Microbial Fuel Cell Stack Research Articles

Microbial Fuel Cell stack performance enhancement through carbon veil anode modification with activated carbon powder

The chemical energy contained in urine can be efficiently extracted into direct electricity by Microbial Fuel Cell stacks to reach usable power levels for practical implementation and a decentralised power source in remote locations. Herein, a novel type of the anode electrode was developed using powdered activated carbon (PAC) applied onto the carbon fibre scaffold in the ceramic MFC stack to achieve superior electrochemical performance during 500 days of operation. The stack equipped with modified anodes (MF-CV) produced up to 37.9 mW (21.1 W m−3) in comparison to the control (CV) that reached 21.4 mW (11.9 W m−3) showing 77% increase in power production. The novel combination of highly porous activated carbon particles applied onto the conductive network of carbon fibres promoted simultaneously electrocatalytic activity and increased surface area, resulting in excellent power output from the MFC stack as well as higher treatment rate. Considering the low cost and simplicity of the material preparation, as well as the outstanding electrochemical activity during long term operation, the resulting modification provides a promising anode electrocatalyst for high-performance MFC stacks to enhance urine and waste treatment for the purpose of future scale-up and technology implementation as an applied off-grid energy source.

Multiple anodic chambers sharing an algal raceway pond to establish a photosynthetic microbial fuel cell stack: Voltage boosting accompany wastewater treatment

Photosynthetic microbial fuel cells (PMFCs) allow renewable energy production from wastewater. However, system scale-up is still a major challenge hindering the use of PMFCs for practical applications. Herein, a PMFC stack, which consisted of multiple anodic chambers installed in an algal raceway pond (ARP), was established to recovery energy from anaerobically digested effluent with the assistance of a prototypical capacitor circuit. The highest voltage output of the stack reached 1.4 V with four PMFC units and four capacitors. The system can produce stable voltages through controlling charging and discharging frequencies and the voltage output remained stable around 0.60 V when the time interval decreased to 2 s. During long-term operation, the highest power density of the stack with capacitors reached 2.34 W/m3, which was 77% higher than that without capacitors (1.32 W/m3). About 98% of the ammonium in the anolyte was removed, resulting from the ammonium migration effect. The dynamics of bacterial community compositions were not greatly influenced by the capacitor circuit, and the stack with capacitors had a more stable bacterial community compared to the stack without capacitors. The variations in bacterial community composition following power density changes indicated that members of the Clostridia and Betaproteobacteria were related to power generation. Bacteria affiliated to Bacteroidetes were inhibited when power density was high, though their numbers were enriched at the end of the process. This study promotes a practical method for developing the PMFC technology into real-world applications, and furthermore reveals the main bacteria that play vital roles in power generation by analysing the anodic bacterial community during the whole process.

Effects of unit distance and number on sediment microbial fuel cell stacks for practical power supply

Effects of unit distance and number on sediment microbial fuel cell stacks for practical power supply

Shipboard bilge water treatment by electrocoagulation powered by microbial fuel cells

Ships generate large amounts of wastewater including oily bilge water, blackwater and greywater. Traditionally they are treated separately with high energy consumption. In this study we demonstrate the feasibility that these waste streams can be treated using an integrated electrocoagulation cell (ECC) and microbial fuel cell (MFC) process, which not only synergized the contaminants removal but also accomplished energy neutrality by directly powering EC with MFC electricity. Results showed that MFC stack powered ECC removed 93% of oily organics, which is comparable to the performance of an external DC voltage powered ECC. In the meantime, more than 80% of COD was removed from MFCs when fed with either acetate or municipal wastewater. Moreover, the ECC electrode area and distance showed notable effects on current generation and contaminants removal, and further studies should focus on operation optimization to enhance treatment efficiency.

Operation and Electro(chemical) characterization of a microbial fuel cell stack fed with fermentable household waste extract

<p>Two identical four air-cathode single chamber membrane-less microbial fuel cells were stacked and tested under in series and in parallel electrical configurations. Fermentable household waste extract (FORBI; 0.8 g COD/L) was used as substrate, in all cases. Linear Sweep Voltammetry (LSV) was carried out for the construction of polarization curves which revealed that the highest power ouput (3.88 mW) was obtained under parallel connection as in series connection was found lower due to voltage drop phenomena. Electrochemical Impedance Spectroscopy measurements (EIS) gave an insight in the electrochemical processes occurring within the stack under both electrical connections. The contribution of the individual resistances to the overall internal resistance was defined, designating the significant role of the solution resistance (Rs) and the charge transfer resistance (RCT) under closed circuit conditions.</p>

Scale up of Microbial Fuel Cell Stack System for Residential Wastewater Treatment in Continuous Mode Operation

The most important operational expense during wastewater treatment is electricity for pumping and aeration. Therefore, this work evaluated operational parameters and contaminant removal efficiency of a microbial fuel cell stack system (MFCSS) that uses no electricity. This system consists of (i) septic tank primary treatment, (ii) chamber for secondary treatment containing 18 MFCs, coupled to an energy-harvesting circuit (EHC) that stores the electrons produced by anaerobic respiration, and (iii) gravity-driven disinfection (sodium hypochlorite 5%). The MFCSS operated during 60 days (after stabilization period) and it was gravity-fed with real domestic wastewater from a house (5 inhabitants). The flow rate was 600 ± 100 L∙d−1. The chemical oxygen demand, biological oxygen demand, total nitrogen and total phosphorous were measured in effluent, with values of 100 ± 10; 12 ± 2; 9.6 ± 0.5 and 4 ± 0.2 mg∙L−1, and removal values of 86%, 87%, 84% and 64%, respectively. Likewise, an EHC (ultra-low energy consumption) was built with 6.3 V UCC® 4700 µF capacitors that harvested and stored energy from MFCs in parallel. Energy management was programmed on a microcontroller Atmega 328PB®. The water quality of the treated effluent complied with the maximum levels set by the Mexican Official Standard NOM-001-SEMARNAT-1996-C. A cost analysis showed that MFCSS could be competitive as a sustainable and energy-efficient technology for real domestic wastewater treatment.

Hydrogen production from microbial fuel cells-ammonia electrolysis cell coupled system fed with landfill leachate using Mo2C/N-doped graphene nanocomposite as HER catalyst

In this work, we reported hydrogen production from ammonia-rich wastewater using series stacked microbial fuel cells (MFCs)-ammonia electrolytic cell (AEC) coupled system with Mo2C/N-doped graphene (Mo2C/N-rGO) nanocomposite as hydrogen evolution reaction (HER) catalyst. The electrocatalytic activity of Mo2C/N-rGO nanocomposite towards HER, the performance of simultaneous bioelectricity and hydrogen production as well as landfill leachate treatment of this coupled system were investigated under continuous parallel flow mode. Results demonstrated that four air-cathode MFCs in series stacking harvested the highest power density of 536 mW m−2 when fed with glucose and ammonium mixture, and meanwhile approximately 59 μL gMo2C/N-rGO−1 h−1 of hydrogen production rate was achieved with continuous bioelectricity supply to the AEC unit. As the substrate was shifted to actual landfill leachate (dilution ratio of 1:4), only ca. 143 mW m−2 of maximal output power was obtained from the series stacked MFCs, but it still accomplished 71% NH4+-N removal efficiency and about 42 μL gMo2C/N-rGO−1 h−1 of hydrogen production rate. This MFCs-AEC coupled bio-electrochemical system highlighted its potential for hydrogen production from real landfill leachate along with simultaneous chemical oxygen demand and ammonia-nitrogen removal without the need for external electricity supply, thus achieving the resource and energy re-utilization of ammonia-rich wastewater.

Effect of Stacking Microbial Fuel Cells on Electricity Generation from Sludge

Microbial fuel cells (MFCs) are bioreactors that convert energy in the chemical bonds of organic compounds into electrical energy through catalytic activity of electrogenic micro-organisms, under anaerobic conditions. In this study, a stacked MFC consisting of 4 single MFCs was assembled using microbial sludge and connected in series. 1.0 V of electricity was generated in each cell and as much as 4.0V of electricity was generated in the four stacked cells. The stacked MFC was used to power a flashlight and a 4.0-volt LED light bulb. The electricity generated decreased with time due to a decrease in microbial activity and increased with increase in the number of stacked cells.

Performance assessment of a four-air cathode membraneless microbial fuel cell stack for wastewater treatment and energy extraction

A stack of two identical single chamber microbial fuel cells (MFCs) was assessed during using fermentable house hold extract as substrate. The design of the MFC units was based on the single chamber membrane-less technology using four cathode electrodes. The total power output was 492 mW either in series or parallel connection considering a total anolyte volume of 240 cm3. During continuous operation, the COD removal was 80% for each cell and for both operation modes (series and parallel). The electrochemical profiles provided significant information on the behaviour of the stack. During continuous operation, parallel connection is preferred over series connection, as it results to the same power output values, and COD removal but it provides lower internal resistances leading to more stable electrochemical performance behaviour.

Assessing the impact of design factors on the performance of two miniature microbial fuel cells

Every day, wastewater treatment requires large amounts of electricity. Microbial Fuel Cells (MFCs) can convert wastewater treatment plants from net power consumers into energy neutral/positive systems by generating electricity from wastewaters. We investigate here the design factors that have major impacts on the performance of two miniature MFCs, and, consequently, of the resulting stack of MFCs. A versatile mathematical model is provided, which simulates the complex MFC system by integrating fluid dynamic principles with mass transport phenomena and (bio)electrochemical reactions. The model is used to support an in-depth study of the two MFCs, which differ for electrode spacing, anodic volume and fluid pattern within the anodic chamber, and to associate any difference in performance to design factors. Finally, system scale-up is demonstrated by generating stacks of the two MFCs. Thanks to the versatility of the model developed, this study becomes a guide for the effective development of future miniature MFCs.

Inovasi Sistem Stack Microbial Fuel Cell menggunakan Substrat Limbah Rumen Sapi serta Implementasinya sebagai Media Pembelajaran

ABSTRACT[Innovation of microbial fuel cell stack system using cow rumen waste substrate and its implementation as a learning media]. The aims of this study are to: 1) describe the difference of Electric Motion (GGL), 2) describe the difference of electric power per unit area of the anode (Pa) which is produced between the series design MFC type series, parallel, mixed type 1 and mixed type 2, and 3) describe the significant difference of learning outcomes between the PBL learning model using MFC media with PBL learning model by using the electrical kit medium on dynamic electrical concept in SMA Muhammadiyah 4 Bengkulu. The free variable of this research are MFC stack system design (series, parallel, mixed types 1 and 2) and the dependent variable is GGL and electric power per unit of anode surface area. The results are obtained difference GGL and Pa between series design, parallel, mixed types 1 and 2 by comparison are 3: 1: 1,5: 2 whereas Pa ratio is 1: 10: 6: 2 with maximum GGL is obtained in series design of 3,29 V and Pa maximum in parallel circuit 21,76 mW / m2. Implementation of MFC series as a learning media used Problem Based Learning model on physics learning Implementation of MFC circuit with research design using one group pretest-posttest design. The testing of hypothesis with t-test shows tcount 2.739> ttable 2,001 and 95% significant level so it can be concluded there are significant differences in learning outcomes of PBL learning model by using MFC media with PBL learning model by using media Electric Kit on dynamic electrical concept in SMA Muhammadiyah 4 Bengkulu. Keywords: Stack Microbial Fuel Cell (MFC) Sistem; Rumen Cow Liquid Waste; Learning Media.

Inovasi Sistem Stack Microbial Fuel Cell menggunakan Substrat Limbah Rumen Sapi serta Implementasinya sebagai Media Pembelajaran

ABSTRACT[Innovation of microbial fuel cell stack system using cow rumen waste substrate and its implementation as a learning media]. The aims of this study are to: 1) describe the difference of Electric Motion (GGL), 2) describe the difference of electric power per unit area of the anode (Pa) which is produced between the series design MFC type series, parallel, mixed type 1 and mixed type 2, and 3) describe the significant difference of learning outcomes between the PBL learning model using MFC media with PBL learning model by using the electrical kit medium on dynamic electrical concept in SMA Muhammadiyah 4 Bengkulu. The free variable of this research are MFC stack system design (series, parallel, mixed types 1 and 2) and the dependent variable is GGL and electric power per unit of anode surface area. The results are obtained difference GGL and Pa between series design, parallel, mixed types 1 and 2 by comparison are 3: 1: 1,5: 2 whereas Pa ratio is 1: 10: 6: 2 with maximum GGL is obtained in series design of 3,29 V and Pa maximum in parallel circuit 21,76 mW / m2. Implementation of MFC series as a learning media used Problem Based Learning model on physics learning Implementation of MFC circuit with research design using one group pretest-posttest design. The testing of hypothesis with t-test shows tcount 2.739> ttable 2,001 and 95% significant level so it can be concluded there are significant differences in learning outcomes of PBL learning model by using MFC media with PBL learning model by using media Electric Kit on dynamic electrical concept in SMA Muhammadiyah 4 Bengkulu. Keywords: Stack Microbial Fuel Cell (MFC) Sistem; Rumen Cow Liquid Waste; Learning Media.

Miniaturized Ceramic-Based Microbial Fuel Cell for Efficient Power Generation From Urine and Stack Development.

One of the challenges in Microbial Fuel Cell (MFC) technology is the improvement of the power output and the lowering of the cost required to scale up the system to reach usable energy levels for real life applications. This can be achieved by stacking multiple MFC units in modules and using cost effective ceramic as a membrane/chassis for the reactor architecture. The main aim of this work is to increase the power output efficiency of the ceramic based MFCs by compacting the design and exploring the ceramic support as the building block for small scale modular multi-unit systems. The comparison of the power output showed that the small reactors outperform the large MFCs by improving the power density reaching up to 20.4 W/m3 (mean value) and 25.7 W/m3 (maximum). This can be related to the increased surface-area-to-volume ratio of the ceramic membrane and a decreased electrode distance. The power performance was also influenced by the type and thickness of the ceramic separator as well as the total surface area of the anode electrode. The study showed that the larger anode electrode area gives an increased power output. The miniaturized design implemented in 560-units MFC stack showed an output up to 245 mW of power and increased power density. Such strategy would allow to utilize the energy locked in urine more efficiently, making MFCs more applicable in industrial and municipal wastewater treatment facilities, and scale-up-ready for real world implementation.

Microbial fuel cell stack power to lithium battery stack: Pilot concept for scale up

A stack to stack microbial fuel cell power to batteries storage was investigated on the pilot scale with the aim to scale up in future. A 12 unit MFC-stack, equipped with maximum power point tracking (MPPT) and lithium polymer batteries (3.7 V), was set up. The MFC-stack architecture was simplified by sharing partially electrolytes. The serial 12 unit MFC-stack was first used as a linear assembly of all MFC units and then subdivided into three MFC-sub-stacks which enhanced power extraction by 8.5 times. To balance the stack power generation, the external circuits were alternated into zigzag, braid and random figurations as well in rational directed configurations. Finally, batteries permutation along with MPPT enabled faster and balanced lithium battery stack charging. Balanced conditions resulted in time shift oscillations, the absence of unwanted power pooling and voltage reversals. All in all, the work showed how to generate and store power from an 12 L microbial fuel cell stack with partly common electrolytes.

Blocking oscillator-based electronic circuit to harvest and boost the voltage produced by a compost-based microbial fuel cell stack

Energy obtained from microbial fuel cells (MFCs) is often considered low for practical applications; however, this issue has been overcome by developing electronic circuits that power low-consumption devices such as environmental sensors. Even with recent technical advances, power management systems (PMSs) that target household applications are scarce, while worldwide demand for green energy continuously grows. This research aims to design an electronic circuit to harvest and boost the energy produced by a MFC stack and demonstrates its practical application by powering an LED array. Ceramic and electrolytic capacitors were compared, and an electrolytic capacitor was selected (22 μF, 25 V, 0.11 s). A PMS was constructed utilizing an electrolytic capacitor (22 μF) linked to a blocking oscillator with a toroidal ferrite core that was used as the primary component to boost the MFC output potential. The circuit was operated with three compost-based MFCs connected in series as a power source. The open circuit potential of the MFC stack was 2.25 V, but the useful voltage was 0.837 V in a closed circuit, with a maximum power density of 173 mW m−2. The harvest-and-boost electronic circuit increased the voltage of the MFC stack by 3.6 fold with respect to the pulse peak although the effective voltage increase was 71%, which could power a 10-LED array (3 V).

Field Trial of Self-Stratifying Membrane-Less Microbial Fuel Cells Stacks in an Autonomous and Self-Powered Urinal

The main competitive advantage of the microbial fuel cell (MFC) technology is to generate electricity from organic waste, which is otherwise considered expensive to treat; as such, interest in this field has intensified over the two last decades. Efforts have mainly focussed on improving the materials employed, the design configuration and the energy-harvesting peripherals. Many improvement solutions have been proposed within the last decade, more and more pilot-scale systems feeding on various kinds of feedstock have been tested (e.g. domestic wastewater, brewery waste, marine sediments, urine). A previous field trial at Glastonbury Music Festival has already demonstrated the feasibility of directly using urine from festival goers to light-up a urinal, thereby setting a benchmark in urine fuelled-MFCs for self-sustainable applications [1]. Furthermore, the concept of self-stratifying membraneless MFC (SSM-MFC) has also been reported. This approach allows scaling-up units’ sizes without significant power density losses, within the tested range (from 900 mL to 5000mL), a factor that has proven an obstacle in previous studies. This design had only been tested under controlled laboratory conditions and never trialled under real usage conditions [2, 3]. In the current study the results of an autonomous system, which was tested at the Glastonbury Music Festival 2016 are presented. To perform this trial, large MFC modules were built, tested and integrated in a setup that comprised a urinal, a stack of 12 SSM-MFCs modules, and an energy management control system harvesting the generated energy to power the lighting of the urinal. The urinal was large enough to accommodate 12 users at any given time and consisted of troughs directing urine to a buffer tank. This tank, equipped with an over flow redirecting excess urine, was connected to a passive feeding mechanism that was supplying urine to a MFC stack of 12 modules every time a volume of 9 L was reached. The stack was set with 6 independent cascades, each having 2 MFC modules electrically connected in parallel. Each module of the cascade comprised 38 MFCs submerged in the same electrolyte and electrically connected in parallel. All six cascades were electrically connected in series. The energy was then harvested and stored in a battery bank. At night (≈9h30 duty-cycles), the control board was redirecting the energy towards 6 LED strips (2.862W) lighting the urinal. Results from laboratory conditions have shown that the power density of a single module was ~2.75 W.m-3, whereas under real conditions the power density ranged from ~1.70 to ~2.36 W.m-3 (total volumetric footprint). The energy harvested from the undiluted urine was sufficient to power the PEE POWER® lights for 9h30 every day. Under laboratory conditions, at 44h hydraulic retention time (HRT) the COD was reduced from 5.586 mg COD.L-1 to 0.625 mg COD.L-1 (88%); the nitrogen was also reduced by 29%. In the field, with a HRT of 11h40, the COD decreased by 48% and the total nitrogen content by 13%. When plotting data from the laboratory tests together with the ones of the field trial, the fitted Michaelis-Menten curve (r2=0.960) indicates that with a HRT of ≈64h, the COD could be reduced to the European Union standard for discharge (0.125 mg COD.L-1). Compared to the 2015 field trial benchmark [1], the present system demonstrates a 37 % higher COD removal with a 50% shorter HRT, and produced ≈30% more energy in a third of the total volumetric footprint. Overall, these results correspond to an over 7-fold technological improvement. [1] Ieropoulos IA, Stinchcombe A, Gajda I, Forbes S, Merino-Jimenez I, Pasternak G, Sanchez-Herranz D and Greenman J. Pee power urinal - microbial fuel cell technology field trials in the context of sanitation. Environ. Sci.-Wat. Res. Technol. 2016;2:336-343 [2] Walter XA, Gajda I, Forbes S, Winfield J, Greenman J and Ieropoulos I. Scaling-up of a novel, simplified MFC stack based on a self-stratifying urine column. Biotechnology for Biofuel 2016;9:93 [3] Walter XA, Stinchcombe A, Greenman J and Ieropoulos I. Urine transduction to usable energy: a modular MFC approach for smartphone and remote system charging. Applied Energy 2017;192:575-581

Investigation of ceramic MFC stacks for urine energy extraction

Two ceramic stacks, terracotta (t-stack) and mullite (m-stack), were developed to produce energy when fed with neat undiluted urine. Each stack consisted of twelve identical microbial fuel cells (MFCs) which were arranged in cascades and tested under different electrical configurations. Despite voltage reversal, the m-stack produced a maximum power of 800 μW whereas the t-stack produced a maximum of 520 μW after 62.6 h of operation. Moreover, during the operation, both systems were subject to blockage possibly due to struvite. To the Authors' best knowledge, this is the first time that such a phenomenon in ceramic MFC membranes is shown to be the direct result of sub-optimal performance, which confirms the hypothesis that ceramic membranes can continue operating long-term, if the MFCs produce maximum power (high rate of e− transfer). Furthermore, it is shown that once the ceramic membrane is blocked, it may prove difficult to recover in-situ.

Ceramic Microbial Fuel Cells Stack: power generation in standard and supercapacitive mode

In this work, a microbial fuel cell (MFC) stack containing 28 ceramic MFCs was tested in both standard and supercapacitive modes. The MFCs consisted of carbon veil anodes wrapped around the ceramic separator and air-breathing cathodes based on activated carbon catalyst pressed on a stainless steel mesh. The anodes and cathodes were connected in parallel. The electrolytes utilized had different solution conductivities ranging from 2.0 mScm−1 to 40.1 mScm−1, simulating diverse wastewaters. Polarization curves of MFCs showed a general enhancement in performance with the increase of the electrolyte solution conductivity. The maximum stationary power density was 3.2 mW (3.2 Wm−3) at 2.0 mScm−1 that increased to 10.6 mW (10.6 Wm−3) at the highest solution conductivity (40.1 mScm−1). For the first time, MFCs stack with 1 L operating volume was also tested in supercapacitive mode, where full galvanostatic discharges are presented. Also in the latter case, performance once again improved with the increase in solution conductivity. Particularly, the increase in solution conductivity decreased dramatically the ohmic resistance and therefore the time for complete discharge was elongated, with a resultant increase in power. Maximum power achieved varied between 7.6 mW (7.6 Wm−3) at 2.0 mScm−1 and 27.4 mW (27.4 Wm−3) at 40.1 mScm−1.

Assessment of organic removal in series- and parallel-connected microbial fuel cell stacks

Microbial fuel cells (MFCs) degrade organic contaminants in wastewater while simultaneously producing electricity, but must be stacked to yield adequate voltage and current. This study examined the evolution of the chemical oxygen demand (COD) removal rate and efficiency in two identical individual MFCs (i-MFCs) in series- and parallel-connected stacks (sc- and pc-MFCs, respectively) under batch and continuous operation. The stack voltage and current increased in the respective series and parallel connections of the two i-MFCs (MFC unit 1 and MFC unit 2). Voltage reversal was observed in the sc- MFC below an external load of 100 Ω. Regardless of occurrence of the voltage reversal, organic reduction between i-MFCs and sc-MFCs showed no significant difference (gap of < 9% and < 6% in COD removal rate and efficiency, respectively); additionally, organic removals between the two individual MFCs in series indicated differences less than 9% of COD removal rate and 5% of COD removal efficiency in batch mode. Continuous operation also yielded similar organic removals as the MFCs in individual and series connection (voltage reversal occurred) mode, even over 8 days operation. Parallel connection yielded identical organic removals and currents in the two individual MFCs of the pc-MFC, even though the two separate i-MFCs showed different organic removal rates and current productions. This study provides the guide for the application of stacked MFCs for power source and efficient organic pollutant removal in wastewater treatment process.

Voltage reversal causes bioanode corrosion in microbial fuel cell stacks

A better understanding of voltage reversal phenomenon and its long-term effects on power generation are crucial to efficiently improve the voltage of microbial fuel cell (MFC) stacks. In this study, six MFCs with imbalanced performances were connected in series. After over 100 h of operation under voltage reversal conditions, increased turbidity and color were observed in the anolyte of the reversed MFC. In addition, the cyclic voltammogram of the anode changed form a typical catalytic current to a capacitance current. The scanning electron microscopy (SEM) showed that biofilm was dissociated from the anode surface, indicating that long-term operation under voltage reversal could damage the biofilm and ultimately resulted in the failure of MFC stacks. X-ray diffraction (XRD) and SEM equipped with energy dispersive X-ray spectrometry (EDX) analyses showed that the black particles in the anolyte was mostly carbon exfoliated from the anode, suggesting that carbon corrosion caused the biofilm failure.