Atmospheric CO₂ Sequestration in Seawater Enhanced by Molluscan Shell Powders

Carbon capture, utilization, and storage (CCUS) are widely recognized as a promising technology for mitigating climate change. CO₂ mineralization using Ca-rich fluids and high-concentration CO₂ gas has been studied extensively. However, few studies have reported CO₂ mineralization with atmospheric CO₂, owing to the difficulty associated with its low concentration. In seawater, the biomineralization process promotes Ca accumulation and CaCO₃ precipitation, assisted by specific organic matter. In this study, we examined the conversion of atmospheric CO₂ into CaCO₃ in seawater using shell powders (Pinctada fucata, Haliotis discus, Crassostrea gigas, Mizuhopecten yessoensis, Turbo sazae, and Saxidomus purpurata). Among the six species, the shell powder of S. purpurata showed the highest rate of CaCO₃ formation and recovery of CaCO₃. NaClO treatment test revealed that the organic matter in the shells enhanced the CO₂ mineralization. All materials used in this study, including atmospheric CO₂, seawater, and shells, are economically feasible for large-scale applications. Using shell powder for CO₂ mineralization in seawater embodies an innovative technological advancement to address climate change.