Interactions between deep microbial biosphere and geo-sequestrated CO2: A review

CO₂ capture and storage (CCS) is a promising approach for significantly reducing CO₂ emission from industrial ends and mitigating global warming in the coming decades. Given that most of the subsurface formations are biological active environments, the deep microbial biosphere plays an important role in governing the fate and sequestration efficiency of injected CO₂. While substantial researches have explored the initial states and microbial shifts following CO₂ injection, there remains a notable gap in studies that systematically examine the interactions between deep microbial biospheres and geologically injected CO₂. Such understanding is essential for elucidating mechanisms and extents of geochemical CO₂ evolution under the subsurface microbial mediation. This paper comprehensively examines recent findings about impacts of CO₂ injection on deep microbial biosphere, and discusses microbial responses that are pivotal in determining the fate of the injected CO₂. Initially, the review addresses the influence of elevated CO₂ on geological chemistry, including pH, ionic strength, redox state and free energy distribution. Subsequently, it delves into the adverse effects of CO₂ on microbial growth, cell integrity, endospore generation, metabolism and community dynamics. Lastly, the review emphasizes key microbial activities that potentially facilitate in situ CO₂ immobilization, including CO₂ mineralization, methanogenesis and conversion to other valued chemicals. The objective of this review is to elucidate how elevated CO₂ levels affect geological microbiology, and how microbial responses impact the fate and speciation of CO₂ in storage sites, and to provide insights for optimizing future CO₂ storage strategies in geological formations.