One of the biggest challenges scientists and engineers face is coming up with solutions to our environmental problems that make sense to everybody. Whether the problem is preserving habitat for cave spiders, keeping fertilizer chemicals out of the frog pond, or making sure we don't disintegrate the atmosphere with our hairspray, scientists and engineers have to come up with a plan that keeps both humans and the environment happy. Keeping humans happy means their solution needs to be cost effective, which means the benefit of the solution has to be worth the cost.

Of course we're talking about the Benjamins when we talk about cost effectiveness, but we're also talking about the kinds of costs we can't put on a credit card. Like, does the solution ruin a habitat for nesting birds? Does it make a loud, steady whirring noise that feels like it's eating our brains? Does it completely block everyone's view of the beach? Does it produce an odor like a mix between sweet potatoes and sweaty feet? These are all examples of "costs" that scientists have to navigate as they come up with their solutions.

As an example, here's a pretty big problem: fresh water. Fresh water is pretty important to survival and, um, showering, but isn't always so easy to come by. We do, however, have plenty of salt water sloshing around the planet, so scientists have been working on a solution that could turn some of that salt water into useable fresh water.

The first thing scientists had to figure out was, is it even possible? The short answer is yes. It's totally possible to get the salt out of water. In fact, you can even do it at home. Just mix up some salt water, throw it in a pot and boil it. The steam that rises is plain old water, so you just have to boil water, rig up a contraption to collect the steam, let the steam cool, and you've got yourself a refreshing glass of salt-free water. Easy peasy, right?

Sure it's easy—if you're trying to get enough water to keep a mouse hydrated. Imagine trying to supply water to an entire city that way. Not so easy anymore. Scientists figured out that the best way to do this on a large scale is to use vacuum distillation or reverse osmosis. You can check out the details if you're interested, but just know that they're kind of involved processes that use up a lot of energy for how much fresh water they make. Like, a lot of energy. The energy used to desalinate 100 million gallons of water is enough to power 28,500 homes.¹² Yikes.

Either way we attempt to get the salt out of the water, we're using energy. Aside from costing money, energy also tends to result in pollution, unless clean or renewable options are being put to work. We have to use chemicals to make these processes work, as well as protect the equipment from the damage salt water can cause. And then there's all the leftover salt. Dumping this stuff directly in the ocean can really bojangle the delicate balance of ecosystems down there.

At this point, the amount we would spend on electricity and the pollution we would create to get this process going outweighs the benefit of having the fresh water, so it's not really a viable solution to our parched problems. However, scientists have never let something like this defeat them before. Desalination plants have already been built and are cranking out freshwater for some coastal cities in California in Florida. Scientists are also continuing to research and experiment with different materials and processes to see if they can find a way get rid of the salt and keep the dough without harming the environment.