If lattes seem overpriced now, wait until coffee becomes a precious commodity. An engineering professor spied an opportunity in the layer of oil he found floating in an old cup of coffee one morning. He extracted what was left in some used grounds—about 10%-15% oil by weight—with simple chemistry and produced $1-a-gallon biodiesel, the New York Times reports.
Several hundred million gallons of biofuel could come from the coffee brewed just this year, though that’s only about 1% of the diesel guzzled in the US. Still, a pilot program is being set up with a Nevada roaster to test the waste’s potential. “It won’t solve the world's energy problem,” the prof admits, but it’s the only fuel that leaves a sweet aroma. (Read more biodiesel stories.)