Abstract
The aim of this work is to integrate, in the same reactor, subcritical water extraction with a downstream Hydrothermal Carbonization (HTC) process for apple pomace valorization. For this purpose, tests were run in a 250 mL stainless steel reactor. The first extraction step was performed in a temperature range from 100 to 125°C and pressures above the corresponding saturation to maintain the water in a liquid state. Then, extraction residues were characterized by moisture and ash content, elemental composition, and higher heating value. Thermogravimetric Analysis (TGA) and deconvolution of Thermogravimetric Derivative (DTG) peaks were used to identify free sugars and hydrolyzed protein. Afterwards, HTC test of spent material was performed at 220 °C for 3 hours. The resulting solid phase (hydrochar) was collected and characterized as well.