trying to achieve a cheap CO2 storage system

[Ale-75-IT]

I won't dwell because I don't write well in English.

What I want to achieve is to recycle CO2 from fermentation, compress it at low pressure because I haven't the skill lo liquefy it (let's say 6-7 bar), and store for further usage.
I intend to use cheap materials like pet bottles, fast compressed air junctions, a 12v "oil less" compressor (air smells a little so not truly oilless i fear) and a PC power source.

The core of the system is an heat sealed plastic food bag which takes an input from my fermzilla spunding valve (In the photo the CO2 cylinder simulates a fermzilla). Inside the bag there's the little 12v compressor that push co2 outside the bag into the storage system.

After the gas comes out of the bag under pressure, It will pass throug a non-return valve, a pressure gauge, a tank (PET bottles), a faucet (gas outlet).

Initial tests show that the system is airtight (but it was no easy task to make airtight caps due to washers too soft and wavy caps).
The next step will be to add some controls to detect when the bag gets full and the compressor needs to be turned on. I'm thinking of a potentiometer that can sense the width of the bag and activate (via an esp32) the compressor until the bag returns to its previous state.

Any help/thoughts will be appreciated, bye,

Ale

 

[AlexKay]

My understanding is that commercial CO2 capture systems have a scrubbing step. Fermentation (especially early fermentation) produces a number of flavor-active compounds (e.g., H2S) that you really don't want to re-introduce to another batch of beer. It's possible that all you'd need is activated carbon in-line, and could repurpose a water filter. (The filter might help with any volatiles coming off of your compressor, as well.) I'd consider experimenting along those lines if you find yourself getting flavors you don't want.

 

[Ale-75-IT]

thanks AlexKay,
in fact I'm partially unaware of the possible consequences of the project...
What I wonder is that when fermenting isobaric (and therefore the beer is partially carbonated thanks to the gases naturally produced) or when sugar is introduced into bottles to carbonate the beer .... the situation could be similar.
If I'm wrong, a possible option would be to use the CO2 stored in this way for decanting, so there would be minimal contact with the beer.
Thank you for your advice,
Ale

 

[Ale-75-IT]

Another option could be to avoid storing early fermentation active compounds?
I'm very interested in digging into this topic which I'm unaware of.

Thank you so much!

 

[DuncB]

You'd find it a lot easier to store the gas in an empty keg, then you'd get 20 litres at up to 25psi, connections would be easy as ball lock connectors and spunding valve could be used.

What are you going to use this gas for?

@doug293cz in another thread explained at length that the volumes capturable with this aren't that useful even in a bigger container.
Your plastic bag will be letting air through it so you are going to be storing in your pet bottles a mix of co2 and air. Diffusion starts immediately.

The gas in a keg could be used to replace losses in a low pressure system such as over a cask ale via a demand valve. But I doubt you are making cask ale given your pressure fermenting.

A " bio reactor " in a fermenter or keg with yeast sugar and water is also another way to "make" CO2 for serving pressure.

 

[Ale-75-IT]

I like to complicate my life with DIY so I'm not interested in simple solutions.
Storing Co2 at isobaric fermentation pressures does not suit my purpose. What I'd like to have is a more pressurized CO2 for decanting or carbonating beers.
The sealed food grade plastic bag is absolutely airtight (thanks to kegland seams) and can't get O2 inside once purged....

Thanks and bye,
Ale

 

[DuncB]

This thread has a lot of info and was the one I was thinking of.

https://www.homebrewtalk.com/threads/use-a-keg-as-a-co2-vessel.698904/#post-9239161

 

[DuncB]

I like to complicate my life with DIY so I don't care about non-easy solutions.
Storing Co2 at isobaric fermentation pressures doesn't meet my purpose. What I would like to have is higher pressurized CO2 to do decanting or to carbonate beers.
The food grade sealed plastic bag is absolutely air tight (thanks to kegland juinctions) and no O2 can gen inside once purged....

thanks and bye,
Ale

Well you can ferment up to about 30 psi in a pressure fermenter or higher so that wouldn't be isobaric.

The join on your bag might be "airtight" .

The trouble is that the bag is permeable, it can hold liquid fine but gas can just wander straight across a plastic bag and exchange. The tubing you are using isn't EVA barrier tubing either so there will be exchange across your tubing as well.

 

[Ale-75-IT]

Ok the bag could be permeable but at which "speed"? They're used to preserve food from gases.... I don't think O2 will enter at high rate...
Same thought on tubing, they're used to preserve compressed air....

Tomorrow I'm reading the topic you posted.
Thank you and good nite,
Ale

 

[Ale-75-IT]

I read that thread but my goal/system is different.

What I want to achieve is to rise CO2 pressure up to 80-100 psi (6-7 bar) inside PET bottles. I tested them individually and they resist 8 bar = 116 psi, what I really don't know is if they can resist for a long time. If not, I'll have planted a cluster bomb in the basement!

If all goes as planned, with about 11 liters (3 gal) of storage capacity, assuming 7 bar (100 psi) storage pressure inside the bottles, I can decant about 50 liters (13 gal) from a Fermzilla loaded at 1.5 bar (22 psi), in my serving kegs.

If we are talking about decanting I do not expect unpleasant flavors due to potentially unwanted stored gases, due to the short contact time with the beer.

Forced carbonation is another story, but perhaps this could add additional DESIRED flavors (all those wonderful volatile hop aromas you dispense into your basement air when you let the brewing CO2 go).

Bye,
Ale

 

[Bassman2003]

I think I see what you want - a source of pure CO2 to force carbonate or dispense your beer. What I think is your best route is what has been mentioned - use a keg. You will get plenty of CO2 in a cornie and it will be safer as they are rated for higher pressure. Plus if you add a Bune-N keg seal it will be pretty much O2 free. EVA barrier tubing for the connections and you are set.

No need to reinvent the wheel so to speak!

But, how are you going to get up to 6-7 bar for the gas input? Are you going to run a fermentation at these pressures? The yeast will explode. Cramming the CO2 in at a higher pressure than 2 bar is going to be your challenge.

 

[Ale-75-IT]

Hi Bassman2003.

I inflate a plastic bag with CO2 at low or no pressure at all (it enters slowly as the fermenter produces it) and periodically pump it out of the bag with a little 12v air compressor. It can manage 7-8 bars.

Bye,
Ale

 

[Bassman2003]

How does that work? If the air compressor is storing air and forcing it back out, how do you move the CO2 without introducing air?

 

[mac_1103]

I inflate a plastic bag with CO2 at low or no pressure at all (it enters slowly as the fermenter produces it) and periodically pump it out of the bag with a little 12v air compressor. It can manage 7-8 bars.

So why not just pump it into a keg? I'm not too worried about your PET bottles exploding, but I would expect some leaks to develop in all of those connections over time.

 

[Ale-75-IT]

How does that work? If the air compressor is storing air and forcing it back out, how do you move the CO2 without introducing air?

Basically the scheme is that.

So why not just pump it into a keg? I'm not too worried about your PET bottles exploding, but I would expect some leaks to develop in all of those connections over time.

Pumping into a keg could be an option, but dunno if a cornelius can tolerate 6-7 bars (you should remove safety valve or change it with an adequate one)...
And yes I've a concern about possible leaks too... I'll look for a cheap cylinder...

This setup is an "early beta".... looking for improvement and to see if it's worth to go on.

Bye,
Ale

 

[mac_1103]

Corny kegs are rated for 130 PSI which is almost 9 bar. Many PRVs are designed to pop at much lower pressures so you do need to make sure you have an appropriate one.

 

[Bassman2003]

Thanks. So you have the pump inside the CO2 storage bag. This bag seems to be the most important part of the setup. Keeping it sealed (electrical cord etc...) is key. Pumping into a keg and storing is easy. The bag might need to be quite large for this to be worthwhile.

 

[Deadalus]

How about a keg or a sealed bucket for your pump instead of the bag. Various sizes are available.

 

[Bassman2003]

It might be a challenge to get the pump bag to be purged of oxygen to start. A bag makes this easier because you can squeeze it down while pumping out.

 

[Deadalus]

It might be a challenge to get the pump bag to be purged of oxygen to start. A bag makes this easier because you can squeeze it down while pumping out.

I considered needing to purge but from what I have read the volume generated off a five gallon batch is quite a bit. I was going to suggest a small keg intiially but the OP mentioned cost and may not have any. I just bought food grade 2 gallon buckets for $5 each with lids $2-3 though. The bag picture seemed a little flimsy.

They do make water bladders with big zipper openings but probably upwards of $20. Not sure what material it is but a Platypus Big Zip is the brand name I am thinking of. I thnk they are usually 2-3 liters.

 

[Ale-75-IT]

Must thank you all because you gave me a lot of suggestions for my DIY obession...

Thanks. So you have the pump inside the CO2 storage bag. This bag seems to be the most important part of the setup. Keeping it sealed (electrical cord etc...) is key. Pumping into a keg and storing is easy. The bag might need to be quite large for this to be worthwhile.

Having a big bag maybe could be a trick to skip the "control unit" (esp32 + any sort of sensor capable of detecting the bag state): I would manually turn on/off the compressor when the bag gets full. Dunno how many litres/gal will a 23l (6 gal) batch of IPA output at about 18 C° (64 F°) in a certain amount of time... but can research a bit ('cause I sleep 7 hours and go to work 8-10 hours a day ).

How about a keg or a sealed bucket for your pump instead of the bag. Various sizes are available.

A keg/bucket will add extra complications on detecting when the pressure rises to a level you have to turn on/off the pump: I think I'll need a pressure sensor and I don't ever used one so I'm not comfortable with it... and it won't be suitable if you plug in a classical 23l plastic fermenter, wich isn't capable of holding pressure. If the cost remains under a hundred dollars/euros it won't be a big issue, but I'd like to stay as cheap as possible cause a 2 kg CO2 refill is about 13€ here in Italy .

Corny kegs are rated for 130 PSI which is almost 9 bar. Many PRVs are designed to pop at much lower pressures so you do need to make sure you have an appropriate one.

I found this old Corny in my basement, never used it because of beer ball lock stuck (was unable to screw out it and clean/replace washers).
It's a Pepsi-Cola keg dated 1989... and it says "maximum serving pressure 4.9 bars"!

Tomorrow I'll try to inflate it to 7-8 bars in the garden (staying at an adeguate distance ) to mostly see if it can keep pressure.
If it explodes the neighborhood will respect me more in the future .
But, hey, it says:

I have to trust!
HaHaHAHA

Bye and thanks,
ALe

 

[Deadalus]

What does the keg top look like? The pressure release valve in the keg lid should open at 4.9 bar. It's an emergency release. The neighbors may not appreciate the hissing sound!

Are you saying you couldn't get the posts off? We could most likely help fix your keg.

I also have no idea how much a pressure sensor might cost. A check valve (one way valve) between the fermentation vessel and the pump collection container would prevent over pressurizing the plastic fermentation vessel. You could put a timer on the pump if it fits in the keg, the keg has an emergency pressure release as mentioned. Turn it on periodically. Initially I don't think you would need the pump. The pressures would equalize but steadily increase I think. Check valves have a cracking pressure I believe it's called, the mininum pressure to open the valve. You wouldn't want that too high for the one I suggested after the FV. Just brainstorming here though, could be other options.

 

[mac_1103]

Dunno how many litres/gal will a 23l (6 gal) batch of IPA output at about 18 C° (64 F°) in a certain amount of time...

You can find plenty of discussion of that on this forum. For example, doug293cz's epic post on CO2 generation. 20 L of 1.050 wort produces 878 g of CO2 which is about 439 L.

I'd like to stay as cheap as possible cause a 2 kg CO2 refill is about 13€ here in Italy

That's probably cheaper than what most folks pay in the US.

 

[Ale-75-IT]

Ok, I'm ready to test my rusty Corny in the garden... Hope the cable will be long enough .

Bye,
Ale

 

[Ale-75-IT]

Good old Pepsi Keg!

It can hold 7 bar without air leaks (tested with that orange liquid dish soap).

Initially It produced very few bubbles on the tire connector, because it was not tight (it belongs to another project, I was trying to put a food grade plastic bag inside the Corny; I succeeded but with another method).

I think I can trash the bottles and do further investigation with the bag and the electronics to drive the compressor, now that I have a serious bomb to plant in the basement!

Thank you all,

Ale

 

[beren]

A 20 pound CO2 tank is only like $45 to fill and that will dispense 35 or 40 kegs and you don’t have to do anything

 

[mac_1103]

A 20 pound CO2 tank is only like $45 to fill and that will dispense 35 or 40 kegs and you don’t have to do anything

Except buy an empty 20 pound CO2 tank.

 

[beren]

I got one cheap. Some places may let you upgrade sizes like maybe Airgas

 

[sibelman]

OP says

I like to complicate my life with DIY

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.

 

[DuncB]

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

 

[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!