|The bioreactor. Note the fan at right, powered by a fuel cell using the resulting H2. The gas passes via a glass “trap” to capture excess moisture.|
In a feasibility study funded by the UK’s Engineering and Physical Sciences Research Council (EPSRC), bioscientists at the University of Birmingham have demonstrated that certain bacteria can produce hydrogen gas as they consume high-sugar waste produced by the confectionery industry.
The sweet waste was supplied by Birmingham-based international confectionery and beverage company Cadbury Schweppes plc, a partner in the initiative. An economic assessment undertaken by another partner, C-Tech Innovation Ltd, showed that it should be practical to repeat the process on a larger scale.
As well as energy and environmental benefits, the technique could provide the confectionery industry (and potentially other foodstuff manufacturers) with a useful outlet for waste generated by their manufacturing processes. Much of this waste is currently disposed of in landfill sites.
In this project, diluted nougat and caramel waste was introduced into a 5-liter demonstration reactor. The bacteria, which the researchers had identified as potentially having the right sugar-consuming, hydrogen-generating properties, were then added.
An adapted form of a harmless strain of E. coli broke down the confectionary waste, producing hydrogen and organic acids. Naturally occuring Rhodobacter sphaeroides then was introduced into a second reactor to convert the organic acids into more hydrogen.
The hydrogen produced was fed to a fuel cell, in which it was allowed to react with oxygen in the air to generate electricity. Carbon dioxide produced in the first reactor was captured and disposed of safely, preventing its release into the atmosphere.
Waste biomass left behind by the process was removed, coated with palladium and used as a catalyst in another project, funded by the Biotechnology and Biological Sciences Research Council (BBSRC), aimed at identifying ways of removing pollutants such as chromium (VI) and polychlorinated biphenyls (PCBs) from the environment.
The reactors used by this parallel initiative also required hydrogen and this was supplied by the confectionery waste initiative too, further underlining the benefits offered by the new hydrogen production technique.
Hydrogen offers huge potential as a carbon-free energy carrier. Although only at its initial stages, we’ve demonstrated a hydrogen-producing, waste-reducing technology that, for example, might be scaled-up in 5-10 years’ time for industrial electricity generation and waste treatment processes.—Professor Lynne Macaskie, University of Birmingham School of Biosciences
As well as confectionery waste, the study tested the viability of potato extract as a feedstock for hydrogen-producing bacterial action. This did not yield promising results as the potato starch proved difficult to break down with the bacteria used.
The team is now engaged in follow-up work which will produce a clearer picture of the overall potential for turning a wider range of high-sugar wastes into clean energy using the same basic technique.
The 15-month feasibility study—Biological Hydrogen Production from Crops and Sugar Wastes—received EPSRC funding of nearly £24,000 ($US45,000).
“Applications of bacterial hydrogenases in waste decontamination, manufacture of novel bionanocatalysts and in sustainable energy”; L.E. Macaskie, V.S. Baxter-Plant, N.J. Creamer, A.C. Humphries, I.P. Mikheenko, P.M. Mikheenko, D.W. Penfold and P. Yong; Biochem. Soc. Trans. (2005) 33, (76–79)