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

Aromatic liquor breweries produce massive distiller grains containing a high percentage of rice husks that necessitate harmless treatment and resource utilization. These husk-rich distiller grains 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 3-year field experiment (2018–2020) was established to understand the effects of BDG on sorghum agronomic performances and greenhouse gas emissions from the soil. The results showed that BDG had higher mineral nutrient (N, P, K, and S) contents, 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), the combination of CF and BDG (CF+BDG) increased sorghum nutrient (N, P, and K) uptake, yield, fertilizer use efficiency, and economic benefit. Cumulative CO2 emission from the soil changed little between with and without BDG, indicating the microbial stability of BDG. The effective adsorption of NH3 or NH4+ by BDG upon N application may reduce N loss through NH3 and N2O emissions and increase the efficiency of fertilizer N use. Cumulative 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.