Biogas is a gas composed principally of methane and carbon dioxide produced by anaerobic digestion of biomass. Due to the method of obtaining it the following gases are enumerated in statistical reporting: - 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.