CO2 scincey type stuff questions

[Kirkwooder]

OK,right now I have an IPA going blurp, blurp, blurp,blurp, blurp, and an empty CO2 tank that needs filling.

Being the car/tool guy that I am, I'm thinking that an old air compressor and some fancy tubing could capture the wasted CO2 escaping into my cellar way, and put it to good use when I need it to push beer out of a tap. It seems simple enough that everyone should be doing it. Witch leads me to believe that it isn't as easy as all that.

Does anyone know the science behind compressing CO2?

 

[grampamark]

The short answer-if you have to ask, you can't afford it.

C02 is stored, under very high pressure, as a liquid, which vaporizes when the valve is opened (C02 boils at -110°F). A suitable compressor would probably cost >$20K. Our fire dep't bought a used high pressure air compressor from a dive shop that was going out of business; paid around $4K, as I recall, almost 20 years ago. And that was just for compressing breathing air, not pure C02.

You can harvest C02 by fermenting in a keg, with a spunding valve, which will allow your beer to partially carbonate during fermentation and then use the naturally produced C02 to push the beer into the serving keg. Thread about that here.

 

[Kirkwooder]

What other gasses are produced/released during fermentation? How pure do you need the CO2 that pushes beer out of a tap?

My thinking is that the gasses produced during the bottle conditioning process seems to make for pretty good beer. A home brewer doesn't really need great volumes of CO2 for serving, so high pressures aren't really needed to save large volume in a liquid form.

I would think that a 5 gallon tank with 125psi of fermentation produced CO2 would be plenty to push 5 gallons of beer out a tap at tap pressures.

CO2 is heavier than air and should displace atmospheric gasses out the top of a sealed container, such as a fermentation vessel. There should be some way to collect and compress this gas for reuse.

Are there any reasonably priced measuring devices for CO2 content in a gas that would let you know if a trapped gas would be suitable for beverage serving?

Forgive me if I am missing something, I feel a little bit like Zach on Big Bang Theory when I think about these things.

 

[LayerUp]

Couple high level thoughts, by no means is this all inclusive.

1) yes, the molecular weight of co2 is higher than the molecular weight of n2, so it will "sink" in a container. Couple issues with this thought, however. First, the higher the temperature, the less the density difference, second, this also assumes no external energy is applied to the system. Have you ever seen one of your cool buddies blow a sweet-ass vape cloud? Think about all the vortices and eddy currents that develop in the vapor when your buddy blows with a little force from his lips. Now think of the how things like walking past the container full of gas, or an hvac system kicking on, or your refrigerator compressor starting up, and you can see it will be very difficult to keep the air still.

2) the fermentation byproducts are not solely co2. You have numerous gases that escape as fermentation occurs, this is why you can smell smells from the airlock. The concentration of co2 is based upon the principles of Henry's law (please, look it up). Identifying and isolating the co2 is no trivial task.

3) your airlock is dispensing gas at a pressure slightly higher than 1atm. This is a very low partial pressure. You will need to determine how to capture this volume in a very large, slightly vacuum sealed container, in order to collect enough to have any chance of compressing and condensing it. The only other option would be to constantly run the compressor and pull off the gases as fermentation occurs. If you do that.,You will pull a partial vacuum between the airlock and compressor, and cause the airlock to boil, followed by your beer. If you elect to try and store the co2 offgas in a pressurized contain, well, now your fermentation carboy is a pressure vessel. Hope it's rated for the loads.......

Typed up on my phone while brewing beer, please excuse any typos

 

[day_trippr]

Even though pure CO2 has a higher molecular density than "air" and hence could in theory fall to the bottom of a vessel, the gas mix in said vessel will rapidly homogenize due to molecular motion alone. Outside of extreme laboratory conditions the whole "CO2 blanket" thing is a myth.

As for the proposal, I doubt it has any chance of practical application, even discounting the economics of getting close to success...

Cheers!

 

[Kirkwooder]

OK so driving 60 miles round trip to fill a tank is still my best bet. Thanks for the info!

 

[isomerization]

Sounds like you should buy a larger tank or more tanks, will pay off in the long run on less trips.