Upcycling of Commercial Biobased Polyester Bioplastics─Turning Used or Spoiled Materials into Added-Value Products

Bioplastics incorporate different renewable sources via direct biosynthesis or biotechnological intermediates, contributing to the eventual production of a biobased system. Sustainable polymers and materials represent an essential substitute for petrochemical intermediates and the synthesis of applied compounds. We listed, described, and discussed three main groups of commercially applied and produced bioplastics: polyhydroxyalkanoates (PHAs), polylactic acid/polylactide (PLA), and polybutylene succinate (PBS). Although all the mentioned biobased polymers possess biodegradability at specific conditions, their waste or spoiled primary products have significant potential for new and diverse applications. The thermally degraded, hydrolyzed, or physically aged biopolyesters lack sufficient performance in their initial applications; upcycling is an alternative and promising strategy that produces valorized, added-value products or complex multistep-derived functional systems. This comprehensive review describes the major challenges that the discussed biobased polymers face, identifies fundamental chemical approaches for bioplastics as entering substances, and outlines the potential and outlook for the waste-based molecules and precursors produced. The eventual alternative applications include the pharmaceutical industry, the cosmetics segment, the production of chemical intermediates and reactants for organic synthesis, and various functional and circular materials, such as recyclable thermoplastics and thermoset vitrimers.