Water worries cloud future for U.S. biofuel

From the Scientific American:

It’s corn planting time in the U.S. Plains, and that means Kansas corn farmer Merl “Buck” Rexford is worrying about the weather — and hoping there is enough water. Rexford plans to start seeding his 7,000 acres near Meade, Kansas, this week and he is relishing a recent heavy snow storm that dropped several inches of much-needed moisture.

Like corn farmers throughout the United States, Rexford hopes to grow a healthy crop yielding more than 150 bushels an acre this year. Much of his crop will wind up at a nearby ethanol plant. And that puts the 65-year-old Rexford at the center of a bitter divide over biofuels, particularly corn ethanol.

Critics argue that precious water resources are being bled dry by ethanol when water shortages are growing ever more dire. Federal mandates encouraging more ethanol production don’t help.

According to the article, most of the water consumption occurs in the manufacturing process:

“Biofuels are off the charts in water consumption. We’re definitely looking at something where the cure may be worse than the disease,” said Brooke Barton, a manager of corporate accountability for Ceres, a group backed by institutional investors focused on the financial risks of climate change.

Corn is a particularly thirsty plant, requiring about 20 inches of soil moisture per acre to grow a decent crop, but most corn is grown with rain, not irrigation. Manufacturing plants that convert corn’s starch into fuel are a far bigger draw on water sources.

Water consumption by ethanol plants largely comes from evaporation during cooling and wastewater discharge. A typical plant uses about 4.2 gallons of water to make one gallon of ethanol, according to the Institute for Agriculture and Trade Policy.

The ethanol industry pegs that at about 3 gallons of water to 1 gallon of fuel.

Read more from the Scientific American by clicking here.

But the water use figures depend highly on where the corn is grown, according to the University of Minnesota:

Ethanol production in Minnesota and Iowa uses far less water overall than similar processes in states where water is less plentiful, a new University of Minnesota study shows.

The study, which will be published in the April 15 edition of the journal Environmental Science and Technology, is the first to compare water use in corn-ethanol production on a state-by-state basis. The authors used agricultural and geologic data from 2006-2008 to develop a ratio showing how much irrigated water was used to grow and harvest the corn and to process it at ethanol plants.

Among the major ethanol-producing states, Iowa uses the least water, with about six gallons of water used for each gallon of ethanol. Minnesota, which in 2007 produced roughly a third as much ethanol as Iowa, uses about 19 gallons of water per ethanol gallon.

States where irrigation is needed to grow corn fared far worse than those where almost no corn is irrigated. California, which produces only a tiny fraction of the nation’s ethanol but irrigates most of its corn, is the largest water consumer, at about 2,100 gallons of water per gallon of ethanol. South Dakota, with total production roughly equal to Minnesota’s, uses about 96 gallons of water to produce one gallon of ethanol.

Read more from the University of Minnesota by clicking here.

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