As home biodiesel brewers know, it's a time-consuming and chemically intensive process to transform French fry grease into a fuel. And then there's the problem of burning something in your truck that could have fed people; canola oil can be used for food or fuel, for example.

That's why many biodiesel devotees—including DARPA, the Defense Department's research arm—have turned to plentiful algae: it grows like a weed and certain strains can be turned into buckets of oil. Plus, it's not a nutritional staple like soy or palm oil.

The question is: How do you convert algae oil into biodiesel efficiently?

Biodiesel made from plant stock or animal fat (or a combination of the two) will likely get a lot of attention in the coming year as a potential fuel alternative to the petroleum, gasoline and kerosene polluting the environment. But don't expect human cellulite to make the cut when it comes to renewable fuel, despite claims by one Beverly Hills, Calif., doc that he powered his Ford SUV and his girlfriend's Lincoln Navigator using fat that he liposuctioned from patients.

Craig Alan Bittner, 40, medical director of the now-defunct Beverly Hills Liposculpture and a board-certified radiologist, didn't stick around to make his case for the use of flabby fuel. Rather, he fled to South America to avoid prosecution for several alleged crimes (in addition to the unsubstantiated claim of using human fat to make biodiesel), including allegedly allowing his assistant and his girlfriend to perform surgeries without a medical license, Forbes.com reports.

Researchers from the University of Nevada, Reno, have discovered that coffee can be turned into an alternative fuel other than caffeine: biodiesel. And you can have your coffee and drink it too. No need to use the fresh stuff, old grounds are more than up to the task, according to material scientist Mano Misra and his colleagues.

Even after being subjected to the rigors of brewing, roughly 15 percent of the weight of dried coffee grounds is oil, which, much like palm and soybean oil, can be converted into biodiesel. The coffee has the added benefit of not being a food source, like palm oil and soybeans.

Nevertheless, more than 16 billion pounds of coffee are produced globally every year, according to the U.S. Department of Agriculture. Misra estimates that the grounds from that haul could be used to make as much as 340 million gallons of biodiesel. For their part, the researchers turned grounds donated by Starbucks into biodiesel that had the added advantage of smelling like a fresh cup o' Joe.

Making a few stops along the way, BioJet 1 went 1,776 miles of a 2,486-mile journey from Reno, Nev., to Leesburg, Fla., exclusively on biodiesel. The fuel in question, made by Lake Erie Biofuels, was a blend of soy and animal fats turned to diesel.

The Aero L-29 jet kept the biodiesel from congealing at high altitude by continuously heating it—and landing every 300 miles or so to refuel. The flight is a proof of principle, according to Green Flight International CEO Doug Rodante, and is aimed at addressing the carbon dioxide (CO2) emissions from burning jet fuel -- roughly 3 percent of total worldwide greenhouse gas emissions, according to the U.N. Intergovernmental Panel on Climate Change (IPCC), but released in a very bad spot—high in the atmosphere.