From www.global-greenhouse-warming.com:
The harvesting of biogas is an important role of waste management because methane is a greenhouse gas with a greater global warming potential than carbon dioxide. Landfill gas can be burned to produce electricity, usually with a reciprocating engine or micro-turbine. The gas is often used in a cogeneration arrangement, to generate electricity and use waste heat to warm the digesters or to heat buildings. Excess electricity can be sold to electricity suppliers. Electricity produced by anaerobic digesters is considered to be green energy and can attract subsidies.
…
Read the complete article: May 1, Landfill Gas