Process modelling and analysis of ikaite production for atmospheric CO2 removal through ocean alkalinity enhancement

[Geoengineering News]

https://www.sciencedirect.com/science/article/pii/S0263876225006872

Authors: Xuesong Lu, Rachel Millar, Pranav Toutam, Aidong Yang, Spyros Foteinis, Laura Bastianini, Phil Renforth, Stefan Baltruschat, Jens Hartmann

https://doi.org/10.1016/j.cherd.2025.12.028

18 December 2025

Highlights

•Ikaite production process for atmospheric CO2 removal was designed with pressure swing.

•Processes including calcite dissolution with CO2, degassing and crystallisation have been modelled.

•Key factors influencing ikaite production process have been exploited and analysed.

•Results of this work could provide a guidance for production of other minerals.

Abstract

The production of ikaite, a metastable calcium carbonate hydrate, offers a promising pathway for atmospheric CO2 removal through ocean alkalinity enhancement. This study explores the feasibility of ikaite production through a three-step process, involving calcite (CaCO3) dissolution under elevated CO2 pressure, CO2 degassing from the calcium carbonate rich solution, and subsequent crystallisation. Here, a mathematical model was developed and validated against experimental data, and the effect of key operational parameters was examined. The calcite loading/dosage, particle size and CO2 pressure for dissolution, seed loading and particle size for crystallisation, and degassing pressure as critical factors have significant impact on process efficiencies. Under optimal conditions, involving CO2 pressures of 2 bar for dissolution, 0.01 bar for degassing, and 0.001 bar for crystallisation, with seed loading of 5 kg/m³ and seed particle sizes of 3 μm, the process achieved steady state ikaite production of 1.64 kg/m³ from a calcite feed of 0.83 kg/m³ . This investigation demonstrates the technical viability of ikaite production through CO2 pressure swing and informs its future development as a potential contributor to climate change mitigation.

Source: ScienceDirect