Co‐pyrolysis of activated coal gangue and corn stover: Production and application of ammonium humate and mineral‐based solid organic fertilizer

Abstract The high alkalinity resulting from high‐temperature alkali activation of coal gangue limits its application in agricultural fields. Rationally eliminating the adverse effects of alkalinity is crucial for the high‐value utilization of coal gangue. This study innovatively utilized alkali‐activated coal gangue (ACG) to promote the humification of corn stover (CS), achieving efficient synergistic conversion between CG and CS. By calcining CG at 900°C with Ca(OH) 2 , ACG with a silicon activation rate of 19.85% was obtained. The ACG was then co‐pyrolyzed with CS (1:1 mass ratio) at 250°C for 2 h, resulting in a total yield of artificial humic acids (AHA) and artificial fulvic acids (AFA) of 39.87%. Mechanistic analysis showed that ACG reduced organic matter loss, facilitated the decomposition of hemicellulose, cellulose, and lignin, and generated small molecules (e.g., furans and ketones), thereby enhancing humification efficiency. Additionally, ACG improved the structure of AHA, increased carbon content, promoted the conversion of oxygen‐containing functional groups to carbonyl groups, and enhanced the hydrophilicity of AFA. Further hydrothermal treatment with ammonium carbonate produced ammonium humate solution (N‐HS) and a mineral‐based solid organic fertilizer (MSOF). N‐HS was rich in mineral elements. Application at 800 mg L −1 increased wheat stem weight by 55.45%. MSOF significantly promoted wheat root growth, increasing root dry weight by 123.96%. Soil‐based experiments showed that MSOF increased the stem weight of Chinese cabbage by 14.31%. This study provides a new strategy for the comprehensive utilization of CG and agricultural waste, offering both environmental benefits and agricultural value.