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Evaluating the generation of microplastics from an unlikely source: The unintentional consequence of the current plastic recycling process
Summary
This study revealed that the plastic recycling process itself generates large quantities of microplastics, particularly during the mechanical shredding step. Depending on the plastic type, shredding produced between 7,000 and 29,000 microplastic particles per kilogram of material processed, and weathered plastics generated even more. This is an important finding because it means recycling, which is intended to reduce plastic pollution, may actually be creating a significant new source of microplastic contamination.
This study casts light on the potential of microplastic generation during plastic recycling - an unintended consequence of the process. To date, microplastics have been detected in the wastewater and sludge from plastic recycling facilities; however, generation pathways, factors and minimisation strategies are understudied. The purpose of this study is to identify the factors affecting microplastic generation, namely, plastic type and weathering conditions. The size reduction phase, which involved the mechanical shredding of the plastic waste material, was identified to be the predominate source of microplastic generation. Material type was found to significantly affect microplastic generation rates. Focussing on the microplastic particles in the size range of 0.212-1.18 mm, polycarbonate (PC), polyethylene terephthalate (PET), polypropylene (PP), and high-density polyethylene (HDPE) generated 28,600 ± 3961, 21,093 ± 2211, 18,987 ± 752 and 6807 ± 393 particles/kg of plastic material shredded, respectively. The significant variations between different plastic types were correlated (R2 = 0.88) to the hardness of the plastic. Environmental weathering was observed to significantly affect microplastic generation rates. Generation rates increased for PC, PET, PP, and HDPE by 185.05 %, 159.80 %, 123.70 % and 121.74 %, respectively, over a six-month environmental exposure period. The results in this study confirm production of large amounts of microplastics from the plastic recycling industry through its operational processes, which may be a significant source for microplastic pollution if measures to reduce their production and removal from wastewater and sludge are not considered.
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