Capturing CO2 from Keg

[trustyrusty]

Hi Guys

Just did a google search and found some old posts and nothing substantial. One I saw were using

ballons...

I am using corny keg as secondary fermenter and letting a lot of Co2 out and thought that is a real waste.

I was thinking of getting a corny lid with the gas or liquid out post and attaching to an empty keg.

The only thing I can think of is if the pressure equalizes or the pressure in the storage keg gets high it won't

transfer, I wonder if there is one way valve for this purpose? Or there is some contraption. If could re-use

the keg to maintain carbonation ie put it back when needed. Seems a simple idea but anyone tried this?


cheers

 

[Grott]

There is a fair amount of co2 in a finished keg. You could prepare your next keg to be filled by sanitising it then purge all the o2 out by having a tube to the bottom of the keg connect to a gas disconnect. All the co2 would then transfer.
Cheers

 

[mikec]

What you're capturing isn't pressurised and is also potentially contaminated.
I can't see this being worth the effort.
You could fill one keg with CO2 but that is not enough to do anything other than purge that one keg of air.
It's a couple of cents worth of gas.

Really big breweries do recapture some of their CO2 but it then goes through a lot of processing to sanitise it and repressurise it. It's millions of bucks of equipment but worth it due to the volumes they use.

 

[MHB]

Under the Reinheitsgebot, German brewers cant bring in any CO2 not made in the brewery, so they need to use their own - that has sort of driven the R&D.
At a HB scale it isn't worth it (mikec covered it) and even at a big commercial level few outside Germany bother.
Mark

 

[trustyrusty]

Thanks - you are probably right, the thing is that I have naturally carbonated a batch (in fact I have to keep purging it in the fridge still), so it seems a waste...
I was thinking that even if I kept a keg full that was under say 15 psi (under the pressure of the producing tank which I am keeping at 20 psi) I could at least have some CO 2 re-carbonate a keg later or it use for pouring pressure ...?

Interestingly if I had not let co2 out it reckon it could have got up to 200 psi, would that effect the beer?

Interesting about the German brewers...

 

[peteru]

Interestingly if I had not let co2 out it reckon it could have got up to 200 psi, would that effect the beer?

At 200 psi you could be looking at mechanical failures in the keg or fittings. That could range from a slow leak to an explosive decompression or even a rupture. Although, realistically, it should just result in the pressure release valve activating, assuming you have one.

 

[Yob]

I would not want to be in the same room as a keg with 200psi in it...

**** that..

And the beer would be undrinkable and saturated beyond comprehension

 

[trustyrusty]

Guys I did not say the Keg was 200 psi - If I had NOT let it out it would be 200 psi - ie letting out 10 psi for the last 20 days, and even longer.... IE quite a lot of CO2

 

[klangers]

The way it's done in big breweries:

• All fermenters are connected to a CO2 recovery circuit
• Since fermenters have a few kPa top pressure, the produced CO2 flows out of the fermenter into the recovery "gas bag" which is a big balloon
• When the balloon gets full, the CO2 compressors kick in and pressurise the gas
• The hot, high pressure gas is then cooled/condensed and stored (under pressure)
• This can then be used like "bought" CO2

It's certainly possible to do this on a home brew scale, but not at all sensible.

 

[Wolfman1]

You could get carbon credits from the government.
It would payback the investment in 4-500 years

 

[Lyrebird_Cycles]

The way it's done in big breweries:

• All fermenters are connected to a CO2 recovery circuit
• Since fermenters have a few kPa top pressure, the produced CO2 flows out of the fermenter into the recovery "gas bag" which is a big balloon
• When the balloon gets full, the CO2 compressors kick in and pressurise the gas
• The hot, high pressure gas is then cooled/condensed and stored (under pressure)
• This can then be used like "bought" CO2

It's certainly possible to do this on a home brew scale, but not at all sensible.

There are a couple of extra steps: the recovered gas is dessicated, scrubbed of ethanol and deodorised. I remember Alum being used in one of those steps, probably the dessication. We looked at doing this and the turnover point for decent return on capital was about 100 megalitres per annum beer produced.

 

[klangers]

There are a couple of extra steps: the recovered gas is dessicated, scrubbed of ethanol and deodorised. I remember Alum being used in one of those steps, probably the dessication. We looked at doing this and the turnover point for decent return on capital was about 100 megalitres per annum beer produced.

Indeed, there are numerous additional steps, depending on the level of engineering detail one wants to explore.

 

[mikec]

Your beer wouldn't have gotten to 200psi on its own.
But as others have said your PRV should blow before you get to explosion levels.

Trusty, to your original question and follow up.
Let's say you managed to fill a keg to equilibrium with the first keg, at 15psi.
You don't actually have that much gas. As soon as you tried to use it, pressure would drop and then it would be gone. i.e. you couldn't carb another keg with it, you probably couldn't even carb one bottle with it.

 

[RelaxedBrewer]

You don't actually have that much gas. As soon as you tried to use it, pressure would drop and then it would be gone. i.e. you couldn't carb another keg with it, you probably couldn't even carb one bottle with it.

Fermentation actually produces quite a lot of CO2. A 19L batch of 1050 OG beer, will produce ~375L of CO2. You can easily carb quite a lot of beer that amount of CO2.
To illustrate the point further, think about how little fermention is required to carbonate naturally in a bottle.

Still not worst the cost of setting it up though.

 

[dannymars]

Boags in Launceston harvest their CO2 for re-use. #Trivia

 

[dannymars]

This idea would be kind of useful for someone like me who has a lot of kegs. Keeping them all pre-pressurised would save /some/ gas...

Having a check valve, into an empty cornie, then to a release valve would keep all my kegs pre-purged for when I need to use them. Which would be fairly handy I guess. However the sanitary-ness may be an issue as well as the aroma etc. Maybe one of those sanitary air-filter things would suffice.

 

[mikec]

You've also got to remember that CO2 is not the only byproduct of fermentation.
I'm not sure you wanna be injecting that back into finished beer.

 

[mikec]

Fermentation actually produces quite a lot of CO2. A 19L batch of 1050 OG beer, will produce ~375L of CO2. You can easily carb quite a lot of beer that amount of CO2.
To illustrate the point further, think about how little fermention is required to carbonate naturally in a bottle.

Still not worst the cost of setting it up though.

Yeah but we are only talking about filling one keg to 15psi. Which is not much gas and will deplete quickly when you try to use it.