5 gallon jug co2 for longer time? - The Planted Tank Forum
 
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post #1 of 10 (permalink) Old 02-25-2010, 12:39 AM Thread Starter
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5 gallon jug co2 for longer time?

TLDR: Is there a way to use a 5 gallon jug for CO2 production and have it last longer than a 2 liter? I read somewhere that someone said they got 4-6 months out of theirs, but the brew store guy seems to think that this'll be spent up in a week.

I'm unemployed, so can't afford the 3-400$ for CO2. I've had this 55 gallon tank with lights and a CO2 ladder diffuser for a couple years, the tanks been untrimmed, and it was just a mat of plants and snails for several years.

Well, I ripped everything out, and replanted. I'm using four of those quad pin bulbs that are 55 or 65 watts each, so I have ~4 wpg, so I know I need CO2.

I was pumping the CO2 from the 2 liter into a small in-tank filter that was basically acting like a powerhead without my HOB's going. My homemade drop checker was reading yellow.. The filter design makes me think that it will eat baby cherry shrimp, so I've ripped it out. I'm now using my HOB filters and have one powerhead. Due to design of powerhead, I'm not injecting CO2 into its intake, I tried using the aerator inlet on the powerhead, and my drop checker is back in the blue. I've put back in my hagen co2 ladder, and I'm still in the blue, so I figure I need more co2.

I've read about the jello method, but for 5 gallons, it seems a little cost prohibitive. I thought that yeast didn't reproduce without the presence of oxygen, so had hoped that I could just add a small amount of yeast, and varying the amounts would regulate the quantity of CO2. The brew store guy seems to think that yeast reproduces regardless if there's oxygen or not, and that there isn't a way to regulate growth.

So far the only idea I have is to add a small amount of sugar to the 5 gallon, and then progressively add more later. I could do this, but I'd really like to 'set it and forget it' for a while.

Do I have any hope here? Or am I stuck with just doing a boatload of 2 liters hooked up in series and swapping those out?
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post #2 of 10 (permalink) Old 02-25-2010, 02:58 AM
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Why not start by running less light?
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post #3 of 10 (permalink) Old 02-25-2010, 04:17 AM
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Here's an experiment:

Prepare one two liter bottle with a recipe that produces a certain amount of CO2 for a week.

Prepare another two liter bottle the same as the first, but with 1/2 the amount of yeast.

Yeast cells can double in just a few hours. So theoretically, the second bottle should lag only a few hours behind the first. And in the long run, both should produce the same amount of CO2, and for about the same time.

But it does not. The second bottle produces about 1/2 the CO2, for about 2x the time. Why?

Yeast needs nutrients just like plants do. There's hardly any nutrients in sugar, only empty calories as mom used to say.

The only real nutrients in the bottle were added with the yeast itself. Once those nutrients are gone, they are not available again until old yeast cells die and release them. The yeast population reaches a fixed plateau.

Now when making wine or beer, there's a lot more stuff in there than sugar, and lots of nutrients to go around. Brewers sometimes add "yeast nutrient" too, just to make sure that nutrients do not become a limiting factor.

So yes, I suppose you could use a 5g jug to produce CO2 at a fairly constant rate for months at a time.

But figuring out the right recipe might be difficult.

And there might be other factors too. For example, another less-desirable bacteria might manage to muscle in on your malnourished yeast...
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post #4 of 10 (permalink) Old 02-25-2010, 08:21 PM Thread Starter
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Hmmm...

I added yeast nutrients, and quite a bit of baking soda. After a few hours the champagne yeast wasn't doing anything, so I seeded it with a 2 liter I had going, and added more bakers yeast. The next day it has a fairly slow bubble count. Maybe 0.5 or 1 bubble per second. I was expecting it to explode.

Did some math. 5 pounds of sugar at 72F would equate to about 30 gallons of Co2. It looks like the bubbles are 1/4", so if I do some more math...

It looks like if the bubbles are 1/4" at 1 bubble per second, that 5 pounds of sugar should last about 1.5 years. Who knows about the fudge factor however. So maybe it is reasonable to expect 6 months out of this...
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post #5 of 10 (permalink) Old 02-25-2010, 09:45 PM
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Some issues that will likely arise:

How do you intend to dissolve over 2 kilograms of sugar into 19 L of water? That's a lot of solute to dissolve.

In addition, the bubble rate that you take from the beginning of the logarithmic growth phase is not necessarily representative of what will occur (say) a few days down the road when the yeast has started to take off. In addition, waste byproducts of yeast metabolism may accumulate to toxic levels, killing off the yeast.

I find it difficult to believe DIY CO2 mixes can last 6 months; anything more than 1 month, I already find hard to believe.

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post #6 of 10 (permalink) Old 02-26-2010, 03:03 AM
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Quote:
Originally Posted by Darkblade48 View Post
How do you intend to dissolve over 2 kilograms of sugar into 19 L of water? That's a lot of solute to dissolve.
Is there a reason it has to be dissolved?

I used to put the baking soda in first, then pour in the sugar, and add water to about 2/3rds full. I'd prime the yeast in a little warm water for 15 minutes or so, then dump it in.

The idea behind it was that the sugar would slowly dissolve into the water on its own as the yeast used it up. And that the baking soda would slowly diffuse out from under the sugar layer, gradually working to lower the pH as the fermentation products worked to raise it; instead of being fully dissolved right up front and initially raising the pH to a level not optimal for the yeast.

Of course, it also had the appeal of being easier.

I can't say for sure if it was better or worse than dissolving everything up front, but it did work.

Quote:
Originally Posted by Darkblade48 View Post
In addition, waste byproducts of yeast metabolism may accumulate to toxic levels, killing off the yeast.
If a recipe on a small scale allows the yeast to consume all of the sugar before waste kills it off, then scaling up the water and sugar equally will result in more wastes, but proportionally diluted by more water. It cancels out, ending up at the same toxin concentration as the smaller batch when all the sugar is consumed.
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post #7 of 10 (permalink) Old 02-26-2010, 03:32 AM
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It should last longer given there is a small amount of yeast. Yeast does reproduce quickly if in an oxygenated environment. In an environment with very little oxygen, such as an air tight container full of sugar water, they will stop reproducing and pull the sugar apart to get oxygen; the byproducts being alcohol and CO2 gas.

There are about 18 liters in 5 gallons. so if you put lets say 16 or 17 liters of water and the same number of cups of sugar and sealed it up tight (you can get a set up like this from a brew shop, or just find a tight fitting lid) Then add about 1/4 tsp of yeast it might last 6 months or so.

From what I know the yeast will stop reproducing and start making CO2 once they are out of O2. Then the die or go dormant once the alcohol reaches a certain level (varies depending on type). So with little air in the bucket and a small amount of yeast it should take a while to reach the critical alcohol level.
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post #8 of 10 (permalink) Old 02-28-2010, 10:01 PM Thread Starter
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Update, 4 days later the CO2 rate is still consistent. I probably OD'd it on baking soda. The KH is probably ridiculously high. So all is looking well for it to be a good long sustained CO2 production, unless something else gets out of wack.
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post #9 of 10 (permalink) Old 03-24-2010, 01:38 PM
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dont forget bottle pressure which is why most people prefer 2 liter bottles i was gonna try a 3 liter and canned the idea early because of this but you may wanna try 3 liter bottles and see if you get an extra week or 2 out the mixture im still pondering the idea of the 3 liter but i have my 2 liter mixture exact right now....last me almost a month! at 1bps
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post #10 of 10 (permalink) Old 03-24-2010, 06:49 PM Thread Starter
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Bottle pressure is a good point. I got scared of breaking the container before it built up enough pressure to power a ceramic diffuser. The container was bulging and not sitting flat anymore.

Champagne yeast was dead from the package. I think the baking soda was a bad idea also. Was still cranking out CO2 a month later, but I replaced the solution anyways, it was going pretty slow. Replaced it, and now I get 1.2 bps into my powerhead and my drop checker is yellow in my 55g. I'm recording the BPM several times a day, and will have a better idea later of what works and what doesn't. I wasn't recording my data on my first batch and didn't have a bubble counter yet.
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