Turning food scraps into energy

Bay Area utility program believed first of its kind in U.S.

OAKLAND, Calif. - Leftovers from San Francisco Bay Area restaurants may soon help power the region.

The East Bay Municipal Utility District has created a program, believed to be the first of its kind in the United States, to generate electricity from the methane gas produced by food decomposition.

Engineers have been testing and refining the process since the U.S. Environmental Protection Agency gave the utility $50,000 in 2006 to study it, and they plan to sell energy to the grid beginning next year.

"The program could yield a significant amount of energy, long term," said John Hake, an associate civil engineer with the utility district. "It's no silver bullet, but it could be one part of a portfolio of renewable energy sources."

Food scraps are collected from about 2,300 restaurants and grocery stores in the Bay Area and taken to the utility district's wastewater treatment plant in Oakland, where they are pumped into large tanks full of microbes that speed up decomposition. The food releases methane gas, which is used to generate electricity.

The utility now powers its wastewater treatment plant, which serves about 650,000 homes in Alameda and Contra Costa Counties, by processing many kinds of waste, including food scraps.

By the end of 2010, the utility expects to double its capacity to create power, said David Williams, director of wastewater, enabling it to sell more than five megawatts of energy to Pacific Gas & Electric Co. The utility eventually hopes about one megawatt will come from food scraps, powering 1,300 homes, Williams said.

It would need to process about 100 tons of food per day to reach that goal, he said. Now, the plant processes about 100 tons per week.

Contaminants such as forks and plastic bags, which often get mixed into the food scraps, have caused the most trouble for the food-waste program, Williams said.