From waste to wattage | July 11, 2008 | Danville Express | |

Danville Express

Newsfront - July 11, 2008

From waste to wattage

Pilot program will test way to turn food waste into renewable energy

by Meghan Neal


ver wonder what happens to all those cucumber peels and pepper seeds discarded from restaurant food prep? Or the loaves of stale bread from the grocery store?

Imagine: If all goes according to plan, this food waste could be converted into electricity and used to power Bay Area homes within the next couple years.

East Bay Municipal Utility District has teamed up with Central Contra Costa Solid Waste Authority, which serves Danville and Alamo, in a groundbreaking pilot program that will save food trash and convert it into renewable energy.

"This is a very green program that we're developing," said Bart Carr, program manager for the waste authority.

The trial will begin this fall. About 50 restaurants and grocery stores, mainly in Walnut Creek, will be given green bins and biodegradable bags to gather food trash. Allied Waste of Contra Costa County, the third agency in the partnership, will collect about 100 tons of food per week, estimated Carr.

First the waste is pre-processed - essentially pureed into a pulp - to rid it of contaminants like forks or plastic containers. It's then sent to EBMUD where it's run through compost digesters and converted to methane, a biogas.

The methane is used to fuel engines, which drive generators that produce electricity, said EBMUD's Donald Gray, who invented the compost digester. One truckload of food waste - about 20 tons worth - can power 260 homes per day. If 100 tons were digested every day, five days a week, it could provide a year's worth of power to as many as 1,400 homes.

EBMUD already uses the system, which it is in the process of patenting, to power its own facility. When excess energy is generated, it's sold to PG&E to power households and businesses, likely within the Bay Area, said Gray.

"One of our goals was to become energy independent with renewable energy," he said. "We also are interested in reducing greenhouse gas, and that's also a benefit."

Another "green" aspect of the program is that it will divert tons of food waste from ending up in landfills, where the natural breakdown of the food causes large amounts of greenhouse gases to be emitted into the atmosphere.

If these gases aren't captured and used as renewable energy, they are absorbed into the atmosphere and can contribute to global warming.

The waste authority has set a goal to divert 50 percent of waste from landfills by recycling it. The agency hopes the groundbreaking experiment will help it meet that goal.

"For us it's just a very exciting program," said Carr. "If other communities ... can look at what we're doing and learn from it, and can start a similar program, then I think that would be great."

Central Contra Costa County is the first region to collect only pre-consumer foods - items that have not been served to customers and are therefore considered "clean" waste. San Francisco collects pre- and post-consumer food waste, which is more contaminated and more expensive to process. Program managers hope this extra step will make the digestion process more effective and ultimately more successful.

Training food service employees to separate out the clean food waste will be a key part of a successful program, said Carr. He also mentioned that the owner of The Peasant & the Pear on Hartz Avenue in Danville has expressed interest in participating if and when the program expands.

EBMUD is moving toward being a larger supplier of electricity, acquiring more engines to take in the copious amounts of biogas being produced. Gray estimated this could increase the number of households powered by the utility company from around 1,500 to 4,000.

Though he wasn't sure what that would mean for residents' electricity bills, he said it seemed logical that with more energy available locally, rates would go down.

The trial is expected to run for 18 months and cost roughly $172,000. If it proves successful, EBMUD and the waste authority hope to expand the program to their entire service areas.

"If this works out," said Gray, "then it really kind of opens the door for more of this happening."


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