# Why CO2 from fermentation?



## HeyPK (Jan 23, 2004)

CO2 from yeast fermentation is a time-honored method whose origins as a source for aquarium plants go back at least to the 1940's. But you don't get very much CO2. From a molecule of glucose (6 carbons) you get two CO2 molecules and 2 alcohol molecules (4 carbons). You only get 1/3 of the carbon in the form you want, and the other 2/3 accumulates and stops fermentation when it gets to around 15%. You have a lot of waste and you have to set up new cultures every couple of weeks. 

In contrast, aerobic respiration of glucose converts all the carbon in glucose to CO2. You get 6 molecules of CO2 and no toxic byproducts that inhibit the organisms respiring the glucose., Starch is a polymer of glucose and is easily broken down to glucose and respired by soil organisms. 

What if you had some soil in a bottle and added a tablespoon or so of oatmeal (Oatmeal is starch, mostly) and pumped some air through the soil to an airstone in an aquarium? 

I have been thinking about trying to design a DIY aerobic CO2 producer.


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## Millipede (Feb 11, 2009)

HeyPK said:


> In contrast, aerobic respiration of glucose converts all the carbon in glucose to CO2. You get 6 molecules of CO2 and no toxic byproducts that inhibit the organisms respiring the glucose


except for the co2 itself.


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## HeyPK (Jan 23, 2004)

Lack of O2 as well as high CO2 will stop respiration, but, if you pump air through the soil and into the tank, you take care of that problem.


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## Tikulila (Feb 18, 2011)

If we would take a bit of soil, add to is some water with sugar and yeat, for a start, it might work.
As for yeast, we would need soil, i would add a bell (like the CO2 bell), for O2, so there wont be too much escape, but enough for the yeast, underground. Also it will work better with mud for it will be harded for the O2 to escape ad faster to dissolve. 
Then after the 1st dose of sugar, we start adding some oatmeal, once a week.

Might work, I have warm climate here, maybe someone should try it also in cold climate.

In addition the are the types of soil. can anyone add to this?


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## HeyPK (Jan 23, 2004)

It would be better to add starch to the soil than sugar, which dissolves and makes a hypertonic solution which can be too concentrated for organisms to live in. You don't have to add yeast, There are plenty of soil organisms, fungi and bacteria that can break down the starch. Oatmeal flakes are mostly starch. They will become covered with mold in two days and be broken down mostly in two weeks. Any organic matter in soil will be eventually be consumed by soil organisms and its carbon converted to CO2. Oatmeal flakes go pretty fast. (Maybe some plastics we make are an exception; on the other hand maybe they will eventually be consumed given lots of time.) Naturally occurring organic matter made by living things gets consumed.

Any kind of topsoil should be fine unless it was sterilized.

Instead of oatmeal flakes added every several weeks, one could add dead leaves. It takes a lot longer for dead leaves to be broken down, and so the CO2 production would be a lot slower, but would be over a longer period of time. One could compensate by having a larger volume of soil with dead leaves. Maybe a couple of cubic feet with air being moved through slowly, would keep a 15 gallon tank supplied with CO2 for 6 months before more dead leaves had to be added. Since oatmeal flakes are broken down much more rapidly, one could get by with a smaller volume of soil and adding more oatmeal every two weeks.


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## Tex Gal (Nov 1, 2007)

Has anyone experimented with this? It sounds interesting....


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## Tikulila (Feb 18, 2011)

I will try it with the soil in my garden, which is the main soil here, clay based. My only concern is that oxygen wont get to all the soil, what do you suggest? Also, we need to make sure all organisms in there are safe, I dont want Methane in my aquarium, and im guessing you wont too. That is the only danger, but my guess is it can be done.


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## HeyPK (Jan 23, 2004)

Diffusion through air is something like a hundred thousand times faster than it is through water. As long as your little compost pile is damp, but not waterlogged, O2 should get to all parts of it until all the O2 is exhausted everywhere in the container. The container has to be airtight with an air pump that pumps air into it and an airline leading out to the aquarium. I know they make pumps that move small amounts of air by rolling steel bearings along a length of flexible air tubing (I think they are called peristalsis pumps), but these pumps are expensive. I am thinking more of using a regular aquarium air pump but only turning it on for a minute or two several times a day. One can buy some nice, small, relatively cheap (16 to 19 dollar) electric timers that can be set to do that.


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## Tikulila (Feb 18, 2011)

OR, like i might do, blow some air through it every morning and afternoon, with the addition of a check valve, which will be needed anyway. although i think i would rather buy an airpump. now i only need to find a place for a check valve.....

also, if we do use a bell, the larger it is, the more air it can hold for us.

now i remember, we learnt about the diffusion 2 years agoin science... how could i forget...:|


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## HeyPK (Jan 23, 2004)

I was thinking that a check valve would be needed, too, and I spent a lot of time looking up plastic check valves on Google. But, I found that the air pump, itself, acts as a check valve. When it is turned off it does not allow back flow of air, but allows air to be sucked through it in a forward direction very easily. How fortuitous! It is beginning to look as though this set-up can be made using easily-obtained materials.


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## Tikulila (Feb 18, 2011)

Well, that helps, I guess its time to go get some tubing and a cheap Pump. Only that now I need to find an accurate Timer.

might be the next CO2 generation.


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## HeyPK (Jan 23, 2004)

The General Electric plug-in 7-day digital timer looks like a good one. It has 20 separate on-off settings to the nearest minute, and each one can be daily. That should be more than enough. It also has a battery for memory if the power should fail. There are still some issues with sealing the container. I was thinking of a large rubber stopper, but now I am thinking of a rubber glove.


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## Tikulila (Feb 18, 2011)

About the timer, I live in israel, so ill get one from the local brands.

The air tight part, about which part of the bottle are you talking, the tube to the pump and bell can be seald with or silicone or loctite, it works really well for airtight.


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## HeyPK (Jan 23, 2004)

My thinking is that we want a container that has a relatively wide mouth so that we can get the soil into and out of it easily. The wrist part of the rubber glove could go around the mouth and be held on with one or more rubber bands. Cut off the tip of a finger and insert the in-going air tube which goes down to the bottom of the container. Cut off the tip of another finger for the out-going air tube. Seal the air tubes to the fingers with rubber bands. Cut the rubber bands so that they are strands, not loops, and tie them around the fingers to seal the air tubes. The rubber bands around the mouth should also be strands. When it is time to add more oatmeal, untie the rubber bands around the mouth, pull off the glove, dump out the dirt into a dish pan or something, mix in more oatmeal flakes, and put the dirt back in the container and tie on the rubber glove.

I don't know how much CO2 we are going to get from this set-up. It might be possible with a large enough volume of soil and a large enough amount of oatmeal flakes to over-do it. I think it would be best to try this out on an aquarium without fish until we know more about how this thing will work.


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## Tikulila (Feb 18, 2011)

Thats a good idea, maybe a wide container would work, like a box. 
The output will get up as it ages, so at somepoing we could just leave it without food for a week so some of it will die, making sure not to get too much, although I doubt we will need to do that.
The glove will expand under the pressure, which might also be a problem. If we use a flat box, and drill holes into the Cap, its also a possibility. I'll build a 3D diagram, so it'll be clearer.


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## HeyPK (Jan 23, 2004)

I think that these rubber gloves sold for housework in grocery stores are a lot thicker than the rubber gloves that doctors use, and they would probably not swell very much under the pressure that an air pump could produce. They are more heavy duty and are made for repeated use. 

The CO2 output from the setup would probably rise to a peak and then slowly decline, kind of like the way it does from the typical sugar fermentation set-up.


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## Tikulila (Feb 18, 2011)

That is true, welll, mine isnt going to look too good, the gloves here are yellow-blue...

ill start today a test one, its going to make a test run today, im making the earth consisting of crushed cornflakes and some claybased earth, ill see what happens. might be that we will end up with a fungal growth in there. 

lets see what happens.

ill send photos.


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## Tikulila (Feb 18, 2011)

Here are the pics, doesn't look too good, but I guess a small cabinet to put that in will finish the awful look prob. The container is only for this test run, out of the few more to come.

The specs:

The soil is clay based from the garden, not sieved or anything like that.
In the soil I mixed some crushed cereals, 2 kinds. 
The 1st kind is the simple cereal.
The 2nd is a full-grain cereal. 
Also, i put some standing up ones, to see what comes out, also from the 2 kinds.
here are the pics.




























Cereal Type #1









Cereal Type #2


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## HeyPK (Jan 23, 2004)

It looks much too wet. The cereal will ferment. The soil should be just damp with lots of air spaces. Take what you have and mix an equal amount of dry soil with it. If necessary, spread it out to dry further. There should be no visible liquid water filling in spaces between soil particles.

I will be setting up my attempt today, and will post pictures later.


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## Tikulila (Feb 18, 2011)

Don't worry, it's only the start, its dry on the bottem, it look better now, ill mix it to get it to even out, and we will see what happens tomarrow. 

I also added some self stick nylon on top, with small holes, to conserve the most heat, without obstucting the air flow. 
Optimal temp. is 37 degrees Celcius.

Waiting to see your setup.


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## Tikulila (Feb 18, 2011)

Update!

there seems to be fungul growth on the cereal. most of it is on the type #2 cereal. ill see if i can identify anything. HeyPK, did you try anything?


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## HeyPK (Jan 23, 2004)

Fungi are good. The question now, is, How much CO2 is being produced. Is it enough to be useful in a tank? 

I got involved in a lot of other aquarium work. I have bought a bunch of pumps, fluorescent tubes, timers, etc. Today, I think I can work on the aerobic set-up. Pictures will be coming.


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## Tikulila (Feb 18, 2011)

No problem,I'm not sure about CO2 output, I'll have to change part of the setup, so we would see what's coming out. Also, part of the decomposition prosses can release CO2, including other thing. the fungi is probably from this family:Saprotrophic Fungi .

Edit:
Corn grain holds about 70% carbohydrates

so here is a bit of info on it:
http://www.fao.org/ag/againfo/programmes/en/lead/toolbox/Mixed1/MS1PSR.htm
http://en.wikipedia.org/wiki/Chemical_process_of_decomposition#Carbohydrate_degradation


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## HeyPK (Jan 23, 2004)

Spent quite a bit of time on the project tonight. I found that pumping the air through the compost in the jar presents too many problems. The pressure necessary to move air through an air stone in a 29 gal keeps blowing the glove off the jar even if I tie on the glove with strong rubber bands. I am giving up on the glove idea. I think that pulling the air through the jar with the compost is the way to go. Pulling the air through should create only a very slight negative pressure.


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## HeyPK (Jan 23, 2004)

I have got the set-up that pulls air through the compost pile, and it works!!! I have a small aquarium pump and I took a small plastic bag, cut off the bottom so that it becomes a plastic tube, put the pump inside with the electric cord and the output tube going out one end and an input tube going in to the other end. I tied the bag firmly around output and input tubes with cut rubber bands. The input tube goes to the jar with the compost. The jar is a 1 gallon pickle jar about 2/3 full of soil with a half cup of oatmeal flakes mixed in. Stretched over the top of the jar I have plastic from a plastic garbage bag with two small holes, one for the tube that goes to the bottom of the soil and to the pump. The other hole is for a short tube that pulls the air in when the pump is operating. The pump is operated by a GE 7 day digital timer.

I set it all up yesterday with the tube from the pump output going into a 15 gallon aquarium that has green water, a lot of light---110 watts of compact fluorescent---and has not had any CO2 input for more than a month. While I don't have a pH meter, I am sure that that tank had become very alkaline because of the green water, the bright light and the lack of CO2 input. All the snails had died in it and a plant I put in it also died. With green water and bright light you commonly get pH values over 10.

I set the timer to pull air through the compost 15 minutes at 10 AM, 5 minutes at 12 noon, 5 minutes at 6 PM, and 5 minutes at 9 PM. After the first 15 minutes I tested the water with a bit of brom thymol blue. I got a blue-violet color that indicates the pH is 8 or higher. Can't tell a thing from that result. There may have been a lot of CO2 in the air pumped into the tank, or there may have been none. If there was a lot of CO2, it wasn't enough to get the pH down to the range of the Brom thymol blue that goes from 8 to 6

Source of picture: http://mslavenda.com/bromothymol_blue.htm 









I want away and did things and came back and took another test after the 6:00 PM injection of air. This time I got a green, with a little blue, indicating a pH of around 7. After the 9:00 PM injection it was a distinct yellow green, almost lower than I would want it in a tank. The pH was a bit lower than 6.5. This is working amazingly well. In fact, I think I should reduce the amount of air I pump in tomorrow. I am going to reduce it to 5 minutes at noon and 5 minutes at 5 PM. and see what pH's I get.


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## Tikulila (Feb 18, 2011)

Nice!!! I'll try it here, but I didn't really understand how you did the container, can you add a couple of pics, so then I'll understand it better.

Now let's see how long it holds, I say it has to work at least more than 1 month to be worth the effort.


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## HeyPK (Jan 23, 2004)

OOPS!! I said I was going to change the times to 5 min at noon today and 5 min at 5 PM today. It was dark and I didn't read the AM and PM settings correctly. Instead I set it to 5 min at midnight and 5 min at 5 AM this morning. The pH this morning was even lower, coming in at between 6 and 6.5. I set it so that it got one 5 min shot at 3 PM today, and now the pH is all the way down to 6. The brom thymol blue is yellow.


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## HeyPK (Jan 23, 2004)

I switched the CO2 output from the aquarium that just had green water to another one that is stuffed with plants, Vallisneria, Elodea and Myriophyllum. It is a 15 gallon with one 55 watt compact fluorescent. These plants pull down the CO2 rapidly. I have been feeding CO2 into this tank for four days now---5 minutes at 8:00 AM, 12 noon, 5:00 PM and 8:00 PM. The pH has been staying a little below 7.0. Color of the brom thymol blue is green.


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## Tikulila (Feb 18, 2011)

Well, I guess we got what we want, can you send a pic of it, because I didnt really understand the instructions.


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## HeyPK (Jan 23, 2004)

A---intake tube to compost. This tube ends above surface of compost. 
B---output tube from compost. This tube begins at the bottom of the compost. The pump (C) pulls air through the compost and pumps it through tube D to an air stone in the aquarium. (E) is the General Electric 7 day timer. It has to be plugged in. You can set up to 20 on-off settings. The pump is wrapped up in a nylon cooking bag with the bottom of the bag removed, making the bag a tube. The rubber bands at each end make the tube air-tight so that when the pump is on, the air being pulled in all comes from the compost. I chose the nylon cooking bag because ordinary plastic bags are much more prone to wear, developing holes, etc. The nylon is much tougher.


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## Tikulila (Feb 18, 2011)

Ingenius! I will make one, just with my changes, for i have different items here. 1 question, doesnt the CO2 escape from point A?

I'll be building it after my exam tommorow!, what a nice way to finish exam season! 

and seems like my filter is coming back in! and Of course, a new DIY reactor, what did you use?


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## HeyPK (Jan 23, 2004)

I am pretty sure that very little CO2 escapes from the tube at point A. This system does not build up pressure from CO2 production the way a fermentation system does. The fermentation system does not use oxygen, but it does produce CO2, and so there is a net production of gas and pressure builds up. The aerobic system uses up oxygen as it produces CO2 and, overall, pressure does not increase. In fact, pressure may decrease slightly. If carbohydrates are being metabolized, the amount of oxygen used will be exactly equal to the amount of CO2 produced. If proteins or fats are being utilized somewhat more oxygen will be utilized than CO2 produced. Either way, no CO2 gets pushed out. I used oatmeal (uncooked dry flakes) which is mostly carbohydrate. 

Another benefit of this system may be that, when you are not pulling air through it, O2 content decreases and CO2 content increases. As O2 drops, the metabolism of the bacteria, fungi, etc., probably drops also. When O2 gets really low, the metabolism of the whole system gets really low, too, and, basically, the system 'waits' until you pull in more fresh air, and then it cranks up again. Thus, it produces CO2 on demand. This means that whatever is being decomposed lasts longer than it would if oxygen were always present. I don't think the system switches to fermentation unless oxygen gets down to zero for a long time. If you pull a little air through it at least once a day, I think it will stay aerobic.


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## Tikulila (Feb 18, 2011)

Thats a good point, I will put it in 4 times a day each will be 15 min. (timers here go every 15 min, the digitals are quiet expensive) it'll be like your setup.


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## HeyPK (Jan 23, 2004)

fifteen minutes is the minimum??? A digital timer would give you a lot more flexibility. How much are they? The one in my picture cost U.S.$14.00. What are the prospects of getting one online?

If you have to go with 15 min. minimum, I would recommend a larger compost container than 1 gallon and that you have the container only a little over 1/2 full of compost. That gives you a larger volume of air in the container above the compost that functions as CO2 storage. If you had a small container with a small volume of air above the compost, you would pull most of the CO2 out of the system in the first several minutes, and after that, you would be pumping close to atmospheric air into your tank and probably blowing a fair amount of the initial CO2 out before it had a chance to dissolve. Also, I would get as small a pump as possible. With a larger container and a larger amount of compost, you could get the pH of your tank too low if you have too much decomposition. You will need to experiment with smaller amounts of oatmeal flakes or whatever you are planning to use as the material to be decomposed.

The pH of the tank my setup is pumping into is staying right around 6.5, which is just right. I wouldn't want it any lower. The brom thymol blue test is giving a yellow-green color. The plants (mostly _Elodea nuttallii_) have grown rapidly and are now shutting out nearly all of the light so that the bottom is quite dark.


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## Tikulila (Feb 18, 2011)

Ill hae to check, online is a prob, cause most sellers don't ship to israel. ill be going to all the shops here in the city to find a digital one. currently, the maual is about 30 shekels here, (8$) and the digital is about 200 (52$) so there is a huge difference... ill see what i can get.


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## HeyPK (Jan 23, 2004)

It also occurred to me that, if 15 minutes is your limit, you can lower the pump output to make sure you don't pump more than you want to. Most pumps have an output adjustment. If not, there are adjustable inline valves you can get.


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## Tikulila (Feb 18, 2011)

that is true, I'll buy a weak pump, which will be enough to do the trick.


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## HeyPK (Jan 23, 2004)

The setup has been running for 11 days now, and the pH in the aquarium is still between 7 and 6.5. Lots of pearling. I am planning a much bigger setup---a compost pile in a much larger container, perhaps 5 gallons. This time I am going to try composting dead leaves. The rate of CO2 production will be much slower, but with a much larger compost pile I should still get enough CO2. Also, production should last for many months.


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## Tikulila (Feb 18, 2011)

Smart, tommorow im going to finally get the equipment. About time.[smilie=s:


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## HeyPK (Jan 23, 2004)

I did some measurements of the CO2 content of the air being pulled out of my little compost pile in the gallon jar using a Scholander apparatus. This has a burette filled with 10% potassium hydroxide solution. Atmospheric air collected with a syringe is injected in to measure the volume collected by the syringe. Then air samples that have measurable CO2 are injected, and the difference in volume is due to CO2 that was absorbed by the KOH solution. For example, I injected air I exhale, and the difference was 3.57cc (atmospheric air) minus 3.44 cc (exhaled air) which equals 0.13cc. This works out to be 3.6% CO2 which is very close to what the physiology books say exhaled air ought to be (3.5%). 
When on my regular schedule of pulling air through the compost pile, (Pump on for 5 minutes at 9AM, 3PM, 5PM and 8PM) I got an average of 0.8% CO2. Much less than I expected, but enough, apparently enough to keep the pH of the fifteen gallon tank between 7 and 6.5. When I did not draw air through the compost pile for 48 hours, I got 12.0% CO2 in the air coming out one minute after the pump was turned on. 

Conclusion: (1) The system does build up CO2 when air is not drawn through it. Escaped CO2 through diffusion or air leaks is not serious. (2) Even when the CO2 content of the air put into the aquarium is quite low, one can still get a favorable amount of CO2 in the water. (3) A bigger compost pile would be better. I am thinking of a compost pile in a 5 gallon container. Two or more large containers could be together with the pump pulling from all of them.


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## Tikulila (Feb 18, 2011)

sounds good! unlike you, i seem to be under constants exam perssure, so its going on slowly, i still need to get some tubes... after that, its time to start the pile!

if you would put air pockets in the container, it might also help the build up of CO2, just as a guess, the bottom will also be able to produce some. Also, how often do you add oats?


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## HeyPK (Jan 23, 2004)

I think that, with the speed that a gas diffuses through a gas, the CO2 in the air in the container above the soil would be quite similar to the CO2 content in the soil. The air above the soil in the container should serve as storage. The soil should be loose and fluffy, if possible. Additions of peat should help with that. 

I have not added any more oats since I started. I suppose the time to add more would be when the setup no no longer keeps the pH in your aquarium where you want it.


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## DeChaoOrdo (Jan 7, 2012)

the main reason CO2 from fermentation is used is it's speed. Second is scale. It is not the most efficient method, as you've mentioned but in order to convert starches to CO2 time is necessary for the reactions, and the amount of CO2 produced by limited volumes will most likely be insufficient. Yeast may provide less yield% but the speed the reaction occurs at in small volumes makes it the simplest DIY method. On a larger scale, combustion is likely the most ready source for CO2(as is used in commercial applications). Respiratory CO2 has a higher percentage yield but also requires large volumes of source material. Using an aerated mix of yeast/water/sugar solution would easily provide a more steady and less dangerous CO2 source than fermenting the sugar, but you've got to keep KISS in mind.


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## Brightworks (Oct 10, 2010)

I hope to hear more about this. This looks to be true innovation to me.

HeyPK, 

I wonder if there is a way to speed it up (insulate, heat mat) I would happily use a 5 gal. bucket in place of compressed co2.

Are there any other environmental factors that would increase production?

What would happen if this were on a co2 controller? Would more frequent cycles increase production (more oxygen available for decomposition)?

DeChaoOrdo,

You mention using an aerated mix of yeast, water, sugar - can you describe this in more detail? How would this address the problem of excess alcohol (does aeration change this?)?


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## DeChaoOrdo (Jan 7, 2012)

Brightworks said:


> I hope to hear more about this. This looks to be true innovation to me.
> 
> HeyPK,
> 
> ...


The aerated mix wouldn't produce alcohol at all. Yeast are facultative anaerobes, in the presence of oxygen they use a different metabolic pathway than in anoxic and anaerobic conditions. This is seen in the early stages of yeast bottles there is a dramatic spike of CO2 production while the oxygen is used up, which then levels off and is followed by a bell curve as the fermentation carries. I have never tried this particular method since there are a lot of complications to creating such a setup, though.

While I'm posting in this thread I should note re-reading I see my initial objections were ill-formed, and what I proposed is essentially the same idea(using respiration to produce CO2). My cynicism over most new DIY CO2 schemes caused me to misread what was being said. I would be concerned over using this method due to the possibility of methane production in poorly aerated pockets in the soil, though.


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## H3LLRA1Z3R (Nov 9, 2010)

This is awesome, even if if doesn't work, still cool to try it.


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## HeyPK (Jan 23, 2004)

The compost pile-in-a-gallon-jar has finally slowed down in CO2 production. The oatmeal flakes originally put in 25 days ago are essentially gone. The daily pH tests with brom thymol blue are now up to plain blue color, pH close to or above 8. On Jan. 15, I removed the cover of the gallon jar (see the picture, post #30) and stirred up the soil with a stick. There was a little left-over mold, but the flakes were gone. The soil was a little drier than I would want it. I added some broken-up pieces of uncooked spaghetti, about 1/4 of a cup, added a small amount of water and put the cap back on. I thought that the spaghetti might be broken down more slowly than the oatmeal flakes. No visible increase in CO2 production was seen yesterday. Some mold was beginning to grow on the spaghetti sticks. The tank now has a very heavy growth of Elodea. I expect to see some lowering of the tank pH over the next few days as the decay organisms get to work on the spaghetti pieces. 

I may be able to get my hands on a pH probe and software that automatically takes measurements. This would make a very nice graphic record of the tank's pH.


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## HeyPK (Jan 23, 2004)

*Re: Why CO2 from fermentation? OOPS!*

Another OOPS!! A big one. I did the brom thymol blue test in the 15 gal today, and still got the cold blue that says pH 8 or higher. This is odd. The spaghetti pieces I put in are fully invested with mold, and I ought to be getting more CO2. I decided to check the timer to see if it was going on at the programmed times. It turns out it wasn't. It was ignoring them. No wonder the pH was high! I tried various settings with the manual button, but the programmed times continued to be ignored. When all else fails, read the manual. It turns out that before programming, you always have to reset the timer with that little recessed button that you have to poke with a pencil tip. Apparently when I changed some of the programming times, the changes were not only ignored, but the original program settings were now also ignored. Eventually, I had changed all the times, and all settings were ignored. That is probably when the pH started going up and I concluded that the oatmeal was all used up (My previous post, #47). So, Ignore post 47.

It seems that you can change the clock times without messing up the programming. The way to check if all your programmed times are working is to change the clock to 1 minute before the program is due to turn the pump on, then wait and see if the air pump starts up. My programmed times are now 8:00 AM, 12:00 noon, and 5:00 PM, all on for 5 minutes. They all work. I checked. It will be interesting to see what pH's I get tomorrow. It seemed strange and upsetting that I was getting these high pH's. Now, all is right with the world again.


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## HeyPK (Jan 23, 2004)

Now that the time clock is working, giving me 5 minutes of air from the compost at 8AM, 12:00 noon, and 5:00 PM, the pH is back down to between 6.0 and 6.5, yellow green with more yellow than green. Putting in the pieces of uncooked spaghetti has increased the CO2 output.


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## ObiQuiet (Oct 9, 2009)

This is fascinating.


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## Tikulila (Feb 18, 2011)

It is. HeyPK, sems like you got the hang of it, here it is still in process.

Maybe add some fish, so we can see the effect it has on them? It might be dangerous if any methane gets there.


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## HeyPK (Jan 23, 2004)

The worry about fish is that you could cause them real distress if the system produces and you pump in too much CO2. It would be prudent to set up the system and let it run until you know how to control the CO2 output by how many minutes the clock is set to run the pump, how much and what kind of organic matter is being decomposed, and how many times the pump is turned on by the clock each day. Once you have all that under control, there shouldn't be any problem. When adding organic matter that breaks down quickly, you should not add large amounts because you might get a big CO2 increase that could be bad for the fish. If you are not sure, add small amounts and check your pH the next few days. You can get an idea that way of how much you need to add to get the pH where you want it. 

It looks to me as though the ideal system is one that does not have organic matter that breaks down rapidly producing a pulse of CO2 that lasts only a few weeks. I am thinking that dead tree leaves would produce CO2 steadily for many months, possibly a year or more. It remains to be seen how many tanks could be supplied and what volume of composting tree leaves would be required. If a leaf composting system could be developed, it would truly be a "set it and forget it" system. 

I got yellow with some green---pH nearer 6 than 6.5 again today.


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## Tikulila (Feb 18, 2011)

Thats my plan, a mixture of crushed leaves and soil, as from our earlier discussion you pointed that out. My guess is I'll do two 15 min times a day, each before lights.


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## AndyManic (Jul 16, 2009)

Wow! Keep it up guys. Nice read, very interesting.


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## ecotanker (Jun 12, 2009)

Very interesting! You guys have inspired me to try it out. I think a mix of quick fuel like cereal and slow fuel like dried leaves would be good to start. The quick fuel is to get the digester population up and running, and the slow fuel would be for maintaining the population. 

I need to get this up and running soon!


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## ecotanker (Jun 12, 2009)

I think we need a name for this setup. How about Carbon From Respiration Reactor. CFR reactor for short.


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## HeyPK (Jan 23, 2004)

How about DIY aerobic CO2.


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## Tikulila (Feb 18, 2011)

Well, that was ironic... anymay, nice way to simplify things HeyPK.


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## HeyPK (Jan 23, 2004)

The yeast-sugar system is also producing CO2 from respiration---anaerobic respiration. One could call the aerobic method, AECO2 and the anaerobic method, ANCO2. Or, how about compost pile CO2, CPCO2? Dirt-cheap CO2, DCCO2?? Or just DCO2---dirt CO2? Nah! that won't sell.


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## catsma_97504 (Sep 4, 2010)

This has been a very interesting thread to read through. Looks like it has worked quite nicely. Will be watching to see how things turn out. I wonder if the compost to tank size holds true for larger volumes.

Sent from my Motorola Electrify using Tapatalk


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## ecotanker (Jun 12, 2009)

Adding one more word would make a great name for any apparatus using this concept - carbon from aerobic respiration reactor. I can see CFAR reactors as the next big DIY thing.


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## ecotanker (Jun 12, 2009)

Well it has been a week since I set up the reactor, and today when I open it to check I got hit with a
funky sour smell.

Is this to be expected?


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## HeyPK (Jan 23, 2004)

> Well it has been a week since I set up the reactor, and today when I open it to check I got hit with a
> funky sour smell.
> 
> Is this to be expected?


What did you add as your source of CO2? Was the reactor closed with no access to fresh air? Once you set it up, you need to pull some air through it daily to keep the oxygen level from going to zero.

My little gallon jar compost pile is still producing. I put some broken up uncooked spaghetti pieces in it when the oatmeal flakes were about used up, and the pH of the tank went down to between 6 and 6.5 for a week and then between 6.5 and 7 for another week. When the pH went above 7, I put some more spaghetti in a week ago, and the pH is still down in the yellow green category---between 6 and 6.5. I figure I can keep adding spaghetti pieces for quite a long time. Some time in the future, minerals from the spaghetti are going to accumulate to the level where their concentration may inhibit the community of breakdown organisms. At that time I can either replace the soil or remove the mineral salts from the soil by leaching them out with water. If one occasionally leaches out the mineral build-up, the soil and its community of breakdown organisms should last forever.


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## ecotanker (Jun 12, 2009)

I built something similar to what you had posted in post #30, electric timer and all,
except I did not make the jar cover air tight.

My fuel source consist of white flour, soy flour crumble dry leaves. I also put in some dry peat granules for air pockets.


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## HeyPK (Jan 23, 2004)

The cover of my setup is not really air tight. I have a short intake tube. (See picture in post # 30) However, I did want to minimize loss of CO2 via the cover. I think the problem is the soy flour. That can produce a really bad smell.


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## scolling007 (Feb 1, 2012)

How did you prevent soil from beeing leeched out of the outtake tube that is going to the pump?

also do you think that it might be better if the pump is placed inside of a bottle that can have holes drilled and sealed with silicone to replace the need for the airtight bag?


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## HeyPK (Jan 23, 2004)

I don't like the idea of the intake tube having all the air intake at one location---the end of the tube---even though I don't think that the velocity of air at the end of the tube would be enough to suck in soil unless you had a really big pump. Still, it is a possibility. It would be better to have a lot of small intake holes spread out, rather than all the intake at one place. I have some ideas on how to spread out intake, but none that I am completely happy with, yet. I want the solution to be something that can be made with easily available materials. 

Also, if you got the soil way too wet, there might be the problem of water being sucked into the pump. I suppose a water trap bottle could be put in the line going to the pump. 

Having the pump in an air tight container such as a jar would be better than the bag, which is a compromise. You would want the container to fit the pump closely so that there would not be a large volume of air in it. The nylon cooking bags are pretty tough and do not easily develop holes due to wear and tear. If you seal the ends going around the intake and the exit tubes well, you should have a system that is quite air tight and doesn't pull in significant outside air while pulling air through the compost. You can test the setup by clamping off the intake tube and turning on the pump. If the bag flattens next to the pump and the air output of the pump decreases, then you have a satisfactorily air tight set up.


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## ecotanker (Jun 12, 2009)

I thought about having a layer of air below the soil, kind of like a plenum or an undergravel filter, with the air tube going to the air pump bag connected to this air layer. There will need to be some kind of thing separating the underlying air layer and the soil perhaps a small plastic jar with a fine mesh covering it.



HeyPK said:


> I don't like the idea of the intake tube having all the air intake at one location---the end of the tube---even though I don't think that the velocity of air at the end of the tube would be enough to suck in soil unless you had a really big pump. Still, it is a possibility. It would be better to have a lot of small intake holes spread out, rather than all the intake at one place. I have some ideas on how to spread out intake, but none that I am completely happy with, yet. I want the solution to be something that can be made with easily available materials.


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## Tikulila (Feb 18, 2011)

That would be a good way to "wash" all the CO2 fro the jar to the tank. a way would be like a bell diffuser, a bit above the bottom of the jar. might be worth a try.


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## HeyPK (Jan 23, 2004)

My little compost pile in the gallon jar is still producing. I added some more dried spaghetti fragments about two weeks ago. A week ago, I noticed that the brom thymol blue was blue-green, and I discovered a 3/4 inch hole in the plastic top. Perhaps the cat did that. I replaced the plastic with something a little tougher, and the color went back to green. Today I happened to be there when the timer turned the pump on, and the time on the said it was 7:08 PM. That's funny, I never set the timer to go on at 7:08 PM, and the actual time was 5:00 PM. The pump turned off at 7:11 PM. Funny, I had my times set to run the pump for five minutes, not three. I checked the settings on the pump and they were all blank. The pump should have not been running at all. I don't know how the timer got so messed up, and so I hit the reset button and re-entered the clock time and the on-off times. I'm going to have to watch this timer.


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## Tikulila (Feb 18, 2011)

So, how is it going?


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## HeyPK (Jan 23, 2004)

I've been too busy to keep it up, and so everything is dry in the compost jar. No CO2 is being produced. As soon as I get all the grading done, I will be able to get back to it. Is anybody else trying this method?


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## Tikulila (Feb 18, 2011)

i had to stop mine, too, but in about 2 weeks ill restart it.


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## ecotanker (Jun 12, 2009)

Mine is still going. My plants are growing better but yet to get pearling. Since I just set up a new way to diffuse the gas I will wait and see if this will give better results.


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## Tikulila (Feb 18, 2011)

good, so the project was a success


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## ecotanker (Jun 12, 2009)

Yes, so far.


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## HeyPK (Jan 23, 2004)

The way to improve on this method is to move from a small container where rapidly decomposing stuff is added frequently (like every two weeks) to a large container that has slowly decomposing stuff that only needs to be renewed every 6 months or every year. Water would have to be added more frequently, but that is a simple process that would take very little time. I envision something like a 5 gallon container filled with a 4:1 mixture of dead leaves and soil.


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## Diana K (Dec 20, 2007)

A larger container would also allow you to put the air pump right in the container, eliminating the nylon bag and its connections. 

Perhaps... 

Large plastic storage box
Grid near the bottom, propped up on chunks of PVC pipe (egg crate? 1/4" hardware cloth?)
Decomposing matter on top of the grid.
Shelf near the top of the box, well out of the compost. Air pump sits on the shelf. 
To draw air through the compost drill some holes through the storage box, under the grid, but on the sides (not the bottom) of the box. Small holes ought to be fine, but maybe several so air gets drawn in all around/under the grid. 

See the drawing. 
I can see a few problems, need solutions:
Will there be too much gas exchange though the holes? Maybe use a one way check valve on these? 
Can storage boxes be sealed well enough to do this, yet leave the lid removable to replace the compost?
Need to seal the holes in the box where the electrical for the pump passes through, and the air tubing. (Air tubing is easy to seal: Drill the hole a bit too small. Self sealing against low pressure)


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## Diana K (Dec 20, 2007)

OK, going fish room sized set up:

More than one air pump, each on its own timer. (Assuming very large storage box) 

Once an hour one of them comes on, rotating through the day each one would come on more than once, but how often? (If they come on too often they are not getting very much CO2)

Can you skew it so the aquariums get a boost of CO2 in the early AM, just as the lights are coming on? If you did not harvest the CO2 in the dark, does it accumulate to worthwhile levels so you could harvest a lot of it when you wanted it? 

How large a container and what materials give the optimum production of CO2? 

Since it is temperature dependent would it help to warm the compost for an hour or two (more? less?) before you wanted maximum harvest? (Reptile heating pad on a timer, or soil heating cables that are used to start seeds) 

Goal:
Maximum CO2 as the lights go on.
Then replenish each tank as often as possible through the day. Then stop at lights out so the tank goes through the night with lower levels of CO2. 
The build up of CO2 in the compost box ought to allow a bigger harvest in the AM.


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## ecotanker (Jun 12, 2009)

Would CO2 greater than air density give it the tendencies to concentrate in the layer below the compost?

If this is the case, then the air holes should be near the top of the reactor and the pump should have 
either be located below the compost or have some way of tapping the air below the compost. 

My current design is based upon the assumption that CO2 would concentrate below the compost, but I don't know for sure if this is the case.


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## Tikulila (Feb 18, 2011)

so, here is a few answers:


Best Temp: 37 degrees celcuis

moisture would do some good.

Diffution rates will be slower the rates of bacteria CO2 buildup. after a night, CO2 in container will be high.

You would want a STABLE community of bacteria, even myabe add a specific Bac' for best results- I'll see about that.

"Food": a combinations of brown things and green things. (different minerals)

Check valves will work, good idea.

CO2 Is HEAVIER then air, so yes, ecotanker you are correct.

and lastly: I dont have anough room to make an expirament :crybaby:...


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