Researchers at the University of Minnesota have concluded that the amount of water used in ethanol production varies up to 2,138 liters of water per liter of ethanol, depending on regional irrigation needs.
Corn ethanol is already plagued by environmental concerns such as pollution from fertilizer, pesticides, and herbicides; soil erosion; greenhouse-gas emissions from production; and competition for agricultural land with food crops.
The new study, published in the journal Environmental Science and Technology, also found that as corn-based ethanol production has approximately doubled nationwide between 2005 and 2008, related water use has more than tripled.
In some states, such as Ohio, Iowa, and Kentucky, where corn can grow with little to no irrigation, only five to seven liters of water are required to turn the foodstuff into fuel. Almost all of this water is used to boil, ferment, and distill the biofuel.
As ethanol production has increased, however, more corn is being grown in western states such as Nebraska, Colorado, and California, where irrigation needs raise the fuel’s water requirements significantly.
“This is one more nail in the coffin for ethanol,” says David Pimentel of Cornell University, in Ithaca, NY, whose own studies have shown that ethanol requires more energy to produce than it releases when burned, and that the fertilizer used to grow corn for ethanol has contributed significantly to dead zones in the Gulf of Mexico (areas of the ocean with low oxygen content due to increases in chemicals in the water).
The U.S. Energy Independence and Security Act of 2007 mandates that ethanol produced using existing technologies will have to increase from the 34 billion liters produced in 2008 to 57 billion liters per year by 2015. This includes the more arid western states, where corn-based ethanol is currently produced.
“We’re already in an unsustainable situation in terms of water use, already drawing down aquifers like the Ogallala,” Schnoor says of the vast underground water source stretching from South Dakota to northern Texas. “This would exacerbate that decline if we expand in these irrigation states.”
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