How much gas can yeast produce?

Question

gas - carbon-dioxide.

Answer 1

The theoretical maximum amount of CO2 that yeast can produce is 2 molecules of CO2 for each molecule of sugar that is available (see refs 1 & 2).  This assumes that the yeast a perfectly efficient and can convert all the sugar to ethanol, which of course, they can't.

If you brew 5 gallons of beer, your starting mixture might have in it about 1.6 kg of sugars, and this would generate about 800 grams of CO2.  This is way more than the 120 grams of CO2 that will give you a saturated solution (full carbonation), so the excess has to exit through the gas trap.  My crude calculations (based on a density of CO2 gas of 2 kg/m³) is that brewing 5 gallons of beer would generate up to 0.4 m3 of gas, of which about 15% would go into solution in the beer (later to produce bubbles and head).

(Mmmm, makes me thirsty for some India Pale Ale :-)