Just implement better recycling programs, and develop better technology for recycling (so "contamination" isn't a problem, etc.). This might not work so well for societies where it's socially acceptable to just throw your trash on the ground and have trash littering the landscape though.
If no new plastic was available, maybe we could recycle better, but at a very high energy cost. Even Japan, famous for its recycling where end users clean and sort their plastic in great detail, burns a lot of their plastic for energy.
Not all plastics can be recycled and there may not be any financial incentive to do so. Most paper in my state that goes into the curbside recycle bin ends up in the trash.
Recycling is hard because different plastic molecules don’t always play nice together - and the same goes for metal.
So you need to sort everything carefully. This is hard, slow, and way too imperfect.
I wonder if a better approach could one day be to burn it and then use some future catalyst or reaction to convert the smoke into something useful, or to chop the raw plastic up and feed it to a vat ful of special bacteria.
Yeah, that's why I said we should develop better recycling technology, because what we have today isn't that good. The bacteria idea is a good one I think. We already have microorganisms that can eat plastic, so it seems like it should be possible to genetically-engineer better plastic-eating bacteria for this purpose.
Just don’t let them loose!
We have lots of buried plastic pipes and cables.