Persulfate-driven sludge biorefinery toward value-added medium-chain fatty acids

), significantly enhancing its bioavailability during anaerobic fermentation. Integrated metagenomic functional annotation and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) revealed that EPS-derived DOM reshaped the microbial metabolic network, stimulating glycolysis, amino acid metabolism, and carbon chain elongation. Moreover, the formation of unsaturated and aromatic-like fermentation products indicated enhanced DOM humification, which facilitated carbon chain elongation and microbial metabolic activity. Life cycle assessment and techno-economic analysis confirmed the environmental sustainability and economic feasibility of this radical-driven strategy. By elucidating the radical-EPS-DOM-metabolism cascade, this study provides mechanism-guided strategies for efficient sludge biorefinery, advancing the field from empirical operation toward targeted, high-efficiency design.