Regional variations in the potential for CO2 removal through enhanced rock weathering in aquatic environments

One strategy for lowering atmospheric CO₂ levels is enhanced weathering, which involves dispersing rock powder to accelerate natural weathering. One obvious application area would be seawater. Because weathering is a chemical reaction, it is influenced by environmental properties like temperature and physical properties like the reaction area.

This study looks into the variability in sequestration rates from spreading of olivine at 13 distinct regional coasts around the world, including those with warm and temperate climates. Furthermore, sensitivity analysis was performed with various combinations of influencing parameters (grain size and seawater temperature) to determine the effects of individual parameter combinations. A 100-year simulation was conducted using geochemical thermodynamic equilibrium modeling (PHREEQC).

According to the simulations, over a 100-year period, CO₂ uptake from atmosphere varies significantly between the seas, ranging from 0.13 (Black Sea) to 0.94 (Banda Sea) tonne (t) CO₂ per t of olivine at a grain size of 100 μm. The difference between warm and temperate region’s atmospheric CO₂ uptake is 0.4 t CO₂ per tonne of olivine dissolve in seawater. A subsequent sensitivity study of parameter combinations reveals that the Black Sea can reach 0.8 t CO₂ consumption rates per tonne of olivine if the material was ground to a grain size of 19 μm while the Banda Sea can reach the same amount of consumption rates at a grain size of 150 μm. The study results suggest that there are large differences of enhanced weathering speeds between different regions.