SD Corn: GAO Ethanol Water Use Report Is All Wet

Report says it takes 323 gallons to produce a gallon of ethanol from Dakota-grown corn, but only 10 gallons from Iowa-grown corn.

Published on: Dec 15, 2009

"This is just plain nuts," says Bill Chase, president of the South Dakota Corn Growers Association, referring to news about a GAO report on water usage for corn ethanol.

The Government Accountability Office recently released a report on corn water use by region.

The report says the in North Dakota, South Dakota, Nebraska and Kansas farmers an average of 323.6 gallons of water to produce one gallon of ethanol from corn kernels, with all but three of those gallons coming from irrigation.

It said Iowa, Indiana, Illinois, Ohio and Missouri use an average of 10 gallons of water for every gallon of ethanol and  Minnesota, Wisconsin and Michigan uses 16.8 gallons of water.

"Common sense is clearly missing. The ridiculous comparisons beg the question, 'whose calculator is GAO using to claim the Northern Plains uses 20 to 30 times more water to produce a gallon of corn ethanol than states along our borders?'" Chase says. "We will take on the water debate any day of the week, especially when compared to the water it takes to refine oil for gasoline."

Of the 13 main corn producing states, South Dakota ranks fourth lowest in the nation for corn acres irrigated at just 175 thousand acres in 2007, according to a November report from the USDA's National Agriculture Statistics Service (NASS). Iowa irrigated 107 thousand acres; and Minnesota irrigated 254 thousand acres of corn.

"How can it even be conceivably possible for South Dakota corn ethanol to require over 320 gallons of water and our neighbors in Iowa only need 10 gallons of water to produce a gallon of corn ethanol? It paints a picture as if we are trying to produce corn in a desert when in fact South Dakota will produce its most abundant corn crop on record this year with 690 million bushels," Chase says.

Approximately 20-25 inches of water are necessary to produce an acre of average-yielding corn. This translates to about 597,388 gallons per acre per year, or nearly 4,000 gallons per bushel, according to information from University of Kentucky. 

In South Dakota this year, since April 1, West Central regions received 14. 64 inches of rail; Central South Dakota received 17.64 inches of rain; and Southeast South Dakota received 22 inches of rain according to the South Dakota Ag Statistics Service. An inch of rainfall on an acre of corn is 27,000 gallons.

And with the advancements in the pipeline in the way corn uses water as seed companies develop more drought tolerant hybrids that require less water, the sky is no longer the limit for South Dakota corn production as rainfall becomes less of a factor.

What GAO doesn't give credit for is through evapotranspiration, corn returns more water to atmosphere than is used in irrigation. An acre of corn gives off 4,000 gallons of water a day in evapotranspiration, which calculates into about 1 to 1.5 million gallons of moisture per acre annually.

What's more is water use by corn ethanol plants has been reduced by 26% from 2001 to 2007 according to the U.S. Dept of Energy, Argonne National lab. Just 3 gallons of water are required per gallon of corn ethanol.

"It is patently unfair for GAO or any entity to 'penalize' or count against corn growers the use of rainfall water by corn crops. If rainfall lands in a parking lot at the GAO building and runs off into the Washington, DC storm sewer system and ends up in the Potomac or Anacostia Rivers nearby DC, should that rainwater be "counted" against the GAO in terms of its "water footprint?" says Chase.

The report also failed to put ethanol's water profile in context with other energy sources, primarily oil.

U.S. Geological Survey estimates 1,851 gallons of water are required to extract, transport and refine a barrel of oil (lifecycle); and the daily oil consumption is 20.8 million bbls./day (Energy Information Administration)

National Renewable Energy Laboratory estimates 65 to 90 gallons of water are required per barrel of oil

"The bottom line is corn ethanol is tired of the target on our back for issues other industries seemingly get a free pass for," says Chase. "When in reality, our renewable resource through corn ethanol is accelerating our nation toward reduced greenhouse gases and energy independence. What have other industries done for the U.S. consumer lately?"

Source: South Dakota Corn Growers