Is There Enough Water to ‘Grow’ Ethanol?

by Bill Chameides | June 23rd, 2009
posted by Erica Rowell (Editor)

Permalink | 2 comments

Current ethanol production is primarily from the starch in kernels of field corn. Growing corn requires considerable amounts of water, but just how much depends on which state the corn is grown in. (NREL)

A recent study points out that when it comes to water usage, where your ethanol is brewed really matters.

Several studies (see here, here, and here) have developed national averages for the amount of water needed to grow corn ethanol. But now researcher Yi-Wen Chiu and colleagues at the University of Minnesota have published a paper in Environment Science and Technology that draws attention to the variations in water consumption across states. They found that:

  • where the ethanol-bound corn is grown largely determines the amount of water needed to produce the ethanol; and
  • for some perverse reason, as we grow more corn for fuel, those crops are increasingly being planted on land that requires irrigation (or in other words more water).

The upshot of these findings? Not only are we using more water; we are doing so at a faster rate. This may have troubling implications for water-challenged regions of the country, such as the Plains states and California.

Water Demands of Growing and Producing Ethanol in Selected States*

Liter of Water Consumed
Per Liter Ethanol Produced
Ethanol Produced
(million liters)
Ohio (lowest rate of water use)        5       11
Iowa (top ethanol producing state)        6 6,857
Illinois       11 3,486
Minnesota       19 2,296
South Dakota       96 2,203
Nebraska     501 2,481
California (highest rate of water use) 2,138    257


Implications of Meeting the Biofuels Mandate

More ethanol means more water usage. (NRCS)

To meet the 2015 mandate for corn ethanol of 57 billion liters (15 billion gallons), called for in the Energy Independence and Security Act of 2007, ethanol production will need to increase by 40 percent.

If that ethanol were produced from corn grown in the three states with the lowest water consumption rates (Ohio, Iowa, and Kentucky), the consumption rates of Chiu et al. suggest that total U.S. water use would increase by 61 billion liters. Put slightly differently, that would mean consuming 3.25 percent of all water currently used for irrigation in the country.

Alternately, if the corn were to come from states with the highest water consumption rates (those using more than 100 liters of water to produce one liter of ethanol), 2,400 additional billion liters of water would be consumed — or 4.5 percent of all water currently used for irrigation in the United States. Is that a big deal, or just an extra percent or so — not worth worrying about?

We’ll Run Some Water and Corn Numbers and You Decide

Number of corn-growing states in the United States (as of 2007):  41

Number of the 41 corn-growing states not expected to have water shortages before 2015: 6
(source [pdf])

Number of U.S. states that both grow corn and refine ethanol (as of 2008): 19

Number of the 19 corn-growing and ethanol-refining states not expected to have water shortages before 2015: 3
(source [pdf])


* includes surface and groundwater sources

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  1. Dan K.
    Jun 23, 2009

    As CP reports this evening, Waxman has acquiesced to some demands of the rural Democrats, indicating that in the House bill: “Waxman also consented to block EPA from calculating ‘indirect’ greenhouse gas emissions from land-use changes when implementing the federal biofuels mandate. The Democrats will impose a five-year moratorium to allow further study of the issue, with consultation from Congress, EPA, the Energy Department and USDA instrumental in restarting the measurements in the biofuels rules.” While it is a difficult and nascent task of determining LCA/ILUC effects of biofuels, it sets a potentially noxious precedent for future Congresses/Presidents. I just hope the EPA will still be doing work on this, ready to go seemingly in 5 years to get it incorporated into the legislation. I’m optimistic but it is a classical political punting of the pigskin down the road. We’ll see.

    • Bill Chameides
      Jun 26, 2009

      Dan, I share your concern about this compromise. Not counting indirect land-use changes (ILUC) when doing a life-cycle analysis (LCA) for biofuels is like not attributing air pollution in New York to smokestacks in Ohio. I will have more to say on this in a future post. Stay tuned.

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