It matters not how clean coal can be made to burn. What matters is how much it cost to produce a BTU from it.

The answer currently is that coal is expensive when stacked up against natural gas.

The coal industry can whine all it wants about regulations and whatever, but there is not a power producer out there that cares one bit about their troubles. All they care about is producing power at the lowest cost, and even coal mining that is totally automated cannot compete with Natural Gas.

It's all about the $$$$$$$.