Biogas: A gas composed principally of methane and carbon dioxide produced by anaerobic digestion of biomass, comprising: -Landfill gas, formed by the digestion of landfilled wastes. -Sewage sludge gas, produced from the anaerobic fermentation of sewage sludge. -Other biogas, such as biogas produced from the anaerobic fermentation of animal slurries and of wastes in abattoirs, breweries and other agro-food industries.