BOOK OF ABSTRACTS 65 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Tuesday, 25 August 2026 / Hall B+C Technologies and Applications SL26 Hydrothermal Humification for Valorisation of Food Waste into Artificial Humic Substances Lauris Arbidans1, Reinis Saksons1, Linda Ansone-Bertina1, Maris Klavins1 1 University of Latvia, Department of Environmental Science, Jelgavas street 1, Riga, LV 1004, Latvia, email: lauris.arbidans@lu.lv Food waste (FW) management has emerged as a major challenge for the circular economy and climate-neutral development. Globally, FW management costs are estimated at USD 2.6 trillion annually [1], while in the EU alone more than 59 million tonnes of FW are generated each year, corresponding to approximately 130 kg per capita and a market value of EUR 132 billion [2,3]. Beyond direct economic losses, FW disposal contributes approximately 3.49 billion tonnes CO2-equivalent annually, accounting for 8–10% of global greenhouse gas emissions [4,5]. Conventional management routes, including landfilling, composting, and incineration, remain insufficient because they fail to ensure complete resource recovery and are poorly suited to wet, highly biodegradable feedstocks. Hydrothermal carbonisation (HTC), specifically its subtype - hydrothermal humification (HTH) - has therefore emerged as one of the most promising green conversion technologies for wet biomass streams. Conducted in subcritical water (180-260 °C) under autogenous pressure and using strong alkali (e.g. KOH) as a catalyst, HTH enables direct processing of FW without energy-intensive drying, converting heterogeneous organic matter into carbon-rich hydrochar (HC) and artificial humic substances (AHS), which can be used in agriculture and environmental technologies [6]. This study focuses on common household kitchen food waste stream valorisation possibilities for production of AHS, that could benefit circular economy principles, while mitigating the environmental impact of FW. Several food items were chosen with diverse macronutrient composition that cover most of the food chain – carbohydrates, fats, protein and lignocellulose. Individual samples were subjected to HTH conditions, using 0.65 M KOH solution under temperature range of 170–230 °C over 1–8 hours. Obtained AHS solutions were separated from HC, artificial humic acids (AHA) were precipitated from AHS solutions, purified and characterised, using UV-Vis spectroscopy, FTIR and 3D-EEM fluorescence spectroscopy. Obtained AHA samples derived from food waste were compared to natural peat humic acids and results showed that the core composition is similar, however AHAs exhibited relatively more unsaturated aliphatic structures than natural mature peat humic acids [7].
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