Degradation of thermoplastic cellulose acetate-based bioplastics by full-scale experimentation of industrial anaerobic digestion and composting

Abstract

The ability of full-scale industrial plants to degrade bioplastics waste must be verified to exclude any negative effects on the quality of the process outputs. This study aims to assess the degradation of two thermoplastic cellulose acetate-based bioplastics, in pure and composite forms in both Anaerobic Digestion (AD) and Composting (C) industrial conditions. The main degradation occurred during AD, where a disintegration of about 36% and 50% was achieved from pure and composite thermoplastic cellulose acetate, respectively. The disintegration during C did not exceed 20% for both samples. The combined process resulted in a slightly higher degradation (58–40%) than that obtained in AD, revealing how the main alteration of samples occurred in an anaerobic environment. Despite this macroscopic degradation, the samples showed only minor superficial degradation as highlighted from SEM analysis. FT-IR spectroscopy, TGA andDSC analyses showed that the biodegradation mechanism involved mainly the plasticizer loss and deacetylation of the cellulose matrix, with only partial degradation of cellulose backbone However, both deacetylation and degradation were favored in AD and AD + C processes and from the presence of filler in anaerobic conditions. These results demonstrated how the degradation obtained on an industrial scale can differ significantly from those obtained in the laboratory scale, especially for pure thermoplastic cellulose acetate. Furthermore, current industrial AD and C process resulted not optimized for the treatment of thermoplastic cellulose acetate-based bioplastics. Hence, this works could help waste facilities managers to process emerging materials such as bioplastics in a more sustainable way.