## 3 Results
### The Effect of UP and PEF on BMP  
Figure 4 presents the experimental results of the chicken manure methane potential. The BMP from the raw substrate with no pretreatment was 210.42 \(\pm\) 7.92 mL/g VS. The biogas yield was 307.29 \(\pm\) 13.65 mL/g VS. The application of ultrasonic radiation pretreatment increased BMP. The highest BMP was obtained in the UP8 series, in which \(250.06\pm 8.68\) mL/g VS was obtained, with biogas production amounting to 365.07 \(\pm\) 11.71 mL/g VS. Regarding the BMP rate (r), the highest value of 55.06 mL/g VS daily was obtained in the UP7 series. The highest reaction rate constant (k) value of 0.14 1/d was also observed in this series (Figure 3). The effect of UP on the productivity of biogas from rice straw was investigated by [PERSON] et al. [30]. When rice straw was treated at a frequency of 37 and 102 kHz, the biogas production values during the 45-day anaerobic digestion amounted to 250.36 and 243.79 mL CH4/g VS, respectively, which accounted for an increase of approxi  
Figure 2: The TOC (**a,b**) and COD concentrations (**c,d**) in the liquid fraction of the substrate. Superscript letters (a, b, c) denote significant differences ([PERSON]’s RiR test, \(p<0.05\)). mately 21.95% and 18.75% compared to the straw subjected to no treatment. Pretreatment at 37 kHz ensured a greater methane yield than at 102 kHz. The difference between the results of [PERSON] et al. and those obtained for chicken manure was probably due to the twice as high content of hemicellulose (41.7%) and cellulose (37.5%) in the substrate compared to chicken manure. [PERSON] et al. [33] compared physical pretreatment methods using ultrasounds and hydrothermal cavitation in mesophilic anaerobic digestion of cattle manure mixed with wheat straw. Their study demonstrated that the application of UP allowed biogas production to increase by 64.2%. Figure 3: The cellulose, hemicellulose, and lignin contents in the substrate. Superscript letters (a, b) denote significant differences (Tukey’s RiR test, \(p<0.05\)). (a) Ultrasound Pretreatment (b) Pulsed Electric Field Pretreatment. Applying a pulsed electric field for the pretreatment of the lignocellulosic substrate also increased methane production. The highest biogas and BMP coefficients in the samples  
Figure 4: BMP from a substrate pretreated with UP, along with the kinetic parameters of the first-order model. disintegrated using PEF were noted in the PEF6 series and amounted to 366.99 \(\pm\) 14.18 and 248.90 \(\pm\) 9.29 mL/g VS, respectively (Figure 5). It was also observed that the BMP and biogas productivity dropped slightly in subsequent series. The application of PEF disintegration did not affect the methane content in biogas. The highest methane production rate (r) value of 104.17 mL/g VS d for the samples subjected to PFE pretreatment was obtained in the PEF8 series. Regarding the reaction rate constant (k) value, the highest value of 0.43 1/d was also obtained in the PEF8 series (Table 2). [PERSON] et al., while studying the methane fermentation of agricultural waste, obtained constant k values of 0.15 1/d for apple waste, 0.23 1/d for sunflower, and 0.29 1/d for orange waste [34]. [PERSON] et al. estimated parameters for different kinetic models describing the production of u and methane from bacterial-algal biomass co-fermented at different ratios with cellulose. For first-order kinetic, they obtained results for a k value ranging from 0.055 1/d to 0.091 1/d [35]. The methane content of biogas was unaffected by PEF disintegration or UP. The percentage of methane in biogas ranged from 67.0% to 69.3% (Figure 6). Figure 5: _Cont._  
[PERSON] and [PERSON] [22] conducted a study involving pretreatment using a pulsed electric field to determine the effect of PEF on methane production. The test substrates included leachate from waste landfills and fruit and vegetables. In order to investigate the effect of pretreatment on BMP using the biochemical methane potential test, the following three treatment intensities were applied: 15, 30, and 50 kW h/m\({}^{3}\).