[BrewBama]

An article on saving CO2 from the latest addition of Zymurgy popped up so I read it. It was interesting but it omitted one pretty obvious way that I save on CO2: I use the CO2 produced by fermentation to push sanitizer out of the receiving keg thereby purging the keg. They mention using bottled CO2 to do this but not CO2 produced by fermentation.

[Richard]

Yes,  I was very surprised that the article omitted the use of fermentation gas to purge kegs. It has saved me a lot of CO2 and trouble since I started doing it. Now I only replace my 5 pound tank every 8 months or so and I need to make sure that the certification hasn't expired or they charge me for a re-test when take it in.

[ynotbrusum]

Definitely use fermentation generated CO2 to purge kegs - it must save me a tank of CO2 per year, I am willing to bet.  Combine that with fermenting under pressure and I end up using my tanked CO2 mainly for dispensing/racking finished beer only.

[dbeechum]

How are y'all capturing CO2? (Not that I can with my fermenters)

[BrewBama]

I’m not capturing it.

I fitted a gas post to my fermenter lid, attach a jumper line from the fermenter to the gas in post on a no foam sanitizer filled keg, and place a jumper from the liquid out post into a bucket. As fermentation proceeds the sanitizer is pushed from the keg into the bucket via the CO2 produced by fermentation.

For example yesterday I brewed. Today the bucket is full of sanitizer which now acts like an airlock. I saved the bottle CO2 it would have taken to push the sanitizer from the keg.





To keg the beer, I remove the jumpers, turn the keg upside down towards the gas in post, attach a gas quick disconnect to get the little bit of remaining sanitizer out until it sputters, then reattach the gas jumper from the fermenter to keg. I attach the jumper back onto the liquid out post to allow CO2 to escape purging the liquid line, then attach it to the fermenter spigot. Place the keg below the fermenter, open the fermenter spigot, and the beer displaces the CO2 in the keg and the CO2 displaces the beer in the fermenter. I save bottle CO2 by not using it to push beer from the fermenter to the keg.

[ynotbrusum]

Build up in fermenter - Fermzilla All-Rounder.
In post to spunding valve to keg with sanitizer to out post to bucket to catch sanitizer.  Switch over to second spunding valve on out post when sanitizer is empty in keg.  Keg becomes a big air lock and pressurized to 10 psi.  If a second keg needs purging, start over with that one - filling it first with sanitizer.  At some point the production of CO2 may not meet the demand for kegs needing sanitizing and pressurizing, but it will easily do 2-3 kegs in one fermentation cycle if you stay on top of the process.

Cheers!

[Richard]

I have separated the sanitizing and purging. First I sanitize a keg, then drain all the sanitizer I can. Once dry I leave it sealed up. During fermentation I connect a gas post on my fermenter to the liquid post on my keg, with the gas post going to a hose in a blowoff jar. I also have a tee in the line from the fermenter to keg, and I put a mylar balloon there, which is squeezed empty for starters. As fermentation proceeds the keg is purged and the balloon fills up. After fermentation and before I start a cold crash I disconnect the keg from the fermenter and use the balloon to provide CO2 to compensate for that required by the cold crash  (PV=NRT and the increased amount that dissolves at low temperature). The balloon has more than enough capacity and finishes with a fair amount of CO2 still in it. I use that CO2 to purge hoses to be used in the closed transfer, using the sanitizer purging method.

[fredthecat]

i understand this and its really cool, however aren't gaseous flavour compounds leaked off as well as CO2?

[ynotbrusum]

i understand this and its really cool, however aren't gaseous flavour compounds leaked off as well as CO2?

I would think that no more than occurs with a traditional airlock or blowoff tube arrangement. Of course, I have no means to objectively measure this.

[Bob357]

How are y'all capturing CO2? (Not that I can with my fermenters)

I pressure ferment and use a different technique for purging. I empty my kegs after sanitizing then purge by running a jumper between the fermenter gas post and the beer out post of the keg with a spunding valve on the gas out post of the keg, set to 12 psi, a day or 2 into fermentation. This not only does a decent job of purging but leaves the fermenter and keg at ~10 psi for a pressurized transfer. This cut my CO2 usage by more than 50%. I know the purge isn't as complete as when using a keg filled to the brim with sanitizer solution, but I don't want any liquid running through my spunding valve.

[Richard]

i understand this and its really cool, however aren't gaseous flavour compounds leaked off as well as CO2?

Yes, to some extent. When I empty the balloon after kegging the gas that comes out smells very nice. I don't think that having some flavor compounds left in the purged keg alters that taste of the beer that goes into it, if that is your concern.

[Andy Farke]

I haven't gotten into using fermentation-generated CO2 to purge kegs, although maybe I will someday.
My big CO2-conservation technique is to use the CO2 from an empty keg to purge sanitizer from a to-be-filled keg. It works super well for me...you just fill the new keg with sanitizer, hook a jumper from the gas port on the old keg to the new one, and hook up another line (into a bucket or tub) from the beverage-out on the new keg, and let 'er go! (this was featured in the Zymurgy gadget issue a year or two back...)