Illustration by Pelle Mellor
As a biofuel, the advantages of coffee over alternative biofuels are numerous: it does not diverting crops from being a food source because it’s made from the left over coffee grounds. it’s consistently available globally, it can easily yield 10-15% of biodiesel by weight, it requires little or no tinkering because it has lower viscosity, manufacturing costs are at about $1 per gallon, and when burned it leaves a smell many of us love!
If you’re interested in producing some coffee-based biodiesel here’s the process, but it’s really better suited for a larger-scale producer:
“The diesel-extraction method for coffee grounds is similar to that used for other vegetable oils. It employs a process called transesterification, in which the grounds react with an alcohol in the presence of a catalyst. The coffee grounds are dried overnight and common chemical solvents, such as hexane, ether and dichloromethane, are added to dissolve the oils. The grounds are then filtered out and the solvents separated (to be reused with the next batch of coffee grounds). The remaining oil is treated with an alkali to remove free fatty acids (which form a soap). Then the crude biodiesel is heated to about 100ºC to remove any water, and treated with methanol and a catalyst, so that transesterification takes place. When cooled to room temperature and left to stand, the biodiesel floats up, leaving a layer of glycerine at the bottom. These layers are separated and the biodiesel is cleaned to remove any residues.
From Mar 5th 2009 The Economist print edition http://www.economist.com/science/tq/displaystory.cfm?story_id=13174477