What are the different technologies that are generally considered to be chemical recycling?
Although there are several new and promising technologies, chemical recycling technologies currently fall generally within one of three primary process categories:
Dissolution (Purification): Dissolution processes use a solvent and low heat to extract color or additives from a single-polymer feedstock, or target polymers from mixed plastic materials. Dissolution techniques do not change the polymer structure of the target plastics, using physical (i.e., mechanical) recycling technologies but with the addition of chemical solvents.
Depolymerization: Depolymerization processes take a single-resin feedstock and partially or fully break the polymer bonds using a solvent to generate monomers or oligomers. There are also several sub-categories, depending on whether the depolymerization process is primarily thermal, chemical, or a mixture of the two.
Conversion: Conversion technologies are the most studied chemical recycling techniques. These processes typically involve the thermal breakdown of the waste plastics in an oxygen-starved and combustion-free reactor, maintaining carbon in the final products of the conversion reaction (char, liquid oil, light gases and syngas) rather than releasing carbon as carbon-dioxide. These processes can also include catalytic steps to convert the liquid oil and syngas to select chemical products.
These chemical recycling technologies produce different outputs, ranging from chemicals and monomers, to waxes, syngas, and mixed hydrocarbons, as shown in this chart:
