Abstract
The microbial fuel cell (MFC) technology relies on energy storage and harvesting circuitry to deliver stable power outputs. This increases costs, and for wider deployment into society, these should be kept minimal. The present study reports how a MFC system was developed to continuously power public toilet lighting, with for the first time no energy storage nor harvesting circuitry. Two different stacks, one consisting of 15 and the other 18 membrane-less MFC modules, were operated for 6 days and fuelled by the urine of festival goers at the 2019 Glastonbury Music Festival. The 15-module stack was directly connected to 2 spotlights each comprising 6 LEDs. The 18-module stack was connected to 2 identical LED spotlights but going through 2 LED electronic controller/drivers. Twenty hours after inoculation the stacks were able to directly power the bespoke lighting system. The electrical energy produced by the 15-module stack evolved with usage from ≈280 mW (≈2.650 V at ≈105 mA) at the beginning to ≈860 mW (≈2.750 V at ≈300 mA) by the end of the festival. The electrical energy produced by the LED-driven 18-module stack increased from ≈490 mW at the beginning to ≈680 mW toward the end of the festival. During this period, illumination was above the legal standards for outdoor public areas, with the 15-module stack reaching a maximum of ≈89 Lx at 220 cm. These results demonstrate for the first time that the MFC technology can be deployed as a direct energy source in decentralised area (e.g. refugee camps).
Highlights
The first report on microbial fuel cell (MFC) was published over 100 years ago [1], yet the technology only caught the attention of scientists with the discovery of microbes capable of electron transfer without external redox mediators [2,3]
The calibration experiment aimed at finding an equilibrium between the number of LEDs and the electrical configuration of an S-MFC stack whilst maintaining stable and continuous operation
Based on the LED characteristic (Fig. 4b) of 30 Lx and on the limited height available between the troughs outlets and the soakaway, the aim was for a system of 300 mA. This meant that the stack was assembled with 5 cascades electrically connected in series, each cascade comprising 3 modules electrically connected in parallel (Fig. 3b, 15M_S-MFC_B)
Summary
The first report on microbial fuel cell (MFC) was published over 100 years ago [1], yet the technology only caught the attention of scientists with the discovery of microbes capable of electron transfer without external redox mediators [2,3]. MFCs transform chemical energy in organic matter directly into electricity through bacterial metabolism. A vast range of organic matter both in solid and liquid forms can be used as MFC feedstock (fuel), which includes various types of domestic and industrial waste. I.e. simultaneous waste treatment and energy generation, makes the technology stand out amongst other renewable energy technologies [6]. MFCs can be used for the recovery of resources such as phosphorus [7], nitrogen [8], potassium and copper [9], and as bio-sensors detecting various elements, such as bioactive compounds (e.g. formaldehyde) in drinking water [10] or
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