Hot coals are still burning, so they are still giving off CO and CO2. Take a look at the coals when you put them in the bucket and when you toss them out. Has the mass of the coals changed? If so, the lost weight is Carbon that has been given of as Carbon Dioxide and Carbon Monoxide.
I would be cautious about this, because the CO can kill you pretty quick, if you are not careful. Don’t know about the plants.
(PS. You’re destroying the planet with those evil Greenhouse Gases, etc... Not really, but you ask 10 non-FReepers this question, and that is the answer you’ll get from nine of them)
There have been volcanoes erupting continually since Earth existed each one discharging more GG in a day than all humanity does in a year.
The idea that CO2 destroys the planet is bizarre unless we understand the theory is agenda driven.