IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 BOOK OF ABSTRACTS 272 Poster Session / Technologies and Applications Hall A + %S). In addition, the H/C, O/C, and C/N atomic ratios were determined, as well as the degree of internal oxidation using Zdanow’s formula: ω = [(2O + 3N) − H]/C. Referring to the ranges of elemental composition for humic acids of soil origin reported by Kononova, these compounds typically contain 52–62% C, 3–5.5% H, 30–33% O, and 3.5–5.0% N. The C content in the analyzed AHAs indicated values typical of, or very close to, those reported for natural humic acids. Similar observations were made for H content. The O content may indicate a high abundance of O-containing functional groups, whereas the lowerthan-typical N content resulted from the naturally low concentration of this element in the biomass used. In most of the analyzed variants, increasing the torrefaction temperature led to a reduction in C, H, and N contents; however, the magnitude of these changes varied across the investigated temperature ranges. Changes in the elemental composition consequently affected the H/C, O/C, and C/N ratios, as well as ω. In the case of the H/C and O/C ratios, the most pronounced changes related to the degree of humification and the abundance of O-containing functional groups were observed from 240 °C onwards. In contrast, for the C/N ratio and ω parameter, some variants (temperature/catalyst/particle size combinations) exhibited several temperature ranges characterized by more distinct shifts in the values of these indicators. References 1. K. Sun, Z. Niu, S. Xiao, X. Qi, S. Li, M. Chen, L. Dai, Y. Si, npj Clean Water 7 (2024) 47. 2. A. Gryta, K. Skic, A. Adamczuk, A. Skic, M. Marciniak, G. Józefaciuk, P. Boguta, Agriculture 14 (2024) 37. 3. F. Yang, S. Zhang, K. Cheng, M. Antonietti, Sci. Total Environ. 686 (2019) 1140–1151. 4. J.G. Lee, H.Y. Yoon, J.-Y. Cha, W.-Y. Kim, P.J. Kim, J.-R. Jeon, Biotechnology Advances 37, 8 (2019) 107416. Acknowledgement This research was funded in whole by the National Science Centre, Poland, grant no. 2024/53/B/ST10/03137
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