Sanity check for CO2 harvesting

[fuzzybee]

In my new setup, I'm fermenting in 6 gallon Torpedo kegs in a 4CF fridge. Currently, I start my fermentations with a gas-out blowoff tube going into a pitcher of Star San, then I switch to a spunding valve after fermentation has started to die down.

I'd like to start excess harvesting CO2 during spunding to evacuate my serving keg. Since I can't easily fit another keg in the fridge, and definitely not 2, my thought is to drill a hole in the door and feed some EVA Barrier through it, with Duotight connections on either end. Then, all I have to do is move my blowoff tube to the door port, take the outside connector and put it into a gas in on a keg full of Star San, and take the beer out from that into a beer out on another keg which has the PRV pulled. If needed, I'll put a check valve between the door and the first outdoor keg.

I ferment in my garage, so I'll have a pretty good temperature difference between the fermentation and the outside kegs (especially for lagers). Will I run into issues with this?

 

[DuncB]

No need for hole the fridge seal should cope with 8mm eva. Both my fridges can cope with 2 at once.
Temp doesnt make that much difference as you are in an all gas situation.
Use blowoff inside fridge, then when purging connect up as you say.
Once keg purged go gas out ferment keg to liquid in and put spunding valve on gas. Build your pressure to correct one for temp and final vols. This might be 25 to 30 psi at ferment temp.
Once ferment and diastatic rest finished disconnect your serve keg.
Cold crash ferment.
Once you've had a few days clearing do closed transfer. Gas to gas first to equalise pressure, disconnect one gas end and then attach liquid to liquid brief pull of prv starts the siphon. Height difference helps this.
Then reconnect gas and the system balances as it transfers.
You shouldn't need supplementary gas for the transfer. It does take time I find about half hour.
If you have 8mm internal tube use that on the liquid line.

Don't forget purge your lines with CO2 pre transfer, liquid line purge it using gas in your serve keg.

After transfer you can use remaining ferment pressure in keg to start next keg purge.
Hope this makes sense.

 

[CascadesBrewer]

No need for hole the fridge seal should cope with 8mm eva. Both my fridges can cope with 2 at once.

hmmm...That is one reason I have not tried this much myself (except once with a beer fermented with Voss). I cannot fit a keg in my chest freezer along with my fermenter.

put it into a gas in on a keg full of Star San, and take the beer out from that into a beer out on another keg which has the PRV pulled

Note there is a thread with lots of math showing that just venting the CO2 from fermentation into a keg will purge the levels of oxygen down to extremely low levels without the need to fill a keg with StarSan or worry about a second holding keg for the solution. This is the process I used once, and it worked well.

 

[DuncB]

The thread did agree though that the purge of starsan would mean less oxygen to flush out.

 

[doug293cz]

hmmm...That is one reason I have not tried this much myself (except once with a beer fermented with Voss). I cannot fit a keg in my chest freezer along with my fermenter.



Note there is a thread with lots of math showing that just venting the CO2 from fermentation into a keg will purge the levels of oxygen down to extremely low levels without the need to fill a keg with StarSan or worry about a second holding keg for the solution. This is the process I used once, and it worked well.

Here it is: doug293cz's epic post on CO2 generation

Brew on

 

[DuncB]

@doug293cz
Certainly is an epic post, quite a few brewing myths put to bed in that one.

 

[doug293cz]

@doug293cz
Certainly is an epic post, quite a few brewing myths put to bed in that one.

I am quite proud of that post (put a lot of work into it) but what myths were slayed?

That analysis is a "worst case" analysis, since a more accurate analysis would require differential equations, with parameters that are specific to each system. People with measuring equipment accurate enough to test the results (very expensive) have shown that the results are much better than the worst case analysis predicted (this is expected.) Unfortunately, the report is behind a firewall.

Brew on

 

[DuncB]

@doug293cz
Myth Was thinking that the keg has to be full of liquid and purged to ensure minimal oxygen.
Your calculations showed this wasn't true.
Also peoples belief that diffusion can't occur against a gas flow gradient ( ie along a tube).

 

[Closet Fermenter]

Question. I have used fermentation gas to purge my receiving keg. The keg was cleaned and sanitized, but empty. Did a closed transfer to receiving keg; no problems. Now, if I want to naturally carbonate in the receiving keg, do you foresee any problems putting the sugar in the receiving keg which will be purged with fermentation gas.
I am reluctant due to the moisture coming through, the initial atmospheric oxygen level, and elevated temperature of the receiving keg. I am building a fermentation cooling device to cool my fermenter because I don’t have space for a chamber, but the receiving keg will be warm.
Any thoughts?

 

[doug293cz]

Question. I have used fermentation gas to purge my receiving keg. The keg was cleaned and sanitized, but empty. Did a closed transfer to receiving keg; no problems. Now, if I want to naturally carbonate in the receiving keg, do you foresee any problems putting the sugar in the receiving keg which will be purged with fermentation gas.
I am reluctant due to the moisture coming through, the initial atmospheric oxygen level, and elevated temperature of the receiving keg. I am building a fermentation cooling device to cool my fermenter because I don’t have space for a chamber, but the receiving keg will be warm.
Any thoughts?

I don't see a problem.

Brew on