Biochar addition reduces nitrogen loss and accelerates composting process by affecting the core microbial community during distilled grain waste composting.

This study evaluated the impact of biochar addition on nitrogen (N) loss and the process period during distilled grain waste (DGW) composting. Results from the five treatments (0, 5, 10, 15, and 20% biochar addition) indicated that 10% biochar addition (DB10) was optimal, resulting in the lowest N loss, 25.69% vs. 40.01% in the control treatment. Moreover, the DGW composting period was shortened by approximately 14 days by biochar addition. The composition of the microbial community was not significantly altered with biochar addition in each phase, however, it did accelerate the microbial succession during DGW composting. N metabolism pathway prediction revealed that biochar addition enhanced nitrification and inhibited denitrification, and the latter phenomenon was the main reason for reducing N loss during DGW composting. Based on the above results, a potential mechanism model for biochar addition to reduce N loss during the DGW composting process was established.