An overview of non-biodegradable bioplastics

Bioplastics have introduced numerous flexibilities to humankind. However, bioplastics have brought newer challenges in waste management. Approximately half of the current bioplastic market is not biodegradable, and with a larger market volume, its end-of-life allocation will be problematic for the governments and policymakers. This study aims to provide an overview of the non-biodegradable bioplastics market, including their underlined challenges, typical production methods, characterization, and possible alternative waste utilization perspective. Bioplastic production usually starts from a biological source i.e., biomass and a series of modification techniques such as pretreatment, hydrolysis, and fermentation are carried out to produce bioethanol. Then, bioethanol is converted to non-biodegradable bioplastics. The major non-biodegradable bioplastics are bio-polyethylene (bio-PE), bio-polypropylene (bio-PP), bio-polyethylene-terephthalate (bio-PET), bio-polytrimethylene terephthalate (Bio-PTT), and bio-polyamide (bio-PA). In this review article, an overview of each bioplastic is presented with flow diagrams. Also, the production method of compostable bioplastics—polylactic acid (PLA) — is briefly discussed for comparison purpose. Since the chemical structure of bio-based non-biodegradable plastics is similar to the conventional fossil-based plastics, the characterization and alternative thermochemical utilization techniques of five bioplastic wastes are discussed based on the conventional plastics characterizations. Per ultimate analysis, considering high hydrogen, low oxygen, and low fixed carbon content, bio-PE and bio-PP are recommended as potential feedstocks for the catalytic pyrolysis process to produce gasoline and diesel range liquid hydrocarbons. Alternatively, bio-PET, bio-PA, and PLA are recommended as potential feedstocks for the gasification process, considering their higher oxygen content.