How Sacramento takes food waste from tables to gas tanks

An innovative partnership is helping Sacramento, Calif., to reduce emissions and reduce landfill waste, while stimulating at least $1.1 million in tax revenue and local business opportunities. 

At the center of the Sacramento BioDigester project is an anaerobic digestion facility originally run by CleanWorld, which can process 25 tons of food scraps and organic waste daily. The plant is being expanded this year to handle four times that amount.

"As mayor, I have a vision to transform my region into the greenest in the country and a hub for clean energy technology," said Sacramento Mayor Kevin Johnson when CleanWorld was recognized with an Energy Vision leadership award for the project in November. "One of the signature projects to do this in Sacramento is to convert organic waste and specifically food waste to build a biofuels industry in our region. In fact, we had a specific goal to build three plants producing 1 million gallons of biofuel by 2020."

The city actually beat that goal by six years. With the expansion, the BioDigester will divert an estimated 40,000 tons of food waste from Sacramento landfills each year and displace the amount of diesel needed by these fleets by 700,000 "diesel gallon equivalents," according to Johnson. What's more, the facility reduces greenhouse gas emissions by some 20,500 tons annually and produces more than 10 million gallons of fertilizers and soil amendments that offer an additional revenue stream for the developers.

The process is pretty simple: organic scraps that have been separated from other waste streams are transported to the facility, where anaerobic digestion produces methane. The biogas is converted at the adjacent fueling station, where it is used to fuel the hauling equipment that brings the feedstocks there in the first place — closing the loop.

The project received four major environmental awards in 2013, including the governor's award for innovation. The back story of how the biodigester came to be includes not just Sacramento-based CleanWorld, but several key technology partners:

Atlas Disposal – A Sacramento-based waste hauler that not only transports feedstock to the facility but was the first to commit to procure the compressed natural gas created there for its truck fleet (the company created a division called ReFuel to focus on providing this service for other fleets)

BioCNG –  The Madison, Wis., developer that created the system for refining the biogas created at the biodigester into fuel almost identical in chemical qualities to pipeline natural gas

Clean Energy Fuels – A Newport Beach, Calif., company that provided the refueling station used to deliver the fuel to trucks in the region. (It manages about 500 fueling stations across the United States and Canada.)

From table to gas tank

The land where the biodigester is sited is owned by the county of Sacramento; it was previously a waste transfer station. The project began when a request for proposals was issued seeking alternate uses for the idle facility that had a strong environmental component, said CleanWorld CEO Michele Wong.

CleanWorld served as the primary technology provider, working with the project owner and development team to catalyze the idea and orchestrate the financing, construction and build-out. The team negotiated a series of relationships to arrange for feedstocks, approaching all the local waste haulers. Procurement relationships also were arranged with other local businesses directly, such as a processing facility for dairy company Hood Foods, Wong said.

Overall, more than a dozen organizations were involved with making the Sacramento BioDigester happen including five financing programs and banks, two construction and permitting agencies and eight technology and project development partners (including the companies listed above). "We are definitely a market-making company in that regard," Wong said.

The model works in places with an adequate supply of organic waste from agricultural, industrial and municipal sources. CleanWorld expects to work with several types of developers including:

  • Companies building waste-to-energy technology portfolios
  • Large organic waste producers that would like to build a facility at the source, to produce either electricity or compressed natural gas
  • Composting facilities or municipal recovery operations seeking to broaden its waste recovering programs

The concept of anaerobic digestion isn't all that new. What makes CleanWorld's approach unique is the modularity of its technology, Wong said. The components are prefabricated and require minimal additional water for sites, which means facilities can be built and commissioned more quickly.

"In Europe, these sorts of facilities are plentiful. ... One reason they have not been built in the United States is because they are highly capital intensive projects," she said.

Another reason is that the tipping fees for organic waste are far higher in Europe — in the realm of $100 per ton — than they are in the United States, she said. Although the fees vary dramatically, in Sacramento they are in the realm of $30 to $35 per ton. The fee to send scraps to the CleanWorld facility is competitive with that, Wong said.

The global market for anaerobic digesters and landfill gas equipment is projected to grow to $7 billion by 2018, compared with $4.5 billion in 2013, according to figures from the BCC Research Report "Waste-Derived Biogas: Global Markets for Anaerobic Digestion Equipment."

Aside from the Sacramento facility, CleanWorld was involved with the creation of an industrial-scale plant at American River Packaging in nearly Natomas, Calif., which handles 4,000 tons per year and produces about one-third of the electricity necessary to operate the site. Last December, it began commissioning technology at University of California at Davis that will process 20,000 tons of food service waste annually and supply electricity for the campus microgrid.

Top image: Atlas waste haulers transport organic scraps to the biodigester, where they are converted into biofuels used to run its local fleet.