Oxy-biodegradable plastics in freshwater environments: degradation and biofouling

Abstract

Growing concern about the impact of plastic pollution on the environment has led to the creation of global public policies and the consumption of “environmentally friendly” products, such as oxy-biodegradable plastics. In this context, “greenwashing” practices can arise, i.e., the product promises more environmental benefits than it actually offers, which can lead to superfluous use, inappropriate disposal, and the generation of microplastics (MPs). However, the scientific literature lacks studies that evaluate the behavior of oxy-biodegradable plastic when exposed to the freshwater environment. In this respect, the aim of the current study was to evaluate the degradation process of oxy-biodegradable plastic bags made from high-density polyethylene (HDPE) in river water. To this end, the current study aimed to assess whether these bags actually meet the label information (which corresponds to the complete degradation of material) or whether they correspond to greenwashing practices. The physical and chemical alterations, and the formation of biological communities that occurred on the surface of the plastic material when exposed to natural aging and submerged in freshwater were monitored using mid-infrared absorption spectroscopy with attenuated total reflectance (FTIR-ATR) and scanning electron microscopy (SEM). The characterization of the samples after 180 days of exposure showed that the oxy-biodegradable bags were not completely degraded, with only fragmentation of the material and generation of MPs. In addition, it was also observed that microorganisms present in the water easily colonized the plastic surface from the start of the experiment. In this way, the oxy-biodegradable bags analyzed correspond to a greenwashing practice, which is extremely harmful, since it can influence the increase in consumption of these products, generating greater improper disposal of these materials, and consequently the generation of MPs and the formation of biofilms, which can carry pathogenic microorganisms to the aquatic biota and to humans.