It's a natural process and we just have to mine as many rocks as we dig up oil. We just need to catch up for the last few hundred years where we only dug up oil and no rocks. It still seems like the least expensive option.
It is certainly an option, but likely not enough. Even catalysed, the rock work very slow and require additional power input to maintain at optimal condition.
The other problem is transporting them rt places where they would be most effective - near cities and factories.
The other problem is transporting them rt places where they would be most effective - near cities and factories.