Bio-crude oil produced from source separated dried household food waste through hydrothermal liquefaction

The thermochemical valorization of household food waste represents a promising pathway toward circular bioeconomy and renewable fuel production. In this study, source-separated household food waste was subjected to controlled thermal drying and stored for approximately ten years prior to hydrothermal liquefaction (HTL), enabling evaluation of long-term feedstock stability and its impact on bio-crude production. HTL experiments were conducted at temperatures between 280–320 °C, solids loadings of 5–20 wt%, and residence times of 30–60 min. Results demonstrated progressive improvement in bio-crude yield, elemental composition, and higher heating value (HHV). The highest-quality bio-crude was obtained at 320 °C, 20 wt% solids, and 60 min, achieving a HHV of approximately 43 MJ kg−1 and oxygen content near 9 wt%, values approaching fossil-derived heavy fuels. Compared to wet food waste systems reported in recent literature, the pre-dried feedstock exhibited enhanced carbon recovery to the oil phase and reduced aqueous carbon losses. Long-term storage did not negatively affect conversion efficiency, confirming the stabilizing effect of drying. These findings indicate that decentralized drying functions both as a stabilization and feedstock conditioning strategy that improves HTL performance and downstream upgrading potential.