Performance and microbial community dynamics during rice straw composting using urea or protein hydrolysate as a nitrogen source: A comparative study

Aerobic composting is a promising alternative for the recycling of rice straw (RS), and an applicable nitrogen source is necessary to improve the process. The aim of this study was to compare the performance and microbial community dynamics of RS composting using urea or protein hydrolysate from leather waste (PHL) as a nitrogen source. Results showed that PHL addition achieved a faster temperature increase rate at start-up (1.85 ℃·h-1 vs 1.07 ℃·h-1), higher volatile solid degradation efficiency (48.04% vs 46.98%), and greater germination indices (111.72% vs 89.87%) in the end products, as compared to urea. The major bacterial phyla included Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria in both composting processes. Although the bacterial communities in both processes succeeded in a similar pattern according to different composting phases, PHL addition accelerated the succession rate of the microbial community. Co-occurrence network analysis revealed that bacterial community composition was strongly correlated with physicochemical properties such as dissolved organic carbon (DOC), NH4+, pH, temperature, and total nitrogen (TN) content. These results proved the potential of using PHL as a nitrogen source to improve the RS composting process.