Water Consumption for Biofuel Feedstock Cultivation

Water use may prove to be a central issue in the global and local development of the biofuel industry. While most literature on biofuel water use only considers the biorefinery phase, we studied water consumption for biofuel feedstock cultivation in major feedstock-producing regions of the United States. Using a spatially explicit Penman-Monteith model informed by field-level eddy covariance measurements, distributed climate data, and land use figures, we estimated water consumption and net water use for a number of scenarios of feedstock, location, and refining processes for biofuel development. We find that in California, for example, average water consumption for biofuels from different feedstocks ranges from about 900 to over 1500 gallons per gallon of fuel produced. Cellulosic feedstocks are found to be less water-intensive on average. Furthermore, we find feedstock cultivation to account for more than 99% of the life-cycle embedded water for fuels in California. In some regions and for some feedstock options, a shift to biofuel feedstock cultivation would reduce the strain on water resources, while in others we project it would greatly increase water demand. We are expanding this analysis to better capture both base-line ET from natural systems and ET of some of the less-studied cellulosic feedstocks, as well as to incorporate other regions in the U.S. and internationally. Thus far, we conclude that while water demand for processing is important for plant location and pollution, water consumption for feedstock growth may be (along with land resources) the limiting factor for bioenergy production in many regions.