Microbial Fuel Cell
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A brief overview about Microbial Fuel Cell
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Microbial Fuel Cell
- 1. Microbial Fuel Cell Maria Majeed
- 2. Contents • • • • • • • • • • Introduction Working Principle Designs Electrode Material Microbes Substrates Electrochemical Monitoring Efficiency Challenges Applications
- 3. Introduction A microbial fuel cell (MFC) is a bioreactor that converts chemical energy in the chemical bonds in organic compounds to electrical energy through catalytic reactions of microorganisms under anaerobic conditions.
- 5. The maximum amount of Power Density generated by the MFC is 1kW/m3 of reactor volume
- 6. Working Principle of MFC
- 9. Mechanism of Electron Transfer
- 10. MFC Designs To increase Power Output •To Decrease the Cost To minimize the Power Losses •To increase Performance
- 15. Anode Material Electrode Material Carbon Mesh Graphite felt Graphite fiber Carbon Felt Carbon Cloth
- 16. Cathode Material Platinum coated electrodes higher catalytic activity with oxygen Generate greater amount of power But they are Expensive Platinum Coated cathodes Platinum Black
- 17. Ferricyanide (K3(Fe(CN)6) Good performance and Low Overpotential
- 20. Microbes Used in MFCs • • • • • Shewanella Geobacter Klebsiella pneumonia Rhodopseudomonas palustris Dessulfobulbus propionicus
- 21. Substrates in MFCs Columbic Efficiency and Power Density of MFC are controlled by Substrates
- 24. Electrochemical Monitoring V= Voltage (volts) R= Resistance(ohms) I= Current (Ampere) Q= Charge (Coulombs) t= time (seconds) I= Current (Ampere)
- 25. Electrochemical Monitoring Q= Charge (Coulombs) P= Power (Watts) E= Energy (Joules) t= time (seconds)
- 26. Efficiency of MFCs Coulombic Efficiency is calculated as: CE=columbic efficiency Cp= total coulombs Cti= theoretical amount of columbs F= Faraday’s constant b= no of moles of electrons produced per mole of substrate S= substrate concentration V= liquid volume M= Molecular weight of the substrate used
- 27. Challenges Low Power • 14mA • 300 Wm-3 power • New strain for the generation of electricity Microbe/Electrode Interaction • To avoid biofouling and corrosion
- 28. Challenges Large Scale Losses Fuel Oxidation Rate Anode catalytic activity, proton and electron diffusion Internal Resistance Can be reduced by decreasing the spacing and increasing the surface area Power Density High Internal Resistance, over potential Coulombic Efficiency Substrate Conversion to Carbon dioxide
- 29. Applications • • • • • • • Electricity generation Remote Sensors Bioremediation Wastewater treatment Hydrogen production Biosensors for pollution analysis Desalination
- 30. 1. Wastewater Treatment Engineers at Oregon State University have made a breakthrough in the performance of microbial fuel cells that can produce electricity directly from wastewater
- 32. 3. Remote Sensors Scientists have submerged a traditional wireless thermometer in the Palouse River in Washington
- 33. 4. Bioremediation MFC has been installed in Mexico
- 34. 5. Remote Power Source • In rural areas of Africa, 74% of population lives without Electricity
- 35. 6. Desalination
- 36. 7. Brewery Wastewater Treatment Fosters, an Australian beer company has established a wastewater treatment plant to produce electricity and to clean the water
Notas do Editor
- Many factors are involved in establishment of the MFC at commercial level and vast research is still needed in different fields from microbiology and electrochemistry to material and environmental engineering.
- Microbial fuel cell is considered to be an alternative and new source of energy along with treating the waste wateras it proves to be an ideal solution for the wastewater treatment and energy demand of domestic use.
- It consists of electrical circuit, anode, cathode and semipermeable membrane which allows the flow of Hydrogen ions but prevent oxygen to pass through it. This is the result of electro chemical gradient making high concentration of hydrogen ions around anode. Anode is placed in anaerobic condition because oxygen inhibits the electricity generation.
- A solution containing glucose or acetate which is commonly present in sewage water. Nicotinamide adenine dinucleotide (NADH) is a biological membrane transporter which release high energy electrons and hydrogen ions and then terminal electron acceptors accept these electrons like nitrate, sulphate or oxygen. But in microbial fuel cell, a mediator molecule is added which snatches the electron from ETC instead of being accepted by accepters and is then taken to the anode where it is transported to the cathode and the current is measured by the voltmeter or ammeter connected to the device.
- A solution containing acetate or glucose is added which is normally present in sewage water
- In a normal bacterial cell, the electron continues along the dotted red path where it combines with oxygen to make water. In a microbial fuel cell, the electron continues along the solid red path, where it is picked up by a mediator molecule and taken to the anode.
- biofilms which act as electron acceptor and transfer electrons to the anode surface and thus more energy is produced in this way. Few other electron acceptors are c-type cytochromes and highly conductive pili (nanowires) Shewanellaputrefaciens, Geobactersulferreducens, Geothrixferementans their own mediators or added (mediated transfer)gain electron, get reduced and become permeable to the cell membrane and thus easily transfer electrons to the electrode(Lovley, 2006). Normally used redox mediators are red, thionine, methylene blue, anthraquinone-2, 6-disulfonate, henazines and iron chelates Escherichia coli, Streptococcus lactis, and Pseudomonas so mediators are compulsory for MFCs using these bacterial species. Becz they can’t transfer electron…. penetrating ability, electron grabbing tendency from the electron transport chain carriers, increased electron transferring ability from the metabolite and increased stability during the redox cycling
- research purposes only as they have power and electode losses, very high internal resistance
- simple and cost minimizing strategy, which also increases the power generationBy decreasing the distance, we can decrease the ohmic resistance
- anode is located at the bottom of the cylinder and cathode is located upwards. Glass wool and beads layers for partitioning
- MFCs are connected in series or parallel combination to obtain the best outputMore energy can be generated in parallel combination but is more likely to short circuiting than series connection (I= I+I+I)
- The difference between the real voltage (E) and theoretical voltage (Et))ferric iron, manganese and cobalt
- SEM should allow hydrogen ions to pass through but not oxygen gas to diffuse back to anode chamberThe power output relies on proton transfer from anode to cathode which is a slow process results in high internal resistance SINGLE chamber ----- give high power output but it diffuses oxygen into the anaerobic chamber
- Although single chamber(membrane less) MFCs are described to produce higher power density, membrane absence would diffuse the oxygen back to the anode and thus decreases the coulombic efficiency and bioelectrocatalytic activity of the microbes
- In MFCs, both pure and mixed cultures can be used but mixed cultures are shown to produce higher power but with higher internal resistance for metabolic disturbances and substrate consumption than pure cultures. have the ability to reduce iron (Shewanellaand Geobacter) other are isolated from waste water ((Klebsiella pneumonia, )
- Substrates control the columbic efficiency and power density of the MFC along with providing energy to bacteria. from simple to complex sugars and low to high molecular weight compounds and volatile acids, cellulose, wastewater, proteins, Acetate has been proved to be the best feed of MFCs as it produces maximum power density and high columbic efficiency (The amount of electrons retrieve as current vs. the maximum regaining from the Substrate) because it is inert towards many metabolic pathways such as fermentation and methanogenesis
- It is done with the help of multimeter attached to the wire and resistance has been fixed.
- research is still needed to develop a new strain for the generation of electricity as this process is not controlled by a singles gene but many genes Biofouling or biological fouling is the accumulation of microorganisms, plants, algae, or animals on wetted surfaces. there is a need to develop higher catalytic material with superior performance due to degradable mechanisms of electrode material
- . Geothrixfermentans and Geobacter has the ability to oxidize the substrate completely(94-100% coulombic efficiency by oxidizing acetate).The power density is influenced by high internal resistance or over potential, activation and mass transfer losses the fuel oxidation rate is controlled by anode catalytic activity, fuel diffusion, proton and electron diffusion and consumption diffusion of oxygen to the anode also reduces the coulombic efficiencyThe main challenge in implementing MFC on a large scale is in maintaining low costs, minimizing hazards while maximizing power generation
- bacteria can oxidize organic waste present in the sewage water and water can be cleaned up to 80%. Water must be first treated extensively to remove toxins and other non-biodegradable products as the composition varies, then the process is same as used for brewery wastewater treatmentWhile this high costs for pretreatment will be balanced by the electricity production by MFCs in oceans and rivers can be saved up by reducing the amount of pollutant being dumped
- An alternative source of energy can be produced. an external current source is supplied to overcome the energy barrier inconverting all the substrate into carbon dioxide and hydrogen gas0.25 volts of electric current and anaerobic conditions in both chambers90% of electrons and protons are converted into hydrogen gas which bubbles at the cathode and can be used as fuel so very efficientConventional method of hydrogen production requires 10 times the amount of energy as in MFC
- provide energy to low-power sensors that gather information from remote areas.Then anaerobic bacteria reproduce and metabolize to generate small amount of current which can be used to charge a capacitor to store energy for the sensor provide energy for a longer time to sensors than traditional batteries.
- MFCs are left on the remote water bodies with anode being submerged in the water where organic matter feeds the growing bacteria and cathode remains on the top of the water : Thus organic matter is broken down to carbon dioxide and hydrogen, cleansing the polluted lake or river. Compounds like toluene and benzene found in gasoline can be decomposed by bioremediation of water containing these compounds
- most attractive and cheapest way to provide energy since 1980s in areas of Africa, where 74% of the population lives without electricity homemade MFC which can at least charge a cell phone battery and can act as a source of lightening tool in rural areas of world
- A great amount of energy is required to remove salts from sea water to use it for drinking purposes Now can be done with no external energyA third chamber is placed in between the two electrodes of a standard MFC and positive and negative ions of the salt present in the sea water filled in it, are attracted towards the negative and positive electrodes respectively by using semi-permeable membranes. Efficiency of salt removal has been observed to be 90% in the laboratory but much more efficiency is required to use it for drinking purposes at
- Fosters’ plan is Partnered with the University of Queensland, and their goal is to improve the cleaning power and electrical output of MFCs and ultimately build a 660 gallon, 2 Kilowatt MFCThe power generated from cleaning the brewery wastewater is expected to be balanced by the initial cost of the Microbial Fuel Cell in 10 years.it is rich in organic matter and it’s composition is always same so constant conditions allow bacteria to grow more efficiently and to become adapted to the conditions. Microbial cells are arranged in parallel to increase the volume of cleaning water. And one long tube indicates one MFC. Wastewater is added at the top and after processing clean water comes out from the bottom. Fosters’ plan is Partnered with the University of Queensland, and their goal is to improve the cleaning power and electrical output of MFCs and ultimately build a 660 gallon, 2 Kilowatt MFC that cleans all of