JP2017183012A - Microbial fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten time until output generation from cell formation without using an external power source and control equipment.SOLUTION: A microbial fuel cell (100) includes: a microorganism-containing layer (5) including at least one current generating bacteria (11), at least one aerobic bacteria (14), at least one methane-producing bacteria (15), and organic matter; an anode electrode (2) which is arranged in contact with the microorganism-containing layer (5) and takes out electrons generated by decomposition of the organic matter due to the current generating bacteria (11); and a cathode electrode (3) receiving the electrons.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a microbial fuel cell.

  Microbial fuel cells used for biocatalysts such as microorganisms are attracting attention as a kind of environmental power generation because they can generate power directly from organic matter.

  For example, the microbial fuel cell disclosed in Patent Document 1 has a configuration in which an anode, a cathode, and a cation exchange membrane disposed between the anode and the cathode 14 are disposed, and electricigenic microorganisms are disposed on the anode. .

JP 2008-288198 A (published November 27, 2008) JP 2004-016023 A (published on January 22, 2004)

  In the conventional microbial fuel cell as shown in Patent Document 1, several days are required until the battery output becomes a certain level or more. This is thought to be because the amount of microorganisms on the negative electrode in the initial state and in the negative electrode tank is small, and it takes time to grow and activate the microorganisms.

  In order to increase the growth rate of microorganisms, for example, a so-called electroculture technique for culturing microorganisms while applying a voltage to a medium as shown in Patent Document 2 has been studied. However, the electroculturing technique requires an external power source and a control device for controlling the power source.

  The present invention has been made in view of the above problems, and an object of the present invention is to shorten the time from battery formation to output generation without using an external power supply or a control device.

  In order to solve the above-described problems, a microbial fuel cell according to one embodiment of the present invention includes a microorganism including at least one type of current-producing bacterium, at least one type of aerobic bacterium, at least one type of methanogen, and an organic substance. A containing layer; a negative electrode that is disposed in contact with the microorganism-containing layer and extracts electrons generated by the decomposition of the organic matter by the current generating bacteria; and a positive electrode that receives the electrons.

  According to one aspect of the present invention, it is possible to shorten the time until power generation by rapidly growing and activating microorganisms in a microbial fuel cell without using a power supply or a control device. .

It is sectional drawing which shows typically the microbial fuel cell which concerns on Embodiment 1 of this invention. It is a figure which shows typically the operation principle of the microbial fuel cell which concerns on the said Embodiment 1. FIG. It is sectional drawing which shows typically the microbial fuel cell which concerns on Embodiment 2 of this invention. It is a figure which shows typically the operation principle of the microbial fuel cell which concerns on the said Embodiment 2. FIG. It is a graph which shows the result of having measured the output voltage after manufacture of the microbial fuel cell which concerns on the said Embodiment 2. FIG. It is sectional drawing which shows typically the microbial fuel cell which concerns on Embodiment 3 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.

Embodiment 1
The following describes Embodiment 1 of the present invention with reference to FIG. 1 and FIG.

(Structure of microbial fuel cell)
FIG. 1 is a cross-sectional view schematically showing a microbial fuel cell 100 according to the present embodiment.

  As shown in FIG. 1, the microbial fuel cell 100 includes a housing 1, and an anode electrode 2 (negative electrode), a cathode electrode 3 (positive electrode), and an ion conductive layer provided in the housing 1. 4, a microorganism-containing layer 5, and an air layer 6. An anode electrode 2 is disposed on the upper side of the housing 1, and a cathode electrode 3 is disposed on the lower side of the housing 1. The microorganism-containing layer 5 is disposed on the upper side and the lower side of the anode electrode 2 so as to be in contact with the anode electrode 2. The air layer 6 is disposed below the cathode electrode 3 so as to be in contact with the cathode electrode 3.

  In the microbial fuel cell 100, if the ion conductive layer 4 is interposed between the anode electrode 2 and the cathode electrode 3, the arrangement of the anode electrode 2, the cathode electrode 3 and the ion conductive layer 4 is not particularly limited. Alternatively, the anode electrode 2 may be in contact with the ion conductive layer 4. Moreover, the anode electrode 2, the cathode electrode 3, and the ion conductive layer 4 may be arrange | positioned in order of the cathode electrode 3, the ion conductive layer 4, and the anode electrode 2 from the upper side. Alternatively, the anode electrode 2, the cathode electrode 3, and the ion conductive layer 4 may be arranged in the order of the cathode electrode 3, the ion conductive layer 4, and the anode electrode 2 in the horizontal direction.

  An anode wiring 20 is electrically connected to the anode electrode 2, and a cathode wiring 30 is electrically connected to the cathode electrode 3. Thereby, the electricity generated by the microbial power generation can be taken out. The anode wiring 20 and the cathode wiring 30 may be electrically connected to a control circuit (not shown), a load (not shown), etc., for example.

(Casing)
Although the material which comprises the housing | casing 1 is not restrict | limited in particular, It is preferable to use the material which has insulation, such as a plastics, for example. Examples of the material include a general resin (or rubber) material, a fluorine-based resin (or rubber) material, a metal material with an insulating film, and a ceramic material. In particular, the material constituting the housing 1 is desirably a fluorine resin (or rubber) material because of its low cost and high corrosion resistance.

(Anode electrode)
The anode electrode 2 is an electrode that uses the anaerobic current-generating bacteria 11 supplied from the microorganism-containing layer 5 as a catalyst and oxidizes the organic fuel contained in the microorganism-containing layer 5. Extract the electrons generated by the decomposition of. As a material constituting such an anode electrode 2, a material having conductivity and excellent corrosion resistance is used. Such a material is preferably a material such as stainless steel, platinum, gold, carbon, nickel, titanium, or a conductive material such as a metal coated with stainless steel, platinum, gold, carbon, nickel, titanium, or the like. Can be mentioned.

  Furthermore, as a material constituting the anode electrode 2, a material having a structure or a shape that can obtain an electrode area larger than a projected area, such as a fine structure or a mesh shape, may be used. Thereby, the adsorption area of microorganisms can be increased and a large generated current can be obtained.

  Alternatively, a material such as carbon felt or carbon paper may be used as the material constituting the anode electrode 2. Thereby, not only can the electrical resistance be low and the amount of microorganisms adsorbed can be increased, but also the cost can be kept lower than that of a noble metal material.

  In the present embodiment, the above-described various materials are exemplified as the material constituting the anode electrode 2, but the material is not limited to these materials.

(Cathode electrode)
The cathode electrode 3 is an electrode that reduces oxygen by supplying electrons taken out by the anode electrode 2 to oxygen in the air and water. As such a cathode electrode 3, a material having conductivity, excellent corrosion resistance, and electrochemically oxygen reducing ability is used. Such a material is preferably a material such as stainless steel, platinum, gold, carbon, nickel, titanium, or a conductive material such as metal coated with stainless steel, platinum, gold, carbon, nickel, titanium, etc. And so on. In addition, a conductive material coated with an enzyme or a microorganism having oxygen reducing ability can be used for the cathode electrode 3.

  Further, as a material constituting the cathode electrode 3, a material having a structure or a shape that can obtain an electrode area larger than a projected area, such as a fine structure or a mesh shape, may be used. Thereby, since the reaction area with oxygen can be increased, a large generated current can be obtained.

  Further, as a material constituting the cathode electrode 3, carbon felt, carbon paper, or the like may be used. Thereby, electrical resistance is low, the electrode area which can be oxygen-reduced can be increased, and it can suppress to lower cost than a noble metal material.

  In the present embodiment, the above-described various materials are exemplified as the material constituting the cathode electrode 3, but the material is not limited to these materials.

  The cathode electrode 3 may be an electron mediator such as ferrocyan ion. Thereby, the exchange of electrons between the electrode and oxygen can be performed smoothly, and the current can be improved. Therefore, an electron mediator (electron mediator) may be arranged around the electrode or fixed to the electrode. However, the electron mediator is not essential for constituting the cathode electrode 3.

(Ion conductive layer)
The ion conductive layer 4 is provided between the anode electrode 2 and the cathode electrode 3 as described above. Here, the ion conductive layer 4 limits the diffusion of oxygen from the cathode electrode 3 side exposed to the air (air layer 6) to the anode electrode 2, and the movement of ions from the anode electrode 2 to the cathode electrode 3 It is a layer having a function that enables the ion conductive film and the electrolyte solution. In addition, the “layer” in the ion conductive layer 4 refers to a layer that extends into the internal space of the housing 1 and includes a plane perpendicular to the vertical direction (vertical direction) of the housing 1. The ion conductive layer 4 having the above function may be formed as long as it can inhibit diffusion and permeation of oxygen from the cathode side in contact with air to the anode. However, considering the low cost, the ability to block oxygen densely, and the ease of adjusting the physical properties of the material by adjusting the salinity and density, the hydrogel-like one is preferable.

  The hydrogel is formed by using a polymer material as a base material and containing a large amount of moisture. Such a hydrogel contains an electrolyte, and is disposed between the cathode electrode 3 and the anode electrode 2 to physically reach the anode electrode 2 of oxygen that enters and diffuses from the cathode electrode 3 side. Since it can block | interrupt and is excellent in ion conductivity, a battery can be comprised, without impairing the internal resistance of the microbial fuel cell 100. FIG. In addition, it is possible to adjust the oxygen permeability, ionic conductivity, and flexibility by adjusting the polymer structure, polymer material, water content, ionic strength, etc. of the hydrogel. It is excellent from the viewpoint of improving the degree of freedom.

  Although FIG. 1 shows a configuration in which the ion conductive layer 4 is formed separately from the anode electrode 2 and the cathode electrode 3, the ion conductive layer 4 includes the anode electrode 2 and the cathode electrode 3. Of course, they may be integrated.

(Anode wiring and cathode wiring)
The material of the anode wiring 20 and the cathode wiring 30 is preferably SUS, titanium, nickel, carbon or the like having high corrosion resistance, and is preferably covered with an insulating resin or the like.

(Microbe-containing layer)
The microorganism-containing layer 5 includes an organic fuel composed of an organic compound (organic substance), and also includes current-generating bacteria 11, aerobic bacteria 14, and methanogens 15. Further, the organic fuel is oxidized by the anode electrode 2, and hydrocarbons such as glucose, acetic acid and lactic acid, amino acids and the like are preferably used.

  The current generating bacteria 11, the aerobic bacteria 14, and the methane generating bacteria 15 included in the microorganism-containing layer 5 may be identified and cultured in advance. Thereby, since the reaction efficiency of microorganisms can be improved more, it is more preferable.

  A higher effect can be obtained by mixing the current-generating bacteria 11, the aerobic bacteria 14, and the methane-producing bacteria 15 previously identified and cultured in a predetermined ratio.

(Current-generating bacteria)
Examples of the current generating bacteria 11 used for the anode electrode 2 include conventionally known appropriate anaerobic current generating bacteria such as Shewanella bacteria, Geobacter bacteria, Rhodoferax ferrireducens, and Desulfobulbus Propionicus. Among them, Shewanella is preferable because it is abundantly contained in a wide range of soils and easily exchanges electrons with the anode electrode 2.

(Methane producing bacteria)
Examples of the methanogen 15 used in the microorganism-containing layer 5 include the Methanobacteriaceae Methanobacteriaceae Methanobacteria, Methanosarcina Methanosarcina, and Methanococcus Methanococcus.

  The methanogenic bacterium 15 consumes carbon dioxide, which is a metabolite of the current-generating bacterium 11, and thereby promotes the metabolism of the current-generating bacterium 11 and the accompanying growth. In addition, the methanogen 15 increases anaerobicity by increasing the partial pressure of methane in the microorganism-containing layer 5 and promotes the activation of the current-generating bacteria 11 mainly composed of anaerobic bacteria.

(Aerobic bacteria)
The aerobic bacterium 14 may be, for example, a facultative aerobic organism such as yeast, and is of the Clenarchiota Aeropyrum, Sulfolobus, Metallosphaera, Sulfurococcus, Juliachiota Ferroplasma, Acidiplasma, Thermogymnomonas, Picrophilus, highly halophilic fungi. Any of the obligate aerobic organisms such as all genera and all genera of Taumarchiota may be used.

  The aerobic bacterium 14 consumes oxygen by its metabolism and generates carbon dioxide, thereby increasing the carbon dioxide partial pressure in the anode tank to increase anaerobicity, and the current generating bacteria 11 mainly composed of anaerobic bacteria and The activation of the methanogen 15 is promoted.

(Reaction of microbial fuel cell)
The operation of the microbial fuel cell 100 will be described with reference to FIG. FIG. 2 is a diagram schematically illustrating the operation principle of the microbial fuel cell 100. In FIG. 2, only the anode electrode 2 and the microorganism-containing layer 5 are shown for convenience.

The anaerobic current-generating bacteria 11 (such as the above-mentioned Shewanella bacteria) contained in the microorganism-containing layer 5 are adsorbed on the anode electrode 2, and hydrocarbons (for example, glucose) contained in the microorganism-containing layer 5 by reaction R11. When the organic fuel such as amino acid or the like is metabolized (oxidized), electrons (e ⁻ ) are released from the electron transfer system to the anode electrode 2 (the oxidized organic fuel becomes an oxidant). The electrons (e ⁻ ) reach the cathode electrode 3 via an external circuit (not shown), and when the cathode electrode 3 receives the electrons, a current flows and power generation occurs.

Protons (H ⁺ ) generated simultaneously with the electrons (e ⁻ ) pass through the microorganism-containing layer 5 and the ion conductive layer 4 and reach the cathode electrode 3. Electrons (e ⁻ ), protons (H ⁺ ), oxygen (O ₂ ) in the air and water react on the cathode electrode 3 to generate water (H ₂ O).

The oxygen that has not been consumed by the cathode electrode 3 passes through the microorganism-containing layer 5 or diffuses in the moisture of the microorganism-containing layer 5 and moves toward the anode electrode 2 side. The aerobic bacterium 14 consumes oxygen in the microorganism-containing layer 5 by the reaction R14. In addition, the methanogen 15 consumes CO ₂ that is a metabolite of the current-producing fungus 11 and generates CH ₄ by the reaction R15. Thereby, the oxygen partial pressure in the microorganism-containing layer 5 is lowered, while the methane partial pressure is increased.

  By the above reaction R14 and reaction R15, the oxygen concentration in the microorganism-containing layer 5 can be lowered. Thereby, since the oxygen concentration is kept low in the vicinity of the anode electrode 2, it is possible to promote the growth of the anaerobic current generating bacteria 11 used as the electrode catalyst.

(Effects of microbial fuel cell)
The microbial fuel cell 100 according to the present embodiment includes a microorganism-containing layer 5 that includes at least one type of current-generating bacteria 11, aerobic bacteria 14, and methanogens 15, respectively. Thereby, the metabolism of the current generating bacteria 11 and the accompanying growth can be promoted. Therefore, the growth rate of the current generating bacteria 11 can be increased, and the output generation time of the microbial fuel cell 100 can be shortened.

  In the conventional microbial fuel cell, only a single type of microorganism is used. The power generation environment required artificial control such as use of a buffer solution, removal of oxygen, and activation by immobilizing microorganisms on electrodes.

  On the other hand, the microbial fuel cell 100 can realize the microbial fuel cell 100 in which the rising of electric power is fast by mutually activating the microbial activities in the microbial-containing layer 5. This is because the presence of a plurality of types of microorganisms promotes metabolism, neutralizes pH, decreases oxygen, and the like, thereby preparing an environment in which the current-generating bacteria 11 can easily act.

  Moreover, in the conventional microbial fuel cell, it was necessary to use the fuel solution which was made into the anaerobic state beforehand. On the other hand, in the microbial fuel cell 100, since the aerobic bacteria 14 consume oxygen, the fuel solution containing oxygen can also be utilized.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIGS. For convenience of explanation, in the present embodiment, constituent elements having functions equivalent to those of the constituent elements in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

(Structure of microbial fuel cell)
FIG. 3 is a cross-sectional view schematically showing the microbial fuel cell 101 according to the present embodiment.

  As shown in FIG. 3, the microbial fuel cell 101 includes an anode electrode 2, a cathode electrode 3, an ion conductive layer 4, a microorganism-containing layer 5, and air in the housing 1, as with the microbial fuel cell 100 according to the first embodiment. A layer 6 is provided. However, the microbial fuel cell 101 is different from the microbial fuel cell 100 in that the microorganism-containing layer 5 includes the redox material X. The redox material X may be provided so as to contact the anode electrode 2.

(Redox substance)
The redox substance X is preferably a substance that can be oxidized and reduced by the current-generating bacteria 11. As the redox substance X, an iron compound, a manganese compound, a cobalt compound, nitric acid, arsenous acid, a cyanide compound, a ferrocene compound, an osmium compound, or the like is used. As the redox substance X, organic compounds such as benzoquinones, naphthoquinones, anthraquinones, porphyrins, anilines, phenazines, flavins, and phenothiazine compounds are used. Further, as the redox substance X, dehydrogenase, oxidase, or redox enzyme having peroxidase activity is used. The oxidoreductase may be used as the redox substance X in combination with the other substances used as the redox substance X.

  The redox material X may be provided in a solid state as long as it is contained in the microorganism-containing layer 5. In this case, more redox agent X can be provided in the microorganism-containing layer 5. Note that the solid redox agent is preferably arranged so as not to contact the anode electrode 2 in order to prevent a leakage current from flowing to the anode electrode 2.

  The redox substance X may be in the form of powder (particles) or a solution in which the powder (particles) are dispersed in a liquid as long as it is contained in the microorganism-containing layer 5. In this case, the redox material X may be supported on the anode electrode 2 in advance.

(Reaction of microbial fuel cell)
FIG. 4 is a diagram schematically showing the operation principle of the microbial fuel cell 101. In FIG. 4, only the anode electrode 2 and the microorganism-containing layer 5 are shown for convenience.

  As shown in FIG. 4, the redox agent X generates a redox reaction R110 conjugated with the reaction R11 of the current generating bacteria 11. Thereby, the metabolism of the current generating bacteria 11 and the accompanying growth can be promoted. Therefore, the growth rate of the current generating bacteria 11 can be increased, and the generation of electric power can be further accelerated.

(Experimental result)
FIG. 5 is a graph showing the results of measuring the output voltage after the production of the microbial fuel cell 101. In this experiment, the transition of the open circuit voltage from the production of the microbial fuel cell 101 to which the iron compound was added as the redox substance X and the microbial fuel cell 100 to which the iron compound was not added was measured.

  As shown in FIG. 5, in the microbial fuel cell 101 in which the iron compound is added as the redox substance X to the microorganism-containing layer 5, an open circuit voltage of 600 mV or more is generated after one day has passed after the production. On the other hand, in the microbial fuel cell 100 in which the oxidation-reduction substance X is not added to the microorganism-containing layer 5, the open circuit voltage has reached 600 mV after 10 days have passed since the production.

  As described above, it was confirmed that the time required until the output of the microbial fuel cell 101 by the redox substance X was shortened.

(Effects of microbial fuel cell)
The microbial fuel cell 101 according to the present embodiment includes a microorganism-containing layer 5 containing current-generating bacteria 11, aerobic bacteria 14, and methanogens 15, and the microorganism-containing layer 5 contains a redox substance X. .

  Thereby, as a result of the oxidation-reduction reaction R110 between the current generating bacteria 11 and the redox substance X, the metabolism of the current generating bacteria 11 and the accompanying growth are promoted. Therefore, the time until the output of the microbial fuel cell 101 is generated can be made shorter than that of the microbial fuel cell 101 described above.

[Embodiment 3]
The following will describe still another embodiment of the present invention with reference to FIG. For convenience of explanation, in this embodiment, components having the same functions as those of the above-described second embodiment are denoted by the same reference numerals, and the description thereof is omitted.

(Structure of microbial fuel cell)
FIG. 6 is a cross-sectional view schematically showing the microbial fuel cell 102 according to the present embodiment.

  As shown in FIG. 6, the microbial fuel cell 102 includes an anode electrode 2, a cathode electrode 3, an ion conductive layer 4, a microorganism-containing layer 5, and air in the housing 1, similarly to the microbial fuel cell 101 according to the first embodiment. A layer 6 is provided. However, the microbial fuel cell 102 differs from the microbial fuel cell 101 in that the microorganism-containing layer 5 includes at least the redox material X1 instead of the redox material X shown in FIG.

(Redox substance)
The redox material X1 is enclosed in a capsule X10. Further, as the redox material X1, the same material as the redox material X in the second embodiment is used.

  The capsule X10 is formed of a substance that decomposes over time. The capsule X10 can be realized by a degradable material that decomposes after a certain amount of time, for example, based on the conditions in the microorganism-containing layer 5. Examples of degradability that can be used include hydrolyzability, photodegradability, and thermal decomposability. Moreover, the timing at which the capsule X10 is decomposed can be arbitrarily set by controlling the composition, thickness, and the like of the degradable material.

(Effects of microbial fuel cell)
After the capsule X10 is put into the microorganism-containing layer 5, the casing 1 is sealed and then decomposed with a time difference, and the inside of the capsule X10 is opened. Thereby, the oxidation-reduction substance X1 can be introduced into the microorganism-containing layer 5 when the housing 1 is in a sealed state. That is, the desired reaction R110 can be generated in the redox material X1 without being affected by the external environment.

(Modification)
The microbial fuel cell 102 may include a plurality of capsules X10, X20, and X30 each enclosing the redox substances X1, X2, and X3. Thereby, the oxidation-reduction substances X1, X2, and X3 can be made different from each other. Further, the timing at which the capsules X10, X20, and X30 are disassembled may be different.

  As a result, it is possible to design the desired redox substances X1, X2, and X3 to be decomposed at a desired timing. Therefore, the redox substances X1, X2, and X3 can be reacted without affecting the mutual reaction.

  The redox materials X1, X2, and X3 may be the same material. By providing a time difference in the timing at which the capsules X10, X20, X30 are disassembled, it becomes possible to react in stages.

[Summary]
The microbial fuel cell according to aspect 1 of the present invention includes a microorganism-containing layer 5 containing at least one type of current-generating bacteria 11, at least one type of aerobic bacteria 14, at least one type of methanogen 15 and organic matter, A negative electrode (anode electrode 2) that is arranged in contact with the microorganism-containing layer 5 and extracts electrons generated by the decomposition of the organic matter by the current generating bacteria 11 and a positive electrode (cathode electrode 3) that receives the electrons are provided.

According to the above configuration, current generating bacteria 11, by decomposing organic substances contained in the microorganism-containing layer 5, generates the CO _2, and generates electrons and ions. Electricity is generated by taking out the electrons at the negative electrode and receiving them at the positive electrode. The aerobic bacteria 14 consumes oxygen in the microorganism-containing layer 5. The methane producing bacterium 15 produces methane from CO ₂ produced by the current generating bacterium 11. Thereby, since the oxygen concentration in the microorganism-containing layer 5 decreases, the oxygen concentration is kept low in the vicinity of the negative electrode. Therefore, it is possible to promote the growth of the anaerobic current generating bacteria 11 used as an electrode catalyst. Therefore, the time required for generating the output of the microbial fuel cell can be shortened.

  In the microbial fuel cell according to aspect 2 of the present invention, in the above aspect 1, the microorganism-containing layer 5 may contain redox substances X and X1.

  According to said structure, as a result of the oxidation-reduction reaction of the electric current generation microbe 11 and the redox substances X and X1, metabolism of the electric current generation microbe 11 and the growth accompanying it are promoted. Therefore, the generation of electric power can be accelerated.

  In the microbial fuel cell according to Aspect 3 of the present invention, in the above Aspect 2, the redox substances X and X1 may contain an iron compound.

  According to said structure, the oxidation reduction reaction by an iron compound can accelerate | stimulate the metabolism of the electric current generation microbe 11, and the growth accompanying it more. Therefore, the effect of shortening the time required for generating power can be enhanced.

  The microbial fuel cell according to aspect 4 of the present invention may be arranged such that the iron compound is provided in a solid state and does not contact the negative electrode in aspect 3 described above.

  According to said structure, it can prevent that the leakage current to a negative electrode generate | occur | produces.

  In the microbial fuel cell according to Aspect 5 of the present invention, in any of Aspects 2 to 4, the redox substances X and X1 may contain an oxidoreductase.

  The oxidation-reduction substance X1 may be enclosed in a capsule X10 that decomposes after a while after being introduced into the microorganism-containing layer 5.

  According to the above configuration, when the capsule X10 is decomposed after being put into the microorganism-containing layer 5, the redox substance X1 in the capsule X10 is released to the microorganism-containing layer 5. Thereby, a desired oxidation-reduction reaction can be caused in the oxidation-reduction substance X1 without being affected by the external environment.

[Additional Notes]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

2 Anode electrode (negative electrode)
3 Cathode electrode (positive electrode)
5 Microorganism-containing layer 6 Air layer 11 Current generating bacteria 14 Aerobic bacteria 15 Methanogenic bacteria 100 Microbial fuel cell 101 Microbial fuel cell 102 Microbial fuel cells X, X1 to X3 Redox substances X10, X20, X30 Capsules

Claims (6)

A microorganism-containing layer comprising at least one type of current generating bacteria, at least one type of aerobic bacteria, at least one type of methanogen, and organic matter;
A negative electrode that is disposed in contact with the microorganism-containing layer and extracts electrons generated by the decomposition of the organic matter by the current-generating bacteria;
A positive electrode for receiving the electrons;
A microbial fuel cell comprising:   The microbial fuel cell according to claim 1, wherein the microorganism-containing layer contains a redox material.   The microbial fuel cell according to claim 2, wherein the oxidation-reduction substance contains an iron compound.   The microbial fuel cell according to claim 3, wherein the iron compound is provided in a solid state and is disposed so as not to contact the negative electrode.   The microbial fuel cell according to any one of claims 2 to 4, wherein the redox material contains an oxidoreductase.   The microbial fuel cell according to any one of claims 2 to 5, wherein the oxidation-reduction substance is enclosed in a capsule that decomposes after a while after being introduced into the microorganism-containing layer.

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