A computer design model of the three-ton, trailer-mounted vehicle helped engineering students lay out the various components necessary for the system. Source: Virginia Tech

Using leftover food from a campus dining hall, mechanical, civil and environmental engineering students at Virginia Tech have been able to fuel a generator that produces enough electricity to power an average-sized home.

As part of a senior capstone design project, the students originally set out to design a generator capable of producing 1 kilowatt of power with a methane content of 50 percent. However, the students exceeded that goal by producing almost 5 kilowatts with a methane content of over 60 percent.

"When used at scale, a process like this does several things,” said Steven Cox, an advisor to the team and president of GkW Energy, which sponsored the team. “First, it reduces the amount of product going into landfills, which the university pays for by the pound. Second, it means we aren’t shipping that product 75 miles and then returning 75 miles with compost, so it saves more money and lowers our carbon footprint by limiting mileage in large trucks.”

Weighing more than 6,000 pounds, the machine uses methane — not gasoline. Positioned on a 22-foot flat-bed trailer is the generator, the 1,000-gallon reactor and two flexible gas holders gathering methane. The "seed" fluid from the anaerobic reactor jumpstarts the reactor, breaking down the food waste and thus creating the methane, which is ultimately stored in the gas holders. Eventually the captured methane is used to power the electric generator. Additionally, a series of electrical outlets is mounted on the trailer for demonstration purposes and includes standard 120 volt outlets, as well as a 240 volt outlet used to run heavier appliances, such as clothes dryers.

Researcher believe that the system can be upgraded and tailored to be used anywhere large amounts of food are created (for example, small farms).

The biogas generator was on display during the Senior Design Expo on April 28.