environmentalresearchweb blog

« An EU Supergrid | Main | Earth to Exxon: “Be a Mammal, not a Dinosaur” »

More Water-Energy Nexus: Biofuels Dominate US Water for Transportation

A recent paper from the University of Minnesota, by Sangwon Suh and others, estimates the change in embodied water in corn ethanol from 2005 to 2008 (see: Water Embodied in Bioethanol in the United States; http://pubs.acs.org/doi/abs/10.1021/es8031067?prevSearch=water+ethanol+suh&searchHistoryKey).

This paper indicates that the state with the highest quantity of embodied water per corn ethanol is California - strangely higher than Arizona and New Mexico, both of which are estimated to be both growing corn and producing ethanol from it. The range of consumptive water embodied in corn ethanol is 5 to 2,140 liters H2O per liter ethanol. The high end of the range translates to a higher value as compared to my previous study on the water intensity of transportation, likely due to a different assumption regarding how much irrigation water is consumed. Suh assumes that all withdrawn irrigation water is consumed, whereas I used United States Geological Survey data for estimating consumption by subtracting how much withdrawn irrigation water is returned to the source.

The difference in the methods of Suh and myself are not that important, and Suh does us a favor by tracking the changes from 2005 to 2008. During this time period he estimates that the embodied water in corn ethanol has increased 46% and the total consumptive water use has increased by 68%. This implies that more marginal lands, with worse climates for corn agriculture, and being used to grow corn, for food or fuel. This tendency is of course the fear of many that we will be using irrigated agriculture for biofuels on marginal lands even though many are assuming annual crops or perennial grasses on these lands will not be irrigated. In many regions, such as over the Ogallala Aquifer, industrial agriculture has already been overexploiting groundwater resources. It is important to know that the vast majority of the water embodied in corn ethanol is from farming, and thus it is farming corn in general that impacts the water resources, and not necessarily the push for corn ethanol. The Renewable Fuels Standard simply creates another marker for corn, and exacerbates the situation.

Recent work we’ve done at the University of Texas at Austin’s Center for International Energy and Environmental Policy together with members of the Bureau of Economic Geology shows that in 2005 the water embodied in light duty vehicle transportation fuels in the US accounted for approximately 2.5% of the total water consumption. By 2030, we estimate this could be up to 10%, mainly due to increasing ties in the nexus of energy and water in the form of biofuels. This consumption of nearly 14,000 billion liters holds for a vastly different diversity in the number of miles driven on different fuels from 23% - 71% based upon petroleum - quite a spread! So we have many ways to use our water resources for creating new fuels for transportation … or food, but that’s another story.

Posted by Carey King on May 11, 2009 4:22 AM | Permalink