This is a really old idea that is being brought back under the guise of aesthetics instead of the original function, which makes it fucking stupid. The original idea was to use cylindrical tanks along roadways with specific types of algae that were multiple times better at scrubbing smog and other emissions than trees. The idea being they could be put in places that trees couldn't be maintained, like the medians or sides of freeways. Personally I thought it was a good idea. This new shit is dumb.