the co2 is a good option and very easy to set up, when i mix mine i get a jug and put the suger in a jug then add warm water, if its to hot it kills the yeast and if its to cold it wont activate the yeast, so just warm water added to the sugar then mixed up so the sugar disolves, then pour this into the 2ltr bottle, the the same with the yeast but i use a mug and fill 3/4 again with warm water then add the yeast and stir it in, then add it to the bottle and top off with luke warm water or water strait out the tap if the water in the mix is warm enough.
the only thing different i do is i use 2x 2ltr pop bottles, one has the yeast/sugar mix in it, then i have another pop bottle 3/4 full with cold water, i then poke 2 holes in the lid of the bottle with just the water in so you have an inlet and outlet hole, then take the tube from the yeast bottle and push it into the water bottle and down to the bottom below water level, then i get another tube and push it into the other hole but only about an inch so its just inside the bottle but not in the cold water,
then when the yeast goes out the first bottle it then goes into the other bottle and bubbles in the water which acts like a scrubber and removes the smell, then it bubbles up and out the other tube and goes to the plants, in the winter i just use 1x 2ltr bottles but im summer the yeast and sugar attracts the bugs to running 2 bottles stops the smell and the bugs stay away
always rememer that co2 is heavier than air so you either need to run tubing above the plants or around the plants so it has holes poked in it that the co2 can fall out of, or the method i use is mount the tube to the back of a 12v fan then have that blowing across all the plants, then i have another 12v fan blowing cool air up from the bottom of the grow room so any co2 thats settled at ground level gets blown back up into the plants, i run 2 x 12v computer fans off an old mains adaptor, its not even running at 12v i think its running them at 9v so its enough to just move the plants and push the co2 across them.
some of the
sponsors sell co2 cans that stay active for 3 or 4 weeks if i remember right, someone was trying them a while back,
here is a link to the co2 generator page, just use 2ltr pop bottles instead of the gallon or milk jug things its on about, i use 2 x 2ltr pop bottles but you could use 1x 2ltr pop bottle then have the filter as a 500ml pop bottle, if you click on the link it will give you everything you need, then if you scroll down a few posts it will show you the filter method,
actually let me upload a pic and ill show you mine
hope you dont mind me posting it here but might help others understand what im on about,