## 4 Discussion and Conclusions  
The use of pulsed electric field (PEF) to stimulate, condition, or change some properties of biological materials is the subject of numerous studies [36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51]. However, the scientific literature lacks the use of PEF for wood, especially in the context of changes that could affect its energy use. The heat of combustion of firewood is the basic parameter for determining its energy potential. During calorimetric tests, modern calorimeters automatically determine the time-temperature characteristics. They have not been the subject of interest so far, and their role has been limited to only one of the stages of the process determining the value of the heat of combustion. It seems, however, that in addition to the amount of energy produced, the time in which it was released is also important, especially during commercial use of wood as a raw energy material. [PERSON] et al. [52] presented the results of research on the combustion time of coal from the pyrolysis of spruce sawdust pellets, suggesting at the same time that knowledge of the fuel combustion time is necessary for the proper control of this process. The authors obtained results ranging from 4.5 to 6.5 min, and in their opinion, these differences mainly result from the type of fuel used. There is few research on combustion time. The situation is different with the combustion temperature. The authors of such publications [53, 54, 55] believe that the most important role is played by the ignition point and the peak temperature. The aforementioned researchers point out that the first of them, regardless of the type of fuel, has similar values, while the second depends mainly on the content of volatile substances. The time-temperature characteristics of fuel combustion, which is an element of the combustion heat determination process, allow for the analysis of both these parameters, i.e., the duration and temperature obtained at individual stages of the process. The research on the influence of PEF on lignocellulosic material carried out so far indicates the formation of the phenomenon of electroporation causing changes in the structure of the cell membrane. The effect of this is the loss of semi-permeability, which leads to the passage of enzymes hydrolyzing polysaccharides and lignin [29, 30]. Such an effect was already obtained at an electric field of 1 to 10 kV\(\cdot\)cm\({}^{-1}\), with which wood chips were treated [56]. Still, the described mechanisms have not been precisely parameterized [57]. It seems, however, that the same mechanisms may cause differences in the temperature and duration of individual stages of the combustion process. Both the studies presented in this paper and the authors' previous studies [32] have shown that the pulsating electric field affects the temperature-time characteristics of the wood combustion process. The previously published results allowed us to conclude that the dominant factor of changes in the combustion characteristics of biological material treated with PEF is the electric field intensity. However, extending the research to new types of wood and limiting to two combinations of stimulation parameters partially changes the proposed thesis. The key issue to note is the fact that in each of the analyzed variants, the value of the heat of combustion (expressed in energy units per unit of mass) is the same. Slight temperature differences in the subsequent periods of the combustion process between the variants used do not cause changes exceeding the standardized repeatability limit. The situation is different in the case of time measurements. The observed changes are most pronounced in the last period of the combustion process, i.e., from the moment of reaching the maximum temperature to the end of the process. These results seem to be interesting because, as can be concluded from the research, it is possible to modify the time of obtaining thermal energy depending on one's needs.