gree-knees, if I remember correctly, the carbon dioxide (CO2) is made to combine with water (H2O) to produce a carbohydrate (general formula, CHO) and oxygen (O2). The reaction requires light of a minimum intensity (I forget how many foot candles) and chlorophyll.
As far as I know, this reaction, photo synthesis, takes place only in the green leaf, needle, tendril and similar plant structures.
I marvel at the exquisite elegance of the reaction. Carbon dioxide in the atmosphere is replaced with oxygen.
No fuel, fossil or other, is required and there is no harmful by-product.
I have 'a thing' about artificial plants, but that has no relevance to your question or its answer.

Try here:

Here is a link that might be useful: Wikipedia: Photosynthesis

I used to have a license plate with H2O+CO2 on it. :-)

I forgot to say Thanks. Thank you,ronalawn and resin. What's your "THING" about artificial plants? Anita

"and there is no harmful by-product"

Some people might consider "weeds" to be a harmful by-product ;-)

gree-knees, I 're-visited' and saw your question and pineresin's comment.
My concern about artificial plants is that they will be popularized to the point where natural (non-artificial) vegetation will be 'in the minority'. It will be something of a travesty if I were to have only artificial turf, silk trees and plastic flowers in my landscape. It will be something of a tragedy if everyone did the same.
It was love at first scan when I read a weed defined as "a plant whose virtues we have yet to discover". I guarantee that if purple nutsedge (Cyperus rotundus) offered a cure for cancer it will lose its dishonorable place as one of the world's most widespread weeds.
My attitude towards plants almost precludes me from using the word weed, casually.