Waste to Energy: An experimental comparison of burning the waste-derived bio-oils produced by transesterification and pyrolysis methods

In the present research, waste cooking oil biodiesel (WB) and waste pyrolysis oil (WPO) are produced via transesterification and pyrolysis methods. Then the produced WB and WPO are blended at the volumetric percentages of 25, 50, 75, and 100% into the conventional diesel fuel. These fuel blends are tested on a single-cylinder diesel engine under the varying engine loads (1, 2, 3, and 4 kW) at a constant crankshaft speed of 1500 rpm. The results show that both WB and WPO blended fuels decrease the brake thermal efficiency and higher exhaust gas temperature than diesel fuel. As the WB content in the test fuel increases, CO, HC, and smoke emissions gradually decrease due to the high oxygen content of WCO, but NOx emission increases. In terms of exhaust emissions, the reverse trend is noticed for WB blended test fuels (high CO, HC, and smoke, but low NOx) with the lack of oxygen atoms for WPO substitutes. As the percentage of WPO in the test fuel is increased, CO, HC, and smoke emissions gradually increase in comparison to those of diesel fuel, while NOx emissions exhibited a reverse trend. In comparison to that of reference diesel fuel, the highest thermal efficiency declines are found to be 22% for WB100 and 19% for WPO100. WPO100 leads to the significant increment in the HC, CO, and smoke emissions by 59, 36, and 31%, respectively. Compared to diesel fuel, WB100 ensures the highest CO, HC, and smoke emission reduction by 45, 62, and 47%, respectively. On the other hand, the maximum increase in NOx emission is found to be 46% for WB100 test fuel, while the maximum decrease is found to be 25% for WPO100 test fuel as compared to that of diesel fuel. In terms of engine performance and exhaust pollutants excluding NOx emission, it is well-noticed that the WB substitutes present more promising results than those of WPO substitutes. Accordingly, the present research proves that the transesterification method is more suitable for biofuel production than the pyrolysis method.