Now this is an interesting thought. It really applies to me (it's #3). How much validity is there? I used yeast to make co2 in my grow room.
#1. Plants will use as much CO2 as they are given-- the danger is to the PEOPLE if you use a generator with out a monitor or emergency shut off-- the plants';ll be happy--U B dead!
#2-- the yeast thing does work-- but how much it puts out is iffy... and they only work for a few days before the yeast consume all the sugar then die... you can tell by shaking the jar (or whatever you're using) and if it fizzes-- it's still good... if not- dump it.
#3- you are taking a chance of introducing mold into your grow if it Spurts (often they do) or gets spilled. And yeah-- they smell..
And I had a big problem with mold and was unable to find the source. Cleaned the room. took everything out, spraying with bleach solution, repainting, rehanging lights (after thorough cleaning with bleach also).
You can get the same type of results by doing home-made wine in the growroom (at least 2-3 feet from the plants!) then the plants AND YOU benefit!