The elemental compositions and other properties of bio-oil and SR obtained under different conditions are summarized in Table 2. Compared with the elemental composition of the crude rice husk, the obtained bio-oils had higher contents of carbon and hydrogen but lower concentrations of oxygen, leading to increased caloric values. As shown in the table, the HHVs of bio-oils were both higher than 20 MJ/kg, while the HHVs of the crude rice husk was only 14.93 MJ/kg. Moreover, the O/C atomic ratio of bio-oils decreased and the H/C atomic ratio increased. The significant reduction of oxygen content in bio-oils was mainly due to the dehydration reactions and the formation of CO/CO2 in the liquefaction process [14]. In addition, the nitrogen content of bio-oils was higher than that of the raw material.