How much Co2 lost when pulling trub from conical.

[Gallagher1424]

I have a 7.9 gallon fastferment conical. If I were to make a small batch say some where around 4 gallons in this fermenter the Co2 should protect the beer from oxidation even though the headspace is large. Now when I pull trub out I will lose some Co2. Do I lose too much Co2 that the beer is no longer protected by the large headspace?

 

[mongoose33]

There's a myth out there that CO2 will "blanket" beer or wort or whatever. It's not true.

If you admit air into the fermenter, it'll include oxygen which will come in contact w/ the beer. You'll get some degree of oxidation.

One way around that I know is to add a very low pressure CO2 line to the port which would draw in the air. Something like 1-2 psi, no more. Thus you have "makeup" CO2 to counter the volume of the trub loss.

Another way is to capture the CO2 produced by fermentation in a double-vessel similar to this: https://www.norcalbrewingsolutions.com/store/CO2-Carbon-Dioxide-Harvester-Kit.html It allows you to capture CO2 and then feed it back during a crash where headspace contracts, but it could also work with a trub dump. You'd need larger jars for it to work, and the associated connectors.

*************

I think the myth of a CO2 blanket comes from when people have seen dry ice sublimate; the gas is cold, and what we see is water vapor condensing out of the air, and of course that all sinks. But the reason it sinks is because it's cold, and at equal temperature to the air, it's not going to do that. The CO2 will mix with the O2 and the Nitrogen in the air. No blanket.

 

[divrack]

Yea what he said. The headspace is irrelevant. However the amount of o2 from taking out the trub won't be large, but would not be with it in my opinion. Trub isn't a problem really. O2 for hoppy beer is. I leave it as is until I'm ready to transfer then use co2 as mentioned

 

[IslandLizard]

One way around that I know is to add a very low pressure CO2 line to the port which would draw in the air. Something like 1-2 psi, no more. Thus you have "makeup" CO2 to counter the volume of the trub loss.

+1 to what @mongoose33 said, true words of wisdom.

I'm pulling this one out, especially, to emphasize that although 1-2 psi of pressure is not much, it IS plenty. Much more, and your trub and beer will shoot out with quite some force. You could fill a plastic "bag" with CO2 and connect that to the port. As trub is drained, the underpressure will pull CO2 from the bag, deflating it.

Something like this: Cold Crash Guardian

Your beer is always "protected" by the amount of CO2 generated by the fermentation, but it always contains some residual air (O2) too, as that is what you started out with, a headspace full of air.

 

[ajdelange]

Let's look at some numbers. Four gal of wort is 15.14 L which at 10 °P contains about 1575 grams of extract. Assuming 60% of that ferments it is going to produce approximately 747 grams of CO2 which is 17 moles. At 22.4 L/mol that's about 380 liters of CO2 which is about 25 times the headspace. The CO2 evolved is heavier than air and thus displaces the air from the bottom up pushing it out the top 25 times over. Yes, given enough time air and CO2 will diffuse into one another but you don't have enough time. Your beer is not 'blanketed' with CO2 in the sense that there is a layer of CO2 with air above it but it is under a headspace containing very little air.

If you withdraw beer or trub and admit air you will certainly expose the beer to some air not because blanketing doesn't work but because the air coming in will introduce currents in the headspace gas thus allowing mixing.

Obviously the way to prevent this is to withdraw under positive CO2 pressure. You will want this for counter pressure transfer to kegs anyway. "Blowing down" trub isn't called blowing down because we expect it to trickle out of the triclover.

When I fill kegs they are precharged to 30 psig with CO2. The fermenter is under 20 psig. After everything is connected up the keg is bled down to just under 20 psig (through a needle valve) and when pressure is at 19 or so the beer valve is open and the keg fills without foaming.

Even with 20 psig in the fermenter the blow down is, at first, less than spectacular if you have a well compacted yeast cake.

 

[Gallagher1424]

Thank you guys, these were really helpful responses. [emoji4]

 

[mongoose33]

When I started doing some LODO stuff, I learned about spunding, or finishing fermentation in the keg similarly to bottle conditioning. To get about 2.5 volumes of CO2 in the beer, one should spund when there's about 5 points of gravity remaining before full attenuation.

Setting aside the question of how you do that--there are ways--if you work your way backwards you end up with some interesting results. If 5 points is equal to about 2.5 volumes of CO2, if you have a beer that starts at 1.065 and finishes at 1.015, the yeast consume 50 points. That's about equal to 25 volumes of CO2. You can use that excess CO2 to purge a keg, just by running a tube from the fermenter to a QD connected to the OUT post on the keg.

I seem to recall that purging a keg 25 times w/ CO2 was enough to essentially dilute/eliminate what O2 was in there. Can't find a reference for that offhand, but I was struck by how close that is to how many volumes of CO2 fermentation produces.

EDITED TO ADD: The above about the 5 points of gravity getting about 2.5 volumes is true; HOWEVER, I have to account for increased headspace in my Spike CF10 fermenter when i brew a 5-gallon batch. There is a headspace of about 6-7 gallons as opposed to the maybe 1.5 in a 5-gallon fermenter. That means I need to count on about 8 points of gravity to finish, though that as a guesstimate is only that. I can't get enough pressure in my conical to fully carbonate, so 8 points is close enough.

 

[ajdelange]

It's easy enough to figure out what happens when you purge a keg in the usual way. It starts with air at partial pressure 1 bar absolute. If you pressurize with CO2 to 2 bar gauge (3 bar absolute) you still have 1 bar partial pressure of air out of total pressure of 3 bar so the keg now contains 33.3% air and 66.7% CO2. Bleed that back down to 0 bar gauge (1 bar abs) and you have a keg with partial pressure of air of 0.333 bar and .667 bar CO2. Now pressurize that back to 2 bar gauge (3 bar total) and you will have partial pressure of air of 0.333 bar and of CO2 2.667 bar. That's 0.333/3 = 11.1% air so that if you bleed back to 1 bar you have air partial pressure 0.111 bar abs. Thus each time you do this you cut the partial pressure of air to 1/3 what it was in the previous cycel. If you do that 25 times the partial pressure of air will be (1/3)^25 = 1E-12 bar so I don't think one needs to go that far. Note that pressurized to 3 bar abs the keg contains essentially 3 volumes of CO2 (a little less for the first couple of cycles) relative to what it does at 1 bar abs and you are releasing essentially 2 during each bleed down. Note that all this is approximate as we are treating CO2 as an ideal gas here. Using 25 volumes of CO2 thus implies 12 cycles and results in a reduction factor of (1/3)^12 = 1.88e-06. Starting with 0.2 bar O2 we'd wind up with 4e-7 or 0.4 ppm. "Purging" a keg by pressurizing with CO2 and bleeding obviously isn't very effective. Filling with water (with a pinch of metabite) or steam (that's what I do - sterilizes at the same time) and pushing that out with CO2 will get you a better purge and save you a lot of CO2.

So how does this compare to what happens in a fermenter (isn't it strange that a brewing site's spell checker flags ferementer and fermentor as mispellings)? The CO2 is evolved gently, at first, at the surface of the wort. As it is heavier than air it stays there though eventually it will diffuse into the headspace air and the headspace air into it. There is no vigorous mixing as there is when you shoot CO2 into a keg. Even as air diffuses down into the CO2 'blanket' it is displaced upwards by more CO2 Thus it would seem that the rising CO2 'blanket' would push all the air upwards and out the vent at the top. But, of course, you won't get every molecule of air out this way. Will the end result headspace gas have less then 0.4 ppm O2? I rather think so but I have no data.

 

[Jag75]

I have a 7.9 gallon fastferment conical. If I were to make a small batch say some where around 4 gallons in this fermenter the Co2 should protect the beer from oxidation even though the headspace is large. Now when I pull trub out I will lose some Co2. Do I lose too much Co2 that the beer is no longer protected by the large headspace?

If its the

I have a 7.9 gallon fastferment conical. If I were to make a small batch say some where around 4 gallons in this fermenter the Co2 should protect the beer from oxidation even though the headspace is large. Now when I pull trub out I will lose some Co2. Do I lose too much Co2 that the beer is no longer protected by the large headspace?

I have the same fermenter . Never had an issue . The collection ball is pretty awesome because you rack without exposing the wort to oxygen. I leave my wort in for 3 weeks total . Always do a 5 gallon brew . Never issues with oxidation from head space because I never open the top. When I fill the keg I connect the hose on the bottom and run it into the keg . Really like the fast fermenter.

 

[IslandLizard]

without exposing the wort to oxygen

I leave my wort

One thing here, once you pitch yeast, your wort becomes... beer!

When I fill the keg I connect the hose on the bottom and run it into the keg

You should check out the LoDo forum and closed transfers.

Much better to fill your clean keg with Starsan (or drinking water) all the way to the top, dispense a pint, purge the pint of headspace 5-10x under 30 psi, and push the rest of the Starsan out with CO2. Then fill that now 100% pre-purged keg with beer from your fermenter, through the liquid out post (with a QD attached). You don't open the keg, leave the lid on.

There are a few variations on this theme, but they all have the same goal in mind, no oxygen exposure after fermentation! This is especially recommended with hoppy beers. Oxygen causes oxidation that dulls and even kills beers' hop flavor and aroma.

 

[mongoose33]

Just to throw you a few pics about what @IslandLizard is talking about:

1. pressure transfer from conical. CO2 pressure in, then using a jumper from conical to keg, and a spunding valve on the keg to maintain pressure so minimal foaming while transferring (it's partially carbed):

Purging a keg using CO2 produce from the conical; CO2 produced from fermentation goes into the OUT post on the keg, PRV is released to allow release of gas to the outside. The jumper for transferring beer using a closed transfer is in series there so it's being purged of O2 as well.

In this case I'm using CO2 from fermentation to purge the keg (into the keg using the OUT post), then running a line from the IN post to a blowoff jar so I can monitor fermentation:

 

[Jag75]

I'll have to check out the Lodo forum. That's a really nice set up mongoose!. The op and my style fermenter is not as pro style. It's just plastic and has no input for co2 pressurizing. Basically what I have to do is set my fermenter on my table. Take off the collection ball and attach the hose . After sanatizing my keg I fill it with co2. Then I can release some pressure then open the top just enough to slip the hose in from the fermenter and fill. Not sure how much o2 is left in the keg this way but it should be minimal amount. Once the keg is filled and hooked up to co2 to force carb and purge a few times wouldn't that flush out any amount of o2 that was let in by opening the top? Eventually I'd like to have a nice fermenter like the one you have. I just bought the grainfather and my wife would nut up on me if I got something like that right now. I appreciate everyone help and info to teach me better ways to produce better beer.

 

[mongoose33]

I'll have to check out the Lodo forum. That's a really nice set up mongoose!. The op and my style fermenter is not as pro style. It's just plastic and has no input for co2 pressurizing. Basically what I have to do is set my fermenter on my table. Take off the collection ball and attach the hose . After sanatizing my keg I fill it with co2. Then I can release some pressure then open the top just enough to slip the hose in from the fermenter and fill. Not sure how much o2 is left in the keg this way but it should be minimal amount. Once the keg is filled and hooked up to co2 to force carb and purge a few times wouldn't that flush out any amount of o2 that was let in by opening the top? Eventually I'd like to have a nice fermenter like the one you have. I just bought the grainfather and my wife would nut up on me if I got something like that right now. I appreciate everyone help and info to teach me better ways to produce better beer.

I'm going to respond specifically to what you said above, but before I do--I believe everyone can get to brewing excellent beer if they just keep doing things things better. Implement best practices as best you can, eliminate oxygen post-fermentation here, and here, and here if you can, control things better, measure things better, etc. etc.

My goal? Every time I brew, I try to do something better. I believe the small stuff matters, not necessarily individually, but taken as a whole. It's hard to do this kind of thing all at once especially in the beginning, but if every time you brew you do something better--control mash temps better, remove O2 from kegs better, oxygenate the wort better, make the starter better, control timing of hop additions better, etc. etc. etc--your beer WILL get better. And if you keep doing it, your beer will become exceptional. That's my belief, and my mantra.

So--there are things you can do better w/r/t kegging your beer. Here's one: you add CO2 to your keg, but you're not purging it effectively unless you do that more than 10 times, and even then there's O2 left in there. Purging is better than not purging, and as is the case with much of this, we're on a march toward better and better ways of doing things. That, IMO, is the secret to brewing great beer--the small stuff matters, when taken together as a whole.

*********

What you CAN do is this: fill your keg with Star-San solution. Add a gas line to the OUT post (yeah, the gas line on a black QD). Send some CO2 into the keg--the lid is off--and allow it to bubble up and create bubbles. Don't turn it on full blast unless you want a surge of Star-San erupting out of the keg opening. Don't ask how I know this.

What's in those bubbles? CO2, of course. Those CO2-filled bubbles will fill the headspace above the star-san. Let it bubble up under the lid, too, so the bubbles fill the area under the actual lid. Then, when those bubbles are coming out the top and surrounding the lid, stop the CO2 and install the lid. Virtually everything in that keg is now CO2-free. CO2 actually does have trace amounts of O2 in it, and the water with which the star-san is made has some O2 in it, but it's as good as you can do unless you're purging w/ fermentation-produced CO2.



So, now you have a keg filled with star-san and CO2 bubbles. Push out that Star-San into a 5-gallon bucket or, as I do, into another keg where you repeat the bubble process to make THAT keg O2-free. I always have a clean keg filled with Star-San and which has been purged using the above method so it's ready for the next brew.

When it comes time to rack beer to that keg, you can use a closed-loop system where you feed the CO2 in the keg that's displaced by the incoming beer back into the fermenter so you're not drawing air into the fermenter which starts to...well, oxidize the beer. Not clear how much oxidation that produces, but it's some, and how much depends on how long to rack. Here's how that looks:



When I first did this the only way to fit the tubing into the top of the fermenter was to cut off an airlock. A drilled stopper with a piece of rigid tubing such as that cut from a bottle-filler works as well and that's now what I use when I do things this way.

I have a Black QD attached to a piece of 5/16" silicone tubing that just fits over the end of the spigot on my fermenter so I can go directly into the keg. Usually that keg has some residual CO2 in it and I'll expel any residual star-san out that tubing--and then by doing that, I'm purging the tubing of air as well, and I'll even point that at the spigot to try to clear the spout. Yeah, nutso, but it's now habit, and not that hard a habit to get into.

When I'm going from conical fermenter to keg, I just use a jumper like this:



Now, I know some of this may look as if I'm incredibly anal about this. Well, maybe I am. All I know is that I've followed the continuous quality improvement approach throughout my brewing career (63 batches to this point), and that beer is great. Not just me saying that either.

 

[Jag75]

Mongoose let me see if I got this right . Once I fill my keg with water /starsan I fill with co2 . Then once the bubbles start to come out of the top secure the lid and disconnect from the co2. When I'm ready to fill with my beer I push the water/starsan solution out by connecting to co2 and push it out the (out) port just like beer . Then once it's all dispensed I hook up the (out) port to my fermenter exit line and the gas port of the keg connect with a hose to the airlock . When I push the water out will it be completely empty or have residual water at the bottom ? Thanks for the pics. This seems like a sure way to keep o2 out of the beer completely. Awesome idea. One more question. When you dump into the keg thru the ball lock does the beer drain in by gravity easily or do you have to use pressure to move it,

 

[mongoose33]

Mongoose let me see if I got this right . Once I fill my keg with water /starsan I fill with co2 . Then once the bubbles start to come out of the top secure the lid and disconnect from the co2. When I'm ready to fill with my beer I push the water/starsan solution out by connecting to co2 and push it out the (out) port just like beer . Then once it's all dispensed I hook up the (out) port to my fermenter exit line and the gas port of the keg connect with a hose to the airlock . When I push the water out will it be completely empty or have residual water at the bottom ? Thanks for the pics. This seems like a sure way to keep o2 out of the beer completely. Awesome idea. One more question. When you dump into the keg thru the ball lock does the beer drain in by gravity easily or do you have to use pressure to move it,

You'll have a little residual star-san in there. What I do is attach a QD to the OUT post and allow the pressure in the keg to blow out the little that's left. I end up with an empty, sanitized keg filled with CO2.

I've done a lot of racking from a fermenter using gravity only, and done others using pressure. Takes 20 minutes or more to just gravity drain, usually, during which time I go do something else. I like crashing that beer to the 30s so that when I'm racking into the keg, I get a condensation line on the side of the keg that shows me the progress, and when to stop.

 

[Jag75]

You'll have a little residual star-san in there. What I do is attach a QD to the OUT post and allow the pressure in the keg to blow out the little that's left. I end up with an empty, sanitized keg filled with CO2.

I've done a lot of racking from a fermenter using gravity only, and done others using pressure. Takes 20 minutes or more to just gravity drain, usually, during which time I go do something else. I like crashing that beer to the 30s so that when I'm racking into the keg, I get a condensation line on the side of the keg that shows me the progress, and when to stop.

Awesome ty sir

 

[ajdelange]

Whenever this is discussed I always mention, though I doubt it will be useful to many but in the hope that it may be to some, that I brew with steam and thus use steam to displace air from my kegs (Sankey) and, at the same time, sterilize them. As soon as the steam is disconnected from the keg, CO2 is connected. As the steam condenses it is replaced by CO2. The condensate is, of course, sterile (and the steam has been through a 'culinary' filter) and is simply blown out with some of the CO2. The end result is a sterile keg pressurized with CO2 and ready for back pressure filling.

 

[Jag75]

Whenever this is discussed I always mention, though I doubt it will be useful to many but in the hope that it may be to some, that I brew with steam and thus use steam to displace air from my kegs (Sankey) and, at the same time, sterilize them. As soon as the steam is disconnected from the keg, CO2 is connected. As the steam condenses it is replaced by CO2. The condensate is, of course, sterile (and the steam has been through a 'culinary' filter) and is simply blown out with some of the CO2. The end result is a sterile keg pressurized with CO2 and ready for back pressure filling.

You run steam through your fermenter and your kegs ?

 

[ajdelange]

Kegs yes, fermenters no. Those I sterilize with iodophor.

 

[4of7]

I have a 7.9 gallon fastferment conical. If I were to make a small batch say some where around 4 gallons in this fermenter the Co2 should protect the beer from oxidation even though the headspace is large. Now when I pull trub out I will lose some Co2. Do I lose too much Co2 that the beer is no longer protected by the large headspace?

Beer troll asking ,,when you pulled trub in the bottle,,where did the air go when the trub filled up jar?