APPROPRIATE FARM & ON-SITE ANAEROBIC DIGESTION: Organic nutrient recycling & Pollution mitigation

1. APPROPRIATE
FARM & ON-SITE
ANAEROBICANAEROBIC
DIGESTION
Organic nutrient recycling &
Pollution mitigation

2. • Context
• What is AD?
• AD Viability
• Do’s and Don’ts
• Case study
Topics
• Considerations for putting
a project together

3. Context
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“The earth is what we all have in common”
(Wendell Berry)

4. Long-lived digester design
Ø 450 years combined operation
Ø Many running > 20 yrs
Ø Low parasitic energy
Ø Simple, user-friendly

5. Context & Drivers - It’s time to act!
• Climate change: Last year, we reached 400ppm CO2 in
the atmosphere
• The era of cheap energy is over – global energy
transition. Energy is NOT just your lights and heat.
It is food.
• Population growth: 2050 9BN? 11BN?• Population growth: 2050 9BN? 11BN?
• Increasing urbanisation: 1.4M people/week (B’ham)
• Population age.
2000 – 2BN children –
Prediction for 2100?
Legal CO2 reduction targets

6. Energy
Food
So what can I do?
Reduce
(Efficiencies)
Re-
THINK!Reuse
Recycle
Water
THINK!
(resilience)

7. UK Storms: “We have no
heating,
no power, no hot food”
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8. What is
Anaerobic
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Anaerobic
Digestion?
AD is ……

9. …. a cow, not a tractor!

10. What is Anaerobic Digestion?
Organic
material*
Heat
ANAEROBIC DIGESTER @ 40°C
Biogas
H2S & other gases
To CHP to create
renewable electricity
OR
To boiler, Aga,
Rayburn, gas ring(s)
Digestate
(Biofertiliser)
Optional separation intoOptional separation into
soil conditioner & liquid
fertiliser
OR
Spread to land
An enclosed vessel: heated, stirred (either by
60% CH4 & 40% CO2
An enclosed vessel: heated, stirred (either by
gas mixing or mechanical agitation)
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Nature’s own biological decomposition by micro-organisms
in the absence of oxygen (anaerobic)
It is a natural process that breaks down organic material
in an airless, heated and mixed tank

11. Anaerobic Digestion Composting
Degradation of organic matter in the
absence of oxygen (bacteria, archaea,
protozoa that do not need oxygen to grow
– anaerobes)
Degradation of organic matter
in the presence of oxygen in air
(bacteria/fungi need oxygen to
grow – aerobes)
Best way to treat all non-woody organic
wastes
Best way to treat all woody
organic wastes
Requires heat (ideally) Generates its own heat
(exothermic)
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Creates CO2 Creates CO2
Creates fertiliser whose nutrients are more
available to plants, as well as a soil
conditioner
Creates a soil conditioner /
fertiliser
Creates biogas which can be used to
create electricity, heat or vehicle fuel

12. Biogas
60% CH4
40% CO2
Boiler
CHP
Heat
Losses
Heat
Losses
Electricity
75%-85%
25%-15%
60%-45%
30%-40%
40% CO2
Upgrade
Losses
Biomethane
CO2, H2S, H2O
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15% (rem)

13. SimpleAD plant running on slurry
Cow slurry in
Gas for cooking or heating farm house
Liquid used on grass
Fibre ploughed in
Thermal solar heated digester
Biofertiliser
Digester
40°C
An enclosed vessel:
heated, stirred
(case studies used
gas mixing)
Biogas
60% CH4
40% CO2
Feedstock:
Gravity or
auger fed
Gas
Holder
Liquid
Fibre
Storage
Direct Use
Heat/hot water
Boiler:
(digester heating)
Aga/Rayburn

14. AD plant with Combined Heat & Power (CHP)
Digester
40°C
Biogas
Gas
Holder
CHP
-Tends to need a lot more feedstock
-More complicated to run
Electricity
60% CH4
40% CO2
Liquid
Fibre
Storage
Biofertiliser
Heat Heat
Anaerobic Digester
Feedstock

15. Using the biogas fromAnaerobic Digestion

16. Case study – Bus Bristol-Bath
Courtesy of University of Southampton: Dhivya, Alba & Leo-Paul

17. Why AD?
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18. Farm
Abattoir
Food
Processing
The Food Production Process
•Currently, there is ’waste’
at every stage of the process
•AD closes the loop
•Nutrients must go back to land
in a beneficial way
Fertiliser(nutrients)backtoland*
Retail
Restaurant
& Home
Anaerobic DigesterEnergy
from
Biogas
*Recycle NPK &
micronutrients as fertiliser
*Pathogen/weed seed kill
*Sequester carbon
*Improve soil structure
Fertiliser(nutrients)backtoland*

19. Why AD of slurries/manures?
1989 – Clive Pugh’s Slurry System
1990 – With
• Displacement of fossil fuels (both fertiliser and energy)
• Reduction in carbon dioxide, ammonia, nitrous oxide and
methane losses to atmosphere greatly reduced GHG potential
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1989 – Clive Pugh’s Slurry System WRI (Murcott) Digester

20. Environmental Benefits of AD
• Returns micronutrients, water, carbon, nitrogen to soil
• Reduction in carbon dioxide, nitrous oxide and methane
losses to atmosphere greatly reduce GHG potential
• Offensive odours eliminated/reduced
• Kills many weed seeds/pathogens• Kills many weed seeds/pathogens
• Addition of humus improves the physical properties of soil
water holding capacity, aeration, water soluble aggregates
and increased crop production up to 20-30%
• Reduction in BOD (80-95%)
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21. • Improved slurry handling
• Less water use
• Fertiliser benefit is not just NPK,
but significant and essential trace
elements
• Fertiliser performance is superior;
nutrients are more readily
available, particularly Nitrogen
• Digestate does not hinder clover
Farming Benefits of AD
• Digestate does not hinder clover
growth like synthetic fertilisers.
• Faster re-grazing – healthier
animals
• Increased ley life
• Production of energy and fertiliser
reduces costs of food production,
improves profitability and adds an
income stream to the farm
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22. Digester
Economics
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Economics

23. What is ‘Small Scale’?
•German definition (<75kWe)?
•DECC definition (<500kWe; <250kWe)
•UK Pre-FIT definition?

24. What is AD viability?
Feedstock
CAPEX/OPEX
Income/Avoided
Expenditure
AD
Feedstock
• ‘If it costs me less to manage – that’s for me!’
• ‘Waste is a continuous & increasing cost to the
business’
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25. Biogas Potential
150
200
250
300
Solid Colours - Biogas Yield (Nm3/t FM) Average & Variance
Hatched Colours - Methane Yield (Nm3/t FM) Average & Variance
FOOD WASTE: use 120-130 m3 at 60% CH4
ä
0
50
100
Cattle Slurry Pig slurry Cattle dung Fodder beet Potato pulp Poultry
manure
Apple
pomace
Maize silage Whole crop
cereal silage
Grass silage Grape
pomace
CAPEX/OPEX
AD
Income/Avoide
d Expenditure
Feedstock

26. Feedstock Quality/Cost
Methane
content
(slurry)
Methane
Yield
(Nm3/t
FM)
Feedstoc
k volume
(t/d)
CHP
kWe
Income/day
@£0.192/kW
e
Varian
ce
Low 11 6 8 £38 -21%
Average 14 6 10 £48
High 20 6 15 £69 43%
Cost of additional feedstock
when cows not in year-round?
CAPEX/OPEX Income/Avoide
d Expenditure
Feedstock

27. On-site cost reduction
• Waste management cost savings
• Energy savings
• ?Fertiliser savings – Digestate has N, P, K and trace elements
Government support
Financial Drivers for On-site AD
Government support
• Incentives, eg RHI, Feed-in Tariff (FIT) – for generation
• Export Tariff
• Grants (feasibility only)
• Carbon reduction (tax?)
AD
Feedstock
CAPEX/OPEX
Income/Avoided
Expenditure

28. ‘Typical’ Capex
Specific Investment Costs
Biogas plant <= 500kWe £2.6K-£5.2K
(£1.2K-£3.6K-£10K)/kWe
Biogas plant >500kWe <=£2600
(£2.3-£4.4-£6.2K) /kWe
CHP 150 kWe £750 (£1000) /kWe
CHP 250 kWe £635-£750
Source: FNR, 2012, Arup, 2010
CHP 250 kWe £635-£750
(£850-£1000) /kWe
CHP 500 kWe £500/kWe
Cost of biomethane upgrading, 250 Nm3 6.7p-8.6p/Nm3
Cost of biomethane upgrading, 1000 Nm3 5p-6.7p/Nm3
Income/Avoided
Expenditure
Feedstock
CAPEX/OPEX
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29. Capital costs for farm scale CHP < 250 kWe
(Apples and Pears)
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30. Effect of Energy Prices on Profit
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31. Operating Costs
Energy: Pumps, heat exchangers, macerators, automatic
valves, augers, mixers, agitators, gas storage, (except
bell-over-water configurations); digestate separation
(if included), dumping excess heat from a CHP
KISS principle applies!
Regulatory: CHP emissions tests, training, permitting,
insurance. Regulation must be risk based.
Consumables: H2S removal, pump parts
Maintenance: CHP oil/plugs/servicing, pump parts,
analyser/sensor calibration/replacement, grit removal
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Income/Avoided
Expenditure
Feedstock
CAPEX/OPEX

32. Do’s and Don’ts
• Must be designed for minimal daily
operational time. Must work 24/7
with minimal input.
• Very simple feeding
• Fresh slurry
• Minimal added water (preferably• Minimal added water (preferably
none) – rain or seepage
• Minimal parasitic load (electrical and
mixing)
• Minimal maintenance of mixing (eg
gas vs propeller)
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Income/Avoided
Expenditure
Feedstock
CAPEX/OPEX

33. Typical Digester
Feedstock
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34. Photo: Courtesy of Bourne Valley Associates
Larger modern 80kWe digester: slurry from 120 cows, chicken manure
from free range broilers & some added maize

35. Dealing with grit

36. Putting a project together….

37. Feedstock considerations
• Driver: feedstock volume or output?
• What feedstock is available and how much
biogas will it yield?
• If imported, is it a secure supply?
• What type of input ?
• Crop – self perpetuating.
• Muck / waste – enhancing
• Waste – gate fee + enhancing
• Seasonality / variability
• Cost of buying/growing/haulage
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38. What you need to think about
• Grid Capacity
– How much can you export?
– How much will it cost?
• Best use of biogas
–Boiler, CHP, biomethane or combination?
–Electricity use (as much on-site, unless export–Electricity use (as much on-site, unless export
premium)
–-Heat (helps with overall profitability)
• Digestate
• How much land do you have available?
• Planning/Regulation
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39. AD as diversification
• AD does not detract from your core business.
It enhances it!
• AD does not require re-skilling.
If you understand cow nutrition you can already feed a digester.
AD is NOT about getting another job, it’s a way of
making the job you already do more profitable.
If you understand cow nutrition you can already feed a digester.
• AD provides an alternative income stream
Non food and independent of supermarkets – currently.
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40. Examples
• 1000 Cows
100kW - income £ 100K
1000m³ - cost £ 490K roc 20%
• 250 cows + 2T Grass 5T Chicken Muck
160kW - income £ 130K160kW - income £ 130K
1000m³ - cost £ 670K roc 19%
• 500 cows + 5T grass + 6T Chicken Muck
240kW - income £ 190K
1650m³ - cost £ 960K roc 20%
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41. Drivers
Make money
Diversification
Nutrient recycling
Energy production
Sustainability
Self-sufficiency
Education*
Other considerations
Feedstock handling
Biogas utilisation
Plant design
Finance
Operation
H&S / Risk assessments
Parasitic load
Putting it all together
Education*
Trials*
Permitting/Regulatory
EA
AHVLA
Planning Authority
Ofgem
Others?
EA/Planning Considerations
Odour
Noise
Vehicle movements
Proximity to ‘sensitive receptors’
AONB?/SSSI?
Aesthetics
Parasitic load
Digestate/feedstock storage
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42. Hub & Pod

43. Home Digester
Solar PV
Biogas
Solar PV
Sedum roof
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45. 20m3 Digester
New style de-gritting
20m3 digester
Food waste digester trials
20m3 in situ
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46. Convert a
slurry store?
Digest
high solids?
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47. James Murcott
Angie Bywater
Methanogen (UK) LtdMethanogen (UK) Ltd
info@methanogen.co.uk
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M: 07753 571371
Twitter: BiogasUK
Blog: anaerobicdigest.tumblr.com