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How to Reduce the Environmental Impact of Deicing Roads?


Rapid Response Question: How can we reduce the environmental impact of road deicing practices?

Request by: Anonymous

Report by: Michelle Gaither & Cyrus Philbrick

 

Salt_truck_Milwaukee largeBackground

Keeping icy roads and parking lots safe is costly and necessary work. The U.S. spends about $2.3 billion each year to remove highway snow and ice (1). Most de-icing is accomplished by mechanical methods (scraping, pushing or plowing) or by applying chemicals and/or sand as an abrasive. Chemical de-icing compounds depress the freezing temperature of water and chemically turn ice back into water, improving vehicle and pedestrian safety.

Traditionally, transportation agencies and businesses have used chloride-based salts as deicers. But chlorides resist break down in the environment and are corrosive to bridges, other metal structures, especially aluminum, and to the metal parts of vehicles, especially underneath the car. Damage from salt corrosion costs the U.S. up to about $19 billion per year (1). Chloride also alters soil pH and dehydrates plants along road, highways and parking lots. Increased salinity also threatens the health of drinking water supplies for humans and wildlife. Additionally, some compounds often used in conjunction with chlorides – such as certain metals and cyanide – worsen the negative impacts on surrounding ecosystems.

The above financial and environmental costs have prompted a surge in research on limiting usage of harmful deicers. What strategies can reduce the amount or impacts of de-icing, without sacrificing environmental health or road safety?

 

Key Findings

De-icing is defined as removal of snow, ice or frost from a surface. Anti-icing chemicals can supplement de-icing processes, and can also be applied ahead of time to delay or prevent the bond of ice and snow to the roadway, making mechanical removal easier.

Many transportation departments and businesses with good management plans try to minimize chlorides and typically deploy a variety of road treatments or chemicals, depending on temperatures and conditions. Other treatments include: sanding, plowing and snow removal, and street closures. Road salt is more effective at temperatures around 15 degrees Fahrenheit or lower (3), while calcium magnesium acetate’s (CMA’s) effectiveness diminishes below these temperatures. In most cases, relying on a single substitute for chloride won’t work. 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 get carried by melting snow and ice into nearby streams, causing excess sediment in waterways.

The city of Portland, OR uses CMA, a less toxic compound than chlorides, to deice dangerous streets, bridges, and overpasses. The city’s Snow and Ice plan (6) suggests that road crews deploy magnesium chloride only in temperatures below 17 degrees Fahrenheit, a rare low temperature in Portland’s relatively temperate climate.

Here are a few lists demonstrating some of the less toxic de-icing agents, certified by the entity noted below.

*DISCLAIMER: PPRC does not endorse or guarantee performance of any of the products listed here.

A number of food-production byproducts have promising anti-icing and deicing properties. Some examples include: tomato juice, sugar beet juice (or molasses), pickle juice, and barley residue. A number of these liquids have worked on small scales, at the municipal level and in pilot studies, as alternatives or as supplements to more toxic compounds. Even larger entities, such as the New York State Thruway Authority, recently began using an anti-icing mixture of sugar beet juice and brine to pretreat roads. A number of municipalities have reported that using sugar beet juice to supplement chloride both saves money and lessens environmental impacts. This method reduces the salt draining to sewage systems and into the environment, but it does not eliminate salt altogether.

In addition to studying alternative deicers, the Center for Environmentally Sustainable Transportation in Cold Climates (CESTCC) is developing technologies that facilitate better management of deicers. CESTCC has helped develop “smart snowplows,” which use sensors to gauge an appropriate level of chemical application. “Ordinary snowplows have at least one sensor to measure pavement temperature,” Xianming Shi, assistant director of the center, 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 (4).

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 (2).

Other strategies to minimize environmental impacts include:

  • Installing a road weather information system (RWIS) technology provides timely and accurate information on upcoming and currnet weather and pavement conditions, to plan for appropriate anti-icing and de-icing needs.
  • Apply the least amount of chemicals necessary to melt the ice, following manufacturer instructions. Do not overspread, or under-dilute when mixing is required). Excessive application of deicers does not improve effectiveness. Instead, over-application will waste materials, releasing unnecessary chemicals. Some chemicals, salts especially, can be wetted to spread more easily so less is needed. However, this can also contribute to higher corrosion rate of equipment.
  • Employ anti-icing strategies and products prevent ice from building up on roadways in the first place. Most commonly, this means spreading anti-icing liquid, or pre-salting roads, about two hours before a storm hits to help prevent ice from sticking. The EPA estimates pre-salting can reduce salt use by 41 percent to 75 percent (6).
  • Avoid more toxic chemicals by using products certified by the entities shown above.
  • Whenever possible, ensure applicators are certified or specifically trained to perform the task and operate spreading equipment.

 

Conclusion

Throughout the country, municipalities have started to use a variety of less toxic alternatives, or supplements, to chlorides. The most effective way to reduce toxics and maintain road safety, however, is to establish a good ice management plan that deploys a variety of road treatments depending on temperature and road conditions.

 

Additional Resources

The challenge of limiting toxic deicer usage has prompted the development of a number of local and national initiatives and resources. 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:

 

References

  1. How America got addicted to road salt — and why it’s a problem. Vox. http://www.vox.com/2015/1/13/7531833/road-salt-environment-alternatives (accessed Feb 2, 2015).
  2. Transportation Research Board. National Cooperative Highway Research Program Synthesis 449. Strategies to Mitigate the Impacts of Chloride Roadway Deicers on the Natural Environment; Project 20-05 (Topic 43-12). Washington, D.C. 2013
  3. University of Michigan. Department of Occupational Safety and Environmental Health: Environmental Protection. http://www.oseh.umich.edu/environment/wintermaint.shtml (accessed Jan 7, 2015)
  4. Phillips, R. Green highway snow and ice control cuts the chemicals. Washington State University News [Online] November 17, 2014. https://news.wsu.edu/2014/11/19/green-highway-snow-and-ice-control-cuts-the-chemicals/#.VKGztcP1YA (accessed Jan 7, 2015)
  5. Waters, D & Christensen, P. Molasses next big thing to de-ice local streets? Chicago Tribune. [Online] February 02, 2013. http://articles.chicagotribune.com/2013-02-13/news/ct-tl-wauconda-molasses-20130212_1_beet-juice-beet-juice-molasses (accessed Jan 7, 2015)
  6. City of Portland Bureau of Transportation. Snow and Ice Plan: Background. https://www.portlandoregon.gov/transportation/article/330813 (accessed Jan 7, 2015)

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