ASSESSMENT OF MATERIAL COMPOSITION AND COLOR DISTRIBUTION IN POST-CONSUMER POLYPROPYLENE BALES

In order to meet the recycling targets according to the Packaging and Packaging Waste Regulation (PPWR) within a circular economy framework, a comprehensive understanding of the input stream is essential. The input stream for plastic waste recycling, commonly delivered as compressed plastic bales, vary in composition and quality due to the heterogeneous composition of the stream. These bales contain the targeted polymer fraction as well as amounts of foreign polymer contaminants and non-plastic contaminants that significantly influence the recycling process and recyclate quality. This study focused on rigid post-consumer polypropylene (PP) bales, assessing both material composition and color. PP is one of the most commonly used polymers in consumer packaging. The bales consist of food packaging, such as yoghurt cups, ice cream, or butter containers as well as non-food packaging, such as flower pots. The input materials, processed into shredded flakes, were sorted by material type using a portable near-infrared (NIR) sensor. The flakes were divided into rigid polymers, including PP, polyethylene, polystyrene, and polyamide as well as flexible polymers, aluminum, non-detectable components (e.g., black particles), and other materials (e.g., wood). Moreover, the rigid PP fraction was manually classified by color (transparent, white, red, green, and blue). The study showed that 80-90% of the investigated input samples consist of rigid polypropylene. Color sorting revealed that approximately 40 % of the rigid PP fraction was transparent. White rigid PP comprised around 30%. A detailed analysis of the plastic input stream enables an optimized recycling process that leads to an improved recyclate quality and reduced material loss. This supports regulatory compliance and enhances overall recycling efficiency and sustainability.