Plastics Recycle, Degrade, or Burn

There are forms of recycling that are less familiar —in that they do not directly recycle the materials into new artifacts. Tertiary recycling breaks down the plastic to its component monomers, which can be repolymerized. This requires pyrolysis of the materials, sometimes called thermal cracking, and is most easily accomplished with step growth polymers such as polyamides and polyesters but is also possible for poly(methyl methacrylate). The processes require specialized plant, so are capital intensive, and a large-scale operation is necessary for economic viability. 

For those of you interested in vintage TV, the first episode of a British series called Doomwatch featured just such an eventuality. This was novelized 2l Mutant 59 The Plastic Eater, by Kit Pedler (inventor of the Cybermen, in Dr Who) and Gerry Davis. 

---