The Economist.com has a post about coffee biodiesel. Now that is an idea that smells good.
Coffee is also a plant product, but once the beans are ground and used they end up being thrown away or put on gardens as compost. Narasimharao Kondamudi, Susanta Mohapatra and Manoranjan Misra of the University of Nevada at Reno have found that coffee grounds can yield by weight 10-15% of biodiesel relatively easily. Moreover, when run in an engine the fuel does not have an offensive smell—just a whiff of coffee. Some biodiesels made from used cooking-oil leave a car exhaust smelling like a fast-food joint. And after the diesel has been extracted, the coffee grounds can still be used for compost.
