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Deicing: Strategies for Safeguarding Both Guest and the Environment

by Doug Kievit-Kylar, Pollution Prevention Planner
Vermont Agency of Natural Resources

Keeping walkways safe for guests can be a challenge during Vermont's long winter months; with or without snow. Ice on sidewalks, driveways and parking lots can create hazardous conditions for people, property and the environment. Preventing the need for deicing isn't really practical unless global climate change occurs more drastically and more quickly than scientists now predict. Snow and ice removal is best done non-chemically with shovel and plow but, admittedly, the results aren't always adequate to ensure safety. Chemical deicer and/or a grit like sand is often part of a comprehensive strategy to make winter's passage a safe one.

Chemical deicers work by melting snow and ice and forming a liquid brine. This brine seeps downward to contact paved and other impervious surfaces, spreads outward breaking the bond between ice and cold surfaces, and makes it possible to physically loosen and remove whole sheets of compacted snow and ice. Used in advance of icing conditions this brine can also prevent ice from forming on surfaces.

Salt comes in several forms; sodium chloride, calcium chloride, and magnesium chloride to name but a few. Sodium chloride, or simple table salt, has been used for many years as the deicer of choice largely because of its abundance, effectiveness, and its low cost. There are, however, other costs not often factored into calculations used to determine which deicer to use. Salt poses environmental and human health risk as a potential drinking water contaminant, as a desiccant stressing salt-intolerant vegetation, and as a corrosive effecting both metal and concrete. Calcium and magnesium chloride (not sodium chloride) that is carried into the building on the soles of people's feet can seriously stain indoor carpets. Check the Internet for tips on how to best remove these stains.

According to researchers at Iowa State University, there are five chemicals commonly used as deicers. Alternative deicers claiming to be more environmentally friendly are often a combination of these five chemicals blended to minimize environmental risks while optimizing performance and cost-effectiveness. Understanding the properties of these five chemicals can help you decide which deicer best suits your circumstances (Iowa State University):

Calcium chloride (CaCl2) is available in flake, pellet, or liquid form and often outperforms other deicing products especially at lower temperatures. It produces an exothermic reaction, giving off heat as it melts. Calcium chloride also has a greater capacity to attract and retain moisture directly from its surroundings, which enables it to dissolve faster and start the melting process.

Sodium chloride (NaCl) also known as rock salt was first used as a deicer in the 1940's. It is an effective deicer for areas that receive road traffic. It draws heat from the environment rather than releasing it and it loses most of its deicing effectiveness when temperatures are below 25 degrees F. Heat generated by the friction of moving traffic on busy roadways assists rock salt's effectiveness.

Potassium chloride (KCl) is a naturally-occurring material that is also used as a fertilizer (muriate of potash) and a food salt substitute. Because of its high salt index and the potential to burn foliage and inhibit rooting, its use is relatively limited.

Urea (NH2CO NH2) is synthesized from ammonia and carbon dioxide. It is primarily used as a fertilizer. As a deicer, it has a lower burn potential than potassium chloride.

Calcium magnesium acetate (CMA) is a relatively new salt-free melting agent made from dolomitic limestone and acetic acid. It causes little damage to concrete or plants and is used as an alternative to salts in environmentally sensitive areas.

Always follow label directions when using a deicing product. However, any deicer that is mixed with equal parts of sand can help reduce the use of the deicer and provide grit for added traction. You can reduce the amount of sand tracked into the building by choosing deep tray-type doormats with stiff bristles guests can use to "clean" their shoes and boots before entering. Another removable mat placed in the reception area can help protect permanent surfaces beneath them.

Because some plants are more salt-tolerant than others, consult with your landscaper when deciding on which plants to use in beds near walkways and parking lots subject to deicing agents.

Another alternative to deicers is heated walkways. Concrete pads at busy entryways to the building can have embedded within them flexible pipes for carrying hot water. The water gives up its heat to the concrete and prevents snow and ice from accumulating. The energy costs of such a system should be taken into account when considering this novel approach.


Deicing Agents: Pros and Cons
An article by the University of Nebraska, Institute of Agriculture and Natural Resources Cooperative Extension.

Deicing Compounds and Utah Landscapes
An article by the Utah State University Extension.

Deicing Materials for Slick Sidewalks and Roads
An article prepared by Sherry Rindels, Department of Horticulture, Iowa State University.



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