This study explores biohydrometallurgical techniques within the carbon capture, utilization, and storage (CCUS) framework to address global CO2 emissions. A key aspect of this research involves utilizing the bacterium Proteus mirabilis strain SKC-7 for bioleaching steel slag, resulting in a calcium-rich pregnant leach solution (PLS) suitable for CCUS applications. The study rigorously examines the impacts of various parameters on the formation of carbonate precipitates within the CCUS framework. These parameters include the incorporation of carbonic anhydrase enzymes (found in the spent medium), the adjustment of pH levels, and the modulation of CO2 gas flow rates. Initially, the bioleaching of steel slag was conducted to generate the calcium-rich PLS, followed by carbon sequestration experiments using the bacterium Bacillus subtilis strain SKC-14. These experiments involved injecting CO2 into a combination of PLS and spent medium, after which the precipitates were analyzed for calcium conversion percentages. The characterization of these precipitates was conducted using atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS). Key findings included high calcium conversion rates under various experimental conditions and the identification of diverse carbonate precipitate morphologies, including natron and the vaterite polymorphs of calcium carbonate. The study demonstrates the effectiveness of biohydrometallurgical methods in advancing CCUS technology, presenting a viable solution for mitigating global warming and climate change. To the best of our understanding, this study represents the initial documented application of biohydrometallurgical processes in the context of CCUS.