In recent years, the increasing world population and rapid industrial development has increased the consumption of fossil fuel-derived oils. In response tothe resulting exhaustion of fossil fuel energy, many countries around the world are investigating methods ofwaste energy recovery and reuse, including oil recovery fromthepyrolysisprocessofwastetires. This study investigates the efficiency of an ultrasound-assistedoxidativedesulfurization (UAOD) process in sulfur reduction from diesel oil and thepyrolysisoilfromwastetires treatment. The results indicate that the oxidation efficiency increases as the doses of transition metal catalyst are increased. Longer sonication time also enhances the oxidation process, apparently through the biphasic transfer of oxidants, which results in a high yield of organic sulfur oxidation products. The best desulfurization efficiency was 99.7% (2.67 ppm sulfur remaining) and 89% (800 ppm sulfur remaining) for diesel and pyrolysisoils, respectively, via a process executed by two UAOD units connected in series and combined with solid adsorption using 30 g of Al2O3 in 6 cm columns. These batch experiment results demonstrate clean waste energy recovery and utilization, while fulfilling the requirements of Taiwan EPA environmental regulations (sulfur concentrations less than 5000 ppm).