I think that this would be a great idea. I could use my leftover coffee grinds to run my car.
Biofuels: A novel form of biodiesel is derived from an unusual feedstock that is more commonly used to fuel mental activities: coffee
In the case of coffee, the biodiesel is made from the leftover grounds, which would otherwise be thrown away or used as compost. Narasimharao Kondamudi, Susanta Mohapatra and Manoranjan Misra of the University of Nevada at Reno have found that coffee grounds can yield 10-15% of biodiesel by weight relatively easily. And when burned in an engine the fuel does not have an offensive smell—just a whiff of coffee. (Some biodiesels made from used cooking-oil produce exhaust that smells like a fast-food joint.) And after the diesel has been extracted, the coffee grounds can still be used for compost.
Although some people make their own diesel at home from leftovers and recycled cooking oil, coffee-based biodiesel seems better suited to larger-scale processes. Dr Misra says that a litre of biodiesel requires 5-7kg of coffee grounds, depending on the oil content of the coffee in question. In their laboratory his team has set up a one-gallon-a-day production facility, which uses between 19kg and 26kg of coffee grounds. The biofuel should cost about $1 per gallon to make in a medium-sized installation, the researchers estimate.
Commercial production could be carried out by a company that collected coffee grounds from big coffee-chains and cafeterias. There is plenty available: according to a report by the United States Department of Agriculture, more than 7m tonnes of coffee are consumed every year, which the researchers estimate could produce some 340m gallons of biodiesel. Time, perhaps, to pour another cup before refilling the car.