Abstract
One of the challenges in Microbial Fuel Cell (MFC) technology is the improvement of the power output and the lowering of the cost required to scale up the system to reach usable energy levels for real life applications. This can be achieved by stacking multiple MFC units in modules and using cost effective ceramic as a membrane/chassis for the reactor architecture. The main aim of this work is to increase the power output efficiency of the ceramic based MFCs by compacting the design and exploring the ceramic support as the building block for small scale modular multi-unit systems. The comparison of the power output showed that the small reactors outperform the large MFCs by improving the power density reaching up to 20.4 W/m3 (mean value) and 25.7 W/m3 (maximum). This can be related to the increased surface-area-to-volume ratio of the ceramic membrane and a decreased electrode distance. The power performance was also influenced by the type and thickness of the ceramic separator as well as the total surface area of the anode electrode. The study showed that the larger anode electrode area gives an increased power output. The miniaturized design implemented in 560-units MFC stack showed an output up to 245 mW of power and increased power density. Such strategy would allow to utilize the energy locked in urine more efficiently, making MFCs more applicable in industrial and municipal wastewater treatment facilities, and scale-up-ready for real world implementation.
Highlights
Observing the continuously increasing demand for water and energy in the world, alternative sources are needed to meet the requirement of a growing population
The small reactors made of fine fired clay (S FFC14) generated 0.43 mW and 0.69 mW when the anode surface area was doubled (S fine fire clay (FFC)) to keep the same anode to cathode area ratio used in large terracotta MFC (LargeT) and small terracotta (SmallT) (Table 1)
The maximum performance (Figure 3D) achieved during polarization experiment showed that volumetric density of the SmallT was 20.4 W/m3 while LargeT units achieved only 7.0 W/m3 which suggests 2.9 times higher performance of small Microbial Fuel Cell (MFC)
Summary
Observing the continuously increasing demand for water and energy in the world, alternative sources are needed to meet the requirement of a growing population. The successful scale-up process should involve the optimization of materials and design which allow a cost and energy effective technology (Do et al, 2018), as well as more lab-based and field trial led research for development of this technology for large scale applications (Khan et al, 2017) With this approach in mind, recent advancements bring the technology closer to the real life implementation thanks to using ceramic for MFC architecture (Gajda et al, 2015a,c; Pasternak et al, 2016), open to air cathodes with non-platinum catalysts (Merino-Jimenez et al, 2016; Gajda et al, 2018) and improved design of multiple MFC units in the system (Ieropoulos et al, 2008). The changes in power density during scale-up result from changes in many important factors, such as reactor volume, electrode spacing and electrode specific surface area (surface area per volume; Cusick et al, 2011) which determine internal resistance of the system (Ieropoulos et al, 2008)
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