December 1, 2020. As part of its mission to convert waste into resources, the Los Angeles County Sanitation Districts recently started up a biogas purification system to recycle food waste into renewable vehicle fuel. Food waste includes dinner scraps, spoiled fruit and vegetables from grocery stores and restaurants. “We’ve been converting food waste into electricity for over six years. With this new biogas purification system, we now also produce renewable natural gas that is used to fuel vehicles like cars, buses and trucks. We know that many cities are grappling with how to meet state requirements for recycling food waste and are pleased to offer a complete and cost-effective solution,” said Robert C. Ferrante, Chief Engineer and General Manager for the Sanitation Districts.
The Sanitation Districts’ food waste recycling program has several parts. Waste haulers collect food waste that has been placed in separate bins by their customers. The loads of food waste are delivered to the Sanitation Districts’ Puente Hills Materials Recovery Facility in Whittier. At the Whittier facility, the food waste is loaded into specialized equipment that removes contaminants like plastic bags and forks and blends the food waste into a slurry.
The Sanitation Districts then transport the slurry to their wastewater treatment plant in Carson. Waste haulers who have their own processing equipment also deliver slurry to the Carson plant. The slurry is added to the plant’s digesters, which are large, sealed tanks where microorganisms convert food waste and wastewater solids into biogas.
The biogas is used in two ways. Some is sent to the Sanitation Districts’ power plant located at the Carson facility where the biogas is converted to electricity that runs the treatment plant. The remaining biogas is sent to the new purification system to make fuel grade renewable natural gas. The purification system is capable of producing the renewable natural gas equivalent of 2,000 gallons of gasoline per day. The renewable natural gas is dispensed at the Sanitation Districts’ nearby fueling station that is open to the public.
“Because the Sanitation Districts manage both solid waste and wastewater, we already had most of the infrastructure needed for food waste recycling. We also received a grant from the California Energy Commission that helped fund the new biogas purification facility. As a result, we were able to complete our system relatively inexpensively and pass those savings onto our customers,” said Bob Asgian, head of the Sanitation Districts’ Solid Waste Management Department. “Use of our system has been steadily growing and we have additional available capacity to help more cities.”