Why fermenter to carbonation transfer

In other threads it has often been discussed that you ferment in a fermentation vessel and the CO2 is vented. Then after fermentation we transfer to a keg, or bottles and add priming sugar or pressurized CO2 for carbonation. Why do we waste the CO2 produced in the fermentation? Why do we not have a vessel for fermenting that does not vent all of the CO2 but rather allow you set a pressure in the fermenter so that when fermentation is complete you have fully carbonated beer. I am certain that a dispensing method could be devised so that you could either dispense from the fermenter or even bottle from the fermenter. Seems like we are wasting an opportunity.


That’s an interesting idea… I suppose the increased pressure will increase carbonic acid in the fermenting beer, which may impact yeast health. Also, increased pressure can stress yeast, but I don’t know where the threshold is for causing problems. One thing I’ve heard, although it’s really just anecdotal, is that the pressure in commercial size fermenters can increase the likelihood of autolysis, which is why we don’t really need to worry about it on the homebrew scale.

Not trying to shoot down your idea, because it’s a good thought. Just throwing out some discussion points!


Unless you brew the same beer a lot and know exactly what to expect, it can be tricky to end up with exactly the carbonation level you want without a special pressure release valve.

But fermenting under pressure does change the way the yeast act. The big breweries do it because if done properly, it speeds the fermentation, and any time they can cut out of the process has direct business benefits. That said, I don’t know the details, and I’ve never tried it. Like I said in another thread recently, I’ve never been in that much of a hurry for the beer to finish.

No “special” pressure release valve needed, just the typical fitting on the gas-out side of your keg connected to a brass T, pressure gauge on a second outlet of the T, then thread one of these onto the third outlet:


Vacuum and Pressure Adjustable Brass Relief Valves

48935K25 $7.53

I transfer to the keg after initial fermentation slows down, add priming sugar, hook up the pressure release described above and carbonate naturally in the keg. It also has the benefit of the beer on the lees for improved flavor and shelf life stability over time.