Biorefinery lignin was carbonized under a carbon dioxide atmosphere at various temperatures viz., 500 °C, 600 °C, 700 °C, and 800 °C, separately. The results indicated that with increasing temperature, the mass yield decreased from 49.2% to 39.8%. Carbonization at a high temperature resulted in an increment of carbon (C) content and decreased both the hydrogen (H) and oxygen (O) contents. With the increase of carbonization severity, the ratios of O/C and H/C decreased mainly due to the demethanation, dehydration, and decarboxylation reactions. The carbonization resulted in the transformation of aromatic rings as well as the rearrangement of the aromatic polymers, and the enhancement of the thermal stability of the charcoal formed. [ABSTRACT FROM AUTHOR]