Microbial fuel cell

JAWAHAR NAVODAYA VIDYALAYA SARAIPALI, MAHASAMUND

(CHHATTISGARH)

Bio-electricity production by Microbial Fuel Cell

Presented by

KKpatel

Bio-electricity production by

Microbial Fuel Cell Student :- Tuleshwar Sagar School:-

JNV Saraipali (Mahasamund)

Teacher:- S.K.Pradhan

K.K.Patel

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Introduction:-IT is evident that humankind is increasingly dependent onenergy with the advancement of science and technology.The present-day energy scenario in India and around theglobe is precarious, thus driving to the search of alternativeto fossil fuels. Increasing energy consumption creates unbalancedenergy management and requires power sourcesthat are able to sustain for longer periods1. Trapping renewableenergy from waste organic sources is the presenttrend of active research. In this direction, bioelectricitygeneration through microbial fuel cells (MFCs) using avariety of substrates, including wastewater is being studiedextensively.

Scientific Principle involved:-A microbial fuel cell is a device that converts chemical energy to electrical energy by the catalytic reaction of microorganisms (Allen and Bennetto, 1993). A typical microbial fuel cell consists of anode and cathode compartments separated by a cation specific membrane. In

the anode compartment, fuel is oxidized by microorganisms, generating electrons and protons. Electrons are transferred to the cathode compartment through an external electric circuit, and the protons are transferred to the cathode compartment through the membrane. Electrons and protons are consumed in the cathode compartment, combining with oxygen to form water. In general, there are two types of microbial fuel cells, mediator and mediator-less microbial fuel cells. Biological fuel cells take glucose and methanol from food scraps and convert it into hydrogen and food for the bacteria.

Mediator Microbial Fuel Cell

Most of the microbial cells are electrochemically inactive. The electron transfer from microbial cells to the electrode is facilitated by mediators such as thionine, methyl viologen, methyl blue, humic acid, neutral red and so on (Delaney et al., 1984; Lithgow et al., 1986). Most of the mediators available are expensive and toxic.

Mediator-less Microbial Fuel Cell

Mediator-less microbial fuel cells have been engineered at the Korea Institute of Science and Technology [1], by a team led by Kim, Byung Hong[2]. A mediator-less microbial fuel cell does not require a mediator but uses electrochemically active bacteria to transfer electrons to the electrode (electrons are carried directly from the bacterial respiratory enzyme to the electrode). Among the electrochemically active bacteria are, Shewanella putrefaciens (Kim et al., 1999a), Aeromonas hydrophila (Cuong et al., 2003), and others.

Mediator-less MFCs are a much more recent development and due to this the factors that affect optimum operation, such as the bacteria used in the system, the type of ion membrane, and the system conditions such as temperature, are not particularly well understood. Bacteria in mediator-less MFCs typically have electrochemically-active redox

enzymes such as cytochromes on their outer membrane that can transfer electrons to external materials (Min, et al., 2005).

General priniciples of microbial fuel cells A microbial fuel cell (MFC) converts chemical energy, available in a bio-convertible substrate, directly into electricity. To achieve this, bacteria are used as a catalyst to convert substrate into electrons.

Bacteria are very small (size appr. 1 µm) organisms which can convert a huge variety of organic compounds into CO2, water and energy. The micro-organsisms use the produced energy to grow and to maintain there metabolism. However, by using a MFC we can harvest a part of this microbial energy in the form of electricity.A MFC consists of an anode, a cathode, a proton or cation exchange membrane and an electrical ciruit.

A General layout of a MFC in which in the anodic compartment the bacteria can bring about oxidative conversions while in the cathodic compartment chemical and microbial reductive processes can occur

The bacteria live in the anode and convert a substrate such as glucose, acetate but also waste water into CO2, protons and electrons. Under aerobic conditions, bacteria use oxygen or nitrate as a final electron acceptor to produce water. However, in the anode of a MFC, no oxygen is present and bacteria need to switch from their natural electron acceptor to an insoluble acceptor, such as the MFC anode. Due to the ability of bacteria to transfer electrons to an insoluble electron acceptor, we can use a MFC to collect the electrons originating from the microbial metabolism. The electron transfer can occur either via membrane-associated components, soluble electron shuttles or nano-wires.

The electrons then flow through an electrical circuit with a load or a resistor to the cathode. The potential difference (Volt) between the anode and the cathode, together with the flow of electrons (Ampere) results in the generation of electrical power (Watt).

The protons flow through the proton or cation exchange membrane to the cathode.

At the cathode, an electron acceptor is chemically reduced. Idealy, oxygen is reduced to water. To obtain a sufficient oxygen reduction reaction (ORR) rate a Platina-catalyst has to be used. However, many researchers have tried to used other non-noble metal catalysts.

Generating electricity:-

When micro-organisms consume a substrate such as sugar in aerobic conditions they produce carbon dioxide and water. However when oxygen is not present they produce carbon dioxide, protons and electrons as described below (Bennetto, 1990):

C12H22O11 + 13H2O ---> 12CO2 + 48H+ + 48e-

In first Chamber

Microbial fuel cells use inorganic mediators to tap into the electron transport chain of cells and steal the electrons that are produced. The mediator crosses the outer cell lipid membranes and plasma wall; it then begins to liberate electrons from the electron transport chain that would normally be taken up by oxygen or other intermediates. The now-reduced mediator exits the cell laden with electrons that it shuttles to an electrode where it deposits them; this electrode becomes the electro-generic anode (negatively charged electrode). The release of the electrons means that the mediator returns to its original oxidised state ready to repeat the process. It is important to note that this can only happen under anaerobic conditions, if oxygen is present then it will collect all the electrons as it has a greater electronegativity than the mediator.

A number of mediators have been suggested for use in microbial fuel cells. These include natural red, methylene blue, thionine or resorfuin ..

This is the principle behind generating a flow of electrons from most micro-organisms. In order to turn this into a usable supply of electricity this process has to be accommodated in a fuel cell.

In order to generate a useful current it is necessary to create a complete circuit, not just shuttle electrons to a single point.

The mediator and micro-organism, in this case yeast, are mixed together in a solution to which is added a suitable substrate such as glucose. This mixture is placed in a sealed chamber to stop oxygen entering, thus forcing the micro-organism to use anaerobic respiration. An electrode is placed in the solution that will act as the anode as described previously.

In the second chamber

In the second chamber of the MFC is another solution and electrode. This electrode, called the cathode is positively charged and is the equivalent of the oxygen sink at the end of the electron transport chain, only now it is external to the biological cell. The solution is an oxidizing agent that picks up the electrons at the cathode. As with the electron chain in the yeast cell, this could be a number of molecules such as oxygen. However, this is not particularly practical as it would require large volumes of circulating gas. A more convenient option is to use a solution of a solid oxidizing agent.

Connecting the two electrodes is a wire (or other electrically conductive path which may include some electrically powered device such as a light bulb) and completing the circuit and connecting the two chambers is a salt bridge or ion-exchange membrane. This last feature allows the protons produced, as described in Eqt. 1 to pass from the anode chamber to the cathode chamber.

The reduced mediator carries electrons from the cell to the electrode. Here the mediator is oxidized as it deposits the electrons. These then flow across the wire to the second electrode, which acts as an electron sink. From here they pass to an oxidising material.

Materials Used for constructioni) Two heavy duty plastic bottles with sealable lids

ii) Short section of plastic pipe (polyethylene or PVC) for salt bridgeiii) Means to connect pipe to bottles (plastic flanges, end caps with holes drilled)iv) Agar Agarv) Salt (NaCl, KCl, KNO3, etc)vi) Graphite rodvii)Bacteria 3 viii) Food for the bacteria 4

ix) Fish tank air pump with plastic tubingx) Sealing materials (epoxy)xi) Copper wire (plastic coated)xii) Wires with alligator clipsxiii) Multimeter for electrical measurements

Construction & working of Microbial Fuel Cell

1. Collect materials

2. Connect end caps of flanges to bottles

* Epoxy end caps or flanges to sides of plastic bottles. * After epoxy has hardened, drill or cut holes through plastic bottles to allow for contact between liquid and the salt bridge.

3. Assemble Salt Bridge

* Dissolve agar into boiling water (at concentration of 100g/L).* Add salt to the agar/water mixture while the mixture is still hot.* Seal one end of plastic pipe.* Pour agar/salt mixture into plastic pipe while it is still warm and before it begins to thicken.* Allow the agar/salt mixture to cool and solidify.

4. Assemble electrodes

* Connect copper wire to piece of carbon cloth.* Use epoxy to fasten the wire to the carbon cloth and to help protect from corrosion. * Test electrodes with multimeter - there should be a small amount of resistance between a point on the carbon cloth and the end of the wire opposite the cloth.* For anode, pass wire through a hole in the bottle lid and seal with epoxy. Cathode chamber does not necessarily need a lid.

5. Assemble MFC

* Connect salt bridge between the two plastic bottles and use epoxy to seal.

Running of MFC1. Add inoculum (wastewater, anaerobic benthic sediments) to anode chamber

2. Add conductive solution (saltwater) to cathode chamber

3. Insert anode (connected to lid) into anode bottle. Add cathode to cathode bottle. Begin bubbling air in cathode bottle with fish pump.

4. Connect external circuit through a resistor, and start measuring voltage.

ConclusionThis study documented the feasibility of bioelectricitygeneration from anaerobic wastewater treatment using aMFC fabricated with low-cost anode materials (non-coatedplain graphite electrodes), without any toxic mediators(aerated cathode and mediator less anode). Acidophilic(anode pH of 5.5) conditions maintained during the experimentsusing anaerobic mixed consortia also helped inbioelectricity generation along with effective substrate

removal. The procedurewas cost-effective and environmentally sound and sustainable due to utilization of wastewater as substrate.Further, power was generated in situ along with wastewatertreatment, utilizing low-cost and non-coated electrodesand mediatorless anode. This process could beeffectively integrated to wastewater treatment plant,wherein renewable energy could be generated fromwastewater in addition to treatment. The dual activitycould significantly reduce the cost associated with the

current wastewater treatment methods.

ACKNOWLEDGEMENTACKNOWLEDGEMENT I am thankful first respected S.K.Pradhan sir I am thankful first respected S.K.Pradhan sir who inspired me to make Microbial Fuel Cell , who inspired me to make Microbial Fuel Cell , Which I really enjoyed doing .Thanks are also due to Which I really enjoyed doing .Thanks are also due to respected,Anima Baxla Madam, V.K.Patel Sir who respected,Anima Baxla Madam, V.K.Patel Sir who created interest in me & constantly encouraged me created interest in me & constantly encouraged me to do this projectto do this project I am most thankful to our Principal madam I am most thankful to our Principal madam

Manju Sharma , I wouldn’t have been able to Manju Sharma , I wouldn’t have been able to complete the project without their valuable complete the project without their valuable guidance .guidance .

Mention must be made of my friend SurendraMention must be made of my friend Surendra who tirelessly helped me in completing the work.who tirelessly helped me in completing the work.

Prepared by Kk patel

Guided Teacher Guided Teacher PrincipalPrincipal

Refrences :-Refrences :-Webcites:-Webcites:- i) i) www.psu.eduwww.psu.edu ii) ii) www.engr.psu.eduwww.engr.psu.edu iii) iii) www.microbialfuelcell.orgwww.microbialfuelcell.org iv) iv) www.live.psu.edu/story/18683www.live.psu.edu/story/18683BooksBooks:: i) Current Science,vol.92no. 12i) Current Science,vol.92no. 12 ii) Logan, B.E. feature articleii) Logan, B.E. feature article iii) power sources 2006 iii) power sources 2006 iv) Bioresour.Technol.2007 ,98,2879-2885iv) Bioresour.Technol.2007 ,98,2879-2885

1. S.K.Pradhan (Smt. Manju Sharma)2. V.K.Patel

Other information about mfc

New fuel cell uses germs to generate electricity

The new "microbial fuel cell," an early prototype, cannot generate enough power to run an appliance, but it can operate virtually indefinitely without interruption, and is far more efficient than anything like it ever built.

"We are not going to be adding to the power grid at any significant rate soon, but with an electric lawn mower, you could use the leaves and clippings to power up the battery for next week."

The bacteria in the battery generate electrical current when they feed on sugars, which are found virtually everywhere in nature. The technology could create electricity from a wide variety of materials, from human sewage to compost.

As it has become clear that the world will need energy alternatives, we have turned to the idea of finding new ways of releasing the enormous amount of energy trapped in plants and other organic matter. This is the idea behind ethanol, a fuel made from corn. But instead of using organic matter to make a fuel.

The battery relies on a colony of tiny bacteria, called Rhodoferax ferrireducens, first brought up from underground by a research drill in Oyster Bay, Va. The bacterium is unusual because it is able to completely break down sugars without using oxygen. In its natural environment, the bacterium breaks down sugars for energy and deposits electrons on iron as a byproduct.

We placed these bacteria in a closed glass container with a sugar solution and a graphite electrode. As the bacteria ate the sugar, they took up residence on the electrode and began depositing electrons on it.

When we connected a wire between the electrode and a separate electrode exposed to the air, a current started to

flow.

We have built similar devices but they have been far less efficient at converting the sugar to electricity. Of all the electrons that could theoretically be moved by the process, the battery captured more than 80 percent, compared with less than 1 percent for a previous battery, according to the paper.

It is interested in the device because it could be used to run low-power antennas in remote locations without the need for replacing batteries. The electrode could be placed at the

bottom of a pile of waste, along with a colony of the bacteria, which would thrive in the sugar-rich, oxygen-poor environment.

The biggest problem right now is the amount of power generated. The test battery generates just enough energy to power a calculator or a single Christmas tree light,. Simply changing the electrode, so that more of the microbes can touch it, can increase the amount of power it generates.

We have exploring the idea of genetically engineering the microbe so that the colony delivers even more electrons to the electrode, boosting the power.

We hopes the technology could be used to generate electricity from sewage or other waste.

There is a scene in `Back to the Future' where they throw a banana in the car and off it goes, We are not at that stage yet, but this is a big step from what these fuel cells were able to do before."

Uses

Power generation

Microbial fuel cells have a number of potential uses. The first and most obvious is harvesting the electricity produced for a power source. Virtually any organic material could be used to ‘feed’ the fuel cell. MFCs could be installed to waste water treatment plants. The bacteria would consume waste material from the water and produce supplementary power for the plant. The gains to be made from doing this are that MFCs are a very clean and efficient method of energy production. A fuel cell’s emissions are well below regulations (Choi, et al., 2000). MFCs also use energy much more efficiently than standard combustion engines which are limited by the Carnot Cycle. In theory an MFC is capable of energy efficiency far beyond 50% (Yue & Lowther, 1986).

However MFCs do not have to be used on a large scale, as the electrodes in some cases need only be 7 μm thick by 2 cm long (Chen, et al., 2001). The advantages to using an MFC in this situation as opposed to a normal battery is that it uses a renewable form of energy and would not need to be recharged like a standard battery would. In addition to this they could operate well in mild conditions, 20°C to 40°C and also at pH of around 7 (Bullen, et al., 2005). Although more powerful than metal catalysts, they are currently too unstable for long term medical applications such as in pacemakers (Biotech/Life Sciences Portal).

Further uses

Since the current generated from a microbial fuel cell is directly proportional to the strength of wastewater used as the fuel, an MFC can be used to measure the strength of wastewater (Kim, et al., 2003). The strength of wastewater is commonly evaluated as biochemical oxygen demand (BOD) values. BOD values are determined incubating samples for 5 days with proper source of microbes, usually activate sludge collected from sewage works. When BOD values are used as a real time control parameter, 5 days' incubation is too long. An MFC-type BOD sensor can be used to measure real time BOD values. Oxygen and nitrate are preferred electron acceptors over the electrode reducing current generation from an MFC. An MFC-type BOD sensors underestimate BOD values in the presence of these electron acceptors. This can be avoided by inhibiting aerobic and nitrate respirations in the MFC using terminal oxydase inhibitors such as cyanide and azide [Chang, I. S., Moon, H., Jang, J. K. and Kim, B. H. (2005) Improvement of a microbial fuel cell performance as a BOD sensor using respiratory inhibitors. Biosensors and Bioelectronics 20, 1856-1859.] This type of BOD sensor is commercially available

IT is evident that humankind is increasingly dependent onenergy with the advancement of science and technology.The present-day energy scenario in India and around theglobe is precarious, thus driving to the search of alternativeto fossil fuels. Increasing energy consumption creates unbalancedenergy management and requires power sourcesthat are able to sustain for longer periods1. Trapping renewableenergy from waste organic sources is the presenttrend of active research2–7. In this direction, bioelectricitygeneration through microbial fuel cells (MFCs) using avariety of substrates, including wastewater is being studiedextensively2,5–17.It is well known that microorganisms can produce fuelssuch as ethanol, methane and hydrogen from organic matter.More recently, it has been reported that microorganisms

can also convert organic matter into electricity using MFCs2–7.MFC is a biochemically catalysed system, which generateselectricity by oxidizing biodegradable organic matter in thepresence of either fermentative bacteria or enzymes2–7,18–20.The biocatalyst present in the anode chamber of MFCgenerates electrons (e–) and protons (H+) through anaerobicrespiration of organic substrates. Electron transfer occursthrough the electrode (anode) integrated with an externalcircuit to the cathode. Protons diffuse through the protonexchange membrane (which separates the cathode and anodechamber) into the cathode chamber, where they combinewith the electron acceptor. The potential difference betweenthe respiratory system and electron acceptor generates thecurrent and voltage needed to generate electricity2. Harvestingelectricity from organic wastes through MFC is an

attractive source of energy as organic waste is ‘carbonneutral’and oxidation of organic matter only releases recentlyfixed carbon back into the atmosphere4. Accordingto Lovley4, MFC could fill a niche that is significantlydifferent from that of the better known abiotic hydrogenandmethanol-driven fuel cells. Abiotic fuel cells requirehigh temperatures and expensive catalysts which are toxic,to promote oxidation of the electron donors21. Naturallyoccurring microorganisms catalyse the oxidation of fuelsin MFC at room temperature and could potentially be designed to function at any temperature at which microbial life is possible4,6. MFC can be considered as a promising alternative for the harnessing of electrical energy fromvarious substrates using different cell configurations, andelectron transfer mechanisms9,17,20,22–25.Presently, research on MFCs using wastewater as substrate

is in the initial stages of laboratory evaluation aroundthe world. The reported work so far is mainly based on using the monoculture at laboratory level12,20,21,26. A few studieswere reported on using wastewater as substrate for production of electricity2–17,25. Substantial technical and engineering challenges still remain to achieve sustainable electricity production at full scale. The function and efficiency of MFCs with respect to power generation are generally dependent on factors such as nature of carbon source used7,20, fuel-cell configuration (single/multiple chamber), dimensions and volume26,27, nature and type of electrode15,19, electron acceptors (mediators) present in the cathode chamber15,28, electrolytes used22, operating temperature24, nature of inoculum (biocatalyst) used in the anode chamber15,28, and nature of the proton exchange membrane25. The basic aim of the present study is to design MFCs employing low-cost materials without using toxic mediators, which will have the possibility to be implemented in the wastewater treatment plants in the economical perspective. The designed MFC (graphite electrode without any coating) employing aerated cathode and mediatorless anode was evaluated at acidophilic conditions

using anaerobic mixed consortia to enumerate the influence of substrate/organic loading rate (OLR) on the performanceof the MFC in terms of bioelectricity generation from anaerobic wastewater treatment.

ConclusionThis study documented the feasibility of bioelectricitygeneration from anaerobic wastewater treatment using aMFC fabricated with low-cost anode materials (non-coatedplain graphite electrodes), without any toxic mediators(aerated cathode and mediatorless anode). Acidophilic(anode pH of 5.5) conditions maintained during the experimentsusing anaerobic mixed consortia also helped inbioelectricity generation along with effective substrateremoval. The substrate loading rate showed significantinfluence on the overall performance of MFC with respectto power generation and substrate removal. COD removal

efficiency observed in the anode chamber enumerated thefunctioning of MFC as alternative wastewater treatmentunit in addition to renewable energy generation. The procedurewas cost-effective and environmentally sound and sustainable due to utilization of wastewater as substrate. Further, power was generated in situ along with wastewater treatment, utilizing low-cost and non-coated electrodes and mediatorless anode. This process could beeffectively integrated to wastewater treatment plant,wherein renewable energy could be generated fromwastewater in addition to treatment. The dual activitycould significantly reduce the cost associated with thecurrent wastewater treatment methods. =================================================================== presented by KKPATEL(tgt

science)