heat posts

I saw an article about cities doing various things to reduce heat, including lighter road surfaces and planting trees. Trees provide good shade and reduce temperatures, and are generally good for the environment, but can require quite a bit of water for dry areas. I got to thinking that we could build artificial tree-like structures to provide shade. But it would require a lot of material, and it would be undesirable cost-wise and environmentally to dig up new materials for this purpose. So I wondered about building them from waste materials.