I was thinking of ways of making carbon cleaner for the environment. One of the ways I came up with is filling a solar updraft tower https://en.wikipedia.org/wiki/Solar_updraft_tower with the exhaust from a gas/coal plant. So you'd get a true greenhouse gas accumulation of heat going in the tower which will allow for a much smaller/realistic footprint/collector section of the tower. My concern, however, is that it will get very hot in the tower plus light from the sun and plus time will result in very toxic smog?! It's been on my mind so let me know . . .