Biogas means a gas produced by the anaerobic digestion or fermentation of organic matter in an environment without oxygen . The organic matter can be manure , sewage sludge , municipal solid waste , biodegradable waste or any other biodegradable feedstock . Biogas is produced by anaerobic digestion or fermentation of biodegradable materials such as biomass , manure , sewage , municipal waste , green waste , plant material and energy crops .