Trex makes composite decking planks from recycled shopping bags. Seems like a perfect use for the material. Its durable. It doesn’t have to be sterile or pure. Apparently 100,000 bags will go into a typical deck.
Having said that I don’t see what’s wrong with incineration if it’s done correctly. It’s not open pit burning, with waste gases going into the environment. It’s high temperature, with additional gas and oxygen to promote more complete burning. And waste gases are filtered.