Ever wonder how much CO2 you're making? - Home Brew Forums

 Home Brew Forums > Ever wonder how much CO2 you're making?

09-21-2008, 10:41 PM   #1
rocketman768

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Feb 2008
Evanston, IL
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=== Fermentation ===
1 mol glucose -> 2 mols ethanol + 2 mols CO2

=== Molar Mass ===
1 mol glucose = 0.180 kg glucose
1 mol CO2 = 0.044 kg CO2
1 mol ethanol = 0.046 kg ethanol

=== Thermodynamics ====
pV = nRT, where
p is pressure (Pascals = newtons per square meter)
V is volume (cubic meters)
n = moles of gas
R = gas constant = 8.314 N*m/( mol * K )
T = temperature (Kelvin)

How much CO2 does your priming sugar make (assuming it all gets converted)? If we add 4 ounces glucose which is 113 g, then we have added 0.113/0.180 mols = 0.628 mols of glucose. So, 2*0.628 mols = 1.256 mols of CO2 will be produced. So, now assume that the temperature is 20 Celsius (293 Kelvin) and we want to know the volume of CO2 at atmospheric pressure (1 atm = 101,325 Pascals). then V = nRT/p = (1.256*8.314*293)/(101,325) = 0.0302 m^3 = 30.2 liters of CO2.

So, 30.2 liters of CO2 are dissolved in your 5 gallons = 19 liters of beer! Well, in reality only 75% of the glucose gets consumed, so it's more like 0.75*30.2 = 22.7 liters of CO2, but still, that's a lot.

How much CO2 goes out of the airlock during fermentation? You could use the above procedure if you knew the equivalent amount of glucose that was originally in your wort. Since 1 kg of glucose dissolved to make 1 gallon of wort has a gravity of 1.097, divide your gravity in points by 97 points to get the equivalent kilograms of glucose per gallon of wort. Then multiply by the number of gallons to get the total kilograms of equivalent glucose. So if your gravity is 1.055 and you have 5 gallons of wort, then you have 55/97*5 = 2.84 kg of equivalent glucose that's available to ferment. If you assume that 75% of it ferments, then you get 0.569 m^3 = 569 liters of CO2 at room temperature and atmospheric pressure. No wonder my fermenter exploded last time I made that German ale...

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09-21-2008, 11:32 PM   #2
tdavisii

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Jan 2007
St. Louis
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dude that is deep.

09-22-2008, 12:22 AM   #3
friarjohn
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Aug 2008
Peoria
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So what your saying is i should get a couple plant for my brew room?

09-22-2008, 12:48 AM   #4
rocketman768

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Feb 2008
Evanston, IL
Posts: 1,083
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Quote:
 Originally Posted by friarjohn So what your saying is i should get a couple plant for my brew room?
Perhaps some barley??

09-22-2008, 12:51 AM   #5
niquejim
Burrowing Owl Brewery

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Jul 2007
Cape Coral Florida
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"Ever wonder how much CO2 you're making?"

No, not even once!

09-22-2008, 01:16 AM   #6
Moonshae

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Jan 2008
Helmetta, NJ
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Quote:
 Originally Posted by friarjohn So what your saying is i should get a couple plant for my brew room?
The light the plant needs might be detrimental to your brew, though...but if you keep it well covered...the plant could do well. I always start my spring veggies in the basement, in the brew room...I just have to maintain a temp balance that works for both. In the huge space of the room, the extra CO2 is minimal, but every little bit of extra helps.
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09-22-2008, 01:34 AM   #7
FishinDave07
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Oct 2007
South Florida
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For a second there, I thought this was going to be a Global Warming thread...

Some serious chemistry you got going on there.
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09-22-2008, 02:41 AM   #8
homebrewer_99

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Feb 2005
Atkinson (near the Quad Cities), IL
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Rocketman...all I can say is YOU NEED TO GET A HOBBY!!!!

Leave that brainiac stuff behind and go brew something!!!

I thought it too deep also, but if it floats your boat...
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09-22-2008, 02:44 AM   #9
Soperbrew
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09-22-2008, 02:58 AM   #10
Fingers

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Jan 2007
Lac du Bonnet, Manitoba
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rocketman, you neglected the other side of the equation. How much CO2 was absorbed by the barley and hop plants? It would be interesting to see if brewing were actually carbon neutral or not (discounting shipping impacts).
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