My readings in geotherapy and ecological restoration lead me to believe we could do quite a lot to remove CO2 from the atmosphere by doing what we already know how to do in agriculture, forestry, and, most effectively and quickly, mariculture if we did it consistently and globally.  

Best resources I know of on these topics at
http://solarray.blogspot.com/2021/04/geotherapy-not-geoengineering-please.html.

PS:  Existing forests sequester more CO2 than newly planted tree farms.  Expand the biosphere and don't do monocropping, please.

Solar IS Civil Defense