Adding chemicals to reduce pollution is how every internal combustion engine works, especially diesel engines.
Sodium reacts explosively with water, Chlorine is a lethal substance to humans yet when the two chemicals react they become a necessary part for our bodies. There are ways to turn toxic/harmful materials into harmless ones by adding more chemicals. The key part is making sure the result is actually harmless, which we can.
Edit: also in how far would we need to strip earth further for this solution? In this scenario we're already mining asteroids in space and there are (to my knowledge) no natural materials we can find only on earth, if anything there is stuff we can't find on earth but do in abundance in space (like Helium).