24 / 2023-04-29 10:54:05

Regulating Bacterial Dynamics by Lime Addition to Enhance Kitchen Waste Composting

Kitchen waste composting,lime,modular network analysis,bacterial community

Aerobic composting has been verified to effectively convert kitchen waste into high-quality organic fertiliser. To improve composting performance, several pragmatic approaches, have been reported to improve kitchen waste composting from the perspectives of humification and gaseous emissions. Despite their potential for composting performance, these strategies hardly improve acidification characteristic of kitchen waste, which could delay temperature increase and humification as well as exacerbate GHG and malodour emissions during composting. Nevertheless, no relevant studies have been dedicated to the development of countermeasures to further ameliorate kitchen waste composting.

As inspired by previous reports, this study examined bacterial dynamics in response to lime addition for enhancing kitchen waste composting using modular network analysis. Humification and gaseous emissions were determined to evaluate composting performance. Modular network analysis was used to separate bacterial communities into three meta-modules corresponding to the mesophilic, thermophilic, and mature stage of composting, respectively. Lime addition up to 1% could suppress unfavourable dominant bacteria, including acidogens and denitrifiers, in the mesophilic stage to reduce the emission of greenhouse gases. Lime addition also increased the matrix pH and temperature via hydrogen reaction to favor bacterial growth and activity. Thus, the relative abundance of thermophilic bacteria (e.g. Thermoactinomycetaceae and Planifilum) increased with lime addition to facilitate the biodegradation of lignocellulose for humus formation at the thermophilic stage. Further increase of lime dosage up to 1.5% significantly reduced ammonia emission, particularly at the thermophilic stage via chemical fixation of calcium hydroxide in addition to the enhanced organic biodegradation. Moreover, lime addition inhibited the activity of denitrifiers (e.g. Acinetobacter and Steroidobacter) at the mature stage to reduce the emission of nitrous oxide. As such, lime addition could effectively improve composting performance in both biotic and abiotic processes. Results reported here will provide valuable understanding on the performance of lime addition to improve kitchen waste composting.