E-mail - How Much CO2 to Add - Plant Processing of CO2

Hi I read your article on co2 enrichment. Very informative! I do have one question though. How fast do plants process the co2? What I mean is, how long do I need to leave the fans off after I add co2 to the grow room? I have a small area, 6x6. My budget is low, so I am using a poor man's approach and just empting 12 gram co2 cartridges over the plants. Since the amount is so small, will the plants process it in 15-30 minutes? Also, if I am able to say purchase one of the co2 enrichment packages from HTG, how long would I need to leave the fans off? Thank you for your time.

Hello,
Glad to hear people are still checking out some of my old articles. To start with, I should say that the CO2 in the atmosphere has a concentration from 0.03 to 0.04 %. However, it is found that increases to CO2 to 0.1% of carbon dioxide in the atmosphere increases the rate of photosynthesis significantly. This was tested indoors with enclosed chambers where plants are grown under controlled conditions. Crops like tomatoes, lettuce etc. were successfully grown in the chambers and were found to be bigger and better-yielding than their counterparts growing in natural carbon dixoide conditions. I have read your rate of photosynthesis increases if you increase carbon  dixoide to 0.2%.( that is 2000 ppm)   After that I have not seen any studies showing improved growth.


As it said in my article you can figure out the ppm in your room with a bit of basic math and I would try to get your ppm up to 0.2% or 2000 ppm if you can.  Since the use of CO2 is dependent on many variables here are some things to keep in mind: Plants will use more CO2 the higher their rate of photosynthesis. If you use a HID, your plants will use more CO2 than with a fluorescent light fixture. Also, the bigger your plants are, the more CO2 they can use. So, the more light you give the plants and the bigger they are the faster they will use up the CO2. For best results you need to add the CO2 above the plants in a sealed room with no ventilation (fans are ok just no exhaust fans) and let the plants be exposed to the high CO2 concentration for an extended time. They need to soak in the CO2 through tiny holes (called stomata) in their leaves.


How are you adding the CO2? “manually”, I am not exactly sure what the C02 cartridges are? If you are doing this with the door open, you may not get improved results as the CO2 will diffuse out the open door.


As I mentioned, the ideal system is to have the CO2 released when you are not in the room, and the door is closed. You should try to seal the room to make it air tight. This way, the plants will use as much of the CO2 as possible before it leaves the room. Also, if the room is sealed well you should leave a light fan on, this will help mix the CO2 which will have a tendency to sink to the bottom of the room. If you have an exhaust fan, you could shut the fan off during the night cycle, when there is less heat and a need for exhaust, and add the CO2 then. This will give your plants 6-12 hours of exposure (depending on what light cycle you are using) and that way you can be sure your plants are using all the CO2 they can. I understand you are on a budget, but a CO2 system with a timer releasing the gas above the plants in a sealed room is really the best way to increase your growth and yield with CO2, I have read studies that show a doubling of yields just by increasing CO2.


I do want to end by saying that any CO2 you add should help the plants grow better, so although I can't tell you exactly how many grams you should add, if you add any it is better than nothing. A time release system would be optimal, and then using my article you could add enough CO2 to the room to see big results, but anything you do to improve you growth is good.

I hope this helps, good growing,
Dr. E.R.Myers