Potassium assisted pyrolysis of Chinese Baijiu distillers' grains to prepare biochar as controlled-release K fertilizer

A novel K-loaded biochar as controlled-release K fertilizer was prepared through K assisted pyrolysis of distillers' grains (DGs, typical solid-byproducts of Chinese Baijiu) under different atmospheres (N-2 and CO2) and temperatures (400 and 800 degrees C). The fabricated DGs-based biochar exhibited high K loading (200.20-232.33 mg/g), and the release kinet-ics and column leaching experiments suggested that K-loaded biochar exhibited excellent controlled release perfor-mance in a long term. Compared with other biochar, the K-loaded biochar prepared at CO2 and 400 degrees C has lower cumulative release ratio of 82.35 %, and could retain the durative K release at similar to 0.5 % for 25 d. The release kinetics suggested that the K release behavior was dominated by dissolution, electrostatic attraction, adsorption, confinement effect, and chemical interaction. Furthermore, pot experiments revealed that K-loaded biochar could promote the growth of Komatsuna, in which the fresh weight and chlorophyll relative content of Komatsuna cultivated with biochar prepared at CO2 and 400 degrees C reached 0.146 g and 41.95 after 25 d growth, respectively. The above results suggested that the K-loaded biochar exhibited excellent utilization potential as a controlled-release K fertilizer, facilitating the sustainable development and resource valorization of Baijiu industry.