Top: Food waste is processed using an industrial version of a household garbage disposal, then fed into the digester. Image courtesy Sacramento State University

Sacramento State University (Sac State) in Sacramento (CA) installed an on-site anaerobic digester to process food scraps from campus kitchens, eateries, and a children’s center to produce renewable power and a fertilizer for use on the campus. The Impact Bioenergy digester, valued at $200,000, was a gift from Cal Maritime, which was unable to use it, according to an article on the Sac State Sustainability webpage. It is housed in a metal shipping container in the Bioconversion and Agricultural Cooperative Yard on the campus, which is also home to a garden, honeybee hives and composting areas. Incoming food waste is hand sorted to remove plastic contaminants, large pits and other items that could clog the machine. It is fed into an industrial version of a household garbage disposal, where it is ground up and mixed with bacteria that break down the food, and then flows into the digester. Retention time is 24 to 72 hours. The biogas is converted into electricity and can be stored in portable batteries for use at university events instead of gas generators, notes the article. The facility will be used by students and faculty for research projects. “We want this to be a living lab for students to get experience doing research on things such as food-to-gas ratios, biodigestion itself, and learning how to use our own food waste to create biogas and electricity,” explains Waste and Sustainability Analyst Laura Gonzalez-Ospina.