) sources should as a minimum be
calculated using the more detailed Tier 2 methodologies. Reporting
bodies are encouraged to use more detailed methodologies than the
Tier 2 approach (Tier 3) if possible and if this would result in
more accurate reporting.
There is a difference in the definition of Tier 2 and Tier between
the Guidebook and the IPCC Guidelines. The Tier 2 methodology of
the IPCC guidelines has a level of detail that allows to show the
effect of some mitigation options (e.g. shift in manure management
systems, biogas production). Whereas the Guidebook requires a Tier
3 approach if the effect of mitigation measures other than the
reduction of livestock numbers is to be shown.
Although data collection to support Tier 3 methodologies will
usually be more expensive than to support the Tier 2 alternatives,
the overall cost to society may be lower. This is because the
explicit inclusion of abatement measures in the calculation of
emissions nearly always requires the use of a Tier 3 methodology.
For example, using a Tier 2 methodology under the Convention on
Long Range Transboundary Air Pollution, the emissions from
livestock are calculated by multiplying the annual average
population by a default emission factor. If a country to the
conventions chooses to use a Tier 2 methodology for a particular
pollutant, the only abatement measure available is to reduce the
population of livestock.
Alternatively, the country could choose to implement technical
abatement measures that would justify using lower emission factors
than the defaults stipulated in the Tier 2 methodology (i.e. they
would use a Tier 3 methodology). The country might well find that
the combined cost to society of implementing abatement measures and
of increasing data collection to support a Tier 3 methodology is
lower than the cost of reducing livestock numbers.
Tier 3 methodology does not necessarily imply the application of
highly complicated models. A Tier 3
3 Data requirements in relation to emissions of greenhouse gases
and ammonia
16Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
approach is the only possibility to show the reduction of emissions
through country specific abatement technologies. In order to
encourage more environmentally friendly and sustainable ways of
farming, the application of Tier 3 approaches is strongly
recommended. There is no restriction on the form of Tier 3,
provided it can supply estimates that can be demonstrated to be
more accurate than Tier 2. If data are available, emission
calculations may be made for a greater number of livestock
categories than listed under the Tier 2 approach. Mass balance
models developed by the reporting country may be used. A Tier 3
method might also utilize the calculation procedure outlined under
Tier 2, but with the use of country-specific EFs or the inclusion
of abatement measures. The effect of some abatement measures can be
adequately described using a reduction factor i.e. proportional
reduction in emission compared with the unabated situation. Tier 3
methods must be well documented to clearly describe estimation
procedures and will need to be accompanied by supporting
literature.
3.3 Identifying cost-effective abatement measures
The trend seen within both UNFCCC and CLRTP is for emission limits
to be progressively reduced over time. For both greenhouse gas and
ammonia emissions, agriculture represents a major source. As noted
above, for implementing abatement measures the use of Tier 3
methodologies is generally recommended. The implementation of
abatement measures will often result in an increased cost to
agriculture and environmental authority that must monitor
compliance.
When faced with the need to reduce emissions, countries are usually
faced with a choice between a number of different abatement
measures. The main items to be taken into consideration when
assessing the relative costs of different abatement measures are as
follows:
• The capital and maintenance cost to farmers of new equipment or
facilities.
• The cost to farmers of any increased demand for labour.
• The extent to which other costs can be offset (e.g. fertilizer
costs).
• The costs are regulating authority of additional data collection
and reporting requirements.
• Any positive or negative interactions with other policy measures
(e.g. Nitrates Directive, animal welfare legislation).
Identifying the most cost-effective abatement measures for
agriculture usually requires data that exceeds that which is
necessary to support a Tier 2 approach for calculating emissions.
This is because the complex and very varied nature of agriculture
results in large differences in the abatement measures that are
available and their associated costs. This can be illustrated by
three examples related to abating ammonia emissions:
1. Non-ruminant livestock (e.g. pigs) are often housed throughout
the year. For reasons of welfare and productivity, this housing is
usually ventilated using a limited number of fans. Air filtration
units can be attached to the ventilation system to remove ammonia.
In contrast, ruminant livestock are often housed through all part
of the year in open-sided housing, where air filtration is not
feasible.
2. Applying slurry to fields by injecting it into the soil is a
very effective way of reducing ammonia emissions from this source.
However, the technique is not usable on stony soils or on steeply
sloping land.
3. The cost of implementing abatement technology depends strongly
on the size of farm. Economies of scale mean that the cost of
abatement per head of livestock is normally much lower large farms
and small ones.
3 Data requirements in relation to emissions of greenhouse gases
and ammonia
17Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
The complexity of agriculture and the dependence of costs on a
range of interrelated factors means that in order to identify
cost-effective abatement measures, it needs to be possible to
establish relationships between data e.g. livestock type x housing
type x farm size. In addition to assisting in the estimation of
abatement costs, the ability to establish relationships between
data is necessary to enable knock-on effects of abatement measures
to be assessed. For example, applying abatement measures to reduce
losses of nitrogen from animal housing, manure storage and from
field-applied manure, reduces the cost of applying commercial
mineral nitrogen fertiliser.
4 Analysis of data necessary to estimate emissions of greenhouse
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18Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
4 Analysis of data necessary to estimate emissions of greenhouse
gases and CLTRP compounds from manure management
Agricultural activities contribute to emissions of greenhouse gases
and ammonia through a variety of processes. Greenhouse gas and
ammonia emissions from the following agricultural sources have to
be calculated:
1. CH4, N2O, and NH3 emissions from domestic livestock
1a. CH4 emissions from enteric fermentation
1b. CH4 emissions from manure management
1c. N2O emissions from manure management
1d. NH3 emissions from manure management
2. CH4, N2O, and NH3 emissions from agricultural soils (including
indirect N2O emissions)
CH4 and N2O emissions from manure management are calculated
following the IPCC methodology. NH3 emissions are estimated
according to the methodology described in the CORINAIR Emission
Inventory Guidebook.
Emissions are estimated by multiplying activity data with emission
factors. Compiling the national inventory therefore comprises two
main steps:
1. Assessment of national activity data
2. Assessment of emission factors – either default or country
specific emission factors.
4.1 Basic Data
Some basic data are required for most of the emission
estimates.
Livestock population characterisation. Basic livestock population
characterisation is needed for Tier 1 and Tier 2 emission
estimates. It comprises information on livestock species and
categories, annual population, milk production, and climate. It is
of vital importance to use a consistent livestock characterisation
across all categories of animal-related emission sources.
To ensure consistency across animal-related emission sources,
characterisation of livestock sub- categories and assessment of
annual population is described in the IPCC guidelines. Through the
harmonisation between IPCC and CORINAIR guidelines, a consistent
livestock population characterisation between the two guidelines
was achieved. Data on livestock population can be taken from the
national statistics.
4 Analysis of data necessary to estimate emissions of greenhouse
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19Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
Milk Production.: Average annual milk production for dairy cows is
required. Milk production data are necessary for estimating the CH4
emission factor for enteric fermentation. Data can be taken from
the national statistics.
Weight: Default emission factors for methane emissions from enteric
fermentation are based in the assumptions, that the average weight
of a dairy cow in Western Europe is 550 kg (Reference Manual, Table
A-I). If country specific data are available, countries are
encouraged to use them.
Climate: Emission factors are climate dependent. It is thus
necessary to consider the climate under which livestock is managed
in each country. In the IPCC Guidelines, Reference Manual, chapter
4.2.3, three climate regions are defined in terms of annual average
temperature: cool (<15°C), temperate (15°C – 25°C), and warm
(>25°C).
4.2 CH4 emissions from enteric fermentation
A simple Tier 1 method and are more complex Tier 2 method are
available to estimate CH4 emissions from enteric fermentation. In
most cases, the Tier 2 method is applied for emission estimates
from cattle (dairy and non-dairy). CH4 emissions from enteric
fermentation of the other livestock categories are mostly
calculated with the Tier 1 method as they are of less importance
for the whole budget.
The IPCC guidelines propose the following formula to estimate CH4
emissions from enteric fermentation:
Emissions [kg yr-1] = (Intake [MJ day-1] * Ym * 365 [days yr-1]) /
55.65 [MJ (kg of CH4)-1]
where:
Ym = methane conversion rate
The feed intake estimates are used in the Tier 2 enteric
fermentation emissions estimate, and in the estimates of CH4 and
N2O emissions from manure management and direct and indirect N2O
emissions.
Feed Intake Estimate: The feed intake of a representative animal in
each sub-category is estimated to support the Tier 2 emissions
estimates. To support the enteric fermentation Tier 2 method,
detailed data requirements and equations are included in the IPCC
Guidelines to estimate feed intake. The IPCC guidelines propose the
following formula for the calculation of gross energy intake of
cattle and sheep:
GE = [(NEm + NEmob. + NEa + NEl + NEw + NEp)/(NEma/DE)] +
[(NEg + NEwool ) / (NEga/DE)]} / (DE/100)
4 Analysis of data necessary to estimate emissions of greenhouse
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20Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
Where:
GE = gross energy intake [MJ day-1]
NEm = net energy required by the animal for maintenance [MJ
day-1]
NEmob. = net energy due to weight loss (mobilised) [MJ day-1]
NEa = net energy for animal activity [MJ day-1]
NE = net energy for lactation [MJ day-1]
NEw = net energy for work [MJ day-1]
NEp = net energy required for pregnancy [MJ day-1]
NEma/DE= ratio of net energy available in a diet for maintenance to
digestible energy consumed
NEg = net energy needed for growth [MJ day-1]
NEwool = net energy required to produce a year of wool [MJ
day-1]
NEga/DE= ratio of net energy available for growth in a diet to
digestible energy consumed
DE = digestible energy expressed as a percentage of gross
energy
Due to a lack in data availability it is not always possible to
estimate gross energy intake following the formula proposed in the
IPCC guidelines. In the "IPCC Good Practice Guidance and
Uncertainty Management in National Greenhouse Gas Inventories
(GPG)1" it is stated that “for inventory agencies that have
well-documented and recognised country-specific methods for
estimating GE intake based on animal performance data, it is good
practice to use the country-specific methods.” So, the alternative
to the IPCC methodology is to gain country specific data on feed
intake and diet composition.
4.3 CH4 emissions from manure management
The IPCC Guidelines include two tiers to estimate CH4 emissions
from livestock manure. The Tier 1 approach is a simplified method
that only requires livestock population data by animal category and
climate region, in order to estimate emissions. The Tier 2 approach
provides a detailed methodology for estimating CH4 emissions from
manure management systems, and is encouraged to be used for
countries where a particular livestock category represents a
significant share of emissions. This method requires detailed
information on animal characteristics and the manner in which
manure is managed. Using this information, emission factors are
developed that are specific to the conditions of the country.
Tier 2 methane emissions from manure management are estimated by
the following formula:
EFi = VSi * 365 [days yr-1] * Boi * 0.67 [kg m-³] * Σ MCFjK * MS%
ijK jK
1 Good Practice Guidance and Uncertainty Management in National
Greenhouse Gas Inventories
21Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
Where:
EFi = annual emission factor (kg) for animal type i (e.g. dairy
cows)
VSi = average daily volatile solids excreted (kg) for animal type
i
Boi = maximum methane producing capacity (m³ per kg of VS) for
manure produced by animal type i
MCFjK = methane conversion factors for each manure management
system j by climate region K
MS% ijK = fraction of animal type i`s manure handled using manure
systems j in climate region K
Average daily volatile solids (VS) excretion: The IPCC GPG
recommend the following: “The best way to obtain average daily VS
excretion rates is to use data from country-specific published
sources. If average daily VS excretion rates are not available,
country-specific VS excretion rates can be estimated from feed
intake levels.”
B0: The preferred method to obtain the maximum methane producing
capacity of manure (B0) is to use data from country-specific
sources, measured with a standardised method. As up to now no
country specific B0 values have been determined, the inventories
have to be compiled with IPCC default. Inventory accuracy could be
considerably improved, if country specific B0 values were
determined. B0 values were derived from limited and highly variable
data. They are thus connected with high uncertainties.
Methane conversion factor (MCF) Values: Default MCF values are
provided in the IPCC Guidelines for different manure management
systems and climate zones. As up to now no country specific MCF
values are available, the inventories have to be compiled with IPCC
default MCF values. This is another weak point, as default MCF
values are only laboratory based and have so far not been verified
under field conditions. IPCC encourages measurements of emissions
from manure management under field conditions in order to improve
the basis of emission estimates.
Default MCF values are presented in the IPCC Guidelines. The
guidelines contain a range of manure management practices and
assign specific emission factors to them. In order to apply the
Tier 2 approach, it is necessary to have country specific activity
data on manure management system distribution.
Manure management systems: Data on distribution of manure
management systems in each livestock category are important for
accurate emission estimates. There are considerable differences in
emission factors between manure management systems. Manure
management offers promising options for mitigation of greenhouse
gas emissions. It is of crucial importance to have country specific
data on manure management system distribution. Only with these data
available can the effect of more environmentally friendly and
sustainable ways of manure management be shown in national emission
inventories.
The GPG recommend the following: “The best means of obtaining
manure management system distribution data is to consult regularly
published national statistics. If such statistics are unavailable,
the preferred alternative is to conduct an independent survey of
manure management system usage.”
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22Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
4.4 N2O from manure management
All emissions of N2O taking place before the manure is added to
soils are to be reported under “Manure Management”. For the
estimation of N2O emissions from manure management systems only a
Tier 1 approach is available. The IPCC Guidelines method for
estimating N2O emissions from manure management entails multiplying
the total amount of N excretion (from all animal
species/categories) in each type of manure management system by an
emission factor for that type of manure management system.
Emissions are then summed over all manure management systems (see
formulas below).
N excretion per manure management system:
Nex(MMS) = ∑(T)[N(T) x Nex(T) x MMS(T)]
Where:
N(T) = number of animals of type T in the country
Nex(T) = N excretion of animals of type T in the country [kg N
animal-1 yr-1]
MMS(T) = fraction of Nex(T) that is managed in one of the different
distinguished manure management systems for animals of type T in
the country
T = type of animal category
N2O emission per manure management system:
N2O(MMS) = ∑[ Nex(MMS) x EF3(MMS)]
Where:
N2O(MMS) = N2O emissions from all manure management systems in the
country [kg N yr-1]
Nex(MMS) = N excretion per manure management system [kg yr-1]
EF3(MMS) = N2O emissions factor for an MMS [kg N2O-N per kg of Nex
in MMS]
N excretion. N excretion for each livestock category present in a
country must be determined. The IPCC guidelines propose default
values for N excretion. These default values, however, do not
properly reflect country specific conditions. It is desirable to
use national N excretion rates in order to reduce uncertainty in
the estimates.
N2O emission factors. The IPCC guidelines give tentative default
values for N2O emission factors from animal waste management
systems. The default emission factors were derived from a very
limited amount of research and are thus connected with an
uncertainty range of –50 % to + 100 %. They are, however, at the
moment the best estimates available for the calculation of N2O
emissions from AWMS.
Manure management systems: The manure management system
distribution data used to estimate N2O emissions from manure
management are the same as those that were used to estimate CH4
emissions from manure management. It is again of crucial importance
to have national data on manure management system
distribution.
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23Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
4.5 N2O from agricultural soils
Direct N2O emissions are caused by different N-inputs to soils. The
IPCC 1996 method for calculating direct N2O emissions from soils is
based on the assumption that 1.25% of all nitrogen inputs to
agricultural soils are emitted in the form of N2O (expressed as N).
In this method, nitrogen inputs are corrected for gaseous losses
through volatilization of NH3 and NOx.
• Nitrogen sources considered are:
• Animal manures on pastures
• Crop residues remaining on the field after harvest
• Application of sewage sludge on agricultural soils
The nitrogen inputs from all sources are added and the direct N2O
emissions from agricultural soils are calculated using the emission
factor of 1.25%. This method estimates the total direct N2O
emissions, irrespective on type of soils, of land use (e.g.
grassland and cropland soils) and of vegetation, irrespective of
the nitrogen compounds (e.g. organic, inorganic nitrogen), and
irrespective of climatic factors.
4.6 NH3 emissions from manure management
Ammonia emissions from manure management are estimated according to
the EMEP/EEA atmospheric emission inventory guidebook. In the Tier
2 methodology, the flow of total ammoniacal nitrogen (TAN or
mineral N) is followed through the manure management system. The
relative volumes of flow through the different pathways are
determined by country-specific information on animal husbandry and
manure management systems, while the proportion volatilised as
ammonia at each stage in the system is treated as a percentage,
based on measured values and expert judgement.
The detailed methodology requires input data of animal numbers,
nitrogen excretion and manure management systems.
Total ammoniacal nitrogen (TAN) content in excreta: The detailed
method makes use of the total ammoniacal nitrogen (TAN) when
calculating emissions. The initial share of TAN must be known as
well as any transformation rates between organic N and TAN.
N excretion by manure management system: N excretion rates and data
on manure management system distribution are required. Data needs
are harmonised with those described under the sections “CH4
emissions” and “N2O emissions”.
NH3 emissions from storage: NH3 emission estimates differentiate
between emissions from the animal house and emissions from manure
stores. NH3 emissions from storage are estimated from the amount of
N left in the manure when the manure enters the store. Specific
emission factors are available for a range of stores and covers of
stores. Mitigation through lower emissions from stores can only be
shown if national activity data on manure storage are
available.
NH3 emissions from manure application: After estimation of NH3
emissions from housing and storage, the remaining N is field
applied. Different NH3 emission factors are suggested dependent on
the target of land spreading: emissions are thought to be higher on
grassland soils than on cropland soils, because
4 Analysis of data necessary to estimate emissions of greenhouse
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24Analysis of methodologies for calculating greenhouse gas and
ammonia emissions and nutrient balances
infiltration of applied animal waste is slower. Specific emission
factors are available for a range of technical options of manure
application (e.g. band spreading, injection, ploughing in after
application). Many of these options are low cost options that can
effectively reduce emissions after manure application. Activity
data are needed to apply these detailed emission factors and show
the effect of sustainable manure application.
4.7 Data requirements to estimate NH3 and GHG emissions
Emissions are estimated by multiplying activity data with emission
factors. Compiling the national inventory therefore comprises two
main steps: The assessment of national activity data and the
assessment of emission factors (either default or country specific
emission factors). Agricultural emissions strongly depend on the
animal housing, and on the manure management system (MMS)
distribution. These data are a mandatory pre-requisite for accurate
emission estimates that comprise a low range of uncertainty.
Mitigation measures can only show up, if representative data on the
MMS distribution are available. A lack of these data leads to two
major disadvantages: 1. Country specific values can only to a small
extent be integrated in the national emission inventory. Major
parts of the inventory must be set up with default values that do
not always represent processes typically found in the respective
country. 2. Due to the lack in activity data, the effect of
mitigation measures can not show up in the national emission
inventory.
4.7.1 Data requirements
The data in Tables 1 and 2 below are based on the inputs to the
IIASA manure management model, supplemented with items added by
Nick Hutchings, Wilfried Winiwarter and Zig Klimont (IIASA). The
columns IPCC and UNECE show whether the data are already required
to satisfy the reporting demands of the UNFCCC or CLTRP. The items
highlighted in red are those that IIASA indicated where necessary
for identifying economically optimal emission abatement
measures.
The data listed in Tables 1 and 2 are required to enable the
application of a Tier 2 or Tier 3 methodology for the estimation of
CH4, N2O and NH3 emissions. Only with detailed activity data can
the emission estimation equations be applied. The investigation of
policy options and the documentation of abatement measures that
have been implemented will usually require the use of higher Tier
methodologies. Higher Tier methodologies require activity data to
be reported in greater detail. Data items that need to be reported
in greater detail are highlighted in yellow in Table 1.
The values for emissions reported under UNFCCC and CLTRP are
expressed on an annual basis. However, collecting data that permit
emissions to be estimated with a higher temporal resolution may be
of value to policymakers of the following reasons:
• There is evidence to suggest that the damage to certain
ecosystems is related to shorter periods of high atmospheric
ammonia concentrations, rather than the total annual
deposition.
• The formation of secondary particulates that can damage human
health results from an interaction between ammonia and other
atmospheric pollutants. The extent to which the seasonal
distribution of the emission of ammonia interacts with the seasonal
distribution of these other pollutants is therefore of
importance.
• The emission of ammonia and some greenhouse gases from
agricultural sources is dependent upon certain meteorological
parameters, so knowledge about the seasonal variation in activities
related to these emissions permits more accurate reporting.
4 Analysis of data necessary to estimate emissions of greenhouse
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25Analysis of methodologies for calculating greenhouse gas and
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Table 1: Data relating to manure management (needed for each
livestock category)
Data item Units IPCC UNECE Ease Notes
N-excretion kg N yr-1 X X 3 National defaults available, more
detailed data must be collected
C-excretion kg C yr-1 X 3 VS excretion required
Solid and liquid manure system
% X X 1
Time spent grazing hours day-1 X X 2 Ideally include seasonal
distribution
Time spent on yards hours day-1 X X 2 Ideally include seasonal
distribution
Yard flooring – no leachate capture
% X 1 Ideally indicate the surface covering (concrete, bare soil,
woodchips, other)
Yard flooring – leachate capture
% X 1 Ideally indicate the surface covering (concrete, bare soil,
woodchips, other)
Amount of straw added as bedding
kg DM head-1 yr-1
% X 2
Percentage of manure that is spread directly from animal housing to
land. Ideally include seasonal distribution
Housing: fully-slatted floor
Housing: scrubbers or biofilters
% X 1
Manure separation % X 1 Percent of manure that is separated into
solid and liquid fractions
Manure to anaerobic digester (AD)
% X 1 Should be included into UNECE as well
Supplement added to AD: Food waste
Mg yr-1 X 2
Mg yr-1 X 2
Mg yr-1 X 2
4 Analysis of data necessary to estimate emissions of greenhouse
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26Analysis of methodologies for calculating greenhouse gas and
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Data item Units IPCC UNECE Ease Notes
Slurry stored in open tanks
% X 1
% X 1
% X X 1
% X X 1
Manure incinerated % X 1
% (X) 1
Liquid manure = slurry or separated liquid fraction. Ideally
include seasonal distribution
Solid manure applied to fields
% (X) 1
Solid manure = farmyard manure or separated solid fraction. Ideally
include seasonal distribution
Manure application technique: Broadcast – no incorporation
% (X) 1
% (X) 1
% (X) 1
DM = dry matter
(X) = for UNECE; data needed to reliably estimate the effect of
abatement measures
(X) = for soil N balance; data required to calculate manure and
nitrogen applied to the soil
Ease = ease of data collection (1 = easy, 2 = moderate, 3 =
difficult)
Green: Data required by UNFCC or CLRTP. These data are a
prerequisite for Tier 2 and 3 approaches.
Yellow: Data required by UNFCC or CLRTP but which needs to have
greater detail to be useful for policymaking. These data are
helpful for Tier 3 approaches. However, a Tier 3 approach does not
necessarily require all these data. Prioritsation is shown later in
this document.
4 Analysis of data necessary to estimate emissions of greenhouse
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27Analysis of methodologies for calculating greenhouse gas and
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Table 2: Data related to field emissions
(X) = data required to calculate manure and nitrogen applied to the
soil
Ease = ease of data collection (1 = easy, 2 = moderate, 3 =
difficult)
Green: Data required by UNFCC or CLRTP. These data are a
prerequisite for Tier 2 and 3 approaches
Yellow: Data required by UNFCC or CLRTP but which needs to have
greater detail to be useful for policymaking . These data are
helpful for Tier 3 approaches. However, a Tier 3 approach does not
necessarily require all these data. Prioritsation is shown later in
this document.
4.7.2 Data collection
Most of the data in Tables 1 and 2 can easily be implemented into a
questionnaire to be filled in by farmers. E.g. Austria and
Switzerland have already carried out such survey with great
success. In Switzerland, the survey “DYNAMO” was carried out to
assess manure management system distribution (Menzi et al. 2003,
Reidy & Menzi 2005a, b, Reidy et al. 2008b, Kupper et al.
2010a,b). The data were included into the National Emission
Inventory and potentials for abatement options were calculated
based on the country specific data on manure management systems
(Reidy & Menzi 2005c, 2007, Reidy at al. 2008a, Reidy et al.
2009).
In Austria, the survey “TIHALO” has been carried out on a
representative sample of Austrian farms (Amon et al. 2007). The
farmers were able to fill in the questionnaire without additional
help. A sample of the TIHALO questionnaire is attached to this
report (Questionnaire_TIHALO.pdf). The results of the TIHALO survey
were included into the Austrian National Emission Inventories (Amon
& Hörtenhuber 2008, 2009). Through inclusion of national
activity data, inventory uncertainties were reduced. NH3 emissions
from animal husbandry were reduced by 7.1 % only by estimating the
national inventory with more accurate activity data.
Data item Units IPCC UNECE Ease Notes Ammonium nitrate Mg N X X 1
Application rate required Ammonium sulphate Mg N X X 1 Application
rate required Calcium ammonium nitrate Mg N X X 1 Application rate
required
Anhydrous ammonia Mg N X X 1 Application rate required Urea Mg N X
X 1 Application rate required Nitrogen solutions Mg N X X 1
Application rate required Ammonium phosphates Mg N X X 1
Application rate required
Organic manure Mg N X X 2 Sewage sludge, municipal compost,
application rate required
Immediate incorporation of urea % X 1
Imported material for bedding MG N X 2
Crop residue returned to field Mg DM X 3
Crop residue burnt Mg DM X 3 Quarterly resolution needed for arctic
environment/albedo effect
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28Analysis of methodologies for calculating greenhouse gas and
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The REGULATION (EC) No 1166/2008 OF THE EUROPEAN PARLIAMENT AND OF
THE COUNCIL of 19 November 2008 on farm structure surveys and the
survey on agricultural production methods and repealing Council
Regulation (EEC) No 571/88 (EU 2008) lists in Annex V several
characteristics for the survey on agricultural production methods.
These characteristics are as well helpful for the setting up of
good emission estimated and for the proposal of mitigation
measures. The following items have direct influence on the
estimation of GHG and NH3 emissions from agricultural activities.
They could directly be implemented into a survey on manure
management practices as described above.
Animal grazing: The level of detail would be sufficient and the
questions could easily be answered by the farmers.
Animal housing: The level of detail would be sufficient and the
questions could easily be answered by the farmers. In addition to
the animal house, the survey should include questions on a yard and
its utilisation.
Manure application: In this section, additional questions would be
needed: time of the year, when manure is applied, crop to which
manure is applied, manure application technique.
Manure storage and treatment: In this section, additional questions
would be needed: manure stored during warm and cold season, manure
treatment options (biogas, separation, aeration, composting), type
of cover (solid, tent, straw, floating covers).
The data requirements described here go in some aspects beyond the
data requirements described in the TAPAS report from Belgium
(Vervaet et al. 2006).
The animal house needs to include a question on yards
Manure storage must ask for cover, treatment and storage during
warm and cold season
Manure application must ask for timing and application
technique
Farm structure surveys should be carried out every five years. They
should include the items listed in Table 3. Table 3 gives a concise
list of items that should be collected at farm level in order to
improve inventory reporting, show the effect of mitigation
measures, assess environmental impact of farm management practises
and reduce uncertainties in inventory estimates. The data in Table
3 are a prerequisite for the proposal of cost effective and
practical mitigation measures.
Table 3 distinguishes emission sources: housing cattle, housing
pigs, housing poultry, water management, slurry storage, farmyard
manure (FYM) storage, slurry application, farmyard manure (FYM)
application and animal diet. Data collection for the emission
sources is divided into “optimum requirement” and “minimum
requirement”. Activity data listed under “minimum requirement” MUST
be collected. Without these data, a proper inventory reporting is
not possible. The effect of mitigation measures cannot be shown in
the inventory and the cost effectiveness of mitigation measures
cannot be assessed. ”. Activity data listed under “optimum
requirement” SHOULD be collected in order to even more accurately
estimate inventories. They offer more possibilities for country
specific and cost effective mitigation measures and enable the
assessment of environmental impacts of farm management practices.
For most of these data, the additional effort for collecting them
is small and the additional effect is big.
4 Analysis of data necessary to estimate emissions of greenhouse
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29Analysis of methodologies for calculating greenhouse gas and
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Table 3: Data to be collected through surveys at farm level
Activity data collection Reasoning
Housing cattle - minimum requirement Liquid / solid system Tied /
loose housing
EF* differ between both systems, system has great influence on
subsequent losses
Grazing Necessary for estimation a consistent N flow, necessary for
NH3 and N2O emission estimates, IPCC requires data on grazing
Housing cattle – optimum requirement Subcategory of housing systems
prevalent in the country Floor system Yard Air scrubber
Considerable differences in emissions; easy to answer for the
farmer; necessary for the assessment of mitigation measures
Housing pigs - minimum requirement
Liquid / solid system EF differ between both systems, system has
great influence on subsequent losses
Housing pigs – optimum requirement Subcategory of housing systems
prevalent in the country Floor system Yard Air scrubber
Considerable differences in emissions; easy to answer for the
farmer; necessary for the assessment of mitigation measures
Housing poultry - minimum requirement Housing system Manure
treatment
Considerable differences in EF; easy to answer for the farmer
Housing poultry - optimum requirement Drinkers
Frequency of manure removal from the house
Considerable differences in emissions; easy to answer for the
farmer; necessary for the assessment of mitigation measures
Water management – optimum requirement Cleaning of the house, water
addition to slurry Diluted slurry emits less NH3
Slurry storage - minimum requirement
Slurry store cover Great influence on NH3 emissions; cost effective
mitigation measure; likely to become mandatory in the future
Slurry storage - optimum requirement Store size Slurry treatment
Slurry storage during warm and cold season
Considerable differences in emissions; Easy to answer for the
farmer; necessary for the assessment of mitigation measures
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30Analysis of methodologies for calculating greenhouse gas and
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Activity data collection Reasoning
FYM storage - optimum requirement Size of the store and duration of
storage FYM treatment Direct FYM application Duration of FYM
storage Cover of FYM stores
Considerable differences in emissions; easy to answer for the
farmer; necessary for the assessment of mitigation measures
Slurry application - minimum requirement
Application technology
NH3 emissions after slurry application are by far the largest
contributors to total NH3 emissions. Emissions can be effectively
abated by low emission application techniques. Some countries give
subsidies for low emission application techniques. Environmental
effect of these subsidies does not show up if activity data are
unavailable.
Application to grassland or arable land Differences in EF Slurry
application – optimum requirement
Timing and amount of application
Incorporation after application
Considerable differences in emissions; easy to answer for the
farmer; necessary for the assessment of mitigation measures; esp.
timing and amount of application are low cost or even no cost
mitigation measures. They will only show up in the inventory if
activity data are available.
FYM application - minimum requirement Application to grassland or
arable land Differences in EF
Incorporation after application Drastically reduces NH3 emissions;
only measure available to reduce NH3 emissions after FYM
application.
Animal diet – optimum requirement
Components of cattle diet
Important influence on N excretion and CH4 emissions from enteric
fermentation; information will greatly help to improve national
defaults on CH4 emissions from enteric fermentation, N and VS
excretion; all mitigation measures set at the beginning of the
chain will have the largest potential to reduce emissions
Components of pig diet
Important influence on N and VS excretion; information will greatly
help to improve national defaults N and VS excretion; all
mitigation measures set at the beginning of the chain will have the
largest potential to reduce emissions
Phase feeding for pigs
One of the most effective measures to reduce N emissions from pig
manure; measure can be implemented a low or no costs; farmers might
even gain by reducing N content in the pig diets.
* Emission Factors
5 Data necessary for the calculation of N and P balances
31Analysis of methodologies for calculating greenhouse gas and
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5 Data necessary for the calculation of N and P balances
5.1 General
Unlike the situation for greenhouse gas and ammonia emissions,
there is currently no international legal framework relating to
nitrogen and phosphorus balances. As a consequence, there is no
legally- established international standard terminology or
methodology for these balances. The lack of a standardised
terminology has led different authors to refer to the same
calculation methodology by different names or to refer to different
calculation methodologies by the same name. The terminology used in
this report is summarised in Annex “Consolidated list”.
It is important to distinguish between nutrient balances and
nutrient budgets; nutrient balances calculate the difference
between the input and output of a nutrient across the system
boundary. This calculation also enters a nutrient budget but in
addition, the balance (or surplus) is then partitioned between loss
pathways.
A farm nitrogen budget is shown in figure 1
Figure 1: A farm nitrogen budget
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32Analysis of methodologies for calculating greenhouse gas and
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The main inputs to the farm are mineral fertiliser, imported animal
manure, fixation of atmospheric nitrogen by some (mainly
leguminous) crops, deposition from the atmosphere and livestock
feed. Inputs in seed and bedding used for animals are generally
minor inputs, although the latter can be significant for some
traditional animal husbandry systems. The main outputs from the
farm are in crop and animal products, and in exported manure.
Gaseous losses occur from manure in animal housing, in manure
storage and after field application. Other gaseous losses occur
from fields; from applied fertiliser, crops, soil and crop
residues. Losses to ground and surface water occur via leaching or
run off of nitrates, ammonium and dissolved organic nitrogen (DON).
On poorly managed farms, nitrogen can also be lost in run off from
animal housing, animal holding areas and manure storage.
The main nitrogen flows within the farm are in the consumption of
crop products by the livestock, the return of nitrogen to the field
in the excreta of grazing animals, use of straw from the fields as
bedding in livestock housing and the removal of manure from animal
housing and manure storage for field application.
The farm phosphate budget is shown in figure 2. The main difference
between the nitrogen and phosphate budgets is the lack of gaseous
emissions in the latter.
Figure 2: Farm phosphate budget
5 Data necessary for the calculation of N and P balances
33Analysis of methodologies for calculating greenhouse gas and
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5.2 Methodologies related to nitrogen
There are three nitrogen balances in common usage.
5.2.1 Farm gate nitrogen balance
A farm gate nitrogen balance calculates the amount of nitrogen
imported into the farm in commodities and subtracts from it the
amount exported from the farm in agricultural products. This is
illustrated in Fig. 3 below. The farm gate nitrogen balance is
usually divided by the land area associated with the agricultural
production, so that the result is expressed in terms of kg N ha-1
year-1. The advantage with this balance is that with the exception
of manure imports and exports, it relies on readily documented
commodity flows. However, it has the disadvantage that it ignores a
number of inputs that under certain circumstances can make a major
contribution to the supply of nitrogen to the farm. For example,
biological nitrogen fixation can make a major contribution to
nitrogen supply, particularly on organic farms. As a result, this
indicator must be considered obsolete.
Figure 3: Farm gate nitrogen balance
5.2.2 Farm nitrogen balance
A farm nitrogen balance calculates the amount of nitrogen entering
the farm and subtracts from it the amount of nitrogen exported from
the farm in agricultural products. The difference between the two
represents the amount of nitrogen lost to the environment, plus
changes in the amount stored within the farm (principally in the
soil). This is illustrated in Fig. 4 below. The farm nitrogen
balance is usually divided by the land area associated with the
agricultural production, so that the result is expressed in terms
of kg N ha-1 year-1. The farm nitrogen balance is also sometimes
referred to as the farm nitrogen surplus. The rationale for this
indicator is that it reflects the average nitrogen pollution
potential of agricultural land within the area under consideration
(i.e. farm, region, state etc).
5 Data necessary for the calculation of N and P balances
34Analysis of methodologies for calculating greenhouse gas and
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Figure 4: Components of a farm nitrogen balance
Atm. dep. = Atmospheric deposition, Fixation = biological
fixation.
5.2.3 Gross nitrogen balance
A gross nitrogen balance calculates the difference between a. the
sum of livestock excretion, mineral and organic fertiliser, seeds
and biological fixation and b. crop products removed by harvesting
or by grazing. This is illustrated in Fig. 5 below. This balance is
used by the OECD/EUROSTART (OECD 2007) and although not expressed
explicitly, appears to have the same rationale as the farm nitrogen
balance.
Figure 5: Gross nitrogen balance; components included (bold) and
associated flows (grey)
5 Data necessary for the calculation of N and P balances
35Analysis of methodologies for calculating greenhouse gas and
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As for the farm balance, the gross nitrogen balance requires
information on the nitrogen input in fertiliser, imported manure,
fixation, seeds and plants, and atmospheric deposition. In
addition, the gross nitrogen balance requires information on the
excretion of nitrogen by livestock on the farm. The nitrogen flows
through animal housing and manure storage (the greyed flows in Fig.
5) are not considered explicitly. In addition to information on the
export of crop products from the farm, the gross nitrogen balance
also requires the output of nitrogen in forage consumed by grazing
animals and the removal of crop products for use as feed for
animals. Like the farm nitrogen balance, the gross nitrogen balance
represents the amount of nitrogen lost to the environment, plus
changes in the amount stored in the soil.
5.2.4 Soil nitrogen balance
A soil nitrogen balance is shown in Fig. 6.
A soil nitrogen balance calculates the difference between (a) the
total N input to the fields via livestock manure, mineral and
organic fertilisers, seeds, biological fixation and crop residues
and (b) the total N output from the fields via harvested crop
yield. This balance is used by CAPRI (Leip et al, 2010). Although
the soil nitrogen balance is relatively simple, it requires much
more information than is necessary for a farm or gross nitrogen
balance. In order to calculate the amount of nitrogen applied to
the fields in organic manure produced on the farm, the excretion by
livestock must be calculated and the gaseous emissions of nitrogen
in animal housing and manure storage must be estimated. When
calculating a soil nitrogen balance at the scale of the MS, it is
appropriate to use the country specific nitrogen excretion values
reported under UNFCCC and the Tier 2 methodology of the EMEP/EEA
Air Pollutant Emission Inventory Guidebook for calculating the
gaseous emissions of nitrogen in animal housing and manure storage.
Additional information is also required on the nitrogen taken up by
the crop that is returned to the soil in crop residues.
Figure 6: The components of a soil nitrogen balance.
Components in grey must be quantified in order to calculate the
nitrogen in manure applied to the soil.
5 Data necessary for the calculation of N and P balances
36Analysis of methodologies for calculating greenhouse gas and
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5.2.5 Changes in soil nitrogen storage
Changes in soil nitrogen storage are commonly assumed to be zero.
This is the case for OECD and for CAPRI. This assumption is
reasonable for the long-term. However, given the nature of the
dynamics of carbon and nitrogen in the soil, the long-term should
be considered 50 to 100 years. Empirical measurements made in
Denmark and in the famous Rothamsted long-term field experiments in
the United Kingdom have found significant changes in soil nitrogen
storage over time. These changes appear to be related to the
changing structure of agricultural production. Thirty to 50 years
ago, many farms had mixed production enterprises i.e. they produced
both crops and livestock. The increasing specialisation of
agricultural production in the last 50 years has resulted in
notable differences in the inputs of organic matter to the soil on
different farm types. On farms that choose to specialise in arable
production, the removal of livestock has led to a reduction in
organic matter inputs into the soil via animal manure and crop
residues. The reduction in input of crop residues is mainly
associated with the disappearance of grass from the crop rotation,
since this crop contributes much more organic matter to the soil
than arable crops. This has led to a reduction in the soil nitrogen
storage of up to 30 kg ha-1 year-1. The reduction in soil storage
on farms that choose to specialise in pig production is somewhat
less. In contrast, soils on farms that choose to specialise in
cattle production has seen accumulation is in soil nitrogen of
30-50 kg ha-1 year-1.
Further, changes in soil nitrogen storage are likely to be of major
importance where wetlands. peatland and coastal areas have been
drained for agriculture. Such soils typically have high or very
high initial levels of organic matter, due to the anaerobic or
acidic conditions that existed prior to drainage. Drainage leads to
aerobic conditions developing for some or all the year, resulting
in the mineralization of organic matter and the release of mineral
nitrogen. In such situations, 100-300 kg ha-1 of organic nitrogen
may be released annually, until the organic rich top layer finally
disappears.
Assessing the change in soil nitrogen storage is difficult because
the amount stored is large compared to the changes that typically
occur in a single year. It is possible to do over the medium term
(about 10 years) if a sufficiently large number of samples are
taken. However, on former wetland or marine areas, measurements are
complicated by reductions in the height of the soil surface, due to
compaction and to the loss of carbon in gaseous form.
Data relating to changes in cropping pattern and livestock density
over time can be used to detect whether farms have differed
substantially in their development trajectory over time.
5.2.6 Choice of balance
A farm nitrogen balance and the gross nitrogen balance depend on
losses to both atmospheric and aquatic environments, so are broad
indicators of the potential environmental impact of agricultural
nitrogen. They largely rely on inputs and outputs that can be
quantified from existing documentable sources (e.g. farm accounts).
In contrast, the soil nitrogen balance depends to a great extent
upon losses of nitrate, so is a better indicator of the potential
impact on the aquatic environment. This relationship could be
improved further by subtracting the ammonia emission associated
with field application of manures and fertilisers (see section on
ammonia emission). However, calculation of a soil nitrogen balance
demands estimates of livestock nitrogen excretion and the emissions
of nitrogen in animal housing and storage. The data necessary to
obtain these estimates are more difficult to obtain and associated
with greater uncertainty than those necessary for the calculation
of the farm nitrogen balance.
5 Data necessary for the calculation of N and P balances
37Analysis of methodologies for calculating greenhouse gas and
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5.2.7 Revision of methodologies
Gross nitrogen balance
As noted by OECD (2007), estimates of nitrogen excretion obtained
from manure sampling vary widely. The excretion of nitrogen by
livestock and the nitrogen consumed by livestock in feed produced
on the farm are two of the four elements of the livestock nitrogen
balance (the other two being imported livestock feed and exported
animal products). Over the lifetime of an animal, the nitrogen
stored in the animal is zero. To maintain the continuity of
nitrogen (i.e. since nitrogen is neither lost or created, just
redistributed), the following must be true:
imported feed N + farm-produced feed N = animal production N + N
excreted (Equation 1)
By rearranging this equation, one obtains:
N excreted = imported feed N + farm-produced feed N - animal
production N (Equation 2)
As noted by OECD (2007), the estimate of farm-produced feed
nitrogen appears both in the input and output terms of the gross
nitrogen balance:
Input = imported manure + fertiliser + excretion + other N inputs
(Equation 3)
Output = exported manure + marketed crops + farm-produced feed
(Equation 4)
Substituting for excretion:
Input = imported manure + fertiliser + imported feed +
farm-produced feed - animal production + other N inputs (Equation
5)
As a result, the estimate of farm-produced feed nitrogen cancels
out and the gross nitrogen balance is calculated from the
following:
Input = imported manure + fertiliser + imported feed + other N
inputs (Equation 6)
Output = exported manure + marketed crops + animal production
(Equation 7)
The imported animal feed and exported animal products can be more
easily and more accurately determined than the farm-produced animal
feed (e.g. via farm accounts). We therefore consider that the gross
nitrogen balance would be more accurately calculated using equation
6 and 7.
The gross nitrogen balance does not include the import of nitrogen
in bedding for livestock. For organic, high welfare and some
traditional livestock husbandry, the demand for bedding can be
substantial and may require the import of bedding material. This
can be illustrated if one considers an organic dairy farm where the
livestock are kept in loose housing/deep litter that requires the
import of an average of 5 kg straw dry matter ha-1 d-1. If the
concentration of N in the straw is on average 1%, this is
equivalent to just over 18kg N ha-1 yr-1. Using typical Danish
values, this would increase the gross nitrogen balance by 16%. We
consider the input of nitrogen and via imported bedding should be
added to the gross nitrogen balance .
5 Data necessary for the calculation of N and P balances
38Analysis of methodologies for calculating greenhouse gas and
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If the recommendations concerning the calculation methodology and
the inclusion of imported bedding are accepted, the gross nitrogen
balance and the farm nitrogen balance become synonymous.
Soil nitrogen balance
Some clarification of terminology is required concerning the use of
crop residues and crop products in the calculation of the soil
nitrogen balance. Leip et al (2010) refer to crop products and crop
residues. OECD/EUROSTAT refer to crop residues, marketed crops and
non-marketed crops. The OECD/EUROSTAT terminology is to be
preferred as it is clearer. However, it could be usefully modified
as follows:
• Crop residues = plant material left on the field after
harvesting.
• Marketed crops = all crop products sold and exported from the
farm.
• Non-marketed crops = all crop products that are produced on the
farm and used on the farm.
The reason for suggesting these changes is to en