## 3 Results
### The Effect of UP and PEF on Organic Matter Solubilisation  
The TOC content and COD value can represent the concentration of soluble organic substances, and an increase in these concentrations indicates that pretreatment increases the organic matter penetration into the liquid fraction of the substrate. Before the pretreatment, the TOC and COD concentrations were 1922 \(\pm\) 76 mg/L and 5957 \(\pm\) 71 mg O\({}_{2}\)/L, respectively. Pretreatment of chicken manure using ultrasonic radiation resulted in the release of organic matter expressed in the COD and TOC from the substrate. The solubilisation degree increased with the amount of energy used for the treatment (Figure 2a,c).  
The highest TOC content of 2269 \(\pm\) 60 mg/L was obtained in the UP8 series. The highest COD concentration of 6991 \(\pm\) 86 mg O\({}_{2}\)/L was also obtained in the UP8 series. Using a pulsed electric field to treat lignocellulosic substrate also increased the degree of solubilisation (Figure 2b,d). The highest TOC and COD concentrations (2252 \(\pm\) 48 mg/L and 6973 \(\pm\) 85 mg O\({}_{2}\)/L, respectively) were obtained in the PEF5 series. However, it was observed that in the disintegration samples in which more energy than 0.26 Wh/g TS was used, the solubilisation rate began to decrease. In their study, [PERSON] et al. [28] described the effect of PEF disintegration on the COD concentration in the sewage sludge liquid fraction. They demonstrated that the application of PEF increased solubilisation by 65%. A similar study was conducted by [PERSON] et al. [29], in which the COD content increased by approximately 29% following the application of the PEF treatment of sewage sludge. The effects of ultrasonic radiation treatment of lignocellulosic substrate on TOC and COD solubilisation were also investigated by [PERSON] et al. [25]. The ultrasonic disintegration of Sida hermaphrodita increased the TOC and COD contents in the liquid fraction of the substrate by 24.7 and 21.9%, respectively.  
The cellulose, hemicellulose, and lignin contents in the substrate were determined to calculate the depolymerisation efficiency following the UP and PEF pretreatment. The initial contents of these polymers were 14.62 \(\pm\) 0.86%, 11.49 \(\pm\) 0.77%, and 3.34 \(\pm\) 0.25% TS, respectively. As regards the substrate subjected to ultrasonic radiation pretreatment, the greatest reduction in the polymer content was obtained in the UP8 series, with the resulting values of 12.18 \(\pm\) 1.10%, 9.98 \(\pm\) 0.64%, and 2.87 \(\pm\) 0.17% TS, respectively (Figure 3a). For the substrate disintegrated using a pulsed electric field, the lowest cellulose, hemicellulose, and lignin contents were obtained in the PEF6 series and amounted to 12.33 \(\pm\) 1.36%, 10.13 \(\pm\) 0.51%, and 2.94 \(\pm\) 0.17% TS, respectively (Figure 3b). [PERSON] et al. [30] investigated the effect of UP on biogas production from rice straw and found that the application of frequencies of 37 and 102 kHz reduced the hemicellulose content by approximately 25.78% and 20.82%, respectively. An increase in the power level and exposure time reduced the hemicellulose content. [PERSON] et al. [31] noted, in a study into the UP of _Sida hermaphrodita_, that the cellulose, hemicellulose, and lignin contents decreased with an increase in the amount of energy used for disintegration. Their study showed a reduction in the cellulose, hemicellulose, and lignin contents in the best variant by 33.6%, 27.2%, and14.0%, respectively. Similar results were obtained by [PERSON] et al. when PEF was used as a pretreatment method for grape pomace. The use of PEF did not affect the chemical composition of the substrate, the fibre fraction did not decrease [32]. The results provide evidence that the electroporation phenomenon induced by PEF leads to a drastic increase in permeability, due to the appearance of pores in cell membranes releasing some components into the extracellular environment.