You do realize that coal then gets dug up and burned, right?
Also, have you heard of fracking? It's a blend of the words "cracking" and "fracture" and why is that? Like virtually any geology, there are cracks, through which, for example, gasses, like methane or in this case CO2, can escape. Coal beds also happen to be riddled with fractures and cracks. So even if you don't dig up the coal, "should absorb" is pretty weak for something we would be betting our future on.
Also, have you heard of fracking? It's a blend of the words "cracking" and "fracture" and why is that? Like virtually any geology, there are cracks, through which, for example, gasses, like methane or in this case CO2, can escape. Coal beds also happen to be riddled with fractures and cracks. So even if you don't dig up the coal, "should absorb" is pretty weak for something we would be betting our future on.