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 large number of different products claimed to be bioplastics, and they differ greatly in many characteristics. In this review, we discuss the great variety of bioplastic products derived from biological materials and compare their various 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 this process. 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 compare bioplastics with conventional plastics. The diverse bioplastics differ greatly in toxicity. Furthermore, toxicity test methods employed have been very different from one another – some have used solid pieces of plastic, some have used microplastics generated from the bioplastic, and some have used plastic product leachates. Different studies compare them with different conventional plastics. Many bioplastics are more toxic than the conventional plastics they were compared with. Therefore, it is impossible draw any overall conclusions that “bioplastics” as a group are more or less toxic than conventional plastics, but it would be an error to conclude that they are more “environmentally friendly.” Evaluation of bioplastics is much more complex than many assume.