or cracks, you just wanna toss those aside.

(engine whirring) (gentle music) - [Narrator] Salt saves lives.

When applied to icy roads in the winter, Sodium chloride prevents cars and trucks from skiing off the road or into traffic.

Salt can also be deadly.

When sodium chloride seeps into groundwater and makes its way to lakes and streams, it harms fish and other aquatic life and it's impossible to remove.

But what if plants could absorb that road salt before it gets into our water?

That's a solution University of Minnesota researchers are investigating.

(gentle music) - I heard that the roadside salt application and the pollution it causes to our twin city metro area from the radio.

And then, I started to think, you know, what can be the good way to remove the sodium chloride from our environment?

Now we have all the plants growing on the roadside.

Why not we just look into the different type of plants and see whether we can remove those, the roadside salt with the plants we have in our state.

We started this research about five years ago and we first got a couple of undergraduate students who are really interested in this work.

- My role in studying salt absorbing plants is planting different kinds of halophytes which are plants that can tolerate high salt levels and seeing how much salt they can absorb into their above ground biomass.

Because we wanna be able to harvest this above ground biomass and remove this salt from the environment.

So these plants have to be really hardy.

They ideally grow really quickly so they can outcompete these more weed like species that will grow on roadsides and take up salts effectively and not have too much maintenance while we're planting these and harvesting them.

- So, we're really at the preliminary stages of plants that might be good to take up salt sequestered in their biomass, whether it's roots or shoots.

And the idea of harvesting that material is what makes this research novel.

So, if the plant grows and dies, we just delayed when the salt ended up in the groundwater our ditches, (laughs) you know, someplace else.

- [Leif] We are researching different ways to utilize the biomass 'cause we definitely don't want to just throw it away.

So, the main kind of focus is looking at the potential for animal feed.

If you can harvest this and then give it to animals that's a high value way of using the biomass.

But then also, of course, composting and then another avenue is looking at burning the biomass for energy and then potentially reusing the salt that's in the ash.

So, if that ash has a high amount of salts then we could potentially use that again as de-icing salts.

(camera whirring) (gentle music) - We've been salting, perhaps more than 50 years and there's a consequence to, you know, that salt loading to our lives.

Sodium chloride, once it's in solution, nothing stops it.

It goes into the ground, it just moves.

We've got lakes now that are almost as salty as the ocean.

Nothing really grows in it, so if you make it salty enough it kills all sorts of things.

We know it's hard on bodies, you know, hearts and things like that.

It'd be no different than what it does to the environment.

(car whooshing) If you were to drive on any road, look for the first three to six feet.

Do the plants look weird?

And maybe they're not weird, they're just different.

And the reason they're different is that our annuals the salt killed them.

So around the university you can see where you're not supposed to put snow and where they put snow piles and today they're not normal turf grass and you're not gonna grow normal turf grass because the salt residue prevents normal things from wanting to establish and persist.

You look at a typical roadside, you've got the first flush off the shoulder and that's the space that I think is most valuable to capture salt before it even gets to the ditch.

It's the easiest to manage.

We mow it anyway.

- MnDOT has a lot of species, lists, mixes that we already know will grow pretty well on roadside.

So I would kind of look those up on the Internet and just try to find as much information as I could on their salt tolerance.

But a lot of these species, we just had to test in the greenhouse.

(gentle music) (playful music) - [Narrator] The most promising species are moved to field trials.

- The best species right now are actually sunflower and pitseed goosefoot.

The annual or common sunflower is a really good species for salt uptake.

Unfortunately it's not a perennial species.

So we're actually looking at a lot of different perennial sunflowers because we want these plants to be able to grow right when the snow starts to melt.

And it's the spring thaw because that's when the salt concentrations are gonna be the highest in the soil.

But another species like pitseed goosefoot, it's similar to a weedy species that can grow in our backyards.

It's called lambs quarters and so it's another annual but it has pretty good salt uptake.

If these plants can at least grow and then drop their seeds and then pop up really early in the spring then that can also be beneficial too.

- [Narrator] Sugar beets are also highly effective and the plants' leaves can absorb a 20% concentration of sodium chloride, but it isn't a practical crop to plant and harvest on roadsides - MnDOT's goal is to have a perennial plant mix because we don't wanna keep reseeding, we don't have the budgets.

- Think turf grass right now, is probably one of the higher potential species of perennial.

- [Narrator] Perennial plants around MnDOT stormwater management ponds are also important for filtering out pollutants.

- And if we can get plants to trap some of that it's gonna be a benefit to all of us to have less in our potential surface waters, less than in our lakes, rivers, and streams.

- Our first LCCMR project was funded for about three years and we just got continued funding for the next three years.

So the next three years will look a lot like exploring more perennials and then looking at wetland species 'cause we want to target these areas that have a lot more salts in them like rivers and lakes.

- This is hydroponic systems that I'm trying to grow some plants here.

The idea of this research is to see what kind of plants can absorb or uptake the salt from the water.

When we done with this first step, out of seven species, we gonna pick one or two, the best one.

And then after that we move with the habitat.

(gentle music) - [Bo] With our results, we will eventually give MnDOT some recommendations.

- And the whole point of this is not just to do research for research sake, it's to actually implement the results.

And that's one of the roles I play at MnDOT is to take the seed components that work and put it into standard plans standard seed mixes for counties, cities, townships, and anyone who wants to participate.

So we all benefit from salt but we should be exploring alternatives.

So this doesn't replace salt, but it's part of a series of things that we can do to lower the salt use or capture the salt we've done.

For example, alternatives would be to sweep the salt from roads between snow events and reuse it to create storm drain inlets and not put 'em under bridges or in shade, put 'em in sun and let solar heat the area so they don't create a freeze zone or a slippery zone in shaded areas.

Is there other salt alternatives that are probably less corrosive than sodium chloride?

However, they cost more money.

Sodium chloride, rust steel but there's other like mag chloride, calcium chloride, which are more expensive, but they rust different things.

Copper, aluminum, different metals also rust or oxidize away.

So, you know, everything we do has some consequence to something.

For example, potassium acetate is a really nice de-icing agent but it's also really hard on oxygen.

So when it decomposes by bacteria or fungi or algae it takes the oxygen out of the receiving waters.

One of the ways that we're reducing the salt is precision equipment placement of using the salt that's needed based on road temperature and the type of road it is.

Whether it's a interstate, you know, a state road or a county road.

It'd be more precise about the salt application.

But there's a point where you can't go any lower and still have the effects that sodium chloride provides and keeping the ice from forming and hopefully a safer transportation system.

I have children and I would really like to have something that isn't messed up.

I believe that the things we do today should be solved by the generation that caused the problem.

The only important resource we really have, there's two of them, water and soil.

(gentle music)