TRENDS IN GROUNDWATER USE AND ETHANOL PRODUCTION IN IOWA (2004-16)

Iowa is the largest producer of corn ethanol in the United States. About 4.2 billion gallons were produced in 2017 at 43 ethanol plants, which accounts for more than 27 percent of total U.S. ethanol production. Approximately 1.3 billion bushels of corn (47 percent of Iowa corn production) goes toward the production of ethanol annually. Production has increased significantly to current levels from about 859 million gallons per year (MGY) in 2004. The largest increase of 760% occurred between 2004 and 2014, but production has since leveled off due to uncertainties involving the future of the Renewable Fuel Standard and the low price of ethanol. The dry milling process used at 90 percent of the ethanol plants requires large amounts of water, both for the fermentation process and also the production of steam for on-site coal or natural gas power plants. Water use related to ethanol production increased from 2.5 billion gallons per year (BGY) in 2004 to nearly 8 BGY in 2016. Although surface water is used, groundwater is the preferred water source because its chemistry is stable, unlike the large variability that occurs in surface water. Of those 43 ethanol plants, 24 plants use groundwater from high-capacity wells permitted directly by the Iowa Department of Natural Resources (IDNR), which maintains records of groundwater use. In 2016, those plants used about 6.8 billion gallons. Nameplate ethanol production data suggest that water use has become more efficient over time, with the ratio of groundwater gallons withdrawn per ethanol gallons produced hovering near 3.0 and dipping below that value in some cases. The remainder of groundwater withdrawals for ethanol comes from municipalities or from rural water systems, who maintain their own high-capacity well permits with IDNR. A discussion of basic ethanol and water-use policy in Iowa will also be presented in this talk. Although the high-capacity wells utilize at least seven different aquifer systems ranging from the Cambro-Ordovician to alluvial aquifers, ethanol plants have created water allocation challenges in Iowa because of the increased construction of high-capacity wells. We will review IDNR’s approach to water allocation conflicts and the rationale for granting the permits using two case studies, one of which involves a cellulosic ethanol plant.