Applying rock dust to croplands could absorb up to 2B tonnes of CO2

Mine waste of the correct kind will indeed absorb CO2. The rightn type can be found as small particles and even nearly dust. However, some mine dust contains toxic metals, Chrome, Arsenic, lead, copper in acidic form as acid mine drainage. So what you spread on your crops or pasture or even waste land must be chosen with care. That said, there is a lot of the right rock to make a difference at only the cost of haulage.

https://en.wikipedia.org/wiki/Acid_mine_drainage

This would affect soil drainage and ruin valuable land. We would run into food shortages.