When it comes to coal these efforts and those who support them seem to always make the assumption that there is nothing that can be done to make burning coal "cleaner". After working with the utilities industries (mostly natural gas industries) I can tell you with 100% certainty that more than 80% of the by products from the burning of coal, including CO2, can be removed using scrubbing technologies and filters. In many cases the cost to install these technologies are lower than the costs to convert a plant to natural gas. The problem is that EPA regulations on coal are driving the costs up (by making it harder to mine and transport) to the point where in the long run natural gas is cheaper (though get a change in the US administration and that could sway the other way again)(Edit: Which is why a lot of coal plants are being converted to natural gas). My point is that if coal didn't cost as much as it currently does (because of federal regulation) a number of technologies could be installed that would enable coal plants to continue to be used with much much less environmental impact.