Biogas digestion is a process where bacteria breaks down organic waste in an oxygen-free environment to produce biogas, a mixture of methane and carbon dioxide. A digester is used to contain this process, and can be a vessel or container to hold the waste, or cover an area already producing biogas like a landfill. Digesters have improved technology and provide environmental and financial benefits like managing odors from manure. The biogas produced can be used to generate electricity or heat. Different types of digesters exist like covered lagoons or landfill gas collection systems. Concerns include potential releases of hazardous gases, but biogas digestion overall reduces greenhouse gases and provides renewable energy.

1. Biogas Digestion
by
NARESH THAKUR

2. What is Biogas Digestion?
• Biogas Digestion is the process of taking
biogas to produce electricity, heat, or hot
water
• Biogas means a gas formed by carbon
dioxide and methane from breakdown of
organic materials such as manure.

3. What is a Digester?
• Digester is a vessel or container where the
biogas process takes place. Bacteria breaks
down manure or other waste products to
create biogas. Products may be fed into
the chamber such as manure or the
container could be used to cover a place
that is already giving off biogas such as a
swamp or a landfill.

4. Reasons of Interest in Biogas
Anaerobic Digester systems
• Improved Technology in systems has led
to reliability
• Good way to manage manure given the
odor and environmental concerns
associated with manure
• Government has subsidized programs
for systems
• Potential to sell credits to utilities and
utilities continue interest in green
energy

5. Biogas Process

6. Design of a Digester

7. How Digester Works
• Temperature must be kept between 65 degrees
and 150 degrees
• 4 Types of bacteria breakdown the waste
– Hydrolytic breaks organic material to simple
sugar and amino acids
– Fermentative then converts to organic acids
– Acidogenic convert to carbon dioxide,
acetate, and hydrogen
– Methanogenic produces biogas

8. Combined Heat and Power
• Also known as cogeneration
• Using the heated water for other
purposes such as heating buildings or
creating additional energy

10. Sources of Biogas
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Wetlands
Sewage Sludge
Landfills
Plant Material
Animal Waste

11. TYPES OF BIOGAS DIGESTER
SYSTEMS

12. • fixed film digester – “a tank
designed as part of a manure
management system to handle
manure up to 3 percent solids. The
digester is temperature controlled
and a media is placed inside the
digester. This design allows the
microbial populations to attach to
the media and grow as a biofilm
(fixed film), thus preventing the
microbes from being removed with
the effluent”

13. • temperature-phased anaerobic
digester (TPAD) – “two tanks
designed as part of a manure
management system. The digesters
are heated, the first digester in the
thermophilic temperature range
and the second digester in the
mesophilic temperature range. This
will maximize biological activity for
the destruction of volatile solids,
methane production and odor
reduction.”

14. • covered lagoon digester – “an anaerobic
lagoon is commonly used when manure
has less than 2 percent solids.
Decomposition of the manure occurs,
methane is produced and effluent odor is
reduced. The lagoon is covered with a
gas-tight cover to capture the biogas.”

15. • A landfill gas-to-energy – “consists of a
series of wells drilled into the landfill. A
piping system connects the wells and
collects the gas. Dryers remove moisture
from the gas, and filters remove impurities.
The gas typically fuels an engine-generator
set or gas turbine to produce electricity. The
gas also can fuel a boiler to produce heat or
steam. Further gas cleanup improves biogas
to pipeline quality, the equivalent of natural
gas. Reforming the gas to hydrogen would
make possible the production of electricity
using fuel cell technology.”

16. Financial Incentives
• Since 2003 USDA has awarded 37
million to anaerobic digestion systems

17. Benefits and Concerns

18. Benefits of Biogas Digester
Systems
• Odor Reduction by using raw manure
• If Ammonia, a by-product of process,
is captured can be used to help plant
growth by injecting it into the ground
• Reduction of Electricity for Farms
• Carbon Dioxide generated from
biogas digester systems creates less
greenhouse gas then methane gas
used in initial process

19. Biogas Digester System
Concerns
• Releases Nitrogen and ammonia into the
atmosphere both of which hazardous
• Can release Hydrogen Sulfide a very toxic
gas
• Methane released can create explosive
atmosphere
• Should raw materials get into water supply
can contaminate the water
• Transportation is of a concern because
methane is explosive although new
technology may allow it to be stored in
powder form

20. Other Countries use of Biogas
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Nepal
Africa
Ecuador
Sweden

21. Notes-Citations
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Slide 3-http://www.biogas.psu.edu/terminology.html
Slide 4-http://www.biogas.psu.edu/basics.html
Slide 5-http://www.energyrevolution.co.za/biogas/biogas-history
Slide 6- http://www.epa.gov/agstar/documents/2010_digester_update.pdf
Slide 7-http://www.hydropur.be/anglais/Assainissement%20et%20biogaz /biogas
%20principle.html
Slide 8-http://www.clearhorizonsllc.com/html/products/diagram.htm
Slide 9-http://www.oregon.gov/ENERGY/RENEW/Biomass/biogas.shtml
Slide 10-http://www.epa.gov/chp/basic/index.html
Slide 11-http://www.epa.gov/chp/basic/index.html
Slide 12- Various sources see
Slide 13-No need for citation

22. Notes-Citations Continued
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Slide 14-http://www.epa.gov/agstar/documents/2010_digester_update.pdf
Slide 15-http://www.biogas.psu.edu/terminology.html
Slide 16-http://www.biogas.psu.edu/terminology.html
Slide 17-http://www.biogas.psu.edu/terminology.html
Slide 18-http://www.biogas.psu.edu/terminology.html
Slide 19 -http://www.oregon.gov/ENERGY/RENEW/Biomass/biogas.shtml#
Landfill_Gas
Slide 20- No Citation needed
Slide-21- SO2 EMISSION LIMIT FOR UNITS BURNING BIOGAS ADDED TO NSPS FOR
STATIONARY COMBUSTION TURBINES (19 NO. 4 Air Pollution Consultant 2.13)
Slide 22-http://www.epa.gov/agstar/documents/2010_digester_update.pdf
Slide 23- http://www.epa.gov/agstar/documents/nydairy2003.pdf

23. Notes-Citations Continued
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Slide 24-No citation needed
Slide 25-http://animalagteam.msu.edu/Portals/0/anaerobic.pdf
Slide 26-http://www.biogas.psu.edu/Safety.html
Slide 27-http://www.nytimes.com/2008/09/24/business/businessspecial2/
24farmers.html
Slide 28-No need for a citation
Slide 29-http://www.bspnepal.org.np/achievements
Slide 30-http://www.bspnepal.org.np/target-group
Slide 31 – Borders and Environment by Andrew P. Morriss and E. Roger Meiners 39
Envtl. L. 141)
Slide 32-http://sgp.undp.org/download/SGPCaseStudiesBook.complete.pdf
Slide 33-http://sgp.undp.org/download/SGPCaseStudiesBook.complete.pdf
Slide 34-http://news.bbc.co.uk/2/hi/science/nature/4373440.stm
Slide 35-http://tonto.eia.doe.gov/kids/energy.cfm?page=biomass_home-basicsk.cfm