Effect of Biochar on the Co-Conversion of Carbon-Nitrogen and Humification of Kitchen Waste Composting Process

Abstract

Composting was an effective technique to treat kitchen waste into high-quality fertilizer or soil amendment. The unsynchronized conversation of carbon and nitrogen during kitchen waste composting bring about nitrogen loss, carbon emission and low product quality. Therefore, this study explored biochar (5%, 10%, and 15%) on the microcosmic mechanism of nitrogen transformation and humification of kitchen waste composting to manage co-conversation of nitrogen and carbon. Results showed that addition of 10% and 15% biochar prolonged thermophilic period (>55°C) at least 3 days than control, and the final NH4+-N was three times lower than the control in the 10% and 15% treatments, and NO3--N was about 3.5 times higher in the 15%-treated experimental group than in the control. The addition of 15% contributing the most. High-throughput sequencing demonstrated that Firmicutes and Proteobacteria were the dominating species throughout the process, and adding biochar enhanced the abundance of both species, especially Pseudoxanthomonas in Firmicutes. A higher abundance of SBR1031 was identified in the compost treated with 15% biochar. Biochar promotes nitrogen mineralization and humification by adsorbing ammonia and nitrogen and influencing microbial community structure. 10%-15% biochar addition could significantly advance the compost into the high-temperature period, improve the quality of the compost, reduce the nitrogen loss, and enhance the nitrogen fixation capacity, which is essential for the production of value-added compost fertilizers.

Keywords: Kitchen waste, Composting, biochar, nitrogen retainment, Microorganisms