Human beings have converted food into energy since before they walked upright, so it stands to reason that some day a public utility would do the same. But who knew an East Bay agency would help pioneer the effort?
The Food Waste Recycling Project, launched by the Central Contra Costa Solid Waste Authority as a pilot program several years ago in partnership with Allied Waste and EBMUD, turns food scraps from selected restaurants and school cafeterias into electricity. The program is about to expand its scope.
Paul Morsen, executive director of the waste authority, said the idea smacked him in the head one day when he was searching for ways to comply with a state law requiring 50 percent of all waste be diverted from landfills.
"About 20 percent of the waste we handle is food waste," he said. "The largest portion of that is from restaurants and such."
As with most things, the devil was in the details.
EBMUD had already experimented with anaerobic digestion of food discards, breaking them down into methane and carbon dioxide to power generators, but the food had to be separated from wrappers and trash, which meant additional cost.
"If we could get the restaurants to do that," Morsen said, "we could have a cost-effective program."
With some gentle prodding, his staff initially enlisted 55 participating restaurants, which were given instructions, special plastic bags and food-only waste bins. Pickups were as often as three days a week. Before long, another 50 restaurants joined; then more. Only logistics kept the program from growing.
EBMUD's process requires that food scraps be no larger than two inches square; for that, waste was processed in a grinder in Milpitas, but it was 40 miles away. That's when CCCSWA and Allied worked to get a similar machine -- the Morbark 900 tub grinder -- installed much closer, at the Martinez transfer station. It makes big pieces into what Morsen describes as the "slurry" that's trucked to EBMUD's Oakland facility.
Sophia Skoda, an EBMUD senior civil engineer, said the waste is dumped into underground "digester" tanks that are partially filled with water to make what she calls a "milkshake." She described the 20-day process that follows as a lot like what happens in your stomach.
"Everything is kept at a temperature that's perfect for methanogens to live. Those are microorganisms that break down organic materials. As that happens, they give off methane gas and CO2, which we clean up and put in turbines to create electricity."
As much as 80 percent of food waste is converted into energy, which EBMUD uses internally or sells back to the power grid. The remaining waste resembles compost, which is used for landfill covering or farming applications for nonfood crops. It can't be used on edible crops because human waste now is included in the process, a practice that will end when food collections increase.
Skoda said EBMUD hopes to process as much as 200 tons per day -- enough to power 2,400 homes -- when more waste districts join the program. Contra Costa currently collects about five tons a day, but that will increase as it adds up to 100 more restaurants. San Francisco also participates in the program.
"As far as I know," Skoda said, "we're the only folks in the country who are doing this."
Morsen doesn't try to hide his satisfaction.
"In the world of garbage," he said, "this is a very sexy thing."
Contact Tom Barnidge at firstname.lastname@example.org.