Algae produce an oil which can be processed to create a useful biofuel; however, cost-effective methods of harvesting and removing the water from the algae for it to be processed effectively are challenging.

A team led by Professor Will Zimmerman in the Department of Chemical and Process Engineering developed an inexpensive way of producing microbubbles that can float algae particles to the surface of the water, making harvesting easier, and saving biofuel-producing companies time and money. The research will be published in the journal Biotechnology and Bioengineering.

Professor Zimmerman and his team won the Moulton Medal, from the Institute of Chemical Engineers, for their earlier work which used the microbubble technology to improve algae production methods, allowing producers to grow crops more rapidly and more densely.

We thought we had solved the major barrier to biofuel companies processing algae to use as fuel when we used microbubbles to grow the algae more densely. It turned out, however, that algae biofuels still couldn’t be produced economically, because of the difficulty in harvesting and dewatering the algae. We had to develop a solution to this problem and once again, microbubbles provided a solution.

—Professor Zimmerman

Microbubbles have been used for flotation before: water purification companies use the process to float out impurities, but it hasn’t been done in this context, partly because previous methods have been very expensive.

The system developed by Professor Zimmerman´s team uses up to 1,000 times less energy to produce the microbubbles and, in addition, the cost of installing the Sheffield microbubble system is predicted to be much less than existing flotation systems.

The next step in the project is to develop a pilot plant to test the system at an industrial scale. Professor Zimmerman is already working with Tata Steel at their site in Scunthorpe using CO₂ from their flue-gas stacks and plans to continue this partnership to test the new system.

The research was supported by the University of Sheffield´s Knowledge Transfer Account, funded by the Engineering and Physical Sciences Research Council. It was also supported by the Royal Society Innovation Award 2010, and the Concept Fund of Yorkshire Forward.

Resources

• James Hanotu, HC Hemaka Bandulasena, William B Zimmerman (2012) Microflotation Performance for Algal Separation. Biotechnology and Bioengineering