As researchers worldwide scramble to find alternatives to oil, they're beginning to make use of some pretty unusual raw materials.

Talk about natural resources—it turns out that just about any kind of plant or animal waste, and many kinds of garbage, can be turned into biofuels or other sources of clean energy for cars, trucks, or industry. Here are some of the least expected possibilities being tested.

Chocolate

Researchers at Britain's University of Warwick have built a Formula 3 race car that runs on 30 percent biodiesel derived from chocolate waste. As a bonus, the steering wheel is partially made of carrots and other root vegetables.

Dirty diapers

A plant in Quebec turns soiled diapers into fuel. Using a method called pyrolysis, the plant heats up the diapers without oxygen. That breaks down the molecules of both the diapers and their, um, contents, yielding synthetic methane gas and diesel-like oil.

Turkeys

Bones, beaks, and feathers: A Carthage (Mo.) refinery can make diesel that's 80 percent turkey parts from a nearby slaughterhouse. The plant, which went bankrupt and closed last year, is slated to reopen with a capacity of 12 million gallons a year, double its original size.

Urine

Ohio University's Gerardine Botte can convert urine to hydrogen, which is used to make electricity. While it's hard to collect enough human urine to make the process commercially viable, it may be a boon for hog farmers, who have trouble disposing of pig urine.

Beef by-products

Amtrak carries human passengers on the backs—and other parts—of cattle. The Heartland Flyer rides the rails between Oklahoma City and Fort Worth using a biodiesel blend known as B20: 20 percent fuel made with beef by-products and 80 percent diesel.

Coffee

Coffee grounds can consist of up to 20 percent oil, making them an abundant source of biofuel. Researchers at the University of Nevada-Reno have separated oil from grounds and turned it into biofuel. The result even smells like your favorite java joint.

Cow manure

Every cow creates enough waste to keep two 100-watt light bulbs lit 24 hours a day, according to utility Central Vermont Public Services, which has offered "Cow Power" since 2004. Manure from 5,000 cows is used to make methane, which fires generators.

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