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Food + biogas = fuel
Manteca aims for 256K gallons of CNG
food waste
Food waste before it is loaded into a digester to create compressed natural gas at an agricultural operation. - photo by Photo Contributed

Manteca’s food waste combined with methane gas from the municipal wastewater treatment plant could generate enough compressed natural gas to power properly-equipped vehicles averaging 15 miles per gallon some 3.84 million miles a year.

That is the amount of fuel consumed by 192 vehicles logging 20,000 miles a year.

Those figures are based on data the City of Manteca submitted to the California Energy Commission and the CNGnow website.

If all goes well within two to three years Manteca will start producing 140,000 diesel gallon equivalents of compressed natural gas each year at a facility being planned at the wastewater treatment plant on  West Yosemite Avenue near the ACE passenger station. The operation ultimately could yield 256,000 diesel gallon equivalents on an annual basis.

Manteca plans to use the CNG it produces to power its solid waste division fleet to meet tightening San Joaquin Valley clean air standards. The food waste conversion will also meet another looming state mandate for jurisdictions to stop burying 90 percent of their biomass waste that includes food waste.

The city also plans to sell CNG beyond what solid waste trucks use to private sector vehicle owners at the planned fueling station at the wastewater treatment plant.

Manteca public works staff has factored in fuel savings for the solid waste fleet as well into future projected garbage service rates.

Based on the CNGnow website, a vehicle using CNG for fuel driven 20,000 miles a  year and that is getting 15 miles per gallon will spend $2,733 annual on fuel  (CNG prices at $2.773 a gallon) compared to diesel (prices at $3.89 per gallon) that would cost $5,187 as year. For a private  vehicle such as a Ford 250, Dodge Ram 2400 or a Silverado 2500 that are equipped  to burn CNG fuel it would take 3.31 years to recoup the cost difference between a convention engine/fuel setup and CNG.

Manteca currently flares about 107,000 cubic feet of biogas daily at the wastewater treatment plant. At the same time it burns natural gas in boilers to heat treatment plant digesters.

Some 3,140 tons of restaurant and commercial food waste from Manteca is currently being buried at the Austin Road landfill yearly.

In addition, 290 tons of fat, oil, and grease are exported to a Bay Area disposal firm.

Surveys have shown 45.7 percent of Manteca’s residential garbage consists of food waste. If separated, 9,128 tons of food waste can be diverted to the generation of CNG.

Altogether, the diversion would reduce what Mantea buries by 32 percent a year helping realize ongoing savings.

The California Energy Commission last week informed Manteca its application for a $3,018,000 matching grant to build a community-scale and commercial-scale advanced biofuels production facility has passed the pre-application screening.

Based on that, the City Council authorized spending $45,000 with Herwit Engineering to prepare the final grant

To contact Dennis Wyatt, email