Table of Contents Chapter 1. 2 INTRODUCTION..
2 1. ENERGY NEEDS AND MFCs: 2 1.2. MFCs AND ENERGY SUSTAINABILITY OF THE WATER INFRASTURCTURE: 3 Chapter 2.
4 LITERATURE REVIEW… 4 2. MICROBES: 4 2.1. MICROBIAL FUEL CELL: 4 2.
2. TYPES OF MFCs: 4 2.2.1. Mediated: 4 2.
2.2. Mediator-free: 5 2.2.3. Soil Based: 5 2.
3. PRINCIPLE OF MICROBIAL FUEL CELL: 6 2.4. MFC DESIGN: 7 2.4.1. Double-Chamber MFC Design: 7 2.4.
2. Single-chamber MFC Design. 7 2.
5. APPLICATIONS OF MFCs: 7 2.5.1. Generation of Bioelectricity: 7 2.
5.2. Waste Water Treatment: 8 2.6. MICROBIOLOGICAL ASPECT: 8 Chapter 3. 9 METHODOLOGY. 9 3. COMPONENTS.
9 3.1. CONSTRUCTION..
9 3.2. PROCEDURE. 12 3.3.
POWER GENERATION.. 13 Chapter 4. 14 RESULT AND DISCUSSIONS. 14 4. RESULTS. 14 4.1.
DISCUSSION.. 14 Chapter 5.
15 CONCLUSION AND RECOMMENDATIONS. 15 5. LIMITATIONS. 15 5.1.
RECOMMENDATIONS. 15 5.2. ENERGY AND THE CHALLENGE OF GLOBAL CLIMATE CHANGE.
15 Chapter 1INTRODUCTIONEnergyconsumption is increasing day by day within the world. These energy sourcesinclude fossil fuel, renewable sources and nuclear sources in which non-renewablesources of energy, which include enormous portion of energy consumption, couldbe categorized into major classification; nuclear and fossil. These energy sourcesare causing global warming and climate change. Fossil fuels have been formedfrom the organic remains of long-dead plants and animals. They contain a highpercentage of carbon and hydrocarbons. Primary sources of energy used aroundthe world include petroleum, coal, and natural gas, all fossil fuels. Withenergy needs increasing, the production and use of these fossil fuels createserious environmental concerns.
Until a global movement for renewable energy issuccessful, the negative effects of fossil fuel will continue.1. ENERGY NEEDSAND MFCs:Aswe know that we urgently need a alternative source of energy. We are currentlyusing fossil fuel which is unsustainable for us and for our environment that iswhy many searches are being conducted for replacement of energy source. And itdoes not appear that one replacement will fulfill the whole energy necessity.Some countries around the world have made remarkable efforts to find a piece ofcogent solution like Renewable sources, solar energy and energy produced bywind and water. These efforts proposed a new discovery of Microbial Fuel cellin which bacteria can be used to produce electricity from waste water andrenewable biomass.
This discovery has gained much attention due to itsuniqueness. It is the one of the 50 top most inventions of 2009 in Timemagazine. This lead to increase interest in MFC and raise number ofpublications. These systems are very adaptable and provide much energy insustainable way but the major improvement was widespread of this application. MFCsuse active microorganisms as a catalyst in anaerobic mode for the production ofbioelectricity. Electrical current produced by bacteria was first observed byPotter in 1911 and its research domain became wider in 1999s. The microbialfuel cell is a bio-electrical system in which bacteria is used to convertorganic material into electricity. Soil is filled with bacteria thatproduce electricity when they are placed in Microbial Fuel Cell (MFC).
Suchbacteria filled soil is found almost everywhere on earth. An MFC has twoelectrodes and an area that separates that electrode (called a membrane). Foran MFC to work properly, electricity in form of electrons must flow into oneelectrode and leave the other. Some types of soil bacteria can help generate electricity;these are known as electrogenic bacteria, includes the shewanella species thatcan be found in almost all soil types. And the geobacter species which preferliving in soil deep underground or even under the ocean where no oxygen ispresent. The soil bacteria eat the nutrients in the soil, sugars, and in turnproduce electrons that are released back into the soil, which can be used tocreate electricity in the form of energy. 1.1.
1.2. MFCs AND ENERGY SUSTAINABILITY OF THE WATER INFRASTURCTURE:Energyand water are intricately connected. Energy is itself required to make waterresources available for human use and consumption (including irrigation)through pumping, transportation, treatment, and desalination. Over two billionpeople on the planet lack adequate sanitation and one billion do not haveaccess to portable water. Energy demands for conventional water and waste waterprocesses as a large part of the problem. We serve our most part of producedelectricity in the treatments of water. So greatly need a new sustainablesource of energy production in the form of MFCs.
And also MFCs are used inwater treatment to harvest energy utilizing anaerobic digestion.The process can also reduce pathogen. Chapter 2LITERATURE REVIEWLiteraturereview will provide handy information about MFCs.
It will reveal the relevantinformation about the technology used in Microbial Fuel Cell. It will let thereader to understand its design and function. 2. MICROBES:Inorder to understand the fundamental principle of Microbial fuel cell it isimportant to have information about the microorganisms. Bacteria are the majormicrobes which are involved in this process. Bacteria breakdown organic matterand release energy in the process.
Some bacteria have the ability to generateelectricity and to transfer electrons effectively to anode. The bacteria whichhave this ability are known as “Exoelectrogen”. Exoelectrogen have the abilityto generate electricity in microbial fuel cells by extracellular electrontransfer to anode. It directly transfers electrons to a chemical or materialthat is not immediate electron acceptor.
Theseelectrogens can be sourced in sand, water and many other sources. But here weare using soil as a source.2.1.
MICROBIALFUEL CELL:Microbialfuel cell is a bio-electrical system in which bacteria is used to convertorganic material into electricity.2.2. TYPESOF MFCs:Thereare two types of MFCs:1. Mediated2.
Mediator-free3. Soilbased2.2.1. Mediated: In this type ofmicrobial cells a mediator is used o transfer electrons to electrode.
Examplesof commonly used mediators are thionine, methyl blue and neutral red etc. 2.2.2. Mediator-free: Mediator free MFCsused electrochemically active microbes (mostly bacteria) to transfer electronsdirectly to electrode. Mediator-free cells can directly obtain energy fromcertain plants.
This is known as plant microbial fuel cell. Possible plantsinclude sweet grass, tomatoes and algae etc. It can provide ecologicaladvantages.Figure1.2: A plantmicrobial fuel cell 2.2.3. Soil Based: In soil based MFC,soil acts as a nutrient rich anodic media, the inoculums and proton exchangemembrane.
The anode is placed at the bottom whereas cathode is placed at thetop and is exposed to the air. Soil is filled with diverse microbes, includingelectrogenic bacteria, is full of complex sugars and other nutrients obtainedfrom plants and animal material decay. Figure2.3: Soil based MFC 2.3. PRINCIPLEOF MICROBIAL FUEL CELL:”Microbialfuel cells (MFCs) are electrochemical devices that use the metabolic activityof microorganisms to oxidize fuels, generating current by direct or mediatedelectron transfer to electrodes.
” K. Rabaey and W. Verstraete, page 291–298,Jun. 2005. The device consists of anode, cathode, proton exchange membrane andan external circuit. The MFC convert biodegradable substrate directly intoelectricity. Anode holds the bacteria and the organic matter in an anaerobicenvironment. Cathode is exposed to air.
Bacteria generate protons and electronsas organic substance converts to energy. Microbes use this energy for growth.The electrons are transferred directly to the anode (if mediator-free MFC) andthen to copper electrode via conduction.
Somebacteria are unable to transfer electrons on their own, so a mediator is usedfor electron transfer such as methyl blue, thionine. These are called Redoxmediators. H. J. Mansoorian, A.
H. Mahvi, “Bioelectricity generation usingtwo chamber microbial fuel cell treating wastewater from food processing”, May2013Chemicalenergy is converted into electricity by microbial activity. Microbes releaseelectrons. Oxygen is supplied to the cathode by air source. Materials use inthe electrodes influence the energy produced.
2.4. MFC DESIGN:2.4.1. Double-ChamberMFC Design:Thistype of MFC is used widely. It contains two chambers.
Anode is placed in onechamber whereas cathode in another and is separated by a proton exchangemembrane. The anode chamber is kept oxygen free for anaerobic breakdown processto occur. Though it is widely used by it is still challenging because of itsimpractical configuration.
This set up can accommodate various electrodeshapes, i.e. plane, granular and brush as it has a dedicated chambers for theanode and cathode. It can also use other catholyte besides air, which is anysource of oxygen. According to a recent research document, use of algae(seaweed) enhances the oxygen production due to photosynthetic process in theplant which can be facilitated by this type of MFC configuration.
A. González DelCampo, P. Cañizares, M. A.
Rodrigo, Nov. 2013 Figure 2.4: A Double-Chamber MFC1. 2.
2.1. 2.2. 2.3. 2.
4. 2.4.1. 2.4.2. Single-chamber MFC Design:Aone-compartment MFC eliminates the need for the cathode chamber by exposing thecathode directly to the air.
We are dealing with sand based MFC which has oneChamber. Anode is dug inside the soil and cathode is at the top in exposed airas shown in Figure 3.2.
5. APPLICATIONS OFMFCs:The main applications ofMFCs are:2.5.1. Generation ofBioelectricity:MFCis most recent and fantastic technology that uses wide variety of substrates,materials with bacteria to achieve to produce bio energy despite the fact thatpower level in these systems is relatively low.
Themain objective of MFCs is to achieve a suitable current and power for theapplication in small electrical devices. Itis specially used for sustainable long-term power applications. Rahimnejad andet al. turn on ten LED lamps and one digital clock with fabricated stacked MFCas power source and both devices were successfully operated for the duration of2 days. M. Rahimnejad, A. Ghoreyshi, G. Najafpour,20122.
5.2. Waste WaterTreatment:Differenttype of waste water like sanitary waste, food processing waste water etc. cancontain energy in the form of biodegradable organic matter. MFC can captureenergy as electricity or hydrogen gas. MFCs using specific microbes areexcellent techniques to remove sulfides from wastewater. Up to 90% of the CODcan be removed in some cases.2.
6. MICROBIOLOGICALASPECT:Asfossil fuels are depleting soon we are looking for more sustainable methods andone of them is microbial fuel cell technology for long term energy generation.Microbial fuel cell concept is possible due to exocellular electron transfer.
Microbes are involved in this activity. Main step i.e. electron transfer, isdone by microbes. All the study of these microbes is done in a microbiologylab. Without microbes this process is incomplete.
It does not produce harmfulby products so it is more sustainable. Chapter 3METHODOLOGY3. COMPONENTS:Followingcomponents are used in a basic soil based MFC:· Vessel forassembly ( can be any bucket or container) · Anode: It is whereoxidation occurs and has positive polarity in cell. · Cathode: it iswhere reduction occurs, and it is negatively charged. (The anode and cathode ismade from graphite fibre that is used for conduction as a medium)· Hacker board:board at which the wires are connected to complete the circuit.
· Capacitor: it isused to store the charge for the continuous generation of energy.· LED: light to showthe generation of current.· Alligator clipsand Jumper wires ( to connect circuit with millimeter). · Digital millimeter:to measure current.· Gloves: forprotection. Specimen:soil (sifted) atleast 4 cups or 400 grams. Soil from any area will work, frombackyard or open space. Make sure the soil hasn’t been treated with pesticides.
Apparatusfor handling soil includes: Measuring cups, container, distilled water, tape(for securing).3.1. CONSTRUCTION: 1. Measurethe required amount of soil in cups and first make sure it has no big lumps,rocks and twigs. Free the soil from these extra things.2. Adddistilled water if the soil is too dry, mix until a dough like structure isformed.
3. Nowstart the assembly by taking the anode wire and putting its naked end free ofplastic into the graphite fiber.4. Thewire should not come out of the disk and stay inside. 5. Repeatthe same process with the cathode.6. Takethe soil sample and fill the vessel or container up to 1cm mark and place theanode on top of that mud.
7. Gentlypress the anode on the mud so to eliminate maximum air bubbles under the anode.( removing the air bubbles is important, as the trapped oxygen can prevent theformation of an anaerobic bacteria bio film and reduce the power output of yourMFC)8. Usemore soil and fill up to 5cm more and once again pat the mud to remove excessair.9.
There should be no mud above the cathode. 10. Letthe mud rest for a few minutes and drain the extra water before closing.Figure 3.4: Addition of cathode11.
Wipeoff excess mud from the edges and firmly place the lid taking the anode andcathode wires out from the lid holes. 12. Placethe hacker board on top of the lid and attach the anode to the (-) port andCathode to the (+) port.13. Insertthe capacitor’s prongs into the ports 1 and 2. Capacitor is used to store thecharge that is produced over time.
14. Insertthe LED into ports 5 and 6. With the longer prong in port 5 and shorter in 6.15.
Thecircuit is now complete, it should look like: Figure 3.5: ExternalCircuit16. Oncethe MFC is set up, place it in normal room temperature (about 19-25° Celsius or66-77° Fahrenheit F). The MFC should remain in the same location becausemoving it could disrupt the growth of bacteria.
Also temperature should remainsame or that could also affect the bacterial growth which in turn can affectthe power output. 3.2. PROCEDURE:1. Inthe soil based MFC both anaerobic and aerobic processes take place. The anodeis placed in damp soil where the bacteria multiply and create a bio film on itby providing electrons due to break down of organic or inorganic substratesfrom the soil. The bio film has enzymatic action, it facilitates the transferof electrons.2.
Onthe other side cathode is placed at top, leaving its one side exposed to air(aerobic process). 3. Electronstravel from anode and react with oxygen at the cathode with protons from theanode and create water. The more electricity bacteria is present in a nutrientrich soil, the more current is generated.Figure 3.
6: SoilBased MFC3.3. POWER GENERATION:Thebacteria set to work oxidizing and reducing the organic matter to generate lifesustaining ATP that fuels their energy. Protons, electrons and carbon Dioxideare produced as by products with the anode serving as electron acceptor.Thenewly generated electrons pass from a node to cathode using the wire as bridge.
Finally oxygen present at the cathode combined the hydrogen and electrons toform water, completing the circuit. And the led will harness the electricalcurrent produced.Asper this basic design, the LED blinks after 7 days, if the conditions areperfect then the current can be produced early. Chapter 4RESULT AND DISCUSSIONS4. RESULTS:Weuse mud from lake and set it up for the MFC. And it generated electricity whichilluminated the led light.
This shows that we can use bacteria present in soilfor the production of electricity.4.1. DISCUSSION:The design and optimization ofbio-electrodes and bio fuel cells is not trivial.
This technology bridgesvariety of research areas such as biotechnology, energy harvesting andgeneration, environmental science, micro and nano structured materials.Therefore, innovative and untraditional approaches need to be considered andcombined.Though this technology is quitepromising as a source of renewable energy, it will be some time beforelarge-scale, highly efficient MFCs enter the commercial scene. The differentresearch groups working around the world will definitely overcome theshortcomings being faced today, enthused and motivated by the immediate needfor alternate energy.
Chapter5CONCLUSION AND RECOMMENDATIONSThemore the material offered a better environment for production of electrons themore easily and better is production of electricity. Thereis a good amount of electricity that can be produced in the MFC’s but this canonly be used in the places which lack proper sanitation and electricity becausethe process of generating electricity in theses fuel cells also purifies thewater. In this way MFC’s may be may be helpful, but I cannot see them becomingleading sources of power generation in near future. 5. LIMITATIONS:Wecannot run a sensor or transmitter continuously with the generated power of thecell. That is the main problem of the microbial fuel cell. Other limitation isthat we can only operate MFC at low temperature because microbial reactions areslow at low temperatures.
It is already acknowledged that one of the most importantfactors that limit MFC power output is the reduction reaction that takes placein the cathode. Furthermore, the high over potentials, high ohmic resistances,and low kinetics observed in currently used cathodes have caused many problemsduring the establishment of the oxygen reduction reaction5.1. RECOMMENDATIONS:Wecan made exceptions by increasing the surface of the electrode and also theother solution is to use a suitable power management program.
Data can only betransferred when energy stored in ultra-capacitor for later use. 5.2. ENERGY AND THE CHALLENGE OF GLOBAL CLIMATE CHANGE:Thereis no ‘Magic Bullet’ for meeting our current and future energy needs.
There isno question that the release of stored carbon in fossil fuel is increasing theconcentration of carbon dioxide in atmosphere, with increase from 316 ppmv in1959 to 337 ppmv in 2004. Addressingthe effects of climate change is a top priority of the Energy Department. Asglobal temperatures raise, wildfires, drought, and high electricity demandput stress on the nation’s energy infrastructure. And severe weather the leadingcause of power outages and fuel supply disruption in the United States isprojected to worsen, with eight of the 10 most destructive hurricanes of alltime having happened in the last 10 years. To fight climate change, the EnergyDepartment supports research and innovation that makes fossilenergy technologies cleaner and less harmful to thepeople and the environment. We’re taking responsible steps to cut carbonpollution, develop domestic renewableenergy production and win the global race for cleanenergy innovation.
We’re also working to dramatically increase the efficiencyof appliances, homes, businesses and vehicles.