Effects of oxygen supply rate on organic matter decomposition and microbial communities during composting in a controlled lab-scale composting system

Abstract

The study aimed to elucidate the effect of oxygen supply rate (OSR) on the composting of model organic waste independently from other factors by using a controlled laboratory-scale reactor system. Four OSRs, 96.2, 24.2, 13.7, and 3.45 mL-O₂/min/kg-WS (wet solid), were tested. The delay of organic matter degradation was observed temporarily in the early stage of composting with 13.7 mL-O₂/min/kg-WS and severe oxygen deficiency was observed in lower OSR, indicating that the critical OSR existed around this value. Composting with 3.45 mL-O₂/min/kg-WS resulted in constantly low CO₂ evolution rate and remarkably low degree of organic matter degradation. Under deficient oxygen, all enzymes measured, such as phosphatases, esterases, lipases, proteases, and sugar degrading enzymes, showed lower activities. High-throughput sequencing revealed Caldibacillus and Ureibacillus became dominant in the later stages of the oxygen deficiency composting, while Geobacillus was the most dominant microorganism throughout composting with OSR higher than 13.7 mL-O₂/min/kg-WS.

Keywords: Composting; Enzymatic activities; Microbial community; Oxygen supply.