Capturing differences in the release potential of dissolved organic matter from biochar and hydrochar: Insights from component characterization and molecular identification

Biochar and hydrochar have garnered widespread attention owing to their excellent performance in environmental remediation, carbon sequestration, and resource utilization from biowaste. Studies on the release potential of dissolved organic matter (DOM) have been limited, and the distinction between biochar and hydrochar remains unclear. In this study, pine sawdust was utilized as a model precursor with the aim of comparing the release quantity, components, and properties of DOM from biochar (BDOM) and hydrochar (HDOM) under various simulated conditions. The amount of DOM released by hydrochar (38.20-190.49 g/kg) was significantly greater than that released by biochar (0.57-11.96 g/kg), and more DOM was released at higher temperatures and pH values. BDOM consists of three categories of components, namely, humic-like, protein-like, and benzoic acid-like and tyrosine-like substances compounds, whereas HDOM consists of four categories of components, namely, two categories of humic-like compounds and two categories of protein-like compounds. By using ESI-FT-ICR-MS technology, 8586 compounds in BDOM and 6428 compounds in HDOM were identified. A total of 4665 unique compounds were found in BDOM, 1416 unique compounds were found in HDOM under alkaline release conditions, and HDOM contained more unique compounds than those found in other environments. CRAM/lignin-like compounds made up the majority of the released DOM and reached 31.01-65.35 % for BDOM and 54.79-73.05 % for HDOM. These findings revealed significant differences in the release potential of DOM from biochar and hydrochar, and further behavior research is needed to guide future applications of char materials in the environment and agriculture fields.