Hydrothermal humification of olive pomace: a circular approach for producing artificial humic substances

This study explores the hydrothermal humification (HTH) of olive pomace as a sustainable strategy to produce artificial humic acids (AHAs). HTH experiments were conducted at 180, 200, and 220 °C using KOH as an alkaline agent. Reaction products were separated and analyzed for yield, chemical composition, and structural features. The highest AHA yield (12.8%) was obtained at 180 °C under alkaline conditions, while yields decreased significantly at higher temperatures. FTIR and elemental analyses confirmed that the AHAs shared functional and compositional traits with naturally occurring humic substances. These results demonstrate the potential of HTH as a circular valorization pathway for olive mill residues.