The Influence of External Load on the Performance of Microbial Fuel Cells

Abstract

In this work, the effect of the external load on the current and power generation, as well as on the pollutant removal by microbial fuel cells (MFCs), has been studied by step-wise modifying the external load. The load changes included a direct scan, in which the external resistance was increased from 120 Ω to 3300 Ω, and a subsequent reverse scan, in which the external resistance was decreased back to 120 Ω. The reduction in the current, experienced when increasing the external resistance, was maintained even in the reverse scan when the external resistance was step-wise decreased. Regarding the power exerted, when the external resistance was increased below the value of the internal resistance, an enhancement in the power exerted was observed. However, when operating near the value of the internal resistance, a stable power exerted of about 1.6 µW was reached. These current and power responses can be explained by the change in population distribution, which shifts to a more fermentative than electrogenic culture, as was confirmed by the population analyses. Regarding the pollutant removal, the effluent chemical oxygen demand (COD) decreased when the external resistance increased up to the internal resistance value. However, the effluent COD increased when the external resistance was higher than the internal resistance. This behavior was maintained in the reverse scan, which confirmed the modification in the microbial population of the MFC.

Increase in Electrical Parameters Using Sucrose in Tomato Waste

“…The R int values found were 0.34116 ± 0.2914, 0.301241 ± 0.01754, 0.26841 ± 0.012134, and 0.148541 ± 0.012361 KΩ for the MFCs with 0, 5, 10, and 20% sucrose, as shown in Figure 5. The values of the internal resistances of the MFCs decreased with an increasing sucrose concentration, and according to Potrykus et al (2021), the internal resistance of the MFCs is dependent on the decomposition of the substrates used for power generation because the electrons that are released in the oxidation process in the anode chamber flow more freely throughout the system when the internal resistance is low, which also influences the anodic biofilm formation of the MFCs [44,45]. Figure 6 shows the bioelectricity generation process of the microbial fuel cells connected in a series, which managed to generate a voltage of 3.43 V, enough to light a green LED bulb.…”

“…It has been shown that the high content of phenols releases large amounts of electrons, which travel through the external circuit to the cathodic electrode, thus generating a higher electrical current output [42,43]. Ferreira-Santos et al (2020) used extruded pine phenolic extracts to check bioactivity in different applications due to the compounds they contain (Quercetin, Procyanidin A2, Procyanidin B1, and Procyanidin B2) in a large percentage of carbon, which is the main food source for microorganisms [44]. Figure 5 shows the values of the internal resistance of the microbial fuel cells at different percentages of sucrose (0, 5, 10, and 20%); the experimental data was adjusted to the formula V=RI of Ohm's law, where the x-axis represents the values of the electric current (I) and the y-axis represents the values of the voltage (V), for which the slope of the linear fit is the internal resistance (R int .)…”

Effect of Electrode Spacing on the Performance of a Membrane-Less Microbial Fuel Cell with Magnetite as an Additive

“…Unfortunately, the generation of energy from several sources of renewable energy completely relies on environmental conditions, making these sources almost inappropriate for addressing peak demands. Consequently, continuous energy provision cannot be made certain only by these sources, and new renewable energy techniques are needed [ 6 , 7 , 8 ].…”

“…Instead, power generation can be enhanced by optimizing process variables as opposed to scaling up. The power output of an MFC could be enhanced by optimizing process variables, for example, temperature, flow rate, pH, COD, or configuration options, for instance, electrode spacing [ 6 ]. Electrode spacing is perhaps one of the most important variables of a BES.…”

Enhancement of Power Generation and Organic Removal in Double Anode Chamber Designed Dual-Chamber Microbial Fuel Cell (DAC-DCMFC)

“…This technology could be considered for developing in the future in adopting back-to-nature concepts that use natural organic substrates [9,10], such as wastewater-based biomass, enriching carbons, and nutrients utilized by the electrogenic bacteria [11,12]. The research of MFC is still lacking in power generation affected by high internal resistance [13,14] and affected by parameters' control (pH, and temperature) [15], anolyte [16], catholyte [17][18][19][20], inoculum [21,22], anode [23,24], cathode [25,26], electrode spacing [27,28], separator [29,30], flowrate [31,32], retention time [33], wiring system [34], design/construction [35], and configuration [36][37][38]. Design and configuration modifications are studied since the highest internal resistance mostly occurs on the anode chamber.…”