Future applications of digester gas may include electric power production from gas turbines or fuel cells. Digester gas can substitute for natural gas or propane in space heaters, refrigeration equipment, cooking stoves or other equipment. Compressed digester gas can be used as an alternative transportation fuel. Wastewater Treatment Municipal sewage contains biomass solids. Many wastewater treatment plants use anaerobic digestion to reduce the volume of the biomass solids in sewage.
Anaerobic digestion stabilizes sewage sludge and destroys harmful bacteria.
Most wastewater treatment plants that use anaerobic digesters burn the gas for heat to maintain digester temperatures and to heat building space. Unused gas is burned off as waste but could be used for fuel in an engine-generator or fuel cell to produce electric power. A fuel cell at the Columbia Boulevard Wastewater Treatment Plant in Portland, Oregon, converts digester gas into electricity. The fuel cell began producing power in July 1999. The Columbia Boulevard fuel cell will produce an estimated 1,500,000 kilowatt-hours of electricity each year.