14. You could. Some algae-to-biodiesel proposals suggest coal plants as a CO2 source
To grow their algae in vats.
The problem is that we can't afford to keep burning ANY coal if we want to salvage this civilization, even if the carbon is (temporarily) diverted into another fuel before being released into the atmosphere. All coal plants, most oil-burning vehicles, and most nat. gas plants as well, need to be shut down in the next few decades to stand a snowball's chance in hell of keeping some civilization left on this planet.