Has anyone given serious thought to breaking plastics back into their base components (monomers) and re-forming these into new products? For example, 'cracking' PE (poly-ethylene) into ethane, then re-polymerizing the gas into Propane? Sure, it's not cost-effective, except for removing all present and future plastics from landfills and the oceans, and returning it to the manufacturers. I could see oil companies investing in this tech too.
This is an active area of discussion and investment, though as you point out the power consumed in fuel production could offset the benefits. Pyrolysis is the most common form of plastic-to-fuel conversion.
Here are a couple stories to start: