Water Use and Ethanol Production

In light of this US News and World Report article about NRDC's recently released report on western water and global warming, an astute colleague of mine asked me about water use in ethanol refining. Here's what I told him: 

"The current corn ethanol technologies use (i.e. loose to evaporation) between 4 and 6 gallons of water per gallon of ethanol and the first generation of cellulosic are likely to use as much as 12. However, there is no technological reason that both technologies couldn't use about 1. The water is primarily lost cooling the power plant and we know how to do dry cooling with virtually no water. It adds size and some cost, but fundamentally the water issue related to refining is purely one of incentives and policy requirements." 

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