Obviously, any exhalation would still be mostly nitrogen gas, close to what you breathe in (78% in atmosphere).
I HOPE you're just suggesting the ballon thing as a joke, either that or you should abstain a bit before posting.
A simple one gallon fermenting container will provide a slow continuous supply of CO2 for 3-4 weeks. Not a great solution, but not bad if you just have cirrculation fan in a small area and no venting fan to suck out extra CO2 along with heat. No screwing with ballons with pinholes that may last all of a few minutes, if that long.
One recipe:
One gallon jug (from Arizona Tea for example). 3c sucrose (table sugar) boiled in 5c H2O for 5min to help break disaccharide into component glucose/fructose (easier for yeast to munch), another 5c cold water added to boiled sugar solution (cold to speed cooling off), 2c apple/grape juice (or similar) to provide acidity and protiens for the yeast, and another 2c room temp H2O with yeast started. After yeast has had a chance to hydrate (30min?) add it in, IF solution's cooled down enough. Temp shock kills yeast. Add a bubbler to watch CO2 production if you want (airline tubing from fermenter sealed with silicone sealer -> submerged into smaller bottle filled 1/2 with water). Replace as CO2 bubbles slow significantly. Not sure what's a good amount, but probable depends on room size/# of plants. Add more fermenters and stagger deployment (ie. 3 gallons, replace oldest one each week) to keep CO2 levels even.
Airline tubing, tube connectors, silicone sealant/sealer can all be found with aquarium supplies at local store like walmart.
As a bonus, take extra care to rack (remove liquid, leaving dregs) the fermented brew after 3-4 weeks (and rack again, and again) and you'll have a drinkable 'wine' in a couple months too. If you want to try this, you also need to take care to sanitize the frementer/racking container prior to use.
More info and example can be found by searching for DIY co2 (for aquariums).
theres only one place to go paintballing around here and its 30 minutes away. and it cost 250 to play... theres a place acros the street from the paintbal store where people play and they made it better than some of the feilds I've been to... and its free... you just need to bring people or be lucky enough to run into some.
