diy co2

Once it reaches a certain level the alcohol will kill the yeast. Slightly before that level it will kill some of the yeast but not all of it and the survivors will bounce back -- yeast can double in population overnight. I've successfully caught the mix as production starts to drop and replaced the 75% of the old solution with a fresh batch of sugar water. I've also failed to pay attention for a few days and let it get by me. Champagne yeast is more active at the bottom so I siphon off the top and leave the husks of dead yeast at the bottom to feed the next culture (lipids, proteins and minerals, all good stuff). Alternately, you could draw off a portion from the most active area and add it to a fresh mix as a starter culture.

A handy DIY bubble counter is helpful -- a small bottle with an airline in almost to the bottom, filled part way with water, and an airline out almost at the top. It also doubles as a safety trap to help prevent foamover into the tank.

Using champagne yeast instead of bread yeast and locking up a portion of the sugar in Jello-shots are two other techniques for getting longer and more stable DIY CO2 production.

Here is the best article I've ever seen on DIY CO2. It covers a lot of this in detail. The "Gas Separator" is an odd variant on the DIY bubble-counter -- picture the "rigid tubing" (doesn't really need to be rigid) going almost to the bottom and the bottle filled 1/3 with water. It will separate out solids as the article mentions but the CO2 will also bubble through the water: 36 bubbles per minute, 42 bpm, 48 bpm, 44, 38, 30…. This will make it much easier to "catch" the mix. The starter culture mentioned is also a very solid technique I picked up off a winemaking site.

Anonapersona, a solid and knowledgeable member here, has a great thread going on another board detailing their experiments with DIY CO2. An interesting read.

HTH

What you're proposing sounds higher maintenance to me than just starting over once it starts to taper. After all, none of the ingredients, except maybe sugar, are expensive. And you wouldn't be able to reuse sugar anyway. Rather than try to revive it every week or so as you suggested, try the Jell-O recipe. I think it's becoming my mission here at AC to convert everyone to Jell-O. Trust me, once you try it, you won't go back! It's a lot more stable and lasts 2-3 months on average. I think it's well worth it to spend a bit extra time preparing it. Do a search on AC or search engines to find different recipes, or read mine here: http://aquaplants.web1000.com/art1.html

Some folks use plain gelatin (Knox seems to be a favorite brand). I don't think there's a whole lot to it that would get in the way of distilling it if that's what you wanted to do. Mostly its just a slow-release matrix for the sugar. I favored the thicker Jello-shot (jiggler) recipe, cut into small cubes and dropped them into the top of the bottle. Worked.

The rest of it was just siphon off a good bit and replace with fresh. New cubes in with the mix. No real change in the maintenance.
I think the bubble counter is an important safety device, whether or not you want to actually keep a running log. Anonapersona has kept a detailed log running in their thread, testing different variables against each other and learning quite a bit. After the first little bit I just sort of kept an eye on it: hmm, starting to slow, not actually counting or keeping notes.

Most reports are for better and safer results with champagne yeast over bread yeast. YMMV.

If you're thinking of doing this on a large scale I think your sugar costs are going to be much greater than your yeast costs. Look into some homebrew/winemaking shops. There are plenty on the web, but if you can find one locally the folks tend to be friendly and talkative.

Before I decided to bail in favor of pressurized I was thinking about researching Sake. Rice wine, the starch breakdown taking the place of the jello matrix, slow and stable and (if you are thinking large scale thoughts) much cheaper. But I didn't go all that far down that road…