Microbial Fuel Cell Stack Research Articles

Utilization of water chestnut waste for biohydrogen production and enhanced power generation by stacked microbial fuel cell

A novel two-stage approach combining dark fermentation with microbial fuel cell (MFC) technology is proposed which enable biohydrogen production and bioelectricity generation from residual substrate energy. In the present study, batch fermentation of water chestnut waste using Enterobacter aerogenes (MTCC 2822) resulted in the production of biohydrogen. In the batch process, the highest production was 3.2 L/L. Further, single-parameter optimization and multi-parameter optimization were conducted via Response Surface Methodology (RSM) using the Central Composite Design (CCD) model. The maximum biohydrogen reached 3.44 g/L with 55% COD removal. The biohydrogen yield was 7.163 g H2/kg CODreduced with a maximum production rate of 712 mL/L/h. Further, the waste fermentation medium or spent media was used as a substrate in a Microbial Fuel Cell (MFC) to produce power using Pseudomonas aeruginosa PA1_NCHU as inoculum. MFCs were operated with various concentrations of phosphate buffer in the anolyte. As the output is limited in a single MFC, MFCs were operated in parallel stacks to increase power output. A maximum of 28% increase in the power density was observed in stacked MFCs. The energy recovered from the dark fermentation process was around 10.39% and a single MFC was around 10.67%. Hence, this study highlights the innovative use of agricultural waste and the effective combination of dark fermentation with stacked MFC, presenting a sustainable method of maximizing biohydrogen production and bioelectricity from spent media. By leveraging stacked MFC configuration, the potential of higher power output is demonstrated, underscoring the significance of this integrated system for energy recovery.

Craft Brewery Wastewater Treatment in a Scalable Microbial Fuel Cell Stack

Craft breweries release wastewater into the environment, posing serious environmental concerns. Microbial fuel cells (MFCs) are an attractive technology that has been used in industrial wastewater treatment. This study used a scalable system of nine MFCs (stacked) to treat 150 L of craft brewery wastewater (CBW). The CBW had 1831 ± 85 mg COD (chemical oxygen demand) L−1. The hydraulic retention time was 5 days, with a COD removal percentage of 93 ± 1.8%. The total internal resistance of the stack was 204.8 ± 5.2 Ω at 26 ± 2 °C without the use of a metal catalyst; the reduction of oxygen was the limiting process. Finally, the sequence of treatments applied with this proposed system demonstrated its self-sustainability, which could be a viable option for the real-life conditions of this kind of wastewater. Further research is needed.

LED algal microbial fuel cell stack balancing conception: Electronic voltage reversal blockage, light feed-starvation cycling, and aeration

Stacked algae microbial fuel cells (AMFC) combine the strategic use of light and microbial energy to generate usable electricity. It generates oxygen directly at the electrodes, providing CO2 cycling, algal biomass, and value-added biomolecules. In this work a 12 Liter LED-Algae-Microbial-Fuel-Cell-Stack with maximum power tracking was investigated for voltage balancing and reversal resolution, enabling up to 1200 mV stable stack voltage under closed circuit conditions. The experiment was run in a municipal wastewater treatment plant for 152 days. A new type of data control computer device was used to block voltage reversals and maintaining power with unit resistances between 42 and 99 Ohm. It also allowed the detection of previously unreported light starvation effects in 16 process variants with voltage drops ranging from 14 to 240 mV switching off lights. Algae generated an oxygen concentration of 1.9–3.7 mg/L during power generation. Extending all light-on conditions significantly reduced the voltage reversal frequency. All light-on in combination with assisted oxygenation using 0.25 L/min air bubbling per unit resolved voltage reversals and balanced the AMFC-Stack.The results obtained are relevant to the study of stacked bioelectric systems that use low substrate concentrations and yet aim to generate stable power and minimize voltage reversals.

Scale-up single chamber of microbial fuel cell using agitator and sponge biocarriers

ABSTRACT Despite the high efficiency of microbial fuel cells (MFCs), MFCs cannot be a suitable alternative for treatment plants because of insufficient power generation and tiny reactors. Additionally, the increased reactor size and MFC stack result in a reduction in production power and reverse voltage. In this study, a larger MFC with a volume of 1.5 L has been designed called LMFC. A conventional MFC, called SMFC, with a volume of 0.157 L, was constructed and compared with LMFC. Moreover, the designed LMFC can be integrated with other treatment systems and generate significant electricity. In order to evaluate MFC's ability to integrate with other treatment systems, the LMFC reactor was converted into MFC-MBBR by adding sponge biocarriers. A 9.5 percent increase in reactor volume resulted in a 60 percent increase in power density from 290 (SMFC) to 530 (LMFC). An agitator effect was also investigated for better mixing and circulating substrate, which positively affected the power density by about 18%. Compared with LMFCs, the reactor with biocarriers generated a 28% higher power density. The COD removal efficiency of SMFC, LMFC, and MFC-MBBR reactors after 24 h was 85, 66, and 83%, respectively. After 80 h of operation, the Coulombic efficiency of the SMFC, LMFC, and MFC-MBBR reactors was 20.9, 45.43, and 47.28%, respectively. The doubling of coulombic efficiency from SMFC to LMFC reactor shows the design's success. The reduction of COD removal efficiency in LMFC is the reason for integrating this reactor with other systems, which was compensated by adding biocarriers.

The future role of MFCs in biomass energy

Microbial fuel cells (MFC) are an emerging green technology which offers several comparative advantages over other technologies for utilizing biomass. It is a technology that treats (cleans) wet organic waste, converting chemical energy to electricity that is used for connected peripherals and target applications. The main advantage is the technology’s ability to utilise wet biomass in suspension or in solution (i.e., too wet to burn) and change the biomass directly into bioenergy in the form of electricity. All other technologies either combust the biomass directly (e.g., wood fuel) or change the biomass into refined fuels which are then combusted or fed to chemical fuel cells to generate heat or electricity. Excluding methane production from biomass, and fermentation leading to hydrogen production, all other biomass/biofuel technologies utilize dry plant matter, which mainly consists of cellulose or lignocellulose and they cannot directly utilize sludge or slurries of organic detritus material. The substrates used for MFCs are not traditionally made into organic fuels, as with other biomass technologies, but are used directly as fuel, recasting the “waste” suspensions and solutions, and promoting them into fuels themselves. To a stack of MFCs, a polluted river, landfill leachate or farmland run-off, can all be reassigned as fuel. This wet fuel is widespread around the planet, the amounts found and the energy contained within are significant, and the cost as a fuel is close to zero. This review gives a general overview of biomass energy along with extraction techniques and compares advantages and disadvantages of MFCs with other biomass technologies for producing electrical energy.

Grid-Connected Microbial Fuel Cell Modeling and Control in Distributed Generation

Water shortages and water pollution have seriously threatened the sustainable development of the community. The grid-connected microbial fuel cell is an effective way to control the cost of wastewater treatment plants. Moreover, it solves the problem of low efficiency and high energy consumption. In view of the characteristics of strong coupling, non-linearity, and internal load in the process of microbial fuel cell grid connection, it is necessary to design the grid-connected unit of power electronic device. Based on the establishment of the microbial fuel cell stack model, the stability control and the constant power control scheme were designed for the chopper and inverter, respectively. The simulation results showed that the control strategy with the combination of voltage stabilizer and constant power can make a grid-connected system of all phase voltage and frequency output. The three-phase voltage Uabc was steady at 7 h and the voltage amplitude was controlled at roughly 380 V, according to the output voltage waveform. The value was 50 Hz, which satisfies the criteria for grid connection.

Modeling and testing the steady-state and transient behaviors of stacked microbial fuel cells under different electrical connection patterns

Microbial fuel cells (MFCs) represent a key solution in the context of sustainable energy development from organic material. Their implementation for real applications is still limited because of economic issues and low power densities. Several efforts have been done both to improve the economic performances by selecting low-cost materials and to increase the power output by realizing stacked configurations.The development of more complex configurations increases the difficulty of predicting the behavior of these bioenergy systems and their performances. In this contest numerical models, supported by the experimental activities, are very useful tools for forecasting the main biological, electrochemical and mass transfer processes occurring within MFCs during their operation in different conditions.In this paper, an electrical transient model, devoted to perform the stacked MFCs voltages and currents on equivalent electric circuits has been developed. The model, that is the superposition of an exponential pattern over a linear trend, is able to define the transient time domain of the voltage and current solutions of a specific electric circuit, enabling the scalability of the estimation of the electrical variables in stacked MFCs systems. The model calibration has been carried out by means of the experimental activities on a single MFC reactor as well as on a stacked MFCs configuration connected in parallel/series.The experimental activities have been performed by using a test bench consisting of the Agilent Digit Multimeters and a Resistance Box. The experimental tests have allowed to assess: i) the steady-state and transient behaviors of a single MFC; ii) the steady-state and transient behaviors of the stacked MFCs configurations.Results have highlighted that the developed model has proved to be an interesting tool for predicting the transient behavior of output currents and voltages after a step perturbation demonstrating how the MFCs evolve towards stable conditions as the load varies.

Halobacterium salinarum NRC-1 Sustains Voltage Production in a Dual-Chambered Closed Microbial Fuel Cell.

Sustained bioenergy production from organisms that thrive in high salinity, low oxygen, and low nutrition levels is useful in monitoring hypersaline polluted environments. Microbial fuel cell (MFC) studies utilizing single species halophiles under salt concentrations higher than 1 M and as a closed microbial system are limited. The current study aimed to establish baseline voltage, current, and power density from a dual-chambered MFC utilizing the halophile Halobacterium salinarum NRC-1. MFC performance was determined with two different electrode sizes (5 cm2 and 10 cm2), under oscillating and nonoscillating conditions, as well as in a stacked series. A closed dual-chamber MFC system of 100 mL capacity was devised with Halobacterium media (4.3 M salt concentration) as both anolyte and catholyte, with H. salinarum NRC-1 being the anodic organism. The MFC measured electrical output over 7, 14, 28, and 42 days. MFC output increased with 5 cm2 sized electrodes under nonoscillating (p < 0.0001) relative to oscillating conditions. However, under oscillating conditions, doubling the electrode size increased MFC output significantly (p = 0.01). The stacked series MFC, with an electrode size of 10 cm2, produced the highest power density (1.2672 mW/m2) over 14 days under oscillation. Our results highlight the potentiality of H. salinarum as a viable anodic organism to produce sustained voltage in a closed-MFC system.

Microbial community diversity changes during voltage reversal repair in a 12-unit microbial fuel cell

Microbial fuel cell stacks (MFC-Stack) are often confronted with voltage reversals, likely due to an interplay between microbial community dynamics and insufficient electric circuit balancing. Herein, we provide new insight into voltage reversals by examining the microbiomes of twelve MFC units of a 12-liter Pilot-MFC-Stack during repair. Different biofilm repair methods (self-healing, electrostimulation, and re-acclimatization upon cross-inoculation) were used to evaluate the microbial community response. In addition, MFC-Stack simulation was performed based on Kirchhoff’s Second Law to predict values for source potentials and post-evaluate internal resistances. Analysis of the 16S rRNA amplicon sequencing data suggests that the biofilm repair methods could slowly heal damaged biofilms. Notably, severely voltage reversed MFC units had low electrogen relative abundances (18%) and positive anode potentials, while strong bioanodes and contained more than 50% electrogens and had negative anode potentials. Between-community analyses (beta diversity ordination and multinomial regression) of the voltage reversed MFC units revealed differences among biofilms in contrast to healthy/strong MFC units. Permutational multivariate analysis of variance (PERMANOVA) confirmed that reversed biofilms were, indeed, significantly (p < 0.05) different from stronger ones. Overall, these analyses demonstrated the utility of combining electrotechnical and microbial community analyses, especially beta diversity ordination and multinomial regression, to understand problematic MFC units and the potential success of a biofilm repair method. Finally, thicker biofilms were usually healthier and stronger, although thickness was no guarantee for proper structure and power function as all factors were interdependent. There was an evolutionary trend that strong anodes became stronger/healthier and others weaker. This spontaneous trend has to be considered to avoid irreversible voltage reversals and to repair electrogenic biofilms in an MFC-Stack.

Investigation of the optimum conditions for electricity generation by haloalkaliphilic archaeon Natrialba sp. GHMN55 using the Plackett–Burman design: single and stacked MFCs

The production of bioelectricity via the anaerobic oxidation of organic matter by microorganisms is recently receiving much interest and is considered one of the future alternative technologies. In this study, we aimed to produce electrical current by using facultative halophilic archaeon Natrialba sp. GHMN55 as a biocatalyst at the anode of a microbial fuel cell (MFC) to generate electrons from the anaerobic breakdown of organic matter to produce electrical current. Since the MFC’s performance can be affected by many factors, the Plackett–Burman experimental design was applied to optimize the interaction between these factors when tested together and to identify the most significant factors that influence bioelectricity generation. We found that the factors that significantly affected electrical current generation were casein, inoculum age, magnet-bounded electrodes, NaCl, resistor value, and inoculum size; however, the existence of a mediator and the pH showed negative effects on bioelectricity production, where the maximum value of the 200 mV voltage was achieved after 48 h. The optimum medium formulation obtained using this design led to a decrease in the time required to produce bioelectricity from 20 days (in the basal medium) to 2 days (in the optimized medium). Also, the overall behavior of the cell could be enhanced by using multiple stacked MFCs with different electrical configurations (such as series or parallel chambers) to obtain higher voltages or power densities than the single chambers where the series chambers were recorded at 27.5 mV after 48 h of incubation compared with 12.6 mV and 1.1 mV for parallel and single chambers, respectively. These results indicate that the order of preferred MFC designs regarding total power densities would be series > parallel > single.

Application and Characterization of Poly Vinyl Alcohol Membrane in Microbial Fuel Cell

Microbial Fuel Cells (MFCs) has been attracting significant attention as it not only treats waste water but also generates electricity from using waste water thereby producing electricity. The present paper presents the use of MFC in converting the waste water into electricity using a PVA membrane and graphite electrodes assembled in a lab made single MFC stack. The highest voltage obtained as 452 mV in open circuit condition which got stabilized after working for 8hrs of operation and the membrane lasted for more than 10 days of operation. The maximum current density produced was 1400mA/sqm and the ion exchange capacity was found to be 1.2meq/gm. FTIR, contact angle, TGA and SEM analysis of the membrane was also done.

Performance of stacked microbial fuel cells with barley–shochu waste

The treatment of barley-shochu waste combined with electricity generation was examined using stacked microbial fuel cells (SMFCs). The maximum chemical oxygen demand (CODCr) removal efficiency and maximum power density were achieved at 36.7 ± 1.1% and 4.3 ± 0.2Wm⁻³ (15.7 ± 0.9mWm-2). The acetic acid concentration in effluent increased, whereas the citric acid, ethanol and sugar concentrations decreased during the operation. Microbial community analysis of the anode cell suspension and raw barley-shochu waste revealed that Clostridiaceae, Acetobacteraceae, and Enterobacteriaceae became predominant after the operation, implying that microorganisms belonging to these families might be involved in organic waste decomposition and electricity generation in the SMFCs.

Optimization of catalyst dosage and total volume for extendible stacked microbial fuel cell reactors using spacer

Reactors stack may be one of the most viable methods for microbial fuel cells (MFCs) scaling up. Optimization of catalyst and total reactor volume is necessary for stacked MFCs. Optimization of active carbon dosage (10 mg/cm 2 ) or adding a small amount of Pt/C (1/10 of the common quantity) into active carbon can both improve reactor performances with relative low catalyst cost. One stacked unit set up with four cubic MFCs is built in this research, which spacers are used to minimize the distance of cathodes and two anodes share mutual chambers. The total volume of stacked unit is reduced by 23.8%, without adversely affecting performance, including start up, power density and columbic efficiency. Theoretically, more stacked units can be extended using similar stack structures in this study. • Dosage optimization is important for active carbon catalyst. • One stacked unit set up with four cubic microbial fuel cells. • Spacers minimize the cathodes distance and two anodes share mutual chamber. • Total volume is reduced by 23.8% without adversely affecting performance. • The stack structure can be further extended horizontally.

Removal of Coliphage MS2 Using a Microbial Fuel Cell Stack

Bioelectrochemical technologies offer alternative ways of treating wastewater and using this process to generate electricity. However, research in this area is just beginning to consider environmental transmission of viruses present in wastewater. The viral fecal indicator coliphage MS2 (the most frequently used pathogen model) was used in this study, since it is a well-known indigenous wastewater virus. The scaled-up bioelectrochemical system had a working volume of 167 L and coliphage MS2 concentration decreased from 8000 to 285 PFU/mL. The kinetics were quantified up to 15 h, after which excessive yeast growth in the system prevented further bacteriophage determination. The logarithmic reduction value (LRV) calculated within the first three hours was 3.8. From 4 hours to 14, LRV values were from 4.1 to 4.8, and in hour 15 the LRV increased to 5.3, yielding a more than 90% reduction. Overall, results obtained indicate that the scaled-up bioelectrochemical treatment system was efficient in reducing coliphage MS2 densities and could be used as a model to explore its further applicability for the reduction of viruses or pathogens in treated effluents.

Heat Treatment Effect on the Surface Properties of Carbon Cloth Electrode for Microbial Fuel Cell

In this study, we investigate the effect of heat treatment on the surface properties of carbon cloth electrodes and on the power generation efficiencies of microbial fuel cells (MFCs) configured with the heat-treated carbon cloth electrodes. Water contact angle measurements show that the hydrophobic surfaces of the carbon cloth became super-hydrophilic after heat treatment at a temperature above 500 °C, making it suitable for bacterial propagation. X-ray photoelectron spectrometry revealed that the signal of the C-O functional group of the carbon cloth electrodes increased in intensity after heat treatment. The MFCs configured with heat-treated carbon cloth electrode exhibited high power density of 16.58 mW/m2, whereas that of the untreated MFCs was only 8.86 mW m2. Compared with other chemical modifications, heat treatment does not use any environmentally unsound acidic or toxic solutions during modification and are promising for manufacturing large-scale MFC stacks.

Comparative study of different hydro-dynamic flow in microbial fuel cell stacks

• Different hydrodynamic configuration were investigated in MFC stacks. • Modified earthen membrane was utilized in the MFCs. • Parallel independent hydrodynamic connection showed the best power generation. This work has investigated the scale-up potential of microbial fuel cells (MFCs) under stacking mode. Stacking was done in batch mode and continuous mode. Batch feeding mode stacks were operated in electrical series (S) and parallel (P) mode. Continuous feeding mode stacks were kept in electrically parallel mode with different hydro-dynamic patterns. The two continuous stacks were connected hydro-dynamically in series ( i . e . Parallel Dependent; PD) and parallel ( i . e . Parallel Independent; PID) configurations. The performance of the continuous stacks was evaluated on the basis of COD consumption rate, power generation and coulombic efficiency. PID obtained highest power (0.47 mW) which was approximately 3.6 times that of PD configuration (0.13 mW). The rate of COD consumption was also highest in PID stack (3091.75 mg·L −1 ·d −1 ). Coulombic efficiency of the PID stack was 14.26% which was approximately 292.8% of the PD stack. The results confirmed that the parallel electrical connection hybridized with the independent hydro-dynamic flow gives the best possible results when working with stacking of MFCs.

Demonstration of energy and nutrient recovery from urine by field-scale microbial fuel cell system

Scaling-up of Microbial fuel cells (MFC) involves optimizing parameters like the number of units, electrodes and unit size. This study demonstrates the working of a 10 L scale MFC stack for nutrients recovery (struvite as slow phosphorous release fertilizer) and energy recovery from urine over a three-month analysis period. The MFCs employed, a part of three staged systems (pH development, precipitation and treatment), were membrane divided double-chambered, operating in multiple-fed batch mode with a hydraulic retention time of 48 h. The average removal of chemical oxygen demand (COD) achieved was 75.55 ± 2.8 %, with removal rates of 4.252 kg/m3 day. The recovery of Ortho-Phosphates and ammoniacal nitrogen as struvite was 90 ± 1.5 % and 46 ± 2.16 %. The stacked MFC showed an average open-circuit voltage of 3.29 ± 0.68 V with power density of 14.5 mW/m2. Our findings suggest that the proposed three-stage process employing MFC stack achieved acceptable performance concerning nutrient recovery and organics removal.

Scale Up of a Marine Sediment Microbial Fuel Cells Stack with a Floating Aerated Cathode Using a Circuit Storage Energy from Ultra-Low Power

In this study, it was proposed to design, build, analyze and evaluate a stack of 9 Sediment Microbial Fuel Cells (SMFC) with a depth in the sediment of 10 cm and separation between anode and cathode of 100 cm, using floating cathodes aerated with saturated oxygen, sediments and seawater were collected from the Campeche bay (Mexico). Maximum power density and current density were 101.28 mW/m2 and 899.51 mA/m2 respectively, and organic matter removal was 9.25%, obtaining aromatic structures. Using a circuit storage energy from ultra-low power. Our findings revealed that the implementations of SMFC stack proposal could be a candidate for real scale.

Effect of sediment microbial fuel cell stacks on 9 V/12 V DC power supply

Sediment microbial fuel cell (SMFC) is a bio-electrochemical device that uses anaerobic bacteria to produce renewable energy. The voltage generated by SMFC is very low, so directly it cannot be applied to modern electronic devices. But, it is feasible to raise the output voltage of SMFC by connecting them in series-parallel combinations. In the present work, four SMFC modules are developed in the laboratory and by connecting in four different ways the output voltage as well as the output current are raised to the utility levels. The primary cause to avoid the practical application of series and parallel connected SMFC is voltage reversal problem. To do away with this problem, in this work each group of SMFCs is first used to charge a super-capacitor (4 F, 5.5 V) and then it has been used to power the dc boost converter. Moreover, in this research work, the effects of charging and discharging times of super capacitors for each module are also investigated. In the final stage, a dc boost converter is presented to step-up the voltage of stacked SMFCs which provides a regulated output voltage (9 V/12 V) at the load. The results obtained, show that module-4 connected boost converter provides higher output current for a longer duration as compared to other super capacitor connected modules. This technique of energy harvesting from SMFCs can be used as a power source (either of 9 V or 12 V) in practical electronic devices.

From the lab to the field: Self-stratifying microbial fuel cells stacks directly powering lights

The microbial fuel cell (MFC) technology relies on energy storage and harvesting circuitry to deliver stable power outputs. This increases costs, and for wider deployment into society, these should be kept minimal. The present study reports how a MFC system was developed to continuously power public toilet lighting, with for the first time no energy storage nor harvesting circuitry. Two different stacks, one consisting of 15 and the other 18 membrane-less MFC modules, were operated for 6 days and fuelled by the urine of festival goers at the 2019 Glastonbury Music Festival. The 15-module stack was directly connected to 2 spotlights each comprising 6 LEDs. The 18-module stack was connected to 2 identical LED spotlights but going through 2 LED electronic controller/drivers. Twenty hours after inoculation the stacks were able to directly power the bespoke lighting system. The electrical energy produced by the 15-module stack evolved with usage from ≈280 mW (≈2.650 V at ≈105 mA) at the beginning to ≈860 mW (≈2.750 V at ≈300 mA) by the end of the festival. The electrical energy produced by the LED-driven 18-module stack increased from ≈490 mW at the beginning to ≈680 mW toward the end of the festival. During this period, illumination was above the legal standards for outdoor public areas, with the 15-module stack reaching a maximum of ≈89 Lx at 220 cm. These results demonstrate for the first time that the MFC technology can be deployed as a direct energy source in decentralised area (e.g. refugee camps).