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In this study, microbial fuel cells deploying heterogeneous ion exchange membranes were assessed. The behavior of the cells as a function of the membrane applied was evaluated in terms of maximal current density, electron recovery efficiency and energy production rate (up to 427.5 mA, 47.7 % and 660 J m

Hydrophobic ionic liquids (IL) may offer a special electrolyte in the form of supported ionic liquid membranes (SILM) for microbial fuel cells (MFC) due to their advantageous mass transfer characteristics. In this work, the proton and ion transfer properties of SILMs made with IL containing imidazolium cation and [PF6]− and [NTf2]− anions were studied and compared to Nafion. It resulted that both ILs show better proton mass transfer and diffusion coefficient than Nafion. The data implied the presence of water microclusters permeating through [hmim][PF6]-SILM to assist the proton transfer. This mechanism could not be assumed in the case of [NTf2]− containing IL. Ion transport numbers of K+, Na+, and H+ showed that the IL with [PF6]− anion could be beneficial in terms of reducing ion transfer losses in MFCs. Moreover, the conductivity of [bmim][PF6]-SILM at low electrolyte concentration (such as in MFCs) was comparable to Nafion.

In this study, mixed culture bioelectrochemical systems were operated with various membrane separators: one prepared with 1-Butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) ionic liquid and another one called Nafion, used as reference for comparative evaluation. In the course of experiments, the primary objective was to reveal the influence of membranes-type on microbial fuel cell (MFC) behavior by applying a range of characterization methods. These included cell polarization measurements, monitoring of dehydrogenase enzyme activity and cyclic voltammetry for the analysis of anode biofilm properties and related electron transfer mechanism. Additionally, MFC performances for both membranes were assessed based on Coulombic efficiency as well as substrate (acetate) concentration dependency of energy yields. As a result, it was demonstrated that the ionic liquid-containing membrane could be suitable to compete with Nafion and appears as a candidate to be further investigated for microbial electrochemical applications.

Significant advances in the design of bioelectrochemical systems (BES) have promoted these applications to be seen as contemporary biotechnological platforms. However, notable issues in system architecture are still to be addressed and overcome, in particular concerning the membrane separators, which rely widely on polymers. These architectural components play a key-role in facilitating the transport of ions (i.e. protons) between the (compartments containing the) electrodes and therefore, their properties substantially influence the overall BES performance. This article aims presenting an up-to-date survey on the important accomplishments and promising outlooks with polymer-based membranes (both porous/non-porous, charged/uncharged) applied in BES (first and foremost microbial fuel cells, MFCs) that could drive this technology towards enhanced efficiency. Because of the interdisciplinary concept of BES, it attracts attention from scientists and engineers involved in environmental biotechnology, microbial electrochemistry and applied material sciences and as a result, this review paper would target the audience of these fields with particular interest on the progress with membrane separators fabricated with various polymeric materials.

In this work, bioaugmentation strategy was tested to enhance electricity production efficiency from municipal waste liquor feedstock in microbial fuel cells (MFC). During the experiments, MFCs inoculated with a mixed anaerobic consortium were enriched by several pure, electro-active bacterial cultures (such as Propionibacterium freudenreichii, Cupriavidus basilensis and Lactococcus lactis) and behaviours were assessed kinetically. It turned out that energy yield could be enhanced mainly at high substrate loadings. Furthermore, energy production and COD removal rate showed an optimum and could be characterized by a saturation range within the applied COD loadings, which could be elucidated applying the Monod-model for describing intracellular losses. Polarization measurements showed the positive effect of bioaugmentation also on extracellular losses. The data indicated a successful augmentation process for enhancing MFC efficiency, which was utmost in case of augmentation strain of Propionibacterium freudenreichii.

The scope of the current review is to discuss and evaluate the role of the external electrical load/resistor (EEL) on the overall behavior and functional properties of microbial fuel cells (MFCs). In this work, a comprehensive analysis is made by considering various levels of MFC architecture, such as electric and energy harvesting efficiency, anode electrode potential shifts, electro-active biofilm formation, cell metabolism and extracellular electron transfer mechanisms, as a function of the EEL and its control strategies. It is outlined that taking the regulation of EEL into account at MFC optimization is highly beneficial, and in order to support this step, in this review, a variety of guidelines are collected and analyzed.

In this study, the dependency of energy recovery on separator characteristics applied in microbial fuel cells (MFCs) was sought by testing an emerging class of membranes (supported ionic liquid membranes (SILMs), prepared with [hmim][PF 6 ] and [bmim][NTf 2 ] ionic liquids) comparatively with well-known proton exchange (Nafion N115) and microfiltration (PVDF) counterparts. Crucial membrane features such as O 2 and substrate (acetate as the sole carbon source) crossovers were assessed and as a result, mass transfer as well as diffusivity coefficients of these compounds ( k O , k A , D O , D A , respectively) were determined. The experiments showed that SILM-operated MFCs could work in a reliable way and among them, the [bmim][NTf 2 ]-based one produced higher specific energy yield ( Y S = 9.78 kJ g −1 CODin m −2 ) than the Nafion-MFC ( Y S = 8.25 kJ g −1 CODin m −2 ) used as an important reference. This outcome was found to be associated with the membrane-cross oxygen shuttle properties of the membranes ( k O = 1.25 cm s −1 and 1.31 cm s −1 , respectively). As for the two SILMs, significant differences in terms of the energy yield, mass transfer and diffusion coefficients were noted, however, it has appeared from cell polarization measurements that the internal resistances of the SILM-MFCs were nearly the same. The evaluation of the SILM-operated MFCs’ power production was complemented by measuring the dielectric traits of ionic liquids that can be related with the ion conductivity of these materials. It turned out that the [hmim][PF 6 ] IL had an order of magnitude lower ionic conductivity.

Excess consumption of energy by humans is compounded by environmental pollution, the greenhouse effect and climate change impacts. Current developments in the use of algae for bioenergy production offer several advantages. Algal biomass is hence considered a new bio-material which holds the promise to fulfil the rising demand for energy. Microalgae are used in effluents treatment, bioenergy production, high value added products synthesis and CO2 capture. This review summarizes the potential applications of algae in bioelectrochemically mediated oxidation reactions in fully biotic microbial fuel cells for power generation and removal of unwanted nutrients. In addition, this review highlights the recent developments directed towards developing different types of microalgae MFCs. The different process factors affecting the performance of microalgae MFC system and some technological bottlenecks are also addressed.

The start-up of microbial electrohydrogenesis cells (MECs) is a key-step to realize efficient biohydrogen generation and adequate, long-term operation. This review paper deals with the lessons and experiences reported on the most important aspects of H 2 producing MEC start-up. The comprehensive survey covers the assessment and discussion of the main influencing factors and methods (e.g. inocula selection, enrichment, acclimation, operating conditions and cell architecture) that assist the design of MECs. This work intends to be a helpful guide for the interested readers about the strategies employed to successfully establish microbial electrochemical cells for sustainable biohydrogen production.

The aim of this work was to study the inhibition and deactivation of commercial enzyme cocktail (Cellic® Htec2) in the presence of [bmim][Cl] ionic liquid employing model cellulosic substrate, carboxymethyl cellulose (CMC). It turned out from the experiments - relying on enzyme kinetics approach - that [bmim][Cl] could act as a competitive inhibitor. Furthermore, depending on the process conditions i.e. contact of enzyme solution with high concentration [bmim][Cl], severe biocatalyst inactivation should be also taken into account as a potential risk during the enzymatic cellulose hydrolysis even in as short process times as few minutes.

In this paper, the anaerobic treatment of a high organic-strength wastewater-type feedstock, referred as the liquid fraction of pressed municipal solid waste (LPW) was studied for energy recovery and organic matter removal. The processes investigated were (i) dark fermentation to produce biohydrogen, (ii) anaerobic digestion for biogas formation and (iii) microbial fuel cells for electrical energy generation. To find a feasible alternative for LPW treatment (meeting the two-fold aims given above), various one- as well as multi-stage processes were tested. The applications were evaluated based on their (i) COD removal efficiencies and (ii) specific energy gain. As a result, considering the former aspect, the single-stage processes could be ranked as: microbial fuel cell (92.4%)> anaerobic digestion (50.2%)> hydrogen fermentation (8.8%). From the latter standpoint, an order of hydrogen fermentation (2277 J g−1 CODremoved d−1)> anaerobic digestion (205 J g−1 CODremoved d−1)> microbial fuel cell (0.43 J g−1 CODremoved d−1) was attained. The assessment showed that combined, multi-step treatment was necessary to simultaneously achieve efficient organic matter removal and energy recovery from LPW. Therefore, a three-stage system (hydrogen fermentation-biomethanation-bioelectrochemical cell in sequence) was suggested. The different approaches were characterized via the estimation of COD balance, as well.

In the course of dark fermentative hydrogen production, a complex gaseous mixture with significant quantity of CO2 is formed. Hence, proper separation of H2 and CO2 is required for adequate utilization of hydrogen gas in fuel cell applications. Technological solutions for the removal of CO2 can be designed by using gas separation membranes. Nevertheless, contemporary systems should be concerned with the consecutive valorization of carbon dioxide, as well. In this review article, the membrane-based technologies aiming at the effective separation of CO2 and biohydrogen (bioH2) will be evaluated, along with concise discussion and perspectives of integrative schemes offering alternatives for the biologically-mediated (fermentative, bioelectrochemical and algal) conversion of carbon dioxide into value-added substances, such as methane, hydrocarbons, etc. With this analysis, the objective was to bring the most important aspects of membrane-assisted biohydrogen downstream technology under one cover and give insights to recent advancement and possible future research directions.

The use of liquid fraction of pressed municipal solid waste (LPW) for hydrogen production was evaluated via electrohydrogenesis in a single-chamber microbial electrolysis cell (MEC). The highest hydrogen production (0.38 ± 0.09 m3 m−3 d−1 and 30.94 ± 7.03 mmol g−1 CODadded) was achieved at an applied voltage of 3.0 V and pH 5.5, increasing by 2.17-fold than those done at the same voltage without pH adjustment (pH 7.0). Electrohydrogenesis was accomplished by anodic oxidation of fermentative end-products (i.e. acetate, as well as propionate and butyrate after their acetification), with overall hydrogen recovery of 49.5 ± 11.3% of CODadded. These results affirm for the first time that electrohydrogenesis can be a noteworthy alternative for hydrogen recovery from LPW and simultaneous organics removal. Electrohydrogenesis efficiency of this system has potential to improve provided that electron recycling, electromethanogenesis and deposition of non-conductive aggregates on cathode surface, etc. are effectively controlled.

To increase the efficiency of microbial fuel cells (MFCs), the separator (which is mostly a membrane) placed between the electrodes or their compartments is considered of high importance besides several other biotic and abiotic factors (e.g. configuration, mode of operation, types of inoculum and substrate). Nafion-based proton exchange membranes (PEMs) are the most widespread, although these materials are often criticized on various technological and economical grounds. Therefore, to find alternatives of Nafion, the synthesis, development and testing of novel/commercialized membrane separators with enhanced characteristics have been hot topics. In this study, the goals were to assess the membrane-installed MFCs in a retrospective manner and reveal the trends, the applied practices, frequent setups, etc. via Bayesian classification and frequent itemset mining algorithms. Thereafter, a separate discussion was devoted to examine the current standing of research related to major membrane groups used in MFCs and evaluate in accordance with the big picture how the various systems behave in comparison with each other, especially compared to those applying Nafion PEM. It was concluded that some membrane types seem to be competitive to Nafion, however, the standardization of the experiments would drive the more unambiguous comparison of studies.

The performance and behavior of microbial fuel cells (MFCs) are influenced by among others the external load (Rext). In this study, the anode-surface biofilm formation in MFCs operated under different Rext selection/tracking-strategies was assessed. MFCs were characterized by electrochemical (voltage/current generation, polarization tests, EIS), molecular biological (microbial consortium analysis) and bioinformatics (principal component analysis) tools. The results indicated that the MFC with dynamic Rext adjustment (as a function of the actual MFC internal resistance) achieved notably higher performance but relatively lower operational stability, mainly due to the acidification of the biofilm. The opposite (lower performance, increased stability) could be observed with the static (low or high) Rext application (or OCV) strategies, where adaptive microbial processes were assumed. These possible adaptation phenomena were outlined by a theoretical framework and the significant impact of Rext on the anode colonization process and energy recovery with MFCs was concluded.

In this work, two commercialized anion-exchange membranes (AEMs), AMI-7001 and AF49R27, were applied in microbial electrolysis cells (MECs) and compared with a novel AEM (PSEBS CM DBC, functionalized with 1,4-diazabicyclo[2.2.2]octane) to produce biohydrogen. The evaluation regarding the effect of using different AEMs was carried out using simple (acetate) and complex (mixture of acetate, butyrate and propionate to mimic dark fermentation effluent) substrates. The MECs equipped with various AEMs were assessed based on their electrochemical efficiencies, H2 generation capacities and the composition of anodic biofilm communities. pH imbalances, ionic losses and cathodic overpotentials were taken into consideration together with changes to substantial AEM properties (particularly ion-exchange capacity, ionic conductivity, area- and specific resistances) before and after AEMs were applied in the process to describe their potential impact on the behavior of MECs. It was concluded that the MECs which employed the PSEBS CM DBC membrane provided the highest H2 yield and lowest internal losses compared to the two other separators. Therefore, it has the potential to improve MECs.

In this work, two polymeric membrane separators (a proton exchange membrane (PEM), Nafion, and an anion-exchange membrane (AEM), 1,4-diazabicyclo[2.2.2]octane (DABCO)-functionalized PSEBS) deployed in microbial fuel cells (MFCs) are comparatively assessed. The performances of MFCs according to membrane type were evaluated by biological and electrochemical techniques, employing metagenomics, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). It was found that the anodic biofilms of MFCs, irrespective of the type of membrane, were dominated by Geobacter sulfurreducens (37 and 50% for AEM-MFC and PEM-MFC, respectively), a well-known electrochemically active species. Furthermore, the AEM-MFC reflected a significantly lower internal resistance (145 Ω) compared to PEM-MFC (339 Ω) and produced higher maximal current densities and energy yields at all substrate (acetate) concentrations, as follows: 400 vs. 285 mA m−2 (5 mM acetate); 360 vs. 320 mA m−2 (10 mM acetate), 305 vs. 235 mA m−2 (15 mM acetate) and 238 vs.132 kJ m−2 gCOD (5 mM acetate), 161 vs. 128 kJ m−2 gCOD (10 mM acetate), 114 vs. 59 kJ m−2 gCOD (15 mM acetate) respectively. The CV measurements implied diffusion limitations in the MFCs, which were supported by EIS. In addition, the PEM and AEM characterizations revealed that in both cases, the ion exchange capacity, ionic conductivity and oxygen mass transport features were altered considerably over the 39 days during which the MFCs operated.

Microbial fuel cells (MFCs) are recognized as promising applications to produce bioelectricity by utilizing various waste materials. In this study, dual-chamber microbial fuel cells were employed for energy valorization of an untested substrate, the liquid fraction of pressed municipal solid waste (LPW). This by-product is potentially applicable as a substrate in MFCs because of its high organic matter content. In the course of the experiments, the anodic biofilm response and energy production efficiency have been investigated by experimental design approach, taking substrate and fresh inoculum – mesophilic anaerobic sludge (MAS) – addition into account as factors. It was observed that reinoculation could result in a negative effect on the energy production, especially at low substrate (LPW) dosing levels. However, when the LPW to fresh MAS ratio in the anode chamber exceeded a particular value, the biofilm-associated electrical utilization dominated against the degradation in the bulk phase. Furthermore, the results indicated that the highest energy yields (8–9 J g −1 ΔCOD d −1 ) could be attained at the lowest input COD concentrations. The maximal and average COD removal efficiencies were 94% and 87%, respectively, which indicate the excellent biodegradability of LPW. As for COD removal rate, 1.2–1.9 kg COD m −3 d −1 could be reached.

A novel substrate (obtained from biofraction of municipal solid waste by pressing and called LPW) rich in organic substances was used in three anaerobic degradation processes (biogas, biohydrogen fermentation and microbial fuel cells) to comparatively assess their feasibility for energy recovery. It has turned out that all the processes have successfully degraded that substrate and produced energy carriers (methane and hydrogen) as well as bioelectricity. The maximum energy yields (J g−1 CODremoved day−1) and associated COD removal capacities were 255, 200, 2.8 and 46, 52 and 72 % for biohydrogen, biogas and microbial fuel cell, respectively. The outcomes suggested the prominence of biohydrogen process for simultaneous waste treatment and energy recovery from LPW under the test conditions ensured.

The purpose of this research was to improve microbial fuel cell (MFC) performance - treating landfill-derived waste liquor - by applying effluents of various biogas fermenters as inocula. It turned out that the differences of initial microbial community profiles notably influenced the efficiency of MFCs. In fact, the adaptation time (during 3 weeks of operation) has varied significantly, depending on the source of inoculum and accordingly, the obtainable cumulative energy yields were also greatly affected (65% enhancement in case of municipal wastewater sludge inoculum compared to sugar factory waste sludge inoculum). Hence, it could be concluded that the capacity of MFCs to utilize the complex feedstock was heavily dependent on biological factors such as the origin/history of inoculum, the microbial composition as well as proper acclimation period. Therefore, these parameters should be of primary concerns for adequate process design to efficiently generate electricity with microbial fuel cells.

Membrane separators are key elements of microbial fuel cells (MFCs), especially of those constructed in a dual-chamber configuration. Until now, membranes made of Nafion have been applied the most widely to set-up MFCs. However, there is a broader agreement in the literature that Nafion is expensive and in many cases, does not meet the actual (mainly mass transfer-specific) requirements demanded by the process and users. Driven by these issues, there has been notable progress in the development of alternative materials for membrane fabrication, among which those relying on the deployment of ionic liquids are emerging. In this review, the background of and recent advances in ionic liquid-containing separators, particularly supported ionic liquid membranes (SILMs), designed for MFC applications are addressed and evaluated. After an assessment of the basic criteria to be fulfilled by membranes in MFCs, experiences with SILMs will be outlined, along with important aspects of transport processes. Finally, a comparison with the literature is presented to elaborate on how MFCs installed with SILM perform relative to similar systems assembled with other, e.g., Nafion, membranes.

In this work, the performance of dual-chamber microbial fuel cells (MFCs) constructed either with commonly used Nafion ® proton exchange membrane or supported ionic liquid membranes (SILMs) was assessed. The behavior of MFCs was followed and analyzed by taking the polarization curves and besides, their efficiency was characterized by measuring the electricity generation using various substrates such as acetate and glucose. By using the SILMs containing either [C 6 mim][PF 6 ] or [Bmim][NTf 2 ] ionic liquids, the energy production of these MFCs from glucose was comparable to that obtained with the MFC employing polymeric Nafion ® and the same substrate. Furthermore, the MFC operated with [Bmim][NTf 2 ]-based SILM demonstrated higher energy yield in case of low acetate loading (80.1 J g −1 COD in m −2 h −1 ) than the one with the polymeric Nafion ® N115 (59 J g −1 COD in m −2 h −1 ). Significant difference was observed between the two SILM-MFCs, however, the characteristics of the system was similar based on the cell polarization measurements. The results suggest that membrane-engineering applying ionic liquids can be an interesting subject field for bioelectrochemical system research.

In this paper, the anaerobic treatment of a high organic-strength wastewater-type feedstock, referred as the liquid fraction of pressed municipal solid waste (LPW) was studied for energy recovery and organic matter removal. The processes investigated were (i) dark fermentation to produce biohydrogen, (ii) anaerobic digestion for biogas formation and (iii) microbial fuel cells for electrical energy generation. To find a feasible alternative for LPW treatment (meeting the two-fold aims given above), various one- as well as multi-stage processes were tested. The applications were evaluated based on their (i) COD removal efficiencies and (ii) specific energy gain. As a result, considering the former aspect, the single-stage processes could be ranked as: microbial fuel cell (92.4%)anaerobic digestion (50.2%)hydrogen fermentation (8.8%). From the latter standpoint, an order of hydrogen fermentation (2277 J g

In this project, the production of biohydrogen, as a renewable and sustainable energy source was studied. Biohydrogen was manufactured by using E. coli strain in a batch dark fermentative process integrated with membrane gas separation. Two different methods were applied: Firstly, the amount of the produced gas and component concentrations were measured, but CO2 and H2 gases were not separated. In the second experiment CO2 was removed from the gas mixture via chemical sorption (reacting with NaOH). Both methods use continuous product removal in order to enhance the biohydrogen formation. In addition, process modeling was carried out with a simulation software (SuperPro Designer, Intelligen Inc.) so that experimental and computational results could be compared. CO2 and H2 flow rates and fluxes were calculated on the basis of the membrane permeation data obtained by using pure gases and silicone (PDMS) hollow-fiber membrane module (PermSelect – MedArray Inc.).