An interesting article has recently been published in an open-access journal called “Environmental Research Letters.” I’m torn on open-access journals: people should have access to research results, but the quality of publication suffers without higher quality reviewers. That said, this article seems pretty informative. The authors attempted to quantify the energy used in the US in 2010 for treating and delivering water, and they found a whopping 12.6% of energy consumption in the US is due to water.
I found this figure instructive, showing the difference in energy requirements for various types of water sources and treatment levels. Note the difference between desalted water and normally treated water is large, but the difference between desalted water and the California State Water Project water (which is pumped from the Bay-Delta to southern California) is small. No wonder southern Californians are getting more excited about seawater desalination and water recycling, assuming that cost scales with the energy intensity of the water source.
With some pretty complicated flow diagrams, the authors come to one very striking conclusion:
We estimate that 5.4 quads of this primary energy (611 billion kWh delivered) were used to generate electricity for pumping, treating, heating, cooling and pressurizing water in the US, which is approximately 25% more energy than is used for lighting in the Residential and Commercial sectors . (Despite this equivalency, much more policy attention has been invested in energy-efficiency for lighting, rather than reducing hot water consumption or investing in energy-efficient water heating methods, even though the latter might have just as much impact.)
In other words, reducing hot water consumption or investing in energy-efficient water heating methods could have a similar impact to switching our personal lightbulbs to compact fluorescents, yet there has been no policy push to educate people on this aspect.
Results like these are fascinating and instructive. Once we know where the energy is going and how much our water really “costs”, we can make adjustments that make sense without revamping the whole system. You and I can be more energy efficient by taking shorter showers and turning water off while lathering up with soap and shampoo. California can promote water recycling in southern California instead of desalination and increasing imported water, which would save on energy without cutting off the State Water Project. I’m sure many more examples of efficiency improvements are available — we just have to think a little outside the box.