Study Finds Regional Variations in Irrigation Practices Can Push Corn Ethanol Water Requirements 3x Higher Than Earlier Estimates; Need to Account for Regional Specifics in Mandates
08 April 2009
| Top: County-level corn production and ethanol facilities in 2007. The graph illustrates the proximity of ethanol facilities to corn production. Bottom: EWe and TCW of each state as of 2007. The foreground bar height indicates the EWe of each state, with the portion of ground and surface water indicated by color. The TCW, as measured by a state’s EWe and ethanol production (seen in the background), illustrates local and regional ethanol-induced impacts. Credit: ACS. Click to enlarge. |
Researchers at the University of Minnesota have estimated state-level field-to-pump water requirements of corn ethanol production across the US. Their results find that corn ethanol’s water requirements can range from 5 to 2,138 L per liter of ethanol depending on regional irrigation practices. Prior studies have estimated that corn ethanol requires 263-784 L L-1of water from corn farm to fuel pump.
Based on their calculations using state-level water use data, Sangwon Suh and colleagues also found that the national ethanol-production-weighted average water requirement in the US was 142 L L-1 in 2007— much lower than what was previously estimated in other studies. The new paper is scheduled for the 15 April 15 issue of the ACS journal Environmental Science & Technology.
The results also show that as the ethanol industry expands to areas that apply more irrigated water than others, consumptive water appropriation by bioethanol in the US has increased 246% from 1.9 to 6.1 trillion liters between 2005 and 2008, whereas US bioethanol production has increased only 133% from 15 to 34 billion liters during the same period. The results highlight the need to take regional specifics into account when implementing biofuel mandates, the researchers say.
...the spectrum of EWe [embodied water in ethanol] is wide enough that the national average is not useful in representing ethanol’s water dependence in the US. Each state illustrates a significantly different degree of water dependence year by year. Depending on where and how corn was produced, TCW (total consumptive water use) can vary greatly...nationally averaged irrigated water figures are irrelevant in understanding ethanol’s water implications, and the discussion should account for regional variations interpreted on a local basis.
—Chiu et al. (2009)
The researchers estimated the corn farm to fuel pump water requirement per liter of ethanol—termed embodied water in ethanol (EWe)—in 41 corn producing states from 2005 to 2008 using the most detailed regional and state statistics. EWe is defined for the study as the sum of irrigated water (WIR) at corn farms for feedstock production as well as the process water (WP) consumed within biorefineries, divided by total ethanol production within a state, which is presented in liters of water per liter of ethanol (L L-1).
Naturally occurring, direct precipitation to corn fields was not included in WIR to isolate purely anthropogenic water consumption induced by corn ethanol production. Each state’s total consumptive water use (TCW) is defined as the sum of WP and WIR of the state attributable to its bioethanol production.
Among the other findings of the study:
As a general trend, the EWe increases from the East to the West and from the Midwest to the Southwest regions of the US. Among the 19 ethanol-producing states in 2007, Ohio shows the lowest EWe of 5 L L-1, whereas California has the highest EWe of 2,138.
Of the 15 billion liters of ethanol produced in 2005, 4 billion liters (28%) had a EWe greater than 100 L L-1. Of the 17 billion liters of production added from 2006 to 2008, 8 billion liters of ethanol production (43%) will have a EWe greater than 100 L L-1. The results indicate that EWe and TCW increased by 46 and 68% from 2005 to 2008, respectively. The difference between these two categories illustrates more corn production for ethanol is taking place within highly irrigated regions.
To reduce the water requirements to meet the 57 billion liter conventional biofuel production mandate by 2015 under the EISA, future expansion of corn ethanol production needs to take regional or county-level water use practices into account. Our study also shows that corn ethanol produced in the High Plains aquifer appropriates large amounts of groundwater from vulnerable fossil resources. Continued expansion of corn ethanol development in those regions will have more significant impacts on water sustainability than that in regions with no or little irrigation.
Our study highlights the need to strategically promote ethanol development in the states with lower irrigation rates and with less fossil groundwater use. According to the survey conducted by the United States General Accounting Office (GAO) in 2003, 36 out of 47 states expect varied degrees of water shortages within the next decade. It is notable that all the high-EWe states in our study were those classified in the GAO survey as to be likely to experience statewide (Colorado), regional (Wyoming), local (Kansas and Oklahoma), or uncertain water shortages (California and New Mexico). Continued expansion of corn production in these regions is likely to further aggravate expected water shortages of the region.
The time left for improving water consumption is limited. To achieve substantial EWe reduction, we have to pay attention not only to biorefineries but also to regional irrigation practices. As the 57 billion liters of annual ethanol production mandate is 90% fulfilled by current operating biorefineries and facilities under construction, concerted and immediate action needs to be taken in order to prevent a problem shift from energy supply to water sustainability.
—Chiu et al. (2009)
Resources
Yi-Wen Chiu, Brian Walseth and Sangwon Suh (2009) Water Embodied in Bioethanol in the United States. Environ. Sci. Technol., Article ASAP doi: 10.1021/es8031067
From Chiu et al:
The silliness of this statement is hard to overstate. Corn grown in California is going to consume the same amount of water if it feeds chickens, people or SUVs. The only way to address the problem of aquifer depletion in these areas is to stop growing irrigated crops there (which will happen anyway when the aquifers are dry or too deep to pump economically). Water subsidies to this acreage should be eliminated to put them back to dry-land farming, and ethanol mandates should be reduced or eliminated to make up for the cut in corn production.Posted by: Engineer-Poet | 08 April 2009 at 09:54 AM
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Burning our food for fuel is idiotic. Biodiesel based on algae, grown in a tiny portion of our desert wasteland (see UNH research), will easily fuel the country. This will require no modifications to our culture (which, yes, has the loons/control freaks in a tizzy) and will simply require that gas engines be phased out for diesel as one purchases a new vehicle.
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Posted by: The Goracle | 08 April 2009 at 10:36 AM
This is why they grow corn in Nebraska and lettuce in California. Truck crops grown in the Imperial Valley of California bring a higher price. No one is using food for fuel. You use corn stalks and wheat straw for cellulose biofuels.
Posted by: SJC | 08 April 2009 at 11:24 AM
Biodiesel based on algae, grown in a tiny portion of our desert wasteland (see UNH research), will easily fuel the country
A pipe dream intended for the gullible.
Posted by: Will S | 08 April 2009 at 12:29 PM