Agric & Bioresources Engineering

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Agric & Bioresources Engineering

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Start date: 2020Subject: search.filters.subject.microbial fuel cell

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    Comparative study of BQ2557 and LTC3108 as efficient ultra-low bioelectricity harvesters from soil microbes using microbial fuel cells.
    (IEC, 2023-03-23) Simeon, Meshack Imologie; Mohammed, A. S; Freitag, R.
    Microbial fuel cells (MFCs) are attractive bio-electrochemical transducers that can convert waste and organic substrates into usable energy through the metabolic activity of electroactive microbes. However, the power generated by MFCs is relatively low compared to other types of fuel cells. This poses a serious problem for the practical application of MFCs. Commercially available voltage boosters are not suitable for use with MFCs due to the low current capacity of the MFCs. Therefore, special amplifiers are needed to boost the power of MFCs. In this study, two ultra-low harvesters (BQ25570 and LTC 3108) were configured and tested for their efficiency in extracting usable energy from soil MFCs. The result showed that the BQ could harvest bioelectricity from three MFCs connected in series to charge a 0.22 F supercapacitor up to 3.5 volts, which in turn was used to power a light-emitting diode (LED). The LTC, on the other hand, boosted the voltage of a single MFC from 0.72 V to 3.3 V. The increased voltage was used directly to supply a white LED operating at a constant voltage of 2.5 V. The voltage at the LED remained constant even when the MFC voltage dropped to 20 mV. These results demonstrated the potential of soil microbes to generate free energy that can be harvested, amplified and used for practical applications. Compared to the BQ, the LTC performed better with the soil MFC, boosting the voltage of a single MFC unit to a usable level without the need for a battery or supercapacitor.
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    Comparative evaluation of the performance of a capacitive and a non-capacitive microbial fuel cell
    (IEEE, 2021-03-25) Simeon, Meshack Imologie; A. L. Imoize; Freitag, Ruth
    Electrode materials play a critical role in the performance of microbial fuel cells. This study investigates the contribution of capacitive bio-electrodes to sustainable power production in a single-chamber microbial fuel cell (MFC). The capacitive electrodes consisted of a stainless-steel wire mesh with an activated carbon layer, while the non-capacitive control electrodes were made of graphite felt with a wound current collector. The MFCs were constructed using a glass vessel with the anode completely buried in biologically active soil and the cathode placed above the soil to form a single-chamber configuration. The performance of the MFCs was investigated using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The results showed that the performance of the capacitive MFC was three times better than that of the non-capacitive MFC. While there was no significant difference in the Ohmic resistances of the MFCs, there was a significant difference in charge transfer resistance and capacitance of the MFCs. The capacitive MFC had a double layer capacitance of 8.282 µF in addition to the diffuse layer capacitance at the layer/metal interface of 2.012 F, while the non-capacitive MFC had a double layer capacitance of 5.034 µF with no diffuse layer capacitance. The results show that the capacitive characteristics of both cathode and anode improve the performance of a single-chamber MFC.
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    Optimization of soil microbial fuel cell: influence of feeding duration, electrode factors and diversity factor of uncontrolled mixed microbial communities
    (international Society for microbial Electrochemistry amd Technology-ISMET8, 2022-09-19) Simeon, Meshack Imologie; Freitag, Ruth
    The electrochemical performance of the microbial fuel cell (MFC) depends not only on the operational and design parameters, but also on biological factors (Gadkari et al., 2019). Therefore, optimization studies that incorporate the interactive effects of the main influencing factors and the contributions of the biological factor would improve the understanding of the improvement strategies needed to advance the application of MFCs in the real world. While single-factor experiments are simple and less expensive to conduct, the reproducibility of the results of such experiments cannot be established with a high degree of confidence, especially in a complex system such as MFC. In this study, the feeding duration (4, 6 and 8 days), electrode material (carbon felt (CF) and modified stainless steel mesh (SM)), and electrode spacing (2, 4 and 8 cm) were integrated into a single design to optimize the performance of Soil MFC for stable and useful bioelectricity. The binder component of the SM was further optimized with four polymeric binders (epoxy, PVA, PVDF, and PTFE) and a new method - pasting and reinforcement (Simeon et al., 2022). PCR amplification and sequencing of 16S rDNA fragments were performed on the genomic DNA extracted from the MFCs, and bioinformatics analysis was performed using the QIIME2 microbiome analysis package. The results showed that the SM with a surface modified by conductive carbon black and epoxy binder exhibited superior performance in all experimental phases and achieved a maximum power three times higher than the CF at an electrode spacing of 4 cm and a feeding duration of 8 days. PVDF produced the highest current under real-time external loading, while epoxy produced the highest and most sustained power of 487.15 + 9.5 mW/m2 under linear polarization. Bioinformatic analysis revealed a wide bacterial diversity, with the most abundant phyla belonging to Proteobacteria (30-35%), Acidobacteriota (10-13%), Actinobacteriota (4-14%), Chloroflexi (6-9 %), Bacteroidota (3-9%), firmicutes (3-6%). Complex diversity in composition and abundance was observed mainly between the anode and cathode and between sampling time points, but no statistically significant difference was observed between the two electrode materials. This study indicates that the electrode material has the greatest influence on the sustainability and extent of bioelectricity capacity of a soil microbial fuel cell. Therefore, an increased focus on improving the electrode material would be a step in the right direction to position SMFCs as viable energy systems that can compete with the other established bio-electrochemical systems