*2.6. GC-MS Analysis of Bio-Oils*

Gas chromatography–mass spectrometry (GC–MS) was carried out on a Shimadzu GCMS-QP2010 Ultra chromate mass spectrometer on an HP-5MS column (0.25 μm, 0.32 mm, 30 m) with the following parameters: carrier gas helium "A", temperature injector 300 ◦C, flow rate through the column 2 mL/min, split mode (10), thermostat temperature program—gradient temperature increasing from 60 to 180 ◦C in steps of 10 ◦C/min, then holding for 10 min, then increasing the temperature from 180 to 230 ◦C in steps of 10 ◦C/min, then holding for 5 min, then increasing the temperature from 230 to 280 ◦C in steps of 10 ◦C/min, then holding for 5 min, then increasing the temperature from 280 to 310 ◦C in steps of 10 ◦C/min, then holding for 13 min, and the range of scanned masses: 35–700 *m*/*z*. The 1 μL sample was injected into a 10% wt% toluene solution .

#### *2.7. Analysis of Biochars*

The chemical analysis of the mineral part was carried out using an EDX-800HS2 energy dispersive fluorescent X-ray spectrometer (Shimadzu, Kyoto, Japan). Measurement conditions: tube: Rh-anode (50 W), voltage: 50 kV, 15 kV, current: auto, atmosphere—air, measured diameter: 10 mm, measurement time: 100 s. The sample was placed on a Mylar film (6 μm thick) in a cuvette for the X-ray fluorescence analysis, after which the cuvette was placed in the instrument and the measurement was taken.

The volatile matter (VM) and ash content were determined according to ASTM D3175- 89 and ASTM D3174-04, fixed carbon (FC) was calculated from the difference and calculated by Equation (10):

$$\text{FC} = 100 - \text{VM} - \text{Ash} \tag{10}$$

The HHV (MJ/kg) of the biochars were determined using Equation (11) [35]:

$$\text{HHV}\_{\text{biochar}} = (15.59 \cdot \text{VM} + 35.36 \cdot \text{FC} - 0.78 \cdot \text{Ash}) / 100 \tag{11}$$

The basic-acid ratio *B/A* (Equation (12)), slag viscosity index *SR* (Equation (13)), and fouling index *Fu* (Equation (14)) were used to determine the possibility of contamination of the heating surfaces of the power equipment when using biochar as a fuel [36]:

$$B/A = \left(\text{Fe}\_2\text{O}\_3 + \text{CaO} + \text{MgO} + \text{Na}\_2\text{O} + \text{K}\_2\text{O} + \text{P}\_2\text{O}\_5\right)/\left(\text{SiO}\_2 + \text{Al}\_2\text{O}\_3 + \text{TiO}\_2\right) \tag{12}$$

$$\rm{S}\_{R} = 100 \cdot \rm{SiO\_2} / \left( \rm{SiO\_2} + \rm{Fe\_2O\_3} + \rm{CaO} + \rm{MgO} \right) \tag{13}$$

$$F\_{\rm u} = (B/A)/(\text{Na}\_2\text{O} + \text{K}\_2\text{O})\tag{14}$$

#### **3. Results and Discussion**
