UC Davis commissions biodigester

The University of California, Davis (UC Davis), and Sacramento-based technology partner CleanWorld officially unveiled the UC Davis Renewable Energy Anaerobic Digester at the campus’ former landfill on April 22, 2014, Earth Day.

The anaerobic digestion (AD) technology invented by Dr. Ruihong Zhang, UC Davis professor of biological and agricultural engineering, is being used inside large, white, oxygen-deprived tanks. Bacterial microbes in the tanks digest campus and community food and yard waste, converting it into energy that feeds the campus electrical grid.

“It has been the thrust of my research to bring the innovations we made possible at UC Davis to commercial scale,” Zhang said. “This technology can change the way we manage our solid waste. It will allow us to be more economically and environmentally sustainable. I am proud and grateful to be a part of the team who helped make this moment a reality.”

The digester at UC Davis is the third commercial biodigester that CleanWorld has opened using Zhang’s technology within the past two years and is the nation’s largest anaerobic biodigester on a college campus, according to the company.

The system is designed to convert 50 tons of organic waste to 12,000 kilowatt hours (kWh) of electricity each day using state-of-the-art generators, diverting 20,000 tons of waste from local landfills each year.
The facility has taken advantage of its location at the now closed UC Davis landfill by blending landfill gases – primarily methane – with the biogas to create a total of 5.6 million kWh per year of electricity. It is expected to reduce greenhouse gas emissions by 13,500 tons per year.

“The biodigester is the latest chapter in UC Davis’ world-renowned legacy of environmental sustainability,” says Linda P.B. Katehi, chancellor of UC Davis. “This project stands as a model public-private partnership and demonstrates what can be achieved when research universities and private industry collaborate to address society’s most pressing challenges.”

CleanWorld CEO Michele Wong and vice president of research and development Josh Rapport are UC Davis alumni. Rapport received his doctorate in anaerobic digestion from UC Davis under Zhang’s tutelage in 2011.

“There is so much to celebrate today as we recognize the far-reaching environmental and sustainability impacts this technology will have,” says Wong. “It will enable the more than 100 million tons of organic waste each year that is currently being landfilled in the U.S. to be converted to clean energy and soil products. CleanWorld is proud to be the commercialization partner with Dr. Zhang and UC Davis for these game-changing innovations. With this project, we’ve crossed the bridge from research and development to commercialization and proven that CleanWorld’s high-solid AD system can be a feasible, cost-effective, and repeatable solution, not only for municipalities and communities, but also for universities and public institutions throughout California and the U.S.”

Within the biodigester closed loop system, whatever is not turned into biogas to generate renewable electricity can be used as fertilizer and soil amendments – 4 million gallons of it per year, which may provide natural fertilizers for an estimated 145 acres of farmlands each day.

Nearly half of the organic waste, or feedstock, needed to operate the biodigester to full capacity will come from UC Davis dining halls, animal facilities and grounds. CleanWorld is working with area food processing and distribution centers to supply the remaining amount. Meanwhile, UC Davis will earn 100 percent of the project’s green energy and carbon credits and receive all of the electricity generated.

The project’s backers say it benefits from a unique public-private partnership. While Zhang moved the technology forward, CleanWorld’s commercializing efforts have made it modular, cost-effective, and faster to deploy, making it one of the most advanced, commercially available anaerobic digestion systems in the country, according to the company. The biodigester went from bare ground to full installation within six months. Its $8.5 million cost was roughly two-thirds less than other anaerobic digesters the university researched as potential renewable energy sources, says CleanWorld.

CleanWorld financed the majority of the project with private equity and a commercial loan from First Northern Bank, Dixon, Calif. Approximately $2 million in public funding came from the U.S. Department of Energy and the California Energy Commission.