Nuclear waste is small and solid

That would depend on the category of the waste:

- High level waste - Transuranic waste - Low level waste

where high level waste comes in two classes: spent fuel and reprocessing waste, the latter being liquid (possibly not green).

https://ieer.org/resource/classroom/classifications-nuclear-...

You can just bury it deep in a mountain

Belgium is notably lacking in mountains, which is why they now start building a site for low level nuclear waste storage, adding to the cost. For high level nuclear waste they have to build deep underground, waterproof, bomb-proof facilities at high expense:

https://www.nirasondraf.be/

As for the article by Shellenberger you linked, please note that he is a right winger criticising wokeism etc, who claims eternal growth can continue like until now without ecoogical impact

https://en.wikipedia.org/wiki/Michael_Shellenberger

Edit: I just found out that Shellenberger now works on finding the Aliens:

Unidentified Anomalous Phenomena: Exposing the Truth", Shellenberger claimed sources have told him that intelligence communities "are sitting on a huge amount of visual and other information" about Unidentified Anomalous Phenomena (UAP)

Same wiki.