Effect of excess sludge and food waste feeding ratio on the nutrient fractions, and bacterial and fungal community during aerobic co-composting

[Display omitted] •Mass ratio of 1:1 excess sludge and food waste was beneficial to nitrogen fixation.•Larger proportion of excess sludge was conducive to accumulation phosphorus.•Ascomycota accounted for the highest at the mass ratio of 1:1 pile.•The 1:1 composting pile was conducive to the degradation of cellulos. The effect of excess sludge and food waste feeding ratio on the co-composting process was explored using 5% bagasse biochar as an additive and conditioner. Results showed that when the mass ratio was 1:1, nitrogen fixation ability was the strongest and ammonia nitrogen increment in the pile reached 2.31 mg/g. The increase in excess sludge content/food waste ratio during composting was conducive to the accumulation of H2O-P, BD-P, HCl-P, NaOH-P and NaOH85-P. When the ratio of excess sludge to food waste mass was 1:1, the relative abundance of Firmicutes was the largest in the compost, which corresponded to 72.77% at the phylum level. Food waste mass was more beneficial to the growth and reproduction of microorganisms and to the metabolic activities related to membrane transport. Considering the fungal content, Ascomycota and Basidiomycota were maximum, with relative abundance of 69.53% and 20.91%, respectively, at the mass ratio of 1:1.