Air, Water and Solid Waste Impacts: Greenhouse gasses (GHG), which trap heat in the atmosphere, include carbon dioxide and methane entering the atmosphere primarily through the combustion of fossil fuels such as oil, natural gas and coal. The highest carbon fingerprint determined in the EEA occurred in the mill & fill alternative, with micro surfacing GHG emissions lower by almost 45 percent. It was higher for mill & fill because that alternative requires over twice the amount of material to be shipped to and from manufacturing and job sites.
With regards to water emissions, micro surfacing has the highest critical water volume requirement, attributed primarily to the manufacture of lane striping materials. Excluding the impact of road markings, the remaining water emissions for each alternative are about the same.
Solid waste emissions included those from municipal, special, construction and mining wastes. They are principally the result of sending materials to landfills for disposal. Even when considering the perpetual use of RAP content, the study finds that mill & fill still has the highest impact in this category due to the much greater quantity of materials.
Land Use: With respect to the impact caused by the two technologies on the biodiversity of our ecosystems, the EEA found that energy required to produce and apply mill & fill is the largest contributor to land use. Mining wastes as generated from aggregate production, as well as solid waste disposal of unrecycled materials, also contribute to the impact on land use.
Summation Of EEA Findings
Evaluating the individual environmental impact categories, the EEA finds that mill & fill has the highest environmental impact on a weighted basis in all main categories. Micro surfacing performs best in all main categories on a weighted basis because it requires less than 50 percent of materials than that for mill & fill, while maintaining the desired customer benefit.
Furthermore, although applied more frequently, micro surfacing scores lowest in resource consumption—the most relevant environmental impact for the study—because of its significant reduction in the amount of binder and aggregate used. This materials reduction also benefits micro surfacing in toxicity potential and risk potential.
Micro surfacing also scores lowest in energy requirement—the second most relevant environmental impact—because of its lower overall consumption of asphalt binder, lower manufacturing and application temperatures, and reduced logistical impacts due to shipping less material to and from the job site.
(This article is being submitted by the International Slurry Surfacing Association (ISSA). Tim Harrawood, ISSA Past President and Manager of Vance Brothers, Inc., was a member of the study group that prepared this report. This is a synopsis of the overall analysis. The full report is posted online by NSF at