By Eugenia Vlasova, Edited by Barb Seegers
Beautiful, spring-like days in the middle of January are a great relief for winter-tired people and their pets. While I was enjoying one of those days, and walking with my furry friends, I noticed a problem that had been buried under the snow for weeks — an ice melter that I had been using on my driveway had now burned the lawn. When I shoveled snow off my driveway, the salt that remained on the pavement mixed with the snow. Then, when temperatures began to rise, the snow melted and absorbed into the soil, leaving the grass yellow and pretty much dead. As the warning signs in the buckets of my ice-melter suggest, those chemicals may irritate eyes and skin and can be harmful for pets. Is there anything we can do to reduce the environmental impact of ice-melters? Let’s discuss that shall we?
How Ice Melters Work
As you may have learned in school, under normal conditions water freezes at 0° C or 32° F. Dissolving additives, such as various kinds of salt, lowers the overall freezing point of water. I asked Stephen Merkel, an engineer and chemistry expert on Quora, about ice-melters, and this is what he said:
Pure water is easier to freeze than water with a bit of any chemicals dissolved in. The amount that a given chemical lowers the freezing point is called the freezing point depression. There are a number of different salts, which dissolve easily in the small amount of liquid water on the surface of any piece of ice(pretty much all ice has at least a few molecules of liquid water at the surface or water behaving somewhat liquid like). This highly concentrated solution, then has a lower melting point, which if it is lower than the outdoor temperature, will cause more ice to melt at the interface, until the freezing point depression matches the temperature, or all of the ice is melted.
So, when we pour ice-melters on the driveway, we do not actually melt the ice. You can read what temperatures are good for your specific ice-melter on the label, and if it is colder than that, pouring the ice-melter won’t do the job.
Different types of ice-melters contain different chemicals, and different additives are more effective at different temperatures. For example, Potassium Chloride (KCl) and urea ((NH2)2CO) lower the freezing temperature of water to -4°C (25°F), which means they are more useful as fertilizers rather than ice-melters. Rock salt, also known as Sodium Chloride, lowers the freezing temperature of water to -7°C (20°F) and is ineffective when it is colder than that. Magnesium Chloride (MgCl2) works at temperatures as low as -18°C (0°F), but it is more expensive than most chemicals. Many municipalities prefer Calcium Chloride (CaCl2) which is effective to -32°C (-25°F) and acts faster than other salts. Typically, ice-melt mixes, that you see on shelves, are just blends of all of those, only with varying proportions between brands.
Though very common, salt-based ice-melters are very corrosive and, just like typical table salt, may damage skin and pavers, and are dangerous for plants. The expression “don’t rub salt on an open wound,” is very accurate because we know how much pain it causes to do so. Salt is painful for animals too. If they have cuts or cracks on their paws walking on salt could be excruciating. While many pet owners wash, or at least wipe, the paws of their pets after each walk, wild and stray animals may suffer greatly from salt-pickled roads and driveways.
Reducing the Environmental Impact
Abstaining from using ice-melters is not really an option, because broken and fractured limbs aren’t much fun. How can we reduce the hazards associated with ice-melters? Here are a few suggestions:
- Do not overapply ice-melters – follow the instructions on the label and apply only when and where needed
- Shovel and brush off the snow before applying ice-melters – you’re not trying to melt the snow but melt the ice under the snow
- Sometimes all you need is a little traction – environmentally neutral sand may provide the traction needed
- If sand doesn’t work well enough for you, perhaps try blends that contain less salt, but have potassium chloride instead and limestone for traction. Those blends are less harmful for your skin, as well as for animals and plants
- In spring, flush the area where you applied ice-melters with plenty of water – the more diluted the salt concentration, the milder the effects on plants
- Give non-salt based ice-melters a try — they may surprise you
Pet stores in Canada sell pet-friendly salt-free ice-melter called ‘Safe Paw’. According to the manufacturer, ‘Safe Paw’ is a “modified amide with glycol admixture”. As I learned from a wonderful article at Now, this is just “modified urea in a polypropylene glycol base”.
Stephen Merkel said,
Crystalline amide is basically saying some form of plastic. More than likely, the amide is not actually true nylon, but some amide blend that is a plastic that dissolves in water. An example of this is the plastic used in pool shock bags, which dissolves fully into the pool water. Glycol admixture, is antifreeze. Propylene glycol is sometimes used as an antifreeze, but is also extremely hydrophilic, so it is used to hold water in baked goods occasionally. (Don’t worry it is non toxic, and FDA approved as a food additive). Glycol works the same way as the salt, dissolving into the water, and causing a freezing point depression. The claims that this provides a shield for a few days after applying, is probably due to the plastic polymer causing the glycol to tend to stick to whatever hard surface it was applied to, at least until a fair amount of water rinses it off.
Using ice-melters with moderation is a good idea, not only for stray cats that occasionally cross your driveway, but also because your car won’t corrode as quickly. In the spring, you’ll have to invest less time and money into reviving your lawn. All in all a win-win for you, your pet and the planet!
Image by MixedGrill.