In this research, water use was analyzed for bioethanol production from cradle to gate, using hybrid poplar feedstock and an acetogen pathway conversion process. Volumetric water use and availability was quantified, using the water footprint methodology by Hoekstra et al. (2011). Two hypothetical biorefineries near Mount Vernon, WA and Spokane, WA using rainfed and irrigated feedstock, respectively, were analyzed for three crop yield scenarios. Two climate change scenarios will be presented to demonstrate the effect of higher temperatures and variable precipitation. A policy analysis of water regulations was also conducted.
Results show that water use for bioenergy from hybrid poplar is 70-250 times higher than estimates for crude oil, though lower than many estimates for other bioenergy crops and conversion processes. Results vary by climate and crop production, with the rainfed crop using significantly less water than the irrigated crop. Climate models predict increased irrigation demand and decreased site suitability. In Washington State, limited opportunities to obtain senior water rights exist, so policy constraints add another layer of complexity to biofuel expansion. To fully assess the viability of a biofuels industry, water use must be evaluated alongside life cycle analyses, economic assessments, technical process improvements, and policies. By doing so, the full range of sustainability trade-offs can be evaluated for this industry.