Optimization of hydrothermal carbonization of food waste as sustainable energy conversion approach: Enhancing the properties of hydrochar by landfill leachate substitution as reaction medium and acetic acid catalyst addition

The organic fraction of municipal solid waste (OFMSW) is a controversial biomass that can be converted into renewable energy by hydrothermal carbonization (HTC). The landfill leachate (LL) was used as an alternative liquid source to overcome global concern of water scarcity. The HTC optimization via LL substitution was conducted to study the effects of reaction temperature (180-260 celcius), residence time (2-6 h), biomass to liquid (B/L) ratio (10-20 wt%) and LL COD (10000-20000 mg/L) on mass yield (MY) and higher heating value (HHV) of hydrochar using the Box-Behnken design of response surface methodology. The hydrochar properties, process water and gas product characterizations were evaluated. The effect of acetic acid catalyst was investigated at optimal conditions. Optimal conditions were determined at 225 degrees C, 4.5 h, 20 wt% B/L ratio and 10000 mg/L COD, with 55.30 % MY and 30.15 MJ/kg HHV. Utilization of acetic acid improved the HTC efficiency. Substi-tution of LL is technically feasible and can upgrade the sustainability of HTC.