Food Waste Helps Power Wastewater Plant

Published on
by
the San Francisco Chronicle

Food Waste Helps Power Wastewater Plant

by
Kelly Zito

Wastewater plant workers fill a tank with food scraps to be converted into methane gas. (Lance Iversen / The Chronicle)

Inside hulking white tanks near the Oakland foot of the Bay Bridge, some of your pizza crusts, kung pao chicken and orange peels are cleaning the wastewater from 650,000 households in Contra Costa and Alameda counties.

Sort of.

Under an innovative program touted as the first of its kind in the nation, the East Bay Municipal Utility District collects about 100 tons of food scraps from restaurants and grocery stores each week, speeds up the decomposition process, and uses the resulting methane gases to fuel the energy-hungry pumps and pipelines at its 49-acre wastewater treatment plant. Leftover scraps are turned into compost.

It's a rough, messy process, and educating waiters and grocery clerks about separating chopsticks and plastic cases from the food scraps is a challenge. But the utility is pleased with the program's progress. It cuts greenhouse gas emissions, keeps refuse out of local landfills and may eventually be profitable.

If the utility district hits its long-term goal of processing 100 to 150 tons of food waste each day, district officials hope to begin selling a steady, sizable amount of renewable energy to Pacific Gas and Electric Co.

"This is a great opportunity, especially since our primary focus is public health and environment," said David Williams, director of wastewater at the utility. "Right now, we take a lot of carbon out of the ground and put it out into the air. In this case you're taking carbon that's already here and getting the energy out of it. That's a great thing."

The U.S. Environmental Protection Agency, which awarded EBMUD $50,000 to study the food waste program, said it is the first wastewater system of its kind in the country. Williams expects more utilities to follow, given that treating wastewater consumes a huge amount of energy and that many facilities already have much of the necessary equipment.

For EBMUD, the program grew out of an effort to broaden the kinds of fuels that power the plant. The Oakland operation, like many others in the Bay Area and United States, separates solids from sewage. It then captures the methane gases released while the solids stabilize in giant digester tanks. Even before the utility elected to add food scraps to the mix, the plant was already generating about 2.5 megawatts of power, Williams said.

In 2000, agency managers found themselves sitting on excess capacity after the closure of several East Bay canneries - operations that generate loads of wastewater. So officials began collecting fats, oils, greases and other organic materials from animal processing centers. The federal grant several years later enabled the agency to finally include food leftovers. After spending about $5 million on special pipes and screening gear, the district got on the phone with haulers in San Francisco and Contra Costa County that were willing to deliver only food waste.

These days, the plant can generate upward of 6 megawatts of power.

On a recent weekday, a 20-ton truck showed up at the Oakland plant with several reeking tons of ground-up vegetable peels, bones and breads. After the truck dumped the slush into an underground trough, large hanging hooks snagged several piles of cloths and plastic bags that had ended up with the food slurry.

Shift supervisor Joe Augustine motioned to one pile - "Check out that bright blue rag."

The fight to keep the rag out of the food waste begins several miles away, at places like Bakesale Betty in Oakland's Temescal District. There, bakery owner Alison Barakat said it takes constant monitoring to make sure the trash, recycling and food go into the appropriate bins.

"It does take a commitment, absolutely, because people forget and put something in the wrong can," said Barakat, whose food waste goes to the EBMUD plant. "But we think it's worth it."

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