There is an overlooked problem which increasing microbial abundance while reducing nitrogen loss during composting. This study investigated the viability of spent mushroom substrate (SMS) as conditioners in the aerobic composting of kitchen waste (KW) with cattle manure (CM). The variation of temperature, pH, C/N, organic matter, cellulose, hemicelluloses, germination index (GI), and microflora structure were explored to evaluate the potential in accelerating maturity and nitrogen fixation by SMS addition. The results showed that the addition of SMS accelerated the heating rate, prolonged the high temperature time, and decreased organic matter, hemicellulose, and cellulose by 17.49%, 23.61%, and 18.62%, respectively. The GI reached 105.86% with SMS addition, while 74.17% was found in control treatment after composting. SMS changed the microbial community composition and increased the species abundance. Proteiniclasticum, Clostridium XI and Azomonas were dominant bacteria, which increased the retention of nitrogen, promoted organic matter degradation and reduce compost time. The study can provide a feasible strategy for nitrogen fixation in the field of organic waste recycling.

In order to enhance the start-up of anaerobic digestion (AD), the propionate-degrading methanogenic cultures were introduced to AD of food waste at a high organic loading rate (OLR) of 3.0 g VS/L∙d in this study, and the efficiency of different bioaugmentation strategies were investigated. The results demonstrated that bioaugmentation significantly improved the start-up efficiency and enhanced the methane production. Specifically, higher dosage and frequency of bioaugmentation had a positive effect on the performance of the AD reactors. Among three bioaugmented reactors, the reactor with a bioaugmentation strategy of 0.675 g VS/L of bioaugmentation seed added every 5 d during the first hydraulic retention time (HRT) performed the best and remained relatively stable for the next three HRTs without bioaugmentation. The 16S rRNA gene sequencing analysis revealed that Methanothrix predominated in bioaugmented reactors. A large proportion of Methanothrix accompanied by a small proportion of Methanospirillum played a key role in volatile fatty acid degradation and contributed to the successful start-up and long-term stability of AD at a high OLR. These findings suggest that bioaugmentation with methangenic consortium is a promising strategy to boost the AD process at high OLRs and achieve higher treatment capacity of food waste.