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Food Waste Powers New California Energy Plant

  • Tamara Keith

A new power plant went 'on line' on the University of California Davis campus last month. But there's no coal or natural gas fueling its generators. This plant is powered by organic waste including food -- table scraps from San Francisco Bay Area restaurants.

At Boulevard, an upscale restaurant on the San Francisco waterfront, diners lunch on sea scallops, paella and pan roasted halibut, among other options. Back in the kitchen, cooks and waiters are careful to keep the food scraps separate from the rest of the trash.

The food scraps from this restaurant and 2,000 others in the area are already being collected to turn into compost. But now some of that waste, about 8 metric tons a week, is going to a new biogas power plant at UC Davis. Boulevard chef Tim Quaintance says he's pleased that his leftovers aren't just going to a landfill. "It's nice that in the past things that have basically been thrown away are now actually being used and with this technology really contributing to reducing our reliance on fossil fuels."

The experimental food-fueled power plant is known as the Biogas Energy Project. With its four large steel tanks and 22-kilowatt generator, it is the first real-world demonstration of a technique called anaerobic phased solids digestion. UC Davis Professor of Biological and Agricultural Engineering Ruihong Zhang developed the technology. As she shovels food waste into the plant, she notes, "What you see here is 20,000 times larger than the reactor system I use for laboratory testing."

Turning leftovers into power may sound like something out of a science fiction movie, but Dave Konwinski says it's real. He's head of Onsite Power Systems Incorporated, which licensed the technology and will operate the on-campus plant. "Every ton of collected food waste will provide enough either electrical or thermal energy to run an average of 10 California homes," he explains. He sees this test plant as the first step to commercializing biogas power plants.

Here's how it works. The food waste from the Bay Area - as well as grass clippings and other would-be-trash - go into a sealed tank where bacteria break everything down into water and organic acids, essentially speeding up the natural process of decay. When that's done, the organic acids are pumped into another tank where different bacteria convert the soup into methane gas. Konwinski says that's where the power comes from. "Biogas can be used in a generator, we have a generator we'll be running here...and we're looking at taking the gas and converting it into vehicle fuels."

If this technology proves to be commercially viable, and gets widespread acceptance, the results could be huge. Not only does it promise to keep tons of garbage out of landfills, it could reduce greenhouse gas emissions, and diminish America's reliance on foreign oil. Suddenly leaving a little broccoli on your plate doesn't seem like such a bad thing.

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