Engineering students at the University of Michigan have found a way to justify junk food: Make fuel from its waste grease.
A four-student team demonstrated that it's economically and technically feasible to harvest 10,700 gallons of waste grease produced in 10 campus dining halls to make an effective biodiesel fuel. The fuel was tested out on a small U of M tractor.
The University already uses some biodiesel fuel. It purchases 60,000 gallons from a commercial vendor to blend with regular diesel fuel to make up the 300,000 gallons of combined fuel it uses annually.
The students collected waste grease from deep fryers and mixed it in a tank with potassium hydroxide and methanol to create a reaction that produced glycerine and fatty acid methyl ester solution. The glycerine is separated out and the residual solution is heated up to evaporate excess alcohol and water. Also, the students discovered the glycerine by-product of the process could be cured and used to make a biodegradable alternative to commercial soaps on campus.
According to U of M professor Walter Weber Jr., the potential economic and environmental benefit of the development is huge to any institution that produces large quantities of waste. For example, the University produces nearly 11,000 gallons of waste fat annually that is removed at a cost of 95 cents/gallon. Even if an institution decided not to produce biodiesel fuel itself, it could still realize significant savings in disposal costs by harvesting the waste grease and contracting a vendor to convert it to biodiesel fuel. By replacing the 10,700 of the 60,000 gallons of commercial soybean oil biodiesel with the students' product, the University could save an estimated $28,000.