Carbon-Stimulated Bioaugmentation Enhances Thermogenesis, Lignocellulose Degradation, and Humification in Low-Temperature Cattle Manure Composting

Low ambient temperatures severely restrict the start-up efficiency and microbial bioconversion of livestock manure during aerobic composting. To overcome this “cold-start” barrier, this study investigated the coupled effects of an easily accessible carbon source (molasses) and functional microbial inoculants (Streptomyces griseorubens JSD-1 and Paenarthrobacter nitroguajacolicus LDT1-8) on cattle manure composting. Results demonstrated that the combined strategy significantly expedited thermogenesis, achieving a peak temperature of 62.1 °C and extending the thermophilic phase (>50 °C) by 2 days. This enhanced microbial activity accelerated organic matter stabilization, increasing cellulose and hemicellulose degradation by 44.0% and 49.3%, respectively, and boosting humic acid content by 33.4% in treatment T7 (molasses + JSD-1 + LDT1-8). Amplicon sequencing revealed that the amendments reshaped microbial community structure, selectively enriching lignocellulose degradation and humification-driving taxa (e.g., Actinobacteriota and Mycothermus), leading to a more robust and modular metabolic network. Redundancy analysis confirmed that this directed succession was primarily driven by organic matter degradation and humic fraction accumulation. Overall, the combined application of molasses and microbial inoculants promoted temperature rise, lignocellulose degradation, and humification by reshaping microbial community structure, providing an effective strategy for improving cattle manure composting efficiency under low-temperature conditions.