| Energy independence and global climate change are motivating substantial investment in fossil fuel alternatives. As the ongoing examination of options proceeds, one of the primary alternatives for liquid fuels in particular is the use of bio-fuels. Biofuels are derived from biological feedstocks (e.g., corn, wood, sugarcane) and generally replicate the physical and energetic properties of the fossil fuels they are intended to replace (e.g., combustion temperatures, liquid vs. gas). Because the large scale implementation of biofuels would minimize implications for transforming existing transportation infrastructure, and because they are, in theory, carbon neutral with respect to emissions vs. uptake, they are being widely cited as a sustainable solution. The central criteria for evaluating the sustainability of energy resources is their ability to produce net energy (energy out per energy in), and decisions about feedstocks and processing will largely be made based on comparative energy return on investment (EROI). However, the life cycle of biofuel production includes numerous other resource inputs that need to be accounted for to determine large scale feasibility. The most obvious of these is water, particularly in light of accumulating evidence that human uses of water (both quantity and quality) are unsustainable (e.g., Vorosmarty and Sahagian 2000). Development of an analytical schema for assessing the hydrologic footprint of large-scale biofuel production is the objective of this proposal. |
