Low-Carbon Asphalt Mixtures Using Wind-Industry Waste: A Life Cycle Assessment

Industrial waste valorization in asphalt mixtures can reduce natural resource use and climate impacts, although benefits depend on the substituted material, conditioning needs, and avoided waste management route. This study evaluates the cradle-to-gate environmental performance of asphalt mixtures incorporating welding slag and paint sludge from wind-tower manufacturing. A comparative LCA was conducted for 1 t of asphalt mixture produced at the plant. Four scenarios were assessed: a conventional reference mixture, full replacement of limestone filler by welding slag, incorporation of conditioned paint sludge with reduced virgin bitumen content, and a combined formulation. The model was implemented in SimaPro using ecoinvent v3.8 under the cut-off system model, applying IPCC 2021 GWP 100a and ReCiPe 2016 midpoint and endpoint methods. The reference mixture presented a global warming potential of 95.20 kg CO2 eq/t. Under the baseline avoided treatment crediting approach, welding slag reduced GWP by 9.67%, paint sludge by 28.28%, and the combined scenario by 37.95%. Endpoint results generally indicated lower impacts for the modified scenarios, although rankings differed among damage categories, particularly for human health due to the avoided landfill credit. Overall, these valorization routes showed environmental benefits, especially when hazardous paint sludge reduced virgin bitumen use and avoided conventional incineration.