Discovery and Quantification of Microplastic Generation in the Recycling of Coated Paper-Based Packaging

Microplastics (MPs) are found almost everywhere in the environment and the food chain. The long-term effects of MPs on living organisms are still unclear, so preventing anthropogenic MP generation has become crucial. Fibre-based packaging recycling is investigated here, shedding light on possible MP generation and its consequences. As a typically overlooked source of secondary MPs, cellulosic packaging often consists of thin polymeric coatings that can fragment during recycling. Dispersion coating technology for paper substrates is considered here. The coating formulation was tagged with rhodamine-B and investigated using semi-automatised techniques, including fluorescence microscopy, optical microscopy, and Raman spectroscopy. The results raise concerns as the coating under investigation (8 g/m2) broke into more than 75,000 secondary MPs, whose equivalent diameter and particle count density in the recycled material averaged 75.4 µm and 4.7 particles/mm2, respectively. Wastewater analysis found finer particles (average equivalent diameter: 51.4 µm) with a higher particle count density (6.7 particles/mm2). Overall, 72% of the retrieved particles were smaller than 100 µm. Without proper wastewater screening, such particles (representing 87% in the wastewater filter) may enter the environment, hence representing a hazard for living organisms including humans.