San Francisco pioneers food scraps to fuel method
July 15, 2009
by Bryan Salvage
SAN FRANCISCO — The East Bay Municipal Utility District (E.B.M.U.D.), with help from a U.S. Environmental Protection Agency grant, is pioneering a method of generating renewable energy using food scraps. E.B.M.U.D. takes food waste from San Francisco and Contra Costa County restaurants and commercial food processors and uses them to produce green, renewable energy through anaerobic digestion.
This process decreases food waste sent to landfills and reduces greenhouse gas emissions.
Due to San Francisco’s recently signed mandatory composting law -- the first in the nation -- residents and businesses will begin increasing their composting efforts or finding new and unique ways to divert food scraps from being sent to the landfill. E.B.M.U.D.’s anaerobic digester, in operation since 2004, is leading the way, and currently processes 90 tons a week of post-consumer food waste from restaurants and food-processing facilities. The facility plans on increasing the amount of food waste processed to its maximum capacity of 200 tons a day.
Here’s how the process works. Food waste is separated for disposal and pick up. Waste is broken down in large containers called anaerobic digesters at the E.B.M.U.D.’s main wastewater treatment plant. Bacteria inside the digester decompose the food. The digester captures the biogas and the methane from the biogas powers the treatment plant. Material remaining after the digestion process can be composted and used as a natural fertilizer to help grow food.
More than 30 million tons of food wastes are sent to U.S. landfills annually. Food waste is the second-largest category of municipal solid waste in the U.S., accounting for 18% of the waste stream. Less than 3% of food waste in the U.S. is diverted from landfills.
If 50% of food waste in the U.S. was anaerobically digested, enough electricity would be generated to power approximately 2.5 million homes for a year. Landfills are the second-largest source of human-caused methane in the U.S., and food waste contributes significantly to landfill methane production, according to the E.P.A.
Click here to watch the video on the East Bay Utility District’s anaerobic digester.