Carbon dioxide emitted during fermentation?

[Pdgillis]

Just wondering if anyone was able to get an estimate on how much co2 is given off from your normal 5 gal batch. I remember reading some years ago about someone weighing their beer as it ferments and 4lbs of co2 is what seemed to be the magic number.

I have a temp controlled fermentation freezer vented into a 4x4 grow tent. Every time I open the tent I can smell the fermentation and figure their must at least be some benefit to the plants.

Just wondering if anyone has tried anything similar before?

 

[day_trippr]

Here are a couple of charts on the topic.

Imperial:

Metric:

I've not yet exploited CO2 production to at least purge vessels but I'll get to that eventually...

Cheers!

 

[GnenieGone]

Doing my part to screw the grandkids!

 

[mongoose33]

Roughly 20-25 volumes of CO2. Which means 100-125 gallons. That's equivalent to about 15 cu feet, give or take.

Which, FWIW, pretty much matches @day_trippr 's charts above. Depends on OG plus how much attenuation, but that's roughly what you'll get for a mid-range beer.

 

[Veets]

Just wondering if anyone was able to get an estimate on how much co2 is given off from your normal 5 gal batch. I remember reading some years ago about someone weighing their beer as it ferments and 4lbs of co2 is what seemed to be the magic number.

I have a temp controlled fermentation freezer vented into a 4x4 grow tent. Every time I open the tent I can smell the fermentation and figure their must at least be some benefit to the plants.

Just wondering if anyone has tried anything similar before?View attachment 619542

Cool idea.
What's in the tent?

 

[day_trippr]

Something dank and sticky, hopefully

 

[Pdgillis]

Gotta love being in Canada!

 

[Pdgillis]

They’re a little sad because I just transplanted them to the bigger pots.

 

[Terpene]

OP, you could calculate it stoichiometricly, based on the overall chemical equation:

1 glucose --> 2 ethanol + 2 CO2.

So for every mole of glucose, you get 2 moles of CO2.

You would have to estimate the conversion from gravity points to grams glucose equivalent. Then from grams glucose, convert to moles glucose, then multiply by 2 to get moles CO2, then convert to grams CO2.

It shouldn't matter that wort contains other sugars. The calculations should come out the same. You'd want to use only fermentable gravity points in the calculations, as unfermentables are, well, unfermentable.

Basic chemistry.

 

[Blazinlow86]

Gotta love being in Canada!View attachment 619619

I also love being in Canada and have a few tents going myself. However as a friendly reminder being in Canada won't help you legally as it looks like you have 4-5 times the legal plant count therefore your grows just as illegal as it was years ago. Cheers

 

[day_trippr]

That may be the first "narc" of a post on HBT!

[btw, love the buds on that squat plant! ]

 

[Blazinlow86]

The ones in the far right tent are auto flowers that will be harvested in the next few days. The others are feminized. Cheers

 

[Terpene]

OP, you could calculate it stoichiometricly, based on the overall chemical equation:

1 glucose --> 2 ethanol + 2 CO2.

So for every mole of glucose, you get 2 moles of CO2.

You would have to estimate the conversion from gravity points to grams glucose equivalent. Then from grams glucose, convert to moles glucose, then multiply by 2 to get moles CO2, then convert to grams CO2.

It shouldn't matter that wort contains other sugars. The calculations should come out the same. You'd want to use only fermentable gravity points in the calculations, as unfermentables are, well, unfermentable.

Basic chemistry.

By way of example, let's say we have 5 gallons of 1.054 all grain malt wort that we estimate will ferment down to 1.008. That's 46 fermentable gravity points.

Now, from Beersmith's grain chart (thanks, Brad), we know corn sugar, which is essentially pure glucose, has a max PPG of 46 points. That means if we dissolve 1 pound in 1 gallon of water, we get a 1.046 solution. So, to get 46 fermentable points in 5 gallons, we'd need 5 pounds of corn sugar, or 2268 grams.

Ok, stay with me here.

From wikipedia or a periodic table, we get molar masses:

Glucose 180.156 g/mole,
CO2 44.0 g/mole.

So, our moles of glucose = 2268/180.156 = 12.59 moles glucose.

Based on the chemical equation for fermentation, we therefore will have 12.59 * 2 moles of CO2 = 25.18 moles CO2.

Converting back to grams we have 25.18 * 40.0 g CO2 = 1007 g CO2.

That's about 2.22 pounds of CO2 we can expect from our 5 gallons of 1.054 all grain wort, as an estimate.

It matches very closely with day_tripper's handy charts.

Just wanted to offer a back-to-basics example, in case anyone is interested in how this is calculated from first principles.

 

[Vale71]

You forget yeast is not a chemical reactor but a biological one, which means yield is <1. The reason being the yeast does not just make ethanol for our enjoyment but also needs some of the sugar for its own metabolism. The accepted parameter in the technical literature is 2.06g of fermentable sugar needed to produce 1g of CO2.

 

[Terpene]

You forget yeast is not a chemical reactor but a biological one, which means yield is <1. The reason being the yeast does not just make ethanol for our enjoyment but also needs some of the sugar for its own metabolism. The accepted parameter in the technical literature is 2.06g of fermentable sugar needed to produce 1g of CO2.

All biological reactions and pathways *are* chemical reactions, and stoichiometry *always* applies, whether we're talking yeast, bacteria or humans. This is fundamental biochemistry. Conservation of mass applies. There is no Angel's share.

No, the yeast does not use *some* of the sugar for its own metabolism -- it uses *all* of the sugar for its metabolism. Every drop of ethanol produced in yeast fermentation is the result of yeast metabolism, and that metabolism is described, in summary, by the chemical reaction:

glucose --> 2 ethanol + 2 CO2.

(This is a combination of the Glycolysis Pathway and the Ethanol Fermentation Pathway.)

Now, if the literature states 2.06g sugar produces 1g CO2, it's a believable experimental result, and it's pretty darn close to what's predicted by my example, which is 2.25 g sugar.

So why the small discrepancy? Well, there are reasons, but it isn't what you think. In my view, it very likely relates to cell growth and the storage of glycogen and other sugars in each cell. But that's a whole different subject, an interesting one, but perhaps not too relevant to this thread.

Hope that clears some things up.