Heterogeneous coal gangue-driven humification in manure co-composting: core microbial functional coupling and...

Co-composting coal gangue (CG) with manure addresses dual waste challenges, but microbial mechanisms driving humification in heterogeneous CG-manure co-composting remain unclear. This study investigated how CG differentiated by particle size and carbon content affected the humification process and microbial communities. All treatments reached maturity by day 44, with high-carbon CG (CGH) showing better maturity than large-particle CG (CGL): higher GI (88-92 % vs 86-88 %), lower C/N (14.96-15.21 vs 17.74-17.97), better NO₃^--N retention (7.32-7.80 vs 5.91-6.83 g/kg), and more HA accumulation (91.46-112.58 vs 72.79-88.72 g/kg). CGH had a prolonged thermophilic phase, continuous EC decrease, and efficient precursor accumulation and transformation, potentially contributing to improvement of humification. Network analysis indicated that CGL promoted higher microbial diversity and larger network scale, whereas CGH displayed tighter intra-taxa interactions and more prevalent synergies. CGH possessed more core taxa (43 in CGH vs 34 in CGL) and facilitated the enrichment of functional microbe (e.g., Planifilum) associated with recalcitrant carbon decomposition and HA synthesis. Correlation analysis showed that core taxa and precursors in CGL exhibited higher individual contributions to HA synthesis. However, the correlations and combined contributions among abundant core taxa, rare core taxa, as well as their associations with precursors and HA synthesis were stronger in CGH. These results suggested that CG types adopted distinct regulatory pathways during humification, and the efficient functional coupling among core taxa, precursors, and humic components driven by CGH was likely pivotal for accelerating humification. This study provides novel strategy for CG-manure management and elucidates CG heterogeneity driving humification via microbial-precursor interactions.