University Project Turns Bay Area Table Scraps into Fuels
More than five million tons of food scraps go into California landfills each year. Now a research and technology demonstration facility at the University of California-Davis can turn tons of table scraps from Bay Area restaurants into clean, renewable energy.
The Biogas Energy Project will process eight tons of leftovers weekly from premier restaurants such as San Francisco’s Slanted Door, Jardiniere, Scoma’s, Boulevard, and Zuni Cafe, and Oakland’s Oliveto and Scott’s Seafood.
Each ton of scraps can produce enough energy to provide electricity to power 10 average California homes for one day. Later as much as eight tons of leftovers will go to the project every day.
The Biogas Energy Project is the first large-scale demonstration in the United States of a new technology developed in the last eight years by Ruihong Zhang, a UC Davis professor of biological and agricultural engineering. The technology, called an “anaerobic phased solids digester,” has been licensed from the university and adapted for commercial use by Onsite Power Systems, Inc.
The project’s goal is to divert organic matter such as food waste and yard clippings away from landfills and into the energy grid. That reduces greenhouse gas emissions from landfills and turns trash into a substantial source of clean power. Energy can be harvested from about half the waste material that California currently sends to landfills.
Zhang’s system processes a wider variety of wastes than other anaerobic digesters, most of which are in use at municipal wastewater treatment plants and livestock farms. It works faster, turning waste into energy in half the time of other digesters.
The system produces two clean energy gases–hydrogen and methane. Other digesters produce only methane. The gases can be burned to produce electricity and heat, or to propel cars, trucks, and buses.
Zhang has proved in the laboratory on a small scale that in anaerobic, or oxygen-free, conditions, naturally occurring bacteria can quickly convert food and green wastes into hydrogen and methane gases.
Now the challenge is to make the gases in consistently high-quality and large volumes over the long term. Onsite Power Systems has invested almost $2 million in helping Zhang refine the technology and prepare it for transfer to the commercial market.
Norcal Waste Systems of San Francisco supplies the waste for the project because it already collects restaurant leftovers for its composting operation near Vacaville. Every day, Norcal collects 300 tons of food scraps from 2,000 restaurants in San Francisco and 150 more restaurants in Oakland.