Environmental impacts of low-temperature CO₂ sequestration via carbide slag waste mineral carbonation and utilization of carbonated end-product

The increased concentration of atmospheric carbon dioxide (CO₂) necessitates sustainable CO₂ capture and storage strategies. Direct mineral carbonation using industrial wastes such as carbide slag offers a dual benefit of CO₂ sequestration and waste valorization. However, the environmental implications of using carbide slag for direct mineral carbonation remain unexplored. This study presents a comprehensive life cycle assessment (LCA) of the wet-phase mineral carbonation of carbide slag waste in the UAE region. The key goals include the identification of major hotspots in the wet-phase mineral carbonation process and investigation of alternative scenarios with different end-of-life options to reduce environmental burdens. A cradle-to-gate/grave LCA was conducted following ISO 14044 standards. Environmental impacts were quantified using 18 ReCiPe 2016 midpoint categories. LCA results reveal that thermal drying as a pre-treatment is the dominant contributor to global warming potential (GWP, 828 kg CO₂ eq), fossil resource scarcity (345 kg oil eq) and toxicity impacts. Transportation of waste to the facility plays a notable role in terrestrial ecotoxicity (765 kg 1,4-DCB eq) and land use (2.48 m²a crop eq). In contrast, the impact of the operation stage (mineral carbonation process) was significantly lower (<1 % of the total burden) in all categories. Alternative end-of-life scenario study indicates that mixing the carbonated end-product with cement offers the highest environmental benefits, with ∼300 % drop in GWP. Moreover, the application of solar drying instead of thermal drying can reduce GWP by 91 %. Overall CO₂ reduction potential across all the scenarios ranged from 0.1 to 3.5 kg CO₂ avoided/ kg CO₂ captured. These results indicate the importance of proper end-product utilization and renewable energy adoption in the proposed mineral carbonation process. The LCA results demonstrate the potential of wet-phase mineral carbonation of carbide slag as a viable CO₂ capture and utilization strategy. However, this study is based on the extrapolation of lab-scale experimental results. Thus, future efforts should focus on scaling up the process to validate the assumption for large-scale applications. Moreover, the comprehensive uncertainty analysis for the composition of carbide slag and flue gas should be conducted to improve the robustness of the LCA.