Search Results (18)

The unique fuel characteristics of butanol and the possibility of its microbial production make it one of the most desirable environmentally friendly substitutes for petroleum fuels. However, the highly toxic nature of 1-butanol to the bacterial strains makes it unprofitable for commercial production. By comparison, 2-butanol has similar fuel qualities, and despite the difficulties in its microbial synthesis, it holds promise because it may be less toxic. This paper is the first comprehensive study to compare bacterial tolerance to different butanol isomers by examining the growth of 31 bacterial strains under 1-butanol and 2-butanol stress conditions. The presented results reveal that all tested strains showed a higher tolerance to 2-butanol than to 1-butanol at each solvent concentration (1%, 2%, and 3% v/v). Moreover, with an increased solvent concentration, bacterial cells lost their resistance to 1-butanol more rapidly than to 2-butanol. A comparison of the transcriptome profiles of the reference strains Bacillus subtilis ATCC 168 and E. coli ATCC 25922 disclosed a specific response to butanol stress. Most notably, in the presence of 2-butanol E. coli ATCC 25922 showed a reduced expression of genes for chaperones, efflux pumps, and the flagellar apparatus, as well as an enhancement of membrane and electron transport. B. subtilis, with 2-butanol, did not perform emergency sporulation or escape, as some global transcriptional stress response regulators were downregulated. The overexpression of ribosomal RNAs, pyrimidine biosynthesis genes, and DNA- and RNA-binding proteins such as pcrA and tnpB was crucial in the response. Full article

Microbial fuel cells and their related microfluidic systems have emerged as promising greener energy alternatives for the exploitation of avenues related to combined power and wastewater treatment operations. Moreover, the potential for their application in biosensing technology is large. However, while the fundamental principles of science that govern the design and operation of microbial fuel cells (MFCs) and microfluidic microbial fuel cells (MMFCs) are similar to those found in colloid science, the literature shows that current research lacks sufficient reference to the electrostatic and electrokinetic aspects, focusing mostly on aspects related to the architecture, design, anodes, microbial growth and metabolism, and electron transfer mechanisms. In this regard, research is yet to consider MFCs and MMFCs in the context of electrostatic and electrokinetic aspects. In this extensive review, we show, for the first time, the interrelationship of MFCs and MMFCs with electric double layer theory. Consequently, we show how the analytical solution to the mean field Poisson–Boltzmann theory relates to these systems. Moreover, we show the interrelationship between MFC and MMFCs’ performance and the electric double layer and the associated electrostatic and electrokinetic phenomena. This extensive review will likely motivate research in this direction. Full article

A microbial fuel cell (MFC) is a bioelectrochemical system that can be employed for the generation of electrical energy under microbial activity during wastewater treatment practices. The optimization of electrode spacing is perhaps key to enhancing the performance of an MFC. In this study, electrode spacing was evaluated to determine its effect on the performance of MFCs. The experimental work was conducted utilizing batch digesters with electrode spacings of 2.0 cm, 4.0 cm, 6.0 cm, and 8.0 cm. The results demonstrate that the performance of the MFC improved when the electrode spacing increased from 2.0 to 6.0 cm. However, the efficiency decreased after 6.0 cm. The digester with an electrode spacing of 6.0 cm enhanced the efficiency of the MFC, which led to smaller internal resistance and greater biogas production of 662.4 mL/g VS_fed. The electrochemical efficiency analysis demonstrated higher coulombic efficiency (68.7%) and electrical conductivity (177.9 µS/cm) for the 6.0 cm, which was evident from the enrichment of electrochemically active microorganisms. With regards to toxic contaminant removal, the same digester also performed well, revealing removals of over 83% for chemical oxygen demand (COD), total solids (TS), total suspended solids (TSS), and volatile solids (VS). Therefore, these results indicate that electrode spacing is a factor affecting the performance of an MFC, with an electrode spacing of 6.0 cm revealing the greatest potential to maximize biogas generation and the degradability of wastewater biochemical matter. Full article

Wastewater has high potential as an energy source. Therefore, it is important to recover even the smallest part of this energy, e.g., in microbial fuel cells (MFCs). The obtained electricity production depends on the process rate of the electrodes. In MFC, the microorganisms are the catalyst, and the cathode is usually made of carbon material (e.g., with the addition of Pt). To increase the MFC efficiency (and reduce costs by reducing use of the noble metals), it is necessary to search the new cathode materials. In this work, the electricity production from yeast wastewater in membrane-less microbial fuel cells with Cu-Ag cathode was analyzed. In the first place, the measurements of the stationary potential of the electrodes (with Cu-Ag catalyst obtained by the electrochemical deposition technique) were performed. Because the cathode is constantly oxidized during the operation of ML-MFC, it was necessary to pre-oxidize the cathodes. Without pre-oxidation, there is a risk of changing the catalytic properties of the electrodes (along with the level of oxidation of the cathodes’ surface) throughout their operation in the ML-MFC. These measurements allowed to assess the oxidation activity of the Cu-Ag cathodes. Additionally, the influence of anodic charge on the catalytic activity of the Cu-Ag cathodes was measured. Next, the analysis of the electric energy production during the operation of the membrane-less microbial fuel cell (ML-MFC) fed by process yeast wastewater was performed. The highest parameters (the power of 6.38 mW and the cell voltage of 1.09 V) were obtained for a Cu-Ag catalyst with 5% of Ag, which was oxidized over 6 h, and after 3 anodic charges. This research proved that it is feasible to obtain the bio-electricity in the ML-MFC with Cu-Ag cathode (fed by yeast wastewater). Full article

Carbon nanofiber-decorated graphite rods are introduced as effective and low-cost anodes for industrial wastewater-driven microbial fuel cells. Carbon nanofiber deposition on the surface of the graphite rods could be performed by the electrospinning of polyacrylonitrile/N,N-Dimethylformamide solution using the rod as nanofiber collector, which was calcined under inert atmosphere. The experimental results indicated that at 10 min electrospinning time, the proposed graphite anode demonstrates very good performance compared to the commercial anodes. Typically, the generated power density from sugarcane industry wastewater-driven air cathode microbial fuel cells were 13 ± 0.3, 23 ± 0.7, 43 ± 1.3, and 185 ± 7.4 mW/m² using carbon paper, carbon felt, carbon cloth, and graphite rod coated by 10-min electrospinning time carbon nanofibers anodes, respectively. The distinct performance of the proposed anode came from creating 3D carbon nanofiber layer filled with the biocatalyst. Moreover, to annihilate the internal cell resistance, a membrane-less cell was assembled by utilizing a poly(vinylidene fluoride) electrospun nanofiber layer-coated cathode. This novel strategy inspired a highly hydrophobic layer on the cathode surface, preventing water leakage to avoid utilizing the membrane. However, in both anode and cathode modifications, the electrospinning time should be optimized. The best results were obtained at 5 and 10 min for the cathode and anode, respectively. Full article

The need for energy resources is growing all the time, which means that more fossil fuels are needed to provide them. People prefer to consume chicken as a source of protein, and this creates an abundance of waste. Thus, microbial fuel cells represent a new technological approach with the potential to generate electricity through the action of electrogenic bacteria toward chicken manure, while reducing the abundance of chicken manure. This study investigated the effect of different pretreatment (thermal, alkaline, and sonication pretreatment) of chicken manure to improve the performance of a membrane-less microbial fuel cell (ML-MFC). Statistical response surface methodology (RSM) through a central composite design (CCD) under a quadratic model was conducted for optimization of the ML-MFC performance focusing on the COD removal efficiency (R² = 0.8917), biomass (R² = 0.9101), and power density response (R² = 0.8794). The study demonstrated that the highest COD removal (80.68%), biomass (7.8539 mg/L), and power density (220 mW/m²) were obtained when the pretreatment conditions were 140 °C, 20 kHz, and pH 10. The polarization curve of the best condition of ML-MFC was plotted to classify the behavior of the ML-MFC. The kinetic growth of Bacillus subtillis (BS) showed that, in treated chicken manure, the specific growth rate µ = 0.20 h⁻¹ and doubling time Td = 3.43 h, whereas, in untreated chicken manure, µ = 0.11 h⁻¹ and Td = 6.08. Full article

In addition to disposal issues, the abundance of sludge and chicken manure has been a rising issue in Malaysia. Membrane-less microbial fuel cell (ML-MFC) technology can be considered as one of the potential solutions to the issues of disposal and electricity generation. However, there is still a lack of information on the performance of an ML-MFC powered by sludge and chicken manure. Hence, with this project, we studied the performance of an ML-MFC supplemented with sludge and chicken manure, and its operating parameters were optimized using response surface methodology (RSM) through central composite design (CCD). The optimum operating parameters were determined to be 35 °C, 75% moisture content, and an electrode distance of 3 cm. Correspondingly, the highest power density, COD removal efficiency, and biomass acquired through this study were 47.2064 mW/m², 98.0636%, and 19.6730 mg/L, respectively. The obtained COD values for dewatered sludge and chicken manure were 708 mg/L and 571 mg/L, respectively. COD values were utilized as a standard value for the substrate degradation by Bacillus subtilis in the ML-MFC. Through proximate analyses conducted by elemental analysis and atomic absorption spectrometry (AAS), the composition of carbon and magnesium for sludge and chicken manure was23.75% and 34.20% and 78.1575 mg/L and 71.6098 mg/L, respectively. The proposed optimal RSM parameters were assessed and validated to determine the ML-MFC operating parameters to be optimized by RSM (CCD). Full article

This short review summarizes the improvements on biological fuel cells (BioFCs) with or without ionomer separation membrane. After a general introduction about the main challenges of modern energy management, BioFCs are presented including microbial fuel cells (MFCs) and enzymatic fuel cells (EFCs). The benefits of BioFCs include the capability to derive energy from waste-water and organic matter, the possibility to use bacteria or enzymes to replace expensive catalysts such as platinum, the high selectivity of the electrode reactions that allow working with less complicated systems, without the need for high purification, and the lower environmental impact. In comparison with classical FCs and given their lower electrochemical performances, BioFCs have, up to now, only found niche applications with low power needs, but they could become a green solution in the perspective of sustainable development and the circular economy. Ion exchange membranes for utilization in BioFCs are discussed in the final section of the review: they include perfluorinated proton exchange membranes but also aromatic polymers grafted with proton or anion exchange groups. Full article

Microbial fuel cells (MFCs) are electrochemical devices focused on bioenergy generation and organic matter removal carried out by microorganisms under anoxic environments. In these types of systems, the anodic oxidation reaction is catalyzed by anaerobic microorganisms, while the cathodic reduction reaction can be carried out biotically or abiotically. Membranes as separators in MFCs are the primary requirements for optimal electrochemical and microbiological performance. MFC configuration and operation are similar to those of proton-exchange membrane fuel cells (PEMFCs)—both having at least one anode and one cathode split by a membrane or separator. The Nafion^® 117 (NF-117) membrane, made from perfluorosulfonic acid, is a membrane used as a separator in PEMFCs. By analogy of the operation between electrochemical systems and MFCs, NF-117 membranes have been widely used as separators in MFCs. The main disadvantage of this type of membrane is its high cost; membranes in MFCs can represent up to 60% of the MFC’s total cost. This is one of the challenges in scaling up MFCs: finding alternative membranes or separators with low cost and good electrochemical characteristics. The aim of this work is to critically review state-of-the-art membranes and separators used in MFCs. The scope of this review includes: (i) membrane functions in MFCs, (ii) most-used membranes, (iii) membrane cost and efficiency, and (iv) membrane-less MFCs. Currently, there are at least 20 different membranes or separators proposed and evaluated for MFCs, from basic salt bridges to advanced synthetic polymer-based membranes, including ceramic and unconventional separator materials. Studies focusing on either low cost or the use of natural polymers for proton-exchange membranes (PEM) are still scarce. Alternatively, in some works, MFCs have been operated without membranes; however, significant decrements in Coulombic efficiency were found. As the type of membrane affects the performance and total cost of MFCs, it is recommended that research efforts are increased in order to develop new, more economic membranes that exhibit favorable properties and allow for satisfactory cell performance at the same time. The current state of the art of membranes for MFCs addressed in this review will undoubtedly serve as a key insight for future research related to this topic. Full article

The present work describes a self-sustaining bioelectrochemical system that adopts simple cell configurations and operates in uncontrolled ambient surroundings. The microbial fuel cell (MFC) was comprised of white-rot fungus of Phanaerochaete chrysosporium fed with oil palm empty fruit bunch (EFB) as the substrate. This fungal strain degrades lignin by producing ligninolytic enzymes such as laccase, which demonstrates a specific affinity for oxygen as its electron acceptor. By simply pairing zinc and the air electrode in a membraneless, single-chamber, 250-mL enclosure, electricity could be harvested. The microbial zinc/air cell is capable of sustaining a 1 mA discharge current continuously for 44 days (i.e., discharge capacity of 1056 mAh). The role of the metabolic activities of P. chrysosporium on EFB towards the MFC’s performance is supported by linear sweep voltammetry measurement and scanning electron microscopy observations. The ability of the MFC to sustain its discharge for a prolonged duration despite the fungal microbes not being attached to the air electrode is attributed to the formation of a network of filamentous hyphae under the submerged culture. Further, gradual lignin decomposition by fungal inocula ensures a continuous supply of laccase enzyme and radical oxidants to the MFC. These factors promote a self-sustaining MFC devoid of any control features. Full article

The demand for alternative sources of clean, sustainable, and renewable energy has been a focus of research around the world for the past few decades. Microbial/enzymatic biofuel cells are one of the popular technologies for generating electricity from organic substrates. Currently, one of the promising fuel options is based on glucose due to its multiple advantages: high energy intensity, environmental friendliness, low cost, etc. The effectiveness of biofuel cells is largely determined by the activity of biocatalytic systems applied to accelerate electrode reactions. For this work with aerobic granular sludge as a basis, a nitrogen-fixing community of microorganisms has been selected. The microorganisms were immobilized on a carbon material (graphite foam, carbon nanotubes). The bioanode was developed from a selected biological material. A membraneless biofuel cell glucose/oxygen, with abiotic metal catalysts and biocatalysts based on a microorganism community and enzymes, has been developed. Using methods of laboratory electrochemical studies and mathematical modeling, the physicochemical phenomena and processes occurring in the cell has been studied. The mathematical model includes equations for the kinetics of electrochemical reactions and the growth of microbiological population, the material balance of the components, and charge balance. The results of calculations of the distribution of component concentrations over the thickness of the active layer and over time are presented. The data obtained from the model calculations correspond to the experimental ones. Optimization for fuel concentration has been carried out. Full article

Research related to measurements of electricity production was combined with parallel wastewater parameter reduction in a membrane-less microbial fuel cell (ML-MFC) fed with industry process wastewater (from a yeast factory). Electrodes with Ni–Co and Cu–B catalysts were used as cathodes. A carbon electrode (carbon cloth) was used as a reference due to its widespread use. It was demonstrated that all analyzed electrodes could be employed as cathodes in ML-MFC fed with process wastewater from yeast production. Electricity measurements during ML-MFC operations indicated that power (6.19 mW) and current density (0.38 mA·cm⁻²) were the highest for Ni–Co electrodes. In addition, during the exploitation of ML-MFC, it was recorded that the chemical oxygen demand (COD) removal per time for all types of electrodes was similar to the duration of COD decrease in the conditions for wastewater aeration. However, the COD reduction curve for aeration took the most favorable course. The concentration of NH₄⁺ in ML-MFC remained virtually constant throughout the measurement period, whereas NO₃⁻ levels indicated almost complete removal (with a minimum increase in the last days of cell exploitation). Full article

Improving the efficiency of microbial fuel cell (MFC) technology by enhancing the system performance and reducing the production cost is essential for commercialisation. In this study, building an additive manufacturing (AM)-built MFC comprising all 3D printed components such as anode, cathode and chassis was attempted for the first time. 3D printed base structures were made of low-cost, biodegradable polylactic acid (PLA) filaments. For both anode and cathode, two surface modification methods using either graphite or nickel powder were tested. The best performing anode material, carbon-coated non-conductive PLA filament, was comparable to the control modified carbon veil with a peak power of 376.7 µW (7.5 W m⁻³) in week 3. However, PLA-based AM cathodes underperformed regardless of the coating method, which limited the overall performance. The membrane-less design produced more stable and higher power output levels (520−570 µW, 7.4−8.1 W m⁻³) compared to the ceramic membrane control MFCs. As the final design, four AM-made membrane-less MFCs connected in series successfully powered a digital weather station, which shows the current status of low-cost 3D printed MFC development. Full article

In this paper, the effect of cathode configuration on the performance of a membrane-less microbial fuel cell (MFC) was evaluated using three different arrangements: an activated carbon bed exposed to air (MFCE), a wetland immersed in an activated carbon bed (MFCW) and a cathode connected to an aeration tower featuring a water recirculation device (MFCT). To evaluate the MFC performance, the efficiency of the organic matter removal, the generated voltage, the power density and the internal resistance of the systems were properly assessed. The experimental results showed that while the COD removal efficiency was in all cases over 60% (after 40 days), the MFCT arrangement showed the best performance since the average removal value was 82%, compared to close to 70% for MFCE and MFCW. Statistical analysis of the COD removal efficiency confirmed that the performance of MCFT is substantially better than that of MFCE and MFCW. In regard to the other parameters surveyed, no significant influence of the different cathode arrangements explored could be found. Full article

Towards the commercialisation of microbial fuel cell (MFC) technology, well-performing, cost-effective, and sustainable separators are being developed. Ceramic is one of the promising materials for this purpose. In this study, ceramic separators made of three different clay types were tested to investigate the effect of ceramic material properties on their performance. The best-performing ceramic separators were white ceramic-based spotty membranes, which produced maximum power outputs of 717.7 ± 29.9 µW (white ceramic-based with brown spots, 71.8 W·m⁻³) and 715.3 ± 73.0 µW (white ceramic-based with red spots, 71.5 W·m⁻³). For single material ceramic types, red ceramic separator generated the highest power output of 670.5 ± 64. 8 µW (67.1 W·m⁻³). Porosity investigation revealed that white and red ceramics are more porous and have smaller pores compared to brown ceramic. Brown ceramic separators underperformed initially but seem more favourable for long-term operation due to bigger pores and thus less tendency of membrane fouling. This study presents ways to enhance the function of ceramic separators in MFCs such as the novel spotty design as well as fine-tuning of porosity and pore size. Full article