I like this city trees idea a lot. Probably less practical - at least for the diamond-creating part, more of an art project - is the Smog Free Project by Daan

I like this city trees idea a lot. Probably less practical - at least for the diamond-creating part, more of an art project - is the Smog Free Project by Daan Roosegaarde. It collects smog particles from the air, which are then to be turned to diamonds and sold to the public to raise awareness. https://www.weforum.org/agenda/2016/06/why-turning-smog-into-diamonds-isn-t-as-crazy-as-it-sounds/ https://www.weforum.org/agenda/2016/06/why-turning-smog-into...