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...

 

dude that is deep.

 

So what your saying is i should get a couple plant for my brew room?

 

Perhaps some barley??

 

"Ever wonder how much CO2 you're making?"

No, not even once!

 

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.

 

For a second there, I thought this was going to be a Global Warming thread...

Some serious chemistry you got going on there.

 

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...:rockin:

 

What about the off flavors?

 

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).

 

Don't let these guys bother you. I couldn't compute it myself, but there are times when I wish I had that type of knowledge.

 

Well, it's right at the top of the post!

 

Now compute the volume of methane produced by the yeasties as they travel through my digestive system.

 

Sometimes I wonder if sitting at the computer in the same room as my bubbling fermenters is going to increase the amount of retarded in my head.

 

Why discount shipping impacts? I mean, what if your barley is grown on one near you but the malter is on the other side of the country?

I would guess few agricultural crops are truly carbon neutral, with the amount of artificial fertiliser and tractor diesel used in their production.

 

Does that mean we are contributing to global warming?

 

All the CO2 that is being released by the fermentation is from carbon that was fixed by barley plant from its carbon source: CO2. There is no "new" carbon being released here as you get from the combustion of a fossil fuel.

I knew there was a lot of CO2 being released. I get a few fruit flies in my chest freezer and after a good vigorous fermentation they are all dead.

 

No more so than buying intensively farmed fruit and veg... It's true that the fermentation aspect is carbon neutral. It's the agricultural processes that are fueled by diesel/petrol that aren't...

The energy used to produce the glucose comes from the sun,
the energy used to get the seeds into the groud, the crop harvested, processed, and shipped are not.

 

Haha. There are several posts related to global warming here, but that wasn't my intention at all. I just thought it would be neat to know how much gas is bubbling out of the airlock and how much is in a normal beer when I realized it was really your typical college physics problem.

But, as someone else pointed out, you're not releasing any NEW carbon except that which you use to boil the wort. In fact, take a look at the reaction for fermentation I posted: C6H12O6 -> 2C2H6O + 2CO2. So, there are 6 carbon molecules coming in as glucose, and 2 coming out as CO2. The other 4 are stored in the good old ethyl alcohol (C2H6O) that you drink and digest into acetaldehyde (I don't know what happens after this point...I'm no biochemist).

 

Check out the little video in my signature. It summarizes the biology of alcohol ingestion.

 

How much energy could you harvest if you attached a little windmill fan to the top of your carboy?