Navigating an icy road can be pretty dangerous.

And while applying a coating of  salt is the time-tested method for rendering a frozen highway  drivable, that salt has major downsides. It’s toxic for plants, wildlife  and freshwater ecosystems.

It contaminates our drinking  water and air quality. It can even damage our cars, which,  like, feels a bit counter-productive. So, how do we make winter roads safe  for both drivers and the environment?

Well, science says we have options. [♪ INTRO] Salting a road is by far the  most common de-icing technique. When salt mixes with water, the resulting solution has a lower freezing temperature  than water by itself. However, this is true for all kinds  of solutions, not just salty ones.

Thanks to a scientific principle  called freezing point depression, the temperature at which  plain H2O freezes is always higher than its freezing point when  something is dissolved into it. Essentially, the salt keeps water  molecules from forming solid ice crystals because the salt interrupts  the watery ice structure. The temperature at which the  salty water eventually freezes depends on how salty the solution is.

And although salting roads with the  classic sodium chloride is effective, it wreaks havoc on plants and wildlife,  contributes to poor air, soil and water quality, ruins infrastructure like water  treatment plants and bridges, and corrodes our stuff (like the steel in cars). Which is why some places are experimenting with a few solutions to this chilly conundrum. We can start simple: even a different  kind of salt can make a difference!

The sodium chloride you put on your food  is chemically the same as the rock salt, or halite, that's spread on roads to melt ice. It's cheap, effective, and the infrastructure for delivering it to roads is already in place. The problem is that the  chlorides in the sodium chloride don't ever break down in the environment.

But other salts are better for the environment, if only because less is required  in solution to achieve the same freezing point depression we get with a  higher concentration of sodium chloride. Remember, a salt is just any compound  that has positive and negative ions, which together make a neutral charge. There are a lot of options  for what salts you can use.

For instance, magnesium  chloride and calcium chloride lower the freezing point more effectively  due to some interesting chemistry. When sodium chloride dissolves in water,  it dissociates into two ions: Na+ and Cl-. Magnesium chloride and calcium  chloride, on the other hand, dissociate into three ions  each, since they’re each made of three total atoms instead of the two in NaCl.

And because the number of  dissolved particles in a solution is what determines how low the  freezing point of a solution can get, salts like calcium chloride can do  the same job as sodium chloride, while using less raw salt to do it. Some states like Connecticut have used  magnesium chloride salts for de-icing, citing the lower cost of the solution. However, there is a downside: they’re  still somewhat corrosive to cars, making them less than ideal.

And these salts are also bad for the  environment when they accumulate; it just doesn't happen as  fast as with sodium chloride, because less is needed to do the job. Figuring out which ions react with  what can be a major chemistry puzzle. And you can find more of those at  Brilliant, the online learning platform with thousands of lessons in  science, computer science, and math, and the sponsor for this video.

Their Chemistry and Biology Puzzles  course takes interactive learning to the next level with 28 quick lessons  full of puzzles that keep you engaged. Some of those puzzles cover the  basics of chemical reactions that can help you follow along with all of the  ions I just rattled off, while others pose environmental questions for things  like finding a cleaner burning fuel. You can try them all for free for  30 days at Brilliant.org/SciShow or by clicking the link in  the description down below.

That link also gives you 20% off an  annual premium Brilliant subscription. So, if your ears perked up at the  mere mention of the environment, just wait until you hear about  this next de-icing alternative. Of course, there are other options  beyond salts for de-icing roads.

Some state road agencies have  tested all kinds of weird stuff: cheese brine, pickle juice, beet  juice and pig pee, to name a few. Welcome to the wild world of potentially  eco-friendly methods for melting road ice! Byproducts from vodka distilleries or  sugar beet processing facilities contain a lot of sugars, which, when added to  road salts, helps lower the melting point of the ice, meaning the salt will work  better at even lower temperatures.

But not all eco-options are created equal. For instance, some communities have  complained about the smell from that beet wastewater, and some research  shows that distillery byproducts can also cause some of those ecosystem  problems that we’re trying to avoid. Urea is also marketed as an eco-friendly  solution to road salt, since it’s also water-soluble and makes a solution with  a lower freezing point than pure water.

And while urea is great at  de-icing and is generally safe for pets and children to be around,  there are some downsides. It doesn't perform well below - 4 degrees  celsius and once it gets into a waterway, it decreases dissolved oxygen  and causes algal blooms. ~ Plus, urea is actually somewhat expensive, at least compared to the other options out there. Still, there’s definitely a market for more  of these less harmful options for de-icing.

The other way to help de-ice our roads  is also the way to make pickles - brine. But I’m not talking about  your leftover pickle juice! Brine is just water that’s got a lot of  salts dissolved in it, and using brine on the roads is a pretty neat way to prevent  the ice from forming in the first place.

When you de-ice a road that's already  been snowed upon, transportation agencies use wet rock salt to break the bond between the ice and the road, making it safer to drive. But the idea behind the brine is to apply  liquid salt to the road ahead of time. Some places have started brining the roads with liquid salt solution before  the snow or ice shows up.

This limits the amount of ice that  can form on the road to begin with, and uses about a quarter of the salt of de-icing. Brining requires a lot of infrastructure  and planning; a community needs trucks with big tanks and pumps to spray  the brine onto the pavement surface. This stuff can be expensive.

However, communities that have  invested in brining roads have reported reducing the overall cost of maintaining  winter roads, even after accounting for the extra equipment and staffing. And the reason for the savings is simple:  they're just not buying as much salt! So, while nothing is perfect, there are  absolutely some ways we can move ahead on making our roads safer and more eco-friendly.

Let’s just hope they don’t all smell like pig pee. Thanks for watching! [♪ OUTRO]