Stability of alkalinity in ocean alkalinity enhancement (OAE) approaches – consequences for durability of CO 2 storage

作者：Jens Hartmann, Niels Suitner, Carl Lim, Julieta Schneider, Laura Marín-Samper, Javier Arı́stegui, Phil Renforth, Jan Taucher, Ulf Riebesell · 发表于：Biogeosciences · 年份：2023 · DOI：10.5194/bg-20-781-2023 · 被引用次数：156 · 研究领域：Ocean Acidification Effects and Responses、CO2 Sequestration and Geologic Interactions、Carbon Dioxide Capture Technologies

According to modelling studies, ocean alkalinity enhancement (OAE) is one of the proposed carbon dioxide removal (CDR) approaches with large potential, with the beneficial side effect of counteracting ocean acidification. The real-world application of OAE, however, remains unclear as most basic assumptions are untested. Before large-scale deployment can be considered, safe and sustainable procedures for the addition of alkalinity to seawater must be identified and governance established. One of the concerns is the stability of alkalinity when added to seawater. The surface ocean is already supersaturated with respect to calcite and aragonite, and an increase in total alkalinity (TA) together with a corresponding shift in carbonate chemistry towards higher carbonate ion concentrations would result in a further increase in supersaturation, and potentially to solid carbonate precipitation. Precipitation of carbonate minerals consumes alkalinity and increases dissolved CO 2 in seawater, thereby reducing the efficiency of OAE for CO 2 removal. In order to address the application of alkaline solution as well as fine particulate alkaline solids, a set of six experiments was performed using natural seawater with alkalinity of around 2400 µmol kgsw −1 . The application of CO 2 -equilibrated alkaline solution bears the lowest risk of losing alkalinity due to carbonate phase formation if added total alkalinity (ΔTA) is less than 2400 µmol kgsw −1 . The addition of reactive alkaline soli...