Electricity production from biomass: a bacteria powered battery

Ashihara, H., Mandy, C. and Cornish, J.C.L. (2004) Electricity production from biomass: a bacteria powered battery. In: 42nd Annual Conference of the Australian and New Zealand Solar Energy Society (ANZSES 2004), 30 November - 3 December, Perth, Western Australia

Abstract

The conversion of biomass directly to electricity by the action of bacteria has been known for twenty years or so, but this benign, environmentally friendly electricity source is now being actively investigated with promising results.
The study presented here had the aim of investigating the possibility of setting up a bio-battery, using locally available bacteria and measuring the battery’s properties including its power output.
Bacteria of unknown species were harvested together with an iron and nutrient rich sample of black sediment from a suburban fishpond. The electrodes were formed from strands of carbon fibre, consisting of many individual filaments, to provide a large area substrate for the bacteria to colonise. The anode was immersed in sediment, while the cathode was suspended in plain water above and parallel to the anode. The process of setting up the cells proved to be remarkably easy and a small voltage was developed immediately.
The battery of four cells in series has performed flawlessly now for 16 weeks and after an initial increase has maintained a high stable voltage over a period of time. The voltage output of individual cells has fluctuated, but has reached up to nearly 0.8 V per cell. The battery is currently capable of maintaining a constant current of over 4 μA at an output voltage of 1.6 V. The calculated energy generated by the battery during the second six weeks of operation is 28 joules. Biomass has an energy content of up to 20 MJ/kg, so even a few grammes of material used in each cell will give it a long lifetime.
The voltage output of 1.6 V is quite useable. However, it is the current that needs to be improved in order to increase the output power. Present investigations involve increasing the area of the electrodes to see if, by providing more space for the bacteria, a greater current will result.
To utilise the present battery would require a component such as a capacitor, or a rechargeable battery to continuously store energy at the low rate produced by the bio-battery until it has sufficient to provide a higher power for a short period of time in a suitable application. Thus, a LED could be used to provide periods of illumination or the power could be used for short periods of time to run an electric motor, a piezoelectric audio device, a radio receiver or a radio transmitter.

Item Type:	Conference Paper
Murdoch Affiliation(s):	School of Engineering and Energy
URI:	http://researchrepository.murdoch.edu.au/id/eprint/21094

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