As we pump gasoline into our automobiles, we watch the register ring up dollars, but we don’t see the water cost: some 13 gallons for every gallon of fuel.
It’s one of the most inconvenient truths of modern times that it takes increasing amounts of finite water to supply energy and increasing amounts of climate-disrupting energy to supply water. And too often our search for solutions to one set of challenges is making the other set worse.
This week, National Geographic News provides a comprehensive report on the recent projection by the International Energy Agency (IEA) that, if current trends continue, the volume of water consumed for energy production worldwide will double by 2035.
The recent surge in hydraulic fracturing, or “fracking,” to unlock shale gas plays a part, but the big-ticket items in the equation are coal-fired electricity and the expected rise in biofuel production.
According to the IEA’s assessment, in 2035 biofuels could account for 30 percent of the water consumed for energy production, up from about 18 percent in 2010. The water-intensity of biofuels varies greatly depending on the fuel stock — corn, sugar cane, or agricultural byproducts — as well as on how and where that fuel source is grown.
According to a 2009 study in Environmental Science & Technology, the 2007 U.S. Congressional mandate to produce 15 billion gallons of corn ethanol a year by 2015 would annually require an estimated 6 trillion liters of additional irrigation water (and even more direct rainfall) – a volume exceeding the annual water withdrawals of the entire state of Iowa.
Flipping the water-energy nexus coin, we find that more and more water “solutions” demand more energy – whether pipelines to transfer water hundreds of miles from one place to another or desalination plants. Though the energy costs of desalting have come down in recent decades, it still takes about 2 kilowatt-hours of electricity to produce one cubic meter (264 gallons) of drinkable water.
The good news is that saving energy saves water, and saving water saves energy. And we’ve barely begun to tap the potential of conservation and efficiency improvements to meet new needs.
Now more than ever, real solutions are those that tackle our water, energy and climate problems at the same time.
[For additional information and examples, see the Know the Nexus report by GRACE Communications Foundation. To calculate the water cost of your energy use, try our National Geographic water footprint calculator.]
Sandra Postel is director of the Global Water Policy Project and Freshwater Fellow of the National Geographic Society. She is the author of several acclaimed books, including the award-winning Last Oasis, a Pew Scholar in Conservation and the Environment, and one of the “Scientific American 50.”