Billions of gallons of motor oil are drained from engine crankcases each year, and only some of it is reused. Much of it is simply thrown away or burned. But that old oil could find new life as fuel for your car.

Researchers at University of Cambridge have developed a process that uses microwaves to recycle old motor oil into gasoline-like fuel for use in conventional vehicles. They claim the process has "excellent potential" for commercial use.

“Transforming used motor oil into gasoline can help solve two problems at once,” Howard Chase, professor of biochemical engineering, said in a statement. “It provides a new use for a waste material that’s too-often disposed of improperly, with harm to the environment. In addition, it provides a supplemental fuel source for an energy-hungry world.”

Some estimates suggest 8 billion gallons of motor oil are used annually worldwide. Some is collected and re-refined into lubricating or heating oil, but there are concerns about the pollution involved in doing so. A sizable amount of that old oil is simply discarded or burned.

Pyrolysis is one promising way of reusing old oil. The oil is heated in the absence of oxygen and breaks down into a mix of gases, liquids and a small amount of solids. The gases and liquids can be chemically converted into gasoline or diesel fuel. Trouble is, current methods of heating the oil do so unevenly, so the oil is not easily converted into fuel.

Chase says his team's method uses microwaves to overcome this problem. His team mixed the old oil with microwave-absorbent material, then heated the mixture with microwaves. The pyrolysis process converts nearly 90 percent of a waste oil sample into fuel, and it has been used to produce conventional gasoline and diesel.

“Our results indicate that a microwave-heated process shows exceptional promise as a means for recycling problematic waste oil for use as fuel,” Chase said. “The recovery of valuable oils using this process shows advantage over traditional processes for oil recycling and suggests excellent potential for scaling the process to the commercial level.”

Chase presented his findings Tuesday at the 241st National Meeting & Exposition of the American Chemical Society in Anaheim, California.

Photo: Kendrak / Flickr