trying to achieve a cheap CO2 storage system

[waynetempro]

Your initial design is OK but has some flaws. Here’s my improvement on it. Use two (2) corney kegs. Run the CO2 out of the fermenter to the first keg. Out of that keg to the compressor then through a charcoal filter to the second keg. You will have to build an activation circuit using a barometric sensor that can be placed inline with the first keg to turn on the compressor. The sensors are cheap: https://a.co/d/g9sAkIB
But like I mentioned, you will need to build the controller using an Arduino or similar device. And is course, you will need to purge the system before collecting CO2.
And in case your brew makes, too much CO2, just keep a third keg handy to switch out to handle the overflow.

 

[Bassman2003]

I see the goal as pure CO2. The convenience of using tank CO2 does not reach the goal of pure CO2.

The problem I see with using fermentation gas to purge vessels that then purge other vessels is not knowing when you have pushed through all of the oxygen out of the system. If you start with a keg, that keg either needs to be liquid CO2 purged (kind of defeating any kind of gas savings) then you have to push enough fermentation gas through to consider it O2 free. Only then can you start cramming pure CO2 in your 2nd keg. How much will you capture until fermentation expires? That is the question.

If you naturally carbonate, you could probably get enough to serve an entire keg. Is it worth the effort? Depends upon how easy and inexpensive the setup might be. If it is 'set and forget' once you get it built and tested, it might be worth it.

 

[DuncB]

You need to purge the corny of starsan with ferment gas after all oxygen used up.
Then start the capture compression phase.

 

[Ale-75-IT]

Thanks all for your interest in my project!

If I was in the "don't do anything" situation I wouldn't have started homebrewing. I think producing wine at home (my grandfather did for a long time of his life) is really annoying, BUT producing beer at home is certainly worse (my wife says yes with her head).

Producing beer is a waste of money, a waste of time, a waste of brain activity. Why not buy and drink good beers?

So please I and you don't go OT. Thank you!

 

[Ale-75-IT]

OP says

So the otherwise sensible suggestion to just buy CO2 (and a tank) may not be important in this unusual case.

I wonder how cheap a CO2 capture widget would have to be for me to want one.

Partially replied above, but it's not only a matter of costs, it's the pleasure to DIY.... harvest my own CO2, like I (try to) harvest my hops (similar situation, where you won't ever reach commercial quality or easy of use).
I'm not sure everyone can understand and agree, but hey, it's ok...
(promised not to go OT and failed )

 

[Ale-75-IT]

I still believe that you are going to be collecting CO2 contaminated with oxygen and nitrogen that diffuses into your bag.

I tried to look for some articles on the diffusion of gases through plastics to preserve food, but after reading two and don't finding an answer, I broke...
Until you or I find some evidence there's little point in discussing it, don't you think?

Your initial design is OK but has some flaws. Here’s my improvement on it. Use two (2) corney kegs. Run the CO2 out of the fermenter to the first keg. Out of that keg to the compressor then through a charcoal filter to the second keg. You will have to build an activation circuit using a barometric sensor that can be placed inline with the first keg to turn on the compressor. The sensors are cheap: AEDIKO 4pcs Air Pressure Sensor Module 3.3-5V Digital Barometric Liquid Water Level Controller Board 0-40KPa Air Pressure Sensor Connect 2.5mm Soft Tube: Amazon.com: Industrial & Scientific
But like I mentioned, you will need to build the controller using an Arduino or similar device. And is course, you will need to purge the system before collecting CO2.
And in case your brew makes, too much CO2, just keep a third keg handy to switch out to handle the overflow.

the only problem with your setup, which is also the main reason why it is necessary to put the compressor inside a container (bag or rigid one) is that there are no cheap and oil-less compressors with an air inlet connector. I only found some vacuum pumps but they seems not to reach 8 bar on the air-out.

As for now I think I'll go with the bag, try to produce some control board and see what it happens and how it's reliable on the long run.
Food grade bags are quite resistant, they can handle about 0,5 bars (7 psi), and they "shoud" (see above) protect food by gases, in primis by oxidation, but I can be wrong!

...The problem I see with using fermentation gas to purge vessels that then purge other vessels is not knowing when you have pushed through all of the oxygen out of the system. If you start with a keg, that keg either needs to be liquid CO2 purged (kind of defeating any kind of gas savings) then you have to push enough fermentation gas through to consider it O2 free. Only then can you start cramming pure CO2 in your 2nd keg. How much will you capture until fermentation expires? That is the question.
...

I thought of two ways to get rid of the O2.

the first is to pass a lot of CO2 through the system. As you stated, you'll never be sure you've removed all the O2, but if the system survives over time, each load of new CO2 will dilute the oxygen more and more until it becomes irrelevant.

The second is to sanitize the keg (imaging only one keg in the system, used as storage of compressed CO2), to fill it with sanitized water and to initially purge all the water out with CO2.

Emptying the bag is very easy by its nature, it is made for this purpose: all the air is sucked out.... It will never be completely free of oxygen, because of compressor who has some "dead spaces", and there are pipes too, but if it lasts over time the things will get better (see statement above).

Tx and bye,
Ale

 

[DuncB]

@doug293cz
Has done all of the calculations for you in the thread mentioned earlier about gas purging of kegs, volume needed etc.

A simple experiment for permeability would be to fill one of your bags with some beer, seal it up and leave it at room temperature. Keep it out of sunlight and you'll see it oxidise ( get more orange coloured).


I've never taken a compressor apart but there must be a point where the gas collection goes into a cylinder and an opportunity at that point to fit tubing to go to a different reservoir, pre compression vessel.

MIght be worth a look.

 

[Ale-75-IT]

....
I've never taken a compressor apart but there must be a point where the gas collection goes into a cylinder and an opportunity at that point to fit tubing to go to a different reservoir, pre compression vessel.
....

I've took apart mine and it takes air from a little hole... very difficult/impossible to attach some connector/tube and have a good seal (to avoid O2 intake).
The only ones that have a serious air intake are vacuum pumps but as said, no way to find a cheap one that can compress air to adequate pressures.

 

[Ale-75-IT]

...
A simple experiment for permeability would be to fill one of your bags with some beer, seal it up and leave it at room temperature. Keep it out of sunlight and you'll see it oxidise ( get more orange coloured).
....

i you want to study oxidation in the bag you'll need a "blind" comparison . (EDIT: mmm, no, it's not "blind" it's only a comparison, sorry)
For example a glass jar in the same conditions of temperature and light exposition.

For now it is not my priority but you have given me food for thought for the future.

 

[day_trippr]

Unless one can find a bag made from a material with very high resistance to oxygen I expect the high purity CO2 goal will simply be unachievable. There will be so much surface area, most bags are quite thin, and I have not been able to find bags made of PET or EVA which might give the idea a prayer of success.

Good luck though

Cheers!

 

[Ale-75-IT]

Ok, you both convinced me to further investigate on O2 permeability, before going on.

Thanks,
Ale

 

[IslandLizard]

Unless one can find a bag made from a material with very high resistance to oxygen I expect the high purity CO2 goal will simply be unachievable. There will be so much surface area, most bags are quite thin, and I have not been able to find bags made of PET or EVA which might give the idea a prayer of success.

From the picture it looks like the OP is using the kind of material hops and food are vacuum sealed in. We know those hop and food packs stay hard over long times (years), which may prove gases (such as O2) don't pass the membrane.

Mylar is another option, even Helium can't get through, or very slowly. That may be another material to try. Not sure how easy it is to seal, though. The thick, silver hop bags I've gotten from Hops Direct were multilayer mylar. guessing 4-8 times as thick as a mylar party balloon.

 

[sibelman]

some evidence

Searching with the phrase "gas permeability food storage bags" produced various hits. Here's one.

This other one might be better. It might be sensible to just choose a bag that holds food intended for a long shelf life.

Cheers!

 

[day_trippr]

fwiw, I did about 20 minutes worth of investigation wrt metallized mylar bags and a couple other materials and every one of the sellers also sells oxygen scavenging packets that are recommended to be inserted in the bags before filling with whatever wants to be O2-free.

I did not find PET or EVA bags. I was hoping they're out there but no joy...

Cheers!

 

[Bassman2003]

I have a $25 little vacuum pump that can hit 28 PSI that I use for pressure fermentation starting/head pressure. It has two barbs, one in and one out. I know this is under 3 bar, but what if you could increase your storage volume? Something like a 10 gallon keg at 3 bar would hold quite a lot of CO2.

 

[sibelman]

they're out there

To paraphrase Fox Mulder, the bags are out there.. Maybe Ale could just re-use a bag that, e. g., cashews came in...

Maybe the need for the O2 scavenging could be avoided by venting/discarding one 5 gal. batch worth of gas, which @doug293cz indicates would effectively purge a (much larger) 5 gal. corny.

Speaking of which, I confess affection for the two-keg design mentioned above, but Ale clearly wants to try the bag thing.
And it's clearly possible to fall into an absolutist mode re our beloved and hated O2. A well-chosen bag could work very well.

 

[DuncB]

A well-chosen bag could work very well.

Especially if made of thick metal!

 

[Ale-75-IT]

I've done some research here and there, mostly on some manufacturer's homepage.

It's very difficult to have a technical datasheet for a single product... so It could be quite difficult to know diffusion/resistance data of the bag you're choosing, at O2.

What I have learned is that an aluminum coating reduces the O2 permeability significantly against plastic bags without alu, but how much is not exactly clear to me: best value I've seen is 3cc (cm3) of O2 in 24 hours diffused through a m2 of surface (which is a very huge diffusion!!!). A year ago my homebrew shop "upgraded" their malt and hop packages from clear to "silver" ones.... this empirically supports the idea that I need this type of bag to preserve from O2.


The only sensible upgrade I can think of at this time is to ask the shop to sell me some silver bags.


I also need them to replace the bags I put inside my Corny kegs, I must admit, with very little knowledge of the consequences.... When kegs are quite empty I have had the impression to get lower carbonated beer (due to CO2 exitin the bag?) and a loss of flavor and possibly oxidation (due to O2 gettin in?). I also noticed that the Corny was clean inside but had a bad vinegar smell (again due to anything goin' out of bag because of its permeability?... outside the bag the "ambient" isn't sanitized, because there's no need to do it).


Damn!!! the whole project is slowing down thanks to the increase in knowledge!

Thank you and bye,
Ale

 

[IslandLizard]

Damn!!! the whole project is slowing down thanks to the increase in knowledge!

Thank you and bye,
Ale

You're not leaving us, are you?
Discussions like these are the best to gather input and ideas from a group with an interest in the matter, aka, brainstorming.

Not sure if moisture was addressed, but I can think of reasons why you wouldn't want "beer vapor" ending up in your (final) CO2 holding keg.

 

[Ale-75-IT]

these are the bags my shop utilizes now.

 

[Bassman2003]

When you say "store for further usage", what is your goal for the CO2? Just carbonate and serve? Is so, how many kegs do you need to carbonate/serve from?

Basically, how much CO2 are you looking to capture and store?

 

[IslandLizard]

these are the bags my shop utilizes now.

Yeah, those look like the multi-layer mylar* bags I was referring to in #42, as used by Hops Direct, here in the US.

* At least I hope all the plastic used in the bags is indeed mylar.

 

[Ale-75-IT]

When you say "store for further usage", what is your goal for the CO2? Just carbonate and serve? Is so, how many kegs do you need to carbonate/serve from?

Basically, how much CO2 are you looking to capture and store?

Bassman2003: please forget what I've said before, because I've had new inputs so I'll have to revise my project....

Before making a prediction on how many liters I'll need or on the purpose (carbonation or transfer?), I need to better understand the risk of diffusion of O2 in the system.

This i s crucial. When I face this I will go further implementing the system.

Ty and bye,

Ale

 

[Ale-75-IT]

You're not leaving us, are you?
Discussions like these are the best to gather input and ideas from a group with an interest in the matter, aka, brainstorming....

No I think I won't, even if I have a big linguistic limitation and therefore posting costs me a bit: I have to get a mental image of what I want to say in English, then I have to try to write it and finally (if I'm not particularly pissed off and so I don't care) I want to feed it to google translate to see if there are many differences compared to what I would write.

A good pain in the ass.
But while it's worth it...

Tx and bye,
Ale

 

[Bassman2003]

Bassman2003: please forget what I've said before, because I've had new inputs so I'll have to revise my project....

Before making a prediction on how many liters I'll need or on the purpose (carbonation or transfer?), I need to better understand the risk of diffusion of O2 in the system.

This i s crucial. When I face this I will go further implementing the system.

Ty and bye,

Ale

Just trying to find out your end goal. Why are you attempting the project? - Cheap CO2 or pure CO2?

 

[Ale-75-IT]

Just trying to find out your end goal. Why are you attempting the project? - Cheap CO2 or pure CO2?

Bassman2003: this is a bit of a difficult question for me!
I think what drives me is the passion for DIY, which I inherited from my father. And perhaps even earlier by my grandfather, who made his own wine (all year round), cultivating the vines; he also raised hens, rabbits, chinchillas, for food and to monetize.
It's been forty years and things have changed a lot and I don't want to be pathetic!

I'd like to be as self-sufficient as possible and produce what I need by myself... that's why I grow hops and try to recycle the yeasts between one brew and another, sometime with evident under-pitching, other times with great results. I'm not interested in winning a homebrew contest, but in producing a decent beer for family use: "homemade"... like grandfather's wine which they say (I was too young), was decent.

So could my goal be "self-produced CO2 with some trade-offs"?

Bye
Ale.

 

[DuncB]

Bassman2003: this is a bit of a difficult question for me!
I think what drives me is the passion for DIY, which I inherited from my father. And perhaps even earlier by my grandfather, who made his own wine (all year round), cultivating the vines; he also raised hens, rabbits, chinchillas, for food and to monetize.
It's been forty years and things have changed a lot and I don't want to be pathetic!

I'd like to be as self-sufficient as possible and produce what I need by myself... that's why I grow hops and try to recycle the yeasts between one brew and another, sometime with evident under-pitching, other times with great results. I'm not interested in winning a homebrew contest, but in producing a decent beer for family use: "homemade"... like grandfather's wine which they say (I was too young), was decent.

So could my goal be "self-produced CO2 with some trade-offs"?

Bye
Ale.

I feel another pressure ferment safe vessel corny or fermzilla, feed a CO2 engine with sugar wash and nutrient, you can closed top this up and use this to run your keg setup. Easily run it at 15 to 20 psi, inline reg to your kegs. With beer carbonated by spunding this should easily keep you going.
Vapours / odours could be removed by inline carbon filter or activated charcoal in the fermenter.
25 litres at 20 psi with the regulator should push a lot of pints. @doug293cz I think did the maths on this perhaps in thread already mentioned above or elsewhere.

 

[Bassman2003]

Thanks. It is a nice goal. It is difficult to replace a CO2 tank as it holds so much CO2 due to the very high pressure. You could try to naturally carbonate and use a 2nd keg to capture the CO2 at the same pressure. But the problem will be (as you know) that the CO2 pressure will go down as you serve the beer. This is why your were thinking of a bag and a pump. But I think that will be difficult to get working properly. Not just oxygen ingress but knowing when and how long to turn on the pump etc... will be tricky. Run the pump too long and it might start sucking out of the fermenter. At 6-7 bar that will do some serious damage in the wrong situation.

Not sure how to make this work without large holding containers and/or an expensive pump setup.

 

[Bobby_M]

Your initial design is OK but has some flaws. Here’s my improvement on it. Use two (2) corney kegs. Run the CO2 out of the fermenter to the first keg. Out of that keg to the compressor then through a charcoal filter to the second keg. You will have to build an activation circuit using a barometric sensor that can be placed inline with the first keg to turn on the compressor. The sensors are cheap: https://a.co/d/g9sAkIB
But like I mentioned, you will need to build the controller using an Arduino or similar device. And is course, you will need to purge the system before collecting CO2.
And in case your brew makes, too much CO2, just keep a third keg handy to switch out to handle the overflow.

No good unless you don't mind the fermenter running under pressure. In order to be worth triggering the pump that first keg would need to be under at least a few PSI and then it would have to stop before it reached atmospheric otherwise the lid would be drawn down and leak air in. The pump would need to be hooked to a pair of accurate pressure switches and then all your fermenters would be under some level of pressure.

 

[Ale-75-IT]

this is what I was thinking to try before getting stuck with the O2 problem above....

A potentiometer who can detect bag height and activate/de-activate compressor.

I was quite ready to start experimenting with some simple esp-32 code... but I got stuck with the O2 and bag question...


damn!