Polyhydroxyalkanoate as Next Generation Bioplastics for Sustainability and Circular Energy Management
The concurrent crises of plastic pollution, climate change, and resource scarcity demand innovative biotechnological solutions. This review explores an emerging paradigm to produce polyhydroxyalkanoate (PHA) bioplastics using wastewater sludge (WWS) as a primary feedstock. WWS is a complex yet globally abundant waste stream rich in organic carbon and nutrients, making it a promising and cost‐effective substrate for sustainable PHA production. We discuss metabolic engineering strategies designed to transform mixed microbial cultures into robust and well‐characterized industrial PHA producers, including the heterologous expression of key PHA biosynthesis genes such as phaCAB . Direct PHA synthesis on sludge‐derived media is a promising, integrated approach to waste management and sustainable production, transforming WWS from a treatment‐focused service into a resource‐recovery as bioplastics. This review critically evaluates the key challenges associated with this strategy, including process scalability, optimization of PHA yield, downstream processing, sustainability, and integration within circular bio‐systems. Conventional WWS management emits ~0.3–1.5 kg CO 2 ‐eq/kg PHA dry sludge, whereas life cycle assessments (LCAs) framework indicates that PHA production from WWS results in emissions of approximately ~1.5–3.5 kg CO 2 ‐eq/kg PHA produced. Compared with ~3.5–6.5 kg CO 2 ‐eq/kg PHA fossil‐based plastic replaced on a cradle‐to‐grave basis. When avoided WWS disposal and fossil plastic substitution are considered, WWS‐derived PHAs production has the potential to deliver net climate benefits within a circular‐economy framework. image