0) Donor government identifies a country where acid soils are already cultivated for agriculture. The recipient country should also be reasonably stable so you don't have to plan around armed conflict. Palm oil production in Malaysia looks like a good candidate. It's important to get buy-in from the (potential) recipient country's government too.
1) Within the chosen country, identify a region that has a lot of acid soil cultivation and that has easily accessible deposits of ultramafic rocks nearby. (Shouldn't be too hard, as such rocks are very common.)
2) Provide electrically powered crushers and/or grinders for size reduction, plus power sources if remote from the grid (ideally solar, maybe diesel generators as are common for mining sites; even if it's fossil powered the net CO2 is deeply negative). There may be some necessary R&D optimizing said crushers for low-maintenance conditions, since ultramafic rocks are among the hardest and toughest.
3) Pay locals to run the crushers and transport discounted-or-free rock dust to farmers in place of limestone. There might be some gaming of the system if e.g. drivers are really just dumping rock dust on the nearest empty land instead of finding farmers to take it, but that's tolerable. The project is already 75% done if you just get the rock crushed to dust in the first place. So key metric is ensuring that the crushers are still operable and are actually being used to crush rocks as intended.
Another idea, after I've written this out: there is less but still some acid soil under cultivation in the richer nations of the world, e.g. parts of Australia. Might want to try it first in the developed world where monitoring, language barriers, and infrastructure are all less challenging.
EDIT: a somewhat less effective but still potentially interesting idea is to put the ground rock in near-shore ocean environments where wave action will help abrade/weather the particles. Probably not as good as acidic warm soil in the tropics, but still a speedup over the natural way.
0) Donor government identifies a country where acid soils are already cultivated for agriculture. The recipient country should also be reasonably stable so you don't have to plan around armed conflict. Palm oil production in Malaysia looks like a good candidate. It's important to get buy-in from the (potential) recipient country's government too.
1) Within the chosen country, identify a region that has a lot of acid soil cultivation and that has easily accessible deposits of ultramafic rocks nearby. (Shouldn't be too hard, as such rocks are very common.)
2) Provide electrically powered crushers and/or grinders for size reduction, plus power sources if remote from the grid (ideally solar, maybe diesel generators as are common for mining sites; even if it's fossil powered the net CO2 is deeply negative). There may be some necessary R&D optimizing said crushers for low-maintenance conditions, since ultramafic rocks are among the hardest and toughest.
3) Pay locals to run the crushers and transport discounted-or-free rock dust to farmers in place of limestone. There might be some gaming of the system if e.g. drivers are really just dumping rock dust on the nearest empty land instead of finding farmers to take it, but that's tolerable. The project is already 75% done if you just get the rock crushed to dust in the first place. So key metric is ensuring that the crushers are still operable and are actually being used to crush rocks as intended.
Another idea, after I've written this out: there is less but still some acid soil under cultivation in the richer nations of the world, e.g. parts of Australia. Might want to try it first in the developed world where monitoring, language barriers, and infrastructure are all less challenging.
EDIT: a somewhat less effective but still potentially interesting idea is to put the ground rock in near-shore ocean environments where wave action will help abrade/weather the particles. Probably not as good as acidic warm soil in the tropics, but still a speedup over the natural way.