Mechanical Recycling: The Established Method
Mechanical recycling physically processes material without changing its chemical structure. Plastics are shredded, washed, melted, and reformed into pellets that can be used in manufacturing new products.
Mechanical recycling is relatively energy-efficient, well-established, and cost-competitive for high-quality input streams. Its limitation: it works best on clean, sorted, single-resin plastics. Mixtures of different resin types, contamination, and degradation from previous use cycles reduce output quality. After several mechanical recycling cycles, plastic fibers shorten and the material degrades — it can't be recycled infinitely.
Chemical Recycling: The Emerging Method
Chemical recycling (also called advanced recycling or molecular recycling) breaks polymers down into smaller molecules using heat (pyrolysis), dissolution (solvent-based), or catalysts (gasification, hydrocracking). The resulting monomers, oils, or gases can be used as feedstock to produce new plastics or fuels.
Because chemical recycling works at the molecular level, it can theoretically handle mixed plastics, contaminated feedstocks, and plastics that can't be mechanically recycled — including multilayer packaging and mixed polymer streams.
The Energy Question
Critics of chemical recycling point to higher energy inputs compared to mechanical recycling. Breaking and reforming chemical bonds requires more energy than melting and remolding. For pyrolysis-based processes that produce fuel rather than new plastics, some analysts question whether the lifecycle emissions are truly better than virgin production.
Proponents argue that energy efficiency is improving as the technology matures, and that the ability to handle previously unrecyclable materials justifies the energy premium when the alternative is landfill.
Complementary, Not Competing
The emerging consensus is that mechanical and chemical recycling are complementary. Mechanical recycling handles high-quality, sorted streams economically and efficiently. Chemical recycling handles the difficult residual streams that mechanical recycling can't process.
A well-designed recycling system would use mechanical recycling for clean, sorted material and chemical recycling as a secondary system for mixed or contaminated material that would otherwise go to landfill.