# CO2 dissolution rate vs. saturation etc



## dmachado (20 Jan 2015)

There is something going on with my CO2 system I'd like to see explained f possible.

I have set up a system which uses DIY molasses and yeast CO2 bottles, 6 of them, controlled by a solenoid. The system shuts off on lights out, but of course the yeast keeps producing CO2.

The molasses fermentation is very strong, here’s a photo:




 

I managed to control the storage and blowoff of excessive pressure, and it gets up to 1 bar before lights on. The system is now tuned almost to perfection.

To control the bursts of CO2, I am using a small reactor like this one, but without the bioballs:






CO2 is injected from the top, water is injected from the top side by a powerhead at 600l/h, and exits from the bottom side, only very few tiny bubbles can be seen here and there.

The interval timer opens and closes the solenoid, dosing the CO2, almost filling the reactor each time, without losses and no burping to the surface. 

I observed that in the first fillings of CO2, the dissolution is very very fast, maybe 200ml of CO2 in a matter of seconds.

As the photoperiod advances, the CO2 system pressure drops, of course, and less CO2 is injected each time the interval timer opens the solenoid (about 1 second every 3 minutes).

My question: there is a buildup of gas in the reactor, lets say 50-100ml, that seems to be more difficult to dissolve than the first "fixes" on lights on. This gas burps away when the powerhead shuts off.

I estimated the number of pulses/opening the solenoid, and a decreasing volume from 200ml down to 10ml on the last pulse, and estimated a daily input of 15-20 liters of CO2 (about 30-40g of CO2?). For 300ml down to 20ml it would amount to 25 liters/50g of CO2.

I don't think I am reaching any kind of saturation using this method, maybe the gas in the reactor is not 100% CO2?

What may be that gas that remains undissolved in the reactor?

I hope I explained this clearly and would love to hear opinions on this.

Thank you.


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## Paulo Soares (20 Jan 2015)

Hi DMachado, 
Can i politely ask you something?

Why? Wouldn´t it be better a FE and a regulator with solenoid? Why complicate that much and the risks envolved? 
Even... How can you be shure of what you are injecting? tough..i don´t believe that sugar with ferment and bicarbonate made Co2.. 

And so many other issues..
But i´m gonna follow this thread. Hope to hear from others. 

best compliments.


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## parotet (20 Jan 2015)

Sorry to say that but it seems a lot of headache to be a DIY yeast based system... reactor, solenoid, powerheads. Too much equipment compared with traditional DIY systems. I agree with Paulo that it should be easier to buy a second hand FE and regulator for a few bucks (you've done part of the investment). Not only easier but better for your tank. With a DIY system you won't probably asphyxiate your fish but you will find lots of problem, being the first one the lack of a constant CO2 supply which IME is the worst thing about DIY CO2 systems (BBA will be the first sign) (another one could be to reach the desired concentration of CO2 especially if you are going to increase your lighting now that you are enriching your tank). The other one I would be quite afraid is this solenoid on a CO2 system that probably cannot hold the pressure, resulting in an accident. Nothing really dangerous but I read in a local forum from someone that had to paint all the living room... and that's quite expensive at the end. 

Jordi


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## NC10 (20 Jan 2015)

Paulo Soares said:


> How can you be shure of what you are injecting? tough..i don´t believe that sugar with ferment and bicarbonate made Co2..



Sugar and yeast = Co2 (& ethanol)


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## dmachado (20 Jan 2015)

Olá Paulo!

I just don't want to use pressurized vessels inside the house. The risks are much higher with a FE than with my setup, believe me. And the control of a DIY setup has become a personal challenge.

I don't use bicarbonate. I am fermenting molasses (melaço de cana) so the byproduct is 100% sure CO2 and alcohol. And it runs great, plus I get to tinker a lot and tune up recipes, etc etc.

It works the same way as with sugar, just not as acessible to yeast, and costs about 1/4 of table sugar. 

Um abraço.


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## dmachado (20 Jan 2015)

parotet said:


> Sorry to say that but it seems a lot of headache to be a DIY yeast based system... reactor, solenoid, powerheads. Too much equipment compared with traditional DIY systems. I agree with Paulo that it should be easier to buy a second hand FE and regulator for a few bucks (you've done part of the investment). Not only easier but better for your tank. With a DIY system you won't probably asphyxiate your fish but you will find lots of problem, being the first one the lack of a constant CO2 supply which IME is the worst thing about DIY CO2 systems (BBA will be the first sign) (another one could be to reach the desired concentration of CO2 especially if you are going to increase your lighting now that you are enriching your tank). The other one I would be quite afraid is this solenoid on a CO2 system that probably cannot hold the pressure, resulting in an accident. Nothing really dangerous but I read in a local forum from someone that had to paint all the living room... and that's quite expensive at the end.
> 
> Jordi



Hi Jordi, I have a relief valve on a 5L pressure sprayer which doubles as the holding tank for lights out production time - so no danger of explosion. That's the way to control this system.

The only headache was to get it to work, with a pressurized system you also have a solenoid, regulator, needle valve, diffuser or reactor, my system is simpler in fact. Now I only "cook up" a bottle once a week.

Second hand FE, 150 bar or so inside the house, "my cousin refurbished this one", that sounds really bad. That is a real danger as far as I see it. Those bottles can go through walls...

I want to understand why does the dissolution rate vary through the 8 hour light period.

Regards.


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## ian_m (20 Jan 2015)

dmachado said:


> 150 bar or so inside the house


Nope only 55bar. We have about 45 CO2 cylinders at work and in the last 15 years at my work we have had zero issues, none exploded, no one died, replaced after 8 years, again none exploded, no one died. They are CO2 fire extinguishers. I think I read there were x million in UK and only one major incident in last couple of years where an untrained operator attempted to incorrectly refill a CO2 cylinder.



dmachado said:


> Those bottles can go through walls...


You are thinking of diving cylinders as per Myth Busters. Not FE's.


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## dmachado (20 Jan 2015)

Ok I may have exaggerated a bit...

Anyway, I am sticking with DIY. Maybe I'll post a video of the system in action.

Is the "stubborn gas" in the reactor CO2 and is this related to any "saturation" in the water?...


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## ian_m (20 Jan 2015)

dmachado said:


> Is the "stubborn gas" in the reactor CO2 and is this related to any "saturation" in the water?...


Most likely air so only choice is to bleed it from your system whenever it appears. If CO2 it would dissolve over couple of hours as I absolutely guarantee your water is not saturated with CO2 as you are DIY yeasting.


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## dmachado (20 Jan 2015)

Well, a bit of air will enter the system when I change one bottle.  So it would mix with the CO2 and stay undissolved at the reactor.

So the burp out of the reactor through the powerhead on lights off should be mainly air, not CO2... that's it.

I have to workout a way to prevent or minimize that, but it's no big deal.

Thanks!

I'll post a photo of the system tonight.


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## ian_m (20 Jan 2015)

dmachado said:


> estimated a daily input of 15-20 liters of CO2 (about 30-40g of CO2?).


Something must be very inefficient somewhere or you have a monster tank or something miscalculated. I get through about 15gr a day from a 2Kg FE in 180litres and have a bordering on yellow drop checker.


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## EnderUK (21 Jan 2015)

I'm impressed if no one else is.


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## ian_m (21 Jan 2015)

If you insist on using DIY yeast couple of things I read about greatly improve it.

1. Vent CO2 at night, you need an extra solenoid to this.
2. Put all your bottles in a heated bucket of water (simple 100W aquarium heater) that way your CO2 rate will not vary between winter and summer, can turn heater off at night.
3. Make sure aquarium heater does not touch the bucket above else you will flood the lounge...
4. Make sure you have a "yeast trap" between fermentation tanks and aquarium. Yeast in the tank will kill everything.
5. Nobody has yet succeeded in making 100% seal between fermentation bottle top and CO2 tubing. Silicone is not the answer, it will eventually leak.
6. Molasses for animal feed works just as well and is very cheap, but comes in 10litre bottles.
7. Quite a few people have suffered exploding bottles, including the guy who had to repaint all his lounge at request of SWMBO after an incident.


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## dmachado (21 Jan 2015)

ian_m said:


> Something must be very inefficient somewhere or you have a monster tank or something miscalculated. I get through about 15gr a day from a 2Kg FE in 180litres and have a bordering on yellow drop checker.



The reactor is very efficient, I clearly miscalculated, I used a linear function and I am pretty sure it should be more like a step function, amounting to a lot less CO2. Those 15g/day for a 180 liter are a valuable information for me, thank you.

Here's the photo of the reactor "reacting":


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## dmachado (21 Jan 2015)

ian_m said:


> If you insist on using DIY yeast couple of things I read about greatly improve it.
> 
> 1. Vent CO2 at night, you need an extra solenoid to this.
> 2. Put all your bottles in a heated bucket of water (simple 100W aquarium heater) that way your CO2 rate will not vary between winter and summer, can turn heater off at night.
> ...



Hi Ian,

Thank you for you detailed advice, I have it all checked:

*1*. the safety valve at the pressure sprayer does that if the pressure gets too high
*2*. no need - my cabinet's inside temperature is pretty stable all year
*3*. no need
*4*. DIY yeast 101 - always the first part of the system
*5*. if you have one of these (in my case 7 of these) you have a perfect seal - remember my system goes up to 1 bar:



*6*. I bought 80kg of it last summer  - "yeast is animals!"
*7*. no explosion risk as I am pressurizing the 5 liter pressure sprayer with a safety valve, and the pressure rises a lot less than in a 1 liter volume

I am convinced I have it all covered... I really am.

Thanks for all the input you are giving!


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## NC10 (21 Jan 2015)

ian_m said:


> 5. Nobody has yet succeeded in making 100% seal between fermentation bottle top and CO2 tubing. Silicone is not the answer, it will eventually leak.



I'm not sure what the OP is using, but when I was looking in to DIY I had one of >these< on my shopping list.

Edit: lol Nevermind, too late


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## ian_m (21 Jan 2015)

Blast from the past....
http://www.thekrib.com/Plants/CO2/yeast-disaster.html


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## dmachado (21 Jan 2015)

Been there, I had a minor incident back in 95 with a 5 liter bottle, oh boy... the smell... 

Why do you think it took me so long to get this right?


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## Mr. Teapot (21 Jan 2015)

EnderUK said:


> I'm impressed if no one else is.


Me too! Imagine the booze you could produce as a by-product!

There was a thread over at the Barr Report discussing undissolved gas in reactors that may be interesting to the OP:
http://www.barrreport.com/forum/bar...hat-the-gas-is-inside-the-co2-reactor-chamber


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## dmachado (21 Jan 2015)

Great thread, there seems to be a build up of gas in many reactors... 

In my case, with small amounts of air entering the system when I change one of the bottles, about 75% of that air would be N2, and at the end of the light period it would be mostly that gas that gets burped from the powerhead side. No waste of CO2!

Thanks!


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## dmachado (22 Jan 2015)

Here's a photo of the system.




 
_Entangled _is the word you are looking for...

My main problem now will be getting regular CO2 production from it.


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## ian_m (22 Jan 2015)

dmachado said:


> if you have one of these (in my case 7 of these) you have a perfect seal - remember my system goes up to 1 bar:





Fantastic, these weren't around years ago when I first started investigating CO2, everyone eventually had bottle sealing issues due to silicone not sticking to bottle tops and CO2 tubing.


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## EnderUK (22 Jan 2015)

Have you tried jelly?


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## ian_m (22 Jan 2015)

I seem to remember jelly, sugar, yeast and bicarbonate of soda gave longest regular rate of CO2. Bicarb necessary as fermentation proceeds mixture becomes acidic killing the yeast.


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## parotet (24 Jan 2015)

I guess you've already considered what I'm going to ask, but why not using empty FE cylinders for doing what you do? If you really want to keep on using a yeast system I think it has plenty of advantages: can hold more pressure, more volume, no leaks if using regulators and other fittings, more durability...

Jordi


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## dmachado (27 Jan 2015)

parotet said:


> I guess you've already considered what I'm going to ask, but why not using empty FE cylinders for doing what you do? If you really want to keep on using a yeast system I think it has plenty of advantages: can hold more pressure, more volume, no leaks if using regulators and other fittings, more durability...
> 
> Jordi



 Hi Jordi, the main reason is that you cannot see inside the FE, so you have no clue about the production rate of each botttle, and when is time to mix a new batch. 

Also, PET bottles can withstand about 100psi if I'm not mistaken, close to 7 bar, no way this gets there!

Regards.


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## parotet (27 Jan 2015)

Yep, it makes sense. The advantage i can see is that if you use FE there is plenty of equipment that is leak proof (well, let's say that is easier to be leak proof).

Jordi


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## ian_m (27 Jan 2015)

parotet said:


> I guess you've already considered what I'm going to ask, but why not using empty FE cylinders for doing what you do? If you really want to keep on using a yeast system I think it has plenty of advantages: can hold more pressure, more volume, no leaks if using regulators and other fittings, more durability...
> 
> Jordi


and it will corrode through eventually giving a yeasty floor...


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