It is now the practice to blast whole hillsides and hilltops into the adjacent valleys, ruining both, for the sake of "the USA's cheapest fuel"
Obviously, once you've acquired the coal by these means, you've forfeited the right to call it 'clean', no matter how you consume it.
|Carbon Dioxide (CO2)||2,459,800|
|Sulfur Dioxide (SO2)||9,524|
|Nitrogen Oxides (NOx)||3,799|
These problems are much worse, when you consider the particulates going up the exhaust flues. The thorium and uranium oxides in a year's worth of coal burning by a one gigawatt plant are enough that they exceed in radioactivity the amount that would get a nuclear plant shut down. Even although, in fact, the much greater quantity of lung-irritating other fine dust is a much greater health threat than the radioactivity.
"CCS" (Carbon Capture and Storage) projects will be capturing and storing 2.67 times as much oxygen, by weight, as carbon. It would be more correct to call the technology Oxygen Capture and Storage (OCS)!
At present rates of CO2 production, we would run out of oxygen in less than a million years. That seems like a long time, but it's the same order of magnitude as the existence of the genus homo.
Carbon dioxide is a gas, which has to be compressed by a factor of a thousand to reach a density comparable with water. Compressing a gas costs energy, so you'll have to burn more fuel per gigawatt-hour of output electricity. Carbon dioxide does not "decay" like radioactive waste. You have to bury it forever. Compared with nuclear waste, per unit of energy -- say per gigawatt-year -- the mass, let alone the volume, of carbon dioxide produced is millions of times bigger. And it leaks more easily, and once started, probably more catastrophically.
The idea of "sequestering" gigatons of carbon dioxide is surely far less attainable than the disposing of mere kilotons of nuclear waste.
A kiloton is a thousand tons
A gigaton is a thousand million tons.