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Well-Known Member
Sep 5, 2021
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NE Victoria, Aus
I was just wandering if anyone has ever tried to increase a level of CO2 in a growing area and if yes, what is your experience. I have found a few home made CO2 generators on line and I am very keen to test it but if its a waste of time I’d rather not bother.
If I am remembering high school science, when plants photosynthesize, they take the energy from the sun along with chlorophyll producing a simple sugar and oxygen.
At night, after photosynthesis stops, plants I seem to remember take in carbon dioxide.
This is overly simplistic.
Just where this fits into your plan, I don’t know.
I "experimented" (AKA dabbled at a ridiculously non-scientific effort) enhancing the CO2 in my greenhouse once.

1) It was practically difficult in a large structure. ($$$)
2) 400 ppm CO2 is about normal now, and at about 1300 ppm or so, it becomes toxic.
3) I was able to get the level up to about 900 ppm for a month before I gave up, seeing nothing and deciding to stop wasting money of bottles from the local gas supply store.
I think your culture on other factors, light, nutrition, water, etc must be near perfect before you see any real benefit from CO2. However, I haven't tried myself and have been curious too.
I used to pump CO2 into the water of my aquatic fish tank. It was astonishing how fast my plants grew because of it. About an inch a day. Every week I would have to greatly prune my plants. The plants also produced an incredible amount of oxygen bubbles that would continually rise to the top of the tank. Certainly very effective in an closed aquatic setup. Not sure how you would set it up in a greenhouse. levels will,and faster flowering per plant.
There have been a few studies citing the benefits and it is used in some highly intensive horticulture systems but the real world in a hobbyist greenhouse is a very different situation. Perhaps the best starting point would be to create a well sealed grow chamber within your greenhouse and experiment in a much smaller, controlled space. It would also mean you don't need to enter the high CO2 space making it safer.
I was just wandering if anyone has ever tried to increase a level of CO2 in a growing area and if yes, what is your experience. I have found a few home made CO2 generators on line and I am very keen to test it but if its a waste of time I’d rather not bother.
You can buy bags of mushroom spawn that will generate CO2 over a period of several months... Or make your own. If you make your own it can be very inexpensive.

A local guy sells these (he uses a bioluminescent fungus I think - just because it is easy). But you could easily make your own. Oyster mushrooms or lions mane would give you CO2 and dinner.
Terrestrial and emerged plants are not subject to CO2 limitation like submerged aquatic plants. The big issue is water limitation for terrestrial plants.

Epiphytic orchids employ Crassulacean Acid Metabolism photosynthesis ( which means they absorb and store CO2 at night. They can only store as much CO2 as there is phosphoenol pyruvate to convert to malate with the absorbed CO2. Could CO2 fertilization at night increase malate production? I have no idea but think it doubtful.

Not all orchids employ this mechanism of photosynthesis and how CO2 would affect them I do not know. For fast growing species there could be a visible benefit but for slow growing plants I don't expect we would notice any difference.

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I have researched CO2 exhaustively...there is a wealth of information in the marijuana growing world...and it works. In fact some intensive lighting systems for marijuana are not recommended without the addition of a CO2 system.
While visiting Sam Tsui during his last couple months in business, I recognized a C02 burner hanging near the ceiling. I asked him about it and he gave me a brief instruction on usage and offered to give it to me.
C02 burners and generators are not expensive and you could even use C02 from a welding supply business. The harder and more expensive part is the measurement and control system.
I could install a C02 system in my GH for under $ would be an extravagance that would only work from about November to somewhere around March, because the GH is basically a closed sealed system...Outside of that time period, vents and fans are being used to control temperatures.
In the marijuana growing world C02 is used indoors with LED lighting and climate controlling systems keeping temperature parameters in a zone.
I have thought that when a grower (orchids) is producing excellent plants, surely "culture" is key, ppm fertilizers used, and very possibly C02. Tokyo Orchid Nursery...Hmmm. Sam Tsui used it!
I believe there is a benefit, how much, Im not so sure.
This is an interesting read: Physiological diversity of orchids

It seems some orchids can switch from CAM to other methods of photosynthesis based on water supply. If water needs are met CO2 would become limiting -- assuming all other needs are met.

If you want to add CO2 simply run a gas heater in the grow area.
Correct on the heater.