Binder-free SeNP-decorated cathodes and bioanodes for dual-chambered microbial fuel cells

<i>Harvesting Energy using Biocatalysts</i>

Microbial fuel cells (MFCs) have emerged as a promising technology to convert biomass and organic waste into electricity, offering an eco-friendly and sustainable alternative to fossil fuels. Recent innovations in nanotechnology have significantly enhanced the performance and efficiency of MFCs by improving electron transfer rates, expanding surface areas, and optimizing the properties of anode and cathode materials. This review provides a detailed assessment of the fundamental and functional components of MFCs. These components include the anode, which facilitates the oxidation of organic matter, and the cathode, where the reduction of oxygen or other electron acceptors occurs. Another critical component is the proton exchange membrane (PEM), which allows the transfer of protons from the anode to the cathode while preventing oxygen from diffusing into the anode chamber. In addition to discussing these key elements, the article explores the role of various microorganisms involved in MFCs. These microorganisms, which include both naturally occurring species and genetically engineered strains, play a vital role in facilitating extracellular electron transfer (EET), a process that enables the conversion of chemical energy stored in organic compounds into electrical energy. We analyze different biomass pretreatment strategies, such as physical, chemical, and biological approaches, that enhance the breakdown of lignocellulosic biomass to improve energy output. Furthermore, the review highlights optimization techniques for improving biomass-powered MFC performance, such as electrode modification, pH control, and organic loading rate management. The application potential of MFCs is extensively discussed, covering bioremediation, wastewater treatment, biosensors, and power generation, with a particular focus on MFC-based biosensors for environmental monitoring and medical diagnostics. Despite their immense potential, challenges such as low power output, biofouling, and high operational costs hinder large-scale commercialization. To address these issues, we propose innovative strategies, including the integration of nanomaterials, electroactive microorganisms, and advanced membrane designs, to enhance the efficiency and reliability of MFCs. We conclude that nanotechnology-enabled MFCs, combined with engineered microbes and optimized system designs, hold immense potential for revolutionizing sustainable energy generation and biosensing applications, paving the way for a cleaner and more efficient future.

Recent advances in bioelectricity generation through the simultaneous valorization of lignocellulosic biomass and wastewater treatment in microbial fuel cell

MFC-mediated wastewater treatment technology and bioelectricity generation: Future perspectives with SDGs 7 & 13

Increasing demand for renewable energy in the backdrop of global change calls for waste valorization and circular economy strategies. Public health concerns and demand for clean energy provide impetus to the development of wastewater based MFC. Wastewater treatment and simultaneous generation of bioelectricity offer a myriad of environmental benefits. Nevertheless, it is pertinent to know the challenges with the microbial fuel cell (MFC) technology to upscale the wastewater based MFC. This paper attempts to critically analyse the processes, application, challenges and opportunities of wastewater based MFCs. A literature survey was conducted to find out the advances in the field of wastewater based MFCs and the focus was to decipher the challenges to the implementation of wastewater based MFCs. Recent developments in MFC technology have improved the power output and studies show that a diverse group of organic-rich wastewater can be treated with MFCs. The developments include improvements in MFC configuration, development of biocatalysts and biocathode, anodic biofilm formation, microbial community interactions, and progress in the organic and pollutant removal. Nevertheless, the MFC technology is replete with challenges about the organic removal rate, power density, electrode performance limiting factors, economic viability, high initial and maintenance cost and difficulty to maintain the exoelectrogens activity in a complex wastewater environment. Opportunities exist in scaling up of MFCs, integration with other wastewater treatment methods and measures to minimise the operating costs. MFCs have the potential to increase the resilience capacity of the sustainable wastewater treatment plant.

A critical review of the symbiotic relationship between constructed wetland and microbial fuel cell for enhancing pollutant removal and energy generation

Environmental challenges related to water quality are not unique to impoverished nations, but are also among the most fundamental human demands worldwide. The need for clean water and power is growing by the day. Wastewater is seen as a source of both water and energy. Because of the high energy requirements and high cost, current wastewater treatment systems are associated with limitations. It is vital to create a technology that can produce viable alternatives to current energy resources. Microbial fuel cells (MFCs) are a cutting-edge technology, which have been developed and are now undergoing extensive research in order to treat wastewater sustainably. Showcasing a promising future as a sustainable method, microbial fuel cell (MFC) technology recovers energy and nutrients simultaneously to create bioelectricity, which uses the power of electro-genic microbes to oxidize organic contaminants found in wastewater. Sustainable MFC implementations may be a practical solution for carbon sequestration, biohydrogen synthesis, wastewater treatment, environmentally sustainable sewage treatment and green power production due to the constraints of traditional wastewater treatment. However, because to the challenge of balancing yield with total system upscaling, MFC electricity production remains a significant obstacle for practical applications. The advancements in MFC technologies are covered in this chapter, including modifications to their structural design, incorporation of various novel anode and cathode materials, diverse microbial community interactions and substrates to be utilized and the elimination of contaminants. Additionally, it concentrates on offering crucial insights and examining different applications and futuristic facets of MFCs connected to wastewater treatment and consequently, sustainable resource recovery. By the study we anticipate the industrialization of MFCs in the near future with proper planning and additional research, believing that this would result in cleaner fuels and a better environment for all people.

Microbial Fuel Cells (MFCs) have been intensively studied as a promising technology for energy harvesting. However, in recent years it has become apparent that electricity production from MFCs may not yield energy densities comparable to chemical fuel cells or conventional batteries - but MFCs can provide sustainable and cost-effective wastewater treatment. Conventional centralized wastewater treatment is a very costly process requiring significant infrastructure and energy input. Further, water recycling from conventional wastewater treatment plants is becoming a more acceptable method to deliver clean water in drought-stricken areas, requiring even more energy and infrastructure for disinfection and distribution. In contrast to conventional wastewater treatment technologies, MFCs enable a decentralized method for wastewater treatment, water recycling, real-time monitoring and direct control of organic removal and biomass production. In addition, direct recovery of electric energy, high quality effluents and low environmental footprints can be achieved through MFC technologies. However, while MFCs hold tremendous promise, the practical application of MFC technology has not been realized due great challenges in cost, system stability and optimization – all necessary steps in technology scale up and commercialization. In this study various aspects of MFC technology development from lab prototypes to practical installations for wastewater treatment have been evaluated. An MFC installation consisting of twelve MFC single chamber reactors (Fig. 1) has been designed and explored under real environmental conditions. Each reactor has a rectangular shape with either one or two anodes, positioned at the top and the bottom of the MFC, and two gas-diffusion cathodes. The installation operates under flow through mode with swine waste used as the inoculum source (along with lagoon sediment) and feed solution. In terms of accelerated organics removal, various aspects have been addresses related to reactor design, electrode optimization, operational characteristics, cathode biofouling, biofilm development and bacterial enrichment at the anode. Each of the design aspects has been evaluated first in the lab and then transferred to the field for validation. A start up time of 5 days has been achieved with 0.55 V at 560 Ω. The long-term operation under MFC mode demonstrated 0.27 V at 22 Ω and ~1kg/m3.d COD removal. Interrupted mode of operation provided more stable MFC output and prolonged cathode life span. Figure 1

Improving power output in microbial fuel cells with free-standing CoCx/Co@CC composite anodes

Engineering extracellular electron transfer to promote simultaneous brewing wastewater treatment and chromium reduction

Microbial fuel cells as a sustainable platform technology for bioenergy, biosensing, environmental monitoring, and other low power device applications

Microbial Fuel Cell (MFC) technology has been heralded as a tool for energy conservation, resource recovery and valuable compound synthesis, amongst others. The MFC concept is possible due to the ability of electrochemically active bacteria (EcAB) to transfer the electrons produced from substrate degradation, out of the bacterial cell and onto the electrode surface via different mechanisms; a process called exocellular electron transfer (EET). However, despite advances and extensive studies on EET mechanisms and EcAB, like the Fe(III)-reducing Geobacter sulfurreducens PCA, the technology has not reached yet the stage of broad applicability. This thesis investigates characteristics and performance of EcAB in the anodic compartment of pure- and mixed-culture MFCs in an effort to shed light to processes important to MFC performance and efficiency. In order to reliably study EcAB in a microbial fuel cell environment, a gas-tight, sterile MFC setup was developed and optimized for electrochemical and microbiological studies of the anodic bacteria and consequently the electrochemically active biofilm/bioanode. In addition, a method for Geobacter species quantification with quantitative PCR (qPCR) was developed. Furthermore, a multiple-unit MFC setup was designed for convenient and simultaneous operation of identical MFCs ‘in-parallel’. A design for a new compact, multi-array MFC to be used as a small-scale culturing platform of EcAB based solely on their electrochemical properties is also introduced. Our research with different titanium (Ti) electrodes in the same MFC setup, suggests that the MFC electrode surface is critical as it determines attachment of EcAB and bioanode formation that leads ultimately to efficient electrochemical activity. Pt- and Ta- coated Ti electrodes performed the best while uncoated Ti with either smooth or rough surfaces performed the worst. Future MFC research could benefit greatly from enhancing the electrode interface for optimum bioanode formation and electron transfer. Our studies with flat-plate, graphite-electrode, mixed-culture microbial fuel cells (Pmax ≈ 1 W/m2) operated for several months with external load (Rext), indicated stable and reproducible characteristics including Coulombic efficiencies, average values of cell voltage, anode potentials, and current densities as well as main microbial populations of both the anolyte and the bioanode. However, transient testing of power maxima values (Pmax) that required lower Rext, or applied potential showed result variability, that might be linked to differences in electrochemical impedance factors, redox-active centers and electron-producing states of the bioanodes. Differences in the quantities of the bioanode microbial species did not seem to correlate with this variability. Since energy-conserving applications like waste-water treatment MFCs would ideally be operated with an Rext rather than applied voltage, addressing interface impedance factors, such as charge transfer resistance and electrical double layer capacitance, is important especially when MFCs are operated at lower Rext. Furthermore, mixed-culture MFCs were shown to be selective for certain bacterial consortia, including Geobacter- and Pseudomonas- related species. Geobacter-related species were dominant on the surface of different electrodes suggesting a pivotal role of the species in electrochemical activity and EET. This was not surprising as the original mixed-culture inoculum - used for starting up several bioelectrochemical systems at our research facilities - was amended with pure cultures of G. sulfurreducens PCA. However, the strain specifically selected for and present in most bioanodes was a novel Geobacter, strain T33 that was phylogenetically closely related (99% by 16S rRNA sequence similarity) to several strains detected in a variety of MFCs operated by other research groups under various conditions and anodic substrates. These strains formed a new phylogenetic Geobacter cluster, distinct from G. sulfurreducens. This observation suggested that strain T33 might have an ecological advantage in MFCs over G. sulfurreducens PCA. In-depth characterization of strain T33 in pure-culture experiments showed that strain T33 forms efficient bioanodes with high Pmax similar to strain PCA, but exhibits different redox-centers than strain T33. Furthermore, strain T33 has a more limited electron acceptor range, but a wider electron donor range than strain PCA, including glucose and succinate. Phylogenetic analysis indicated that strain T33 and recently described electrochemically active strains G. soli GSS01 and G. anodireducens SD-1 are closely related (99% by 16S rRNA) and form a new phylogenetic cluster within the Geobacters, 98% by 16S rRNA similar to G. sulfurreducens strains PCA and KN400. Genome-based analyses indicates that even though the two clusters share common metabolic properties, some differences exist with respect to electron donor utilization, attachment and conductive cell surface components (e-pili) production and genome rearrangement and gene acquisition. It is not sufficiently clear how the differences in the genome of strain T33 are relevant to persistence of the strain in MFCs, biofilm formation and EET, our studies overall suggest that strain T33 even though producing similar power densities as G. sulfurreducens PCA, might be more stable and versatile in MFCs, and therefore a better candidate for waste-water treatment if it can couple the oxidation of several organic substrates, as observed with Fe(III)-respiration, also to electrode-respiration.

Wastewater treatment is an energy intensive process that removes contaminants and protects the environment. While some wastewater treatment plants (WWTPs) recover a small portion of their energy demand through sludge handling processes, most of the useful energy available from wastewater remains unrecovered. Efforts are underway to harness energy from wastewater by developing microbial fuel cells (MiFCs) that generate electricity. Key challenges to the development of microbial fuel cells include inefficiencies inherent in recovering energy from microbial metabolism (particularly carbon metabolism) and ineffective electron transfer processes between the bacteria and the anode. We explored the prospects for constructing microaerobic nitrifying MiFCs which could exhibit key advantages over carbon-based metabolism in particular applications (e.g., potential use in ammonia-rich recycle streams). In addition, we evaluated nanostructure-enhanced anodes which have the potential to facilitate more efficient electron transfer for MiFCs because carbon nanostructures, such as nanofibers, possess outstanding conducting properties and increase the available surface area for cellular attachment. In the initial phase of this project, we investigated the performance of a novel nitrifying MiFC that contains a nanostructure-enhanced anode and that demonstrated power generation during preliminary batch testing. Subsequent batch runs were performed with pure cultures of Nitrosomonas europaea which demonstrated very low power generation. After validating our fuel cell hardware using abiotic experiments, we proceeded to test the MiFC using a mixed culture from a local wastewater treatment plant, which was enriched for nitrifying bacteria. Again, the power generation was very low though noticeably higher on the nanostructured anodes. After establishing and monitoring the growth of another enriched nitrifying culture, we repeated the experiment a third time, again observing very low power generation. In the absence of appreciable and repeatable power production from pure and mixed nitrifying cultures, we focused on the second major objective of the work which was the fabrication and characterization of carbon nanostructured anodes. The second research objective evaluated whether or not addition of carbon nanostructures to stainless steel anodes in anaerobic microbial fuel cells enhanced electricity generation. The results from the studies focused on this element were very promising and demonstrated that CNS-coated anodes produced up to two orders of magnitude more power in anaerobic microbial fuel cells than in MiFCs with uncoated stainless steel anodes. The largest power density achieved in this study was 506 mW m2, and the average maximum power density of the CNS-enhanced MiFCs using anaerobic sludge was 300 mW m2. In comparison, the average maximum power density of the MiFCs with uncoated anodes in the same experiments was only 13.7 mW m2, an almost 22-fold reduction. Electron microscopy showed that microorganisms were affiliated with the CNS-coated anodes to a much greater degree than the noncoated anodes. Sodium azide inhibition studies showed that active microorganisms were required to achieve enhanced power generation. The current was reduced significantly in MiFCs receiving the inhibitor compared to MiFCs that did not receive the inhibitor. The nature of the microbial-nanostructure relationship that caused enhanced current was not determined during this study but deserves further evaluation. These results are promising and suggest that CNS-enhanced anodes, when coupled with more efficient MiFC designs than were used in this research, may enhance the possibility that MiFC technologies can move to commercial application. This title belongs to WERF Research Report Series . ISBN: 9781843393368 (Print) ISBN: 9781780403458 (eBook)

The demand for power is quite significant on a global scale. Microbial Fuel Cell (MFC) Technology may be used to reduce reliance on fossil fuels and to provide alternative sustainable energy sources. MFC Technology uses microorganisms to produce power using the organic matter found in the environment. MFC is a biofuel cell, that generates electricity by converting organic material into electricity. Due to its ability to use wastewater as a substrate and to not require a metal catalyst, it can be taken into consideration as a more sustainable alternative for traditional fuel cells. Waste material are first transformed to chemical energy and then, after being treated to the desired level to electrical energy. An anode, cathode and a separation membrane are the basic components of MFC. MFC technology has the potential to become a more environment friendly fuel cell alternative. Despite being viewed as a promising technology, MFC is not yet commercially viable for usage on a large scale due to its poor current generation per unit cost and high internal resistance. More study should be conducted on the creation of more efficient electrode materials and the development of resilient microorganisms as biocatalysts in order to boost the viability of MFC technology.

Agri‐food waste valorisation