Conventional methods for biogas production, particularly anaerobic digestion, are often characterized by slow processing times and limited output efficiency. In contrast, advanced process intensification techniques present a promising alternative, enabling significantly faster conversion rates and enhanced yields. This study explores the improvement of methane quality through ultrasonic pretreatment during the co-digestion process. A predictive mathematical model was developed using response surface methodology (RSM) to estimate methane yield. The analysis considered three independent variables: ultrasonic power (500, 1000, and 1500 W), sonication time (30, 45, and 60 min), and temperature (40 degrees C, 50 degrees C, and 60 degrees C) at three different levels. The second-order quadratic model demonstrated excellent predictive accuracy, with an adjusted R2 of 98.45 %. Numerical optimization identified the optimal conditions for methane yield: ultrasonic power of 1437.8 W, sonication time of 43.7 min, and a temperature of 55.85 degrees C, resulting in a maximum yield of 70.758 %. Validation experiments confirmed the model's reliability, with a maximum deviation of 2.06 %. Furthermore, this study explored the effects of biogas and hydrogen supplementation on a single-cylinder diesel engine running on a pyrolysis oil/diesel blend in dualfuel mode. Results showed an increase in brake thermal efficiency (BTE) by 14.65 % and a reduction in brakespecific energy consumption (BSEC) by 15.38 % for the B20H2 (2LPM) blend compared to baseline diesel operation. The addition of hydrogen gas led to a 25 % reduction in CO and a 13.78 % reduction in HC emissions at 75 % load, while NOx emissions increased slightly by 1.5 % for the B20H2 (2LPM) blend but decreased by 3.84 % when blended with biogas. These findings suggest that ultrasonic pretreatment significantly enhances methane yield, and the supplementation of hydrogen gas and biogas can reduce harmful emissions while improving diesel engine performance in dual-fuel operation.
