I know that a greenhouse is not air tight so I imagine it breathes somewhat and exchanges gas with the outside. However, I also assume that it’s going to use up the co2 in it for plant growth. How does it not run out? I think you could vent it, but then wouldn’t that cool it off and thus defeat the purpose of a greenhouse? All my web searches either give climate change facts or co2 supplementation by farmers.
Mostly it’s fine as others have stated, but sometimes they pump CO2 in there. One example is Friðheimar tomato farm in Iceland, which enhances photosynthesis by using carbon dioxide produced from natural geothermal steam.
I’m so mad that there isn’t a link to more info about that, because I’m wracking my brains and I can’t think of any mechanism that makes sense.
Not sure how they capture the carbon dioxide, but it’s delivered to the greenhouse itself from a giant tank outside the building. I realize that’s probably not the part of the process you were interested in, but it’s all I’ve got.