There is no such thing as clean coal. Coal is a dirty source of energy and any technology that makes it burn cleaner is just mitigating the damage. We should focus on truly clean sources of energy such as solar, wind, and geothermal energies. These are the technologies that will power us in the future and help fight global warming.
Though coal is the primary energy source of the United States, it is a horrible polluter. Not only does the combustion of coal, a hydrocarbon, release CO2 into the air in huge volumes, it also produces toxic particulates and smog. Coal is also non-renewable, so depending on it the way we do is a recipe for economic disaster in the future.