Abstract
In order to improve the potential of Microbial Fuel Cells (MFCs) as an applicable technology, the main challenge is to engineer practical systems for bioenergy production at larger scales and to test how the prototypes withstand the challenges occurring during the prolonged operation under constant feeding regime with real waste stream. This work presents the performance assessment of low-cost ceramic MFCs in the individual, stacked (modular) and modular cascade (3 modules) configurations during long term operation up to 19 months, utilising neat human urine as feedstock. During 1 year, the performance of the individual MFC units reached up to 1.56 mW (22.3 W/m3), exhibiting only 20% power loss on day 350 which was significantly smaller in comparison to conventional proton or cation exchange membranes. The stack module comprising 22 MFCs reached up to 21.4 mW (11.9 W/m3) showing power recovery to the initial output levels after 580 days, whereas the 3-module cascade reached up to 75 mW (13.9 W/m3) of power, showing 20% power loss on day 446. In terms of chemical oxygen demand (COD) removal, the 3-module cascade configuration achieved a cumulative reduction of >92%, which is higher than that observed in the single module (56%).
Highlights
Microbial Fuel Cells (MFCs) utilise organic feedstocks as a fuel for direct electricity production by employing anode respiring microbes that convert organic matter into electrons while treating waste
Different approaches can be employed for optimising MFC technology to allow their scale-up for practical applications and one being miniaturisation and multiplication of small-scale units [22] as it has been shown that higher energy density levels and optimum biofilm/electrode surface area–to–volume ratios reside within smaller scale MFCs
On day 60, the power diminished due to feedstock depletion, after which the inlet tank was replenished with urine and the performance recovered to previous level, which is in agreement with previous work conducted in a continuous flow using human urine, reporting no power variance during 3 months of operating time [37]
Summary
Microbial Fuel Cells (MFCs) utilise organic feedstocks (wastewater, urine) as a fuel for direct electricity production by employing anode respiring microbes that convert organic matter into electrons while treating waste. In terms of effective applicability of MFC systems and the reduction of production costs, there is still much room for improvement in the reactor design and scalability process [23]. Many operational and design parameters, that might affect the power output by MFCs, can only be effectively tested in large-scale systems. Real-world implementation of MFCs requires that high power generation and treatment efficiency can be obtained with large-scale reactors, operated under realistic conditions [28,30].
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