*2.3. Pyrolysis Experiments*

Based on the TGA/DTG data (discussed in Section 3.1), the pyrolysis temperature had to be above 400 ◦C because the peak temperature of DTG was found to be around 380 ◦C. This result was consistent with those reported by Johar et al. [34], indicating the complete devolatilization of hemicellulose and cellulose at around 400 ◦C. Therefore, the pyrolysis experiments were performed by the matrix combinations of temperature (400–900 ◦C, increased by the interval of 100 ◦C) and holding time (0–90 min, increased by the interval of 30 min) in the present study. Herein, a null holding time means that the heating was stopped (powered off) when the specified temperature was reached. Based on previous studies for producing biochar [35–40], a vertical fixed-bed electric furnace is suitable equipment for the production of biochar from various biomass feedstocks. For each pyrolysis experiment, around 5 g of the RH sample was pyrolyzed at a heating rate of around 10 ◦C/min under an inert atmosphere by passing N<sup>2</sup> flow rate of 500 cm3/min. The biochar yield was obtained from the difference between the initial RH sample weight and the resulting biochar weight based on the weight of RH sample fed. In order to describe the RH-based biochar (i.e., BRH), the resulting biochar was denoted as BRH-pyrolysis temperature-holding time. For example, the product BRH-400-30 refers to the pyrolysis conditions at temperature of 400 ◦C for holding time of 30 min.
