The increasing pollution levels, rising energy demand, and the inadequacy of conventional fuels have spurred interest in alternative sources of fossil fuel supply and demand.This problem has shifted the focus towards the examination of a promising sustainable alternativefor diesel fuels. In this sense, biodiesel canbe a more suitable candidate forenergy, environmentally harmless, and cost-competitive approach to respond to the energy demand.The application of ultrasonic energy in biodiesel production viatransesterification has been endorsed as an efficient approach that improves mass transfer factorsresulting in decreased reaction times and potentially lower process expense.This study investigates the advancements in ultrasonic energy for biodiesel generation from various raw materials utilizing different catalysts. A critical assessment of the current approach is furnished, emphasizing the application ofultrasonic irradiation.Besides, in order to better understand ultrasonic energy, each ultrasonic cavitation (UC)and hydrodynamic cavitation (HC)is discussed. Regarding each approach, the fundamental concepts are discussed in detail. Generally, the present study aims at conveyinga comprehensive overviewof ultrasonic energy usage in transesterification reactions and furnishingan outlook on prospective developments inthe technology.
