A Glass of Seawater. Hold the Salt.
How eco-friendly is desalination?
At prevailing emission rates, that would send nearly 15,000 tons of carbon dioxide into the atmosphere every day. That's the same as putting almost 1 million extra cars on the road, or about 3 percent of the state's current fleet.
Desalination raises some additional environmental challenges, aside from energy use. Saline water has to come from somewhere, and some critters may call that somewhere a home. If we try to get it from the ocean, we risk killing a lot of fish in the process. Power plants, which also suck in water in huge volumes, kill billions of immature fish every year, and one study estimated that a single power plant would have the same ecological impact as eliminating thousands of acres of wild habitat.
If, on the other hand, desalination efforts focus on brackish groundwater, we risk causing earthquakes, sinkholes, and land subsidence. Eighty percent of land subsidence in the U.S. is due to groundwater withdrawal. And disposing of the super-salty runoff, which would also contain some chemicals that aid in the desalination process, risks polluting what precious groundwater still remains.
To a certain extent, there's little we can do anymore to halt near-term climate change. Desalination, then, may become a necessary tool, alongside water conservation. Fortunately, if we continue to improve desalination efficiency and runoff disposal, there's enough saltwater to last a great while.