Microbial succession and degradation during kitchen waste biodrying, highlighting the thermophilic phase

[Display omitted] •Kitchen waste biodrying used a compound stone amendment to partially replace sawdust.•Biomarker analysis and KEGG prediction highlight the role of the thermophilic phase.•Thermophilic phase inactivated pathogens, potentially improving nutrient metabolism.•After biodrying, microbial richness rebounded, including pathogenic microorganisms.•The new amendment improved biodrying so the product can be used as biofuel. Biodrying in conjunction with compound stone amendment was used to treat kitchen waste, which improved biodrying. After 16 days, the pile moisture content decreased from 68.8% to 23.0%. Lignin, cellulose and hemicellulose concentrations decreased from 104.6 mg g−1 d.b., 322.9 mg g−1 d.b. and 155.9 mg g−1 d.b., respectively, to 74.0 mg g−1 d.b., 224.8 mg g−1 d.b. and 134.5 mg g−1 d.b., respectively. The Shannon index for bacteria increased from 2.5 to 3.1, while for fungi, it decreased from 4.6 to 0.6. The relative abundances of Amino Acid Metabolism and Carbohydrate Metabolism exceeded 7%. The thermophilic phase during the process inactivated the pathogenic microorganisms, increased the bacterial diversity, decreased the fungal diversity, and potentially improved the metabolism of nutrients, including amino acids, carbohydrates, lipids and vitamins. The biomarker analysis and predicated protein sequences provide genetic evidence to elucidate why the thermophilic phase is the peak time for nutrient metabolism.