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Renewable CNG Produced from Food Scraps in South San Francisco


South San Francisco Scavenger Company (SSFSC) and its partner Blue Line Transfer, is operating an onsite system which converts food scraps and yard waste into transportation fuel and compost. The facility, which began operations in January 2015, uses dry anaerobic digestion technology to generate clean-burning CNG that powers the company’s collection fleet. The fully enclosed system process 11,200 tons of material per year, including food scraps and food soiled paper collected from businesses in the company’s service area, including South San Francisco, Brisbane, Millbrae, and San Francisco International Airport.

“We’re excited about the digester because it allows us to turn compostable food scraps into fuel for the very trucks that collect those materials. It’s a truly closed loop system,” said Doug Button, president of South San Francisco Scavenger Company and Blue Line Transfer. “Plus, the process keeps organic waste out of the landfill and cuts greenhouse gas emissions—benefitting the communities we serve, the environment and our company.”

Most anaerobic digesters currently online in California generate electricity from methane. Blue Line Transfer’s system, made by Zero Waste Energy, LLC, is the first dry anaerobic digester in the country to produce CNG transportation fuel.  Besides producing 500 DGEs per day of carbon negative RNG, the process provides digestate, a nutrient-rich substance that will be matured into certified organic compost. Compared to traditional composting, the dry anaerobic digestion process reduces greenhouse gas emissions and other air pollutants. The launch of the facility is part of South San Francisco Scavenger Company’s expanded business collection program for food scraps and food soiled paper. A campaign is currently underway to increase the number of commercial customers participating in the program. The company plans to expand the food scrap collection program to residents as well.