Preparation of artificial humic acid from cotton stalk and saline-alkali soil by synergistic catalytic pyrolysis and its potential agricultural application

s The green synthesis of artificial humic acid (AHA) is a key approach to the efficient utilization of biomass waste resources. To reduce dependence on strong alkaline agents (KOH, NaOH, etc.) in current humification methods, this study proposes using Saline-alkali soil (SAS) as a cost-effective substitute for producing AHA from biomass solid waste. The results of the study indicated that an AHA yield of 23.33 % ± 1.12 % was achieved through pyrolytic humification under optimal conditions (250 °C, 2 h, with SAS to cotton stalk (CS) ratio of 4: 1). Characterization analysis demonstrated that the SAS supplied an alkaline environment throughout the humification process. Furthermore, the mineral elements in the SAS (Na + , K + , Fe 3+ , and Al 3+ ) facilitated the decomposition of lignin to generate polyphenolic structures, which promoted the protein condensation and increased the aromaticity of AHA. Carbon flow analysis revealed that 60.5 % of the carbon was immobilized, with AHA contributing up to 25.6 % of the total immobilized carbon. Hydroponic experiments demonstrated that the addition of AHA at a concentration of 200 mg L −1 significantly enhanced wheat growth. The residual carbon soil cultivation experiment revealed that the residual carbon exhibited a high specific surface area (6.57 m 2 g −1 ) and effective adsorption properties, achieving a 16 % immobilization rate of Pb and alleviating heavy metal stress on plants. This study presents an innovative approach to the integrated management of SAS and converting biomass solid waste into 'carbon-negative emissions'.