The impacts of aeration modes and rates on nitrogen conversion and bacterial community composition in a 90-m3 silo composting reactor

Abstract

The silo composting reactor is applicable for the in-situ treatment of organic waste. Ensuring an adequate supply of oxygen can enhance the compost maturity. This study investigated the effects of aeration modes and rates on composting effectiveness and nitrogen conversion. The 24 h uninterrupted aeration mode (K60T0) was conductive to achieving an elevated temperature of 78 °C. The germination index value in the lower layer consistently exceeded 80 % with different aeration modes. The content of total nitrogen (excluding K60T0) and ammonia nitrogen increased progressively with the increase of aeration time. Meanwhile, nitrate nitrogen content exhibited fluctuations, with the lowest content observed in the middle layer. An aeration cycle of 50 min followed by a 10-min pause within an hour resulted in the highest amide nitrogen content of 5.93 g/kg and organic nitrogen content of 2 % in the upper layer. The dominant phylum and genera were Firmicutes and Ureibacillus, respectively. The relative abundance of Firmicutes initially decreased and then increased in general with prolonged aeration time. Additionally, the extension of aeration time altered the nitrogen cycling function within the reactor.