Regulating bacterial dynamics by lime addition to enhance kitchen waste composting

This study examined bacterial dynamics in response to lime addition to enhance kitchen waste composting using modular network analysis. Bacterial communities could be separated into three meta-modules corresponding to the mesophilic, thermophilic, and mature stage of composting. Lime addition at 1% (wet weight) suppressed acidogens and denitrifiers (e.g. Lactobacillus and Acinetobacter) at the mesophilic stage to reduce greenhouse gas emissions. The matrix pH and temperature were also increased by lime addition via hydrogen reaction to favor bacterial growth and activity. Thus, thermophilic bacteria (e.g. Thermoactinomycetaceae and Planifilum) were enriched with lime addition to facilitate lignocellulose biodegradation for humus formation at the thermophilic stage. Further lime addition to 1.5% reduced ammonia emission at the thermophilic stage via chemical fixation. Moreover, lime inhibited denitrifiers but proliferated nitrifiers at the mature stage to decrease nitrous oxide emission and enhance nitrate content, respectively. As such, lime addition improved both biotic and abiotic composting performance.