I saw this in my searching. Might have been a post on another site. Unknown poster. I use it but cannot attest to it's usefulness yet. Still trying to work out the kinks in my way under budget grow space.
Co2 from fermintation................This is for some what low levels of Co2 production. First a list of supplies.
1. A plastic 1 gallon tea jug
2. about a foot or two of fishtank hose.
3. 3 cups of sugar
4. Bakers Yeast from a regular grocery store.
Basically all u do is put the sugar and yeast into the jug, fill with warm water, to about an inch from the top. Poke a hole in the lid for the hose, make sure it's tight. Place hose alittle way in, dont touch the mixture. Shake up ur solution. Now once u got it mixed up just take the jug put it in the grow room and place the other end of the hose in a cup with very little waterjust barley cover the hose. and basically it could take from 3 minutes up to 3 days to activate the soulution. The cooler the water the longer it takes to activate. Most of the time, by the next morning just shake it, and ur hose in the glass should produce some bubbles, between 1 every 3 to 30 seconds. And the reason it's in a small cup is, one just so u know it's workin, and 2 so the Co2 can escape into the air. If u have the hose in to much water the the Co2 will disolve into the water and not the air. Co2 meters are expensive so the exact amount of Co2 added to the air is not specific, but in growth trials plants have been known to double in 3-4 weeks. Note this solution only stays active about 3 weeks, and a bigger jug will not make it last longer. To add more Co2 just add more jugs. But remember to shake the jug every day or two. With practically no overhead cost, I hope to here of some peoples trials with this info, thanx and happy growin.....