Analysis of physicochemical properties and bacterial diversity of stevia waste composting: feasibility of waste mud composting

This study explored the effects of Stevia waste (stevia residue and waste mud) as composting materials on compost quality, with a focus on evaluating the feasibility of waste mud as a composting material. The characteristics of compost, such as temperature, pH, electrical conductivity, germination index, total nitrogen, humic acid (HA), fulvic acid (FA), and bacterial community diversity were investigated in this study. The results showed that the optimal ratio of stevia residue and waste mud compost was 4:1 (T3). Compared with single waste mud as a raw material for composting (T4), the quality of T3 was greatly improved. The addition of appropriate amount of stevia residue increased the maximum temperature of T3 and shortened the composting maturity time, promoted the degradation of organic matter (21.77%) and increased the nitrogen content in compost (28.86%). Compared with T4, the HA/FA value of T3 increased by 45.3%, which greatly enhanced the humification degree of compost. The co-composting of stevia residue and waste mud promoted an increase in the abundance of Actinomycetes and significantly enhanced the diversity and richness of microorganisms within the compost. In summary, this study found an effective way for waste mud resource utilization, and verified through experiments the optimal ratio for composting stevia residue and waste mud.