Chapter 10
CO2 Combustion Generators
 
     The CO2 generator has long been a fixture of commercial greenhouse growers. Unlike the injection system, the generator works by constantly creating CO2, instead of releasing enough to treat an entire room at one time.
     The generator is often used in greenhouses because the structures are drafty and the CO2 enhancement would be soon lost if the release was intermittent. The process used by commercial CO2 generators is quite simple. A clean burning gas such as propane or natural gas is burned through a burner like is found in a stove or furnace. Each pound of gas burned yields about 3 pounds of CO2, or about 25 cubic feet.
     The generation principal works on all levels. Large commercial generators are used in greenhouses and large area growth chambers. A simple and small alcohol lamp can be used in a closet growth chamber to provide CO2 enhancement, although I cannot recommend a flame in a room with combustible materials.

Advantages of Generation

  1. Equipment can purchased for all size systems.

  2. If the house containing the grow chamber is plumbed with natural gas, there is no need to haul around large tanks.

  3. An alcohol lamp type generator uses only a gallon or so of alcohol each week (much less for the small closet type operation). This is easily transported into areas where propane or CO2 tanks may present a problem. Alcohol fuel can usually be purchased at any hardware store.
Disadvantages of Generation

  1. Flames always contain an inherent danger of catastrophic fire.

  2. Generation of CO2 by burning puts heat and water vapor into the air. The heat may be unwanted, the water vapor can always present a problem.

  3. It is not recommended, and is usually illegal with good reason, to keep a pressurized tank of propane in a closed area.

  4. Incorrectly plumbed gas fittings may leak creating a fire / explosion / asphyxiation hazard.

  5. A knocked over lantern or alcohol lamp can instantly become a roaring inferno. Since the alcohol flames burn with an almost totally clear flame, the fire can get a good start before it’s noticed, even if the grower is in the room!

  6. A flame can use up all the oxygen in the air, resulting in asphyxiation in a tightly closed area.

 

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