Microbubbles provide new boost for biofuel production

The technique builds on previous research in which microbubbles were used to improve the way algae is cultivated.

Algae produce an oil which can be processed to create a useful biofuel. Biofuels, made from plant material, are considered an important alternative to fossil fuels and algae, in particular, has the potential to be a very efficient biofuel producer. Until now, however, there has been no cost-effective method of harvesting and removing the water from the algae for it to be processed effectively.

Now, 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. They have 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 is set to be published in Biotechnology and Bioengineering on 26 January 2012.

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," 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."

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 1000 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.

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."

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.

1. The paper, entitled "Microflotation Performance for Algal Separation", by James Hanotu, HC Hemaka Bandulasena, William B Zimmerman is published in Biotechnology and Bioengineering on 26 January 2012.

2. The Faculty of Engineering at the University of Sheffield - the 2011 Times Higher Education's University of the Year - is one of the largest in the UK. Its seven departments include over 4,000 students and 900 staff and have research-related income worth more than £50M per annum from government, industry and charity sources. The 2008 Research Assessment Exercise (RAE) confirmed that two thirds of the research carried out was either Internationally Excellent or Internationally Leading.

The Faculty of Engineering has a long tradition of working with industry including Rolls-Royce, Network Rail and Siemens. Its industrial successes are exemplified by the award-winning Advanced Manufacturing Research Centre (AMRC) and the new £25 million Nuclear Advanced Manufacturing Research Centre (NAMRC). To find out more, visit: http://www.shef.ac.uk/faculty/engineering/

3. The Engineering and Physical Sciences Research Council (EPSRC) is the main UK government agency for funding research and training in engineering and the physical sciences, investing £800 million a year in a broad range of subjects - from mathematics to materials science, and from information technology to structural engineering. www.epsrc.ac.uk

The EPSRC has awarded twelve Knowledge Transfer Accounts (KTAs) to UK Universities. KTAs aim to overcome barriers to collaboration between universities and other public and private sector organisations, and to ensure that the outputs of EPSRC research deliver the maximum economic and societal benefit to the UK.