In a new concept for biofuel cells Sabine Sané, doctoral candidate in the research training group Micro Energy Harvesting at the Department of Microsystems Engineering (IMTEK) of the University of Freiburg, has found a way to make a species of tree fungus useful for the production of electricity.
The idea is so innovative and unique that the new energy conversion concept was chosen as the cover story of ChemSusChem, a journal for chemistry, sustainability, energy, and materials. Strange for certain but its fact based truth.
ChemSusChem Cover with Fungus for Biofuel Cells the Lead Article.
The background is biofuel cells produce electricity that is environmentally friendly and conserves resources, for instance from organic waste material. A biofuel cell would use enzymes as catalysts to enable electrochemical reactions that generate electricity. In contrast to precious metal catalysts in conventional hydrogen product fuel cells, these enzymes can be obtained at low cost from renewable raw materials. For many technical applications, however, their lifetime is too short.
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The new concept developed by the Freiburg scientists solves this problem by ensuring that the fuel cell is continually resupplied with the biocatalyst. The supplier of the new biofuel cell is Trametes versicolor, a tree fungus that is also found in temperate climates.
The fungus releases the fungal enzyme laccase into a solution surrounding the cathode the positive pole of the biofuel cell where it enables the electrochemical conversion of oxygen. Experiments conducted by the researchers demonstrate that this method can be used to extend the lifetime of the cathodes to as much as a remarkable 120 days, and considerably longer lifetimes now seem possible.
In a contrasting comparison, the cathodes only have a lifetime of 14 days if they are not supplied with more of the enzymes. Since the enzymatic solution can be supplied directly to the fuel cell without time-consuming and expensive purification, the costs are reduced to a minimum. Potential applications for the concept include microbial fuel cells that generate electricity from wastewater, a technology Kerzenmacher’s research group is also developing.
Enzymatic biofuel cells offer great potential for the direct conversion of biochemically-stored energy from renewable biomass resources into electricity. But the enzyme purification is time-consuming and expensive. Additionally, the enzyme’s degrading hinders the long-term use of enzymatic biofuel cells, which limits their lifetime to only a few weeks.
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The Freiburg scientists’ results demonstrate the possibility to establish simple, cost efficient, and mediatorless enzymatic biofuel cell cathodes that do not require expensive enzyme purification procedures.
An enzyme process biofuel cell with an extended lifetime with self-replicating microorganisms providing the electrode with catalytically active enzymes in a continuous or periodic manner now looks like a feasible commercial idea.
Sané’s research was supported by scientists from a research group led by Dr. Sven Kerzenmacher at Prof. Dr. Roland Zengerle’s Laboratory for MEMS Applications.
By. Brian Westenhaus