The City of Millbrae, California, celebrated the completion of a treatment plant that will use restaurant kitchen grease as a renewable power source to treat the city’s wastewater. Such a reduction in demand for electric power from utilities will reduce carbon dioxide emissions by 1.2 million pounds annually, the same as planting about 170 acres of trees. It is also an energy savings for the city of $366,000…
The unique system, engineered and installed by Chevron Energy Solutions, will utilize 3,000 gallons of restaurant grease — the kind washed from grills and pans — delivered to the plant each day by grease hauling companies, which pay a city fee for disposals. Microorganisms in the plant’s digester tanks eat the grease and other organic matter, naturally producing methane gas to fuel the plant’s new 250-kilowatt microturbine cogenerator to produce electricity for treating the wastewater.
"This innovative project brings new meaning to the term ‘sustainable development,’ " said Millbrae Mayor Robert Gottschalk. "We’re taking an urban waste and turning it into an asset for the city and the environment."
"This project clearly demonstrates that cities can develop renewable energy economically, with multiple benefits to urban communities," said Jim Davis, president of Chevron Energy Solutions. "By looking at the entire waste stream in new ways, the City of Millbrae has cost effectively upgraded its facilities, reduced its operating costs, created new revenue and solved environmental challenges all at the same time."
Nationally, restaurants produce an average of 14 pounds of inedible grease per capita annually — a total of nearly 4.2 billion pounds each year in the United States alone. Much of this grease is disposed of in landfills, where it releases methane — a potent greenhouse gas — as it decomposes, sometimes directly to the atmosphere. Millbrae’s grease receiving station will reduce the amount of grease sent to landfills.
The grease and other organic matter will produce enough biogas at the plant to generate about 1.7 million kilowatt hours annually meeting 80 percent of the plant’s power needs.
The total cost of the project, $5.5 million, was reduced by about $200,000 with a rebate awarded through the state of California’s Self-Generation Incentive Program administered by Pacific Gas and Electric Company. The net amount, along with maintenance costs, is being funded entirely by savings from the new system and, therefore, will have no effect on the city’s wastewater treatment rates.
"This is the only wastewater treatment plant in the U.S. to receive and process inedible grease in a self-funding, purpose-built system that successfully addresses so many challenges simultaneously," said Dick York, superintendent of the Millbrae plant. "It’s a complete solution that could be adopted in many cities around the country."
(Chevron Energy Solutions)