Management and valorization of digestate from food waste via hydrothermal

Abstract

Hydrothermal treatments (HTT) at moderate temperatures (120–200 °C) were investigated in this study for the management and valorization of food waste digestate (DFW). The dehydration was the main reaction in HTT at a temperature lower than 180 °C. After HTT, the hydrophobicity and dewaterability of DFW were improved significantly, which resulted in a 69% and 37% reduction in the digestate cake volume and solid residue mass, respectively. During HTT, the organic matter and carbon were mostly solubilized from solid to liquid, while the multivalent metals were concentrated in the solid residue. The more stable characteristics of the digestate cake after HTT eliminated its environmental risk. The accumulation of organic carbon and a reasonable ammonia nitrogen concentration in the HTT liquid increased the biochemical methane potential from 147 to 245 mL CH4/g TCOD, which demonstrated the feasibility of recovering energy from the HTT liquid.