Recycling plastic would be the best way to eliminate plastic waste. Funny you asked this question they say that God created us because the earth could not produce plastic. Not too funny, but the sad reality is that plastic is crap. Literally it is the waste byproduct of oil processing, nasty stuff.
On the topic of God if you are aware of what is going on in America it would appear that God has a fix for the plastic problem. They say Yellowstone is a super volcano and it is so threatening to the world. Yellowstone is just a small part of the ring of fire which appears to right now as I write this ancient dormant volcanoes are waking up.
A chain of volcanoes from Canada through America and Yellowstone all the way down through Mexico and out to sea. Thousands of volcanoes, tens of thousands. So in theory magma would eliminate the waste a new crust will wipe out any proof we were ever here. That would do the trick as to the best way to get rid of plastic.