Abstract:

Composting is an effective way to recycle and dispose of landscaping waste resources. Landscaping waste comes from various sources with significant differences in their properties, and the conditions required for composting also vary significantly. This study divided landscaping waste into grass debris and tree branches and leaves, and composted them separately. Temperature, humidity, pH value, electrical conductivity(EC), and microbial community succession were monitored during the composting process of landscaping waste to explore the nitrogen transformation of different types of landscaping waste compost in Shanghai. The result showed that the temperature of compost containing grass debris and tree branches and leaves rapidly increased after the start of composting. The highest temperature of grass debris compost reached 69.7 ^oC on the 12th day, while the highest temperature of tree branches and leaves compost reached 66.0 ^oC on the 5th days. The pH value of compost containing grass debris and tree branches and leaves showed a decreasing trend in the early stage of composting, followed by an increasing trend. The turning point of the pH value change trend for both types of compost was between the 14th and 20th day. During the composting process, the EC showed a trend of rapid increase in the early stage and then remained stable. The maximum EC value of grass debris compost was 6.50 mS·cm^-1, and the maximum EC value of tree branch and leaf compost was 2.31 mS·cm^-1. Further analysis found that two types of landscaping waste compost contained a large number of microorganisms related to organic matter degradation, mainly including Bacillus subtilis, Actinobacteria, Gammaproteobacteria, Bacteroides, etc. FAPROTAX functional prediction analysis showed that the nitrogen cycling metabolic function in the compost gradually increased with the progress of composting, and the functional metabolic abundance of nitrogen transformation cycle in tree branches and leaves compost increased more significantly. This study revealed the nitrogen transformation of landscaping waste from the perspective of microbial metabolism, providing technical support for the composting and disposal of landscaping waste.

Key words: landscaping waste, composting, microbial community succession, nitrogen cycling