Bioethanol’s water requirements underestimated

At a time when water supplies are scarce in many parts of the world, scientists from the University of Minnesota are reporting that production of bioethanol – regarded by many as the clean-burning fuel of the future – may consume up to three times more water than previously thought.

Reporting their findings in the journal Environmental Science & Technology, Sangwon Suh and colleagues point out that annual bioethanol production in the U.S. is currently about 9 billion gallons and is expected to rapidly increase in the near future. But the growing demand for bioethanol, particularly corn-based ethanol, has sparked significant concerns among researchers about its impact on water availability.

Previous studies estimated that a gallon of corn-based bioethanol requires the use of 263 to 784 gallons of water from the farm to the fuel pump. But these estimates failed to account for widely varied regional irrigation practices, the scientists contend. A new estimate of bioethanol’s impact on the water supply using detailed irrigation data from 41 states paints a worrying picture. The researchers found that bioethanol’s water requirements can be as high as 861 billion gallons of water from the corn field to the fuel pump in 2007. And a gallon of ethanol may require more than 2,100 gallons of water from farm to fuel pump, depending on the regional irrigation practice.

However, the paper notes that a dozen states in the Corn Belt consume less than 100 gallons of water per gallon of ethanol, making them better suited for ethanol production. “The results highlight the need to take regional specifics into account when implementing biofuel mandates,” the article concludes.

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Source: American Chemical Society

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