Paving the Path to Net-Zero: A Life Cycle Assessment of Asphalt Pavement Construction Projects in Washington State

Abstract

With the US setting a goal of reaching net-zero carbon emissions by 2050, industries must act towards progressing towards this goal. The National Asphalt Pavement Association has stepped up to this challenge by setting an industry goal of halting climate change by achieving net-zero carbon emissions by 2050 during asphalt production and construction. This study examines four Washington State Department of Transportation (WSDOT) asphalt case studies from the 2023 paving season. It analyzes the carbon emissions from the material production through the construction phase (life cycle stages A1-A5). Environmental Product Declarations (EPD) and construction data were collected from contractors to cover upstream asphalt mixture production (A1-A3) and construction (A4-A5) impacts. Life cycle assessments were completed on the openLCA software using project data to quantify the environmental impacts. With a functional unit per short ton of asphalt and based on trends in the life cycle assessments (LCA), material production obtained from the mix design EPD had the most significant impact. Material production (A1-A3) of the four projects fell between 65-80% of the project’s total global warming potential (GWP), followed by transportation (A4) at 10-20% and construction activities (A5) at 8-13%. Material production has such a significant impact on the total GWP that obtaining the mix design’s EPD can provide a good understanding of a project’s total carbon emissions through the construction stage. Reducing the carbon emissions associated with the asphalt paving industry is essential in meeting net-zero carbon emissions goals. This study provides a glimpse into the state of carbon emissions of the asphalt paving industry in Washington State.