Not only will the fuel be cheap, but the exhaust will also produce the wonderful aroma of coffee.

Scientists at the University of Nevada, Reno, researching the prospect of extracting oil from used coffee grounds report that the process is not that difficult. The cheap and environmentally friendly biofuel is abundant enough to potentially manufacture several hundred million gallons a year to power cars and trucks.

The idea was formed by accident says the chief researcher. “I had left my coffee out one night, and the next morning, I noticed that there was a kind of oil around the edge of the cup,” Mano Misra, a professor of engineering said. “Every cup of coffee has it. I decided to do some tests on the oil.”

The analysis proved that the grounds contained roughly 10 to 15 percent oil by weight. The researchers then extracted the oil with standard chemistry techniques and converted it to biodiesel.

For the study, the team collected leftover grounds of espressos, cappuccinos and other coffee preparations from the Starbucks coffee chain.

Being that the process is not particularly energy intensive, the researchers estimated that biodiesel could be produced for about a dollar a gallon.

According to the Department of Agriculture, the world’s coffee production is more than 7.2 million tons per year.

The study was first reported toward the end of last year in The Journal of Agricultural and Food Chemistry.

The resulting coffee-based fuel –which smells like java– is more stable than traditional biodiesel due to coffee’s high antioxidant content, according to the researchers.

“We have found that biodiesel created from spent coffee grounds is stable over a longer period of time than other forms of biodiesel that have been created from feed stocks such as soy and corn,” Misra said. “Biodiesel from spent coffee grounds is a low-cost ‘green’ form of fuel that shows a significant reduction of carbon dioxide emission. It’s an excellent source for biodiesel.”

One hurdle, Dr. Misra said, is in the organized collection of the spent beans. Therefore, the researchers plan on setting up a pilot operation this year using waste from a local bulk roaster.

It won’t be a complete fix for reducing America’s dependence on oil, but it can be a help while at the same time providing a nice aroma for those in the vicinity. The researchers report that the exhaust actually smells like coffee.

“It won’t solve the world’s energy problem,” Dr. Misra said of his work. “But our objective is to take waste material and convert it to fuel.”