Researchers from the Agricultural Engineering Department of the University of Missouri (United States) are investigating the use of ultrasound to hasten the production time for making biodiesel. Ultrasound is a high frequency sound which is inaudible to the human ear. Ultrasound waves are generated by a machine called, an "ultrasound generator". In the conventional method of biodiesel production, vegetable oil (such as soybean, or coconut, or jatropha) is mixed and allowed to react with an alcohol (often, methanol) and heated at high temperature for about one to two hours. Under the proposed process, an ultrasound generator transmits ultrasonic waves onto a mixture of oil and methanol. The ultrasound waves transmitted into the reaction mixture generate microbubbles, which eventually collapse. The microbubble-collapse is usually accompanied by momentary bursts of high temperature and pressure, which are sufficient to drive a chemical reaction. In the oil/methanol mixture, ultrasound releases the fatty acids from the oil, and biodiesel formation occurs when the released fatty acids react with the methanol. The ultrasound process can reportedly make biodiesel within 5 minutes. Assistant Professor Bulent Koc of the University of Missouri, has successfully used the technique on different vegetable and cooking oils, including soybean, sesame, peanut, and canola oils. He said that the main challenge with the use of ultrasonic waves, is to control of the heat generated, which can damage the ultrasound generator. The problem could be fixed by attaching a cooling system around the ultrasonic device..