Could microalgae be the answer for biofuel production after all?

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A technique using microbubbles could mean that harvesting microalgae for biofuels could be about to become much more cost effective.

In a recent story, PFK reported that Brown macroalgae could be the new answer to biofuel production, citing that the amount of energy required to produce oil from microalgae was a major stumbling block.

However, a team led by Professor Will Zimmerman in the Department of Chemical and Process Engineering at the University of Sheffield, believe they have solved the problem of the costs involved in harvesting microalgae for biofuels. They have developed a technique that builds on previous research, which uses a cost-effective method to produce microbubbles to float the algae particles to the surface of the water. This process makes it easier to harvest the algae and saves time and money.

Professor Zimmeran and his team have previously been awarded the Moulton Medal for earlier work that demonstrated the use of microbubbles to improve algae production methods.

"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," explains Professor Zimmerman.

"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."

Using microbubbles for flotation is not a new technology; marine keepers with protein skimmers will be all too familiar with the concept of using air to remove organic particulate from water, and water companies use the process to remove impurities.  However, it hasn’t been used for algae cultivation as previous methods of "dewatering" have proven to be very expensive.

The Sheffield microbubble system uses up to 1000 times less energy to produce the microbubbles, and it is predicted it will cost a lot less to install.

The next step in the project is to create a pilot plant that can test the system at the industrial level. The team already has a working relationship with Tata Steel in Scunthorpe, using CO2 from Tata’s flue-gas stacks, so the plans are to continue this partnership to test the new system.

Dr. Bruce Adderley, Manager of Climate Change Breakthrough Technology at Tata, said: "Professor Zimmerman's microbubble-based technologies are exactly the kind of step-change innovations that we are seeking as a means to address our emissions in the longer term, and we are delighted to have the opportunity to extend our relationship with Will and his team in the next phase of this pioneering research."

For further information see the paper: Microflotation Performance for Algal Separation, by James Hanotu, HC Hemaka Bandulasena, William B Zimmerman.

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