Contamination levels in polypropylene waste streams throughout a mechanical recycling process

Abstract Mechanically recycled plastic dominates the recycled plastics market, yet its suitability for food-contact applications depends on effective decontamination. This study provides industrial-scale data on decontamination throughout the mechanical recycling of post-consumer polypropylene from mixed waste and separate collection. Samples were collected throughout the recycling process, standardized into film sheets, and analyzed to track decontamination and identify food-contact-relevant contaminants. Volatile organic compounds (VOC) decreased by 74–80%, with the largest reduction during sample cup production. Elevated washing temperatures promoted VOC release but induced degradation when combined with sodium hydroxide and deinking agent. Linear alkylbenzenes remained high in the separately collected stream and were not fully removed by processing alone. These substances likely originate from offset printing ink or soap packaging. Overall, this recycling process requires further improvement to meet food-contact requirements, and VOC analysis is a suitable tool to guide decontamination optimization and assess the application potential of the resulting recycled material.