Back in 1989 - Dow Chemcial made a proposal. Even then, there was too many plastic type to sort out and contamination was a major issue. They had a realistic but somewhat defeatist solution. Just burn it all. Use it for heat and power, treat plastic as an intermediate step of oil and nothing more. Then figure out emissions capture technology so that it can be stored somehow.

I don't agree with it entirely but I did like that it was an realistic approach to a complex problem.