Collecting CO2 From Fermentation

[Gnomebrewer]

Until you have proof a hypothesis is nothing more than an unproven idea.

That is correct. Hence the word I used was 'possibility'. I'm not discounting an idea that hasn't been tested (AFAIK) either way. That IS how science works.

With the same logic you could say that you firmly believe that dragons could exist until someone publishes a study proving otherwise.

That is most certainly not the same logic and is (obviously) absurd. My logic is that there is something with anecdotal evidence and nothing disproving it (AFAIK). That makes it possible and worth testing. The idea that the minuscule amount of pressure from an airlock could cause a stalled ferment is, IMO, not worth testing as it's so extremely unlikely.

And of course primary fermentation and bottle carbonation are exactly the same

This is the statement that is not correct. I've given two valid reasons why they are different, but you choose to skim past them. Also, there are cases of stalled ferments being bottled, only to then continue fermenting in the bottle eating the priming sugar and remaining sugars from the stalled ferment. But that of course is impossible if primary fermentation and bottle carbonation are exactly the same.

Could a small amount of oxygen during fermentation help the ferment of notorious stallers such as WY3724? Maybe not, but I'm not completely discounting it.

 

[wstumper]

Might be hard to believe but still true. In regards to oxygen contamination, fermentation derived CO2 is far superior to bottled gas. Industrial ethanol production is the best/cheapest source for low O2 carbon dioxide.

"In addition to ethanol, carbon dioxide (CO2) is also produced during fermentation. Usually, the carbon dioxide is not recovered as a sellable product. If recovered, this carbon dioxide can be cleaned, compressed and sold for carbonation of soft drinks or frozen into dry-ice for cold product storage, for sandblasting in car service and metal industry, etc. If the carbon dioxide is not recovered, it is cleaned and vented to the atmosphere."

State of the Art in Bioethanol Production, Agronomy Research, 2010 Vol.8 No.Special 1 pp.236-254.

Emphasis mine.

CO2 is not the only byproduct of ethanol production and fermentation. Otherwise, they wouldn't have to "clean" the CO2.

Enough said...

 

[Bilsch]

Enough said...

I'm sorry but you are quoting old information. These days about 40% of all the CO2 in industry comes as a byproduct of fermentation. This carbon dioxide captured from ethanol production already comes off at better than 99% and the major impurity is water and ethanol vapor with minor amounts of sulfur which makes it very suitable for food and beverage applications. The other sources of CO2 come from hydrogen, ammonia, natural gas, coal or hydrocarbon production industries and are full of all kinds of impurities such as: N2, O2, Ar, CO, H2, CH4, NO2, SO2, COS, H2S, Cl, Hg, As, Se, ash etc.

So all CO2 must be cleaned after capture but one source for it much less than the rest.

 

[kevink]

Actually, saving fermentation CO2 is on average more expensive than buying it bottled. For small breweries it's even prohibitively expensive as the gear requires an investment upwards of a million dollars.

Of course there is a large up-front cost, but the whole point is to save money in the long run. It's like buying a canning line. You pay for it up front, but it makes money after it's payed off. Just like every other piece of equipment in a brewery.

 

[Vale71]

Of course there is a large up-front cost, but the whole point is to save money in the long run. It's like buying a canning line. You pay for it up front, but it makes money after it's payed off. Just like every other piece of equipment in a brewery.

You're comparing apples to oranges here. Unlike other equipment in the brewery you have an alternative here, i.e. buying bottled CO2 instead of capturing your own. On average, captured CO2 is about 20-30% more expensive than buying it bottled, and that's when all running costs and amortizations and whatnot are properly taken into account. If it's costing your business 20-30% more than the alternative how could you claim to be saving money?

 

[kevink]

I guess everything I have read is wrong, then.

 

[SanPancho]

The yeast you are thinking of is saison. Notorious for stalling out. But remove the airlock and it keeps going. Seems odd but its been written about forp quite some time.

 

[Gnomebrewer]

A bit off topic, but quite an interesting read on recapturing CO2
https://spinoff.nasa.gov/Spinoff2016/cg_3.html

 

[VirginiaHops1]

I don't see the point as CO2 is so freaking cheap. One 20lb tank, which costs around $25, lasted me through 19 10 gallon batches. With that one tank, I purged all 38 kegs prior to filling, pressure transferred every batch, crashed every batch under CO2 pressure, partially carbonated all 38 kegs, purged growlers, and probably did other things with it that I can't remember during that time period. It is totally not worth the hassle of trying to use CO2 from fermentation in my opinion. It seems like it's a solution to a problem that does not exist.

Even if I ONLY purged the 38 kegs with that one tank, it only would have cost 65 cents per keg to purge. Is that worth trying to save?

I've purged my serving keg both ways, typical water purge and purging with fermentation gas via hooking up with jumpers during fermentation. It's actually less hassle and easier/quicker for me to purge with fermentation CO2. I just sanitize the serving keg, hook it up with a jumper and that's it. The main reason I don't always do it is I often don't have an empty serving keg when a fermentation starts.

 

[hmmy92]

at 1 bar overpressure you'll need only 3.9 g/l or 74 g for a 19 liter keg, hardly a ton.

Can you explain the math?

 

[doug293cz]

Can you explain the math?

CO2 at 1 atm pressure (about 1 bar) and 0°C (32°F) has a density of 1.9771 g/l. At room temp (20°C) the density will be ~ 1.9771 g/L * 273.15/293.15 = 1.8422 g/L. At 1 bar over pressure (2 bar absolute pressure) the density will be double, or ~3.7 g/L. (The 3.9 from @Vale71 omitted the temperature correction.) A "5" gal keg actually has a volume closer to 20 L. So, if you set your CO2 regulator to 14.7 psi (1 bar over pressure), you will need 3.7 g/L * 20 L = 74 g of CO2 to push all the liquid out of a completely full keg.

Edit: If you set your regulator to 5 psi (a more reasonable pressure for pushing StarSan out of a keg) you would use 1.8422 g/L * 20 L * (14.7 + 5)/14.7 = 49.4 g of CO2.

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