Baltruschat et al. (2026): Assessment of solid ikaite release into seawater – implications for ocean alkalinity enhancement
Stefan Baltruschat, Jens Hartmann, Niels Suitner, Charly A. Moras, Carl Lim, Laura Bastianini and Phil Renforth, IN: Applied Geochemistry, https://doi.org/10.1016/j.apgeochem.2026.106781
Alkaline feedstocks for ocean alkalinity enhancement (OAE) must guarantee efficient alkalinity release while having limited impact on marine ecosystems and carbonate mineral saturation levels (ΩCaCO₃). When considering mineral powder addition as a deployment option, currently considered feedstocks either exhibit slow dissolution kinetics or may require additional water treatment to limit rapid pH changes. Carbonate minerals, on the other hand, feature fast dissolution when undersaturated, accompanied with a reduced impact on pH and ΩCaCO₃. However, traditional (non-hydrated) carbonate minerals such as calcite and aragonite are insoluble in seawater and therefore impractical as direct-to-use feedstocks for OAE. Here, the authors examine the dissolution kinetics and alkalinity release efficiency of ikaite (CaCO₃·6H₂O) — a hydrated carbonate mineral producible from limestone and dissolvable in seawater — across a range of global sea surface temperatures through a series of controlled laboratory-scale experiments.