## 2 Materials and Methods  
The research material selected for analysis in this study was sawdust from four broad-leaved trees, i.e., birch, oak, linden, and ash tree. The sawdust was subjected to a pulsed electric field with an electric field intensity of 25 kV\(\cdot\)cm\({}^{-1}\) and the number of 300 capacitor discharges (pulses) and an electric field intensity of 30 kV\(\cdot\)cm\({}^{-1}\), where the number of 300 capacitor discharges (pulses) was also used. The results were compared with the sample not treated with PEF. The selected parameters were the result of previous studies [31], in which the applied variants seemed to be the most promising, i.e., they gave the most diverse results. A constant time between successive capacitor discharges (pulses) was assumed, regardless of the test variant used. The entire research process, i.e., preparation of the material for research, its conditioning, and measurement of the calorific value was carried out at the Laboratory of Experimental Research Techniques for Biological Products and Raw Materials, which is part of the University of Agriculture in Krakow. In addition to comparing the results of studies of individual broadleaved tree species with a different number of discharges (pulses), a so-called blank sample was also introduced. It was made of a material that had not been treated with PEF. Conditioning of sawdust with pulsed electric field was performed on the Ertec Su-1 stand (Figure 1a) used daily as a tool for low-temperature inactivation of microorganisms in food products. For the purposes of this research, minor adjustments were made to the stand. The PEF interaction device consists of a high-voltage pulse generator, a working chamber, and a control system. In the apparatus used in these tests, it is possible to generate a voltage up to 31 kV, which--with a distance between bases of the cylinder of c--gives a maximum electric field strength of 31 kV\(\cdot\)cm\({}^{-1}\). The station is equipped with control programming that enables process conditions to be set for several hundred PEF pulses, with widths from 1 to 400 \(\upmu\)s and spacing between them in the range of 1-10 s. The generated pulses have an exponential shape. The average energy consumption when generating a single impulse is 65.6 mWh, with a variation coefficient of 6.9% [31]. A detailed description of the devices used in this study was described in the previous article by the authors [32], where analogous studies were carried out for sawdust from coniferous trees. Properly prepared sawdust, constituting the test material, was introduced into a stationary sterilization cell (Figure 1b). The material tightly filled the 1 cm wide space between the steel cylinders. The remainder of the cell is made of Teflon dielectric. The cells were introduced into the stand chamber, where the electrodes were attached to the bases of the cylinder. In the presented research, stimulation with a pulsed electric field was used with a pulse time width of 160 us and a time between successive discharges equal to 10 s.  
In accordance with the requirements set by the accredited laboratories, before starting the experiments, the material was homogenized and dried to an air-dry state in accordance with the EN 14780:2017-07 standard [33]. In accordance with the assumption presented earlier, a control sample, also known as a blank sample, was separated from the stabilized material (within each species of wood). In each of the variants, the moisture content in the analytical state was tested in accordance with the EN ISO 18134-3:2015 standard [34]. For samples of the material subjected to the pulsed electric field, the measurement of analytical moisture was carried out both before and after stimulation. This was to exclude any discrepancies in the obtained results of the heat of combustion, which, if the control was not carried out, could be caused not by the action of PEF itself, but by a reduction of the water content in the tested material.