Pilot Anaerobic Digester for Campus Food Waste Conversion


Department of Cell Biology and Molecular Genetics



Professors Stephanie Lansing (Environmental Science and Technology), Steve Hutcheson (Cell Biology and Molecular Genetics), and Rick Kohn (Animal Science) built a small-scale anaerobic digester to test a new process of converting organic waste into energy. Three ENST Senior Capstone teams (16 students total spanning three years of the Capstone courses) utilized this unit as well as 4 summer UMCP interns, 1 Brazilian student and 1 high school student. The facility was originally sited at the Beltsville Agricultural Research Center in Beltsville but moved to the UMD Upper Marlboro facility (Terp Farm) due to USDA access restrictions before it was operational.  
Grant funds were initially used for the various grinder pumps, sump pumps and plumbing needed to assemble the anaerobic digester. Initially food waste from Dining Hall food preparation was used as the waste food source, but the material offered was difficult to manage (and pump) for this application (e.g., cantaloupe rinds). Two other waste sources where identified: Panda Express/Moby Dick from in the Stamp Union food court and produce waste from the weekly Farmers Market on campus. The last ENST Capstone group (2016-2017) also used food waste from the Board and Brew, a restaurant on Baltimore Ave.
The exposed location at Upper Marlboro had two unanticipated consequences. First, the outside temperature fluctuations caused the temperature control system to malfunction and one of the tanks had a hole melted through the side of the tank. This required replacement of that tank and a change of the temperature control system. The second problem was the lack of protection from freezing temperatures. To solve these issues, an insulated enclosure was built to enclose and stabilize the tank temperatures. The temperature control was redesigned to use hot “antifreeze” in coils internal to the tanks.  
Much of the time during the grant period was spent resolving technical issues related to the tanks chosen. When the unit was operational, roughly 60% methane biogas was generated at a promising rate. About 35% of the biogas was CO2 that could be removed using a commercial CO2 scrubbing unit to clean up the biogas to the equivalent of natural gas. The biogas, as produced, could also be used directly in an engine generator set to produce electricity.