UK researcher develops microbubble algae dewatering system

By Erin Voegele | February 03, 2012

Researchers at U.K.-based University of Sheffield have developed a microbubble technology that could bring down the cost of algae biofuels by cost-effectively dewatering algae. According to the university, the solution builds on previous research in which microbubbles were used to improve the way algae is cultivated. The research team, led by Will Zimmerman, a professor in the department of chemical and biological engineering, has developed an inexpensive method to produce microbubbles that can float algae cells to the surface of the algae solution, which makes harvesting easier, cheaper and faster. Research on the process has been published in the journal Biotechnology ad Bioengineering.

In 2010, Zimmerman won the Royal Society Mercer Award for Innovation for his microbubble technology, which was then used to improve algae production methods by allowing producers to grow algae crops more rapidly and densely. A video provided to Biodiesel Magazine and Biorefining Magazine by the University of Sheffield explains how the microbubble technology works.

According to the video, microbubbles are miniature gas bubbles of less than 50 microns in size. Their small size allows them to remain suspended in water for much longer than larger bubbles. In addition, the high surface area to volume ratio of the microbubbles allows more gas to dissolve in solution.

In the video, Zimmerman explains how the microbubbles are created using his technology. The process features a fluidic oscillator with a main jet of air coming into the oscillator, and two outlets leaving it. According to Zimmerman, the fluidic oscillators are arranged so that the feedback loop switches the flow from one side to the other in a back-and-forth fashion. The frequency of the oscillation can be altered by changing the size of the feedback loop.

The video further explains that the fluidic oscillator allows a flow of gas to be turned into pulses that alternate between two outlets. The pulses are actually what allow the microbubbles to be created. While other microbubble technologies do exist, Zimmerman’s is more energy efficient because pulsing the gas uses less energy than a steady flow of the gas.

According to information released by the University of Sheffield, microbubbles have been used for floatation before, primarily by water purification companies. In that application, the microbubbles are used to float out impurities. However, the process has not been adopted by those in the algae industry on a large scale because previous methods to make microbubbles have been too expensive.

Alternatively, Zimmerman’s system is estimated to use up to 1,000 times less energy than existing microbubble solutions. In addition, the cost of the system itself is expected to be significantly lower. The use of the system to dewater algae is scheduled to be tested at an existing pilot algae production system installed at Tata Steel. That pilot facility has been used to prove the ability of microbubble technology to improve algae growth.