(Invited) Microbial Fuel Cell Development for Practical Applications Robotics, Urinals and Novel Transistor Analogy
Authors: Ieropoulos Ioannis , Gajda Iwona , You Jiseon , Melhuish Chris , Greenman John 
Published: February 2020

Microbial fuel cells (MFCs) convert organic waste directly into electricity, which is a competitive advantage over other energy generating systems. It is a technology that offers an environmentally friendly service at high-energy conversion efficiency. Full commercialization has yet to be achieved in areas such as wastewater treatment and remote power applications, due to challenges with the level of power output from individual units, cost of materials and scale-up. Unlike some conventional chemical fuel cells that are now fully commercial, MFCs are still at pilot scale testing [1-4]. However, several smaller-scale MFC-based applications have been implemented including, biochemical oxygen demand (BOD) measuring sensors (HABS2000, KORBI), benthic MFCs as on-site power sources for conventional sensors [5-7] and power sources for small electronic gadgets, mobile phones and robots, as well as Pee Power urinals [3, 8, 9].
Single MFCs can generate on average <0.5V at maximum power transfer, which is lower than what electronic circuits and peripheral devices require. Scaling up is therefore critical for the technology to be implemented in practice and find a route to market, and for this purpose several approaches have been proposed. One approach is to enlarge individual units to scale [2], and the second is to miniaturise individual units [10] and stack collectives of these small units together [11, 12]. Independent of size or volume, more than one unit will need to be connected together to increase the voltage and current up to operational levels. This can be in series (voltage boost), parallel (current boost) or a combination of series and parallel (voltage + current boost).
As an alternative to these common connections, a novel method of MFC configuration is suggested in this work, with the introduction of added electrodes – so-called “pins”. The purpose of this type of connection is to enable control and monitoring of the MFC by modulating the physicochemical environment and the idea is derived from electronic transistors and control theory.
This long-term study has been focusing on the development of MFCs for practical applications and scale-up. Through this approach, a novel transistor analogy is proposed with potential for improving power, controlling biochemical reactions, sensing and unconventional computation.

Acknowledgements

This work has been supported by the UK EPSRC, grant numbers EP/I004653/1 and EP/L002132/1 and
Bill & Melinda Gates Foundation, grant no. OPP1094890.

References

[1] Osman, M. H., Shah, A. A. and Walsh F. C. Recent progress and continuing challenges in bio-fuel cells. Part II: Microbial. Biosens Bioelectr 2010;26:953–63.
[2] Logan, B. E. Appl Microbiol Biotechnol. 2010;85:1665–71.
[3] Reinvent the Toilet Fair: India, 2014. http://www.impatientoptimists.org/Posts/2014/03/Reinvent-the-Toilet-Fair-India--Progress-Innovation-Excitement#.VmuEY9DWvrc (visited 11 December 2015).
[4] University of the West of England. “Pee-power” to light camps in disaster zones 2015.
[5] Du, Z., Li, H. and Gu. A state of the art review on microbial fuel cells: A promising technology for wastewater treatment and bioenergy. Biotechnol Adv. 2007;25:464-72.
[6] Reimers, C. E., Girguis, P., Stecher, H. A., Tender, L. M., Ryckelynck, N. and Whaling, P.Microbial Fuel Energy from an Ocean Cold Seep. Geobiol. 2006;4:123-36.
[7] Beyenal, H. and Babauta, J. (2015) Large-Scale Benthic Microbial Fuel Cell Construction, Deployment, and Operation, in Biofilms in Bioelectrochemical Systems: From Laboratory Practice to Data Interpretation, John Wiley & Sons, Inc, Hoboken, NJ, USA. doi: 10.1002/9781119097426.ch11
[8] Ieropoulos, I., Greenman, J., Melhuish, C. and Horsfield, I. (2010) EcoBot-III – A Robot with Guts. Proceedings of ALife XII, MIT Press, 733-40.
[9] Ieropoulos, I. A., Ledezma, P., Stinchcombe, A., Papaharalabos, G., Melhuish, C. and Greenman, J. Waste to real energy: the first MFC powered mobile phone. PCCP. 2013;15:15312-16.
[10] Ringeisen, B., Henderson, E., Wu, P. K., Pietron, J., Ray, R., Little, B., Biffinger, J. C. and Jones-Meehan, J. M. High Power Density from a Miniature Microbial Fuel Cell Using Shewanella oneidensis DSP10. Env Sci Technol. 2006;40:2629-34.
[11] Cohen, B. The Bacterial Culture as an Electrical Half-Cell. J. Bacteriol. 1931.
[12] Ieropoulos I, Greenman J, Melhuish C. Microbial fuel cells based on carbon veil electrodes: Stack configuration and scalability. Int J Energy Res 2008;32:1228–40.