Plastic breaks down is horrible ways and gets everywhere. It's hard to clean well enough to be recycled. Even when recycled it's still constantly breaking down into micro-particles and getting everywhere.

If we can't persuade retailers to use something else I kind of think that the best and cleanest use for single use plastic might be to just incinerate it with a very good scrubber system on the exhaust from the incinerator.

Get the energy back and do something useful with it. e.g. use it as base load for renewable energy sources like wind and solar.

Anything but let it get buried or broken down and into water courses.