The city of San Antonio (Texas, United States) recently announced plans to convert 140,000 tons per year of its ‘biosolids” (solid component of domestic sewage) into biogas (methane and carbon dioxide). Biogas is produced by the fermentation of organic waste (like domestic sewage) by microorganisms, in the absence of oxygen. Basically, the process involves placing the domestic sewage in an air-free reaction tank, added with acclimatized anaerobic microorganisms and then allowed to ferment. The methane produced will be converted to natural gas and used as fuel for its power plants. According to Reuters, “It would be the first U.S. city to harvest methane gas from human waste on a commercial scale and turning it into clean-burning fuel”. The city approved a deal with Massachusetts-based Ameresco Inc. to convert the city’s sewage into natural gas. The facility would generate about 1.5 million cubic feet of the gas per day. According to Steve Clouse, chief operating officer of the city’s water system, “90 percent of materials flushed down the toilets and sinks of San Antonio will be recycled”..