Valorization of oat husk by hydrothermal carbonization: Optimization of process parameters and anaerobic digestion of spent liquors.

Abstract The hydrothermal carbonization (HTC) optimization of oat husk was performed using a response surface methodology. Furthermore, anaerobic digestion (AD) of spent liquor and hydrochar addition were evaluated in the biomethane potential (BMP) test. Results found that temperature influences the most in the studied responses (i.e., mass yield (MY) and higher heating value (HHV)). Optimal hydrochar MY (53.8%) and HHV (21.5 MJ/kg) were obtained for 219.2 °C, 30 min, and 0.08 of biomass/water ratio. A successful prediction capability of the optimization approach was observed, archiving an error