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- 2. CONTENTS ⚫ Introduction ⚫ Whatarefuel cells? ⚫ Whatare microbial fuel cells ⚫ principle ⚫ Constructionof MFC ⚫ Componentsof MFC ⚫ Working of MFC ⚫ Thermodynamicsof MFC ⚫ MFC Design ⚫ Types of MFC ⚫ Applicationsof MFC ⚫ Advantagesof MFC ⚫ Limitationsof MFC ⚫ Conclusion ⚫ References
- 3. INTRODUCTION • Useof thefossil fuels can triggerglobal energycrisisand increased global warming hence there is considerable interest in research fraternityon green production ⚫ In an era of climate change, alternate energy sources are desired to replace oil and carbon resources. Subsequently, climate change effects in someareasand the increasing productionof biofuelsarealso putting pressureon availablewaterresources. ⚫ Microbial Fuel Cells have the potential to simultaneously treat wastewater forreuseand togenerateelectricity; thereby producing two increasinglyscarce resources ⚫ Microbial fuel cell technologyrepresentsa new form of renewable energy by generating electricity from what would otherwise be considered waste, such as industrial wastes orwastewateretc
- 4. Continuation…. • M.C Potterwasthe first toperformwork on thesubject in 1911 in E.coli,A professorof botanyat the Universityof Durham • In 1931, however, Barnet Cohendrew moreattention totheareawhen he created a numberof microbial half fuel cells that, when connected in series, were capable of producing over 35 volts, though only with a currentof 2 milliamps • In 1911 B.H. Kim devoloped mediatorless MFC was a milestone in MFC, Enhanced thecommercialviablity,byeleiminating costly mediator chemicals. • Microbial fuel cells havecomea long way since theearly 20th century.
- 5. Whatare fuel cells? Devicethatconvertschemical energy from fuel intoelectricity through chemical reactionwith oxygen oranotheroxidizing agent.
- 6. What are Microbialfuel cells? ⚫ Chemical energy toelectrical energy ⚫ Catalytic reactionof microorganisms ⚫ Bio-electrochemical system ⚫ Mimics bacterial interaction primary flowdiagram
- 7. ⚫ Based onredoxreactions ⚫ Harness the natural metabolism of microbes toproduceelectricity ⚫ Bacteriaconvertssubstrate intoelectrons ⚫ Electronsrun through thecircuit togeneratepower Principle
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- 9. Components of MFC ⚫Anode ⚫ Cathode ⚫ Exchange membrane ⚫ Substrate ⚫ Electrical circuit ⚫ Microbes
- 10. Anode; ⚫ Conductive,biocompatible &chemicalystablewith substrate ⚫ Stainlesssteel mesh,graphiteplatesorrods ⚫ Bacteria live in theanodecompartmentand convertsubstrateto CO2,H2O and energy ⚫ Bacteriaare kept in an oxygen less environment Anodecompartment
- 11. Cathode; ⚫ Electronsand protonsrecombineat thecathode ⚫ O2 reduced towater ⚫ Ptcatalyst is used Cathodecompartment
- 12. Exchange membrane; ⚫ NAFIONor ULTREX ⚫ Protons flows through the EM ⚫ Protonand electrons recombineon theotherside. ⚫ Can b a proton orcation exchange membrane Exchange membrane
- 13. Electrical circuit ⚫ Afterleavinganode, electrons travel through thecircuit ⚫ Theseelectrons powerthe load Electrical circuit
- 14. Substrates; ⚫ Substrates provideenergyforthe bacterial cell ⚫ Influences theeconomicviabilityand overall performancesuch as powerdensityand coloumbicefficiency of MFC ⚫ Concentration,compositionand type ⚫ Organicsubstrates-carbohydrates, protein,volatileacids,celluloseand wastewater ⚫ Acetate is commonly used as substrate
- 15. Substrates used inMFC Substrate type Concentrations Current density (m A/cm2) Acetate 1g/L 0.8 Lactate 18mM 0.005 Glucose 6.7Mm 0.7 Sucrose 2674mg/L 0.19 Glucaronic acid 6.7mM 0.18 Phenol 400mg/L 0.1 Sodium fumerate 25mM 2.05 Starch 10g/L 1.3 Cellulosic particles 4g/L 0.02 Xylose 6.7mM 0.74 Domestic wastewater 600mg/L 0.06 Brewery wastewater 2240mg/L 0.2
- 16. Microbes used inMFC ⚫Axenic bacterial culture ⚫ Metal reducing bacteria ⚫ Shewanella putrefaciens ⚫ Geobacter sulfurreducens ⚫ Rhodoferax ferrireducens ⚫ Clostridium beijerinckii ⚫Mixed bacterial fuel culture ⚫ Desulfuromonas, ⚫ Alcaligenes faecalis, ⚫ Enterococcus faecium, ⚫ Pseudomonas aeruginosa, ⚫ Proteobacteria,
- 17. Continuation….. ⚫ Clostridium butricum ⚫Bacteroidesand ⚫ Aeromonasspecies ⚫ nitrogen fixing bacteria (e.g. Azoarcusand Azospirillum)
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- 19. Continuation……. ⚫ Anodeand cathodeseparatedbycathodespecific membrane ⚫ Microbesatanodeoxidizeorganic fuel generateselectronsand protons ⚫ Protons move to thecathodecompartment through the membrane ⚫ Electrons transferred to thecathodecompartmentthrough external circuittogeneratecurrent ⚫ Electronsand protonsareconsumed in cathodechamber, combining with O2 to formwater → 2CO2 + 2H+ +8e- ⚫ Anodicreaction: CH3COO- + H2O acetate ⚫ Cathodic reaction: O2 + 4e- + 4 H+ → 2 H2O
- 20. Thermodynamics of MFC ⚫Using Gibbs freeenergy ∆G r = Gr + RT ( lnπ) 0 ⚫ Cell electromotive force W = EemfQ = ∆Gr , Q = nF Eemf = ∆ Gr∕ nF ⚫ Overall reaction in termsof the potential as Eemf = E0 emf –RT∕nF ln(π) positive fora favourabl reaction directlyproducesavalueof emf forthe reaction
- 21. MFC Design ⚫Differentconfigurationsare possible ⚫Widelyused is a twochamber MFC built in traditional ‘H’ shape Twochamberconnected bya tubecontaining a seperatorusually CEM orplain salt bridge
- 22. Types of MFCs ⚫Mediator MFC ⚫ Mediatorfree MFC ⚫ Microbial electrolysis fuel cell
- 23. Continuation…… ⚫ Soil basedMFC ⚫ Phototrophicbiofilm MFC ⚫ Nanoporous MFC ⚫ Sediment MFC ⚫ Membrane less MFC
- 24. Applications of MFC ⚫Wastewatertreatment ⚫ Powergeneration ⚫ Secondary fuel production ⚫ Bio-Sensors ⚫ Desalination ⚫ Educational tool
- 25. Advantages of MFC ⚫Generationof energyoutof biowaste / organic matter ⚫ Directconversionof substrateenergy toelectricity ⚫ Omissionof gas treatment ⚫ Aeration ⚫ Bioremediationof toxiccompounds
- 26. Limitations of MFC ⚫Low powerdensity ⚫ High initial cost ⚫ Activation losses ⚫ Ohmic losses ⚫ Bacterial metabolic losses
- 27. Conclusion ⚫ MFCs havebeen explored as a new source of electricity generation during operational waste water treatment. ⚫ Phototropic MFCs and solar powered MFC also represent an exceptional attempt in the progress of MFCs technology for electricity production. ⚫ It can be used for production of secondary fuel as well as in bioremediation of toxic compounds. ⚫ However, this technology is only in research stage and more research is required before domestic MFCs can be made available for commercialization ⚫ Provided the biological understanding increases, the electrochemical technology advances and the overall electrode prices decrease, this technology might qualify as a new core technology for conversion of carbohydrates to electricity in years to come.