Comment: There are methane plants being built

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There are methane plants being built

that are composting vegetation from entire cities; London Ontario is one I know of. They get enough methane to run their fleet of big waste management trucks and use the compost for fertilizer. You can also use composting toilets and use a method to collect the gas for energy.
http://www.lfpress.com/2012/12/17/harnessing-methane-gas-for...

http://www.ehow.com/how_8642626_capture-gas-septic-system-en...

http://www.youtube.com/watch?v=wVkMmUP3ei0