Regulating bacterial dynamics by lime addition to enhance kitchen waste composting

• Biotic and abiotic processes were regulated by lime for kitchen waste composting. • Lime increased matrix pH, temperature, and regulated bacterial growth and activity. • Lime enriched thermophiles and nitrifiers to enhance humification and NO 3 – content. • Lime inhibited denitrifiers at mesophilic and mature stages to reduce N 2 O emission. • Lime addition reduced NH 3 emission at thermophilic stage by chemical fixation. 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.