Identification of the Main Environmental Impact Categories Over the Life Cycle of Hot Mix Asphalt: An Application to Green Public Procurement

Abstract

Increased environmental awareness has led road agencies to consider the implementation of green public procurement (GPP). Besides sustainability rating systems, environmental indicators can also be implemented in GPP to help road agencies make informed decisions about the environmental impact of the pavement works they procure. A vast literature review revealed that it is still unclear which impact categories are responsible for the majority of the total environmental impact of asphalt mixtures. The objective of this study was to identify the impact categories with the greatest contribution to the total environmental impact of hot mix asphalt so that they can be implemented in the form of environmental indicators in GPP. The scope included conventional and polymer-modified binder and three mix design alternatives: only virgin aggregate, reclaimed asphalt pavement (RAP), and RAP with rejuvenators. The cradle-to-cradle life cycle assessment (LCA) performed showed that global warming (GW), fine particulate matter formation, fossil resource scarcity, and human non-carcinogenic toxicity were responsible for at least 90% of the total impact according to the ReCiPe 2016 hierarchic assessment method. Therefore, a simplified LCA focusing on these four impact categories seems sufficient for the purpose of comparing the environmental performance of alternatives in GPP. It was also found that GW alone accounted for approximately 50% of the total impact, which seems to make GW a good surrogate for the total impact among the asphalt mixtures evaluated. Future work should investigate whether the conclusions from this study still hold up when using secondary materials, lower temperature mixing technologies, or in-situ recycling.

Towards Sustainable Roads: A Systematic Review of Triple-Bottom-Line-Based Assessment Methods

“…Several studies have already addressed the environmental impacts of roads and pavements. A commonly used method for this purpose is Life Cycle Assessment (LCA) [18,19]. LCA is a robust and standardized method for assessing the environmental impacts of products and services throughout their life cycle and is widely used both in industry and academia [20].…”

An investigation on the use of lean asphalt as an alternative base material in asphalt pavements by means of laboratory testing, life cycle assessment, and life cycle cost analysis

“…Furthermore, the EOL impact (C1-C3) is the impact from the deconstruction, transport of waste, and waste processing phase. These results highlight the importance of modeling entire pavement sections rather than individual layers in pavement sustainability assessment.Regarding midpoint indicators, a prior study showed that at least 90% of the total impact in the cradleto-cradle analysis of hot mix asphalt is explained by only four indicators: global warming (GWP), fine particulate matter formation (FPMF), fossil resource scarcity (FRS), and human non-carcinogenic toxicity (HNCT)[55]. Following the same approach, this study found that five out of the 18 midpoint indicators considered in ReCiPe 2016 (H) are responsible for more than 95% of the total environmental impact of the different materials evaluated (Figure8a).…”