Fermentation produces carbon dioxide as a direct by-product of yeast converting sugar to alcohol — roughly the same amount, per hectoliter, that most breweries then turn around and purchase for carbonation and packaging. That coincidence is the cleanest arbitrage available in a brewhouse: capture the gas you're already making, and stop buying the gas you're currently venting.
The numbers line up more closely than you'd expect
Published figures put purchased CO₂ at roughly 3.9 kilograms per hectoliter of beer for a typical small-to-mid craft brewery, and fermentation itself generates CO₂ at almost exactly that same rate. In other words: a brewery isn't buying gas because it doesn't produce enough of its own — it's buying gas because the gas it produces goes straight up the fermenter vent.
What a recapture system actually does
A CO₂ recovery system draws gas off the fermenter headspace during active fermentation, scrubs it of contaminants (primarily removing entrained foam, water vapor, and volatile organic compounds), compresses it, and liquefies or stores it for reuse in carbonation, packaging, and purging. It is mature, well-understood technology — the barrier at craft scale has never been whether it works, but whether the batch volume justifies the capital.
What it costs
A recapture system sized for a small European craft brewery has been documented at roughly €67,000 installed, with a payback in the neighborhood of five years at that scale — largely a function of purchased-gas prices and how many fermenters can feed a single recovery unit. Larger sites see faster paybacks because more fermentation volume amortizes the same core equipment.
Why it's rarer at true craft-distillery scale
A distillery's wash also ferments before it ever reaches the still, venting CO₂ at a comparable rate per liter of alcohol produced — pure fermentation stoichiometry. Recapture at that scale is genuinely uncommon today, mostly because batch volumes are small relative to the fixed cost of the recovery equipment. That's an economics problem, not a chemistry problem, and it shifts as soon as someone builds a right-sized unit for that scale.
How to size the decision
The question isn't whether recapture works — it's whether your annual purchased-CO₂ spend, projected forward, clears the hurdle rate on the capital. That's a straightforward calculation once you have twelve months of gas invoices and your actual fermentation volume; it's usually the first number we run in a metered assessment for a brewery of meaningful size.