Water Use in Ethanol Production

Historically the nation’s lead corn producing area, the North Central Region, now leads the bioenergy industry in production of corn-based ethanol. It also leads the nation in water used for bioenergy. In 2010, the United States produced over 13 billion gallons of ethanol, with an estimated 11.7 billion gallons produced in the North Central Region, which encompasses the states ranging from the Dakotas to Ohio, and Michigan to Missouri. Iowa and Nebraska were the two leading ethanol producers [1]. The widespread soil and water resources of the Great Plains and Midwest Corn Belt are the reason for this concentration of production [2] (Figure 3.1).

Water use in ethanol production facilities is viewed in two ways: 1) the total facility water use and impact on local water supply, and 2) the water used per gallon of ethanol produced. Total facility water use and impact on local water resources depends on the size of the processing facility and how efficient it is in water used per gallon of ethanol produced. So, in fact, these two views are related.

Figure 3.1. County-level corn production and ethanol facilities operating status by 2007. The graph illustrates the proximity of ethanol facilities to corn production (2).

If a facility is drawing water from a ground or surface water source it may have a significant impact on local water supply. Aquifer drawdown may affect neighboring water users and there is considerable emphasis on water reuse and recycling. The Zero Liquid Discharge concept focuses on reducing consumptive use of water to a minimum by reusing liquid water rather than discharging it. Co-location of ethanol facilities to share water with other industrial users is another water efficient practice to reduce impact on aquifers and water supplies.

In the production life cycle of corn-grain ethanol, water for feedstock growth and processing into ethanol are the two greatest water users; and water to grow the feedstock dominates consumptive water use. However, the monetary cost to provide this water, and ultimate “water cost” paid, including redirecting water from alternative uses, depends on whether crops are grown with irrigation or without, and how water is treated in ethanol processing facilities. There are vast differences regionally in how water is used.

Pages: 1 2 3 4