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The Future Forest Company spreads basalt on forestland for carbon sequestration [1].

Wren offers it as one of its carbon offsets [2]. However, it is currently the most expensive of their offset programs, per ton of carbon offset or removed, and significantly so.

[1] https://www.fastcompany.com/90642582/this-company-is-crushin...

[2] https://www.wren.co/projects/mineral-weathering-in-scotland

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I think these mineral weathering programs may make the most sense when applied to the oceans, where they both sequester carbon and directly reduce the ocean acidification that is harming marine life. This is especially the case if wave action on beaches can reduce the amount of energy required to grind and distribute the rock. There also seems to be potential for additional capture by the iron content of the rock fertilizing the growth of phytoplankton in areas where that wouldn't be harmful to other marine life like coral. In areas with tropical coral adding Calcium both reduces acidity and helps shell building creatures.

I am also leery about spreading mountains of silica dust on fields where it can be blown in the air and end up in our lungs eventually.

re phytoplankton/marine life: I guess basalt particles will sink. But if sinking is slow the top layer will get murky absorbing the light.

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