Life cycle assessment of asphalt variants in infrastructures: the case of lignin in Australian road pavements

In order to mitigate against the Green House Gas (GHG) emissions of road projects, this paper presents the life cycle assessment (LCA) of lignin as a partial replacement for bitumen in Australian road pavements. A cradle-to-gate LCA was conducted to assess the environmental impacts of both a control asphalt and asphalt containing 25% lignin binder, to provide a direct comparison of both road pavement alternatives. The cradle-to-gate life cycle assessment found that a 5.72% reduction in Global Warming Potential (GWP) of CO2e Kg is possible through the substitution of 25% bitumen binder with lignin.This study also recognised that the phases that had the highest environmental impact in the cradle-to-gate LCA study were the extraction of raw materials and the pavement mixture production processes corresponding to 30.9% and 64.4% respectively. Further analysis using Monte Carlo Simulation revealed that up to 20% reduction in GWP is possible, based on the uncertainties in the extractive and production processes. The LCA results obtained also showed that the sustainability of Australian road pavements may be improved by replacing a proportion of bitumen using lignin. Further research will assess the rheological performance of the asphalt to ensure that it exceeds or at least matches that of its conventional asphalt counterpart, particularly over the lifetime of the road pavement.