Wikipedia: In chemical recycling, also called feedstock recycling or tertiary recycling, polymers are reduced to their chemical building-blocks (monomers), which can then be polymerised back into fresh plastics. In theory, this allows for near infinite recycling; as impurities, additives, dyes and chemical defects are completely removed with each cycle. In practice, chemical recycling is far less common than mechanical recycling. Implementation is limited because technologies do not yet exist to depolymerise all polymers reliably on an industrial scale and also because the equipment and operating costs are much higher.

Wikipedia: Mixed plastic waste can be depolymerised to give a synthetic fuel. This has a higher heating value than the starting plastic and can be burnt more efficiently, although it remains less efficient than fossil fuels. Various conversion technologies have been investigated, of which pyrolysis is the most common. Pyrolysis of mixed plastics can give a fairly broad mix of chemical products (between about 1 and 15 carbon atoms) including gases and aromatic liquids. Catalysts can give a better defined product with a higher value. Compared to the widespread use of incineration, plastic-to-fuel technologies have historically struggled to be economically viable because of the costs of collecting and sorting the plastic and the relatively low value of the fuel produced.