The Quest for Less Toxic Ways to Deice RoadsJanuary 7, 2015
Keeping icy roads safe is costly and constant work. The U.S. spends about $2.3 billion each year to remove highway snow and ice. For much of that removal, transportation agencies and businesses use chlorides. These compounds depress freezing temperatures and eat through ice, improving vehicle and pedestrian safety. But they also hang around, corroding vehicles as well as nearby vegetation and aquatic environments. Chloride alters soil pH, dehydrates plants, and threatens the health of our drinking water supplies. Additionally, some of the compounds used in conjunction with chloride – such as metals and cyanide, used to prevent caking – compound the damage to surrounding ecosystems.
The above costs, to both ourselves and our environment, have prompted a surge in research on limiting usage of toxic deicers. What solutions work without sacrificing environmental health or road safety?
Washington State University has helped form a center that studies this very problem. The Center for Environmentally Sustainable Transportation in Cold Climates (CESTCC) studies cold climate “road ecology,” which includes green snow and ice control as well as issues with wildlife crossings, fish passages, dust and the use of recycled materials in pavement. Xianming Shi, assistant director of the center and a WSU associate professor in civil and environmental engineering, says that Washington has a deicer problem. Washington applies roughly four tons of salt per lane mile per winter season. As a nation, Shi said, “We are kind of salt addicted, like with petroleum, as it’s been so cheap and convenient for the last 50 years.”
Shi and his colleagues are testing some safer substitutes for chlorides. “There is a lot of talk about beet and tomato juice deicers that are meant to be less corrosive to vehicles, guard rails, steel bridges and concrete pavement,” Shi said. “They help, but there is still plenty of room for improvement.” Shi’s team has also developed a tonic for ice made from the leftover barley residue from vodka distilleries.
Shi’s team is also developing technologies that facilitate better management of deicers. The team has helped develop smart snowplows, which use sensors to gauge an appropriate level of salt application. “Ordinary snowplows have at least one sensor to measure pavement temperature,” Shi said. “Smart snowplows not only read temperature but also residual salt from previous applications, the presence of ice and the amount of friction on the road. All of these readings help operators apply less salt.” These plows are currently being integrated into winter fleets.
In most cases, relying on a single substitute for chloride won’t solve the problem. Using sand, for example, can improve traction but fails to offer the same deicing or anti-icing properties as chemicals. Also, if used excessively, sand can clog storm drains and choke waterways.
While researchers test the effectiveness and scale-up potential of safer alternatives, a number of management solutions can work now to reduce roadway toxicity. The Transportation Research Board recently published a synthesis of Strategies to Mitigate the Impacts of Chloride Roadway Deicers on the Natural Environment. The report documents a range of management strategies, such as improving salt management plans, staff training, monitoring and record keeping, weather forecasting, and vegetation management.
Transportation departments and businesses with good management plans typically deploy a variety of road treatments, such as different deicing chemicals depending on temperatures and conditions, sanding, plowing and snow removal, and street closures. The city of Portland, OR, for example, uses different treatments to fit different conditions. Instead of rock salt, it uses a less toxic compound, calcium magnesium acetate (CMA), to deice dangerous streets, bridges, and overpasses. The city’s Snow and Ice plan suggests that road crews deploy magnesium chloride only in temperatures below 17 degrees Fahrenheit, a rare low temperature in Portland’s relatively temperate climate.
As part of an ice management plan that considers the environment, other strategies include:
- Apply the least amount of chemicals necessary to melt the ice (e.g., not overspreading). Excessive application of deicers does not improve effectiveness. Instead, over-application will waste materials and release unnecessary chemicals into surrounding environments.
- Avoid more toxic chemicals by using products certified by the entities mentioned below.
- Anti-icing strategies prevent ice from building up on roadways in the first place. In recent years, the New York State Thruway Authority began using an anti-icing mixture of sugar beet juice and brine to pre-treat roads. This method reduces the amount of salt added to the road, though the brine still contains sodium chloride.
The challenge of limiting toxic deicer usage has prompted the development of a number of local and national initiatives and resources. For those interested in digging deeper, the following resources provide additional info on the public and environmental health impacts of deicers as well useful solutions and strategies for transportation departments and businesses.
- Green Purchasing Best Practices: Deicers –A practical guide to environmental purchasing strategies and safer product lists.
- Transportation Association of Canada’s Road Salt Management Guide – A synthesis of best management practices for road salt management.
- Minnesota Pollution Consumer Control Agency’s Metro Area Chloride Project – Great info about the public and environmental impacts of chloride.
- University of Michigan’s Deicing and Winter Management Practices Webpage – Detailed info about tradeoffs involved in using different deicing chemicals and agents.
- New Hampshire Road Salt Reduction Initiative – Useful fact sheets and BMPs for business owners seeking to reduce salt use.
Here are a few resources to help find less toxic deicing and anti-icing products:
- Pacific Northwest Snow Fighters Specification and Qualified Products List (QPL) – Approved products must meet specifications limiting the amount of certain heavy metals and other environmental pollutants.
- US EPA’s Design for Environment (DfE) Program Recognition – Any products listed here have gone through a third-party chemical profiling of all formulation ingredients.
- US Department of Agriculture (USDA) Biobased Product Certification Catalog – Products listed in this catalog require snow and ice control products to have at least 93% bio-based content.
– Cyrus Philbrick, Communications Manager
& Michelle Gaither, Industrial Engineer