The dominant role of bacterial community and network characteristics drive the humification process and greenhouse gas emissions during plant residues composting under different aeration rates

Abstract

The study investigated the effects of different aeration intensities on organic matter (OM) degradation, greenhouse gas emissions (GHG) as well as humification during plant residue composting. Three intermittent aeration intensities of 0.16 (T1), 0.38 (T2) and 0.68 (T3) L/kg DM/min with 30 min on/30 min off were conducted on a lab-scale composting experiment. Results showed that OM mineralization in T3 was more evident than T1 and T2, resulting in the highest humification degree and humic acids (HA) content. HA content in T2 and T3 was 7.68% and 10.28% higher than that in T1. Medium aeration intensity was more favorable for emission of total GHG emission. Linear Discriminant Analysis Effect Size analysis showed that the biomarkers within T1 mainly belonged to Anaerolineaceae, while Thermostaphylospora was identified as biomarkers in T2. The enrichment of thermophilic bacterial genera may play important roles on promoting humification in T2 and T3. Bacterial network analysis showed that T3 had the most key nodes and edges. The interaction between bacterial community was strengthened and the network relationship was closest in T3. The Structural Equation Model confirmed the roles of dominant bacterial community on promoting humification. Oxygen concentration and pH indirectly affected both the mineralization and humification through the action of key microorganisms.