Thermophilic-phase compost materials recycling technology accelerates maturation and enhances pathogen and antibiotic resistance gene removal in pig manure composting

Compost materials, which are rich in numerous functional microbial strains, can serve as natural microbial accelerators during composting. Notably, the strains present in these materials during the thermophilic phase exhibit advantageous traits such as thermotolerance and robust metabolic activity. However, the potential impact of incorporating thermophilic-phase compost materials on the biosafety of animal manure compost remains unclear. This study investigated the reuse of thermophilic-phase compost materials as additives (referred to as GD) in pig manure composting, focusing on their effects on humification efficiency, as well as the removal of pathogens, antibiotics, and antibiotic resistance genes (ARGs). Compared with the control (CK), GD increased the abundance of bacterial genera such as Pseudogracilibacillus , Bacillus , Virgibacillus , Caldibacillus , and Oceanobacillus , enhanced microbial capacities for carbohydrate, amino acid, and energy metabolism, and promoted the activities of various functional enzymes. These changes facilitated organic matter degradation and increased the maximum composting temperature by 13.5 °C. The GD also increased humic acid content, humification index, and germination index by 20.0% ( P < 0.05), 31.2% ( P < 0.01), and 17.8% ( P < 0.01), respectively, and substantially shortened the compost maturation period. The GD significantly reduced the viable counts of Coliforms and Salmonella and decreased the abundance of pathogens, including Clostridium botulinum , Klebsiella pneumoniae , Streptococcus pneumoniae , Escherichia coli , and Pseudomonas aeruginosa . Furthermore, the GD increased the removal rates of tetracycline and sulfonamide antibiotics by 9.28% ( P < 0.05) and 11.1% ( P < 0.01), respectively; concurrently, it reduced the overall abundance of ARGs by 44.0%, and lowered the absolute copy numbers of ARGs and mobile genetic elements by 25.0% and 39.8%, respectively. Adding thermophilic-phase compost materials can improve the fermentation efficiency and product maturity of pig manure compost, and can promote pathogen inactivation and the removal of antibiotics and ARGs by elevating compost temperature and modulating microbial community structure. These findings provide technical and theoretical support for the resource recovery and efficient disposal of pig manure.