DIY CO2 going impotent

[aquazen]

I've attempted construction of DIY CO2 injectors for the past 2-3 weeks. I've read several faqs on it, and most faqs stated that with 1/4 tsp of yeast and 2 cups of sugar in a 2 liter bottle should last about 1-2 weeks. The most I've gotten is 4 days. Does anyone else have this problem? I am certain that there are no leaks around the seal. Maybe the faqs are wrong and it doesn't last longer than a week?

Like most people who do DIY, the reason for doing this is mostly monetary. Any help/suggestions are welcome. Otherwise, I may have to forego plants that require CO2 injection and stick with the easy to grow ones...something that I do not find desirable (since I am planning on getting some Rotala and Riccia).

 

[Toirtis]

Is your yeast good-quality and fresh? What sort of water are you using in your mix?

 

[shawmutt]

I use 2 tsp each of yeast and baking soda, along with 2 cups of sugar, in 6 cups of water. By staggering two bottles, one gets changed every 2 weeks. I've experienced some slow down from time to time, but it goes pretty strong. Check out the site in my sig for my setup.

 

[marcus russo]

Another problem is heat. If the yeast is to warm or stored in a warm place it will not work as efffectively

 

[shawmutt]

If the yeast is to warm or stored in a warm place it will not work as efffectively

Yeah, I keep mine in the fridge until I'm ready to use it.

 

[malkore]

It's also November...yeast likes to do its thing between 70-80 degrees. Lower than 70 and you'll see reduced CO2 output.
If there are large temp swings between day and night, you're shocking the yeast and it's dying.

Personally, I think 2cups in a 2liter bottle is too much sugar. I don't use that much in a 1gallon bottle, and I get output for 4 weeks.

 

[aquazen]

Temp and recipe

The house is kept at 72-75 F. I mix 2 cups with 1/2 tsp yeast in a 2 L bottle. The cap is pretty tight, so I doubt there's any leakage.

So from what I'm seeing here, I should maybe cut back to 1 cup of sugar and 1/4 tsp yeast? This should last me about 2 weeks?

 

[shawmutt]

Personally, I think 2cups in a 2liter bottle is too much sugar.

everybody seems to use a different mixture. I use two of each because it was suggested when I started setting them up. Right now my life is really hectic (I actually had to drop a class today), and it's easier to stick with the way I've been doing it, but once the semester is over I hope to set up an experiment to find the most efficient way to get co2.

 

[malkore]

Basically using too much sugar will cause a waste of sugar. Yeast converts sugar to alcohol and CO2 is the by-product. When alcohol levels hit a certain point, yeast slows its consumption of sugar. Eventually the alcohol levels kill the yeast colony.

I used to homebrew mead, and my experience has shown that normal bread yeast max's out at 15% alcohol...at that point it stops. I use bread yeast because it's not designed for brewing, so it's a slower, steadier process.
Now, if you were using a high alcohol tolerant yeast, like champagne yeast, you could use more sugar in the mixture. However you're going to get a much higher CO2 out put initially, and then it will taper off and you'll get a couple weeks of low CO2 production.

I'd say you should get 3 weeks of CO2 out of a 2liter with 1 cup of sugar. Definitely don't need more than 1/4 teaspoon of yeast. Yeast will reproduce in the first 24-36 hours to a colony of appropriate size, so using a lot of yeast doesn't help much.

 

[aquazen]

New batch

Thanks to everyone with their insight. I whipped up a new batch this morning around 10 am. I used 1 cup sugar and 1/4 tsp yeast in a 2L bottle. It's been a few hours, and I can see the yeast working within the bottle. The tube is still full of water up to the surface of the tank, so it may take till tomorrow morning before it starts bubbling.

Here's keeping my fingers crossed. I'm praying for 2 weeks. It's been quite a chore switching it out every 4 days or so.

 

[Guest]

Just to add to some already great ideas. Whats the water temp when you add the yeast? Maybe it's to warm and it's killing off some of the yeast.

I got 3 weeks out of 2 cups sugar, 2 cups water and a dash of yeast. I'd boil the water and add it piping hot into the two liter with the sugar to kill and potential bacteria that might kill the yeast and fully desolve the sugar. Let stand approx. 24 hrs to cool to room temp. Then I would take approx. 1/4 cup water between 100-104 degrees, add the yeast with a dash of sugar to start the fermintation process. 30 minutes later I'd add the yeast mixture to the room temp. sugar mix. I possibly could have pushed the mixture close to 4 weeks, but I'd swap out at three to keep PH more stable. HTH