Identifying hundredfold carbon emission gaps in multiple resource recycling routes of construction waste via process and hybrid life cycle assessment

Resource recycling of construction waste can be an effective substitute for the production of building materials, significantly reduce environmental pollution and ecological damage while lowering carbon emissions. However, existing studies lack a comprehensive and accurate comparison of different recycling processes, making it difficult to fully and accurately determine the associated carbon reduction potential. In this paper, process life cycle assessment (LCA) and hybrid LCA models are used to calculate carbon emissions from resource recycling of construction waste. The results show the carbon emissions of primary resource recycling of construction waste for recycled aggregate, secondary resource recycling of cement stabilized recycled aggregate crushed stone, and recycled concrete solid brick are 2.169 kg CO₂eq/t, 37.019 kg CO₂eq/t, and 77.144 kg CO₂eq/t, respectively, and these three recycling pathways are the lowest carbon methods; The carbon emissions calculated by the process LCA model are only about 0.07–0.15 % of those calculated by the hybrid LCA model; An analysis of the sensitivity of recycled building materials to inputs of electricity, diesel and natural gas, alongside an uncertainty analysis of the input data for the computational model, verified the validity of the data and the accuracy of the calculations from both models. The research findings also provide guidance on the selection, use and improvement of LCA models and offer reasonable carbon reduction strategies for relevant enterprises. Furthermore, the findings provide comprehensive insights into the application scenarios of different carbon accounting methods and offer scientific data to support the low-carbon recycling of construction waste.