Enhancing the biodegradation of (bio)plastic through pretreatments: A critical review

As plastic packaging becomes nearly indispensable in the plastic economy, rigorous efforts have been made to recapture the material value form this waste stream, which is mostly composed of highly resistant plastics. Biodegradation offers an attractive alternative for conventional plastic waste treatment as this approach is environmentally friendly, has low cost and facilitates valorisation. Moreover, there is also an increasing interest in plastic pretreatments waste to enhance biodegradation. This review investigates the pretreatment methods that optimise plastic biodegradation by examining the process's mechanisms and key influencing factors, which can be categorised into: biotic factors, abiotic factors and polymer characteristics. Various types of chemical and physical pretreatments have demonstrated to effectively enhance biodegradation through oxidation and surface changes on the plastics, leading to increased bioconversion rates and biogas production. A critical evaluation of the various categories of pretreatment methods is presented. This evaluation leads to the conclusion that the category of non-thermal physical treatments is most promising, due to the relatively low energy requirements and the absence of a need for chemical additions. Moreover, non-thermal physical treatments have demonstrated application potential at large scale. Based on these conclusions, pretreatments are expected to be an integral part of the biodegradation of plastics within a circular economy approach.