What goes in the Anaerobic Digester?
Michigan State University has a goal of a campus with 100 percent renewable energy. Tuesday, it moved 500 watts a year closer to that goal.
Engineers introduced the newest member of the school's green family is an anaerobic digester. Manure and food waste go in and clean, renewable energy comes out.
"What the anaerobic digester does is helps us reduce waste by using a lot of the food waste from the cafeteria," said Jennifer Battle, MSU's director of campus sustainability. "That in turn produces renewable energy for the campus."
Cow manure and waste from campus cafeterias are placed in an airtight tank, capable of holding 450,000 gallons of material. For 20-30 days that tank is heated to 100 degrees Fahrenheit, hastening the decomposition process and producing methane gas, which can be turned into energy.
Five percent of the energy produced will be used to run the digester itself. An additional 15-20 percent runs the entire farm.
"So we could actually export from this project 60-70 percent of the energy we actually generate," said Dana Kirk, a project engineer. "So it's a net energy producer and a net energy exporter from a small farm."
The project costs about $5 million but is expected to pay for itself in less than 15 years.
"This is what it is to be Spartan green," said Carla Iansiti, an MSU residential hospitality sustainability officer. "Not only being green but being green responsibly and giving back to the environment is what we want to show."
And while the university will only send post-consumer waste to the digester (i.e. food that was taken but not eaten), it has already been making use of its pre-consumer waste (such as onion peels and ends of vegetables not served). That waste is composted and used in soil. That soil in turn is used to grow some of the produce that makes it back into campus dining centers.
"MSU really does bleed green," said Jennifer Battle. "So the sustainability pieces of what we do is not only beneficial to the environment, it's economically beneficial and beneficial to the community."