Measuring ecological impact of water consumption by bioethanol using life cycle impact assessment

Though the development of biofuel has attracted numerous studies for quantifying potential water demand applying life cycle thinking, the impacts of biofuel water consumption still remain unknown. In this study, we aimed to quantify ecological impact associated with corn-based bioethanol water consumption in Minnesota in responding to different refinery expansion scenarios by applying a life cycle impact assessment method. This ecological damage assessment method for quantifying water consumption impacts was proposed by Pfister et al. in 2009 (Environ Sci Technol 43: 4098-4104, 2009) using an impact characterization factor integrating terrestrial net primary production and precipitation. In this study, we derived the spatially explicit eco-damage characterization factors for 81 watersheds in Minnesota and compiled location-specific water consumption data for all current and planned bioethanol production facilities and feedstock production. The ecological damage caused by bioethanol production (Delta EQ(EtOH) in m(2)a <...yr) was then calculated on both watershed and refinery-plant levels. Additional refinery expansion scenarios were established for testing the effectiveness in changing Delta EQ(EtOH). The results show that ecological impact Delta EQ(EtOH) varied by more than a factor of 3 between watersheds. Minnesota consumed 40 billion liters of water to produce 2.3 billion liters of ethanol as of 2007 (17 L water per liter of ethanol). The geographical distribution of Delta EQ(EtOH) was shown to be uneven with a cluster of high-impact regions around the center of the state. The planned refinery expansion is expected to increase the state's corn ethanol production capacity by 75% and Delta EQ(EtOH) by 65%. However, strategically locating the planned expansion in the low-impact areas is expected to minimize the increases in Delta EQ(EtOH) down to 19% from 65%. The scenario analysis shows that strategically sourcing corn from low-impact regions can result in significantly less water use impact compared to a baseline scenario. The results indicate that employing the water consumption impact assessment can provide additional insights in policy making. The environmental impacts related to the change of plant infrastructure and agricultural practices associated with the development of the renewable energy industry should be considered as well for identifying the most sustainable alternatives.