[Digestion] Kitchen grease to biogas

[Zietsman, Rex]

Here is an interesting article:
"MILLBRAE, CA -- Chevron Energy Solutions, a unit of Chevron
Corporation, and the City of Millbrae today celebrated the completion of
new facilities at Millbrae's Water Pollution Control Plant that use a
common urban waste -- inedible kitchen grease from restaurants -- to
naturally produce biogas for generating renewable power and heat to
treat the city's wastewater.

The unique system, engineered and installed by Chevron Energy Solutions,
includes a grease receiving station and an expanded cogenerator as well
as other upgrades that result in annual revenues and energy savings of
$366,000 for Millbrae while nearly doubling the amount of "green power"
produced at the plant.

More than 3,000 gallons of restaurant grease -- the kind washed from
grills and pans -- will be 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 wastewater
treatment. Meanwhile, excess heat produced by the cogenerator warms the
digester tanks to their optimum temperature for methane production.

"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 applying proven
technologies and 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."

"This innovative project brings new meaning to the term 'sustainable
development,'" said Millbrae Mayor Robert Gottschalk. "Through our
partnership with Chevron Energy Solutions, we're taking an urban waste
and turning it into an asset for the city and the environment."

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, which will
meet 80 percent of the plant's power needs and reduce its electricity
purchases significantly. This lower demand for utility-generated power
reduces carbon dioxide emissions by 1.2 million pounds annually, the
same amount of carbon dioxide absorbed by planting about 170 acres of
trees.

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.

The project's completion is being celebrated today at an event in
Millbrae attended by national, state and local government officials and
representatives from business, environmental organizations and academia.

"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 partners with institutions and businesses to
improve facilities; increase efficiency; reduce energy consumption and
costs; and ensure reliable, high-quality energy for critical operations.
The company employs proven technologies to meet customers' specific
needs, including infrastructure technologies, energy controls, solar
photovoltaics, fuel cells, biomass and other systems.

For more information about Chevron Energy Solutions, please visit
www.chevronenergy.com "