Recently there has been an increased interest in the circular economy of plastic with chemical recycling. Chemical recycling is broadly defined as any process by which a polymer is chemically reduced to its original form so that it can eventually be repolymerized and remade. The outputs can be virgin-like plastics, specialty chemicals, monomers, fuels and other products. Chemical recycling, also known as advanced recycling and recovery or transformational technologies, is used exclusively in post-consumer plastics, the most difficult and abundant group of plastics to recycle. The most used process of mechanical recycling (think shredders, granulators, pelletizers) does not change the structure of the plastic so it must be cleaned and sorted, shredded and re-pelletized. Chemical recycling either dissolves the plastic with chemicals or uses heat (pyrolysis) to break down the plastic to its original structures.
Categories of advanced recycling technologies include:
- Purification- dissolving used plastics in a solvent to remove additives
- Decomposition/depolymerization – breaking the molecular bonds of used plastic resulting in monomers
- Conversion – breaking and recombining the molecular bonds of used plastic in a process that is similar to oil refining.
In the process of making mixtures, hydrocarbons referred to a naphtha that is used in plastic production is cracked to produce lighter hydrocarbons and ultimately to compounds including those need to plastic monomers. Naphtha is the goal for most chemical recycling facilities operating in the world today.
There are several companies that are making the process work in plastics that are too contaminated for traditional recycling. Plastics Energy has two plants in Spain that process around 15 tons per day of post-consumer plastics. They take polyethylene, polystyrene and polypropylene that would have been land filled or incinerated and make it reusable. One of the benefits of advanced recycling is that the process completely cleans the product of contaminates which allows it to be used in medical and food applications.
Here at Arlington machinery, we have seen advanced recyclers become a new market for our equipment. In the last few months, we have provided (3) 6” Extruders and a Gala Pelletizer to chemical recyclers to use in their advanced recovery operations. One company thermo-catalytic process to produce industrial waxes and products from 100% post-consumer scrap.
Advanced recycling is not without its detractors. According to some experts, current technology causes almost halve of the carbon in the plastic to be lost as the plastic is converted to gas or oil. The viability for all end-products remains to be seen. The most advanced chemical recovery efforts to produce more plastic yield very little results. As of now the process cannot deal with mixed plastics or black plastic and current market conditions make it difficult to compete with virgin resin.
Advanced recycling is not going to replace mechanical recycling completely, but future technology will have it work in tandem with mechanical recycling. By taking the most difficult plastics, the ones difficult to sort and process mechanically, and making them recyclable, advanced recycling s is a great contribution to the circular economy of plastics.