Seven times more efficient than a human-designed anaerobic digester, a cow’s stomach provides the ideal conditions – anaerobic conditions, constant temperature, regular addition of finely chopped food, neutral pH, and effective mixing - for the fermentation of organic materials that produces biogas. The basic process in anaerobic digesters consists of mixing organic materials to form a highly liquid (3-10% solids) slurry which is heated for pasteurization (70o C) or sterilization (130o C). Afterwards, the slurry is pumped to the fermentation tank for 12-20 days then to a storage tank where the fermented solids are removed. The biogas generated ranges from 60 to 75% methane, depending on inputs and temperature, and requires drying and removal of sulfur dioxide before it is used to generate electricity or heat. In addition to producing energy from a renewable resource, digesters produce fermented solids which have little odor and can be used as a soil amendment. Although anaerobic digesters require significant up front costs, they have the potential to reduce energy costs and produce income through the sale of green electricity, methane, fermented solids and carbon dioxide credits.