Microbial fuel cells directly powering a microcomputer

© 2019 The Authors Many studies have demonstrated that microbial fuel cells (MFC) can be energy-positive systems and power various low power applications. However, to be employed as a low-level power source, MFC systems rely on energy management circuitry, used to increase voltage levels and act as energy buffers, thus delivering stable power outputs. But stability comes at a cost, one that needs to be kept minimal for the technology to be deployed into society. The present study reports, for the first time, the use of a MFC system that directly and continuously powered a small application without any electronic intermediary. A cascade comprising four membrane-less MFCs modules and producing an average of 62 mA at 2550 mV (158 mW) was used to directly power a microcomputer and its screen (Gameboy Color, Nintendo®). The polarisation experiment showed that the cascade produced 164 mA, at the minimum voltage required to run the microcomputer (ca. 1.850 V). As the microcomputer only needed ≈70 mA, the cascade ran at a higher voltage (2.550 V), thus, maintaining the individual modules at a high potential (>0.55 V). Running the system at these high potentials helped avoid cell reversal, thus delivering a stable level of energy without the support of any electronics

Biological and microbial fuel cells

Biological fuel cells have attracted increasing interest in recent years because of their applications in environmental treatment, energy recovery, and small-scale power sources. Biological fuel cells are capable of producing electricity in the same way as a chemical fuel cell: there is a constant supply of fuel into the anode and a constant supply of oxidant into the cathode; however, typically the fuel is a hydrocarbon compound present in the wastewater, for example. Microbial fuel cells (MFCs) are also a promising technology for efficient wastewater treatment and generating energy as direct electricity for onsite remote application. MFCs are obtained when catalyst layer used into classical fuel cells (polymer electrolyte fuel cell) is replaced with electrogenic bacteria. A particular case of biological fuel cell is represented by enzyme-based fuel cells, when the catalyst layer is obtained by immobilization of enzyme on the electrode surface. These cells are of particular interest in biomedical research and health care and in environmental monitoring and are used as the power source for portable electronic devices. The technology developed for fabrication of enzyme electrodes is described. Different enzyme immobilization methods using layered structures with self-assembled monolayers and entrapment of enzymes in polymer matrixes are reviewed. The performances of enzymatic biofuel cells are summarized and approaches on further development to overcome current challenges are discussed. This innovative technology will have a major impact and benefit to medical science and clinical research, health care management, and energy production from renewable sources. Applications and advantages of using MFCs for wastewater treatment are described, including organic matter removal efficiency and electricity generation. Factors affecting the performance of MFC are summarized and further development needs are accentuated

Electricity biogeneration using microbial fuel cells approach

Renewable energies are very important because they released clean gasses to the atmosphere. Hence, polluted air and water can be prevented by using renewable energy sources to generate power. Nowadays, primary fuel sources, especially fossil fuels, are used in generation of the electric energy. However, generation of electricity by using these fuel sources gives negative effects on the environment and human health. It is because the power plants will release substances for air pollution such as carbon monoxide (CO), nitrogen oxide (NOx) and also sulphur dioxide (SO2). Besides, Greenhouse gases (GHGs) was produced when the fossil fuels are burned. It will lead to climate changes and degrade the environment..

Modeling of Polarization Losses of a Microbial Fuel Cell

Microbial fuel cells (MFCs) are promising for simultaneous treatment of wastewater and energy production. In this study, a mathematical model for microbial fuel cells with air cathodes was developed and demonstrated by integrating biochemical reactions, Butler-Volmer expressions and mass/charge balances. The model developed is focused on describing and understanding the steady-state polarization curves of the microbial fuel cells with various levels and methods of anode-biofilm growth with air cathodes. This polarization model combines enzyme kinetics and electrochemical kinetics, and is able to describe measured polarization curves for microbial fuel cells with different anode-biofilm growth. The MFC model developed has been verified with the experimental data collected. The simulation results provide insights into the limiting physical, chemical and electrochemical phenomena and their effects on cell performance. For example, the current MFC data demonstrated performance primarily limited by cathode electrochemical kinetics

Living architecture: Toward energy generating buildings powered by microbial fuel cells

In this study, possibilities of integrating microbial fuel cell (MFC) technology and buildings were investigated. Three kinds of conventional house bricks from two different locations were tested as MFC reactors and their electrochemical characteristics were analysed. European standard off-the-shelf house bricks generated a maximum power of 1.2 mW (13.5 mW m−2) when fed with human urine. Ugandan house air bricks produced a maximum power of 2.7 mW (32.8 mW m−2), again with human urine. Different cathode types made by surface modifications using two kinds of carbon compounds and two PTFE based binders were tested in both wet and dry cathode conditions. The effects of both anode and cathode sizes, electrode connection, electrode configuration, and feedstock on brick MFC power generation were also studied. Water absorption test results showed higher porosity for the Ugandan air bricks than European engineering bricks, which contributed to its higher performance. This study suggests that the idea of converting existing and future buildings to micro-power stations and micro-treatment plants with the help of integrated MFCs and other renewable technologies is achievable, which will be a step closer to a truly sustainable life

Analysis and Performance Evaluation of Microbial Fuel Cells for Electricity Generation

This research work is focused on the analysis and performance evaluation of microbial fuel cells (MFCs) consisting of multiple one chamber connected in series and parallels for investigation of electricity generation. Using six units (i.e., unit A, unit B, unit C, unit D, unit E, unit F, unit G and unit H) stacked MFCs, the fuel cells were analyzed and evaluated for performance. The results obtained with a single unit microbial fuel cells show that, unit (A) produced an average power of 0.224mW, unit (B) an average power of 0.179mW, unit (C) an average power of 0.138mW, unit (D) an average power of 0.092mW, unit (E) an average power of 0.058mW, unit (F) an average power of 0.036mW, unit (G) an average power of 0.018mW, and unit (H) an average power of 0.005mW. It was observed that decrease in number of microbial fuel cells lead to a corresponding decrease in voltage and current generated, thus drop in power. Conversely, when the unit microbial fuel cells were connected together in series and parallel, improvement in power generation was recorded. An average power of 2.681mW and 2.572mW were obtained from series and parallel connection respectively.Keywords: Microbial fuel cells, anode, cathode, power, renewable energy, electricity generatio

A novel method for fabricating conductive microfibers for microbial fuel cells

The increasing demand for energy resources has urged scientists to focus on improving the renewable energy sources. Microbial fuel cells (MFCs) have received an increasing attention. Both energy conversion mechanism and electrode type have attributed to affect the efficiency of the microbial fuel cells. Electrodes as one of the most important components of the microbial fuel cells have been widely investigated. While most of the electrode materials are carbon based, there is very little effort on introducing novel materials for this purpose. This paper intends to shed an insight on the effect of using a new cathode material on the performance of microbial fuel cells. We employ hydrodynamic forces to control both molecular organization and microstructure size and shape in order to create highly structured microfibers. A microfluidic sheath flow device is used for the fabrication processes. The core flow is acrylate solution and UV light cures the photoinitiator to start the polymerization process. The exiting stream goes inside a water bath, where the sheath flow dissolves in the DI water and the core flow forms the microfibers. Controlled self-assembly can be used to deposit a thin layer of functionalized metal nanoparticles on the polymeric structure made from microfibers to enhance their electric conductivity. A conductive and porous network formed by the microfibers can be used as an efficient cathode material in microbial fuel cells. Furthermore, using this fabrication technique we can make microfibers with different shapes and sizes

Developing 3D-printable cathode electrode for monolithically printed microbial fuel cells (MFCs)

© 2020 by the authors. Microbial Fuel Cells (MFCs) employ microbial electroactive species to convert chemical energy stored in organic matter, into electricity. The properties of MFCs have made the technology attractive for bioenergy production. However, a challenge to the mass production of MFCs is the time-consuming assembly process, which could perhaps be overcome using additive manufacturing (AM) processes. AM or 3D-printing has played an increasingly important role in advancing MFC technology, by substituting essential structural components with 3D-printed parts. This was precisely the line of work in the EVOBLISS project, which investigated materials that can be extruded from the EVOBOT platform for a monolithically printed MFC. The development of such inexpensive, eco-friendly, printable electrode material is described below. The electrode in examination (PTFE-FREE-AC), is a cathode made of alginate and activated carbon, and was tested against an off-the-shelf sintered carbon (AC-BLOCK) and a widely used activated carbon electrode (PTFE-AC). The results showed that the MFCs using PTFE-FREE-AC cathodes performed better compared to the PTFE-AC or AC-BLOCK, producing maximum power levels of 286 μW, 98 μW and 85 μW, respectively. In conclusion, this experiment demonstrated the development of an air-dried, extrudable (3D-printed) electrode material successfully incorporated in an MFC system and acting as a cathode electrode

Optimization of Microbial Fuel Cells

Optimization of microbial fuel cells is investigated by utilizing Shewanella oneidensis as a model microorganism. the microbe\u27s ability to grow and use glucose as a carbon source is explored under varying oxygen environments through an offline PMP derivatization method and HPLC analysis. Shewanella growth and glucose utilization is enhanced under aerobic environments; however, under microaerobic environments the addition of ferric iron results in a faster exponential growth initialization. a flavin mononucleotide modified indium tin oxide electrode is prepared and characterized for its usefulness in microbial fuel cells by controlled potential electrolysis, cyclic voltammetry, and electrochemical impedance spectroscopy studies. the electrode is shown to decrease impedance and charge transfer resistance when compared to a bare electrode. Additionally, the electron transfer mechanism is shown to be scan rate dependent. the addition of the monolayer decreased the contact angle resulting in a more hydrophilic surface for microbial attachment. the enhancement of electron transfer is explored through the poising of Shewanella on the modified electrode in the potential range of +0.6 to -0.6 V. Cyclic voltammetry studies performed immediately after poising results suggest catalytic election transfer occurs when Shewanella utilizes the FMN monolayer. Outer membrane protein reduction is absent in cyclic voltammetry following poising indicating direct electron transfer is blocked when the FMN monolayer is present. Current density is shown to increase as the poising potential becomes more negative with a maximum current achieved at -0.2 V. This increase in current density correlates to a decrease in impedance and charge transfer resistance with -0.2 V having the lowest overall initial impedance

PEM-Less Microbial Fuel Cells

Microbial fuel cells (MFCs) are comparatively new technique of simultaneously generating electricity from bio-waste while degrading the organic waste. The use of microbes to generate electricity is an uninterrupted process in MFCs since the bacteria replicate and continue to produce power indefinitely as long as there is enough food source to nurture the bacteria. Besides, MFCs have the potential to produce hydrogen for fuel cells, desalinate sea water, and provide sustainable energy sources for remote areas. Factors like type of electrodes used in the cells, partitioning of cells, oxygen complement and configurations are important factors that affect the performance of MFCs. The fabrication of microbial fuel cells of different configurations and the relationship between the factors affecting the efficiency of single chambered (SC-MFCs) and double chambered (DC-MFCs) will be presented. The experimental data on observations made on the effects of these materials on the MFCs characteristics, electricity generation and wastewater treatment have also been included. The main aim of this study is to find out whether a nonconventional inexpensive clay could be used as an ion-exchange medium alternative to the conventional expensive PEM in the fabrication of MFCs. The results obtained on power generation, current density, open circuit voltage, etc., clearly show that PEM-less MFCs can be used as practical devices for sustainable energy generation