Bioplastics: an examination of variety, degradation, and environmental effects

Abstract There is considerable confusion about ‘bioplastics.’ They are often touted as ‘greener’ than conventional plastics and may be claimed to be biodegradable and compostable. However, there are a great variety of different products claimed to be bioplastics, and they differ greatly in many characteristics. In this review, we discuss the large diversity of bioplastic products derived from biological materials and compare their various physio-chemical characteristics with conventional (petroleum-derived) plastics. We define a number of terms that are often confused or ambiguous. We examine the biodegradability of different bioplastics in various environments (e.g. higher or lower temperatures, composting, soil, freshwater, seawater) and the byproducts (e.g. chemicals, microplastics) that they may release during degradation. In addition, we review studies that evaluated the toxicity of the products released, including toxicity to cell lines and bacteria, to plants, and to terrestrial and aquatic animals. Many studies have compared toxicity of bioplastics with conventional plastics. The diverse bioplastics differ greatly in toxicity. Furthermore, toxicity test methods employed have been varied—some studies have tested solid pieces of plastic, some have used microplastics generated from the bioplastic, and some have used plastic product leachates. The reviewed studies have used different conventional plastics to compare bioplastics with. Many studies found that the bioplastics were more toxic than the conventional plastics. Therefore, it is impossible to draw any overall conclusions that ‘bioplastics’ as a group are more or less toxic than conventional plastics, but it would be incorrect to conclude that they are in general more ‘environmentally friendly.’