On Water Use and Efficiency Advancements

By Geoff Morgan | May 12, 2011

No doubt about it, corn ethanol consumes large quantities of water in its production.  Some studies conclude that, in the same period of time that ethanol production doubled, the related water use tripled.  This has garnered some attention in the public eye, along with the food vs. fuel and other arguments that cast aspersions on corn ethanol.

Water occupies two distinct sources of use in the production of ethanol—that used for irrigating and growing the corn, and that used to boil, distill and ferment the biofuel.  People argue that as corn production has increased in areas of the country that require more irrigation, more water is needed to produce a gallon of ethanol. True, but it is unclear what the allocation of corn use in those areas is—fuel or food.

So what are the facts surrounding water use generally and, in particular, what effect does water technology and regulation have in the corn ethanol industry and what can be done to improve the efficiency of the water used?

The truth is that the production of ethanol has not had a significant impact on water resources in the United States. U.S. Geological Survey data suggest that the industry uses less than 100 million gallons of water daily which equates to two one hundredths of one percent of total water use in the U.S. We sometimes hear the argument that it takes up to 4,000 gallons of water to grow a bushel of corn, but seldom hear that the overwhelming majority of that amount comes from rain water.

Also, ethanol producers are constantly increasing the efficiency of the use of water. The Renewable Fuels Association reports that in 1994, it took more than six gallons of water to produce one gallon of ethanol and now many plants can produce a gallon of ethanol using only three gallons. What technologies are making this possible? More efficient use of recycling, advancements in the areas of water separation technology (utilizing sophisticated membranes to separate water and ethanol in biofuels production) are meaningful examples. R3 Fusion just announced this month the availability of a new commercial system for recovering ethanol from waste scrubber water. The system is designed to process 50 gallons per minute of scrubber waste generated from a 50 MMgy ethanol plant. Private industry continues to produce new developments that should continue to increase efficiencies.

Many other technologies are also being pursued. Producing broths with higher ethanol concentrations can reduce the energy needed for distillation. Alternative technologies to distillation, such as pervaporation (a membrane separation process), also have the potential to significantly reduce water usage. Another option for reducing water demand is to utilize a different heat transfer medium, using forced-air fans for cooling instead of water where appropriate. This could potentially result in much lower evaporative and blowdown losses. Other conservation technology has resulted in significant reduction in water use for cooling towers. 

As cellulosic ethanol technologies develop and achieve commercial scale, efficiencies should continue to increase, as most feedstock sources for cellulosic ethanol need far less water for their growth. The National Renewable Energy Laboratory is analyzing water use issues in cellulosic ethanol production as well as water use in the production of biofuel feedstocks. All of these positive developments also compare favorably to water used in the production of petroleum-based fuels. NREL estimates it currently requires about 2 to 2.5 gallons of water per gallon of gasoline.

So what does this tell us? First, private industry and innovation have resulted in a steady increase in the efficiency of the use of water in biofuels production. Second, the use of water in the biofuels industry is minimal compared to water use generally in the United States. It is incumbent on the industry to continue to pursue advancements, but it is also worth noting what has been accomplished already.

Author: Geoff Morgan
Partner,  Michael Best & Friedrich LLP
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