OXNARD, Calif. — Gills Onions here, the nation's largest fresh onion processor, used to pay a lot of money to get rid of onion waste. Now the waste is being used to produce energy.
Since last summer, Gills has been mixing the onion waste with bacteria in a special anaerobic digester, producing methane gas. The gas is transferred to two 300-kilowatt fuel cells, from FuelCell Energy, Danbury, Conn., which convert it into electricity used to power Gills' operations and into heat to warm the digester.
Since the carbon dioxide emitted by the fuel cell is equal to the carbon dioxide absorbed from the air by the onions, the whole process is carbon neutral. Financially, the system has been supported by energy rebates from the state of California.
A similar process is used by Sierra Nevada Brewing, Chico, Calif. In fact, any operation that produces food waste could adopt this process, including supermarkets.
“We've talked to supermarkets about installing fuel cells,” said Tony Leo, vice president of application and OEM engineering at FuelCell Energy. A supermarket installation would probably use a steady supply of natural gas from a utility, he noted. “We would have to work out a waste profile to use some waste materials for power,” he noted.