Quinone Structures in Wood Vinegar Modified Biochar Drive Humification and Nitrogen Conservation in Composting.

Composting transforms organic waste into stable humic substances (HS), yet the process is frequently limited by substantial nitrogen (N) loss via ammonia (NH3) volatilization. This research establishes an economical modification strategy using wood vinegar-modified biochar (MB) and elucidates the synergistic biotic-abiotic mechanisms that facilitate humification and N conservation during the co-composting of sheep manure and corn straw. Results indicated that MB significantly decreased cumulative NH3 emissions by 32.56% and 29.88% compared to unmodified biochar (B) and the control (CK), respectively (p < 0.05). Furthermore, the MB group significantly enhanced the humification index (0.79) while lowering the biological index (0.611) relative to the CK (p < 0.05). Molecular characterization via Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) revealed that the MB group contained the highest abundance of CHON formulas (42.7%) and lignin-like structures (73%), confirming the sequestration of N into stable aromatic HS. In addition, metagenomic analysis showed that MB significantly upregulated CAZyme genes associated with lignin degradation while enriching metabolic pathways for quinone biosynthesis (ubiquinone and menaquinol) and amino acid metabolism. These redox-active quinones function as electron shuttles, facilitating the abiotic condensation of amino acids and polyphenols. Ultimately, this study elucidates a novel biotic-abiotic coupling mechanism driven by quinone-mediated electron shuttling, confirming the efficacy of MB for simultaneously mitigating N loss and accelerating humification..