Harvesting CO2

[tubbsy]

All homebrew forums and groups I've been a part of have suggested using CO2 from the fermenter to purge kegs and/or push out a sanitiser. But I read several members on probrewer saying CO2 from fermentation is not suitable unless filtered, which costs quite a bit. Why would this be? Surely there's no contaminates that would spoil a keg?

 

[MHB]

The guys on Pro Brewer are right.
In Germany where they aren’t allowed to buy in CO2 and get all of it from the ferment. They tend to let the first third to half vent to atmospher as it is contaminated with Oxygen, contains quite a bit of DMS, other esters and often some bacteria.
They then filter to remove odours and other bits and pieces, dry, compress and store the CO2 in what is called a Balloon for later reuse.
Given the cost of bottled CO2: most people are paying ~$10/kg or (~20 cubic meters @ 20oC and 1 Bar) and the inherent risks of reusing gas without proper treatment and filtration, I'll keep buying it thanks.
Mark

Edit sorry
Its about 50m^3
M

 

[tubbsy]

Thanks Mark.

I'm paying around $100 (after the included bottle in the $79 plan) for a 6kg bottle through BOC as I don't have anywhere nearby that does refills and am going through ~3 bottles a year. It might be worth my while to upgrade to the G plan for $179/year and forget about harvesting CO2.

 

[S.E]

Thanks Mark.

I'm paying around $100 (after the included bottle in the $79 plan) for a 6kg bottle through BOC as I don't have anywhere nearby that does refills and am going through ~3 bottles a year. It might be worth my while to upgrade to the G plan for $179/year and forget about harvesting CO2.

Well the guys on Pro Brewer are nearly right. In a commercial setting CO2 from fermentation is not ideal unless filtered but for us home brewers it is fine.

Home brewing can be as simple or complicated as you want to make it. The trend these days is to copy large commercial brewery methods as near as possible. Reading this and other forums you would be forgiven for thinking it is compulsory to ferment in a closed fermenter ideally under pressure and then transfer to purged kegs without letting the beer come into contact with any oxygen.

When I started first started kegging in the UK it was the norm to ferment in an open bucket and only put the lid on near or at the end of fermentation. The beer was transferred to un purged kegs and primed. The only CO2 available to me at the time were these 240g Hambleton Bard cylinders that were only used for dispensing. From memory they were about 3 or 4 pounds to refill and I soon realised that it was cheaper and easier to go back to cask conditioning and gravity dispensing from cask even if I ended up with a few wasted pints of oxidized beer.

I do use bottled CO2 now as it is so cheap and easily available from KK and KL but for a long time I harvested CO2 from a sealed fermenter and used it from a collapsible polypin when dispensing cask ale instead of just venting and letting in air. It worked very well and if CO2 was not cheap and easily available for me I wouldn’t hesitate in doing it again.

@tubbsy as it would be so easy to connect a fermenter to kegs and purge them I suggest you try it for yourself first before up grading your CO2 plan. Or perhaps just don’t bother purging kegs, many commercial breweries don’t do it.

 

[fifis101]

It hasn't seemed to cause me any issues over the last year since I've been doing it. If you had any concerns about oxygen then just leave the keg connected for longer. My keg is normally purged of sanatiser within the first 24 hours but you could always just leave it connected for longer and keep purging. I'm not sure how much CO2 actually comes off a brew but it'd be many kegs worth over the whole brew.

Brew under 25psi and you also don't have to force carbonate. Other than a few odd times, the only thing I use my CO2 bottle for is to push the beer out of my kegerator.

 

[S.E]

I'm not sure how much CO2 actually comes off a brew but it'd be many kegs worth over the whole brew.

I’m not sure what a fully inflated polypin holds but I would guess about 20L to 30L. I used to fully inflate a polypin with CO2 in around half hour or so from a 60L fermenter.

 

[Vic]

It hasn't seemed to cause me any issues over the last year since I've been doing it. If you had any concerns about oxygen then just leave the keg connected for longer. My keg is normally purged of sanatiser within the first 24 hours but you could always just leave it connected for longer and keep purging. I'm not sure how much CO2 actually comes off a brew but it'd be many kegs worth over the whole brew.

Brew under 25psi and you also don't have to force carbonate. Other than a few odd times, the only thing I use my CO2 bottle for is to push the beer out of my kegerator.

Have been using CO2 from the fermenter after 24hrs of active fermentation to purge sanitizer from kegs for many years without any problem. When active fermentation is on the way and all O2 gone from headspace increase pressure using sounding valve to 5PSI or so and start purging. Free CO2.