Study: Grind rock to fine dust for OAE to work
A new modeling study suggests that one of the more promising ideas for removing carbon dioxide from the atmosphere — adding crushed alkaline minerals (e.g., olivine) to the ocean — may be far less effective than many advocates assume. Researchers at the University of Bern find that much of the carbon-absorbing benefit from ocean alkalinity enhancement (OAE) is lost when mineral particles dissolve below the ocean surface rather than at it.
Using a fully , the study shows that olivine particles only a few larger than ideal for dissolving in ocean water sink hundreds to thousands of meters before dissolving, delaying carbon uptake by decades or longer.
An ideal particle diameter for olivine in OAE can be around 1.7 microns (for comparison, the particle diameter of household talcum powder is typically between 1 and 10 microns). When the particle size of olivine is double the ideal size, carbon capture efficiency can fall by more than 75% in the first ten years, with much of the absorbed carbon appearing far from the deployment site — posing major challenges for monitoring, verification, and carbon crediting.
The findings underscore a major trade-off facing mineral-based ocean carbon removal: grinding rock finely enough to dissolve near the surface sharply raises energy use and emissions, while coarser grains undermine effectiveness of carbon removal. The authors conclude that open-ocean mineral alkalinity enhancement may be substantially less reliable than some previous models, calling for more cautious assessments of its role in climate strategies.