Desalination Will Not Solve Our Water Problems

Poseidon Desalination PlantAs many of you know, I live here in the Bay Area of California — you know: the good part. And we are in the middle of the worst drought since well before the rise of the Aztec Empire. So we are looking very seriously at building a greywater system. For those of you who don’t know, greywater is wastewater that comes from pretty much everywhere but your toilet. For example, your dishwater is greywater. You wouldn’t drink it, but it is fine for other uses like watering your plants or for your toilet. It’s all about efficiency: using the water that you have the best way you can.

But whenever the subject of drought comes up, there is always someone who brings up desalination. We’ve got great big oceans. Why not just pull the salt out of it and give it to our cows? People like this idea because we have a long tradition of fixing problems via technology. But there is a general problem with this outlook on life: we have a statistically skewed sample to draw from. We are, after all, the people who survived. Human history is filled with climate changes that wiped out whole regions. And now that we humans are everywhere, we have the potential to wipe ourselves out on a global scale. Will there be “one weird trick” that will save us?

The best solution to our water problems was for us to take global warming seriously starting back about thirty years ago. But given that we can’t even take it seriously today, that is a fanciful thought. And most likely, the solution to the problems associated with global warming will be to combine a lot of different approaches. And desalination will probably be part of that mix. But it certainly isn’t a cure-all. There are many problems with it — and just as many limitations.

As Michael Hiltzik noted “desalination plants can’t be plunked down just anywhere…” The new billion dollar Poseidon plant rejected three other locations before deciding on Carlsbad where it is close to the Encina Power Station. This made it easier to get the energy that it needs and also reduced the environmental impact, since the power station is already doing that. Poseidon’s continued usefulness will depend upon Encina continuing to run (although it is a good bet at least for the foreseeable future).

The biggest problem with desalination plants is that they use a lot of energy. Of course, so does transporting water large distances. The most efficient desalination can actually use less energy. And one would hope over time that this will be more generally true. So sorry Captain Kirk, the pipeline ain’t the way to go. But still, desalination is expensive. According to Hiltzik, one acre-foot (325,851 gallons) of water from Poseidon will cost about $2,200. “San Diego currently pays $923 per acre-foot for treated water from the Metropolitan Water District. The Pacific Institute reported in 2012 that San Diego could obtain recycled water for as little as $1,200 per acre-foot, and that the marginal cost of water obtained through conservation and efficiency measures was as little as $150.”

A direct example will help. Desalination can be as cheap as (pdf) 3 kW·hr/m3. But it is more normally 4-5 kW·hr/m3. Compare this to pumping it out of the ground which costs less (pdf) than 0.2 kW·hr/m3. That makes groundwater at least 16 times cheaper. And this doesn’t take into account the fact that, for example, the Carlsbad facility will be using all hydrocarbon power, which adds to global warming.

Another problem with desalination is that it has other environmental problems. At the start of the process, “Ocean inflows suck up and kill larval marine organisms.” What’s more, all the salt that is taken out of the water must be put back into the ocean — creating areas that are super-salty. This has large environmental effects, at least on a local scale.

I’m not suggesting that desalination should not be pursued as a tool to fight against the many problems that global warming in causing us to face. But it isn’t the cure-all that many people think it is.

2 thoughts on “Desalination Will Not Solve Our Water Problems

  1. AND, on a related topic, de-grassing every surface and covering it in plastic or cement only contributes to poorly managed run-off and eliminates large portions of transpiration. Transpiration is an important part of the hydrologic cycle. The less water that goes into the sky, the less water there is to come down. Evapotranspiration is the collective term for water transpired by plants (yes, those scraggly grasses and weeds) and water evaporated from surfaces. When water runs off and is channeled, the reduced surface area reduces evaporation and further reduces atmospheric release of H2O.
    Yes, stop wasting potable water on your lawns, but don’t cover land with plastic and cement either.
    Another northern Californian.

    • Yeah, there are a lot of elements to it. It’s fascinating stuff. The water cycle, like the carbon cycle, is really complicated. Our question now isn’t so much rain as where it will fall. And the answer seems to be: not over California.

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