Environmental Life-Cycle Assessment of Winter Maintenance Treatments for Roadways

Abstract

Departments of Transportation (DOTs) rely heavily on chloride-based treatments for winter road maintenance despite the well-documented effects of these chemicals on infrastructure and the environment. Proposed alternative treatments have yet to be widely adopted because of economic and technical limitations that are largely outside of the control of the DOT. This work explores the application of winter maintenance chemicals with a life-cycle approach to understand which actions a DOT can take to reduce the negative life-cycle environmental impacts of these activities. Three representative treatments and/or best management practices are compared: conventional rock salt, calcium magnesium acetate (CMA), and preemptive treatments of roadways with a brine of salt and/or CMA. The results conclusively show that CMA, which has been widely touted as an environmentally preferable, if more expensive, alternative to chloride-based treatments, has considerably higher environmental impacts over its entire life cycle. Most of these burdens are associated with the upstream production processes required to generate the CMA. The salt-based treatments consume considerably less water, energy, and generate fewer greenhouse gases and biochemical oxygen demand in receiving waters. Applying the chloride chemicals as a brine rather than in the dry form results in important reductions in all environmental impacts over the entire life cycle. This result is consistent for a variety of climate conditions (e.g., representative of coastal, piedmont, and mountain climates) considered for this study, which used historical weather data from Virginia. Because DOTs can affect appreciable improvements in efficiency by using brines, sensitivity analysis identifies the activities specifically resulting in the most important environmental improvement on a systems basis. The DOT-controlled steps with the greatest potential for improvement include reducing the energy consumed for the salt application process and implementing practices that reduce total storm water runoff to reduce chloride loading.