In the United States, national security, environmental, and economic concerns drive an interest in alternatives to petroleum that are domestic, low-carbon, and sustainable. Fuels that receive significant policy support include corn-based ethanol, natural gas, methanol, or electricity. However, many alternative fuels are more water-intensive than conventional petroleum-based fuels such as gasoline and diesel.1C. W. King and M. E. Webber, “Water Intensity of Transportation,” Environmental Science and Technology 42 (2008), 7866–7872. For example, more electric vehicles on roads indirectly increases water use for power plant cooling. In 2005, petroleum-based gasoline required about 950 billion liters (250 billion gallons) of water to produce 530 billion liters (140 billion gallons) of fuel. Switching to ethanol from corn—with just 15% of the crop requiring irrigation—requires over 3.75 trillion liters (1 trillion gallons) of water per year within two decades.2C. W. King, M. E. Webber, and I. J. Duncan, “The Water Needs for LDV Transportation in the United States,” Energy Policy 38 (2010), 1157–1167. Just a small irrigated fraction of the biofuels mandate will increase water consumption for light-duty transportation by a factor of four or more.
Adding expectations for other fuels such as cellulosic ethanol, coal-to-liquids, and other sources, requires another 3.75 trillion liters (1 trillion gallons) of water. Because annual water consumption in the United States is about 136 trillion liters (36 trillion gallons), an additional 7.5 trillion liters (2 trillion gallons) or more per year significantly increases water consumption. The Environmental Protection Agency’s Renewable Fuel Standard program and incentives for electric vehicles are examples of energy policymaking that ignores water impacts.