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fuel food
A City of Manteca solid waste truck used to pick up and deliver large collection boxes is being fueled with compressed liquefied gas Tuesday.

Food scraps left today on plates at Applebee’s along with the vegetable oil McDonald’s uses to deep fry McNuggets will end up powering the City of Manteca solid waste truck collecting brown and blue residential carts later this week.

That’s because what Public Works Director Mark Houghton touts as “Manteca’s own refinery” is now converting methane gas generated at the wastewater treatment plant along with food waste to produce compressed liquefied gas.

And in doing so, Manteca is well on its way to effectively wiping out all CO2 impacts the wastewater treatment process creates and then some. That’s because all of the city’s heavy duty trucks as they are replaced will have engines powered by clean burning CNG to eliminate the use of diesel fuel.

Manteca’s food-to-waste endeavor — part of a $35 million project that included building two new digesters and refurbishing the two existing digesters — was celebrated Tuesday with a ribbon cutting at the city’s municipal wastewater treatment plant on West Yosemite Avenue.

“This project demonstrates that Manteca is not only the Family City but is also the Can Do City,” Houghton told the gathering under the canopy of where the public will eventually be able to use a card-lock system using Visa cards to fuel their CNG vehicles.

The cutting edge technology and the fact Manteca is the trailblazer for such a project in the Great Central Valley stretching from Bakersfield through Sacramento to Redding was not lost on speakers representing U.S. Senator Dianne Feinstein, Bay Area Congressman Eric Swalwell as well as those appearing on behalf of Congressmen Josh Harder and Jerry McNerney. All commented on how the project would not only improve air quality in Manteca but also throughout the San Joaquin Valley and nearby regions.

“Back in the 1970s when I went to work for the city, the blue skies were not blue,” Manteca Mayor Ben Cantu said. “They were brown.”

Cantu lauded the project as the latest endeavor to make skies even bluer and air cleaner. He praised for foresight of both staff and previously elected leaders that set the project in motion.

There are only two other facilities in California capable of using methane gas from the wastewater treatment process and food waste to make liquefied gas — one in San Diego and the other in the Bay Area.

The impact of the project and long range cost savings to the city is multiple dimensional.

uWhen fully implemented, the $350,000 annual diesel bill at current prices to run the nearly 30 dozen trucks of the Manteca solid waste fleet has, will be eliminated.

uGiven $10 million of the $35 million project was exclusive to the CNG process was covered in part by a $3 million California Energy Commission Grant and a $1.893 million San Joaquin Valley Air Pollution Control District grant, it left $5.1 million for solid waste ratepayers to cover. Based on not having to pay for diesel thanks to the output of “the Manteca refinery”, the city will recover its investment in about 14 years.

uThe biofuel generated qualifies for what’s called a Renewable Identification Number (RIN) under a federal program put in place in 2007. Those RINs constitute credits that oil companies purchase so they meet a federally mandated goal that a percentage of their fuel production is biofuels. The value of what Manteca will produce per gallon in terms of RINs fluctuates with the market. The RIN value is currently pegged at $2 a gallon. Houghton said the RIN funds weren’t plugged into the cost recovery and will be considered “gravy” due to market volatility. If the RIN were to stay valued at a constant $2 a gallon, the investment for the food to waste process would be recovered in less than 10 years.

uThe digesters were in need of replacement a few years ago prompting the public works staff to take a holistic approach to city solid waste streams that was possible as Manteca is one of the few cities in the state that has retained its own solid waste collection system instead of contracting it out. The digesters put in place — they have floating roofs to allow for the storage of compressed liquefied gas once it is created — serve a dual purpose of converting food waste to fuel and being part of the wastewater treatment process. Houghton said the economy of scale plus refurbishing the older two digesters allowed significant cost savings to bring that part of the project to $20 million. The digester components now in place should be able to serve a population of roughly 150,000 residents.

uCommercial food waste is no longer being landfilled.  That saves tipping fees of $52 per ton plus meets a state mandate that eventually will slap cities with penalties for burying more than a certain percentage of food waste. 

uThe process also uses FOG — fat, oil, and grease — produced by restaurants and concerns such as meat packing firms that is now trucked out of the area by private collection firms to an East Bay Municipal Utility District facility in Oakland. It would reduce costs for local firms including what is arguably the biggest producer of FOG in Manteca — the Sunnyvalley Meat Co. located directly across the street from the wastewater treatment plant.

uThe city can generate revenue from trucking firms that run on CNG fuel as well as residents with vehicles powered the same way. Rates have yet to be set although Houghton said the city will not undercut a nearby commercial CNG operation in Lathrop.

uThere are 32 fueling stations that allow for more effective overnight slow fueling of solid waste tanks that are typically enough to more than cover a day’s run. If by some chance due to manpower shortage or such and a second run was need they can use the quick fueling facility that is designed for public access.

uThe $400,000 CNG powered trucks that are being purchased as older trucks are required run significantly quieter to reduce noise pollution during early morning residential collections.

uThe relocation of the solid waste fleet to the wastewater treatment plant to allow them to be fueled overnight means they can now be washed with recycled wastewater instead of potable water. Trucks –  to keep a lid on smell and other issued — are washed daily after runs are completed.

The city is in the process of moving forward with a solar farm at the treatment plant that when completed will wipe out much of the $1.6 million annual power bill to run the wastewater treatment process.

To contact Dennis Wyatt, email,