OK, I know that it’s been done before, but here is my take on it. Like any DIY CO2, it includes sugar, water, and yeast of course, but the yeast is proper wine yeast, some of the sugar comes from grape juice, and there’s a little lemon juice for proper acidity. My recipe is a simplified derivative of this award-winning version (White Niagara
First, I offer a note on the number and volume of reaction bottles. I know from experimentation that I need 2-3 gallons of actively fermenting solution to provide enough CO2 for ~150 gallons of planted tank. I could use a single 2 or 3 gallon bottle, but given the time it takes for a new solution to reach peak activity, and then the taper in the end, that would yield highly inconsistent CO2 production over the course. Better would be two 1.5-gallon bottles, better yet three 1-gallon bottles, and so on. What I have settled into is five 0.5-gallon bottles with one replaced every 5 days. At any given time, I have 3 bottles in near peak production plus 1 ramping up and 1 ramping down. Every 5 days I mix up a new bottle and harvest one. Quite nicely, this works out to about 1 glass of wine each for me and the mrs every night at dinner. Cheers. Now the details:
For each half gallon batch, I use:
- (1) 11.5-oz can of Welch’s “100%” frozen concentrated grape juice (yellow lids denote 100%, white lids are their cocktail mixes), any flavor. They have red, white, raspberry, cranberry, and peach…all good. Some people make a big deal about not using any juice with preservative in it, thinking that the preservative could inhibit the yeast activity. In reality, (1) good luck finding a cheap supply of truly 100% juice; Welch’s is “100% juice…(tiny print at the bottom) with added ingredients” including preservatives; and (2) regardless, I’ve never had any issues getting the yeast going. Of course, you could invest in higher quality juice to yield a higher quality product (they say you can make a lousy wine with great juice, but you cannot make great wine with lousy juice).
- (1.5) cups sugar, any old granulated sugar. Just the grape juice alone does not have a sufficient amount of sugar; it would not ferment as long or as vigorously, giving less CO2 for your tank and less alcohol for your beverage. So I bump it up with the granulated. Between the juice and this amount of supplemental sugar, my hydrometer tells me this mix has the potential to yield 13% ABV (26 proof). In reality, the yeast dies off when the alcohol reaches about 10-12%, yielding a beverage with just a touch of residual sweetness. You can use less sugar if you prefer a drier wine product. If you prefer a lower ABV, you can also add sulfites to kill off the yeast at whatever ABV you desire.
- (1) teaspoon lemon juice. I know, lots of the DIY CO2 recipes call for baking soda to keep the pH up to supposedly make the yeast live longer. In my experience, it is not the pH that kills them, it’s the alcohol.
- sprinkle of wine yeast. I prefer Red Star brand and I use the varieties Montrachet and/or Premier Cuvee. I get the packets for $0.50 each at the winery/shop down the road. 1 packet usually does 5 gallons, so I can easily do 10 half-gallon batches from 1 packet (nearly 2 months) and probably twice that, keeping the packet in the fridge between uses. You certainly can start a new bottle with live yeast from the old bottle, but the more times you do that the more you run the risk of an ‘infection’ with a wild strain that could have off flavors. It’s only a nickel’s worth of yeast per bottle, not even $4/year, so I don’t cut that corner. If one wanted to get even more CO2 from the mix, and also a higher ABV, one could use champagne yeast: they survive to a higher ABV, but your final product will taste less like traditional wine.
- After these ingredients are in, add enough water to get the bottle a couple inches from the top (5.5 cups for me), leaving enough headroom for a little froth; you can top it up to a full half gallon after the bottle comes offline.
No mixing, no boiling (sterile-technique gurus gasp here), I just dump it all in the CLEAN bottle (rinsed when emptied, run through dishwasher on high heat setting). Yeast go in last so it doesn’t get buried under the sugar. Then let it sort itself out; it always launches no problem and the yeast do all the mixing. Depending on temperature, it takes a few days to get going strong. I get good CO2 production for ~3 weeks. Of course, rather than dumping the bottle when it’s spent, you can (1) put it on a pantry shelf for another couple months so it can completely finish fermenting and get a little age to mellow/mature, or (2) if you are really impatient you really can drink it immediately—it might have a little fizz to it, a little more residual sugar, and taste a little more like grape juice still than wine. But it is quite drinkable. Don’t get me wrong, this is not a top shelf product…we jokingly call it hobo wine, lol. My wife’s people are from the south and refer to such concoctions as Possum Holler Kool-Aid. Ah it’s not that bad. And it’s easily 1/10th the cost of store-bought cheap wines, plus you get the CO2 for your plants. Win, and win. Good luck with yours!