Biogas typically refers to a (biofuel) gas produced by the anaerobic digestion or fermentation of organic matter including manure, sewage sludge, municipal solid waste, biodegradable waste or any other biodegradable feedstock, under anaerobic conditions. Depending on where it is produced, biogas is also called swamp gas, marsh gas, landfill gas or digester gas.

            Luebeck MBT plant, Germany (Haase Energietechnik Gruppe)

The composition of biogas varies depending upon the origin of the anaerobic digestion process. Landfill gas typically has methane concentrations around 50%. Advanced waste treatment technologies can produce biogas with 55-75% CH4. The other main component of biogas is CO2.

Biogas can burned directly for cooking, heating, lighting, process heat, absorption refrigeration, and generating electricity. It can however also be used as a vehicle fuel or for grid injection. In the latter cases, the biogas like SNG will have to be upgraded first to obtain an acceptable gas quality.