Article: R Dominguez-Faus et al (2009). The Water Footprint of Biofuels: a Drink or Drive Issue?     Environ. Sci. Technol., 43 (9), pp 3005–3010. DOI: 10.1021/es802162x

Synopsis: Using conservative estimates of water consumption for irrigated biofuel agriculture in Nebraska and the assumption that the typical vehicle will travel 16 miles to every gallon of ethanol, team of researchers R. Dominguez-Faus and Pedro J. Alvarez of Rice University as well Susan E. Powers and Joel G. Burken determine that on average 50 gallons of water are necessary to produce ethanol for each vehicle mile driven.

“The Water Footprint of Biofuels: a Drink or Drive Issue?” focuses on the agricultural aspect of biofuel life cycles and how it impacts water quantity and quality.  This impact is deemed the “water footprint” of the fuel. Many prior studies have been devoted to the positive and negative aspects of biofuels with respect to land, air, and net energy values.   This article centers on the expected negative effects of the present trajectory of biofuel production. Dominguez-Faus and the coauthors explain that biofuel feedstocks (specifically the row crops of the Midwest such as corn, soy, and sorghum) require significantly more water than traditional sources of energy.

Incentives for biofuels such as ethanol subsidies and the guaranteed market created through the renewable fuel standard have lead farmers to produce biofuel feedstocks on lands where it may have otherwise been economically infeasible.  Land in regions with insufficient or unreliable rainfall requires water intensive irrigation practices and may be causing water shortages in these regions.  Nebraska, for example has been experiencing water shortages that are seemingly related to corn production reaching an all time high in 2007 and 2008.  Dominguz-Faus et al admit that due to the “spatial and temporal variability” of rainfall, it is difficult to predict with any certainty that water shortages will result directly from irrigation practices for the growth of biofuel feedstocks.

In the United States, corn and switchgrass are the least water intensive biofuel feedstocks.  Switchgrass is a lignocellulosic feedstock and was not considered to be an economically viable option at the time of this publication, leaving corn as the primary means to meet biofuel targets each year.  While corn does not require as much water as some other feedtocks, researchers explain that the crop is extremely chemical intensive.  When the chemicals run off into surface water, water quality is negatively impacted.  Dominguez-Faus and the coauthors explain that on average, rainfall in the upstream regions of the Midwest will have anywhere from 24% to 36% of Nitrogen from fertilizers end up in local water systems.

The article discusses potential for the conservation reserve program (CRP) to improve water quality through changes in land use.  Government payments are made to farmers to retire land that is easily eroded or that requires excessive chemical inputs and tilling.  Incentives to retire land to the CRP resulted in a noticeable decrease in water pollutants in 2007.  However, participation in the program is decreasing as farmers seek to take advantage of policies such as ethanol subsidies that promote biofuels.

The team explains that the water consumption and degradation issues associated with biofuels can be addressed through practicing sustainable agricultural methods such as crop rotation.  Also, charging market rates for irrigation water is suggested to encourage the growth of crops in more suitable climates.  Dominguez-Faus et al suggest that incentives are necessary to encourage the production of cellulosic biofuels and that a system similar to the CRP could be designed to promote the growth of these feedstocks in marginal lands to lessen land and water degradation.  Lastly, the authors suggest revising or doing away with policies such as ethanol subsidies and fuel standards that contradict and detract from programs such as the CRP.  Overall, the article puts forth that biofuels are not a lost cause and with careful research and planning, especially with respect to cellulosic biofuels, Dominguez-Faus and the coauthors claim that we may in fact be able to “have our drive and drink our water too.”

The full article can be downloaded here.