U.S. scientists have developed a fuel cell capable of converting 13 percent of the energy found in sewage into electricity, a process that its developers say could also more efficiently treat municipal wastewater. In a report released at the annual meeting of the American Chemical Society, researchers at the J. Craig Venter Institute describe a so-called microbial fuel cell that uses naturally existing microbes that produce electrons and protons as they metabolize the organic waste. The electrons are collected by an anode in one container, while the protons pass through a permeable membrane to a cathode in a separate container; the voltage between the electrodes produces an electric current. The process is also capable of removing about 97 percent of the organic matter, the scientists say. While that would not be clean enough for re-use as drinking water, the researchers say the results suggest the technology could one day emerge a wastewater treatment alternative. Treatment of wastewater and sewage currently consumes about 2 percent of the U.S. energy supply, at a cost of about $25 billion annually.