Well, given what we know about most commercial plastics, which are all derived from oil/complex hydrocarbons, the consumed plastic could be broken down into condensed carbon? Or would it be carbon gases? I'm speculating based on just what I know about plastics, what they are and how they're made.

That's because this narrative is at odds with another environmentalist narrative.

Carbon compounds are oxidized by non plant organisms to form carbon dioxide.

The resulting material is fungus? That’s how eating works