Towards scaling-up implementation of polyhydroxyalkanoate (PHA) production from activated sludge: Progress and challenges

Polyhydroxyalkanoate (PHA) is a biodegradable biopolymer synthesized from renewable resources, providing sustainable and eco-friendly plastics. The utilization of activated sludge for PHA production has gained prominence due to its cost-effectiveness and abundant availability. Upscaling PHA production from activated sludge can contribute to waste management and resource recovery simultaneously, thereby reducing the dependence on petroleum-based plastics. This review critically examines the progress and challenges in this field, while offering valuable insights into strategies for enhancing productivity, improving product quality, and reducing costs. The analysis primarily focuses on identifying key factors influencing each stage of the three-stage process aimed at increasing productivity. Noteworthy strategies proposed include optimizing the enrichment process and feast/famine ratio. For high-quality PHA, the emphasis is on oriented acid production, and the selection of appropriate extraction methods is crucial. The review also addresses cost reduction, discussing the simplification of the process through the two-stage process, and integration of nitrogen removal with PHA production. Future research directions are outlined, highlighting the optimization of PHA quality, scalability of production, development of efficient extraction methods, assessment of environmental impacts, and alignment with policy measures. Conclusively, activated sludge-based PHA production shows great promise and necessitates further research and development for industrialization.