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Fermenting with co2

Been reading and watching on fb about some home brewers. In england. Who are using co2 for primary fermenting anyone on this forum who did try this

our local brewery is fermenting with 5 PSI of pressure… They claim it finishes faster. Sneezles61

Saw an ad for a pressure fermentation vessel in last Zymurgy.

Fermentation produces co2 why add more. I guess there is science about fermenting under pressure but I’m not convinced. I guess people are always going to try and improve mother nature. I prefer to leave her alone


Think they just want to speed the fermetation up. This one dude. At 20 psi fermetation. But now i wonder if this does not stress the yeast. Me personally let nature take its course and just wait.

Most breweries ferment under pressure (spunding). Homebrewer’s are finally just catching up to that method.

So here’s the question I would have: With some yeasts, notably Wyeast 3724, “backpressure” from co2 buildup is hypothesized to slow or even stall fermentation. (See Drew Beecham et al) So…?
I wonder if it is, at least in part, to enhance flavor? To reduce loss of aromatics? Hop aroma?

Side note on the 3724, my last saison finished at 1.000 with no external heat applied. No stall. No airlock.

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My understanding is: suppressed ester production, allowing higher ferment temps, and thus reducing time from mash to glass. Of course the Co2 starts dissolving into solution, meaning they can use less Co2 for finishing up the carbonation process. Usually they start with a low head pressure (<5), then once they get a degree or two plato away from finishing gravity, they bump up the pressure to 12-14psi to begin the carbonation process. Then cold crash for a couple days, then transfer to brites for final carbonation and clearing.


Also, CO2 is a byproduct (wasteproduct) of yeast fermentation, and a metabolic poison to them. Why would you add something that stresses out your yeast and potentially limits full attenuation?

Fermenting under pressure is nothing new. There are multitudes of resources out there describing the process in detail.

To clarify: You’re not adding more Co2. You’re venting Co2 created during fermentation, by utilizing a spunding valve at a set pressue.

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EXCESSIVE CO2 is toxic and can prevent further fermentation. From my understanding the CO2 creates too acidic environment (carbonic acid) and prevents the cell from reproducing. Hence the reason pressure is built as fermentation subsides.

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