So years ago something similar to this was floated as a green alternative to street lamps and similar things. Basically big tubes of algae. They actually figured out how to get and store energy from the photosynthesis of the algae and use it to power a light in or above the tank. The crazy part is the efficiency of the algae at removing CO2 from the air. One tank could pull as much CO2 in one year as one tree does in it’s average lifespan. At least that’s what they reported. Course it would take a ton of maintenance and not sure what you do with the waste algae. As a method for sequestering CO2 it has merritt. Course then there’s always the thought of how much CO2 is generated from actually making one of said tanks. That I do not know but I still don’t think it’s a bad idea. Not really as a replacement of trees though. Hell even in the pictures of this bench thing there are still trees around it. You can see the trunk of a tree behind it and the some branches off to the side on the other image.