Biogas

Biogas is a gas produced by the digestion in an oxygen free (anaerobic digestion) or fermentation of organic matter. The organic matter can be manure, sewage, municipal waste, compost, food waste or any other biodegradable raw material. Biogas is mainly methane and carbon dioxide. Depending on where it is produced, biogas is also called:

• swamp gas
• marsh gas
• landfill gas
• digester gas

Biogas can be used as a vehicle fuel or to generate electricity. It can also be burned directly for cooking, heating, lighting, process heat and absorption refrigeration.

Biogas and anaerobic digestion

See the main article: anaerobic digestion

Anaerobic digestion is much used to make biogas from biodegradable waste because valuable fuel can be produced while destroying disease-causing pathogens and reducing the volume of disposed waste products. The methane in bio gas burns more cleanly than coal, and produces more energy with less emissions of carbon dioxide. The harvesting of bio gas is an important role of waste management because methane is a greenhouse gas with a greater global warming potential than carbon dioxide. The carbon in bio gas was generally recently extracted from the atmosphere by photosynthetic plants, so releasing it back into the atmosphere adds less total atmospheric carbon than the burning of fossil fuels.

Biogas typical composition range

The composition of biogas varies depending on how it is made. Landfill gas typically has methane concentrations around 50%. Advanced waste treatment technologies can produce biogas with 55-75%CH₄.

Biogas composition

Matter	%
Methane, CH4	50-75
Carbon dioxide, CO2	25-50
Nitrogen, N2	0-10*
Hydrogen, H2	0-1
Hydrogen sulphide, H2S	0-3
Oxygen, O2	0-2*

• often 5% of air is introduced to get rid of sulfur microbiologically

Related pages

• Producer gas

Other websites

• AGORES - Biogas Biofuel Lille Archived 2006-10-06 at the Wayback Machine (PDF)
• AGORES - Biogas Biofuel Stockholm Archived 2006-11-16 at the Wayback Machine (PDF)
• University of Adelaide - An Introduction to Biogas
• Biogas in Rural Costa Rica Archived 2007-03-27 at the Wayback Machine
• Solid Waste Association of North America
• Landfill Gas Symposium Archived 2012-07-09 at the Wayback Machine