A plant tolerance index to select soil leaking CO2 bio-indicators for carbon capture and storage

Plant response to the leakage of stored CO2 is a key concern for safe carbon capture and storage (CCS). An understanding of plant tolerance to high soil CO2 concentrations is urgently required to facilitate bio-indicator selection for both long-term environmental monitoring and prevention of stored CO2 leakage. In this study, we propose a new index, the Leaking CO2 Tolerance Index, LCTI, which assesses plant CO2 tolerance using the change (downward shift) in index values under leakage treatments. The calculated LCTI reveals that, of the four studied plants, clover was the most tolerant (0.42), followed by alfalfa (0.4), teosinte (0.33), and finally maize (0.29). Our results suggest that clover, along with other high-LCTI species, should be selected as species that can potentially adapt and respond to CCS leakage. Furthermore, plants such as maize appear suitable as bio-indicators to monitor carbon storage fields, allowing early detection of CO2 leakage.