Effect of storage time on organic matter decomposition during composting by inoculating enriched microorganisms

The use of an enriched microbial community as an inoculum during composting is expected to be effective in accelerating the decomposition of organic matter. In this study, to enhance the efficiency of organic matter decomposition, the effect of storage time on an enriched microbial community was evaluated using a temperature-controlled lab-scale reactor. Compared with the control (Run A), composting runs that inoculated freshly enriched microorganisms (Run Dry 0) and those that inoculated dry-stored enriched microorganisms for 30 days (Run Dry 30) showed higher degrees of organic matter decomposition, which was mainly attributed to the increase in the relative abundance of microorganisms with efficient organic matter decomposition capacities, such as Bacillus, Geobacillus, and Ureibacillus. Dry storage for 60 days (Run Dry 60) showed a lower pH at the beginning of composting, which was mainly due to the accumulation of lactic acid caused by the rapid proliferation of Enterococcus at the beginning of composting, resulting in slow decomposition of organic matter. However, by inoculating enriched microorganisms from the final stage of Dry 60 (i.e., Run Dry 60+), organic matter decomposition was improved to the same degree as in Dry 0 and Dry 30. This study showed that enriched microorganisms will remain active for a short period during storage, but a longer storage time will affect their organic matter decomposition efficiency as inoculum, whereas reuse of the enriched microbial community will restore their performance as inocula after long-term storage. This study provides implications for the use of stored inocula.