Comparative studies of hydrochars and biochars produced from lignocellulosic biomass via hydrothermal carbonization, torrefaction and pyrolysis

In this study, hydrothermal carbonization, torrefaction, and pyrolysis of hornbeam wood chips were performed. Different runs were conducted at varying temperatures ranging from 225 to 575 °C, and the resulting biochars and hydrochars were analyzed. Biochars obtained from torrefaction runs had high yields, but no significant structural changes compared to raw material. Biochars produced from pyrolysis runs had high fixed carbon content that increased with temperature. Hydrochars obtained from hydrothermal carbonization had higher degree of carbonization than biochars produced from torrefaction under identical conditions. The order of carbonization degree, from highest to lowest, was: biochars obtained from the pyrolysis process, hydrochars produced from the hydrothermal carbonization process, and biochars obtained from the torrefaction process. The highest heating value of the biochar was 32.51 MJ kg−1, produced from the pyrolysis run at 575 °C.