Capturing co2

[BigDave1303]

Hi.I've often thought about collecting co2 from a ferment but not done it yet. I have recently replaced my airlock with a blow-off pipe which runs into a 6 pint milk bottle & bubbles through a couple of inches of starsan mix. (See photos)

In theory:
After reading another post, have had the idea of placing the plastic milk bottle set up into the bottom of a spare 25 litre plastic fermenting bucket (lid on but able to vent through small hole on top) which hopefully should fill with the co2 & push the air out above it. This would have the advantage of sucking back co2 instead of air when I cold crash & bottle.
Not sure if I could work out a way of purging all of the bottles though. I'm not sure if o2 exposure is very high within the bottles. I suspect most of the exposure to the air is the larger surface area on top of the beer within the fermentor when air is sucked back in as the liquid level drops. So doing this co2 reclaiming should eliminate or at least reduce it.

Anyones thoughts?

 

[Golddiggie]

If your fermenter can handle pressure, just let it build a bit (depending on it's tolerance level) and seal it up before you cold crash. No connection to anything external means no chance of sucking anything back in. Hell, even if it can't handle more than 1PSI, just seal it up before you start the cold crash. I can't imagine it would create enough vacuum force to cause an issue. Then again, without knowing what the spec's of your fermenter are, it's difficult to say for certain.

 

[BigDave1303]

If your fermenter can handle pressure, just let it build a bit (depending on it's tolerance level) and seal it up before you cold crash. No connection to anything external means no chance of sucking anything back in. Hell, even if it can't handle more than 1PSI, just seal it up before you start the cold crash. I can't imagine it would create enough vacuum force to cause an issue. Then again, without knowing what the spec's of your fermenter are, it's difficult to say for certain.

it's a GF conical

 

[Golddiggie]

PSI tolerance levels?? If it's good for at least 1PSI, then you should be OK to just seal it up when you're done venting CO2.

I've started fermenting under pressure with my converted commercial beer keg fermenters (set up almost a decade ago now). Can easily handle the ~15psi I've let them sit at (via spunding valve). Once fermentation is complete, I simply remove the spunding valve setup and leave them completely sealed. Zero worries about sucking back anything this way.

I'll be thinking about getting some conical fermenters after I've moved and set up for brewing inside (can't do it where I'm renting, planning to purchase a house). I'll only LOOK at ones that are rated for 15psi (or above if possible).

 

[McKnuckle]

This kind of thing is easy to do if you have a spare keg, along with standard tubing and QD type connectors. You would hook up a tube from the fermenter to the keg's liquid port, then run a blow-off tube from the keg's gas port to a Star-San jar. Then if you cold crash, it's going to pull CO2 from the keg, and in an extreme case, liquid might run up the blow-off tube but would be contained in the keg. The fermenter would never come close to being affected.

The pipe you've got rigged up makes this a tad more challenging.

Keep in mind; CO2 is going to stay in the bucket and push out air only as long as there is positive pressure going into the bucket. As soon as that pressure stops, when fermentation is done, air will seep into the small opening on top and mix with the CO2. It really needs to be sealed to work as you intend it.

 

[BigDave1303]

This kind of thing is easy to do if you have a spare keg, along with standard tubing and QD type connectors. You would hook up a tube from the fermenter to the keg's liquid port, then run a blow-off tube from the keg's gas port to a Star-San jar. Then if you cold crash, it's going to pull CO2 from the keg, and in an extreme case, liquid might run up the blow-off tube but would be contained in the keg. The fermenter would never come close to being affected.

The pipe you've got rigged up makes this a tad more challenging.

Keep in mind; CO2 is going to stay in the bucket and push out air only as long as there is positive pressure going into the bucket. As soon as that pressure stops, when fermentation is done, air will seep into the small opening on top and mix with the CO2. It really needs to be sealed to work as you intend it.

Thanks for the info. I don't have any kegs (yet ).
Up until now I have always just used an airlock which has to be removed at the cold crash & bottling stages to prevent suck back from it. That's my reasoning of using stuff I already have i.e. spare plastic fermenting bucket. May not fully stop air getting in but has to be an improvement on removing an air lock which is guaranteed to pull in air.
If/when I get into kegging then pressure transfer will be the way forward & I will be able to set up as you have mentioned for venting the co2.

 

[Vale71]

In theory:
After reading another post, have had the idea of placing the plastic milk bottle set up into the bottom of a spare 25 litre plastic fermenting bucket (lid on but able to vent through small hole on top) which hopefully should fill with the co2 & push the air out above it. This would have the advantage of sucking back co2 instead of air when I cold crash & bottle.

Gases don't work like that in reality. In reality they mix quite quickly so that you will have an air/CO2 mixture in the bucket with an ever decreasing percentage of air as fermentation progresses. In theory there is enough CO2 produced during a standard fermentation to lower the O2 concentration to infinitesimally small levels but since you're using a simple plastic bucket that is anything but air-tight I doubt you will achieve that except maybe temporarily. At the latest when you have suckback air will be sucked into the bucket and will mix with the CO2 and you will still have oxygen being sucked back into the fermenter.

 

[BigDave1303]

Gases don't work like that in reality. In reality they mix quite quickly so that you will have an air/CO2 mixture in the bucket with an ever decreasing percentage of air as fermentation progresses. In theory there is enough CO2 produced during a standard fermentation to lower the O2 concentration to infinitesimally small levels but since you're using a simple plastic bucket that is anything but air-tight I doubt you will achieve that except maybe temporarily. At the latest when you have suckback air will be sucked into the bucket and will mix with the CO2 and you will still have oxygen being sucked back into the fermenter.

Hi, Thanks for your reply.
I realise I will never stop all o2 getting back in but my thinking is that it will be at a lower concentration, and will to be an improvement on just removing an air lock which is guaranteed to pull in 100% air.