Small is the New Large: Demonstration of how Microanalyses Elucidate Large‐Scale CO ₂ Uptake Through Mineralization

ABSTRACT Safe and permanent storage of CO ₂ via Carbon Capture and Storage (CCS) technologies is required to limit global warming to 1.5°C–2°C above pre‐industrial levels. In situ mineralization of CO ₂ within reactive formations or silicate‐rich materials containing Ca‐ and Mg‐bearing minerals, such as cement and basalt, is a potentially rapid and secure method of geological CO ₂ storage. We review how advanced imaging techniques including X‐ray microcomputed tomography and electron microscopy can be integrated to understand the CO ₂ mineralization process at the microscale. We highlight how novel methods, including correlative microscopy and machine learning, are pivotal in studying complex reactions within heterogeneous samples. We explain how integrating microstructure analysis increases the reliability of reactive transport modeling and consequently improves the CO ₂ storage capacity assessment. Furthermore, we discuss challenges that need addressing to improve accuracy in measuring properties like reactive surface area and highlight the key areas for future research, including method validation and error estimation of properties acquired through imaging. While image analysis offers profound insights into CO ₂ mineralization, significant advancement is required in segmentation accuracy and reproducibility. Furthermore, using experimental observations from studies of cement and basalt, we suggest a decision tree for assessing the suitability of formations for CO ₂ mineralization.