The Role of Biogas from AnaerobicDigestion in Irish Agriculture

Tom Knitter

SEAIRenewable Energy Information Office

National Bioenergy ConferenceTeagasc/SEAI/DAFF20th April 2011Tullamore

SEAI REIO - Background

• Created in 1995, based in Clonakilty, West Cork

• Established to promote the use of renewable

resources and provide independent information and

advice on the financial, social and technical issues

relating to renewable energy development

http://www.seai.ie/Renewables/Bioenergy/Anaerobic_Digestion/

Outline

• Overview development, technology andprocess

• Technical requirements and plant components

• Developing a project, economics

• Upgrading Biogas to Biomethane

• GHG-abatement

• Summary

Overview development,technology and process

Biogas use in Europe 2009

Source: EurObservER, Biogas Road map

Sources of biogas:• Landfill

– Light green

• Sewage Sludge treatment– Green

• Others: Agriculture, MSW– Dark green

Units: ktoePrimary biogas production in EU

Different reasons for thisdevelopment:• Feed-in tariffs for bioelectricity• Vehicle fuel• Rural development• Wastewater treatment• Excessive‘ landfilling• Etc.

Biogas: an Energy all-rounder

Biology

• 4 digestion steps by different enzymes and bacteriawithout O2

• Bacteria in last step (methane formation) mostsensitive

– pH-value (fatty acids), normally 7-8– Temperature >36°C

• Temperature– Mesophilic: 35 – 45°C– Thermophilic: 45 – 65°C

• Keep conditions constant– Feeding, temperature in digester/material, mixing,

composition feedstock, etc.

Biology (1)

[ppm: Parts per million; Vol.. - %: volumetric percentage]

20 – 20.000 ppmH2SHydrogensulphide

< 2 vol. - %N2Nitrogen

< 2 vol. - %O2Oxygen

2 - 7 vol. - %H2OWater vapour

25 - 45 vol. - %CO2Carbon dioxide

50 - 75 vol. - %CH4Methane

ConcentrationChemical symbolComponent

Feedstock

Input/gas production

6.1147728020.0Residuals from vegetables

1.02412804.5Pig slurry

60.6120071395100.0Glycerine*

70.316878278795.0Fat

10.72571267540.0Chicken litter/dung

5814007009087.0Grain

1.74120808.0Cattle-slurry

6.0143708025.0Cattle-dung

9.42251108520.0Food waste

kW/t FM dkWh/tm3/t fresh material% of dm% of freshmaterial

kW per t inputmaterial and day

kWh/t fresh inputmaterial

gas-production pert fresh material

organic drymatter

(data can vary)Dry matter (dm)

35% electrical efficiency CHP, 21 MJ/m3, 55% CH4 content, 3,6 MJ/kWh

This table is only intended to provide indicative results. All values are approximate and can varyextremely. Gas yields depend on dry matter content, storage feedstock, handling feedstock. For an

exact calculation, feedstock testing is definitely necessary.

http://www.seai.ie/Renewables/Bioenergy/Anaerobic_Digestion/Digestion_Substrates

Biogas - feedstock yield

1 household

4,000 kWhel./a

6 Cows = 110 t/a

slurry

or

14 t/a fresh grass

silage

or

16 t/a food waste

=

Technical requirements

• Main Components:

– Digester

– Mixer/agitator, pumps

– Feeding systems for solid biomass

– Combined Heat and Power (CHP)

– Etc.

• Components must be suitable for feedstock

• Plant price €4,000 to €7,000/kW

– E.g. 250 kW €1.2m – €1.7m

Biogas plant schemewet continuous system

Continuous Digester

– Vertical/round digester• Most common system• Different heights, diameter• 100 – 4,000 m3

• Several digesters/stages possible

– Plug flow• Horizontal shaft

– Combination

Solid feeding systemCo-digestion

• Feeding in liquid manure store, mixing

– Eventually integrated chopper pump

• External solid feeding system

• Integrated feeding system in pipe

– Pump attached to feeding system

Agitator/pumps

• Agitator/pumps must besuitable for feedstock

• Agitator:– Aim: get high gas yields– Material should be well

mixed (biology)

Combined Heat and Power unit(CHP-unit)

CHP-unit• Modified Gas or Diesel-engine plus a generator

• Well developed units for biogas

• Capacity: 50-2,700 kWel.(4 – 20 cylinders)

– Diesel engines just up to 340 kWel.

• Biogas has to be cleaned (water, H2S, NH3 ...)

Developing a project

Economics

Developing an AD plant

Developing a project is a long process!

?...!

Operating the plant:What is my motivation for installing/operating a plant?Who is operating the plant (24/7 supervision necessary)?

SummaryDeveloping AD facility

1. Feedstock (amount, quality, gas prod.)Sizing plant and CHP, design, regulations

2. Location of plant

3. PlanningLocal authorities

4. Contact supplier/developerFeasibility study/design

5. Financial projectionIncome/cost analysis

Developing steps take place simultaneous

Checklist on website:http://www.seai.ie/Renewables/Bioenergy/Anaerobic_Digestion

1. Feedstock

• Availability and amount:– Stable amount over next months, year(s)?– Does the amount make a plant viable!?

• Gate fee/price– Stable for the next years? Costs calculated realistically

• Regulations– Waste permission, ABP(DAFF), nutrient management plan of

digestate

• Quality– Gas yield/specific gas production, dry matter, organic dry matter

Sizing CHP unit

Sizing the plant andcomponents/technique

Developing an AD plantFeedstock

Example feedstockSize CHP-unit

Tonnes feedstock per day

20 t/d cattle slurry (= 800 kWh)

3 t/d dung (= 480 kWh)

2 t/d chaff (= 1.100 kWh)

3 t/d food waste (= 720 kWh)

Power kW per day

35 kW

20 kW

50 kW

30 kW

28 t/d

≈ 10.000 t/a

kWh/24 hr

Plant design: Organic loading rate, retention time

Retention Time: 35 d (slurry) – 100 d (energy crops), feedstock remains in main digester(s)

Organic Loading Rate: < 4.0 - 4.5 kg oDM/m3/d; How much organic dry matter (oDM) added per m3 per d

www.seai.ie/Renewables/Bioenergy/Anaerobic_Digestion/Process_parameters/

≈ 135 kW

Financial projection

• Income:

– Selling electricity (REFIT) and heat

– Fertilizer value/selling fertilizer

– Gate fee

• Running Cost, extract:

– Loan, interest (investment), insurance

– Maintenance/repair/spare parts plant

components/CHP

– Management/administration

– Etc.

Analyzescenarios!

What if...?

Checklist developing a project:

http://www.seai.ie/Renewables/Bioenergy/Anaerobic_Digestion/Economics/

Upgrading biogas to Biomethane

Biogas – an Energy all-rounder

2

Source: IEA

Upgrading Biogas (AD)

• Biogas (55% CH4) upgraded to Biomethane (>95% CH4 =natural gas)

• According to IEA upgrading Biogas in early commercial stage(2009)

• App. 100 installations in Germany and Sweden together, butalso Switzerland, Lithuania, Austria

• Injection: BG already connected to end user (700,000customer)

• Vehicle fuel: Interesting for waste companies (see Sweden)– Cars commercially available

• Amount: 25,000 – 80,000 t/a Energy Crops, Waste 30,000 t/a

GHG abatement

Green House Gasemissions by source

• Overall CO2 emissions: 62 Mt/a

• Agriculture 28% of overall CO2 emissions in 2009

– App. 17.4 Mt CO2

• AD technology can reduce CO2 emissions significantly:

– Avoid CH4-emission (slurry storage) and use that potential

– Avoid NO2 and NH3 emissions by dung storage and spreading

– Electricity and heat production (replacement fossil fuels)

– Replacement inorganic fertiliser (energy intensive)

High potential for CO2 reduction

CO2 emissions calculation

Irish agriculture CO2 emission: 17.3 Mt CO2 eq.

Germany: Reduction of 13,24 Mt CO2 just with AD (emissions,energy production)

Summary

Summary Biogas

• AD is a clean, well developed and commercially availabletechnology

• AD/Biogas will play a significant role in the futureenergy market– Getting energy independent/self sufficient– Potential to supply constant electricity, heat, gas, transport fuel

up to 8,500 hrs/a– Contribution to all Renewable Energy targets

• RES-E, RES-H, RES-T

– Production close to demand - can be stored - dispatchable power

• Creating and supporting rural jobs and opportunities forseveral years– Money stays in rural area/Ireland– Ongoing employment after construction (supply chain, operation,

maintenance)– Farmer harvesting energy (energy supplier)!

• Efficiencies up to 90%

• Environmental benefits

– Fulfill EU directives (landfill, high efficient CHP,

etc.)

– Save CO2/CH4 emissions (abatement)

– Digestate valuable soil fertiliser

• Higher homogeneity

• Higher pH-value

• Better availability of nutrients (saving inorganic

fertiliser)

• Significant reduction in pathogens (e.g. E. Coli,

Salmonella, Enterococcus etc.) and odours

– Closed nutrient circle (waste reduction)

Source picture: Bioenergy-village Juehnde

Summary Biogas

Summary Biogas

• Fast development and improvement of technology

• A lot innovations on the market or in the RD+D,

demonstration or early commercial stages

• Target: More energy (kWh) from the same area (ha)

– Saving 30 - 40% of the feedstock in the future

• Performance more efficient

produce cheaper green electricity

Further AD information

See: www.seai.ie/Renewables/Bioenergy/Anaerobic_Digestion/

• Updated AD information

• Literature (IEA), handbook, digestate, energy crops,operation, process, biology, feedstock

• Presentations recent events

• Connection to the grid

• First steps in developing a plant, checklist

• Etc.

Thank you

Tom Knitter

SEAI - Renewable Energy Information OfficeUnit A, West Cork Technology Park

Clonakilty, Co. Cork

tom.knitter@reio.ie

+353 (0)23-88 63 237

+353 (0)87-68 27 688