Home Made CO2 Production - How To Guide

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Hi Guys, this is from my journal and I've been asked if I would post it here too, so here it is:

A few people have asked about the CO2 bubblers I have in my little grow tent so here's exactly what the set up is, very cheap and I think successful looking at my girls in comparison to my last grow they are way way ahead but that could just be the difference in strains, these are Autos the others weren't.

In my set up I'm using:

2 x 1.5Liter drinks bottles

2 x Wine/Beer bubblers - Cost anything between $3-5 for two including the rubber bungs.


1 x Cup Unrefined sugar

Half teaspoon Bakers Yeast, apparently brewers yeast is even better and last a bit longer as mine only produce bubbles well for three days before I either add more sugar or a freshmix completely.

Half teaspoon baking soda to speed up process a little.

Empty and clean your bottles, you can use bigger if you like just up the ingredients a bit, pour in 1 x cups of unrefined sugar, you can use standard white but I just happen to use unrefined anyway so it was to hand.

Then pour in some warm NOT hot water fill 2/3rds, you must leave room at the top for expansion or they can overspill !!!

Place top back on and shake furiously till sugar is pretty much dissolved in water, then remove top and add your yeast and baking soda, put top back on and shake like mad again.

Voila, your mix is ready, now just put the bungs in bottle tops and put bubblers in the bung holes, fill one side of plastic bubbles with water and you'll be able to see exactly how often it produces bubbles of CO2.

Mine normally start produciing within 3-4 hours and then bubble every 5-15, faster at first and then slowing down, once they slowed right down just repeat the whole exercise again or just top up with more sugar.

I tend to do a completely fresh set up otherwise it produces bubbles but nowhere near the same rate.

I'm doing my nutes change today and have now got another two bottle, which I now intend to hang above the plants, one in each corner as CO2 is heavy than oxygen so drops down, ideally you want it dropping onto your plants.

There are many other ways to use CO2 from tiny little cannisters 5-10grams right up to huge great cyclinders with hundreds of liters but for most home/small growers the method described above is cheap and effective, the only problem is you have no real control over exactly how much CO2 is being released nor do you know exactly how much it's producing, unless you get a CO2 meter.

Here's my set up with four bottles hanging one in each corner.

Hope this helps,



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Nice description bro ! very useful

Jah bless

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Hey Toaor - Just got back from the home brew shop inspired by your bubblers, got a couple of bubblers and the guy said this super wine yeast compound was the best stuff for the job - guy said a few people actually do this for their plants


gonna get my bubbler bubbling when lights go on

thanks again thumbs_up.gif

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started bubbling after around 3 hours of making the mixture....

Toaore - you are a genius

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this is a good post, my friend;

take care,


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Glad you've foudnn this post useful guys.

Salvador, I used bakers yeast and baking soda and it's starts bubbling within about 10 minutes but only last about 3 or 4 days before it slows right down, you can just add some more sugar for the yeast to eat up but I generally do a completely fresh batch, I have no idea exactly how much CO2 they are producing though as I don't have a CO2 meter but any extra has to be worth it.

I have been looking at other cheap options too and you can buy tiny little CO2 cartridges off Ebay or big spray cans from Aquarium shops and just spray it in whenever you like. I'm trying to find an automatic gauge and valve to do it for me but as yet nothing.

All the best guys,


If any of you grow outdoors, what sort of yields are you getting in comparison to indoors? I'm trying to work out roughly how much I'll end up with per plant for my guerilla grows, I've read of amounts from 600gms to 1.2kg per plant.

I want to grow enough to see me right through to next spring/summer growing season so need about 70-80 ounces and want to know ho wmany plants to put out bearing in mind they won't all survive the summer, some may get discovered and stolen so I'm working on 50% surving the whole season, I have 10 plants to go out in next week or two and have another 15 seeds in germ cubes.

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toaor and salvador - thank you both very very much.... i have just implemented this oparandi and it works just fab!

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You're welcome Rebel Yeah, I replace mine with fresh mixture every 4/5 days, you can just add more sugar but it works much slower so obviously less CO2, I need the extra to help my plants in the heat.


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Excellent post Toaor

Full of good advice

Peace to the highest


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Awesome post Toaor, i will be trying this out next time i go to the hardware shop nice and simple i like it and best of all cheap, thanks buddy

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Troaor, this is a great post, I'm off to the shop to get myself a bubbler and some yeast. Cheers for this great little but genius tipcool

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Thanks for the great tutorial men, i need to ask you though:

Can you introduce co2 in your grow room at any point? Does the age of the plant or the previous exposure to co2 plays any role?

Thanks again!

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@ Elias...co2 can be introduced at any time of the plants's what the plant breathes exhales and plant were meant to live together...we exhale what it exhales what we need..mutually benificial.

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Thanks sixstrings, i've dropped one bucket in my box yesterday with yeast, 1.5 kg of sugar and some hot water, mixed the all thing.... We'll see what kind of impact it has on my babies!

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great topic and great idea ;)

But don't forget guys, i might be wrong, That when you increase your CO2 level you have to increase at the same time all the other elements too in order to make it worth something.

Meanings amount of light, Heat in the room (supposed to be around 30° in CO2 enriched room if i remember right) etc...

Thanks for sharing man i might try this next summer :)

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nice man, we see quite a few people using this system :) How did you like it? you saw an improvment?

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Nice tutorial. I was thinking to buy a CO2 generator but now i know i can create a homemade CO2 generator cheap.

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I have a tent in my bedroom woukd it be to dangerous to use co2 because my tent is hard to keep under 30 it stays at 30 so co2 would be good thing if anyone nows thanks this is a good idea peace

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I have never used C02 enrichment.


I did not have an answer, so this is what I found on the interweb.


CO2 caculator -


The air already has about 390 PPM (thanks Rich) so you only need to add 1110 PPM more to get the optimum level of 1500 PPM

copied and pasted from -




What are safe levels of Carbon Dioxide




Levels of carbon dioxide (CO2), a colorless, odorless gas, have been known to reach 3,000 parts per million (ppm) in homes, schools, and offices with no ill effects. The maximum recommended by the National Institute of Occupational Safety and Health (NIOSH) for an 8-hour occupation is 5,000 ppm (13 times the current level of 380 ppm). The Occupational Safety and Health Administration (OSHA) also use 5,000 ppm as their threshold for occupational safety.


But 5,000 ppm appears to be a very conservative estimate of safe levels because other sources claim we can tolerate up to 1.5% of it in air, 15,000 parts per million.


Consider: people with respiratory problems are given medical gas typically consisting of 95 percent oxygen and 50,000 ppm (5 percent) carbon dioxide. This gas can also be obtained with CO2 ranging from 1% to as high as 10% for treating people who have been asphyxiated.


Also consider: we would die if we did not breathe in such a way as to retain very close to 65,000 ppm (6.5%) of CO2 in the alveoli (tiny air sacs) of our lungs.


And finally, the American Industrial Hygiene Association (AIHA) reports that 100,000 ppm (10%) of CO is the atmospheric concentration immediately dangerous to life.


Scientific studies on higher levels of CO2


Altitude sickness is caused by hyperventilation, which results in increased oxygen (O2) in the blood but decreased CO2. (Note: oxygen (O) occurs as a molecule in nature, hence the symbol O2) The lowered CO2  will not allow the increased O2 to be utilized. Adjusting to this condition is called “ventilatory acclimatization”. While it is not completely understood all that happens during this process, it has been observed by experimentation that supplementing CO2 prevents this acclimatization as well as preventing the sickness. It appears that respiratory distress due to lower levels of O2 (requiring ventilatory acclimatization) can be relieved or eliminated by the application of a higher level of CO2.


This might be a good time to ask: since we exhale CO2, why do we need it to be present in the air we inhale? Good question, but apparently, we do as demonstrated by the above experiment. Other experiments found that simply circulating CO2 up one nostril and out the other while the subject held their breath cured migraine headaches as well as allergic symptoms. Other researchers propose administering CO2 to people who suffer from epilepsy, Parkinson’s, and autism as well. Clearly, we are affected by low  levels of CO2 in the air we breathe and need to acclimatize to these low levels, if we can, but not everyone can. Consider:


ı People who experience periodic breathing as well as apnea (cessation of breathing) during sleep benefit from higher levels of CO2. These conditions affect a lot of older people.


ı Increased levels of CO2 can improve the sleep of young people as well. One study found that healthy young men on a submarine slept well when CO2 levels rose but not as well when the levels dropped.


ı Furthermore it’s administered in the form of medical gas (1% to 10%) for many medical conditions to  stimulate respiration. For example, people with asthma require from 3% to 5% for therapeutic effect.


Studies suggest that a lower level than this but somewhat higher than present atmospheric levels would prevent the attacks in the first place and prevent subclinical symptoms associated with asthma such as anxiety, insomnia, immune dysfunction and excessive sensitivity to pain. CO2 levels higher than 5 per cent are used for extreme cases such as for treating victims of asphyxiation and to stimulate breathing of  newborn infants as well as speeding recovery of patients who have been anesthetized.


ı The majority of us have some degree of lung impairment, which affects the more critical function of the lungs in regulating the proper level of CO2 in the alveoli (tiny air sacs). Metabolic syndrome alone includes approximately 20 – 30 % of adults in the U.S. and Europe. Then there are smokers, asthmatics, and people with miner’s lung, emphysema and scarred lungs due to previous bouts of pneumonia, old people, and many more conditions. Furthermore, a wide range of medical conditions and infectious diseases manifest in pulmonary symptoms. All these conditions can require medical gas because the present atmospheric level is not optimum and appears to lack a safety margin for people with lung impairment. Breathing is a tricky business. We have to breathe fast and deep enough to get the O2 we need but not so fast as to hyperventilate and lose control of our blood’s CO2 balance (pH). Over the last 50 million years the O2 level and CO2 level have both dropped as well as atmospheric density, which puts us into the same predicament as the mountain climber who must acclimatize to a higher altitude. Even healthy mountain climbers reach a level at which they cannot further adapt. People with lung impairment are like the climber who has reached that level. Either an increase in the O2 level or an increase in the CO2 level would be a benefit. It is for good reason that people hospitalized are fitted with air tubes to their nostrils providing them very high levels of oxygen and carbon dioxide. (Typically, 4.5 times the oxygen but, more  importantly, 130 times the carbon dioxide that is in the atmosphere)


ı Experiments have shown that even healthy people have different tolerances (or sensitivity) to CO2  levels. However, we can all acclimatize to much higher levels simply by constant exposure to those levels.


Physiological changes occur as well as adaptive breathing changes. There is a curious variation in these physiological changes noted in studies of people who live at higher altitudes, which seem to be a result of genetics. The natural experiment of human colonization of high-altitude plateaus on three continents has resulted in two—perhaps three—quantitatively different arterial-oxygen-content phenotypes among Andean, Tibetan and Ethiopian high-altitude populations. The dominance of Ethiopian (and neighboring Kenyan) athletes in endurance marathon running events would appear to be a result of their unique evolutionary adaptation in this regard.


Copied & pasted from -


So that is what I found, hope it is interesting reading for you.


Peace brother


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nice reading here :) What method would you use to add your CO2? a DIY setup or a real one with bottles? usually if you choose the bottles for proper CO2 levels it iwll cost a little more cause you really to measurate to have the good levels like Lams showed before and not be dangerous for you, but when you do with bottle usually you want your room to be 100% air tight, so it's kind of dificult with tents, if you jut go for DIY or the CO2 bags, you should be pretty safe with only one :) don't sleep with 10 people in your room and all windows and door closed :P


Good luck man

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Nice Dust, you made lots of good points there and you made me chuckle too :) Good humor ;)

CO2 in bottle is really cheap, no one needs to make thier CO2 unless they just want to play and like making it. To refill a 14LB gas bottle is £15 GBP that is loads of CO2. You can rent the empty bottle for £50 GBP a year, that is les than £1 GBP a week. You can also buy a bottle for £57 GBP and it will be full whaen you buy it (you own this bottle for life, only need to pay for refill).

The CO2 dosing regulator can be around £160 GBP this is the most expensive part to buy, but hat iis the same price as 5 exhale bags. After a couple of grows you will be saving money although there is a higher intial start up cost.

Lmao! Just found some more info.


Carbon Dioxide Enrichment Methods

By Roger H. Thayer, Eco Enterprises


Carbon dioxide is an odorless gas and a minor constituent of the air we breathe. It comprises only .03 % (300 parts per million, or PPM) of the atmosphere but is vitally important to all life on this planet!

Plants are made up of about 80-90 % carbon and water with other elements like nitrogen, calcium, magnesium, potassium, phosphorous and trace elements making up only a small percentage. Almost all of the carbon in plants comes from this minor 300 PPM of carbon dioxide in the air.

Plants take in CO through pores, called stomata, in their leaves during daylight hours. They give off oxygen at the same time, the results of a process called photosynthesis. This oxygen that they give off is used by humans and all animal and marine life on this planet. Without it, animal and human life would not be possible.

Oxygen comprises almost 20 % of the earth's atmosphere. Most of it was generated by plant life. The process of photosynthesis combines CO2 and water to form sugars and free oxygen. Simple sugars like C6H12O6 provide plants with energy and are formed into the more complex plant parts such as carbohydrates, amino acids, protein, cellulose, leaves, roots, branches and flowers.

People and animals breathe in oxygen generated by plants and breathe out the CO2 that the plants needóa truly symbiotic relationship. In ancient times, millions of years ago, when there was only plant life on the earth and no animal life, the atmosphere was quite different. There was much more volcanic activity, one of nature's sources of CO2, and the air contained three to four times as much of it than now. Plants thrived. Giant tree ferns reigned supreme and much of our coal, gas and oil deposits were created by them during that long-ago time.

Plants would benefit from more CO2 in the air today, and actually are benefitting as we burn more fuels, one by-product being carbon dioxide. CO2 in the air has increased from 270 PPM to over 300 PPM, more than an 11% increase, in just the last 40 years! This has also worried many scientists because of what is called the greenhouse effect.. The more CO2 there is in the atmosphere, the higher the planet's temperature will go. Too much warming of the planet can melt ice caps, flood coastal cities, spread deserts and famine and drastically change the climate. This effect is somewhat self-regulating however. The oceans absorb a great deal of CO2 giving algae and plankton, 90% of the plant matter on earth, more CO2 to grow on and giving the rest of the plant matter on land more also. This decreases the amount of CO2 in the atmosphere, thereby regulating it. Scientists are just now learning to understand the self-regulating systems that stabilize most factors in our environment.


Biologists and plant physiologists have long recognized the benefits of higher CO2 content in the air for plant growth. Horticulturists and greenhouse growers have used CO generators to enhance growth rates on plants for many years with good results.

With the advent of home greenhouses and indoor growing under artificial lights and the developments in hydroponics in recent years, the need for CO2 generation has drastically increased. Plants growing in a sealed greenhouse or indoor grow room will often deplete the available CO2 and stop growing. The following graph will show what depletion and enrichment does to plant growth:


Below 200 PPM, plants do not have enough CO2 to carry on the photosynthesis process and essentially stop growing. Because 300 PPM is the atmospheric CO content, this amount is chosen as the 100% growth point. You can see from the chart that increased CO can double or more the growth rate on most normal plants. Above 2,000 PPM, CO2 starts to become toxic to plants and above 4,000 PPM it becomes toxic to people.

With the advent of ideal growing conditions conditions provided by metal high-intensity discharge (H.I.D.) lighting systems, hydroponics, environmental controls such as temp., humidity, etc. and complete, balanced plant nutrients such as Ecogrow, the limiting factor on plant growth rate, quality, size and time to maturity becomes the amount of carbon dioxide available to the plants.

There are five common methods of generating extra amounts of CO2:

1. Burning hydrocarbon fuels

2. Compressed, bottled CO2

3. Dry ice

4. Fermentation

5. Decomposition of organic matter

We will discuss these five methods briefly in turn. In order to make an effective comparison of CO2 generation, benefits and drawbacks, a std. 8' X 8' X 8' or 512 cu. ft. growing area will be used.


This has been the most common method of CO2 enrichment for many years. A number of commercial growers and greenhouses use it in their larger structures. The most common fuels are propane, butane, alcohol and natural gas. Any of these fuels that burn with a blue, white or colorless flame will produce carbon dioxide, which is beneficial. If a red, orange or yellow flame is present, carbon monoxide is being generated due to incomplete combustion. Carbon monoxide is deadly to both plants and people in any but the smallest quantities. Fuels containing sulfur or sulfur compounds should not be used, as they produce by-products which are harmful.

Most commercial CO2 generators that burn these fuels are too large for small greenhouse or indoor grow room applications. Some small ones are avai fable or a Coleman lantern, bunsen burner or small gas stove can be used. All of these CO2 generators produce heat as a by-product of CO2 generation, which is rarely needed in a controlled environment grow room but may prove beneficial in winter growing and cool area greenhouses.

The rate of CO2 production is controlled by the rate at which fuel is being burned. In a gas burning CO2 generator using propane, butane or natural gas, one pound of fuel produces approximately 3 pounds of carbon dioxide gas and about 1.5 pounds of water vapor. Approximately 22,000 BTUs of heat is also added. These figures can vary if other fuels are used.

To relate this to our standard example in an 8' X 8' X 8' growing area, if you used ethyl or methyl alcohol in a gas lamp or burner at the rate of 1.3 oz. per day, we would enhance the atmospheric concentration of CO2 to 1300 PPM if the room was completely sealed.

An enrichment standard of 1300 PPM was chosen as it is assumed that 1500 PPM is ideal, and that the plants will deplete the available CO2 supply by 100 PPM per hour. Remember, the normal atmosphere contains 300 PPM of CO2. A 100% air exchange (leakage) every two hours is assumed to be the average air exchange rate in most grow rooms and tight greenhouses. If many cracks and leaks are present, this exchange rate will increase significantly, but added CO2 (above 300 PPM) will also be lost. If a vent fan is in use, disregard CO enrichment, as it will be blown out as fast as it is generated.

A circulation fan is beneficial, as it moves the air about in the greenhouse or grow room. If the air is still, it can cause a "depletion layer effect". This effect causes the CO2 right next to the plant leaf to be quickly depleted. If fresh air carrying additional CO is not brought to this surface, photosynthesis and growth will diminish and eventually cease.

There are a number of factors involved in keeping the CO2 content at the desired concentration level. 1. If the greenhouse or grow room is not tightly sealed up, add up to 50% to the CO2 generator production volume. 2. If temperature is increased fiom 70 F to 90 F, add 20% to the volume generated, and vice-versa. 3. If the grow area contains large or tightly spaced plants, add 20% to 30% to the CO2 volume generated.

If more light is used, more CO2 can be utilized and should be produced proportionately up to the practical limit of 5,000 footcandles per square yard and 1500 PPM CO2 atm. content. When more CO is generated, more water and plant nutrients should be used, again to a practical limit of 2X normal. lf your plants are going to grow faster because of CO2 enrichment, they will need more nutrient and water.

The last factor to consider in maintaining a set CO2 level is the size of your growing area. This is simply done for gas burning and following methods by setting up a mathematical ratio. In our "standard" room (8' X 8' X 8'), we have 512 cubic feet. If your growing area measures 10' X 10' X 20', you have 2,000 cubic feet of volume to contend with. If you want to use the ethyl alcohol/gas-lamp enrichment method, set up the ratio using l.3 oz. by weight of alcohol per day gives:

1.3 oz./day = 512 cu. ft.

------------------ -------------------

X oz./day = 2,000 cu. ft.


Then cross multiply: 512 X = 1.3 X 2,000. Dividing both sides by 512 gives you X = (1.3 X 2000)/512, solve for X. X = 5 oz.

You need 5 oz. of ethyl alcohol per day in a 10' X 10' X 20' grow area to generate the same amount (1300 PPM) of CO2 as in a 512 cu. ft. room.

To generate 1500 PPM above the available CO2 (200 PPM) in the same size area, set up the ratio:

1300 PPM = 5 ounces

-------------- ------------

1500 PPM = X

X = (5 X 1500)/1300 = 5.77 ounces.

NOTE: One pound of CO is equivalent to approximately 8.7 cu. ft. of gas at standard temperature and pressure.

If different hydrocarbon fuels are used, the heat content, in terms of B.T.U. should be taken into account. If the BTU per hour rate is half that of ethyl alcohol, twice as much must be burned to generate the same approximate amount of CO2 desired. The amount of CO2 generated depends on the carbon content of the fuel being used. The BTU per hour heat content can be obtained from literature or suppliers.


This is the second most popular method of CO2 enrichment and provides fairly accurate, controlled results. Compressed CO2 comes in metal containers under high pressure. Small cylinders contain 20 lbs. of compressed CO and large tanks hold 50 lbs. Pressure ranges from 1600 pounds per square inch to 2200 PSI.

To enrich available CO with compressed gas, the following equipment is needed:

1. Tank of compressed CO2

2. Pressure regulator

3. Flow meter

4. Solenoid valve, (plastic or metal)

5. Short-interval 24 hr. timer capable of having an "on time" variable from one to 20 minutes.

6. Connecting tubing, fittings and adapters


This method allows for the injection of a controlled amount of CO2 into the growing area at a given interval of time. The pressure regulator reduces the compressed gas pressure from 2200 lbs./square inch to a more controllable amount (100 to 200 PSI) which the flow meter can handle. The flow meter will deliver so many cubic feet per minute of CO2 to the plants for the duration of time that the solenoid valve is opened. The timer controls the time of day and length of time that the solenoid valve is open.

To operate this CO enrichment system in our standard 8' X 8' X 8' grow room area, we want to add enough CO to increase the near depleted level of 200 PPM to 1500 PPM. We must then add 1300 PPM of CO2 to a volume of 512 cu. ft. We would like to do this in intervals of time relative to the natural air exchange rate (leakage rate) to keep the CO level near the 1500 PPM range.

Let's select an injection time interval (CO2 enrichment time) of every two hours. First, we must determine how many cubic feet of CO2 must be added to 512 cu. ft. of volume to increase our 200 PPM to 1500 PPM. To do this, multiply the room volume of 512 cu. ft. by .0013 (1300 PPM) to obtain 0.66 cu. ft. of CO2 that is needed. Set the regulator at 100 PSI and the flow meter at 20 CFH (Cubic Feet per Hour) or 0.33 cubic feet per minute. If we set our timer to stay on for two minutes every two hours, we will get the 0.66 cubic feet of additional CO we need to bring the CO level to the 1500 PPM optimum level needed.

Each pound of CO compressed gas contains approximately 8.7 cubic feet of CO gas at atmospheric pressure. Compressed CO2 costs around 50 cents/lb. at most supply houses. At that rate of 0.66 cu. ft. every two hours for 18 hours per day, this method will cost around 30 cents per day to operate. The timer should be set to deliver CO2 during the "on time" (daylight time) for which the lights are set. This is the only time the plants can use CO2; they do not use it when it's dark.

The compressed gas method of CO enrichment has the advantages of fairly precise control, readily available equipment ($150.00 to $300.00 average cost for an installation) and it does not add extra heat to the growing area. It also works well for small growing spaces and after initial equipment costs, is not expensive to operate.


This method works well for small areas, especially if some cooling effect is desired. Dry ice, solid carbon dioxide, is very coldóabout 109 degrees F below zeroóso we suggest you handle it with gloves. Dry ice is available through freezer and meat packing outlets and is relatively inexpensive. In our std. 8' X 8' X 8' room, you would need about 0.8 lbs. of dry ice per day to raise the atmospheric CO2 content to 1300 parts per million. If the growing area is quite warm, 0.8 lbs. can melt much faster than 18 hours. Two methods can be used to regulate this. One is to cut just small pieces, about .1 lb., and add a new piece every two hours to the growing area. The second method is to put the required amount in an insulated styrofoam box with a few small holes cut in it. This will slow the rate of melting considerably but must be "tuned in" to get it just right so 0.8 lbs. melts in the 18 hours of light "on" time. Extra dry ice must be kept in a freezer to prevent loss due to evaporation.

Since CO2 is heavier than air, one good method of distributing it to the plants is to attach the container or dry ice to the light reflectors which are normally placed over the plants. The CO2 will then flow down through or over the lights and evenly bathe the plants. If a circulation fan is used, the dry ice or its container should be placed directly in front or behind it for even distribution. Common to all CO2 enrichment methods, try to seal up the room or greenhouse as best you can, especially around the bottoms of doors and walls.

The dry-ice method will cost around 60 cents per day for our standard sized, 512 cu. ft. grow room. A possible benefit of using dry ice is the cooling effect it produces.


Sugar is converted into ethyl alcohol and CO2 when it ferments due to the action of yeast. In this method, the following ingredients and equipment are needed:

1. Suitably sized container, plastic or glass

2. Sugar, common or invert

3. Yeast, brewers or bourgelais wine yeast

4. Yeast nutrient

5. Sealant, cellophane, tape or lid

6. 1/4 plastic tubing

7. 1/4 shutoff valve

8. Balloon

9. Starter jar or bottle

A pound of sugar will ferment into approximately half a pound of ethyl alcohol (C2H5OH) and half a pound of CO2. One pound of CO2 makes 8.7 cubic feet of CO2 gas at normal atmospheric conditions. In our standard 8 X 8' X 8' grow room, you will need to generate 512 cu. ft. X .0013 (1300 PPM CO2) = 0.66 cubic feet of CO2 every four hours. It takes time for the yeast to ferment sugar, so the size of container you should use in determined by dividing the cubic feet of growing area (512 Cu. ft.) by 32 = 16 gallons.

A convenient container to use here would be a plastic kitchen garbage can. These are inexpensive and easily obtainable.

To determine how much sugar we need for six weeks of operation or until fermentation ceases, the following calculations are necessary: From the above paragraph, we need 0.66 cu. ft. of CO2 every four hours. If one pound of CO2 makes 8.7 cu. ft. of CO2, we will need 0.08 lbs. of sugar, but because every one pound of sugar only makes 1/2 lb. of CO2, we must double the amount of sugar needed, i.e. 0.08 X 2 = 0.16 lbs. of sugar every four hours. Since there are six four-hour periods in a 24 hour day, the amount of sugar we need is 0.16 x 6 or 0.96 lbs. of sugar per day.

If we round this off to one pound of sugar per day, we will need 42 lbs. of sugar in six weeks. We must consider that only 80 to 90% of the sugar will be completely converted in this length of time, therefore, we should actually use about 48 lbs. of sugar in six weeks.

The sugar solution to start with is 2 1/2 to 3 lbs. per gallon. You can use hot water to start with, as sugar dissolves faster in it than in cold water. You must let it cool to 80-90 degrees F before adding yeast to it or the yeast will be killed. Start with the fermenting container only half-full as you will be adding an extra gallon per week for 6 weeks. Begin with eight gallons per week and 24 lbs. of sugar.

To start the solution fermenting, you will want to make a "starter batch" of sugar water, yeast and yeast nutrient. To do this, use a coke or beer bottle (approx. one pint), dissolve 1/4 lb. of sugar in 10 oz. of warm water (approx. 3/4 full), add a pinch of yeast and two pinches of yeast nutrient to this sugar mixture. Place a balloon on the bottle and set in warm location, 80 to 90 degrees F, for one to two days or until the balloon expands and small bubbles are visible in the solution.

After the starter solution has begun fermenting vigorously, it is added to the main fermentation tank at the same temperature already mentioned. After a day or so, to see that the system is working properly and that CO2 is being generated, close the valve to the supply tube and, if the unit is sealed properly, the balloon should expand in a short period of time. To regulate the amount of CO2 being delivered to the plants, open the valve until the balloon is only half the size of full expansion.

The CO2 supply tube with in-line valve should have a 2" loop in it half full of water to serve as an air-lock. This loop can be held in place with tape on the side of the fermentation tank. The open end of this tube can either be positioned in front of a circulating fan or run through "T" fittings to make additional tubes, the ends of which can be positioned above your plants. Remember, CO2 is heavier than air and it will flow downwards.

Once per week, undo a corner of the Saran Wrap and add an extra gallon of sugar solution and yeast nutrient, then reseal the top with tape. Use three lbs. of sugar and one teaspoon of nutrient per gallon.

After the last gallon is added, after six weeks of operation, let fermentation continue until the balloon goes down and no more bubbles are visible in the "U" tube. When this point has been reached, taste the solution. If is it sweet, fermentation is not complete and a new starter batch should be made and added to the tank. More yeast nutrient should also be used. If the solution is dry (not sweet) like wine, fermentation has stopped and the alcohol content has killed the yeast. At this point, it's time to clean your tank and start a new batch.

The fermentation process is quite good for generating CO2 and relatively inexpensive. Regular or invert (corn) sugar is inexpensive and available. You may have to purchase invert sugar at a wine supply store. This method of generating CO2 will cost approximately 50 to 60 cents per day.

To save money on extra yeast, you can either take out approximately a gallon of fermenting liquid and save for the next batch, or start a second system identical to the first and alternate themóclean and replenish one, then three weeks later, clean and replenish the second.


When organic matter decomposes due to bacterial action, carbon dioxide is generated. Plants grow lush and vigorously on a tropical jungle floor as a result of this natural decay of dead plant and animal matter. This can increase the available CO2 content from the normal 300 PPM amount to over 1,000 parts per million. This can also be done indoors, for little cost, but is odorous and unsanitary. For these and other reasons, it is not highly recommended. The sterile conditions of a well-set-up hydroponic grow room or greenhouse could be disrupted and adverse bacteria, bugs and disease induced with detrimental effects on your plants.

In conclusion, all these methods will work if done properly and CO2 enrichment is a very beneficial addition to your greenhouse or grow room systems. Some are more practical than others, some less expensive and some require more time and attention. All chemical reactions are temperature dependent and photosynthesis is no exception. With CO2 enrichment, a higher temperature, up to 100 degrees F, can be used, more light may be needed as it is required for the photosynthetic reaction to take place. More water and nutrients will also be required, and a machete may be necessary to control the added, sometimes startling extra growth rates possible on most plants by using CO2 enrichment!

Courtesy of the Hydroponic Society of America. Copied & pasted from


Peace Hunters


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About us

Strain Hunters is a series of documentaries aimed at informing the general public about the quest for the preservation of the cannabis plant in the form of particularly vulnerable landraces originating in the poorest areas of the planet.

Cannabis, one of the most ancient plants known to man, used in every civilisation all over the world for medicinal and recreational purposes, is facing a very real threat of extinction. One day these plants could be helpful in developing better medications for the sick and the suffering. We feel it is our duty to preserve as many cannabis landraces in our genetic database, and by breeding them into other well-studied medicinal strains for the sole purpose of scientific research.

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