U. of Idaho's Biodiesel Tech Note addresses ultrasonic technology

The Biodiesel Education Program at the University of Idaho has published a new Biodiesel Tech Note focused on ultrasound-assisted biodiesel production. According to B. Brian He, a faculty member in university’s Biological and Agricultural Engineering Department, the Biodiesel Education Program decided to investigate ultrasonic biodiesel production due to interest from those in the industry. "We received a lot of emails and telephone calls about the technology," He said.

The tech note states that ultrasound has been shown to be a useful tool in the mixing of liquids that tend to separate. Ultrasonic waves mix the fluids at a micro-level, which can vastly increase reaction rates. In fact, the Biodiesel Education Program’s research has found that ultrasonic reactors have been shown to complete the biodiesel conversion in as little as five to 30 minutes on the lab scale, He said. The tech note also shows that current ultrasonic technology users have claimed that less catalyst is needed to perform reactions.

Information published by the Biodiesel Education Program describes how ultrasonic technology works. Sound waves ranging anywhere from 24 to 1300 kilohertz (kHz) transfer energy into a fluid media, creating violent vibrations. Those vibrations form cavitation bubbles, which collapse causing sudden contraction of the fluid. The collapse produces very intense mixing.

While several ultrasonic wave intensities have been evaluated, the tech note said that more research is needed to determine the optimum levels of ultrasonic power input for biodiesel production. “Using a higher frequency and intensity does not necessarily increase the speed or effectiveness of the biodiesel reaction,” said the Biodiesel Education Program in the note. “Most experiments have used 20-24 kHz for biodiesel processing.

In addition to faster processing, ultrasonic biodiesel production could prove beneficial as far as lower energy needs. According to He, the ultrasonic process seems to require less energy than conventional biodiesel processing. The tech note said that a great deal of energy savings could be achieved because the liquids do not need to be heated in order for the reaction to be completed using ultrasonic technology. However, the note also states that using both heat and ultrasonic technology has been shown to result in a faster, more complete reaction.

He said that it is possible we could see larger scale commercial biodiesel production using ultrasonic technology within the next five years. It will depend on if the technology advances sufficiently to provide enough benefit to incentivize members of the industry to switch.

A full copy of the Biodiesel Tech Note can be downloaded from the Biodiesel Education Program’s website.