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Turning sewer & garbage into power?

Solar also may be in City of Manteca’s future

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Turning sewer & garbage into power?

South San Joaquin Irrigation District Utilities System Manager Don Battles stands next to some of the solar panels that are already helping Manteca reduce part of its water system power cost by 15 ...

HIME ROMERO/The Bulletin


POSTED June 13, 2009 2:37 a.m.
Manteca could stabilize its power costs by switching to renewable energy sources.

They could include:

•converting sewer or methane gas to electricity through a bio gas digester.

•solar photovoltaic installation to generate electricity.
•a biomass generator to turn garbage into electricity.

Navigant Consulting has completed an assessment report that determined those three options are economically viable while options to convert the municipal vehicle fleet such as garage trucks and pickups to alternative fuel use didn’t make fiscal sense.

A detailed game plan of how the city could pursue renewable energy while taking control of municipal power bills will take place during Tuesday’s 7 p.m. City Council meeting at the Civic Center, 1001 W. Center St.
The biggest user of energy – the wastewater treatment plant – consumes almost $1.2 million worth of electricity a year. It could cost between $2 million and $6 million in capital outlay to put in a bio gas digester to carry the load at the wastewater treatment plant. That would reflect a kilowatt per hour cost of 3.44 cents to 7.32 cents. That compares to the current PG&E charge of 12.39 cents.

The consultants determined the city could save $500,000 a year which means even if it cost as much as $6 million, the city would recoup its investment in 12 years. That, however, does not take into account PG&E rate hikes that have been happening at a frequency of two to three per year. That means the payback realistically will be shorter.

The aggregate cost of city power use excluding the wastewater treatment plant, traffic lights, and street lights is $1.2 million. Various solar photovoltaic installations would require $13.6 million to replicate the PG&E load. Grants that are available could reduce the cost to Manteca to $6.8 million which would reflect a 16-year payback. However, that assumes no PG&E rate increases for 16 years so the payback is conservative and should actually end up being shorter.

Burning garbage could generate electricity cost 7 to 9 cents per kilowatt but would require partnering with other agencies in the county to generate enough garbage to make it work. It would also help the city avoid landfill costs as it is charged per ton to bury garbage. It would also greatly reduce the potential need to truck garbage out of state in the coming years when landfill capacity is exhausted in California. Right now, garbage is being buried at a site on Austin Road between French Camp and Arch roads.
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