Farmers can produce biogas from manure from their cattle by using anaerobic digesters. Biogas environments include wastewater digesters, landfills, and animal feeding operations (covered livestock lagoons). Digesters processing dedicated energy crops can achieve high levels of degradation and biogas production. Anaerobic digesters were originally designed for operation using sewage sludge and manures. The cake can also be used as feed in digesters and gasifiers to produce biogas. Portland is considering implementing anaerobic digesters and plasma gasification that would efficiently decompose garbage. California has 242 sewage wastewater treatment plants, 74 of which have installed anaerobic digesters. Electricity produced by anaerobic digesters is considered to be renewable energy and may attract subsidies. Farm methane digesters (or "Farm Power"). The egg-shaped structures house the plant's sludge digesters. The following is a partial list of types of anaerobic digesters. One use of vinasse is in thermophilic digesters. Therefore, many digesters operate with codigestion of two or more types of feedstock. In batch tunnel digesters, the feedstock is deposited in tunnel-like chambers with a gas-tight door. Chemical pulp is produced by combining wood chips and chemicals in large vessels called digesters.