Wells to wheels: water consumption for transportation fuels in the United States†
The sustainability of energy resources such as transportation fuels is increasingly connected to the consumption of water resources. Water is required for irrigation in the development of bioenergy, reservoir creation in hydroelectric power generation, drilling and resource displacement in petroleum and gas production, mineral extraction in mining operations, and cooling and processing in thermoelectric power generation. Vehicles powered by petroleum, electricity, natural gas, ethanol, biodiesel, and hydrogen fuel cells consume water resources indirectly through fuel production cycles, and it is important to understand the impacts of these technologies on water resources. Previous investigations of water consumption for transportation fuels have focused primarily on key processes and pathways, ignoring the impacts of many intermediate, inter-related processes used in fuel production cycles. Herein, the results of a life cycle analysis of water consumption for transportation fuels in the United States using an extensive system boundary that includes the water embedded in intermediate processing and transportation fuels are presented. The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model provides a comprehensive framework and system boundary for transportation fuel analysis in the United States. GREET was expanded to include water consumption and used to compare the water consumed per unit energy and per km traveled in light-duty vehicles. Many alternative fuels were found to consume larger quantities of water on a per km basis than traditional petroleum pathways, and it is therefore important to consider the implications of transportation and energy policy changes on water resources in the future.