"The rock powder, usually basalt, is often scavenged from local mines or quarries, where it exists as a waste by-product. ERW companies collect the rock powder, sometimes milling it further to reduce the grain size. Then they truck it to farms, where it is used in place of ag lime.
Studies show that volcanic rock dust can raise the pH of overworked soils, improving productivity." Modern Farmer
There’s a couple things to consider here:
Any energy spent to crush the basalt produces CO2, making the process of C storage less efficient
Soil benefits would be slow because you’re relying on geochemical weathering. Elemental sulphur is used as an amendment and as you would expect, it drops soil pH, but the process has a lag time and the hoo boy it goes brrr. Conversely, rock phosphate is used, and that’s a pretty gradual release.
The C sequestration is likely slow and reversible.
Carbonates break down quickly. They’re also highly labile in the soil. Because of this it’s not a silver bullet. They can precipitate lower in soil profile, but they can also be brought to the surface with capillary action, and re-exposed/weathered.
I’ve seen some articles on using this concept for mining C storage, as tailings are ‘just’ rock dust and water, so they are looking at ways to convert tailings facilities to C storage facilities at closure, but it’s not there yet. Everything I’ve seen has been conceptual.
Back to farming, though, why not just use lime?
I’m not sure about the lime, but I just want to thank you for that great explanation!!