Research on carbon reduction benefits and spatial optimization of construction waste resource utilization under transport distance thresholds: A case study in Jiangsu, China

The construction industry is a significant source of global carbon emissions and generates massive amounts of construction and demolition waste (CDW), making its resource utilization crucial for a low-carbon transition. While Life Cycle Assessment (LCA) has been applied, the dynamic threshold effect of transportation distance on carbon reduction benefits remains poorly quantified, often overlooking spatial distribution factors. This study conducts a comprehensive LCA of a CDW resource utilization center in China, comparing the carbon emissions of resource utilization against direct landfilling. Monte Carlo simulation and global sensitivity analysis were employed to address parameter uncertainties and to identify key influencing factors. Furthermore, a novel three-dimensional spatial optimization model was developed to identify critical transportation distance thresholds. The results demonstrate that although the carbon intensity of resource utilization (6.85 kg CO2e/t) is higher than that of direct landfilling (4.27 kg CO2e/t), leveraging the transportation advantage of recycled aggregates (Δd = 80 km) yields a net reduction of 5.08 kg CO2e/t. The resource utilization rate (α) is identified as the most sensitive parameter. Spatial optimization reveals that to ensure carbon benefits, the sum of the distances from the CDW source to the resource utilization center (d1) and from the center to the end-users (d4) must be dynamically adjusted based on the landfill distance (d3). For instance, when the landfill is near urban areas (d3 < 20 km), d1 + d4 must be ≤ 80 km. This study provides a scientific basis and a practical decision-support tool for CDW management and logistics planning, advocating for a ''distributed resource utilization centers coupled with regional landfills'' strategy to maximize carbon reduction.