Bioelectricity production by using goat (Capra hircus) rumen fluid from slaughterhouse waste in mediator-less microbial fuel cells

Microbial fuel cells (MFCs) grasped an outlook for bioelectricity production under global scenario. Many studies have highlighted the utilization of various wastes for electricity generation by this advantageous technology. In the present investigation, an H-type, two-chambered MFC was designed for bioelectricity production using Capra hircus rumen fluid collected from slaughterhouse, paddy straw as substrate, copper as anode, and zinc as cathode. The power output of single MFC was recorded to a maximum of 5.76 W and 8.49 W/m². Effect of acetic acid as catholyte with concentration range (0.0–2.0%) was compared with air cathode. Acetic acid was found to enhance the power output at 2% concentration. Assessment for increased power output was carried out by connecting the four MFCs in series. MFC series performed well with a maximum power output of 67.24 W at 192 h with acetate as catholyte whereas 54.76 W for air cathode. The maximum power density achieved was 42.11 W/m² for acetate in cathode and 34.39 W/m² for air cathode. The MFCs developed with rumen consortia, hay as substrate, and Cu–Zn electrodes were found to be effective in bioelectricity production.     

Review of high-performance biocathode using stainless steel and carbon-based materials in Microbial Fuel Cell for electricity and water treatment

Biocathode application in Microbial Fuel Cell (MFC) is a promising alternative for sustainable energy production. This recognition is due to its low construction and operation costs as well as the utilization of microbial metabolism in assisting power generation. One of the most crucial factors contributes to the performance of a biocathode MFC is the characteristics and configuration of the biocathode material itself. Hence it requires improvement for a better understanding towards its bioelectrochemical mechanisms as well as improving the MFC performance. However, reports on improving biocathode through support material selection and performance optimization in MFCs are still lacking. Based on previous reports, studies have shown that carbon-based material and stainless steel are possible biocathode materials for high power MFC performance. This review focuses on comparing these potential biocathode materials, regarding the commonly applied biocathode MFC designs and optimization. This review also compares the performance of biocathode materials in MFC based on the bioelectricity production and wastewater treatment. Further studies and understanding can provide a useful basis in fabricating biocathode designs and configurations to produce better sustainable bioelectricity in MFCs.     

Cathode modification with peptide nanotubes (PNTs) incorporating redox mediators for azo dyes decolorization enhancement in microbial fuel cells

To enhance azo dye reduction in cathode of microbial fuel cells (MFCs) and power generation, a novel cathode modification method was developed on carbon paper (CP) through immobilization of redox mediators (RMs) with self-assembled peptide nanotubes (PNTs) as the carrier. Results showed that the optimum peptide concentration for PNT self-assembly on electrode and Orange II decolorization in MFCs was 2 mg mL^?1. The PNT/RMs/CP electrodes exhibited higher electrocatalytic activities than PNT or RM solely modified electrodes and raw carbon paper electrode. MFCs loaded with the riboflavin (RF)/PNT modified cathode (PNT/RF/CP) or anthraquinone-2, 6-disulfonate (AQDS)/PNT modified cathode (PNT/AQDS/CP) showed an enhanced decolorization rate to Orange II compared to that with the control electrode, with the reduction kinetic constants increased by 1.3 and 1.2 folds, respectively. Furthermore, the MFCs with the PNT/AQDS/CP cathode and PNT/RF/CP cathode generated a higher maximum power density of 55.5 mW m^?2 and 72.6 mW m^?2, respectively, compared to the control (15.5 mW m^?2). The PNT/RMs modification could reduce cathode total internal resistance and accelerate electron transfer from electrodes to dyes, which may result in the enhanced performance of MFCs.     

Enhanced sludge stabilization coupled with microbial fuel cells (MFCs)

This study presents research results on electricity production from waste activated sludge using MFCs during stabilization process. Different MFC configurations equipped with various electrodes were used. Voltage measurements were continuously done during 35 days of MFC operation. Experimental results showed that bioelectricity generation was linked to volatile solids (VS) and protein reductions as a fraction of extracellular polymeric substances (EPS). Double chamber MFC reactor equipped with graphite electrodes had better power and current densities as 312.98 mW/m² and 39.07 μA/cm² while single chamber MFC equipped with titanium electrodes revealed better power and current densities as 97.60 mW/m² and 17.63 μA/cm², respectively. Molecular results indicated that power outputs of MFCs effected by diverse microbial communities in anode biofilms. Although organic matter degradation is reported as 35%–55% VS reduction for digesters, this research provided a promising approach for sludge stabilization with enhanced degrading of organic matters up to 75% by using MFCs.     

Effect of recirculation on bioelectricity generation using microbial fuel cell with food waste leachate as substrate

Recirculation is one of the effective techniques used to upsurge the output of anaerobic reactors. The present study investigates the effect of recirculation of anolyte on bioelectricity generation using food waste leachate in two chamber Microbial Fuel Cell (MFC) with carbon electrodes and Ultrex as proton exchange membrane (PEM). The MFCs are operated in fed-batch mode at varying COD concentrations of 500–1250 mg/L with the hydraulic retention time of 17 h for recirculation. Maximum current density, power density and columbic efficiencies of 100.34 mA/m², 14.42 mW/m² and 10.25% respectively for MFC without recirculation and 150.30 mA/m², 29.23 mW/m² and 14.22% respectively for MFC provided with recirculation are obtained at COD of 1250 mg/L. Comparative performance analysis of the cells indicates that recirculation enhances the bioelectricity production in MFC. Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) analyses are also done to find the changes in PEM.     

Exoelectrogens in microbial fuel cells toward bioelectricity generation: a review

Exoelectrogens are catalytic microorganisms competent to shuttle electrons exogenously to the electrode surface without utilizing artificial mediators. Diverse microorganisms acting as exoelectrogens in the fluctuating ambience of microbial fuel cells (MFCs) propose unalike metabolic pathways and incompatible, specific proteins or genes for their inevitable performance toward bioelectricity generation. A pivotal mechanism known as quorum sensing allows bacterial population to communicate and regulates the expression of biofilm‐related genes. Moreover, it has been found that setting the anode potential affects the metabolism of the exoelectrogens and hence the output of MFCs. Microscopic, spectrometry investigations and gene deletion studies have confirmed the expression of certain genes for outer‐membrane multiheme cytochromes and conductive pili, and their potential roles in the exoelectrogenic activity. Further, cyclic voltammetry has suggested the role of multifarious redox‐active compounds secreted by the exoelectrogens in direct electron transport mechanisms. Besides, it also explores the various mechanisms of exoelectrogens with genetic and molecular approaches, such as biofilm formation, microbial metabolism, bioelectrogenesis, and electron transfer mechanisms from inside the exoelectrogens to the electrodes and vice versa. Copyright © 2015 John Wiley & Sons, Ltd.     

Analysis of chitin particle size on maximum power generation, power longevity, and Coulombic efficiency in solid-substrate microbial fuel cells

Microbial fuel cells (MFCs) produce bioelectricity from a wide variety of organic and inorganic substrates. Chitin can be used as a slowly degrading substrate in MFCs and thus as a long-term fuel to sustain power by these devices in remote locations. However, little is known about the effects of particle size on power density and length of the power cycle (longevity). We therefore examined power generation from chitin particles sieved to produce three average particle sizes (0.28, 0.46 and 0.78 mm). The longevity increased from 9 to 33 days with an increase in the particle diameter from 0.28 to 0.78 mm. Coulombic efficiency also increased with particle size from 18% to 56%. The maximum power density was lower for the largest (0.78 mm) particles (176 mW m⁻²), with higher power densities for the 0.28 mm (272 mW m⁻²) and 0.46 mm (252 mW m⁻²) particle sizes. The measured lifetimes of these particles scaled with particle diameter to the 1.3 power. Application of a fractal dissolution model indicates chitin particles had a three-dimensional fractal dimension between 2 and 2.3. These results demonstrate particles can be used as a sustainable fuel in MFCs, but that particle sizes will need to be controlled to achieve desired power levels.     

Recent advances in constructed wetland‐microbial fuel cells for simultaneous bioelectricity production and wastewater treatment: A review

The coupling of constructed wetlands (CWs) to microbial fuel cells (MFCs) has turned out to be a source of renewable energy for the production of bioelectricity and for the simultaneous wastewater treatment. Both technologies have an aerobic zone in the air‐water interface and an anaerobic zone in the lower part, where the anode and the cathode are strategically placed. This hybridization is a promising bioelectrochemical technology that exerts a symbiosis between plant‐bacteria in the rhizosphere of an aquatic plant, converting solar energy into bioelectricity through the formation of root exudates as an endogenous substrate and a microbial activity. The difference between CW‐MFC and MFC conventional lies in the bioelectricity and substrate production in situ, where exogenous substrates are not required for example wastewater. However, CW‐MFC can take organic content present in wastewater, promoting the removal of some pollutants. Different areas that comprise the study of a CW‐MFC have been explored, including the structures and their operation. This review aims to provide concise information on the state of the art of CW‐MFC systems, where a summary on important aspects of the development of this technology, such as bioelectricity production, configurations, plant species, rhizodeposits, electrode materials, wastewater treatment, and future perspectives, is presented. This system is a promising technology, not only for the production of bioenergy but also to maintain a clean environment, since during its operation, no toxic byproducts were formed.     

Study on synergistic mechanism of PANDAN modification,current and electroactive biofilms on Congo red decolorization in microbial fuel cells

Effect on microbial fuel cells (MFCs) for decolorization of Congo red by Poly (aniline-1,8-diaminonaphthalene) (PANDAN) modification, current and electroactive biofilms (EABs) is investigated. With the synergism of the three factors: PANDAN modification, current and EABs (A2 reactor), the COD removal and decolorization rate significantly increase to 88% and 97%, as well as the Congo red is thoroughly degraded. The decolorization performance comparison and Redundancy analysis (RDA) results indicate that the EABs take more responsibility (contribute ~ 50%) for the decolorization, rather than the modification and current. Therefore, the effects and mechanism of PANDAN modification and current on EABs are further revealed by the Confocal Scanning Laser Microscopy (CSLM) and high-throughput sequencing analysis. The effects of current (anodic dynamical microenvironment), material adsorption, and electron transfer mediating act comprehensively on the thickness, viability, EPS and microbial community of the EABs, among which the relationship is discussed in depth by hierarchically comparison, with “independent and additional effects”. It is demonstrated that the modification, current and EABs present the synergistic effect and promote each other in the performance of the decolorization MFC.     

Ultrasonic pretreatment of palm oil mill effluent: Impact on biohydrogen production,bioelectricity generation,and underlying microbial communities

Substrate bioavailabity is one of the critical factors that determine the relative biohydrogen (bioH₂) yield in fermentative hydrogen production and bioelectricity output in a microbial fuel cell (MFC). In the present undertaking, batch bioH₂ production and MFC-based biolectricity generation from ultrasonically pretreated palm oil mill effluent (POME) were investigated using heat-pretreated anaerobic sludge as seed inoculum. Maximum bioH₂ production (0.7 mmol H₂/g COD) and COD removal (65%) was achieved at pH 7, for POME which was ultrasonically pretreated at a dose of 195 J/mL. Maximum value for bioH₂ productivity and COD removal at this sonication dose was higher by 38% and 20%, respectively, than unsonicated treatments. In batch MFC experiments, the same ultrasound dose led to reduced lag-time in bioelectricity generation with concomitant 25% increase in bioelectricity output (18.3 W/m³) and an increase of COD removal from 30% to 54%, as compared to controls. Quantitative polymerase chain reaction (qPCR) tests on sludge samples from batch bioH₂ production reflected an abundance of gene fragments coding for both clostridial and thermoanaerobacterial [FeFe]-hydrogenase. Fluorescence in situ hybridization (FISH) tests on sludge from MFC experiments showed Clostridium spp. and Thermoanaerobacterium spp. as the dominant microflora. Results suggest the potential of ultrasonicated POME as sustainable feedstock for dark fermentation-based bioH₂ production and MFC-based bioelectricity generation.     

Three-dimensional graphitic mesoporous carbon-doped carbon felt bioanodes enables high electric current production in microbial fuel cells

Microbial fuel cells (MFCs) represent a new approach that can simultaneously enhance the treatment of waste streams and generate electricity. Although MFCs represent a promising technology for renewable energy production, they have not been successfully scaled-up mainly due to the relatively-low electricity generation and high cost associated with MFCs operation. Here, we investigated whether graphitic mesoporous carbon (GMC) decoration of carbon felt would improve the conductivity and biocompatibility of carbon felt anodes, leading to higher biomass attachment and electricity generation in MFCs fed with an organic substrate. To test this hypothesis, we applied 3 different GMC loading (i.e., 2, 5, and 10 mg/cm² of anode surface area) in MFCs compared to control MFCs (with pristine carbon felt electrodes). We observed that the internal resistances of modified anodes with GMC were 1.2–2.3-order of magnitude less than pristine carbon felt anode, leading to maximum power densities of 70.3, 33.3, and 9.8 mW/m² for 10, 5, and 2 mg/cm²-doped anode, respectively compared to only 3.8 mW/m² for the untreated carbon felt. High-throughput sequencing revealed that increasing the GMC loading rate was associated with enriching more robust anode-respiring bacteria (ARB) biofilm community. These results demonstrate that 3-D GMC-doped carbon felt anodes could be a potential alternative to other expensive metal-based electrodes for achieving high electric current densities in MFCs fed with organic substrates, such as wastewater. Most importantly, high electron transfer capability, strong chemical stability, low cost, and excellent mechanical strength of 3-D GMC-doped carbon felt open up new opportunities for scaling-up of MFCs using cheap and high-performance anodes.     

A novel method for determination of a time period for stabilization of power generation of microbial fuel cell with effect of microorganisms

Microbial fuel cells (MFCs) are quickly gaining traction in the mainstream industry due to their capabilities in simultaneous power generation and wastewater purification. They use bacteria like Shewanella and Geobacter as primary units for the same. However, their power generation capabilities are limited by a lack of stability in certain configurations. For the development of appropriate power storage and management systems, this instability must be investigated. Therefore, the present study proposes the artificial intelligence (AI) methodology of artificial neural search (ANS) networks to predict the period for stabilization of power generation of microbial fuel cell in the presence of microorganisms. An output voltage has been measured as a function of time (approximately 1600 h). A stabilization period of power generation has been predicted from the slope obtained from the graph of voltage vs time. The analysis of the ANS model indicated that the power generation stabilization has occurred between 12th and 16th weeks. Experiments were then performed to validate the findings from the ANS model. This may serve as an indication for the development of energy management and storage systems that can account for the trends observed during this study     

Effect of hydrogen producing mixed culture on performance of microbial fuel cells

This study examined the influence of H₂-producing mixed cultures on improving power generation using air-cathode microbial fuel cells (MFCs) inoculated with heat-treated anaerobic sludge. The MFCs installed with graphite brush anode generated higher power than the MFCs with carbon cloth anode, regardless heat treatment of anaerobic sludge. When the graphite brush anode-MFCs were inoculated selectively with H₂-producing bacteria by heat treatment, power production was not improved (about 490 mW/m²) in batch mode operation, but for slightly increased in carbon cloth anode-MFCs (from 0.16 to 2.0 mW/m²). Although H⁺/H₂ produced from H₂-producing bacteria can contribute to the performance of MFCs, suspended biomass did not affect the power density or potential, but the Coulombic efficiency (CE) increased. A batch test shows that propionate and acetate were used effectively for electricity generation, whereas butyrate made a minor contribution. H₂-producing mixed cultures do not affect the improvement in power generation and seed sludge, regardless of the pretreatment, can be used directly for the MFC performance.     

Insights on the resistance,capacitance and bioelectricity generation of microbial fuel cells by electrochemical impedance studies

Electrochemical Impedance Spectroscopy is employed to understand the role of anodic capacitance and individual component resistance in the bioelectricity generation of microbial fuel cells.The anodic capacitance during initial bacterial growth and biofilm formation (1–9 days) is 6 times higher than the literature data.The power density calculated on day 24 being 0.497 W/m² which is approximately 3 times higher than the literature data.The maximum columbic efficiency obtained is 30.8% which is 2.8 times higher than literature. These results demonstrate that the mixed culture bacteria is more efficient in bioelectricity generation in microbial fuel cells and the anodic capacitance due to biofilm growth on anode plays an important role in the power generation of microbial fuel cells. The electrode resistance dominates over solution resistance due to Hydrogen Evolution and Oxygen Reduction Reactions.     

FeCo alloys in-situ formed in Co/Co2P/N-doped carbon as a durable catalyst for boosting bio-electrons-driven oxygen reduction in microbial fuel cells

Non-noble metal catalyst with high catalytic activity and stability towards oxygen reduction reaction (ORR) is critical for durable bioelectricity generation in air-cathode microbial fuel cells (MFCs). Herein, nitrogen-doped (iron-cobalt alloy)/cobalt/cobalt phosphide/partly-graphitized carbon ((FeCo)/Co/Co₂P/NPGC) catalysts are prepared by using cornstalks via a facile method. Carbonization temperature exerts a great effect on catalyst structure and ORR activity. FeCo alloys are in-situ formed in the catalysts above 900 °C, which are considered as the highly-active component in catalyzing ORR. AC-MFC with FeCo/Co/Co₂P/NPGC (950 °C) cathode shows the highest power density of 997.74 ± 5 mW m^?2, which only declines 8.65% after 90 d operation. The highest Coulombic efficiency (23.3%) and the lowest charge transfer resistance (22.89 Ω) are obtained by FeCo/Co/Co₂P/NPGC (950 °C) cathode, indicating that it has a high bio-electrons recycling rate. Highly porous structure (539.50 m² g^?1) can provide the interconnected channels to facilitate the transport of O₂. FeCo alloys promote charge transfer and catalytic decomposition of H₂O₂ to ?OH and ?O₂^?, which inhibits cathodic biofilm growth to improve ORR durability. Synergies between metallic components (FeCo/Co/Co₂P) and N-doped carbon energetically improve the ORR catalytic activity of (FeCo)/Co/Co₂P/NPGC catalysts, which have the potential to be widely used as catalysts in MFCs.     

Effects of furan derivatives and phenolic compounds on electricity generation in microbial fuel cells

Lignocellulosic biomass is an attractive fuel source for MFCs due to its renewable nature and ready availability. Furan derivatives and phenolic compounds could be potentially formed during the pre-treatment process of lignocellulosic biomass. In this study, voltage generation from these compounds and the effects of these compounds on voltage generation from glucose in air-cathode microbial fuel cells (MFCs) were examined. Except for 5-hydroxymethyl furfural (5-HMF), all the other compounds tested were unable to be utilized directly for electricity production in MFCs in the absence of other electron donors. One furan derivate, 5-HMF and two phenolic compounds, trans-cinnamic acid and 3,5-dimethoxy-4-hydroxy-cinnamic acid did not affect electricity generation from glucose at a concentration up to 10 mM. Four phenolic compounds, including syringaldeyhde, vanillin, trans-4-hydroxy-3-methoxy, and 4-hydroxy cinnamic acids inhibited electricity generation at concentrations above 5 mM. Other compounds, including 2-furaldehyde, benzyl alcohol and acetophenone, inhibited the electricity generation even at concentrations less than 0.2 mM. This study suggests that effective electricity generation from the hydrolysates of lignocellulosic biomass in MFCs may require the employment of the hydrolysis methods with low furan derivatives and phenolic compounds production, or the removal of some strong inhibitors prior to the MFC operation, or the improvement of bacterial tolerance against these compounds through the enrichment of new bacterial cultures or genetic modification of the bacterial strains.     

Identification of removal principles and involved bacteria in microbial fuel cells for sulfide removal and electricity generation

Simultaneous sulfide and organics removals with electricity generation can be achieved in microbial fuel cells (MFCs). In present research, principles of sulfide removal as well as the involved bacteria in the MFCs with sulfide and glucose as the complex substrate are investigated. Results indicated that electrochemical and biological oxidations are the main effects for sulfide removal. Community analysis shows a great diversity of bacteria on the anode surface, including the exoelectrogenic bacteria and sulfur-related bacteria. They are present in greater abundance than those in the MFCs fed with only sulfide and responsible for the effective electricity generation and sulfide oxidation in our proposed MFCs. The results are conducive to reveal the interactions between the pollutants and microbes in aspects of pollutants removals and energy recovery in the MFCs for sulfide removal.     

Power recovery with multi-anode/cathode microbial fuel cells suitable for future large-scale applications

Multi-anode/cathode microbial fuel cells (MFCs) incorporate multiple MFCs into a single unit, which maintain high power generation at a low cost and small space occupation for the scale-up MFC systems. The power production of multi-anode/cathode MFCs was similar to the total power production of multiple single-anode/cathode MFCs. The power density of a 4-anode/cathode MFC was 1184 mW/m³, which was 3.2 times as that of a single-anode/cathode MFC (350 mW/m³). The effect of chemical oxygen demand (COD) was studied as the preliminary factor affecting the MFC performance. The power density of MFCs increased with COD concentrations. Multi-anode/cathode MFCs exhibited higher power generation efficiencies than single-anode/cathode MFCs at high CODs. The power output of the 4-anode/cathode MFCs kept increasing from 200 mW/m³ to 1200 mW/m³ as COD increased from 500 mg/L to 3000 mg/L, while the single-anode/cathode MFC showed no increase in the power output at CODs above 1000 mg/L. In addition, the internal resistance (R_in) exhibited strong dependence on COD and electrode distance. The R_in decreased at high CODs and short electrode distances. The tests indicated that the multi-anode/cathode configuration efficiently enhanced the power generation.     

A novel microbial fuel cell stack for continuous production of clean energy

Production of sustainable and clean energy through oxidation of biodegradable materials was carried out in a novel stack of microbial fuel cells (MFCs). Saccharomyces cerevisiae as an active biocatalyst was used for power generation. The novel stack of MFCs consist of four units was fabricated and operated in continuous mode. Pure glucose as substrate was used with concentration of 30 g l⁻¹ along with 200 μmol l⁻¹ of natural red (NR) as a mediator in the anode and 400 μmol l⁻¹ of potassium permanganate as oxidizing agent in the cathode. Polarimetry technique was employed to analyze the single cell as well as stack electrical performance. Performance of the MFCs stack was evaluated with respect to amount of electricity generation. Maximum current and power generation in the stack of MFC were 6447 mA.m⁻² and 2003 mW.m⁻², respectively. Columbic efficiency of 22 percent was achieved at parallel connection. At the end of process, image of the outer surface of graphite electrode was taken by Atomic Force Microscope at magnification of 5000. The high electrical performance of MFCs was attributed to the uniform growth of microorganism on the graphite surface which was confirmed by the obtained images.     

Research progress in the application of metal organic frameworks and its complex in microbial fuel cells: Present status,opportunities, future directions and prospects

Metal organic frameworks (MOFs) could greatly improve the power generation and degradation performance of microbial fuel cells (MFCs). MOFs and their compound derivatives played key role in cathode, anode and proton exchange membrane of MFCs, which greatly promoted the power generation of MFC and the degradation efficiency of various pollutants. However, MOFs were still possessed some defects, such as complex synthesis process, difficult regulation, instability, etc. Moreover, the application of MFC was limited in low power density, system internal resistance, microbial consumption, etc. Which further limited the degradation of pollutants by MFC. The existing problems and various improvement schemes of MOFs for MFCs were further summarized, which would provide references for promoting the application of MOFs materials in MFC system. It was expected to enhance the application of MOFs materials and promote the performance of MFC.