Under anaerobic conditions, yeast (Saccharomyces cerevisiae) harvest oxygen from glucose yielding ethyl alcohol, and CO2.. They actually evolve small quantities other other things such as ethylene, which is a plant hormone associated with ripening..
Alot of ppl already know you can produce CO2 with yeast, and sugar, but alot of the instructions and recipes I've seen are unreliable.. I'll get to a good lazy man recipe, but I gotta start by saying that its a shame if thats what you choose.. The best thing to do is seek out a forum on brewing, wine-making, or distilling and master a symbiotic hobby to this one..
Anyways, the numbers.. There are a number of aspects to look at regarding numbers.. Yeast specific numbers, sugar specific numbers, alcohol specific numbers, even exhaust rate, gas law and molar calculations..
Baker's yeast can tolerate up to 14% abv before succumbing to death by their own waste.. Other specialty yeasts can survive higher levels up to 18-19%.. All yeast function best when they aren't pushed to their limits, but each have their pros/cons for various fermentations..
Yeast can only handle sugar concentrations ~30-35% by mass.. Beyond this their cell walls get trashed..
Yeast can process sugar in two different modes.. Fermentation producing alchohol is the anaerobic mode..
C6H12O6 -> 2CO2 + 2C2H5OH + heat
For fastest/cleanest fermentation, sugar should be inverted, but I don't want to get into that now.. Its on google..
There is also an aerobic mode that yields no alcohol, but 3x as much CO2 and baby yeast..
C6H12O6 + 6O2 -> 6CO2 + 6H2O + more heat
Notice the fact that baby yeast aren't in that eq'n.. That brings up a good point.. YEAST DO NOT EAT SUGAR!!! Its an energy source for other chemical reactions more like breathing.. And yeast need to eat too, in reproductive mode they need alot of actual food.. Thats why I'll be stressing food sources when I get to recipes..
So those eq'ns bring us to some mole math.. A mole is like a dozen, except its waay bigger, and isn't an arbitrary number 1mole (602000000000000000000000 of anything) of protons weighs 1g.. This means that the mass of a mole of atoms weighs its atomic number in grams..
CO2 has a molar mass of 44g, glucose [C6H12O6] has a molar mass of 180g.. From the eq'ns we see that the ratios of CO2 to glucose are 2:1 and 6:1 respectively, so by mass it works out that the CO2 yield under anaerobic conditions is about 50% initial sugar mass, and about 150% initial sugar mass in reproductive mode..
Another thing about moles is that we can use them to estimate CO2 ppm..
A mole of a gas like CO2 will occupy 22.4L (~0.8cuft) at standard temperature/pressure.. 1mole of CO2 in 22.4L at STP would be 1000000ppm.. Our ideal target is about 1500ppm, which 667x diluted.. So 44g of CO2 produces about 15000L (530cuft) of ideal plant air, but stationary the CO2 will pool at the bottom.. Knowing how many cfm your grow room cycles, and being able to estimate the CO2 production rate its possible to scale towards a roughly correct stable concentration.. I can help you with this math if you ask..
Steady CO2 output from a single fermentation batch is impossible (not as impossible under reproductive conditions since very little alcohol is evolved).. If you want to keep controlled levels you'd need to get really good at making yeast happy, AND use multiple batches stagger started and always cycling.. But really if you care that much about the CO2 stability you should spend money on a bottle/burner and a meter..
I know I said its a shame to not brew up something tasty, but to address the mechanics thats what I'm going to post.. This can be scaled to need, but scaling a fermentation extremely may make it ferment a bit differently..
I'm going to work with Litres since there is only one kind.. Sorry Americans..
Dependable Sugar Wash 10L
For this measurements don't need to be precise, I'm leaving wiggle room..
For fastest results use dechlorinated water.. If your water is chlorinated with chlorine then that is as simple as letting it sit in the sun for a while.. If its chlorinated with chloramine, then its more persistent.. Vitamin C helps break it up I believe, I forget what else is involved.. I don't have to deal with that.. You can call your water supplier to find out if you do.. Ppl with aquariums need to deal with it so answers are easy to get..
-If yeast is in fridge/freezer, get some out now to warm.. The more the better, but its not critical for this wash.. I might use 3 little packs, or 1-2oz of bulk yeast for this if I'm not making a yeast starter batch..
-Heat 2-3L of water hot enough to dissolve sugar easily..
-Dissolve ~1.75kg (4lbs) sugar in that water..
-Squirt in a few tsp of lemon juice.. (Acidic conditions [high 4's] help to keep bacteria at bay, and also help invert sugar for yeast)
-Mix in a food source for them.. A can of tomato paste is great, potato water, cereal, fruit, concentrated juice and many other things are also good.. A crushed multivitamin is pure gold.. As long as you give them something they're happy..
-Optionally put in a half tsp of high N fertilizer.. Ideally DAP (diammonium phosphate).. this energizes yeast and helps speed stuff up.. Brew stores sell some sweet yeast energizer/nutrient blends
-Top it up to 10L with cold water
Make sure its within 75-85°F Yeast can survive warmer, but warmer water holds less O2.. Aerate the hell out of it! I'm not kidding we want O2 in there initially to the yeast can build their colony.. When they're done the population will be about 10-20million cells/mL! This is why we need food.. Yeast contain tons of things that aren't in sugar..
-Add yeast and give it a little stir.. Cover it up and keep it at whatever temperature your grow is.. In 2-12 hours it should be sounding like a glass of ice that just had soda poured on it, and should ferment to about 10.5%abv in 4-5 days..
Over its active period that batch will evolve about 2lbs (~20moles) of CO2, which would mix up to 300000L (~11000cuft) of ideal 1500ppm plant air..
From here its about considering your grow-room volume, exhaust rate, and exhaust position.. Exhaust on cieling is FAR superior to a low exhaust for CO2 containment..
It should be pretty evident though that this won't add up to much in a 2000cuft room with 560cfm exhaust, but for a contained stealth grow it could help alot.. Personally I'm under the anecdotal belief that the ethylene evolved helps my buds ripen a bit quicker..
Theres so much more that could be said.. I've been brewing and distilling for many years, and I have alot of math/science under my belt, so I have alot of experience an recipes to share.. I mainly make rums and sour mashes personally because I hate fermenting something, and not throwing it in my still a few times.. If I get a couple ppl to build themselves a still, I'll be happy with the results of this thread..
i have been searching and searching the web for a thread like this, i just ordered seeds and is about to arrive. And i have not yet done my set up, i was planning of having a 99% sealed stealth grow box its about 1.5' long x 1.5' height x 7" wide and was thinking of puting an co2 tank but way out of my price range! I was wondering if i could actually pull it off with a co2 gen (yeast and sugar) and roughly howmuch co2 will i be able to generate with it. I will vent only at lights off or could i not vent at all? Just when i open the box? Can i be able to make the gen with a smaller bottle or should 2L be the minimum? This will be my 1st grow and as i saw your thread i immediately joined the forum