Enhancing composting efficiency of horticultural residues through wheat straw addition: Microbial mechanisms driving metabolic heat generation

Sustainable thermal energy can be obtained through crop waste composting, enhancing the application potential of biomass resources. Microbial metabolic heat generation mechanisms during lignocellulose degradation in mixed straw composting were investigated. Four treatments representing different raw material compositions [T1 (Horticultural Residues, HR), T2 (HR + Cow Manure, CM), T3 (Wheat Straw, WS + HR), T4 (WS + CM)] were applied and composted for 36 days. WS addition helped HR composting (T3) prolong thermophilic phase by 49.5 %, achieving 13.0 MJ/kg metabolic heat release and 61.3% organic matter degradation, demonstrating its energy recovery potential. Key microbial taxa, including Pseudoxanthomonas, Thermopolyspora, Chelativorans and Thermobacillus were enriched in thermophilic stage, contributing to lignocellulose degradation through metabolic pathways such as TCA cycle and pentose phosphate pathway. Redundancy analysis showed that high temperature, C/N and pH favored enrichment of dominant microbial communities, accelerating lignocellulosic bio-conversion to metabolites [e.g., D-(+)-maltose and D-ribulose-5-phosphate]. Partial least squares structural equation model confirmed environmental factors, bacterial communities and metabolic activity as key drivers of heat production, and revealed regulation pattern on composting heat production. The findings offer insights into optimizing bio-conversion processes for high-quality energy recovery from HR.