Collaborative resource recovery and carbon emission reduction from municipal solid waste incineration bottom ash through semi-dry carbon sequestration

This study developed an efficient semi-dry carbonation process for municipal solid waste incineration bottom ash (MSWIBA) to simultaneously achieve resource recovery and carbon emission reduction. The optimal carbonation conditions were established at a liquid-to-solid ratio of 0.15, temperature of 40°C, and pressure of 0.2 MPa using a simulated flue gas containing 20 % CO₂, achieving maximum carbon sequestration of 10.7 % within 12 h - equivalent to the performance obtained in pure CO₂ atmosphere within 60 min. The carbonation treatment significantly modified BA characteristics, increasing particle size while reducing sub-10μm particles, enhancing specific surface area, pore size and porosity, and transforming surface morphology through calcite formation. Concurrently, the process effectively improved heavy metal immobilization, reducing leaching concentrations to meet regulatory standards, and ensuring environmental safety for subsequent applications. When employed as supplementary cementitious material, carbonated BA demonstrated superior performance compared to untreated BA, exhibiting reduced water demand, improved workability, accelerated early hydration through nucleation effects, and enhanced pore structure via Ca(OH)₂ carbonation to form CaCO₃. These modifications collectively contributed to a significant improvement in compressive strength of cement mortar at equivalent dosages. The findings demonstrate that semi-dry carbonation effectively enhances both the carbon sequestration potential and cementitious properties of BA, establishing its viability as a sustainable alternative to conventional cement in construction applications.