Effects of different bulking agents on the maturity, enzymatic activity, and microbial community functional diversity of kitchen waste compost

Aerobic composting is an effective method for the disposal and utilization of kitchen waste. However, the addition of a bulking agent is necessary during kitchen waste composting because of its high moisture content and low C/N ratio. In order to select a suitable bulking agent, we investigated the influence of leaf litter (LL), sawdust (SD), and wheat straw (WS) on the enzymatic activity, microbial community functional diversity, and maturity indices during the kitchen waste composting process. The results showed that the addition of WS yielded the highest maturity (the C/N ratio decreased from 25 to 13, T value=0.5, and germination index (GI)=114.7%), whereas the compost containing SD as a bulking agent had the lowest maturity (GI=32.4%). The maximum cellulase and urease activities were observed with the WS treatment on day 8, whereas the SD treatment had the lowest cellulase activity and the LL treatment had the lowest urease activity. The compost temperature and microbial activity (as the average well color development) showed that bulking the composts with SD prolonged the composting process. The diversity index based on the community-level physiological profile showed that the composts bulked with LL and WS had greater microbial community functional diversity compared with those bulked with SD. Thus, the maturity indexes and enzymatic activities suggest that WS is a suitable bulking agent for use in kitchen waste composting systems.