Biogas Systems
Anaerobic Digestion is Very Useful
Image courtesy of Community Composting Network
Anaerobic Digestion in a Diagram
Image courtesy of Sustainable Sanitation and Water Management (SSWM)
What is Biogas?
• It is similar to natural gas.
• It is 50-70% methane.
• The remainder is carbon dioxide and traces of
hydrogen sulfide and ammonia.
• Methane is the important product. It can be
burned as fuel, just like natural gas.
What are the benefits of Biogas?
•
•
•
•
Sanitation and hygiene
Fuel and electricity
Reduces indoor air pollution
Reduces deforestation and cuts CO2
emissions.
• Fertilizer
Image courtesy of SKG Sangha/The Ashden Awards
Small scale biogas digesters
Image courtesy of Dr.-Ing. Arquitecta Joana Forte – Nepal 2011
Image courtesy of the Pace Project
What do you put in?
Images courtesy of Practical Action
How much biogas is produced?
• It depends on what you put in
Image courtesy of Smith (DFID) 10
Human Waste
C/N Ratio
Duck dropping
Human Excreta
Chicken dropping
Goat dung
Pig dung
Sheep dung
Cow/Buffalo dung 24
Water Hyacinth
Elephant dung
Maize stalk
Rice straw
Wheat straw
Saw dust
200
8
8
10
12
18
19
25
43
60
70
90
Hydraulic Retention Time
Human waste
55 days
Cow/Buffalo Dung 45 days
Low C/N ratio  Low gas production
(Need 3 times the plant size to produce
same amt of biogas as cow dung)
High HRT  Less amount required
for feeding into plant
WASH solution – HYBRID PLANT
Cow dung for biogas production
Human waste for sanitation
How much biogas is produced?
Size of Digester
4m3
6m3
8m3
10m3
15m3
Daily Cow Dung
Required (kg)
Gas Production
(m3/day)
Stove usage
(hrs/day)
32
48
64
80
120
1.28
1.92
2.56
3.20
4.80
3-4
5-6
6-8
8-10
13-15
What does this mean?
Image Courtesy of Practical Action
What does this mean?
• Rural Scale: dung from 2-4 cows (or 5-10 pigs)
can produce enough gas for all a family’s
cooking, and sometimes their lighting, too.
• Urban Scale: A family or community using just
their own food waste can replace between
25% and 50% of their cooking fuel.
• Large-scale: electricity can be generated for
many families or whole communities.
Variations on Biogas Installations
• The following slides will demonstrate the wide
variety of biogas systems currently being used
around the world.
• The major variables are:
1. Size of the installation.
2. Materials used to create the installation.
3. Amount of pressure created within the
system.
Fixed Dome Biogas Plant
Sano Khokana, Kathmandu Valley,
Lalitpur, Nepal
Images courtesy of
Prakash Chandra
Amatya
Floating Dome Biogas Plant
Images courtesy of Practical Action and Ashden Awards
Image courtesy of Ashden Awards
BIOTECH, India
• In households and institutions, biogas plants handle kitchen
waste and sometimes have toilets connected
– Biogas is used for cooking, displacing about 50% of LPG use.
• Larger systems used at markets, municipal sites, schools and
hostels generate enough electricity for lighting
Images courtesy of Ashden Awards
Loowatt
A new customizable toilet that allows the toilet
owner to also have an energy source
Image courtesy of Loowatt
Flexible Balloon Biogas Plant
Images courtesy of SSWM
Low-Cost Polyethylene Tube Digester
Images courtesy of Energypedia
Assess Community Need
If you are working with a community that has a
waste disposal problem, biogas may be a helpful
solution. Work with your community to determine:
1. What types of waste are is the community
producing?
2. What quantities of this waste is the community
producing?
3. Is the community interested in transforming this
waste into useful energy and fertilizer?