Praveena Gangadharan, Indumathi M. Nambi, Jaganathan Senthilnathan et al.

RSC Advances • 2016

In the present study, a low molecular heterocyclic aminopyrazine (Apy)–reduced graphene oxide (r-GO) hybrid coated carbon cloth (r-GO–Apy–CC) was employed as an active and stable bio-electro catalyst in a microbial fuel cell (MFC).

M. Al-badani, Peng Chong, Heng-Siong Lim

International Journal of Green Energy • 2023

ABSTRACT Microbial fuel cells (MFCs) have attracted much interest as an alternative energy conversion technology and as a system for recovering and treating wastewater. MFC is a powerful technique for generating energy from various sources, including natural organic matter and renewable biomass. It has several possible applications, including power generation for many small electronic devices, wastewater treatment, and biosensors. However, the restricted power output of MFCs is the most significant impediment to their widespread use and up-scaling in practical applications. The anode electrode is the most critical component of an MFC, where poor anode electrode performance leads to poor MFC efficiency. Therefore, efforts have been made to modify electrodes to improve their performance. While power density is an essential metric in determining MFC efficiency, other parameters such as Coulombic efficiency, current density, cell voltage, and the removal rate of chemical oxygen demand (COD) should also be considered to evaluate the performance of MFC. This study reviews the most recent electrode modification techniques through anode treatments with metal oxides, conductive polymers, carbon nanotubes, and other chemical compounds as well as through cathode modifications. Different modified MFCs are compared in terms of their power density and the type of bacteria and membrane used.

Sri Sathya Sandilya Garimella, Sai Vennela Rachakonda, Sai Sowmya Pratapa et al.

Annals of Microbiology • 2024

Microbial fuel cells (MFCs), which use bacterial electron transport mechanisms to generate energy, have become a viable technology for renewable energy production. This review investigates the evolutionary and functional connections between bacterial energy transduction mechanisms and mitochondrial electron transport chains, building on the endosymbiont theory of eukaryotic cell evolution. The conserved features and similarities between prokaryotic and eukaryotic electron transport pathways were elucidated, highlighting their common origins and roles in cellular bioenergetics. This discussion explores the essential mechanisms governing the movement of electrons and ions across biological membranes, crucial for generating energy and maintaining electrochemical gradients in bacteria and mitochondria. Capitalizing on these insights, we explore the applications of electrogenic bacteria in MFCs for renewable electricity generation. Optimal conditions for enhancing bacterial electron transfer to electrode surfaces are identified, paving the way for improved MFC performance. Potential large-scale implementations of MFCs in wastewater treatment, biosensing, and bioremediation of contaminated environments are discussed, underscoring their versatility and environmental benefits. The importance of investigating bioenergetic mechanisms at both the cellular and molecular scales of fully harnessing the capabilities of microbial energy conversion systems is highlighted in this review. By bridging the gap between fundamental cellular processes and sustainable technologies, we aim to advance renewable energy solutions that harness the remarkable capabilities of electrogenic microorganisms.

Akshat Sharma, Lara Đelević, Katharina Herkendell

Energy Technology • 2024

The adoption of microbial fuel cell (MFC) technology hinges on the development of efficient proton‐exchange membranes (PEMs), which significantly influences fuel cell performance and cost. PEMs have a critical role in preventing oxygen crossover, maintaining electrochemical neutrality, and supporting microorganisms within MFCs. Nafion, the current industry‐standard PEM, grapples with environmental, cost, and performance issues. Although improvements to Nafion have been reported using additives, immersion in heteropolyacids, different pretreatment methods, and UV irradiation, many of the challenges still remain. Herein, the recent developments in the area of alternative PEMs are reviewed and analyzed. Among them, sulfonated aromatic hydrocarbons, particularly sulfonated polyether ether ketone, have emerged as top contenders in terms of scale up and commercial viability. At the same time, membranes based on polyvinyl alcohol, ionic liquids, and natural materials are also being actively researched for various MFC applications. Since most studies are short term and lab scale, there is a need evaluate long‐term stability and economic cost of PEMs in terms of standardized parameters such as power‐to‐cost and normalized energy recovery. Additionally, for emerging low‐energy‐density MFC applications like biosensors and in vivo power sources, PEM properties and design need to be tailored carefully.

Huajun Feng, Yuxiang Liang, K. Guo et al.

Environmental Science & Technology Letters • 2016

Titanium has been widely used as a dimensionally stable anode in the electrolysis industry because of its excellent corrosion resistance, conductivity, and scalability. However, because of its poor biocompatibility and poor performance as a bioanode, it has drawn little attention in the field of microbial fuel cells (MFCs). This study reports an efficient way to convert a titanium electrode into a high-performance anode for MFCs, in situ growth of titanium dioxide nanotubes (TNs) on its surface. After TN modification, the titanium surface became rougher, more hydrophilic, and more conducive for anodic biofilm formation. The maximal current density achieved on this TN-modified titanium electrode was 12.7 A m–2, which was 190-fold higher than that of the bare titanium electrode and even higher than that of the most commonly used carbon felt electrode. Therefore, the high conductivity, corrosion resistance, and current density make the TN-modified titanium electrode a promising and scalable anode for MFCs.

Zejie Wang, B. Lim

Environmental Engineering Research • 2019

Sediment microbial fuel cells (SMFCs) illustrated great potential for powering environmental sensors and bioremediation of sediments. In the present study, array anodes for SMFCs were fabricated with graphite rods as anode material and stainless steel plate as electric current collector to make it inconvenient to in situ settle down and not feasible for large-scale application. The results demonstrated that maximum power of 89.4 μW was obtained from three graphite rods, twice of 43.3 μW for two graphite rods. Electrochemical impedance spectroscopy revealed that three graphite rods resulted in anodic resistance of 61.2 Ω, relative to 76.0 Ω of two graphite rods. It was probably caused by the parallel connection of the graphite rods, as well as more biomass which could reduce the charge transfer resistance of the biofilm anode. The presently designed array configuration possesses the advantages of easy to enlarge the surface area, decrease in anodic resistance because of the parallel connection of each graphite rod, and convenience to berry into sediment by gravity. Therefore, the as prepared array node would be an effective method to fabricate large-scale SMFC and make it easy to in situ applicate in natural sediments.

Wenbin Liu, Leiming Lin, Ying Meng et al.

Environmental Science: Nano • 2021

Microbial fuel cell with titanium dioxide nanotube array cathode was first demonstrated as a promising approach for uranium recovery and separation from groundwater.

Weihua He, Xiaoyuan Zhang, Jia Liu et al.

Environmental Science: Water Research & Technology • 2016

A new type of scalable MFC was developed based on using alternating graphite fiber brush array anode modules and dual cathode modules in order to simplify construction, operation, and maintenance of the electrodes. The modular MFC design was tested with a single (two-sided) cathode module with a specific surface area of 29 m2 m−3 based on a total liquid volume (1.4 L; 20 m2 m−3 using the total reactor volume of 2 L), and two brush anode modules. Three different types of spacers were used in the cathode module to provide structural stability, and enhance air flow relative to previous cassette (combined anode–cathode) designs: a low-profile wire spacer; a rigid polycarbonate column spacer; and a flexible plastic mesh spacer. The best performance was obtained using the wire spacer that produced a maximum power density of 1100 ± 10 mW m−2 of cathode (32 ± 0.3 W m−3 based on liquid volume) with an acetate-amended wastewater (COD = 1010 ± 30 mg L−1), compared to 1010 ± 10 mW m−2 for the column and 650 ± 20 mW m−2 for the mesh spacers. Anode potentials were unaffected by the different types of spacers. Raw domestic wastewater produced a maximum of 400 ± 8 mW m−2 under fed batch conditions (wire-spacers), which is one of the highest power densities for this fuel. Over time the maximum power was reduced to 300 ± 10 mW m−2 and 275 ± 7 mW m−2 for the two anode compartments, with only slightly less power of 250 ± 20 mW m−2 obtained under continuous flow conditions. In fixed-resistance tests, the average COD removal was 57 ± 5% at a hydraulic retention time of 8 h. These results show that this modular MFC design can both simplify reactor construction and enable relatively high power generation from even relatively dilute wastewater.

Thorben Muddemann, Dennis Haupt, Bolong Jiang et al.

Processes • 2019

This contribution describes the effect of the quality of the catalyst coating of cathodes for wastewater treatment by microbial fuel cells (MFC). The increase in coating quality led to a strong increase in MFC performance in terms of peak power density and long-term stability. This more uniform coating was realized by an airbrush coating method for applying a self-developed polymeric solution containing different catalysts (MnO2, MoS2, Co3O4). In addition to the possible automation of the presented coating, this method did not require a calcination step. A cathode coated with catalysts, for instance, MnO2/MoS2 (weight ratio 2:1), by airbrush method reached a peak and long-term power density of 320 and 200–240 mW/m2, respectively, in a two-chamber MFC. The long-term performance was approximately three times higher than a cathode with the same catalyst system but coated with the former paintbrush method on a smaller cathode surface area. This extraordinary increase in MFC performance confirmed the high impact of catalyst coating quality, which could be stronger than variations in catalyst concentration and composition, as well as in cathode surface area.

Tianjiao Guo, Chunyan Zhang, Jingkai Zhao et al.

Scientific Reports • 2019

Abstract A Chemical absorption-bioelectrochemical reduction (CABER) system is based on Chemical absorption-biological reduction (CABR) system, which aims at NO removal and has been studied in many of our previous works. In this paper, we applied polypyrrole (PPy) on the electrode of bioelectrochemical reactor (BER) of CABER system, which induced a much higher current density in the cyclic voltammetry (CV) curve for the electrode itself and better NO removal rate in the system. In addition, a Microbial Electrolysis Cell (MEC) is constructed to study its strengthening mechanism. Results shows that PPy-MEC has a greater Faraday efficiency and higher reduction rate of Fe(III)EDTA and Fe(II)EDTA-NO in the solution when compared to original Carbon MEC, which confirms the advantage of PPy-modified electrode(s) in the CABER system. The results of this study are reported for illustration of potential of CABER technology and design of low-cost high-efficiency NO x control equipment in the future.

Xiaolin Zhang, Xiaojing Li, Xiaodong Zhao et al.

RSC Advances • 2019

The great potential of bioelectrochemical systems (BESs) in pollution control combined with energy recovery has attracted increasing attention.

Angela Cantillo-González, Javiera Anguita, Claudia Rojas et al.

Micromachines • 2022

Bioelectrochemical systems (BESs) have been extensively studied for treatment and remediation. However, BESs have the potential to be used for the enrichment of microorganisms that could replace their natural electron donor or acceptor for an electrode. In this study, Winogradsky BES columns with As-rich sediments extracted from an Andean watershed were used as a strategy to enrich lithotrophic electrochemically active microorganisms (EAMs) on electrodes (i.e., cathodes). After 15 months, Winogradsky BESs registered power densities up to 650 μWcm−2. Scanning electron microscopy and linear sweep voltammetry confirmed microbial growth and electrochemical activity on cathodes. Pyrosequencing evidenced differences in bacterial composition between sediments from the field and cathodic biofilms. Six EAMs from genera Herbaspirillum, Ancylobacter, Rhodococcus, Methylobacterium, Sphingomonas, and Pseudomonas were isolated from cathodes using a lithoautotrophic As oxidizers culture medium. These results suggest that the tested Winogradsky BES columns result in an enrichment of electrochemically active As-oxidizing microorganisms. A bioelectrochemical boost of centenarian enrichment approaches, such as the Winogradsky column, represents a promising strategy for prospecting new EAMs linked with the biogeochemical cycles of different metals and metalloids.

Manoj Kumar, Rajesh Singh

Environmental Science: Water Research & Technology • 2020

In the present study, we investigated the role of constructed wetlands (CWs) integrated with a bioelectrochemical system (BES), which can concurrently treat wastewater effectively with energy recovery.

Jing Wang, Ming Li, Fangtai Liu et al.

Journal of Nanomaterials • 2016

We proposed a self-connected carbon nanofiber design for electrode in microbial bioelectrochemical system. This design was realized by direct growth of carbon nanofibers (CNFs) onto stainless steel (SSM) via a chemical vapor deposition process without addition of any external catalysts. In the CNFs-SSM composite electrode, the SSM acted as the conductive network and ensured efficient substrate and proton transfer, and the CNFs layer served as highly porous habitats for thick biofilm propagation. The current generated by the CNFs-SSM was 200 times higher than the bare SSM under the same experimental conditions. This provided a simple and promising method for preparation of electrode material with high performance and low-cost in bioelectrochemical system.

Hui Wang, Ying Du, XiangHua Wang et al.

Fuel Cells • 2024

ABSTRACT Refractory organic pollutant removal can be enhanced by a bioelectrochemical system via the addition of electron donors/acceptors. In this study, a single‐chamber soil microbial fuel cell (MFC) was constructed, and electricity production and atrazine removal efficiency were assessed using different co‐substrates and phosphate buffer concentrations. The co‐substrates compensated for the lack of soil organic matter and provided a sufficient carbon source for microorganisms to facilitate MFC electricity generation and efficient atrazine removal. The maximum voltage (94 mV), power density (39.41 mW m −2 ), removal efficiency (85.30%), and degradation rate (1.68 mg kg −1 d −1 ) were highest in the soil MFCs with sodium acetate when compared with the other groups. Phosphate buffer significantly alleviated the dramatic soil pH change. The electricity generation and atrazine removal efficiency increased with the buffer concentration (0–0.10 g L −1 ). The maximum voltage (144 mV) and power density (89.35 mW m −2 ) were highest, total internal resistance (652 Ω) was lowest, and atrazine removal efficiency (90.95%) and degradation rate (1.54 mg kg −1 d −1 ) were determined in the soil MFCs with the phosphate buffer concentration of 0.10 g L −1 , and. These results indicate that the co‐substrate and phosphate buffer can enhance the electricity generation of soil MFCs and atrazine removal.

Philipp Arbter, Niklas Widderich, Tyll Utesch et al.

Microbial Cell Factories • 2022

Abstract Background Electro-fermentation (EF) is an emerging tool for bioprocess intensification. Benefits are especially expected for bioprocesses in which the cells are enabled to exchange electrons with electrode surfaces directly. It has also been demonstrated that the use of electrical energy in BES can increase bioprocess performance by indirect secondary effects. In this case, the electricity is used to alter process parameters and indirectly activate desired pathways. In many bioprocesses, oxidation-reduction potential (ORP) is a crucial process parameter. While C. pasteurianum fermentation of glycerol has been shown to be significantly influenced electrochemically, the underlying mechanisms are not clear. To this end, we developed a system for the electrochemical control of ORP in continuous culture to quantitatively study the effects of ORP alteration on C. pasteurianum by metabolic flux analysis (MFA), targeted metabolomics, sensitivity and regulation analysis. Results In the ORP range of −462 mV to −250 mV, the developed algorithm enabled a stable anodic electrochemical control of ORP at desired set-points and a fixed dilution rate of 0.1 h −1 . An overall increase of 57% in the molar yield for 1,3-propanediol was observed by an ORP increase from −462 to −250 mV. MFA suggests that C. pasteurianum possesses and uses cellular energy generation mechanisms in addition to substrate-level phosphorylation. The sensitivity analysis showed that ORP exerted its strongest impact on the reaction of pyruvate-ferredoxin-oxidoreductase. The regulation analysis revealed that this influence is mainly of a direct nature. Hence, the observed metabolic shifts are primarily caused by direct inhibition of the enzyme upon electrochemical production of oxygen. A similar effect was observed for the enzyme pyruvate-formate-lyase at elevated ORP levels. Conclusions The results show that electrochemical ORP alteration is a suitable tool to steer the metabolism of C. pasteurianum and increase product yield for 1,3-propanediol in continuous culture. The approach might also be useful for application with further anaerobic or anoxic bioprocesses. However, to maximize the technique's efficiency, it is essential to understand the chemistry behind the ORP change and how the microbial system responds to it by transmitted or direct effects.

Manoj Kumar, Rajesh Singh

Environmental Science: Water Research & Technology • 2020

In this study, two-phase continuous vertical flow constructed wetlands were installed with a pre-cleaner bioelectrochemical system for the removal of NH 4 + -N (60.41–85.78%), NO 3 − -N (25.55–35.18%), TN (57.80–84.65%), TKN (37.24–70.08%), PO 4 3− -P (38.89–63.40%), SO 4 2− (49.53–76.06%), and COD (25.83–74.70%) from municipal wastewater.

Young Eun Song, Changman Kim, Jiyun Baek et al.

Sustainable Energy & Fuels • 2020

The high CODH activity appears to have a synergistic effect with an electrode-assisted electron transfer, and thus maximize the conversion of acetate and VFAs from electrosynthesis with CO.

Anna Weimer, Jens Krömer, Bin Lai et al.

Microbial Biotechnology • 2025

ABSTRACT Mediator‐based extracellular electron transfer (EET) in a bioelectrochemical system is a unique approach to regulate the microbial redox and energy metabolism of Pseudomonas putida KT2440, which enables a new‐to‐nature high product yield under anaerobic conditions. Previous studies identified respiratory complex III in the inner membrane as a key redox protein involved in mediator (ferricyanide) interactions, but the exact mechanism through which the mediator crosses the outer membrane to extract electrons from membrane‐bound redox proteins and transfer them to the anode remains unclear. In this study, we demonstrated the critical role of the TonB‐dependent system, a widespread transportation system in gram‐negative bacteria, in the mediator‐based EET process. Transcriptomic analyses revealed significant upregulation of TonB‐dependent receptors in response to ferricyanide exposure, suggesting their involvement in mediator uptake. Deletion of the TonB complex resulted in a > 50% decrease in the mediator reduction rate and current output, confirming the role of the TonB‐dependent system in mediator transport. Additionally, increasing passive diffusion through the overexpression of the general porin OprF increased cell permeability and the mediator reduction rate, but it failed to compensate for the absence of TonB‐dependent transport. These findings suggest that both systems act in a complementary manner: the TonB‐dependent system is likely the primary mechanism for periplasmic mediator uptake, whereas OprF is likely involved mainly in mediator efflux. Further bioelectrochemical system experiments demonstrated that, with a functional TonB‐dependent system, OprF overexpression increased current output, glucose consumption, and 2‐ketogluconate production, suggesting a viable strategy for enhancing the efficacy of mediator‐based EET. This work reveals the major mediator transport mechanism in P. putida and deepens the understanding of the mediator‐based EET pathway, laying the basis for future rational engineering of EET kinetics and facilitating the integration of mediator‐based electron transfer into industrial biotechnology to push its process boundaries.

Christy M. Dykstra, Spyros G. Pavlostathis

Biotechnology and Bioengineering • 2017

ABSTRACT Bioelectrochemical systems (BESs) may be used to upgrade anaerobic digester biogas by directly converting CO 2 to CH 4 . The objective of this study was to evaluate gas (N 2 , CO 2 , CH 4 , and H 2 ) and carbon transport within a methanogenic BES. Four BES configurations were evaluated: abiotic anode with abiotic cathode (AAn‐ACa), bioanode with abiotic cathode (BAn‐ACa), abiotic anode with biocathode (AAn‐BCa), and bioanode with biocathode (BAn‐BCa). Transport of N 2 , a gas commonly used for flushing anoxic systems, out of the anode headspace ranged from 3.7 to 6.2 L/d‐atm‐m 2 , normalized to the proton exchange membrane (PEM) surface area and net driving pressure (NDP). CO 2 was transported from the cathode to the anode headspace at rates from 3.7 to 5.4 L/d‐atm‐m 2 . The flux of H 2 from cathode to anode headspace was 48% greater when the system had a biocathode (AAn‐BCa) than when H 2 was produced at an abiotic cathode (BAn‐ACa), even though the abiotic cathode headspace had 75% more H 2 than the AAn‐BCa biocathode at the end of 1 day. A 7‐day carbon balance of a batch‐fed BAn‐BCa BES showed transient microbial carbon storage and a net transport of carbon from anode to cathode. After a 7‐day batch incubation, the CH 4 production in the biocathode was 27% greater on a molar basis than the initial CO 2 supplied to the biocathode headspace, indicating conversion of CO 2 produced in the anode. This research expands the current understanding of methanogenic BES operation, which may be used in improving the assessment of BES performance and/or in the development of alternative BES designs and mathematical models. Biotechnol. Bioeng. 2017;114: 961–969. © 2016 Wiley Periodicals, Inc.

M. Zeppilli, A. Mattia, M. Villano et al.

Fuel Cells • 2017

Abstract Here, an innovative three‐chamber bioelectrochemical system configuration is proposed to combine COD, CO 2 and NH 4 + removal into a single device. In the proposed process, while COD oxidation and CO 2 reduction occurred, respectively, in the anodic and cathodic chamber, the consequent current generation promoted the migration of target ionic species towards an intermediate accumulation chamber, across cation and anion exchange membranes, respectively. Under this configuration, COD removal proceeded in the anode chamber with an average removal rate of 841 mgCOD L −1 d −1 while the cathode was able to remove 2.1 gCO 2 L −1 d −1 and produce 60 meq L −1 d −1 of CH 4 . Around 90% of the removed CO 2 was contained in the concentrated spill (at around 20 g L −1 of bicarbonate), which was recovered from the intermediate accumulation chamber and also contained the removed nitrogen as ammonium ion (around 32% removal and around 4‐fold concentration with respect to the anode influent). Methane generation allowed a partial recovery of energy of overall energy consumption costs of both COD and CO 2 removal. This study confirms the possibility to combine three processes into a single bioelectrochemical device.

Gowthami Palanisamy, Sadhasivam Thangarasu, Tae Hwan Oh

Polymers • 2023

Microbial fuel cells (MFCs) provide considerable benefits in the energy and environmental sectors for producing bioenergy during bioremediation. Recently, new hybrid composite membranes with inorganic additives have been considered for MFC application to replace the high cost of commercial membranes and improve the performances of cost-effective polymers, such as MFC membranes. The homogeneous impregnation of inorganic additives in the polymer matrix effectively enhances the physicochemical, thermal, and mechanical stabilities and prevents the crossover of substrate and oxygen through polymer membranes. However, the typical incorporation of inorganic additives in the membrane decreases the proton conductivity and ion exchange capacity. In this critical review, we systematically explained the impact of sulfonated inorganic additives (such as (sulfonated) sSiO2, sTiO2, sFe3O4, and s-graphene oxide) on different kinds of hybrid polymers (such as PFSA, PVDF, SPEEK, SPAEK, SSEBS, and PBI) membrane for MFC applications. The membrane mechanism and interaction between the polymers and sulfonated inorganic additives are explained. The impact of sulfonated inorganic additives on polymer membranes is highlighted based on the physicochemical, mechanical, and MFC performances. The core understandings in this review can provide vital direction for future development.

Axel Rous, G. Santa-Catalina, E. D. Quéméner et al.

bioRxiv (Cold Spring Harbor Laboratory) • 2023

The production of nitrogen fertilizers in modern agriculture is mostly based on the Haber-Bosch process, representing nearly 2% of the total energy consumed in the world. Low-energy bioelectrochemical fixation of N2 to microbial biomass was previously observed but the mechanisms of microbial interactions in N2-fixing electroactive biofilms are still poorly understood. The present study aims to develop a new method of enrichment of autotrophic and diazotrophic bacteria from soil samples with a better electron source availability than using H2 alone. The enrichment method was based on a multi-stage procedure. The first enrichment step was specifically designed for the selection of N2-fixing bacteria from soil samples with organic C as electron and carbon source. Then, a polarized cathode was used for the enrichment of autotrophic bacteria using H2 (hydrogenotrophic) or the cathode as electron source. This enrichment was compared with an enrichment culture of pure diazotrophic hydrogenotrophic bacteria without the use of a microbial electrochemical system. Interestingly, both methods showed comparable results for N2 fixation rates at day 340 of the enrichment with an estimated average of approximately 0.2 mgNfixed/L.d. Current densities up to −15 A/m2 were observed in the polarized cathode enrichments and a significant increase of the microbial biomass on the cathode was shown between 132 and 214 days of enrichment.These results confirmed an enrichment in autotrophic and diazotrophic bacteria on the polarized cathode. It was hypothesied that autotrophic bacteria were able to use either the H2 produced at the cathode or directly the cathode through direct electron transfer (DET) as more biomass was produced than with H2 alone. Finally, the analysis of the enriched communities suggested that Desulforamulus ruminis mediated microbial interactions between autotrophic anaerobic and heterotrophic aerobic bacteria in polarized cathode enrichment. These interactions could play a key role in the development of biomass in these systems and on N2 fixation. Based on these findings, a conceptual model on the functioning of mixed cultures N2-fixing electroactive biofilms was proposed.

D. Pant, Suman Bajracharya, G. Mohanakrishna et al.

Qatar Foundation Annual Research Conference Proceedings Volume 2016 Issue 1 • 2016

Microbial Electrosynthesis (MES) comprises electro-reduction of carbon dioxide (CO2) to multi-carbon organic compounds by chemolithotrophs using electrons from a cathode. Reduction of CO2 to chemicals through microbial electrocatalysis was investigated by using a mixed culture of acetogenic and carboxydotrophic bacteria forming a microbial biofilm supported on a carbon based electrode, as biocathode, in a two chamber reactor. The biofilm was developed after a start-up phase with fructose and later on, growing on bicarbonate as substrate at sufficiently negative cathode potential (hydrogen evolution) in a couple of subsequent fed-batch operations. CO2 reduction could occur via direct electron transfer from the electrode or indirectly via mediators or via hydrogen at more reductive potential. Predominantly, Acetic acid was produced along with other volatile fatty acids (VFAs) while applying − 1.1 V/Ag/AgCl cathode potential, along with hydrogen evolution. At the initial stage of fed-batch operation, higher carbon recovery up to 60% was observed from bicarbonate (dissolved CO2) to acetic acid while after accumulation of acetate, the recovery rate went down to 12% as acetate degradation/conversion started or other unmeasured products formed. Maximum acetate production rate achieved during the operation was 40 g m− 2 day− 1 corresponding to coulumbic efficiency of 41%. Microbial analysis of catholyte at the end of the experiment showed that the bacterial community was dominated by Cellulomonas, Stappia and Pseudomonas spp. These results suggest that the mixed culture enriched with acetogenic bacteria can catalyze the electro-reduction of CO2 into a number of chemicals like VFAs through direct or indirect electron transfer mechanisms. While using gaseous CO2 as carbon source, the dissolution and mass transfer of CO2 to the biocatalyst limit the biological reduction process. In addition, the bacterial attachment and retention of reducing equivalent specially hydrogen also restrict the process at the cathode. In order to deal with these issues, a gas diffusion cathode (GDC) (VITO Core™) and a flow-through porous carbon felt cathode were separately tested in MES for CO2 reduction. In principal, the porous activated carbon with hydrophobic binder layer in GDC creates a three-phase interface that makes CO2 and reducing equivalents available to the bacteria. Flow-through graphite felt cathode retains the suspended biomass and electrochemically produced hydrogen when the catholyte is forced to flow through it. An enriched inoculum of acetogenic bacteria, isolated from wastewater sludge was used as biocatalyst. The cathode potentials were maintained at − 0.9 to − 1.1 V vs Ag/AgCl to facilitate CO2 reduction also via the hydrogen evolved at the cathode. On average, CO2 reduction to acetate was achieved with the production rate ∼35 to 43 mg/L/d supplying 20% (v/v) CO2 gas mixture in both the reactors. In the reactors without GDCs or modified cathode, CO2 reduction was never steady for a long period of operation. Acetate was the primary product of CO2 reduction but ethanol and butyrate were also produced concurrently at pH lower than 6. The highest acetate production rate reached in GDC reactor was ∼550 mg/L/d supplying 80% (v/v) CO2 mixture over the GDC. In conclusion, gas diffusion and flow-through cathodes were useful to develop stable CO2 reducing biocathodes and also to operate in continuous mode. Keywords: Microbial electrosynthesis, CO2 reduction, Gas diffusion cathode, Flow-through biocathode, Biocathode, Autotrophic Bioproduction.

Kengo Sasaki, Daisuke Sasaki, Yota Tsuge et al.

Biotechnology for Biofuels • 2021

Abstract Background It is desirable to improve the anaerobic digestion processes of recalcitrant materials, such as cellulose. Enhancement of methane (CH 4 ) production from organic molecules was previously accomplished through coupling a bioelectrochemical system (BES); however, scaling-up BES-based production is difficult. Here, we developed a two-stage process consisting of a BES using low-cost and low-reactive carbon sheets as the cathode and anode, and a fixed film reactor (FFR) containing conductive material, i.e., carbon fiber textiles (CFTs) (:BES → FFR). By controlling the cathodic current at 2.7 μA/cm 2 without abiotic H 2 production, the three-electrode BES system was operated to mimic a microbial electrolysis cell. Results The thermophilic BES (inlet pH: 6.1) and FFR (inlet pH: 7.5) were operated using hydraulic retention times (HRTs) of 2.5 and 4.2 days, respectively, corresponding to a cellulose load of 3555.6 mg-carbon (C)/(L day). The BES → FFR process achieved a higher CH 4 yield (37.5%) with 52.8 vol% CH 4 in the product gas compared to the non-bioelectrochemical system (NBES) → FFR process, which showed a CH 4 yield of 22.1% with 46.8 vol% CH 4 . The CH 4 production rate (67.5 mM/day) obtained with the BER → FFR process was much higher than that obtained using electrochemical methanogenesis (0.27 mM/day). Application of the electrochemical system or CFTs improved the yields of CH 4 with the NBES → FFR or BES → non-fixed film reactor process, respectively. Meta 16S rRNA sequencing revealed that putative cellulolytic bacteria (identified as Clostridium species) were present in the BES and NBES, and followed (BES→ and NBES→) FFR. Notably, H 2 -consuming methanogens, Methanobacterium sp. and Methanosarcina sp., showed increased relative abundances in the suspended fraction and attached fraction of (BES→) FFR, respectively, compared to that of (NBES→) FFR, although these methanogens were observed at trace levels in the BES and NBES. Conclusions These results indicate that bioelectrochemical preprocessing at a low current effectively induces interspecies H 2 transfer in the FFR with conductive material. Sufficient electrochemical preprocessing was observed using a relatively short HRT. This type of two-stage process, BES → FFR, is useful for stabilization and improvement of the biogas (CH 4 ) production from cellulosic material, and our results imply that the two-stage system developed here may be useful with other recalcitrant materials.

Diya Novarina, Eko Swistoro, M. Firdaus et al.

PENDIPA Journal of Science Education • 2018

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.

Shujie Fan, M. Mahmoud, Biao Wen et al.

BioResources • 2018

The bioelectric activity of two lab scale microbial fuel cell (MFC) designs, MFCI (1,500 cm3) and MFCII (12,000 cm3) were examined using old corrugated containerboard (OCC) discharge for simultaneous effective treatment with greater power production. The decrease of MFC internal resistance (MFC-Rin) resulted in increased generated power output. The different parameters used in MFC included electrode conducting area (ECA), cathodic redox solution (CRS), MFC volume capacity, and MFCs connections. The generated current densities (CD) and power densities output (PD) at variables of external resistances (Rex) that ranged from 10 Ω to 20,000 Ω were calculated to estimate the MFC-Rin. In MFCI, using potassium ferri-cyanide as CRS, the change of ECA from 16 cm2 to 64 cm2 decreased the MFCI-Rin from 130 Ω to 110 Ω, and it was further decreased to 65 Ω when manganese dioxide was used as the CRS. Using Rex 100 Ω, MFCII exhibited lower Rin 18.46%, enhanced voltage 37.5%, and greater chemical oxygen demand removal 4.77% compared with MFCI. Series and parallel connections between four MFCI increased the generated PD by 286% and 258%, respectively, compared with that obtained by single MFCI.

K R S Pamintuan, J A A Clomera, K V Garcia et al.

IOP Conference Series: Earth and Environmental Science • 2018

Plant-microbial fuel cells (PMFCs) are a sub-branch of a class of promising bioelectrochemical systems which are capable of simultaneously supplying biomass and renewable energy from photosynthesis and root exudation. In this study, the possibility of power amplification through stacking was tested. Ipomoea aquatica and Pistia stratiotes were used as model plants in this study because their biomass is valued as food for humans and livestock, respectively. In a brief 7-day experiment, maximum power densities of 6.35 mW / m2 for I. aquatica and 3.54 mW/m2 for P. stratiotes were obtained from aquatic PMFC assemblies. No significant difference in voltage was observed between the two plants, although the current and power output of I. aquatica were significantly higher than that of P. stratiotes. Connecting three cells in series resulted to three times higher voltage but the same current, and connecting three cells in parallel resulted to three times higher current but the same voltage for both plants. Power was also amplified by stacking. There is no significant difference in the power produced by the cells connected in series or parallel. Power density remained constant due to the increase in surface area of electrodes used upon stacking. These results are consistent with the rules of electric circuits and would become a valuable tool in the computational design of larger systems with numerous cells that can supply a large part of our electricity demands. For future studies, assemblies with more cells are recommended to establish the upper limit of the validity of the series/parallel models and can be tested with other plants.

G. Zhu, Shan Huang, Yongze Lu et al.

Environmental Technology • 2019

ABSTRACT A multi-anode microbial fuel cell (MA-MFC) was developed to investigate simultaneous nitrification and denitrification (SND) in the bio-cathode. As the chemical oxygen demand to nitrogen (COD/N) ratio of the cathode was increased from 0 to 4.5, the electricity-producing quantity ranged between 498 and 543 C and the attained total nitrogen (TN) removal rate reached 12.07 g TN·m−3·d−1, resulting in a TN removal efficiency of 78.8% under the target COD/N ratio of 3.5. The removal of pollutants in series and parallel, open-circuit and closed-circuit were compared, respectively. The removal rates of TN, , and cathode and anode COD were all higher in the parallel connection configuration than in the series configuration. In parallel connection, the TN removal rate reached 14.4 g TN·m−3·d−1, which was 1.9 times that in series connection. Compared with the open-circuit system, the removal rate of TN in the closed-circuit system was improved by 17.8%, which could be ascribed to electrochemical denitrification. The results of high-throughput sequencing confirmed and clarified the presence of autotrophic denitrification and heterotrophic denitrification, including aerobic denitrification, when the MA-MFC had been operated for 18 months. GRAPHICAL ABSTRACT

K. Pamintuan, Arnie Jantzen G. Ancheta, S. Robles

E3S Web of Conferences • 2020

Plant-Microbial Fuel Cells (PMFCs) are an emerging type of renewable energy that generates an electric current through the consumption of rhizodeposits by exoelectrogenic bacteria that lives in the rhizosphere of the plant. Since the plant is not harmed by the energy-harvesting process, PMFC technology has the potential to simultaneously produce food (biomass) and generate electricity. As of now, power densities of PMFCs have remained low and commercialization is not yet possible. To achieve higher power densities, the stacking behaviour of PMFCs needs to be studied. In this study, several cells growing Ocimum basilicum (basil) and Origanum vulgare (oregano) were constructed and evaluated. Upon stacking, it was shown that the constructed PMFCs did indeed behave like batteries, where the voltage of cells connected in series are additive, and that the voltage of cells connected in parallel are constant. The actual values of voltage of stacked cells are similar to the expected value (α=0.05). Cumulative stacking tests revealed that there is no apparent loss in voltage upon stacking up to 9 cells growing O. basilicum. Further computation of power and power densities have proven that stacking is a viable method of amplifying electricity generation in PMFCs, as both increased with increasing number of cells connected in series.

M. Halim, Md. Owaleur Rahman, I. Eti et al.

Energy Sources, Part A: Recovery, Utilization, and Environmental Effects • 2020

ABSTRACT The present study examined optimized anodic electrode materials microbial fuel cells (MFCs) with Jashore Municipal Wastewater (JMW) as substrate in series and parallel connections. Three anodic materials, Iron plate (Fe), Carbon felt (CF), and Graphite rod (GR), were used to get green energy from waste biomass in microbial fuel cells. The output voltage, current, and power density of MFC were measured to investigate the preeminent anodic electrode material. The optimized anodic electrode material was Fe owing to high voltage generation followed by CF and GR. Results further indicated that the output voltage increased, but current density, as well as power density, decreased in series connection due to the increase of internal resistance compared to parallel at Fe-Cu combination. The maximum voltage, current density, and power density in series connection were 2238 mV, 79.98 mA/m2, and 108.850 mW⁄m2, respectively. On the other hand, in parallel connection, those values were 793 mV, 248.272 mA/m2, and 115.943 mW⁄m2, respectively. Most small electrical devices need high currents rather than high voltage imply parallel connections are preferred in this regard. Moreover, Fe-Cu combination is better to remove (87%) organic matter regarding COD removal efficiency from wastewater of MFCs.

Kumar Sonu, Z. Syed, M. Sogani

International Journal of Environmental Studies • 2020

ABSTRACT In this work the energy recovery in microbial fuel cell was studied by electrically stacking its three individual units into series and parallel arrangements. The power output was higher in parallel stacking by 2.07 and 14.77 times than series and individual units respectively. The rate of degradation of dye wastewater was in order of individual Microbial Fuel Cell (MFC) < series stack < parallel stack. The corn cob biochar was used as an additive in the MFC to improve the efficiency of the individual MFC unit. The addition of 0.5 g corn cob biochar enhanced the power output to 38.6 mW/m2 from 0.47 mW/m2 in the MFC individual unit without the biochar additive. The simultaneous COD reduction, TDS reduction and decolourisation of dye wastewater achieved are 82.14%, 68% and 74.8% respectively. The current work demonstrates that the dose of biochar and parallel stacking are a framework to achieve enhanced dye removal and bioenergy recovery via microbial fuel cell.

S. Mehrotra, N. K. Singh, Anusha Vempaty et al.

Environmental Technology • 2022

ABSTRACT A bioelectrochemical reactor is an assembly, which facilitates energy generation and resource recovery using electrochemically active microorganisms. To maximise energy production from wastewater in this bioreactor system special design is required. Therefore, in the present study, continuous flow auto dripping bioelectrochemical reactors (AutoDriBERs) were developed as a single and multi-electrode assembly for urine treatment. Further, their performance was assessed by connecting reactors in series and parallel arrangements. AutoDriBER configured in series connection showed the highest 93.64 ± 1.57% chemical oxygen demand removal rate with the 1.38 ± 0.64 V voltage and 2.54 W m−3 polarisation power density. The optimum flow rate for maximum voltage production was tested with various models i.e. the linear, exponential, Sweibull-1, and Sweibull-2 models to confirm voltage prediction and its validity. The Linear and exponential models were found best fitted for voltage production with R2 value of 0.999. These findings infer a novel approach toward optimisation of the complex, inexpensive and self-sufficient design for electricity generation from energy-rich urine wastewater in rural areas. GRAPHICAL ABSTRACT

Gabriela Marcano, Colleen Josephson, P. Pannuto

2022 IEEE International Symposium on Circuits and Systems (ISCAS) • 2022

This paper discusses experiments on soil-based microbial fuel cells (MFCs) as energy scavenging sources. We explain the mechanism of operation for MFCs, perform controlled laboratory experiments of MFCs, and deploy a small-scale insitu pilot in an active farm. We find that traditional energy harvester ICs draw power too aggressively, which reduces overall energy capture. We show that isolated MFCs can be combined in series or parallel to improve the voltage or current output of the harvesting source. Lastly, we observe that under a real-world, drip-irrigated agricultural setting, MFC output is appreciably lower, but consistent at 0.5-2 microwatts.

K. Pamintuan, Hazelle Jae Abanilla, Luis Alfonso Dañez

2023 International Conference on Power and Renewable Energy Engineering (PREE) • 2023

Plant microbial fuel cells (PMFCs) are bio-electrochemical systems that show promise in electricity generation via the plant-microorganism reactions occurring at the rhizosphere of the plant roots. The study aims to determine the scalability of this technology by the stacking of fifteen (15) 3D-printed hexagonal multi-anode/cathode cells growing water hyacinth (Pontederia crassipes); the cells are stacked to determine the extent of power amplification when multiple connections and configurations are employed. In a 30-day experiment, a branched series pattern generated the highest power (1.52 µW) and power density (5.34 µW/m2) among all arrangements. Voltage losses were more prevalent in cells stacked in series than in parallel. Power densities were much higher for cells stacked in series. Still, stacking cells in both series and parallel improved the power-generating capacity of PMFCs compared to an individual cell. Combining series and parallel connections in a clumped stack resulted in a much lower power density than the value generated by an individual cell. Differences were observed when cells were rotated to change the orientation of the connections, as switching from series to parallel caused a consistent deterioration in performance. Polarization tests revealed this clustered pattern to have the highest internal resistance, contributing to internal losses and decreased exerted power. It is hoped that the results of this study will have a significant contribution to the efforts of optimizing PMFC performance, particularly by stacking.

Yumi Kimura, Gabrielle Angela Magdaluyo, K. Pamintuan

2023 International Conference on Power and Renewable Energy Engineering (PREE) • 2023

Plant microbial fuel cell (PMFC), a green energy source, is a bioelectrochemical system that converts rhizodeposits to bioelectricity. This paper investigated the stacking efficiency of PMFCs with USB connectivity using 3D-printed conductive PLA electrodes with Vigna radiata as the model plant. The stacking techniques successfully connected 16 PMFCs in pure and varying combinations of series and parallel. Stacking all cells in pure parallel obtained a maximum voltage of 98.4 mV. However, due to voltage reversal, cumulative stacking of PMFCs in pure series or parallel is inefficient and not an ideal strategy for scale-up. Further evaluation of the overall performance was done by stacking the cells in series-parallel and parallel-series configurations. The results revealed that stacking 6 (3P-S), 8 (4P-S), and 12 (4P-2S) cells in parallel-series correspondingly amplified the power and power densities of the system. Essentially, it was reported that stacking two sets of two parallel cells in series (2P-S) collected the highest power and power density of 0.42 µW and 13.76 µW/m2, respectively. Despite optimizing the power and power density, PMFC still faces a challenge in retaining the power and power density while connecting stacked cells. The scale-up potential of this system, the optimal power density of PMFCs could be improved by design optimization of electrodes and further analysis of the factors influencing the power generation capacity of this environmentally benign technology.

Muhammad Lutfan Aiman Zamri, S. Z. Makhtar, Mohamad Farhan Mohamad Sobri et al.

IOP Conference Series: Earth and Environmental Science • 2023

Microbial fuel cell (MFC) is an outstanding technology recently creating the headlines relating to energy and environment field that been discovered since the earlier 20th century. It has been furthered implemented for energy renewable through simultaneous bioremediation of wastes. MFC works by converting chemical energy store in the waste into electrical energy with the help of selected microorganisms. Regarding to this, the principle of bioremediation was applied using MFC as the renewable energy where the microorganisms consume the substrate thus generating electrical energy. Many studies done by researches are mostly focusing on MFC utilizing waste and measuring the power generation on different type of MFC but lack of studies on the effect of series and parallel circuit in MFC setup and how does it differentiate the outcome of the studies. This paper reviews the history, working principle, design of MFC, classification of different substrates and its power output and the effect of series and parallel circuit of MFC setup for simultaneous bioremediation and energy recovery.

Alexiane Godain, Timothy M. Vogel, Jean-Michel Monnier et al.

Microorganisms • 2023

MFCs represent a promising sustainable biotechnology that enables the direct conversion of organic matter from wastewater into electricity using bacterial biofilms as biocatalysts. A crucial aspect of MFCs is how electroactive bacteria (EAB) behave and their associated mechanisms during extracellular electron transfer to the anode. A critical phase in the MFC start-up process is the initial colonization of the anode by EAB. Two MFCs were operated with an external resistance of 1000 ohms, one with an applied electrical voltage of 500 mV during the initial four days of biofilm formation and the other without any additional applied voltage. After stabilization of electricity production, total DNA and protein were extracted and sequenced from both setups. The combined metaproteomic/metagenomic analysis revealed that the application of voltage during the colonization step predominantly increased direct electron transfer via cytochrome c, mediated primarily by Geobacter sp. Conversely, the absence of applied voltage during colonization resulted in a broader diversity of bacteria, including Pseudomonas and Aeromonas, which participated in electricity production via mediated electron transfer involving flavin family members.

Eduardo Leiva, Enzo Leiva-Aravena, Ignacio Vargas

Water • 2016

Acid mine drainage (AMD) is a complex environmental problem, which has adverse effects on surface and ground waters due to low pH, high toxic metals, and dissolved salts. New bioremediation approach based on microbial fuel cells (MFC) can be a novel and sustainable alternative for AMD treatment. We studied the potential of MFC for acidic synthetic water treatment through pH neutralization in batch-mode and continuous-flow operation. We observed a marked pH increase, from ~3.7 to ~7.9 under batch conditions and to ~5.8 under continuous-flow operation. Likewise, batch reactors (non-MFC) inoculated with different MFC-enriched biofilms showed a very similar pH increase, suggesting that the neutralization observed for batch operation was due to a synergistic influence of these communities. These preliminary results support the idea of using MFC technologies for AMD remediation, which could help to reduce costs associated with conventional technologies. Advances in this configuration could even be extrapolated to the recovery of heavy metals by precipitation or adsorption processes due to the acid neutralization.

Anna Sekrecka-Belniak, Renata Toczyłowska-Mamińska

Energies • 2018

Fungi are among the microorganisms able to generate electricity as a result of their metabolic processes. Throughout the last several years, a large number of papers on various microorganisms for current production in microbial fuel cells (MFCs) have been published; however, fungi still lack sufficient evaluation in this regard. In this review, we focus on fungi, paying special attention to their potential applicability to MFCs. Fungi used as anodic or cathodic catalysts, in different reactor configurations, with or without the addition of an exogenous mediator, are described. Contrary to bacteria, in which the mechanism of electron transfer is pretty well known, the mechanism of electron transfer in fungi-based MFCs has not been studied intensively. Thus, here we describe the main findings, which can be used as the starting point for future investigations. We show that fungi have the potential to act as electrogens or cathode catalysts, but MFCs based on bacteria–fungus interactions are especially interesting. The review presents the current state-of-the-art in the field of MFC systems exploiting fungi.