Course: BFM 101 Biofuels Fundamentals

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Water Use in Ethanol Facilities

Current water use data in processing facilities is generally not public information. Most industry studies show that the amount of water used to produce one gallon of ethanol has been dropping since 1998. A 2005 report from Minnesota indicated average water use per gallon of ethanol produced dropped from 5.8 gallons in 1998, to 4.2 gallons in 2005 [2,3]. In 2005, an estimate of 4 gallons per gallon of ethanol produced was an industry average. However, the Renewable Fuels Association [6] reported estimates of 3 gallons of water use per gallon of ethanol. Mueller, 2010, [5] surveyed ethanol producers in Iowa, Minnesota, Nebraska and eastern South Dakota in the fall of 2008 and winter of 2009. From 2001 to 2008, water use was down to 2.72 gallons per gallon of ethanol produced by dry mill processing. Improvements in water treatment and recycling in production facilities over the years have cut water use (Table 3.2). Not all operating facilities report water use, thus survey averages are not comprehensive. A current industry average (2011) is likely between 3 and 4 gallons of water used per gallon ethanol produced. Consumptive use of water is much less because of improved reuse and recycling.

Relatively Speaking

How much water does an ethanol plant use?

Let’s consider a 100 Million gallon per (MGY) year ethanol facility, that uses an average of 4 gallons of water per gal of ethanol.

This facility will use 400,000,000 gallons of water per year.   Let’s be conservative and assume only 50% of this water is recycled or reused.  Thus consumptive use is 200,000,000 gallons of water per year.

By comparison, one center pivot irrigation system applying 6 inches of water over 130 acres in a year will use about 21,000,000 gallons of water.   It would take only 10 pivots systems using water at this rate to equal the annual consumptive use of our hypothetical ethanol facility.

How Much Water Does a Corn Crop Use?

The corn needed to supply the 100 MGY ethanol facility could come from 1,538 pivot systems,  potentially using 35 billion gallons of water (at 6 inches of application).

Relatively speaking, water needed for ethanol processing is a drop in the bucket compared to that needed to grow the corn.

Adapted from: Ethanol Mythbusters, F. John Hay, Extension Educator, UNL

Table 3.2  Water Use In Ethanol Facilities Over Time:  Various sources.

1 NREL=National Renewable Energy Laboratory; USDA=United States Department of Agriculture; MN=Minnesota study; RFA=Renewable Fuels Association; NDMS=National Dry Mill Corn Ethanol Survey (Mueller, 2010); ZLD=estimates with Zero Liquid Discharge

Resources by eXtension, Bioenergy & Sustainability, BIOEN3 CC BY-NC-SA 2.5
www.extension.org/pages/63365/bioenergy-curriculum

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