The concoction on page one yields a specific gravity of around 1.081. For you beer and wine drinkers, that's enough sugar to produce 10% alcohol assuming complete attenuation. Maltose isn't 100% fermentable but sucrose and dextrose are. At those potential alcohol levels, you'd need 14 billion cells of yeast at the standard pitching rate of one million cells per ml of liquid per degree plato to properly attenuate the mixture. 14 billion yeast cells is about 1 gram of yeast.
The reason the outlined recipe for this method is bunk is that one litre of liquid at your pitching rate of 'one teaspoon' of yeast and the specific gravity of liquid is that you'll get about 3-5 days of the smallest amount of CO2 before the mixture has attenuated, or completely stalled. The problem with the gravity is that it's too high and can present attenuation problems for the yeast. Most strains really struggle in liquids over 10% unless aerated periodically. One litre is also WAY too small a batch size. Yeast starters for batches of beer at 1/2 gallon barely add a scent to a closet, let alone add any CO2 benefit to plants.
If you want a system that works, and mind you this will work for a small closet grow and that's all, you need to increase the batch size and change the ratio of sugar to water. Only one pack of yeast is necessary as when yeast go through the phases of respiration, fermentation and sedimentation, your cell count increases 4 fold. A Brewery will recycle yeast and for this amateur-hour project, you can too. Except you're not concerned about fusel alcohols, phenolics and ester production. That means you can use one pack of yeast for the rest of your life.
One Gallon of water
1.4 lbs of sugar
1 pack of Safale S05 dry ale yeast (only 2 grams are needed out of the 11 gram pack)
This 1.065 mixture should ferment for about 1 week giving you a constant flow of CO2. Ideally, you should really double the batch size (and the ingredients) to get any kind of decent CO2 production
. Ferment this in a 3 gallon pale with the lid off even. You also need to make sure that you aerate the mixture at some point before fermentation has started as yeast need food (sugar in this case) and O2 to thrive. An airlock is not needed yet won't hurt as they are only useful when sanitation is a concern. At the end of the week, the yeast will have flocculated to the bottom of your container. Mix up a new mixture of sugar and water, dump out your fermented batch of prison wine, but make sure to leave at least half of the beige sludge in the container as that yeast will ferment your next round.
The concern I have is that is this really worth the 25 Lbs of sugar during flower that's needed to add any measurable amount of CO2? I'd say save the money and add an intake fan.