Life Cycle Assessment of Greenhouse Gas Emissions from Recycled Asphalt Pavement Production

Abstract

With the growing impact of climate change, there is an increasing need and obligation to reduce the responsible greenhouse gases (GHG) in road construction as well. Using life cycle assessment (LCA) methods, several studies have already separately analysed individual parameters of the asphalt production process and illustrated potential improvements in terms of GHG reduction. However, the data of most assessments originate from single sources and databases, and as such can offer little validation against unreliable assumptions. For this reason, in addition to conducting separate assessments at quarries, batch asphalt mixing plants, and construction sites in order to collect energy and material consumption data with which to calculate GHG emissions, this work relies on the results of multiple sources found in the literature. Using the structure for environmental product declarations (EPDs) in EN 15804, our results are divided into the different stages of a life cycle and the corresponding modules. This allows for systematic comparison of different products and eliminates previous uncertainties regarding the inclusion of benefits beyond the system boundary. The results show the dominance of asphalt binder in the material footprint and the corresponding advantage of substituting virgin material with recycled material, as well as the influence of material moisture on GHG emissions in the production process. In addition to the evaluating the material itself, two road sections with increasing traffic volume (and increasing share of electric mobility) were examined and compared with the traffic-related GHG emissions over a 30-year lifetime. We can confirm that traffic has a substantially higher share of the total GHG emissions (>95%); however, as its regulation is the responsibility of governments, the construction industry can only bring about improvements in its own sphere in seeking to further climate protection.