This document discusses biogas and anaerobic digestion as a renewable energy solution for rural communities. Biogas is produced through the bacterial breakdown of organic matter in an oxygen-free environment. This process recovers energy from waste materials like animal slurry and food waste in the form of methane gas, while also producing a nutrient-rich fertilizer. The document provides examples of small-scale community biogas plants that treat agricultural waste to produce heat and electricity. Planning a community biogas plant requires surveying available waste resources, identifying a site, determining end uses for the biogas, addressing regulatory requirements, and financing the project through community involvement and ownership.

1. “To encourage and empower small rural communities to
take ownership of and develop community led renewable
energy solutions for the benefit of their own locality”

2. Ss
Biogas / Anaerobic Digestion for the Community
Noel Gavigan
Technical Executive
Irish BioEnergy Association
Noelgavigan [at] irbea.ie

3. • Recycles organic material
• Recovers the energy and
converts it into usable gas
• Recovers the nutrients and
allows them be used back on
farmland
BIOGAS DIGESTER
Animal slurries,
Energy Crops
Food Waste,
Food
processing
Waste
Electricity Heat Vehicle Fuel
Digestate
Fertiliser
What is Biogas /
Anaerobic digestion??
https://www.youtube.com/watch?t=3&v
=KgUwdepePF4

4. What is Biogas? - What Happens?
• Bacteria digest organic matter in
a very similar manner to
rumenants (cows / sheep). The
Energy is converted into
Methane gas.
• The gas can readily be used to
produce heat, electricity or be
used as vehicle fuel after
purification.

5. Industrial Scale Biogas
• 250kwe – 5MWe scale
• Capital Expenditure of €4-5m / MW
• Feedstocks: Energy Crops
• Feedstocks: Waste Materials
• Feedstocks: 10,000 tonnes to 200kt

6. Developing World Biogas Plants

7. Biogas Composition
• Heating
• Electricity
• Upgrading to gas
grid
• Vehicle Fuel
Uses of Biogas

8. Digestate – High Value
Fertiliser
• Liquid slurry – spreadable with normal
farm machinery
• Retains all the original nutrients from
the feed material
• Nutrients are more available to the
plant, as much as double the amount of
available Nitrogen
• Digestate can be separated into liquid
and solid portions
• Solids are high in Phosphate and
Potassium
• Liquid is high in Nitrogen

9. What Materials can be used in a biogas plant?
• Agricultural waste & Products
• Animal slurries
• Harvest residues
• Grass / Maize / Cereals

10. What Materials can be used in a biogas plant?
• Food processing waste
• Meat/fish processing waste
• Dairy waste
• Brewery spent grains
• Vegetable waste
• Waste from prepared food factories
Offal

11. Food left over
Fruits and vegetables
• Food Waste
• Household collected food waste
• Catering Waste
What Materials can be used in a biogas plant?

12. Gas Yield from Various Materials
Substrate Dry matter Biogas
Methane
Content
Net Energy
Heating value Electricity Electric value
90% efficient 35% efficient 19c/kwh
[%]
m3
/ton fresh
weight
% kWH / Tonne @8c/kwh [kWh el./ton]
(not including heat
value)
Cattle Manure
8 25 60 162 € 11.70 57 € 10.80
Pig manure 6 20 60 130 € 9.36 45 € 8.64
Milk whey 8 58 53 333 € 23.97 117 € 22.14
Brewers yeast
(pressed, cooked)
25 152 62 1021 € 73.48 357 € 67.87
Potato pulp 19 108 50 585 € 42.11 205 € 38.89
Slaughterhouse
waste (rumen)
15 60 55 357 € 25.73 125 € 23.77
Bread and baking
residues
77 570 53 3272 € 235.57 1145 € 217.57
Corn silage 35 216 52 1216 € 87.58 426 € 80.89

13. Example 1: Gießen Dairy Farm (Germany)
Small-scale biogas plant (installed capacity 75 kW).
Feedstocks: cattle slurry (10.950 m3/year)
Energy use: heat for self-consumption, electrical energy
is fed into local power grid.
Digester: 600 m3 concrete tank
Biogas valorisation unit: 75 kW boiler.
Energy production : 630 Mwhel/a; 740 MWhth/a
Investment: 500,000€
Estimated payback period = 6 years

14. Example 2: Fahringer farm, Rettenschöss (Austria)
Small-scale biogas plant (self-built, low-cost).
Feedstocks: cattle slurry, whey, pig slurry
Energy use: heat for the housing and the cheese plant.
Digester: 150m3 concrete tank
Biogas valorisation unit: 50kW boiler.
Gas production : 150-180m3 biogas/day
Investment: 35,000€
Annual Maintenance cost (estimate 5% CapEx €1750)
Gas value €6570/yr
Payback 7 years
Data obtained from a report
of the BIOREGIONS project
(www.bioregions.eu)
compiled by Patrick Daly

15. Example 3: Methanogen: Waterford, Ireland
• Built 1992 – running ever since
• 2 x 70m3 insulated concrete tanks, Fibreglass top
• €35,000 Initial investment
• 50kw Heat output

16. Planning a Community Digester – Farmer Aspects
Farm Operation
• Facility to treat waste materials
• Access to enhanced fertilisers
• Reduction in pathogens and
weed seeds
• Greening agricultural practice
Community Aspects
• Positive benefits of reduction of
farm odours
• Lowering carbon footprint
• Who will provide a site for the
digester?
• Ownership
• Green Community
• Potential for district heating

17. Planning a Community Digester – Non Farmer
Residents
• Greening the Commmunity
• Ownership sharing?
• Positive benefits of reduction of
farm odours
• Outlet for food and garden waste
• Access to excellent fertiliser for DIY
gardener
• Potential for district heating
Local Food Companies
• Outlet for food processing waste
and surplus stock
• Reduction of carbon footprint
• Embedding company to the
community
• Potential for heating and/or
electricity

18. What must be done?
• Survey of available feedstocks (Community Meetings)
• Identify a suitable site
• Identify suitable uses for the gas in terms of heat, electricity or gas
upgrading
• Community Meetings!
• Financial feasibility
• Regulatory aspects (planning, waste licencing etc..)
• Community Meetings!!
• Financing the project and ownership
• Community Meetings!!!

19. Ss
Biogas / Anaerobic Digestion for the Community
Noel Gavigan
Technical Executive
Irish BioEnergy Association
noelgavigan@irbea.ie