In a collaboration between several members of The National Platform Chemical Recycling from TNO, Utrecht University, University of Twente and ECN, part of TNO, a perspective on the future of chemical recycling was published in the scientific journal Angewandte Chemie and is available open source. This review article titled “Beyond Mechanical Recycling: Giving New Life to Plastic Waste” summarizes the available and emerging chemical recycling techniques and assesses their carbon footprint via a Life Cycle Analysis. This is complemented by an overview of companies that are active in the field of chemical recycling or recently started activities.
Chemical recycling technologies are necessary to complement the only technique that is already used for recycling of polymer waste, mechanical recycling. Current plastic recycling rates are very low, because mechanical recycling can only address certain types of polymers (PP, PE, PET), while others like PU cannot be recycled this way. In addition, the plastics have to be sorted extremely well before. Otherwise, the process yields a plastic with much degraded properties, i.e. causing brittleness. A rather unappealing color cannot be avoided in any case and potentially toxic additives remain, making food grade applications impossible and leading to the main use of these recycling products in flower pots, shampoo bottles or garden chairs to name a few. As chemical recycling allows for the full reversion to chemical building blocks in the case of pyrolysis, monomers in the case of solvolysis and clean polymers without additives in the case of dissolution/precipitation, it can have great benefits over mechanical recycling.
It is concluded that a combination of several technologies will be necessary to achieve circularity for polymers, since all methods exhibit strengths and weaknesses. While pyrolysis can take rather mixed plastic waste streams with low amounts of PVC and PA, producing a rather low value mix of hydrocarbons, solvolysis and dissolution/precipitation potentially yield a higher value product but can take only very pure monostreams of certain types of polymers. CO2 savings are highest with the latter two, while all chemical recycling techniques as well as mechanical recycling are advantageous over incineration with energy recovery. Emerging methods, with a very low technology readiness level are covered as well aiming to inspire novel ideas that go beyond more extensively researched techniques like pyrolysis and to highlight possible solutions for overcoming drawbacks of and difficulties with these technologies.