The proper way to dispose of plastic is in an incinerator, as is commonly done in the EU. Regular old polyethylene burns cleanly and easily.
Do you know what's actually dangerous to the environment? These new "paper" alternatives which are often coated in PFAS chemicals -- which cannot be safely mulched or incinerated because they are "forever" chemicals.
Just use regular plastics please, and burn them. It's by far the most environmentally friendly solution.