Garbage as Fuel

Biodigester converts organic waste to energy

In 2006, UC Davis in partnership with Onsite Power Systems launched the Biogas Energy Project featuring the “biodigester”, a technology that utilizes bacteria to convert organic waste into natural gas in the form of methane and hydrogen. Behind the technology is Ruihong Zhang, a professor in the Biological and Agricultural Engineering Department at UC Davis. Professor Zhang has experimentally determined the optimal conditions the bacteria need to work efficiently, as well as combined anaerobic phased solids digester system (APS-Digester) and anaerobic mixed biofilm reactor (AMBR) technology enabling both solid and liquid processing within the digester. Propane powers the digester’s start-up and shutdown and regulates the digester’s temperature.

Now, four years after the launch of the pilot program, a commercial biodigester has been created for the City of Industry’s garbage hauler, and another will be put to the test in powering a new West Village housing community at UC Davis, to be opened for occupancy in fall 2011. The biodigester technology is advantageous in that natural gas is produced in a cost-effective manner, and organic waste, such as food scraps, are diverted from the landfill and converted into a compostable material thereby reducing waste.

The concern with a commercialized biodigester is the variable of contamination. Within an experimental environment only pure organic matter is being placed into the digester. A digester receiving loads from the public will be exposed to at least minimal contamination i.e. landfill or recyclable materials (plastic utensils, foil wrappers, bottles or cans) in the digester’s waste stream. How will the digester respond to contamination? How much contamination can be accepted? Will the bacteria work unhindered around the misplaced items or will the contamination effect the established optimal environment, or even compromise the process completely?

The technology and research has been proven to work, but collaboration with the community will be essential to the digester’s success. Education will be important to reducing contamination when implementing the novel biodigester technology and an additional waste stream into the community. This technology, however, could provide us with an economical alternative energy, as well as change the way we view our organic waste.

http://www.universityofcalifornia.edu/advocacy/your_university_03_2008/r...
http://news.ucdavis.edu/search/news_detail.lasso?id=9192
http://www.onsitepowersystems.com/files/PropaneCouncil-Biodigester_Wins_...