I’ve been playing with sugar and yeast as a method to raise CO2 in the grow room. Here’s what I’ve found.
I tried the bottle / aquarium tubing models you see on YouTube. No success there as it didn’t up the ppm in my 5x5 tent enough to make a difference.
I then tried an open bucket. The bucket was perhaps a 2 gallon size. I filled it 1/3 with lukewarm water and then added 2 cups of sugar and a couple of heaping tablespoons of active yeast. This did raise CO2 an appreciable amount; however, there were other problems that came up. It did raise CO2 in the grow room to 850 to 900 from 550 to 600.
If you do this then you need to be prepared to change out your bucket daily, as foul smells develop despite the main by-products of the reaction being vinegar and CO2. You also need to be aware that mold will develop in the bucket after more than 36 to 48 hours. The mold can be a health problem and also disastrous to your crop.
If you want to use sugar and yeast, then be prepared to do some work to keep it going properly.