Bioplastics in the circular bioeconomy: Production pathways, biodegradation mechanisms, and environmental implications

The escalating environmental burden caused by conventional petroleum-based plastics has intensified global efforts to develop sustainable material alternatives. Bioplastics have emerged as a promising solution due to their renewable origin, potential biodegradability, and compatibility with circular bioeconomy principles. Unlike conventional plastics, bioplastics are designed to integrate material production, use, recovery, and degradation within biologically driven cycles that minimize waste generation and environmental impact. However, the sustainability of bioplastics depends not only on their production from renewable resources but also on their end-of-life behavior, particularly microbial biodegradation and environmental fate. This review provides a comprehensive and critical synthesis of bioplastics within the framework of the circular bioeconomy, with emphasis on production pathways, microbial biodegradation mechanisms, and environmental implications. Major classes of bioplastics, including natural biopolymers, microbially synthesized polymers, and synthetic bio-based biodegradable plastics, are discussed in relation to feedstock sources, manufacturing technologies, and material properties. The role of microorganisms in bioplastic degradation is examined in detail, highlighting key microbial taxa, enzymatic systems, and metabolic pathways involved in polymer depolymerization and assimilation. Environmental performance, including degradation behavior in soil, compost, freshwater, and marine ecosystems, is critically evaluated alongside potential risks such as incomplete degradation and microplastic formation. Finally, challenges, knowledge gaps, and future perspectives for advancing bioplastics toward truly circular and sustainable material systems are discussed. This review aims to support the development of scientifically informed strategies for bioplastic design, waste management, and policy implementation within a circular bioeconomy framework.