BioGas

Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. Organic waste such as dead plant and animal material, animal dung, and kitchen waste can be converted into a gaseous fuel called biogas. Biogas originates from biogenic material and is a type of biofuel.

In 2003, the United States consumed 147 trillion BTU of energy from "landfill gas", about 0.6% of the total U.S. natural gas consumption.[27] Methane biogas derived from cow manure is also being tested in the U.S. According to a 2008 study, collected by the Science and Children magazine, methane biogas from cow manure would be sufficient to produce 100 billion kilowatt hours enough to power millions of homes across America. Furthermore, methane biogas has been tested to prove that it can reduce 99 million metric tons of greenhouse gas emissions or about 4% of the greenhouse gases produced by the United States.

http://en.wikipedia.org/wiki/Biogas

Mainly Methane and Carbon Dioxide

Can be a Renewable Energy

http://en.wikipedia.org/wiki/Anaerobic_digestion

http://www.miiu.org/wiki/Anaerobic_Digester - home use

• John Robb: T H Culhane's system - usually for Third World, but: You can do this yourself (above ground) or with some neighbors (below ground) or you can contract for it. If the community has the willpower, a municipal sewage system can use large biogas digesters to generate electricity — likely more than enough to operate a sewage treatment facility and power some community buildings. (Resilient Community)

http://en.wikipedia.org/wiki/Mesophilic_digester

GobarGas http://www.miiu.org/wiki/Gobar_gas