*2.3. Bomb Calorimeter*

In order to take the necessary measurements, a Parr 1341 Plain Jacket Bomb Calorimeter was used. In more detail, from the samples obtained after torrefaction for a given time, we accurately weighed quantities of about 0.5 g. Then, the 0.5 g was placed in the oxygen container with the pressure of 25 bar oxygen and a specific length of ignition wire. The combustion container was placed in the calorimeter's adiabatic tank, which contained 2000 g distilled water shaken at a steady speed while the temperature was measured per minute. Accordingly, two ignition lead wires were pushed into the terminal sockets on the bombs' head, the cover was set on the jacket and the stirrer was turned manually in order to ensure that it ran freely. Upon turning of the stirrer, the drive belt slipped onto the pulleys and the motor started operating.

With regards to temperature indications, they were measured manually with the help of a 6775 Parr Digital Thermometer each minute for 5 min in order to achieve equilibrium into the calorimeter. More specifically, at the start of the sixth minute, the ignition button was pushed and temperature measurements were taken each minute until the temperature became stable again. As such, the increase of the temperature was intense during the first minutes and slowed down when reaching the stage equilibrium. The energy equivalent of the calorimeter was determined by its standardization at 10,104 J/ ◦C. The energy equivalent due to the formation of nitric acid and sulfuric acid was not included in the calculations while the moisture content of the samples was 6.0%.

Additionally, two ignition lead wires were pushed into the terminal sockets on the bombs' head, the cover was set on the jacket, and the stirrer was turned manually in order to ensure that it ran freely. Upon turning of the stirrer, the drive belt slipped onto the pulleys and the motor started operating. In this context, the diagram of Figure 2 depicts the temperature profile and how the latter is a ffected during the di fferent stages described earlier.

**Figure 2.** Temperature profile vs. time during the measurement of a typical sample's higher heating value of combustion.
