Carbonic anhydrase-producing bacteria-mediated sandstone-CO₂-brine interaction and its impact on carbon sequestration

CO₂ geological sequestration is one of the most effective technologies for reducing atmospheric greenhouse gas concentrations. However, conventional storage technologies are frequently accompanied by long cycles, and the vast majority of CO₂ is in an unstable state in the subsurface, posing a leakage risk; thus, it is particularly important to develop new technologies to accelerate the conversion of CO₂ stored in the subsurface into a stable ionic and mineral state. The subsurface is rich in microbial communities, and when CO₂ is introduced into the formation, complicated biogeochemical reactions occur, making it critical to investigate the effect of microbially mediated water-rock reactions on CO₂ geological storage. In this study, Bacillus licheniformis was screened from deep saline aquifers and added to the sandstone-CO₂-brine system. Changes in bacterial growth, solution chemistry, and rock properties were tested to analyze the microbial effects on the mineral dissolution-precipitation process. After 60 days of reaction at 50 °C and 10 MPa, the microbes exhibited strong tolerance to extreme CO₂-rich environments; the system's pH increased, with the microbial treatment showing a higher pH value than the control group. The participation of bacteria increased the concentration of bicarbonate ions and promoted the dissolution trapping of CO₂; simultaneously, it significantly accelerated the dissolution-precipitation process of minerals, which led to an increase in the mass of rock cores and a decrease in core porosity from 12.61 % to 10.75 %. These processes promoted CO₂ mineral trapping, demonstrating the potential of microbes to improve the stability and safety of CO₂ geological sequestration.