We recently heard that, according to one group of researchers at Environmental Science & Technology magazine, corn ethanol has a water cost of 50 gallons per mile. Now, a team working from the University of Twente in the Netherlands has calculated the water cost of ethanol and other biofuels and to make bioelectricity. The results are not pretty. The researchers looked at 13 crops and tried to calculate the most efficient way to turn them into energy depending on where the crops were grown, and which process was used to turn the biomass into either biofuel or electricity. The worst offenders included making biodiesel from rapeseed or soya (14,000 liters of water to make just one liter of biodiesel) and jathropha (20,000 liters of water), according to the abbreviated description we found at Alpha Galileo. The researchers found that the most efficient crop-to-energy ratio came from turning whole sugar beet plants into electricity. If you're just interested in making biofuels, then sugar beets are still your best bet. A liter of ethanol made from sugar beets uses "just" 1,400 litres of water, the Twente researchers found. Second and third generation biofuels made form algae or advanced cellulosic processes were not included. Coskata, for example, says their process uses less than a gallon of water to make a gallon of ethanol.

[Source: Twente (in Dutch), Alpha Galileo via Greenbang]
Photo by D Sharon Pruitt. Licensed under Creative Commons license 2.0.