Microplastics Release from Conventional Plastics during Real Open Windrow Composting

Abstract

The recycling of bio-waste plays an important role in a circular economy as it transforms bio-waste into a valuable resource (organic fertilizer). However, even separately collected bio-waste can contain some plastic waste, which is usually separated after composting and not before it. Primary studies have confirmed the degradation of plastic during composting, but the release of microplastics from them has not been studied. This article presents a quantification and comparison of the release of microplastics from commonly used plastics during green waste composting. Microplastics were identified by Nile red staining and examination under a fluorescent microscope. Plastic degradation was assessed by weight loss calculation, scanning electron microscope (SEM), and Fourier-transform infrared spectroscopy (FTIR) analysis. On average, 17 to 52 microplastics’ are released from 5-by-5 cm pieces of conventional plastics during composting. The control polylactic acid sample showed the smallest amount of released microplastics: four particles on average. The number of released microplastics depended on the polymer type and thickness of the samples. The results of the current article can be further used for the prediction of microplastic generation and setting a limit on the plastic content in bio-waste.