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Old 09-21-2008, 10:41 PM   #1
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Default Ever wonder how much CO2 you're making?

=== 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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Old 09-21-2008, 11:32 PM   #2
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dude that is deep.

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

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Old 09-22-2008, 12:48 AM   #4
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Quote:
Originally Posted by friarjohn View Post
So what your saying is i should get a couple plant for my brew room?
Perhaps some barley??
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Old 09-22-2008, 12:51 AM   #5
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"Ever wonder how much CO2 you're making?"

No, not even once!

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Old 09-22-2008, 01:16 AM   #6
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Quote:
Originally Posted by friarjohn View Post
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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Old 09-22-2008, 01:34 AM   #7
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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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Old 09-22-2008, 02:41 AM   #8
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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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Old 09-22-2008, 02:44 AM   #9
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What about the off flavors?

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Old 09-22-2008, 02:58 AM   #10
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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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