I can't even claim to know where I found this article, as I have been doing so much research on so many topics lately... so I'll just share what I have saved...
(Found this by searching for the title below): Making a homemade CO2 Generator
Items Required:-
* 10lb. white sugar-
* 5 gallon clean bucket W/lid-
* 4 1/2 gallons of water-
* A piece of toast browned and hard-
* A table spoon of dry active yeast (for baking bread)-
First boil the water, (this will ensure clean water) remove from the heat and add the sugar. Stir until sugar dissolves. Let cool until water is room temperature (if you don't let it cool down it won't work).-
After the sugar water has cooled, float the piece of toast on top of the water. Now, empty the tablespoon of yeast over the toast. After a few days, the yeast will take over the toast and start making bubbles (CO2) in the bucket. After a week, the amount of bubbling (CO2) will increase.-
Keep the lid airtight on the bucket. CO2 travels up the dispersion tubing, and due to it being heavier than air, falls directly onto your plants. Timing your exhaust, is essential in maintaining an effective level of CO2.-
Note:-Unfortunately the author of this contribution has not been able to test the CO2 levels produced using his method. Personally, I would use a CO2 analysis kit to help manage (exhaust timing etc), and maintain, an optimum level of around 1500PPM.
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What I do know based off from personal experiences, when you make alcohol or bread and yeast mixes with sugar (honey, sugar, etc...) it will produce carbon dioxide that is what makes breads rise, and that is what we wait for in the making wine. But as I have seen people commenting under this topic when I was researching it, if something goes wrong with the vent tube venting the CO2 gas, well it can make a seriously huge mess. Others pointed out that its a waste to make your own CO2 buckets such as above because of the control issues of being able to regulate the CO2 as a guaranteed PPM, as anything less than 1000 PPM is a waste of time and won't have any real effects on the plants.
I have seen these "CO2 Bags" for smaller spaces, and I couldn't believe the price they wanted. I will be honest I'll go without CO2 before I pay that kind of price and then have to dampen it everyday just to work.
I have seen a bucket CO2 for sale which was ranging from $40 to over $100, but it seemed reasonable for the price and when they say it would last 7-months. They also discussed NASA having and interest in this for the mission to Mars, which makes sense... But after doing a search on here and reading what others here and some other places have had to say about them, to be honest I have really questioned how worthwhile it really would be, when again I can't ensure one bucket alone will give me the 1000+ PPM I am looking for.
Then of coarse there is the CO2 bottle approach, I was questioning a smaller CO2 tank like that being used for soda machines, but the gauge to regulate it was over $100, plus you have the filling of the bottle, hydro tests on the bottle (every 5-yrs & has to pass inspections). I found one of these on Craigslist for $50 used, but I'd have to drive nearly 3-hours to get it, and then fill it... But at least with this type of a design if I need more, I twist a nob, and if I need less I twist the knob. I have a pressurized tank I have to transport to get refilled sure, but that can last me a lot longer than 7-months, and when I'm doing the real hard core math it suddenly for me anyways seems the more logical and reasonable way to go for my small grow space and the arrangements I have.
But all of this is what has brought me here today to do research on, as I am scouring around and do more learning and research on now so I can make the best decisions for me short and long term.
