Question: How do trees extract Co2 from the atmosphere then return the air molecules back to the environment?

Susan Cartwright answered on 18 Jun 2020: last edited 18 Jun 2020 4:28 pm

This is a process called photosynthesis, which is described in detail at https://en.wikipedia.org/wiki/Photosynthesis. To summarise, plants combine CO2 and water with energy input from light to make sugar and oxygen: 6CO2 + 6H2O –> C6H12O6 + 6O2. The CO2 is absorbed, and the oxygen emitted, through the leaves, in a similar sort of way to the way we absorb oxygen through our lungs.

Interestingly, plants didn’t develop this technique themselves: they stole it. Photosynthesis takes place in organelles within plant cells called chloroplasts, and chloroplasts are nearly identical to a kind of free-living organism called cyanobacteria. We think that long ago single-celled ancestral plants actually engulfed some of these cyanobacteria and kept them alive within their own cells to produce food!