Anaerobic digestion is widely used as a source of renewable energy. The process produces a biogas, comprising of methane and carbon dioxide. This biogas can be used directly as cooking fuel, in combined heat and power gas engines or upgraded to natural gas quality biomethane. The utilisation of biogas as a fuel helps to replace fossil fuels.
EPA estimates that 157 digester projects are operating on commercial scale livestock
facilities nationwide - July 2010.