Preparation and Basic Characterization of Hydrochar from Food Waste Digestate Sludge via Hydrothermal Carbonization

Hydrochar has been regarded as a promising alternative for recycling and upcycling various wastes streams. In this study, hydrochar from food waste digestate sludge (FWS) was prepared using hydrothermal carbonization (HTC). The properties of the prepared hydrochar were assessed under different conditions, including reaction temperature (180, 220, and 260°C) and time (0.5, 1, and 2 hours). The characterization included analyses of pH, electrical conductivity, proximate composition, elemental composition, calorific value, energy density, and energy yield. A correlation analysis was performed to understand the relationship between these properties and hydrochar’s production operating conditions. The parameters showed stronger relationships with reaction temperature, with several exhibiting high correlation coefficients. In particular, hydrochar’s mass yield, and its carbon, sulfur, and oxygen contents, as well as its calorific value, exhibited strong correlations. The fundamental characterization of hydrochar in this study is expected to serve as valuable data for the efficient recycling of FWS in the future.