"This plastics thread is too frequently ignoring the huge differences between different plastics. "
You will usually find plastics issues posted on the Renewable Energy discussion board.
https://discussion.fool.com/t/plastics-reduction-treaty-fails-again-at-busan-meeting/110856
Yes, this thread is not strong in background but we do have people on the boards who are well informed.
The big issue is recycling, sorting things into the 7 groups, some much easier (and more profitable to recycle) than others. The PET used in pop bottles and water bottles is easiest to recycle. It also has linkages that breakdown in the environment meaning it is likely to degrade faster over time. Worst are polyethylene and polypropylene–often milk bottles. Can be made into railroad ties, deck planks, telephone poles, etc, but not worth much. Probably lasts forever in a landfill or the ocean. Can be cracked into petroleum fractions but not much value in them.
In the '60s the detergent industry learned that anything you put in the environment needs to biodegrade. Otherwise it accumulates and eventually causes problems. The plastics people design theirs to last forever. There are some biodegradable plastics but they have not found much acceptance. Gluing particles together with cornstarch has much potential to resolve issues. Remember paper mache?