Evaluation of catalytic subcritical water gasification of food waste for hydrogen production: Effect of process conditions and different types of catalyst loading

Food waste is a kind of wet bio-waste which has been a challenge for the ecological environment and disposal. In this paper, hydrogen production from subcritical water gasification (SbWG) of food waste with and without catalyst loading was systematically investigated. The effects of reaction temperature (300–360 °C), residence time (30–90 min), food waste concentration (10–30 wt%) and catalysts (Ni/γ-Al 2 O 3 , Ni/ZrO 2 , NaOH, KOH, and FeCl 3 ) were studied within a pressure range of 10.5–20 MPa. The optimal process condition for SbWG of food waste without catalysts loading was determined to be 360 °C and 90 min with 10 wt% food waste. The liquid products and hydrochar were characterized by TOC , TGA/DTG, and SEM. The TOC concentration of liquid products decreased vastly with increasing reaction temperature. The highest H 2 yield (1.88 mol/kg), H 2 mole fraction (35.01%), and H 2 selectivity (53.86%) were achieved at 360 °C for 90 min with 5 wt% loading of KOH. It can be concluded that the performance of the catalysts for improving hydrogen production in SbWG of food waste was in the following order: KOH > NaOH > Ni/γ-Al 2 O 3  > Ni/ZrO 2  > FeCl 3 . The catalytic SbWG can be a potential alternative for energy conversion of food waste and hydrogen production.