Research proves feasibility of post-consumer polystyrene waste as feedstock

Styrenics expert, Ineos Styrolution, recently highlighted the final results of ResolVe, a German government funded research project exploring the recycling of polystyrene.

“The project proves the feasibility of post-consumer waste becoming a valuable feedstock, thus creating a circular economy for polystyrene. The project also included a commercial and an ecological evaluation of the recycling process,” the company stated.

The final report on the ResolVe research was completed by the team, coordinated by Ms. Franziska Nosic, Ineos Styrolution. The report concluded that depolymerisation – an enhanced process breaking polystyrene up into its building blocks – is a very appropriate recycling solution for polystyrene in combination with distillation of the output for further polymerisation. The process promises to produce recycled polystyrene meeting food contact standards.

The research showed that up to 75% of the output can be fed into the purification step and subsequently back into the production of new polystyrene.

Key part of the project was the investigation of waste composition and the effect on styrene yield. This was done in a collaboration between the IKV (Institut für Kunststoffverarbeitung), the Institute for Processing and Recycling (Institut für Aufbereitung und Recycling, I.A.R.) and Neue Materialien Bayreuth GmbH (NMB). The most relevant process parameters temperature, mass flow rate, residence time and vacuum pressure, were systematically permutated and the best process conditions were identified. IKV Aachen transferred these basic process/properties relations to a larger scale and successfully de-polymerised polystyrene to styrene oil. As part of the research, the feasibility of additional processes including steam-cracking of process residues were assessed, together with Ineos O&P as project partner.

The research showed that a stable depolymerisation process is possible with a broad variety of feedstock material. Lightweight packaging and expanded polystyrene (EPS) waste proved to be most suitable feedstock for the depolymerisation process. While the process tolerates polyolefin contamination, a “legacy” flame retardant HBCD (hexabromocyclododecane) could be removed to a large extent, however bromine containing traces remained.

The depolymerisation process not only contributes to the reduction of post-consumer waste and the recovery of valuable resources, a life cycle assessment of the production process for polystyrene revealed that the production with previously depolymerised material requires less energy and produces less CO2 than conventionally produced polystyrene.

Mr. Norbert Niessner, Global R&D/Intellectual Property Director at Ineos Styrolution, noted, “This project has made a dream come true. The results demonstrate that polystyrene and de-polymerisation fit perfectly to the concept of a circular economy.”