The writer makes a useful point about the nature of “renewable” resources. They can be more finite than “non-renewables.”
It matters, of course, what type of material we are categorizing. Petroleum, for example, is a finite resource in all the ways that cucumbers are. Cord wood burned in furnaces or stoves, or even lumber used to build houses (to preserve heat for human comfort) similarly would be more cucumber-like than copper-like.
But the basic observation remains valid. Even copper must eventually and irreversibly oxidize. It is just a matter of speed. In which case it is odd to call some of the fastest burning things “renewable.”