## 2 Materials and Methods
On the basis of the collected results, it was determined that the average energy consumption for generating a single impulse is 65.6 mJ. During the tests, values ranging from 56.5 mJ to 71.3 mJ were measured, and the determined value of the coefficient of variation was 6.9%. During the measurements of the parameters of the generated high voltage pulse, the value of the initial electric field intensity was changed in the range from 4 to 30 kV\(\cdot\)cm\({}^{-1}\). The recorded waveforms are summarized in Figure 6. The recorded waveforms present the oscillating course of changes in the voltage value of the generated pulse. Its initial amplitude depends on the adopted voltage that triggers the pulse. The time during which the oscillations of the generated impulse were suppressed for all tested impulses amounted to approx. 150-160 \(\upmu\)s.  
Figure 7 presents the visualization made in ANSYS [33], and in particular: distribution of the electric potential in the range from 0 kV to 30 kV (a,b) and the gradients of electric field intensity (c,d) in the vicinity of electrodes (1) for the break time value of 0.5 s (a,c) and 1 s (b,d) from previous discharge. It also demonstrates the figure geometry of the previous discharge channel (2). Figure 6: Voltage pulse as a function of time changes depending on the voltage [32]. Before the samples were placed in the chamber of the Ertec Su-1 stand, the standardized material was stabilized in accordance with the EN 14780:2011 standard (tested material was unified and brought to the air-dry state). Then, within each species of wood, two groups were distinguished, one of which was the so-called control test, where the pulsed electric fuel was not applied, while the other was subjected to the pulsed electric field. In both cases, the moisture content in the analytical state was determined in accordance with EN ISO 18134-3:2015 standard [34]. The test portion of the material (minimum 1 g weighing to the nearest 0.1 mg.) is dried at a temperature of (105 \(\pm\) 2) \({}^{\circ}\)C in the air atmosphere until the constant mass is achieved. Constant mass was defined as a change not exceeding 1 mg in mass during a heating period of 60 min. The percentage of moisture was calculated from the loss in mass of the test portion. In addition, for the sample that was subjected to the pulsed electric field interaction, the moisture content of the wood was determined again before the combustion heat test was conducted. Such a procedure made it possible to exclude the influence of the differentiation of the controlled and processed material moisture content on the basis of the obtained results of the combustion heat. The value of 0.1% was adopted as the limit of repeatability. The combustion heat of the tested biological material was determined with the use of a calorimetric bomb combustion method, based on the EN ISO 18125:2017 standard [18]. A weighed portion of the analysis sample (1 \(\pm\) 0.1) g was burned in high-pressure oxygen (the bomb filled to 3 MPa by pure oxygen with an assay of at least a volume fraction of 99.5%, and free from the combustible matter) in a bomb calorimeter. The effective heat capacity of the calorimeter was determined in calibration experiments by combustion of certified benzoic acid under similar conditions, accounted for in the certificate (ambient temperature equal to 25 \({}^{\circ}\)C). The corrected temperature rise was established from observations of temperature before, during and after the combustion reaction took place. Water (distilled, 1.0 \(\pm\) 0.1 mL) was added to the bomb initially to give a saturated vapor phase prior to combustion, thereby allowing all the water formed, from the hydrogen and moisture in the sample, to be regarded as liquid water.