Los Angeles County to produce transportation fuel from biogas

April 17, 2020. In 2014, Los Angeles County Sanitation Districts (LACSD) saw the writing on the wall; SB 1383 requiring diversion of organics from landfill was not drafted yet but already the push was on to divert food from landfills. So, the agency began exploring what has since turned into a multimillion-dollar program to be able to co-digest food and biomass at its wastewater treatment plant. The end product will be transportation fuel it will sell at its public compressed natural gas (CNG) station and possibly inject into the pipeline.

“The project is currently under construction, and we anticipate pushing the start button in July of this year,” says Will Chen, supervising engineer, energy recovery engineering section of LACSD’s Solid Waste Department.

Partnering with Waste Management, the agency spent three years assessing the feasibility of using the existing anaerobic digestion operation at its wastewater treatment plant in Carson to co-digest food and sludge. They experimented at one of LACSD’s 24 anaerobic digesters to ensure parameters were acceptable such as pH, conductivity, total solids and contamination levels from inerts like plastics and glass.

The conclusion was that up to 62 tons of food waste could be handled per day.

“Enforcement of SB 1383 will be in two years, and haulers will primarily have two options for food waste: compost or anaerobic digestion. This project has enabled us to expand acceptance of these materials,” says Chen.

LACSD has invested in equipment and built a preprocessing plant at the materials recovery facility adjacent to the closed Puente Hills landfill in order to offer preprocessing to customers.

What’s unique about this project is that the existing fueling station is adjacent to where the facility will be built. “We have a CNG station that can use RNG (renewable natural gas) now, and our intent is to feed that station 100 percent of our RNG. We are also evaluating pipeline injection and/or gas-to-energy,” says Chen, who explains that LACSD is now assessing its carbon intensity score, which determines the value of gas under California’s low carbon fuel standard (LCFS) credit program.

“For now, the station is open to the public with most of the vehicles being buses, trash trucks and passenger cars. In time, we intend to expand to accommodate large tractor trailers. With LCFS and RINs (renewable identification number), it makes sense. We should recover capital, and it should be a revenue-generating project to fund other food waste infrastructure projects,” says Chen.