CO2 Generator Systems

Marijuana Horticulture

by Jorge Cervantes

CO2 generators are used by commercial flower, vegetable, and marijuana growers. Green Air Products has introduced a complete line of reasonably priced CO2 generators that burn natural gas or LP (propane) to produce CO2. However, heat and water are by-products of the combustion process. Generators use a pilot light with a flow meter and burner. The inside of the generator is similar to a gas stove burner with a pilot light enclosed in a protective housing. The generator must have a cover over the pen flame. You can operate the generators manually or synchronize them with a timer to operate with other grow room equipment such as ventilation fans.

CO2 generators produce hot exhaust gasses (CO2 + H2O). Even though CO2 is heavier than air, it is hotter and therefore less dense and rises in a garden room. You must have god air circulation for even distribution of CO2.

Carbon Dioxide generators can burn any fossil fuel – kerosene, propane, or natural gas. Low grades of kerosene can have sulfur content as high as 0.01 to 1 percent, enough to cause sulfur dioxide pollution. Use only high-quality kerosene even though it is expensive. Always use grade “1-K” kerosene. Maintenance cost for kerosene generators are high, because they use electrodes, pumps, and fuel filters. For most grow rooms, propane and natural gas burners are the best choice.

When filling a new propane tank, first empty it of the inert gas which is used to protect it from rust. Never completely fill a propane tank. Propane expands and contracts with temperature change and could release flammable gas from the pressure vent if too full.

Generators burn either propane or natural gas, but must be setup for one or the other. They are inexpensive to maintain and do not use filters or pumps. Hobby CO2 generators range from $300 to $500, depending on size. The initial cost of a generator is slightly higher than a CO2 emitter system that uses small, compressed gas cylinders. Nonetheless, growers prefer propane and natural gas generators, because they are about four times less expensive t operate than bottled CO2 generators. One gallon of propane, which costs about $2, contains 36 cubic feet of gas and over 100 cubic feet of CO2 (every cubic foot of propane gas produces 3 cubic feet of CO2). For example, if a garden used one gallon of propane every day, the cost would be about $60 per month. In contrast, bottled CO2 for the same room would cost more than $200 per month!

CO2 generators are less expensive to maintain and less cumbersome, but they have some disadvantages, too. One pound of fuel produces 1.5 pounds f water and 21,800 Btu of heat. For grow rooms less than 400 cubic feet, this makes generators unusable. Even for larger garden rooms, the added heat and humidity must be carefully monitored and controlled so as not to affect plants. Growers in warm climates do not use generators, because they produce too much heat and humidity.

If fuel does not burn completely or cleanly, CO2 generators can release toxic gasses – including carbon monoxide – into the grow room. Nitrous oxide, also a by-product of burning propane, can grow to toxic levels, to. Well-made CO2 generators have a pilot and timer. If leaks or problems are detected, the pilot and timer will turn off.

A CO2 monitor is necessary if you are sensitive to high levels of gas. Digital alarm units or color change plates (used in aircraft) are an economical alternative. Carbon monoxide is a deadly gas and can be detected with a carbon monoxide alarm available at most hardware and building supply stores.

Check homemade generators frequently, including kerosene or gas heaters. Propane and natural gas produce a blue flame when burning efficiently. A yellow flame means unburned gas (which creates carbon monoxide) and needs more oxygen to burn cleanly. Leaks in a system can be detected by applying a solution of equal parts water and concentrated dish soap to all connections. If bubbles appear, gas is leaking. Never use a leaky system.

Oxygen is also burned. As it becomes deficient in the room, the oxygen / fuel mixture changes. The flame burns too rich and yellows. This is why fresh air is essential.

Turn off CO2 generators at night. They create excess heat and humidity in the grow room, and they need oxygen to operate. At night, roots need the extra oxygen in the room for continued growth.

if you are using Co2 and the yield does not increase, check to make sure the entire grow room is running properly and that plants have the proper light and nutrient eves, as well as the correct temperature, humidity, grow-medium moisture, and pH. Make sure roots receive enough oxygen both day and night.