Unveiling the Role of Processing Route in CO2 Mineralization by Incineration Bottom Ash under Near-Ambient Aqueous Conditions

Abstract

Process design is crucial to scaling up ex situ mineral carbonation (MC) for CO₂ storage and utilization. Here, we aim to elucidate the emission reduction potential and reaction product of different processing routes under near-ambient conditions. Utilizing municipal solid waste incineration ash (MSWIA) as a starting material, we examined the combined effects of semi-dry (SD) versus wet (W) and batch (BR) versus continuous flow regimes (CFR). We found that CFR-SD demonstrated the best promise in net emission reduction (∼0.047 kg CO₂-eq for carbonating 1 kg MSWIA), attained by an accelerated CO₂ uptake and low energy penalty. A carbonate-binding effect was observed under SD (but absent in W), raising the particle size by more than an order of magnitude. Although calcite was identified as the only CaCO₃ polymorph, its microstructure varied significantly, with increasing crystal size (from 0.1 to 1 μm) and angularity when switching from SD to W. Introducing agitation to the system further promoted the dispersion of CaCO₃, thereby increasing the amount of CO₂ stored under CFR-SD. This study verifies the environmental advantages of CFR over BR and points to the synergies of MC with the production of carbonate-bond artificial aggregates through CFR-SD and cement additives through CFR-W for construction applications.