The recycling use of MSWI bottom ash as road construction material for carbon emissions reduction based on life cycle...

This study evaluates the potential of municipal solid waste incineration-bottom ash (MSWI-BA) as a partial substitute for natural aggregates (NAs) in asphalt pavement, focusing on carbon emissions reduction. A comparative life cycle assessment (LCA) was conducted for a 5.142-km municipal road (Guangying Avenue, Sichuan, China) under two scenarios: a conventional pavement with NAs and a pavement incorporating MSWI-BA aggregates (MAs) at optimised (Alternative A) and maximised (Alternative B) substitution rates. The LCA covered raw-material production, transportation, and construction phases, using carbon emission factors (CEFs) and a Data Quality Indicator-Monte Carlo uncertainty analysis for robust quantification. Results indicate that high substitution of Mas yields significant carbon savings. Under Alternative B (70 % MA in the base layer and 100 % in the subbase/capping layers), the pavement saved approximately 2.78 × 10⁴ tonnes of NAs and reduced life-cycle emissions by about 31 %. The greatest reductions occurred in lower layers, with base, subbase, and capping courses achieving 51 %-78 % CE reductions, compared to only 5 % in the surface layer. Transportation emissions partially offset benefits, as MAs were transported 156 km compared to 8 km for NAs. Local processing (Alternative B within 50 km) is recommended to maximise net gains. Despite a modest 7 % increase in construction-phase energy use for MA paving, the overall carbon benefit remains clear. These findings highlight the scalability of MSWI-BA for low-carbon road construction and provide practical insights for engineers and policymakers pursuing sustainable infrastructure solutions.