Recycling and revalorization of PLA and PHA-based food packaging waste: A review

Poly(lactic acid) (PLA) and poly(hydroxyalkanoates) (PHAs) are the most significant biodegradable polymers in terms of their increasing global industrial production capacities with the aim of replacing petroleum-derived food packaging materials. The latter are well known for their environmentally polluting nature. This paper aims to review the diverse technologies related to the recycling and revalorization of single-use food packaging materials based on PLA and PHAs (e.g. chemical depolymerization, solvolysis, mechanical recycling (mechanochemistry), enzymatic hydrolysis, fermentation, gasification and hybrid approaches), as well as to address an important issue for plastic materials manufacturers as is the reprocessing of residual materials obtained during the manufacturing of food packaging. The latter is aimed at reducing waste and increasing the economic sustainability of the materials and the business. Mechanical recycling (mechanochemistry) is recommendable with the aim of reducing waste and increasing the sustainability of residual materials obtained during the manufacturing of industrialized biodegradable food packaging based on PLA and PHA. In contrast, chemical (chemical depolymerization and solvolysis), enzymatic and fermentation recycling is recommendable to treat discarded single-use food packaging materials made from PLA or PHA, thus yielding chemical precursors (monomers) and fuels, which can then be used as feedstocks to produce their corresponding recycled/renewed polymers or copolymers, thereby diminishing the need for new chemicals. Finally, the gasification process is currently representing an interesting perspective for connecting hybrid recycling approaches between the use of chemistry and bioprocesses, and not merely obtaining synthesis gas as a precursor of monomers, copolymers and/or recycled/renewed biodegradable polymers.