Water consumption estimates of the biodiesel process in the US

As a renewable alternative to petroleum diesel, biodiesel has been widely used in the US and the world. However, its potential impact on water resources has not been much evaluated. This study investigates water consumption from the biodiesel process, which includes three stages: soybean irrigation, soybean-to-soybean oil processing, and biodiesel manufacturing, at both national and state levels. Mass-based allocation is performed and water consumption at the three stages is obtained on the basis of million gallons per year and gallon water per gallon biodiesel (gal/gal). The normalized water consumption (water intensity) of the irrigation, oil processing, and biodiesel production stages are 61.78, 0.17, and 0.31 gal/gal, respectively. The resulting total normalized water consumption is 62.26 gal/gal for the biodiesel process which is much lower than those reported in existing literature. It is shown that water consumption from the three stages varies significantly from state to state, which warrants the necessity of state-level water consumption analysis for better decision making in water resources management. Water consumption in potentially water-stressed states is also investigated and results show that currently these states represent 1.6 % of total water consumption associated with biodiesel production, 0.46 % of soybean harvest, and 27.61 % of biodiesel production capacity in the US.