Michigan State University in Lansing has commissioned a $5 million anaerobic digester that will re-use waste from the university’s farms and dining halls to create energy for several buildings on the south end of campus.
The anaerobic digester will use about 17,000 tons of organic waste to generate 2.8 million kWh per year. About 20 percent of the energy from the digester is used to sustain the process, but the other 80 percent is available for other uses on campus, which will pay for the digester in about 15 years. In comparison, a smaller anaerobic digester already in use at MSU for research purposes uses almost all of the biogas it produces to run the system.
The feedstock the system will use includes cow manure from the MSU Dairy Teaching and Research Center; food waste from several campus dining halls; fruit and vegetable waste from the Meijer Distribution Center in Lansing; and fat, oils and grease from local restaurants.
The digester holds about 450,000 gallons of feedstock, which is then maintained at roughly 100 degrees Fahrenheit for 20 to 30 days. The organic material is decomposed by a group of naturally occurring microorganisms found in livestock manure. The result is biogas and a slurry of partially decomposed organic matter, water and nutrients.
In addition to the two on-campus anaerobic digesters, MSU is also involved in a similar project in Costa Rica. Earlier this year a digester went online that will help provide power to a village in the Central American nation. The project is a partnership between MSU and the University of Costa Rica.