Biofuels and the Energy-Water Nexus: Perspectives for the United States

This study provides an assessment on the production of biofuels, such as ethanol and biodiesel, and the energy-water nexus in the United States. Transitioning the transportation sector to low carbon sources will require the use of both electricity and sustainable biofuels. A total transition to electricity could take several decades, given the size of the transportation fleet and front-end costs. Moreover, some parts of the transportation sector, such as aviation and shipping, may rely on biofuels (e.g., biokerosene and biodiesel) for an extended period due to technology barriers to using electricity. Therefore, under most future scenarios, biofuels will continue to play an important role in reducing transportation sector greenhouse gas emissions. Both biofuels and thermoelectricity generation have a significant water footprint associated with their production cycles [1]. As electricity and biofuels gain a larger share of the transportation fuel market, the cumulative impact on water resources must be considered [2]. As shown in Figure 1, water use for thermoelectric power represents the largest share of the total water withdrawal in the U.S., followed by irrigation for crops [3]. Figure 2 shows the use of water in different stages of corn growth, whereas Figure 3 shows the current corn production areas. Thus, with or without biofuels expansion, water supplies must be a central component for both energy and agricultural planning.