Hydrothermal pretreatment and compound microbial agents promoting high-quality kitchen waste compost: Superior humification degree and reduction of odour

Abstract

Present study investigated the effects of hydrothermal pretreatment (HTP) and addition of compound microbial agent (CMA) on humification, odour generation and metabolism functions of bacterial communities during composting of kitchen waste (KW). Surprisingly, HTP and CMA addition treatment could promote the humification of compost and the control of odour units in contrast to the control (without HTP and CMA addition). The humic acid to fulvic acid ratio of end compost increase by 187.30 %, while humification index (HIX) increased by 18.87 %. 3D-EEM fluorescence spectroscopy of dissolved organic matter (DOM) demonstrated that it facilitated the synthesis of humified compounds and the decomposition of biodegradable compounds. Moreover, the SUVA254, SUVA280 and E253/E203 increased by 118.6 %, 115.25 % and 42.11 % after HTP and CMA addition indicating an increase in aromatic carbon abundance. VFAs had the higher degradation rate (84.91 %) than other treatments (57.46–77.72 %). Meanwhile, the main contributor to the malodorous odour was isovaleric acid, followed by butyric acid and acetic acid during composting. Mantel test indicated that the humification degree was significantly influenced by environmental parameters (temperature, pH, etc.) and metabolic products (HA, DOC and VFAs). Metagenomic analysis indicated that the biodegradation processes at the thermophilic stage were controlled mainly through genes involved in microbial metabolism. HTP and CMA addition was an eco-friendly and efficient strategy to reduce odour emission and improve the compost quality.