Carbon sink gain mechanism and evaluation of coal-based solid waste resource utilization in China

The extraction and utilization of coal in China have generated massive amounts of coal-based solid waste (CBSW), posed serious environmental risks, and contributed to greenhouse gas emissions. Under the “Dual Carbon” goals, promoting the resource utilization of CBSW has become essential for the green transition of the coal industry. This study systematically reviews the properties, environmental impacts, and resource potential of CBSW, identifying utilization pathways such as building material substitution, backfill mining, and ecological remediation. An integrated Life Cycle Assessment (LCA) and System Dynamics (SD) model was developed to quantify the carbon sink gain (CSG), incorporating direct emissions, substitution benefits, avoided emissions, and carbon sequestration. The complete stock-flow differential equation system, standardized multi-source parameterization framework and 30-year multi-scenario dynamic simulation module of the coupled LCA-SD model are fully presented, supported by the stock-flow causal loop diagram, full parameter table and scenario setting table for transparent methodological interpretation. Results show that fly ash utilization in building materials yields the highest CSG (405.7 kg CO₂-eq/t), primarily due to cement clinker substitution. Backfill mining offers moderate CSG (218.5 kg CO₂-eq/t) with synergistic safety and ecological benefits, while high-value utilization of gasification slag shows the lowest net CSG (165.8 kg CO₂-eq/t) due to high process energy consumption. The coupled LCA-SD model constructed in this study can provide differentiated low-carbon reference basis for coal enterprises and environmental policymakers, which provides a theoretical and practical foundation for low-carbon solid waste management in China.