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Most people have heard about diesel vehicles modified to run on used vegetable oil, but there’s only so much of that to go around. Apparently, coffee grounds are between 11 and 20 percent vegetable oil by weight, and when you take into account the fact that global sales of coffee reached 18.4 billion pounds this year, there are a lot of used coffee grounds to be had! If all those grounds were used to produce biofuel, it would work out to between 300 and 400 million gallons’ worth; to provide you with a sense of scale, in 2007, total U.S. fuel oil production was 1.5 billion barrels, or 46.5 billion gallons. When put into context, it is obvious that this technology will not be the silver bullet that solves our carbon concerns, but it could certainly help to lessen the demand for petroleum, especially if used in concert with other sources such as ethanol from native plants or cellulose.
If the process can be scaled up successfully, it has the potential to be very efficient; all of the oil from the grounds can be used to produce biodiesel, and the byproducts from the process can be used to create ethanol, as well. What’s more, what’s good for humans may be good for the vegetable oil, too- the high proportion of antioxidants in coffee helps to keep the oil from breaking down, making long-term storage easier. One can even envision a situation where restaurants can sell their grounds for a little bit of extra profit!
The question of environmental impact would seem minimal in this case, but two factors need to be taken into consideration. One, the production of ethanol and biodiesel involves significant energy and water inputs (approximately 660 watt-hours and 125 liters of water for every liter of ethanol produced, according to a comparative study of biofuels); requirements for biodiesel production from soybeans in the same article were 270 watt-hours and a considerable amount of steam input, but the methods and inputs involved in biodiesel production from coffee may significantly differ. The second issue is the coffee itself; while there are varieties of coffee that can grow in shaded environments, “full-sun coffee” has become widely used due to its superior production rate but its more open nature reduces available habitat, increases erosion, and requires fertilizer and pesticide use to maintain. The question of impact, then, is ours to answer.