My local supermarket carries a dizzying variety of salt—"hand-harvested" sea salts, kosher salt, plain-old table salt, etc. Are any of these salts more eco-friendly than the others?
Gourmands and health nuts love debating the advantages of various types of salt, but environmentalists have typically been more concerned about the kind we apply to our roads than by the stuff on supermarket shelves. Some types of food salt are made in ways that are easier on the planet—but by the time they get to you, the benefits may have vanished.
There are two ways to get salt: from the earth or from naturally occurring saltwater. Most of the common table salt sold in the United States is produced via solution mining, which involves digging a well deep into an underground salt deposit, pumping in water to dissolve the salt crystals, and then drawing the brine back up to the surface. The process is pretty mild, as mining operations go, since it doesn't produce much noise, airborne pollutants, or groundwater contamination. (The worst-case scenario would be a cave-in, although that's highly uncommon.) At the processing facility, the salty solution is fed into a machine that resembles a giant pressure cooker and that evaporates most of the water; the resulting slurry gets spun and heated until the salt is completely dry. This method—known as vacuum pan refining—is the most costly and energy-intensive way to make salt, but it creates a very pure product that's nearly 100 percent sodium chloride. (You can also get edible salt the old-fashioned way—by physically mining it out of the earth in its mineral form—but in the United States, most of this rock salt is used for highway ice removal.)
The other way food salt is made is by solar evaporation, in which seawater (or briny lake water) is pumped into a series of large, shallow ponds and left to evaporate naturally. The process is very slow—it can take years for the sun and wind to turn saltwater into crystals you can scoop up and package—but it has a clear environmental benefit in that it requires very little fossil-fuel input. With large-scale operations, wildlife issues may come into play: Supporters say the ponds can provide sanctuary for certain wetland species, like flamingos and other birds (PDF); however, environmentalists have successfully protested the establishment of industrial saltworks in parts of Australia and Mexico on the grounds that they could disrupt existing ecosystems at sea and on land. The liquid that remains after the solar evaporation process—known as bitterns—also requires special consideration, since in large, concentrated amounts it can be harmful to fish and other aquatic organisms (PDF).
Some solar sea salt is then washed and refined in a process that can be as energy-intensive as vacuum pan refining. But most gourmet sea salts are harvested from the evaporation ponds—sometimes with hand tools—and then treated very minimally before they're packaged and sold. (At larger operations, the salt is gathered using special tractors equipped with scrapers on their front ends.) So at least in terms of energy use and greenhouse gas emissions, those high-end salts would indeed seem to be more eco-friendly than the common variety.
Of course, the flip side is that the fancy stuff may have traveled a long way to get to your neighborhood Whole Foods. At the moment, most artisanal salts are produced outside the United States,while regular table salt generally comes from domestic sources. Figuring out whether the savings on the production side are enough to cancel out the impacts of the longer journey would require a lot of data collection and number-crunching. Either way, packaging could make a big difference. Many gourmet salts are sold in small glass bottles. As we discussed before with regards to beer containers, glass is heavy and makes for more expensive transportation—and greater emissions of greenhouse gases.
What about kosher salt? As with meat, the kosher designation alone doesn't make a difference when it comes to environmental impact. Kosher salt can be extracted via solution mining or from seawater and processed via vacuum pan refining or solar evaporation. What makes salt kosher—or, more precisely, suitable for use in the process of draining the blood from a kosher piece of meat—is the size of the particles. Either the salt is raked during the refining phase so that the pieces come out larger and coarser or producers simply sift out naturally occurring smaller granules, which are then sold as table salt or else molded into things like water-softening tablets and animal feeding blocks. So there's no reason that kosher salt should be better for the planet than regular-old table salt—though it does make for a nice rim on your margarita glass.
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