Functional biochar and catalytic sustainable biosynthesis of PHA derived from waste activated sludge

Advancing circular wastewater management, this study developed an innovative solution for waste activated sludge (WAS) utilisation by constructing a system in whichWAS wasconverted to biochar and feedback catalysed biosynthesis of Polyhydroxyalkanoates (PHA). After PHA extraction, residual sludge was pyrolysed into biochar, which acted as a catalyst to further enhance PHA production by the self-fermentation conversion of WAS. Biochar significantly improved electron transfer during anaerobic digestion (by 61.36 %) and boosted the proportion of PHA-producing bacteria by 12.33%, resulting in an 81.04% increase in PHA yield, comprising 66.14% of the dry sludge weight. Multi-omics analysis showed that biochar amplified the expression of key PHA synthesis genes (phaA, 4.69-fold;phaB,10.04-fold; andphaC,12.02-fold). This study offers a sustainable approach for WAS management, thereby advancing resource efficiency and providing ecological benefits.