• • High C/N (≈28.0:1) with nitrogen-rich wastewater reuse (HRN) cut cumulative N2O emissions by 53.38% and NH3 by 62.15% versus low C/N reuse (LRN), directly mitigating odor and greenhouse gas release in composting operations.
• • HRN increased final compost nitrogen content to 4691.27 mg/kg, 3.9% higher than HRW (4514.96 mg/kg), demonstrating enhanced nitrogen conservation and fertilizer value under carbon-sufficient conditions.
• • Low C/N (≈20:1) with nitrogen-rich wastewater reuse (LRN) exacerbated NH3 and N2O emissions by 26.43% and 112.99% respectively versus LRW, highlighting carbon limitation as a critical operational threshold for nitrogen recycling.
• • All treatments achieved pH (8.17–8.48) and GI (90.85%–122.96%) within national organic fertilizer standards, confirming that nitrogen-rich wastewater reuse does not compromise final compost maturity when C/N is managed.