Effects of biochar produced from distiller grains on agronomic performances of sorghum (Sorghum bicolor L.) and greenhouse gas emissions from soil

Aromatic liquor breweries produced massive distiller grains with high rice husks that necessitate harmless treatment and resource utilization. These solid wastes can be pyrolyzed in the Ni-based catalyst system at a relatively low temperature (480 °C) into combustible gas, which is used in liquor distillation, and biochar (BDG) with high mineral nutrients and good surface properties. A three-year field experiment (2018–2020) was established to understand the influence of BDG on sorghum agronomic performances and greenhouse gas emissions from the soil. The results showed that BDG had higher mineral nutrient contents (N, P, K, and S), larger cation exchange capacity, and better surface structure than those prepared using the traditional method at 400 and 600 °C. Compared with sole chemical fertilizer (CF), CF+BDG increased sorghum nutrient uptake (N, P, and K), yield, fertilizer use efficiency, and economic benefit. Accumulative CO2 emission changed little from soils with and without BDG, indicating the microbial stability of BDG. The effective adsorption of NH3/NH4+ by BDG upon N application may reduce N loss through NH3 and N2O emissions and increase the efficiency of fertilizer N use. Accumulative CH4 emission ranged from 32.45 to 44.86 g ha-1, which could be overlooked as a greenhouse gas in the sorghum field. Moreover, CF+BDG significantly decreased NH3 and N2O emissions for the production of each unit of sorghum grains and the CO2 emission from the land for the production of a certain amount of sorghum grains. Therefore, CF+BDG exhibited better agronomic and environmental performances in sorghum cultivation.