Reusing CO2 from FV

[scott isham]

When I transfer beer from the Fermenter to the serving tank I use CO2 and don't use a pump. When the fermenter is empty I have a tank full of CO2 at 15psi. It seems like such as waste just to vent that much CO2 to the atmosphere. I was wondering if I could at least reuse some of the CO2 to top off the head pressure of another fermenter that's going to be transfered soon. I don't think anything can survive in CO2, so I don't think I would be introducing any bugs or anything. Maybe a few flakes of dried up krausen might get through, but I could use a filter of some sort to catch those. Is this a good idea or am I missing something?

[NYSBrewer]

If, by chance, there was any oxygen in your serving tank, that would end up in your fermenter after the rack was compleat. Pushing that onto another beer may be enough to oxidize it, that is my only concern, and why I dont reuse. I would'nt mind hearing some other opinions....

[WitsEnd]

If you're using CO2 to push from the FV to the serving vessel, how would oxygen from the serving vessel get into the FV?

You're right, there's a great deal of potential energy left in a full FV at 15 PSI.

I would think you could use this to at least partially push the next FV into a serving tank until the head pressure drops to the point that you're not getting the flow that you need.

Another option might be to use it for purging a recieving tank. Instead of venting to atomosphere, sent it through a serving vessel before venting, reducing the amount of oxygen in the tank.

[jwalts]

If your water doesn't have enough alkalinity (yeah right), you may be able to bubble the leftover CO2 through your next batch of brewing water to help dissolve calcium carbonate. I have no idea how much CO2 or time that would take, though.

Joe

[NYSBrewer]

When racking from an FV to a serving tank, there should be a hose from the top pf the serving tank, connected to the side-arm if the FV to equalize pressure. As the beer moves into the serving tank the gas that is in the tank gets displaced by the beer and ends up back in the FV. If your serving tank was not compleatly purged of all oxygen, it will end ub in the FV when it is empty. It may not be enough to oxidize a beer, or if you are certain that the serving tank is compleatly purged with co2, then there would be no oxygen.

[South County]

Final CO2 purge/fill on keg cleaning runs? Obviously the pressure will diminish as you fill the kegs but I would think you could offset some of the CO2 needed. By using the gas to purge smaller containers I would think you would have less O2 pickup.

[GlacierBrewing]

When I'm filtering, I pressurize both FV and BBV to about 13psi and equalize them. When I'm done with the filter, my BBV is now full of filtered beer and pressurized for carbonating. I then distribute the CO2 in the FV to any other tank that may need it (BBVs for carbonating, BBVs for racking, FVs for next filter, etc). Follow quality brewhouse/cellar sanitation practices AND make certain your gas transfer hose is sanied! I've been doing this for quite a while now with no problems (knock on stainless!).
Dave

[kramling]

Are you guys purging the serving vessel/BBT of Oxygen prior to transfer from FV? What is the likelihood of oxidation in a finished product from not doing this?

[NYSBrewer]

Yes, purge, purge, purge!!!

[GlacierBrewing]

Yes, always purge the tank. Why give your new beer any more unnecessary contact with the atmospheric gas mix? I worked at a micro where the cellar guy was of the opinion that all he needed was a "blanket" of CO2 on the bottom of the tank and as the beer was CAREFULLY and CALMLY introduced into said tank, the column of liquid, topped by CO2 would push out all the ambient air. For what it's worth......

Prost!
Dave

[WitsEnd]

When racking from an FV to a serving tank, there should be a hose from the top pf the serving tank, connected to the side-arm if the FV to equalize pressure.
The OP stated that he moved the beer with pressure and no pump. I don't think this would be possible with an equalizing hose.

[Kushal]

You can push the co2 through an inline filter if you are worried about contamination. And if you are worried about air in the tank, let it sit over night and then move the co2 from the bottom, as it is heavier than air.

[NYSBrewer]

Right, Witsend, my bad.....

[jwalts]

Hey Kushal, I'm pretty sure diffusion trumps gravity in terms of gas mixing. The CO2 blanket works to your advantage (though not completely) when purging a tank from the bottom, but I think the CO2 and air would be pretty evenly mixed after an overnight rest.

[gitchegumee]

Purging is about the only thing you can do with fermentation gas. It cannot be used to carbonate as it must be scrubbed clean first or it will give headaches. And I'm with jwalts on diffusion trumping gravity. Leaving the two gases together overnight will just cause them to mix more--regardless of density. Fill your tank with water and push with CO2 for an effective purge.

[Guestimate]

Sometimes I think the movement of gas (insert bean joke here) performs better in our minds than in reality. Gas diffusions works very well in cellular microbiology, but in large cylinders other factors can come into play. I can remember rolling cylinders of a helium/argon mix around the shop. This was, of course, until OSHA decided that a bunch of idiots rolling highly pressurized cylinders around an autoshop was not a good idea. I also know of several SCUBA divers that to this day will roll cylinders of Nitrox or Heliox before they dive with them. As it turns out, giving both gravity and diffusion the middle finger, poorly mixed gas will stratify in the tanks and properly mixed gas will remain homogeneous indefinitely.
To get back to the original question, to properly recycle CO2 requires a lot of expensive equipment. I received a quote from Witteman years ago for several hundred thousand dollars. If you are hoping to save CO2, start transferring with a pump and use a balance line.
Also, many things can survive in a CO2 environment. Lactobacillus, Pediococcus, Wild yeast, Al Gore, etc.


Kevin

[scott isham]

Saving money or trying to reuse every bit of CO2 out of my fermenter was never my intention. I only thought of this after finishing a transfer and noticing the fermenter next to the one that I had just emptied needed the head presure topped off a bit. As I blew off the empty tank, I thought "why not use some of this CO2 to top off that one". I guess if some nasties can indeed survive in CO2 and get carried over, I'm not going to do it.

[beerking1]

Also, many things can survive in a CO2 environment. Lactobacillus, Pediococcus, Wild yeast, Al Gore, etc.
Kevin

Now THAT'S funny!

[gitchegumee]

Guesstimate, with all due respect to your experience, have you ever definitively checked this stratification "myth"? I'm an active scuba diver as well as a welder and have never heard of stratification in tanks of any kind of gas mix (poorly or well-mixed). And it doesn't seem to make physical sense--entropy will always push towards homogeneity. Especially with light, pressurized gases. And if Nitrox were to somehow separate into its components, why wouldn't the air around us that's made of the same components?

[Guestimate]

Phillip, my experience with this myth is as follows: My PADI instructor actually told us to roll our Nitrox tanks. Granted this was many years ago and his instruction was the result of his experience with a poorly mixed tank. This guy also forced water down his wind pipe and then put his regulator in his mouth to prove to us that we can cough, vomit, what ever, though our primary. My rolling of the argon/helium mix cylinders was per the recommendation of an older mechanic in the shop who had also had experience with a poorly mixed tank. Keep in mind, I also saw this crazy S.O.B. seat a tubeless truck tire on a rim by spraying ether on the bead and throwing a match at it. In both of these situations these guys actually believed the mixed gas would separate in the tanks. They were both misinformed, but speaking from actual experience with poorly mixed tanks. Homogeneously mixed gas will not separate into it’s components. I am going to repeat that one. Homogeneously mixed gas will not separate into it’s components. However, poorly mixed gas will stratify in storage tanks. These sites list equipment designed to keep poorly mixed gas from stratifying in cylinders:

http://www.megs.ca/auxiliary_equipment/gas-cylinder-blankets-2015.htm
http://www.labjupiter.com/dp/cat/84490/84533/iinfo.cfm?LCl=8186&TVTID=0&TItemNo=0&ItemNo=82860&q=1
http://news.thomasnet.com/fullstory/28475

I believe that individuals purchasing this equipment would be better off purchasing properly mixed gas to begin with. In all reality though, who gives a SH@# about my experience. Lets all conduct our own mythbuster experiment. Next time you transfer beer out of a fermenter, after you have finished your transfer, seal off the empty fermenter and drop the pressure to 5 psi. Then pressurize the empty fermenter to 10 psi from the top with compressed air. Let it sit over night and then release some gas from the bottom of the tank and check it’s CO2 content. Then release some gas from the top of tank and check it’s CO2. I have never conducted this experiment and I am very interested in the results.

Kevin

[gitchegumee]

Right. That ether trick is fairly common and a real time-saver! Kinda scary the first time you witness. I checked some other sources that claimed stratification too. They were not from modern mixed Nitrox that is pushed through a molecular sieve, but rather from blending methods (read: separate tanks of pure gases) used in the past. I'm still highly doubtful about the necessity of these tank rollers, but I guess others aren't. Regarding your experiment, I think your test protocol is spot-on. I can borrow an O2 meter from local dive shop. I also have a nitrogen generator. Besides just CO2 mixing with air, I'd also like to try Nitrogen and air. Being so close in atomic weight, it would supposedly diffuse even faster.
On another point, I use the nitrogen generator to push beer from BBTs to kegs & our canning machine. Although introducing nitrogen at 14 psi to a cold, carbonated tank would theoretically foam the beer (partial pressure of CO2 is reduced as the fraction of N2 is increased), foaming does NOT happen. My beer is still fully carbonated 8 hours after initial N2 is added. I guess that the slow introduction of N2 does actually stratify inside the tank. This would "blanket" the beer with the initial headspace of CO2. That's my theory anyway. As long as it works! I've also heard from some German micro brewers that they use compressed air to push their beer to the bar, but I'm not sure whether they might be using carbon steel tanks with a plastic liner--carbonated beer inside the liner, compressed air outside. Cheers!

[Moonlight]

I would venture that the easiest way to understand the stratification is like a bartender pouring a mixed drink with the alcohol on top (alcohol is lighter than water). Customer is initially wowed by how strong it tastes at the top, but it mixes in before long, especially with some turbulence. Still, the alcohol never separates on its own.