Ultrahigh‐temperature composting of sewage sludge with novel inoculant: Process performance and microbial dynamics

Abstract Ultrahigh‐temperature aerobic composting is a promising approach for rapid stabilization of municipal sewage sludge. In this pilot‐scale study, sewage sludge was co‐composted with sawdust, wheat bran, and dried chicken manure in a 2.3 m × 0.6 m × 1.0 m reactor under continuous aeration (0.035 m 3 ·(m 3 ·min) −1 ) for 27 days. The system rapidly reached temperatures above 75°C during the thermophilic phase. Organic matter decreased steadily, while ammonium nitrogen declined and nitrate accumulated during later stages, indicating sequential nitrogen transformations. Compost maturity improved significantly, with the germination index exceeding 90% and an increased humic‐to‐fulvic acid ratio. Microbial analysis showed temperature‐driven succession with Firmicutes dominating the thermophilic stage. Overall, the results demonstrate that ultrahigh‐temperature composting can effectively stabilize sewage sludge at pilot scale.