CO2 Purity and Why It's So Important

[Big Monk]

We have been getting questions about why people should be interested in CO2 purity and what damaging effects the O2 impurities within bottled CO2 can have on the finished beers of ALL brewers.

We have been working on a blog post for some time and we finally finalized and posted a write-up on it today:

http://www.lowoxygenbrewing.com/brewing-methods/carbon-dioxide-purity/

Let's discuss it!

 

[jalc6927]

Interesting

I used to deliver gases and understood the difference was much more than cost

 

[Big Monk]

Interesting

I used to deliver gases and understood the difference was much more than cost

It’s pretty crazy actually. Many people are probably just using 99.5% Industrial Grade CO2 and not realizing that it can have up to 50 ppm O2 impurity.

For the example we cited in our post, a 50 ppm impurity increases DO levels in just the force carbonated beer (without serving factored in) to 171 ppb, 21 ppb In excess of industry maximum.

Keep in mind that we assume 0 ppm in the keg to start (properly purged) and no O2 pickup from transferring, so we can see how things can get a little dicey quick.

 

[FunkedOut]

where does one source pure CO2?

 

[Smellyglove]

Sorry, wrong post.

 

[Big Monk]

where does one source pure CO2?

From fermentation! Seriously though, using Spunding to carbonate your beer is the purest form available.

Many suppliers can provide the varying grades of CO2. It would just be a matter of shopping around.

99.99% Instrument Grade would be one to strive for. I can’t tell you exactly where to get it because supplier sources vary but I would call around to your local suppliers first and see if they can help you out.

 

[Jayjay1976]

Ugh. 50 ppm o2? What level of o2 would this induce in your beer?

 

[Big Monk]

Ugh. 50 ppm o2? What level of o2 would this induce in your beer?

Let’s assume we want 2.5 volumes CO2:

DO Carbonated Beer = 1.42*50*2.5 = 178 ppb

The industry maximum for total packaging O2 is 150 ppb. This value represents the onset of accelerated staling, specifically the beginning of what George Fix termed “Stage B” oxidation. In the above example you exceed that immediately by simply force carbing the beer. That doesn’t even take into account the additional O2 introduced by serving, incomplete purging, O2 from transfer, etc.

This isn’t a scare tactic or us being doomsayers, just a look at something that might not have been on people’s radar. It also doubles as an advertisement for Spunding!

 

[FunkedOut]

I’ve been spunding for a few brews now.
First couple, I used the fermentation off-gassing to push sanitizer out of the serving keg.
I’ve gone back to brewing two at a time so that leaves me with no room for the serving keg in the ferm chamber.

Now, I’m using a bottle of CO2 to purge the serving keg as well as get me from 2.3 vol (spunding) to 2.5 vol (forced).
The O2 in the bottle might make everything else I’m doing on the cold side a waste of time.

 

[daveMN]

What about something like this inline after the regulator?
https://www.thomassci.com/Equipment/Gas-Management/_/OxygenMoisture-Traps1?q=Oxygen Filter
Doesn't look like it's sold as "food grade", but there may be something similar out there.

 

[Big Monk]

I’ve been spunding for a few brews now.
First couple, I used the fermentation off-gassing to push sanitizer out of the serving keg.
I’ve gone back to brewing two at a time so that leaves me with no room for the serving keg in the ferm chamber.

Now, I’m using a bottle of CO2 to purge the serving keg as well as get me from 2.3 vol (spunding) to 2.5 vol (forced).
The O2 in the bottle might make everything else I’m doing on the cold side a waste of time.

Spunding is really king on the cold side. Carbonation and oxygen exclusion in one step? A no brainer if it’s feasible for you.

 

[daveMN]

Spunding is really king on the cold side. Carbonation and oxygen exclusion in one step? A no brainer if it’s feasible for you.

What does your spunding process look like? I have tried 3 batches fermenting under pressure in corny kegs. The first two, the fermentations stalled and I couldn't get the yeast to get going again. The last one, I only spunded to 1.5 psi, while it fully attenuated, it was only to 1.5 psi.

 

[SanPancho]

Another issue is doing any sort of half batch in a corny. Trying to do those calcs to figure out when to spund makes my head hurt.

Although with a bigger chamber i could have serving kegs attached and at least have pure purged serving kegs, so that’s something.

 

[FunkedOut]

Ale: 2 days at lowest pressure I can get with my valve (~1.5psi). Then crank the valve up to 1 bar (~15psi).

Lager: 3 days at low pressure, then crank.

The last pair of lagers I made, they both reached FG on day 4. W34-70.

That’s what works for me.
I’ve read that you should cap/spund when the beer is 10% or 1* Plato away from FG.
I’m too busy and my fermentation’s happen too quickly for me to reliably catch them in this state. Even checking daily.

 

[Big Monk]

What does your spunding process look like? I have tried 3 batches fermenting under pressure in corny kegs. The first two, the fermentations stalled and I couldn't get the yeast to get going again. The last one, I only spunded to 1.5 psi, while it fully attenuated, it was only to 1.5 psi.

Most people at our forum aren’t fermenting in corny kegs. SS brewtech brewbuckets are very popular. I use a converted SS stockpot.

Essentially you track the progress of your FFT and when you get to within 4 gravity points or so of final gravity you transfer to the spunding keg. Once you get comfortable with how a certain yeast performs, most people don’t even use the valve anyway. You just transfer with the required extract in a closed fashion and seal the keg.

Beer finishes fermenting in the spunding vessel and then you can Serve from there, only hooking up bottle gas to serve.

 

[mredge73]

Yeast produce more than C02; this isn't as pure of a source as you suggest.

What grade should I be asking for?
https://www.praxairdirect.com/Speci...r/Pure-Gas-Specifications/Carbon-Dioxide.html

Most of the time the exchanges are Anaerobic grade (CD 4.0AN).
Is this what I should be using for force carbonation?

Based on your research what is the best way to purge a keg?

I ferment in corny kegs with a spunding valve set at 15psi. This is fine for fermentation, the yeast seem comfortable and always reach FG properly. But this is far from the 30psi needed to carbonate fully at fermentation temp. What are you doing differently to avoid having to force carbonate?

 

[FunkedOut]

If you ferment cold enough (lager strain) you can carbonate fully at 15psi.
I ferment lagers a bit warmer, and ales are way out.

We could always prime a keg for carbonation.

Another option is to time things right and set the spunding valve to 30psi (or appropriate pressure for temp) right at the end of fermentation.
My attenuations happen pretty quickly (2-4) days,
I work everyday,
I’m not wanting to pull a sample every night,
so that one is out for me.

 

[jcav]

Excellent article, thanks for posting. So as soon as you force carb with C02 you are putting a certain level of oxygen in your beer and the clock is ticking on oxidation. Great....

John

 

[Big Monk]

Excellent article, thanks for posting. So as soon as you force carb with C02 you are putting a certain level of oxygen in your beer and the clock is ticking on oxidation. Great....

John

Pretty much. It's purity dependant of course. If you can get a grade of CO2 with only a 10 ppm O2 impurity, you'd be in better shape. Typically though that;s not the case. I suspect the average brewer just uses industrial grade CO2, which has a much higher impurity of O2.

It's also carbonation dependant. We used 2.5 volumes for the examples but as you increase desired carbonation you increase O2.

It's a jungle out there...

 

[Big Monk]

Yeast produce more than C02; this isn't as pure of a source as you suggest.

True but in this case we only care about the O2 content because of the oxidation potential.

Most of the time the exchanges are Anaerobic grade (CD 4.0AN).
Is this what I should be using for force carbonation?

That's good stuff. Running the numbers:

DO2 = 1.42 * 10 * 2.5 = 35.5 DO for Force carbonation. I still recommend Spunding but you can't complain about those numbers.

Based on your research what is the best way to purge a keg?

We have a full write up coming soon on properly (full liquid purge) and closed transferring. Stay Tuned.

I ferment in corny kegs with a spunding valve set at 15psi. This is fine for fermentation, the yeast seem comfortable and always reach FG properly. But this is far from the 30psi needed to carbonate fully at fermentation temp. What are you doing differently to avoid having to force carbonate?

Set the valve higher.

 

[Brettomomyces]

How much of a difference is there between industrial and "food grade"? The hydro stores out here typically have food lot CO2 and are cheaper

 

[Big Monk]

How much of a difference is there between industrial and "food grade"? The hydro stores out here typically have food lot CO2 and are cheaper

It goes by purity:

99.5% = 50 ppm Oxygen impurity

99.9% = 30 ppm Oxygen impurity

99.99% = 10 ppm Oxygen impurity

99.999% = 2-5 ppm Oxygen impurity

Food grade does not necessarily mean higher purity. Beverage grade would be a good start.