Alternatives to rock salt

Photo: Sara Atkins
Eco-friendly de-icers

Doctors have been telling us for years that too much salt isn't good for us. Turns out, it isn't good for the environment either.

And yet, five million tonnes of rock salt is spread across snow and ice-covered Canadian roads each year, according to a 2001 Environment Canada report.

Rock salt is cheap, easy to apply and effective but it’s a real environmental threat, killing trees and vegetation, contaminating waterways and groundwater, damaging bridges and cars due to corrosion and poisoning wildlife.

It's also toxic. Both Environment Canada and Health Canada have recommended that it be listed as such under the Canadian Environmental Protection Act, 1999.

What’s worse, once salt gets into an environment, it’s there to stay. It doesn't evaporate or breakdown–it simply accumulates, compounding the problem.

How de-icers work

Simply put, a melting agent or “de-icer” lowers the freezing point of water. De-icers shouldn't be used to completely rid an area of ice or snow–they’re meant to break the bond between ice and the pavement, making shoveling easier.

But this “easy” clean-up comes at a price.

“You may see burning in your garden as high salt concentration is a real stressor for your plants,” says Andrew Laursen, assistant professor in the department of chemistry and biology at Ryerson University. "Salts are soluble, they’re mobile. They’re going to find their way into surface water and groundwater."

Understanding the options

Walk into any home improvement store during winter and you'll find a dizzying array of salt, de-icers and "natural" alternatives. So how's a consumer to choose?

"Read labels. Even if it says 'all natural,' what does that really mean?" says Emily Alfred, executive director with Toronto-based non-profit RiverSides.

Here's a rundown of some of the more common ingredients you’ll find.

  • Rock salt, or sodium chloride: The cheapest ($3.50 for $10 kg), most readily available option. It's also the most toxic and only works to minus 7 degrees Celsius.
  • Potassium chloride, or potash: Only works to minus four degrees Celsius; although it’s a common fertilizer, when used as a deicer it can actually damage vegetation (due to higher applications rates).
  • Calcium chloride and magnesium chloride: Often billed as greener options, they have a lower freezing point (minus 23 degrees and minus 15 degrees Celsius, respectively) and require less application than rock salt. But "anything with chloride in it should be avoided or used as minimally as possible," says Alfred.
  • Urea: A form of nitrogen typically used for fertilizer, but when used as a deicer its application rate is 10 times higher. Compared to alternative products, it’s less toxic to vegetation and won't corrode metal (which is why it’s often used at airports), but once in waterways, can cause algal blooms that choke the oxygen supply to fish and other organisms. Urea is five times more expensive that road salt and only works to minus five degrees Celsius.
  • Calcium magnesium acetate and potassium acetate: They don’t corrode cars or bridges, work to minus 7 degrees and minus 26 degrees Celsius respectively, and partially degrade in soil. But these “greenest” options are also 10 to 20 times more expensive than conventional ones.

Use as directed

"Try to reduce your usage of salt or alternatives as much as possible," says Kyle Vander Linden, a water resource specialist with Credit Valley Conservation.

"Use only what the manufacturer recommends or use as little as needed to melt the snow or ice on your driveway or sidewalk."

If you must use a de-icer, choose one that is made with a mixture of chemicals to prevent excess accumulation of any one compound in the environment.

Anti-icing, or using a bit of de-icer before a snow fall, helps reduce the amount of product needed. And products with environmentally benign dyes or colour agents can help prevent over-application.

On dry days, sweep up loose salt and de-icer to prevent the excess being washed into nearby waterways. And on very cold days, don’t bother applying any deicing product at all — it simply won't work.

The greenest choice

The experts agree: the greenest alternative is simply elbow grease. "The best thing you can do is really just keep your walkway clear," says Alfred. "Shovel as quickly as you can, use a broom and an icebreaker"

Fiona Wagner is a freelance writer in Marmora, Ontario.