Technology
Enhanced Rock Weathering is a carbon dioxide removal technology strategy that accelerates the natural process of rock weathering to capture and store atmospheric CO₂. In nature, this process occurs over thousands of years and longer, as rocks slowly react with CO₂ and water, releasing cations and converting CO₂ into bicarbonate and carbonate ions in water. Enhanced weathering speeds up this process by selecting reactive rocks—such as ultramafic and mafic rocks like dunite and peridotite—grinding them into fine particles, and spreading them over land. By increasing the surface area of the rocks, enhanced weathering promotes their ability to react with CO₂, making the process significantly more effective. Once dissolved, the carbon can remain trapped in water as bicarbonate or carbonate ions or eventually form solid carbonate minerals, which provide long-term storage. Some of this dissolved carbon is transported to the ocean through runoff, where it can be stored for tens of thousands of years or longer, helping to mitigate climate change.
The efficiency of enhanced weathering depends on multiple factors, including rock type, particle size, soil conditions, and climate. Smaller rock particles dissolve faster because they have a larger surface area available for chemical reactions. However, grinding rocks to very fine particles requires energy, creating a trade-off between reaction efficiency and the overall energy cost of the process. Once spread on agricultural fields or forest soils, these minerals interact with soil microbes, which can further enhance their breakdown and reaction with CO₂. The local soil pH also plays a role, as acidic soils can speed up mineral dissolution, making the process more effective. Additionally, temperature influences the efficiency of the technology: lower temperatures allow more CO₂ to dissolve in water, whereas higher temperatures increase the rate at which minerals react with CO₂ and water. As the rocks dissolve, they release important nutrients into the soil, increasing its alkalinity and potentially benefiting plant growth. Over time, carbonate minerals may precipitate, permanently locking away CO₂.
Pilot studies
The Pasek Minerales is located in Galicia, NW of Spain, where the dunite mine, the dunite (magnesium silicate), is an ultramafic rock. In the Pasek facilities, a pilot has been carried out that supports several technologies (Fig. 1).
Plots 5 and 6 are those that were destined to verify and quantify CO2 capture.
Fig. 1 – Satellite view of the plots belonging to Pasek trials.
Fig. 2 – Installation of the different materials according to technologies.
Firstly, it made a comminution of the mineral up to reach 0/3 (Fig. 2), with 3 mm as a maximum particle size (Fig. 3), this was spread in both plots, the first of them, is working as a control plot, the second one posse the same size particle, but it was added native species of trees and shrub species, gramineous and legumes (Fig. 4).
Fig. 3 – Dunite 0-3 mm used in the control plot and plot number 5.
Fig. 4 – all plots planted except for the control plot.