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The Least Toxic Way to Melt Snow and Ice

We had the season’s first real snowstorm this weekend, and we weren’t really prepared for it. I didn’t even know where our shovel was! We also didn’t have any salt for the front steps, so I took this opportunity to find out if we could get something that had less of an impact on the environment.

From what I can tell, there’s no truly environmentally friendly way to melt snow and ice. The two main materials people use—rock salt and calcium chloride—are both bad; it’s really just a choice of which is better. Along with many others, the City of Cambridge recommends using calcium chloride rather than rock salt or sand. (Ironically, the city also provides rock salt free of charge.) Many de-icers are a combination of multiple ingredients, so check the label. Here’s what I could find in local stores:

Calcium Chloride – CaCl2

  • can be used in smaller amounts (a handful per three square yards)
  • works better than rock salt at temperatures below 20 degrees Fahrenheit
  • increases salinity of waterways

Rock Salt – NaCl (Sodium Chloride)

Magnesium Chloride – MgCl

Urea – (NH2)2CO

Sand (Or Kitty Litter, Ashes, etc.)

  • clogs sewers
  • increases sedimentation in streams
  • increases turbidity, reducing water quality and potentially killing fish and aquatic plants
  • makes hard ice more slippery
  • doesn’t melt ice

Calcium magnesium acetate and potassium acetate are two promising de-icers, but they’re generally used only for large-scale use or as additives to rock salt. Not a solution for home use.

Since all ice melters have adverse effects on the environment, the best thing we can do is use less of them. To me, this means that calcium chloride is the way to go. It’s more effective in smaller amounts, and, if I could find the colored kind (I couldn’t around here), I’d be able to see the coverage and use less of it.

Keep in mind that this is not supposed to take the place of shoveling, just prevent the skim that forms on wet sidewalks or break up the ice so we can shovel it away. That crunch under your feet is an indication that someone used waaay too much.

Cross posted on the Cambridge Energy Alliance blog.


Comment from Jenn
Time December 21, 2009 at 10:29 pm

…but ash is FREE!…and natural…and…well, if you’re burning wood at your house, you’re all ready creating it and it’s gonna be making it’s way to a stream eventually anyway….

I do agree with CaCl for you city people who don’t have wood heat though! ; P

…and although ash is less effective, I am glad that we are able to use it for something, aside from just dumping it out back…

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Time December 22, 2009 at 8:45 am

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Comment from Brenda Pike
Time December 22, 2009 at 9:22 am

Yeah, not many people burning wood in Boston. 🙂

This has got to be an especially tough problem for you guys, since you’re right next to that stream. I have no clue what’s recommended to do with ash. I know that you’re not supposed to use much of it in the garden (if at all) because it will raise your soil’s pH.

Comment from Danielle
Time December 23, 2009 at 2:12 pm

I’m grateful that my current landlord got an extremely enthusiastic snow-removal surface… as opposed to the previous landlord, who had the downstairs neighbors clear the huge driveway with a rickety diesel snowblower, which meant I often helped shovel for hours… but oh man, it’s like the Dead Sea dehydrated on my steps. Horrifying piles of salt. I keep having to sweep the kitchen. I hope not enough gets in to hurt my cat.

Comment from Danielle
Time December 23, 2009 at 2:13 pm

SERVICE! Jeez. Time to take a few days off!

Comment from Brian B
Time December 24, 2009 at 1:51 am

Urea- Does that mean I can just pee on the ice and it will melt? I’m going to start peeing on the front steps to melt the ice. I use a combo of ash and rock salt. The ash absorbs water that has melted so it doesn’t refreeze and also allows the sun to melt the ice. Small amounts of ash can actually benefit the garden by neutralizing acidic soil (not good for strawberries, but good for other plants)

Comment from Brenda Pike
Time December 24, 2009 at 7:08 am

Pee would definitely melt it–but I doubt your wife would be pleased!

I’d always thought ash was really good for gardens, but apparently if too much is used it can raise the soil’s pH too high. It sounds like ash should be used sparingly and only if the soil’s pH is below 7.0. I had no idea!

Comment from Brenda Pike
Time December 24, 2009 at 7:10 am

We caught Oliver trying to eat a piece of rock salt that came in on our boots yesterday. It’s just the right size and shape for him to mistake it for kibble.

Comment from greenmomintheburbs
Time January 2, 2010 at 8:55 pm

Interesting! We use something called “Safe Paw” (we have pets) that looks like it’s carbonyl diamide, which is the same as urea, but it has something in it that prevents the nitrates from leaching out into the water supply…

It’s sort of a no-win situation, isn’t it? Sigh…

Comment from Brenda Pike
Time January 2, 2010 at 9:00 pm

It really is! I passed on Safe Paw because of the urea. What in it is supposed to prevent the nitrites from leaching? I can’t find that claim on their website.

Comment from Alden Rickman
Time March 10, 2010 at 12:39 pm

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Comment from Brenda Pike
Time March 11, 2010 at 10:03 am


Comment from Judy Ricker
Time November 15, 2010 at 8:35 am

I just read somewhere to use Dawn dishwashing liquid mixed with water don’t know if it would work or freeze more! Going to try some next time steps are icy!

Comment from Brenda Pike
Time November 15, 2010 at 9:42 am

I’d be afraid that it would make the steps really slippery. Don’t fall!

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