Modified biochar mitigates nitrogen loss in distilled grain waste composting by modulating microbial community...

Area of Science:

• Environmental Science
• Soil Science
• Microbiology

Background:

• Pristine biochar (DB) aids compost maturity and nitrogen retention, but its effectiveness is limited by feedstock and preparation.
• Surface modification of biochar is needed to optimize composting performance.
• Distilled grain waste composting requires strategies to enhance maturity and minimize nitrogen loss.

Purpose of the Study:

• To investigate the effects of pristine biochar (DB) and KOH-modified biochar (DBK) on compost maturity and nitrogen loss.
• To elucidate the microbial mechanisms underlying biochar's impact on composting.
• To assess the economic viability of using modified biochar in composting.

Main Methods:

• Composting experiments using distilled grain waste with no biochar (D), DB, and DBK treatments.
• Analysis of compost maturity using seed germination index (GI).
• Quantification of nitrogen loss and microbial community analysis (including functional genes and network analysis).

Main Results:

• DBK, with high surface area and pore structure, significantly improved compost maturity (GI 70% by 23 d) and accelerated nitrification (16 d).
• DBK reduced total nitrogen loss by 34.13% (vs. D) and 10.47% (vs. DB).
• DBK increased nitrogen-fixing bacteria, microbial complexity, and functional redundancy, identified key microbial drivers (Actinomadura, Chryseolinea) and genes (nxrABC, hao).

Conclusions:

• KOH modification of biochar (DBK) is a superior strategy for enhancing compost maturity and mitigating nitrogen loss.
• DBK promotes nitrogen retention by increasing microbial community complexity, functional redundancy, and specific nitrogen transformation pathways.
• DBK application in composting is economically beneficial, offering a net profit of 63.63 RMB/t.