Sodium chloride (road salt) is commonly used to control snow and ice on roadways and sidewalks. Though effective and affordable, sodium chloride presents problems for ecosystems and infrastructure. After melting ice and snow, sodium chloride can enter local waterways, threatening drinking water as well as fish and other aquatic organisms. It can also contaminate soil and plant life and cause corrosion to paved surfaces, buildings, and metal – including vehicles and interior flooring. Best practices for snow and ice control – such as mechanical controls, pre-wetting salt, and collecting residual salt and sand to prevent it from entering water supplies – can reduce the negative impact of sodium chloride, but purchasers should also consider environmentally preferable products.
Snow control and deicing products are purchased in bulk by transportation departments for use on major roadways. They are also purchased pre-packaged for smaller applications, such as steps, sidewalks and parking lots, by property owners and maintenance staff. Environmentally preferable products include chloride products with corrosion inhibitors and alternatives to chloride-based products, such as agricultural-based pre-storm coatings and calcium magnesium acetate.
Design for the Environment (DfE) is an EPA program that distinguishes chemical products such as deicers that are safer for human health and the environment. The Pacific Northwest Snowfighters (PNS) is an association of transportation agencies dedicated to ensuring the safety of winter maintenance products through structured testing and evaluation and has developed specifications to guide transportation agencies in the selection of chemical products for snow and ice control.
Acetate-based deicers (such as calcium-magnesium acetate and potassium acetate) are non-corrosive and usually biodegradable (whereas chloride-based products persist in the environment). For example, calcium magnesium acetate (CMA) is a natural acid, soluble in water, with chemical properties similar to vinegar, available for applications both large scale (roads and airport runways) and small scale (sidewalks). Compared to chloride-based products, acetates are expensive, but cause minimal damage to roads, vehicles, and vegetation and their lower freezing point makes plowing and shoveling easier in colder temperatures. However, they can contribute to eutrophication (e.g., algae blooms) and oxygen depletion in water supplies.
Plant-based snow and ice control products can be used to slow down the formation of ice, prevent ice from bonding to pavement, or make road salt (or other conventional deicing chemicals) more effective at lower temperatures (by pre-wetting it). Some of these products are derived from agricultural by-products (such as corn cobs) that might otherwise be managed as waste. They can serve as a corrosion inhibitor for chloride-based deicers, minimize damage to vegetation, and result in reduced application rates (which lower labor, fuel and other operational costs). However, like acetates, they are costly, can contribute to eutrophication and oxygen depletion in water supplies, and must be used in conjunction with other deicing products (often as a roadway pre-treatment or a wetting-solution for other solid deicers).
Chloride-based Deicers Other Than Sodium Chloride
Alternatives to sodium chloride such as calcium chloride, magnesium chloride, and potassium chloride are effective deicing chemicals. They are less corrosive than sodium chloride and less expensive than non-chloride based deicing chemicals (costs can be 30% to 40% more than sodium chloride, but because they melt ice more quickly, 30% and 50% less of these products is required). Like sodium chloride, they can damage vegetation and can contribute chlorides and heavy metals to water supplies. However, their lower eutectic temperature helps prevent snow and ice from bonding to pavement and melt ice at lower temperatures.
Snow and Ice Control Specification
301 West Preston Street, Baltimore, MD 21201