The University of Belgrade’s Institute for Multidisciplinary Research invented an urban photo-bioreactor. Liquid 3 cleans the air and serves as a bench in the Belgrade city centre.
It’s a tank filled with microalgae, a solar panel on the top generates electricity for USB charging ports for citizens and a pump that pumps air into the tank where the algae process the CO² and produce Oxygen.
https://balkangreenenergynews.com/liquid-tree-to-combat-air-pollution-in-belgrade/
I think this is super cool for places trees don’t easily grow, like atriums and “walls” within public spaces, airports ,etc
Cost per year of maintenance versus equivalent tree.
Might make sense in a space colony. But only barely.
I don’t know this could be useful for underground tunnels or colonies.