By Kirsten Ann Conrad, Extension Agent, Arlington County Virginia Cooperative Extension
As winter bears down on us, our hardscape (sidewalks, roads, steps, and patios) needs to accommodate the same traffic as it does in summer. However, the added threat of freezing temperatures, snow, and ice, makes it important that we manage our landscapes for both human safety and concern for the environmental impact of products like ice melt and deicers on the environment.
Deicing of hard surfaces is necessary in Virginia’s variable winter weather. The choices fall along two lines, those improving traction or those actively melting the ice. Traction improvers include common products such as wood shavings, non-clumping kitty litter, wood ashes, bird seed, coffee grounds, and sand. While environmentally feasible and basically functional, they tend to be messy and do not melt the ice. Deicing products act more quickly but the salt or fertilizer formulations have a negative environmental effect.
The five most common types of ice-melt products include the following (please note the relative toxicity and environmental impact in each description):
- Sodium chloride (NaCl) (rock salt) is most damaging to plants and contains cyanide, which is harmful to aquatic organisms.
- Calcium chloride (CaCl2) is more expensive than rock salt, but you will use only one third as much. Even in the lower prescribed quantities, it too is damaging to plants.
- Magnesium chloride (MgCl2) is less toxic than either calcium chloride (CaCl2) or sodium chloride (rock salt).
- Urea (46-0-0) is a very concentrated nitrogen fertilizer that can harm plants and is a serious risk to water quality. In recent years, fertilizer products have been recommended for ice melt purposes. These are generally either nitrogen-urea or phosphorous products and are particularly bad choices in areas with direct runoff into waterways, storm sewers and rain gardens.
- Calcium magnesium acetate (CMA) is the best overall choice for small home landscapes: less toxic than chloride deicers, but more expensive than rock salt. It is less corrosive than chloride-based products, is biodegradable, and will not harm the environment when used in small amounts. However, it is less effective in wet, heavy snow unless surfaces are treated in advance of snowfall or icing.
Organic compounds are among the newer ideas for combating ice. These include beet juice* (from the sugar beet), pickling brine, distillery, fruit, and brewery waste products. These industry by-products lower the melting point of ice and snow thereby reducing the environmental impact of salt. Several commercial products are now available combining organic wastes with MgCl2 or NaCl.
*The high carbohydrate level of beet juice may encourage the growth of algae and other aquatic organisms. Plant residues from grape, cherry, and apple processing that do not have the aquatic pollution concerns of beet juice are also being used in some areas.
Homemade pre-treatment brine is a mixtures of 23 percent CaCl2 solution that can be sprayed on hard surfaces. The basic recipe is 2.5 pounds of calcium chloride per gallon of water. Mix to dissolve and apply sparingly. See note above about use of CaCl2.
Mechanical tools like shovels and plastic sheeting are cheap, environmentally friendly, and effective. For best results shovel snow frequently to expose surfaces to sunlight; using black plastic over an icy surface can trap solar energy and speed up ice melt.
Virginia Cooperative Extension offers research-based information on all aspects of sustainable landscape management. Our local Arlington/Alexandria Master Gardeners offer one-on-one advice at our Extension Master Gardener Help Desk. Hours are 9–12 weekdays. Phone: 703-228-6414. Email us at: firstname.lastname@example.org
- Homemade brine solution for hard-surface pre-treatment: https://www.des.nh.gov/organization/divisions/water/wmb/was/salt-reduction-initiative/documents/bmp-brine.pdf
- How salt works and overview of deicing chemicals: https://stormwater.pca.state.mn.us/index.php/How_salt_works_and_overview_of_deicing_chemicals
- Using Fruit Biowaste for Deicing