Microbial-based detonation and processing of vegetable waste for high quality compost production at low temperatures

Composting is a resourceful and harmless technique for reducing vegetable waste (VW), but low temperatures limit the efficiency and quality of composting. Owing to the perishability of the VW and its high indigenous microbial populations, the development of microbial inoculants to enhance its composting is challenging, and thus rarely reported. This study proposed a method for screening and applying compost inoculants to improve the efficiency, safety, and maturity of VW composting at low-temperature. Five cold-adapted (10 °C) strains (Brachybacterium, Klebsiella, Myroides, and Proteus) with glycolytic, starch-hydrolytic, and pectin-degrading functions and four heat-adapted (60 °C) strains (two Parageobacillus and two Bacillus strains) with cellulose-degrading function were screened and inoculated before the initial and thermophilic period of composting, respectively. The inoculants (group T) raised the average temperature of the thermophilic period by more than 2 °C. During the cooling period, the germination index in the T group was 104.7% as compared to 83.3% in the control group. Initially added weed seeds and pathogens were inactivated in both groups, but the rate of inactivation was faster in the T group. The ratio of humic acid to fulvic acid was 2.2 in the T group during the cooling period as compared to 1.4 in the control group, which represented a significant increase (62.0%) in this conversion. During the thermophilic or cooling period of the composting, the inoculants significantly increased the cellulase activity by 74.9%, urease activity by 19.7%, protease activity by 18.6% and catalase activity by 24.4–43.5%. The inoculants not only enhanced enzymatic activities but also restructured and optimized the microbial communities, especially the composition of fungal communities. Moreover, inoculants improved microbial interactions and the contribution of fungi in the composting process. This study provides a theoretical basis and practical knowledge regarding the screening and application of inoculants for performing low-temperature VW composting. Our research could open new avenues of basic and applied research in the science of composting to utilize vegetable wastes for sustainable agriculture and a clean environment.