CO2 for you

Carbon dioxide (CO2) generators are perhaps the single most powerful increasers of plant production. During the daylight hours plants breathe in and use CO2 much the same way we animals metabolize oxygen. By adding CO2 to the air of the grow room we are capable of greatly stimulating plant growth and vigor.
Overexposure to CO2 by humans is very capable of proving fatal. Therefore, also remember that monitoring of the air with a CO2 or gas detection device is mandatory when using a commercial CO2 distribution system.

There are two main types of commercial CO2 delivery systems, bottled and propane generators.

Bottled CO2

The bottled CO2 system delivers pure CO2 via a tank that is rented or bought and refilled when empty at any bottled gas distributor or grow shop. The purchases of a regulator and tubing, along with a specialized timer, are necessary to complete the system. The timer opens the regulator to dispense the gas that is delivered to the room among the plants via the tubing (or whatever duct system is chosen for its delivery). The timer usually is on for brief periods of a few seconds per minute, hence the need for the specialized timer.

The bottled systems are relatively efficient and once set up, easy to use. When used in conjunction with some kind of CO2 metering device, to monitor the amount of CO2 in the air, the system is relatively safe. The main drawback is having to deal with filling the heavy, bulky tank when needed. The initial expense is a bit of a sticker shock as well.

Propane generator

Propane generators of CO2 have been gaining popularity since their introduction to the industry some time ago. Bottled propane is connected to a device that burns the gas, slowly and evenly, to produce CO2. The device is usually a box that will hang in the room and is connected to the propane bottle via the appropriate tubing and coupling. It is possible to time and regulate most propane generators to efficiently produce CO2 gas when needed. These devices are usually much simpler and less expensive than the bottled CO2 systems. Propane is also easily available in most places.

There are, however, a few dangers to the propane generator that need to be addressed. First of all, the device utilizes a small flame for CO2 production. Special care needs to be taken whenever dealing with fire, and necessary precautions including location of the device need to be made prior to operation. second, this flame will produce some heat and humidity. The humidity is in the form of water vapor, the other by-product of the process. Proper venting and air circulation will help minimize these factors. As with the bottled system, monitoring the amount of CO2 in the air will be necessary to regulate the proper and safe amount of the gas delivered to the room.

Air circulation

Because CO2 is a gas that is heavier than air, a word needs to be said about the delivery system and air circulation in the room. Generally speaking it is best to introduce the gas up higher in the room, via some form of tube or duct or by hanging the propane generator up high. This way the gas passes by the leaves of the plants on its way down, allowing them to absorb as much as possible. Oscillating fans placed on the floor with their fan pointing up (or any upward movement of air from the floor) is also recommended to best circulate the CO2 among the leaves of the plants. The roots of the plants DO NOT like CO2. In fact, too much CO2 around the roots may actually suffocate the plants. So be wary of these facts and circulate the air well.

There are a number of books and manuals on the market today that deal with the specifics and ?how to?s? of carbon dioxide production for commercial (and home) use. Also, ?growstores? selling the devices offer plenty of advice and/or literature pertaining to the specifics of their products. Remember, CO2 production for larger scale operations requires a certain amount of knowledge unobtainable by any other means than an education. Therefore, I highly recommend that one research thoroughly before one purchases and uses a system.

Small and simple

For those of you running smaller systems such as cupboard, closet or ?box? systems, there is a simple CO2 system that is easy to make and use. This system uses water, sugar and yeast mixed together in a jug, bottle or jar. I like to use one-gallon plastic jugs due to their size and availability.

Put about five or six cups of sugar in a clean one-gallon plastic jug. To this add about a half gallon of water. Mix until the sugar is dissolved and add a little bit of active yeast. Poke a small hole in the lid and replace it on top of the jug. Once a day, or as often as possible, shake the jug to thoroughly mix the contents. In a day or two the yeast will begin to grow and CO2 gas will be a by-product in the jug.

Once the yeast begins to grow, the shaking of the contents will produce a gaseous eruption through the hole in the lid. On its own, the device will slowly produce CO2 as long as there is enough sugar in the mix and the yeast stays active. The daily shaking stimulates the mix to produce a surge of CO2 gas. Therefore, the more times the jug is shaken, the more surges of CO2 that will erupt into the room. The mix will need to be changed or refreshed every two to three weeks. I have found this system to be more than adequate and perfectly safe for smaller grow spaces (twenty square feet or less). It is also very inexpensive to configure and maintain.

Recycled CO2

A source of recycled CO2 may be found in any natural gas or propane appliance, especially those with a pilot light. All such appliances produce CO2, when properly functioning, that is. A simple rule of thumb is: blue flame = CO2 or what we want, yellow flame = CO or carbon monoxide, deadly poisonous! It is merely a question of how to get the CO2 gas from the appliance to the grow room. If the appliance (furnace, hot water heater, stove, etc.) is anywhere near the grow room, then a simple duct system of dryer vent tubing running from the bottom of the appliance (remember, CO2 is heavier than air) to the grow room will suffice. A muffin fan placed on the room end of the tube, blowing into the room, would efficiently move the gas.

Finally, any form of brewing (beer production) or fermenting (wine making) produces CO2, as well. So a home brew kit or home wine making system could also be used to add CO2 gas to the grow room air.

Remember to be very careful not to overdo the CO2 and let the gas fill your house. If this happens then it could suffocate you in your sleep! But properly used, CO2 can be a safe and easy way to increase the yield of your garden.



  1. Anonymous on

    i have a friend that uses a yeast sugar co2 generator to feed his aquarium plants.. this is what he does.. obtain a 3 litre bottle of soda.. yes 3 litre.. if only a 2 litre is availble use it.. also you need a litre water bottle.. aqufina works fine.. empty both bottles… you need aquarium airline tubing and a small air stone (wallyworld) take a drillbit slightly smaller than your tubing drill one hole in the soda cap and 2 in the water bottle cap microwave 1 cup water and 2 cups sugar to dissolve.. add 2 tablespoons yeast after watersugar combo has cooled to about 100 degrees
    take airline tube insert into sodacap at the top.. just enough to push it in.. take that line and insert it into one of the holes in the water bottle.. insert it all the way to the bottom of the bottle and attach your air stone to this tube.. with more tubing insert it into the last hole in the water bottle.. this is your co2 exhaust tube.. add a couple inches of water in your water bottle to create a water filter( like a h20 pipe).. take your exhaust tubing a place it near a fan nice and high as co2 is heavier than air.. enjoy i have found the co2 lasts quite a while.. you can see how much is being produced by the amout of bubbles that emit from your air stone.. check out eds comments on co2 enrichment.. hes the bomb..

  2. Anonymous on

    do not do that. It will attract fungus flies

  3. Anonymous on

    I have a small closet garden thats about 3x4x6 and i tried the mixture of sugar water and yeast. Does it slowly let off co2 or does it only do it when you shake it up?

  4. Anonymous on

    for a short boost of co2 i used a travel size shampoo bottle and a small tupperware and a cup of baking soda. First i poked a smallhole in the top side of the bottle, then filled it 3/4 of the way full of vinegar. the put the 1/2 cup of baking soda in the small tupperware. if in a large pot u can set the container of baking soda in the pot on top of the soil. then i lay the shampoo bottle containing hte vinegar on its side above the baking soda so that it drips slowly into the baking soda creating the bubles and co2 desired. at this point all exhaust and intake fans are off so that the small enclosure such as a closet or cabinet fills with the co2 gas sorry so crude. didnt feel like typing but wanted to get this out there as it works great depending on ur setup.