Microbial fuel cells

Abstract

A microbial fuel cell that can produce a higher power output than conventional technologies is provided. [Solution] The microbial fuel cell 1 comprises soil 11 artificially mixed with metal species, an anode electrode 12 placed in the anaerobic environment of the soil 11, and a cathode electrode 13 placed in the aerobic environment. Iron is mixed into the soil 11 as an example of a metal species that is thought to improve electrical conductivity, thereby increasing the power output of the microbial fuel cell 1. Furthermore, chicken manure charcoal, an example of biochar derived from livestock waste, is also mixed into the soil 11. The chicken manure charcoal functions as a nutrient source for microorganisms and contributes to further improving power output by providing an environment in which the microorganisms can settle.

Description

[Technical Field]

[0001] The present invention relates to a microbial fuel cell. [Background technology]

[0002] In recent years, microbial fuel cells have been attracting attention as a renewable energy source that can replace fossil fuels and nuclear power. Microbial fuel cells generate electricity by decomposing organic matter through metabolic reactions in microorganisms and using the electrons obtained in the process. Microbial fuel cells have the advantages of being environmentally friendly, weather-independent, and less expensive than solar or wind power generation.

[0003] Patent document 1 is an example of a patent document related to microbial fuel cells. Patent document 1 describes a microbial fuel cell that has a configuration in which a negative electrode is placed in a sludge layer, a positive electrode is placed in a water layer, and protons are transferred through the interface between the sludge layer and the water layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-84541 Summary of the Invention [Problem to be solved by the invention]

[0005] Microbial fuel cells have the problem of not having sufficient power output.

[0006] In view of the above circumstances, the present invention provides a microbial fuel cell that can provide a higher power output than conventional techniques. [Means for solving the problem]

[0007] In a first aspect, the present invention provides a microbial fuel cell comprising soil artificially contaminated with metal species, an anode electrode placed in the anaerobic environment of the soil, and a cathode electrode placed in the aerobic environment of the soil.

[0008] The microbial fuel cell according to the first aspect can obtain a higher power output than the conventional technology.

[0009] The present invention provides, as a second aspect, a microbial fuel cell according to the first aspect, wherein biochar is mixed into the soil.

[0010] The microbial fuel cell according to the second aspect can produce a higher power output than when the soil is not mixed with biochar.

[0011] In a third aspect, the present invention provides a microbial fuel cell according to the first aspect, wherein the metal species includes iron metal species.

[0012] According to the microbial fuel cell of the third aspect, by using a metal species of iron, which is an inexpensive metal, it is possible to realize a microbial fuel cell that is inexpensive and has a high output compared to conventional technologies.

[0013] The present invention provides, as a fourth aspect, the microbial fuel cell according to the third aspect, wherein the biochar contains a carbonized material derived from livestock manure.

[0014] The microbial fuel cell according to the fourth aspect can obtain a higher power output than when biochar not derived from livestock excrement is used.

[0015] The present invention provides, as a fifth aspect, a microbial fuel cell according to the fourth aspect, wherein the carbonized material derived from livestock excrement includes chicken manure charcoal.

[0016] According to the microbial fuel cell of the fifth aspect, chicken manure, which is disposed of in greater amounts than livestock excrement other than chicken manure, can be effectively utilized. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing the configuration of a microbial fuel cell according to one embodiment. [Figure 2] Graph showing the results of one experiment demonstrating that incorporating iron into soil increases the power output of a microbial fuel cell. [Figure 3] Graph showing experimental results showing that mixing chicken manure charcoal into soil increases the power output of a microbial fuel cell. [Figure 4] Graph showing the results of an experiment demonstrating that the incorporation of carbonized material derived from livestock waste into soil increases the power output of a microbial fuel cell more than the incorporation of carbonized material not derived from livestock waste. [Figure 5] This is a graph showing the results of an experiment demonstrating that mixing carbonized material derived from livestock waste into soil increases the power output of microbial fuel cells stably over the long term. DETAILED DESCRIPTION OF THE INVENTION

[0018] 1 is a diagram showing the configuration of a microbial fuel cell 1 according to one embodiment of the present invention. The microbial fuel cell 1 includes a container 10, soil 11 contained within the container 10, an anode electrode 12 disposed inside the soil 11, a cathode electrode 13 disposed above the soil 11, an anode-side conducting wire 14 having one end electrically connected to the anode electrode 12, a cathode-side conducting wire 15 having one end electrically connected to the cathode electrode 13, and a lid 16 that closes the upper opening of the container 10.

[0019] Note that soil 11 requires sufficient moisture for microorganisms to live, and in Fig. 1, the surface of soil 11 is covered with water 17. However, the surface of soil 11 does not necessarily have to be covered with water.

[0020] The container 10 is made of, for example, polypropylene, but containers made of other materials may also be used. For example, when constructing the microbial fuel cell 1 in natural soil, agricultural soil, or the like, the container 10 may be a cylindrical body without a bottom, may have holes in the sides or bottom, or may not even be used at all.

[0021] The soil 11 provides a habitat for microorganisms that break down organic matter and release electrons.

[0022] Iron is artificially mixed into the soil 11. The iron mixed into the soil 11 is, for example, finely chopped steel wool, but iron scrubbers, iron powder, etc. may also be used. Also, used iron powder oxidation heating elements (disposable hand warmers) may also be used, which is an effective use of waste.

[0023] The iron mixed into the soil 11 is thought to serve as fuel for the iron-reducing bacteria in the soil 11 to reduce iron and release electrons toward the anode electrode 12, as well as to increase the conductivity of the soil 11, making it easier for the electrons released by the microorganisms to move to the anode electrode 12. Therefore, instead of or in addition to iron, metals other than iron may be mixed into the soil 11. However, iron is preferable because it is cheaper than other metals.

[0024] In addition, the soil 11 contains metallic iron (Fe 0 Instead of or in addition to iron, metal species other than the simple metal may be mixed in. For example, metal compounds such as divalent iron oxide (FeO) and trivalent iron oxide (Fe2O3), divalent iron ions (Fe 2+ ), trivalent iron ions (Fe 3+ ), iron complexes ([Fe(CN)6] 4- , [Fe(H2O)6] 3+ Metal species other than iron (copper, etc.) may be mixed into the soil 11 instead of or in addition to the iron species.

[0025] In addition to iron, soil 11 is also mixed with chicken manure charcoal. Chicken manure charcoal contains various components (phosphorus, potassium, etc.) that serve as nutrients for microorganisms in soil 11 and has the effect of increasing the activity of microorganisms in soil 11. Furthermore, because chicken manure charcoal is porous, it provides an environment suitable for the settlement and proliferation of microorganisms, thereby increasing microbial activity in the soil. Furthermore, chicken manure charcoal increases the carbon concentration of soil 11 and also serves to increase the electrical conductivity of soil 11. Therefore, instead of or in addition to chicken manure charcoal, charcoal derived from livestock excrement other than chicken manure charcoal (such as cow manure charcoal or pig manure charcoal) may be mixed into soil 11. Furthermore, instead of or in addition to charcoal derived from livestock excrement, biochar not derived from livestock excrement (such as wood charcoal or bamboo charcoal) may be mixed into soil 11.

[0026] However, among these biochars, chicken manure charcoal is superior to biochar not derived from livestock waste in that it contains a large amount of various components that serve as nutrients for microorganisms in soil. 11 Chicken manure charcoal is also desirable from the perspective of effective waste utilization, as it uses chicken manure, which is discarded in larger quantities than cow manure charcoal, pig manure charcoal, etc.

[0027] The anode electrode 12 is an electrode placed in the anaerobic environment of the soil 11 and receives electrons released by microorganisms in the soil 11 .

[0028] The cathode electrode 13 is an electrode placed in the aerobic environment of the soil 11, and causes a reduction reaction using electrons supplied from the anode electrode 12 through the anode side conductor 14 and the load L and oxygen in the air or water.

[0029] The anode electrode 12 and the cathode electrode 13 are made of, for example, carbon felt, but other materials (for example, graphite-coated iron plates, etc.) may also be used.

[0030] The anode side conductor 14 forms a path through which the electrons received by the anode electrode 12 flow toward the load L.

[0031] The cathode-side conducting wire 15 constitutes a path through which electrons that have passed through the anode electrode 12 and the load L flow toward the cathode electrode 13.

[0032] The lid 16 serves to reduce the influence of the outside world on the environment inside the container 10. However, depending on the environment in which the microbial fuel cell 1 is used, the lid 16 may not be provided. The lid 16 has holes through which the anode side conducting wire 14 and the cathode side conducting wire 15 pass while covering the upper opening of the container 10.

[0033] A distinctive feature of the microbial fuel cell 1 compared to similar microbial fuel cells according to the prior art is that iron (an example of a metal) and chicken manure charcoal (an example of biochar, particularly charcoal derived from livestock waste) are mixed into the soil 11. This feature allows the microbial fuel cell 1 to produce a higher power output than similar microbial fuel cells according to the prior art.

[0034] FIG. 2 is a graph showing the results of an experiment demonstrating that mixing iron into soil 11 increases the power output of microbial fuel cell 1. Graph G1 shown in FIG. 2 shows the change over time in the maximum ideal power of microbial fuel cell 1 using soil 11 without iron mixing. On the other hand, graph G2 shown in FIG. 2 shows the change over time in the maximum ideal power of microbial fuel cell 1 using soil 11 with iron mixing. In both microbial fuel cells 1, 50% chicken manure charcoal was mixed into the soil 11. It can be seen from FIG. 2 that mixing iron into soil 11 significantly increases the power output of microbial fuel cell 1.

[0035] FIG. 3 is a graph showing the results of an experiment demonstrating that mixing chicken manure charcoal into the soil 11 increases the power output of the microbial fuel cell 1. Graph G3 shown in FIG. 3 shows the change over time in the maximum ideal power of the microbial fuel cell 1 using soil 11 without chicken manure charcoal. Meanwhile, graph G4 shown in FIG. 3 shows the change over time in the maximum ideal power of the microbial fuel cell 1 using soil 11 with 50% chicken manure charcoal mixed in. Note that in all microbial fuel cells 1, iron was mixed into the soil 11. From FIG. 3, it can be seen that mixing chicken manure charcoal into the soil 11 significantly increases the power output of the microbial fuel cell 1.

[0036] FIG. 4 is a graph showing the results of an experiment demonstrating that mixing livestock manure-derived charcoal into soil 11 increases the power output of a microbial fuel cell compared to mixing soil 11 with charcoal not derived from livestock manure. Graph G5 in FIG. 4 shows the change over time in the maximum ideal power of a microbial fuel cell 1 using soil 11 mixed with 50% rice husk charcoal (an example of a charcoal not derived from livestock manure). Graph G6 in FIG. 4 shows the change over time in the maximum ideal power of a microbial fuel cell 1 using soil 11 mixed with 50% chicken manure charcoal. Note that in both microbial fuel cells 1, iron was mixed into the soil 11. FIG. 4 reveals that the power output of the microbial fuel cell 1 is significantly increased when the biochar mixed into the soil 11 is derived from livestock manure.

[0037] FIG. 5 is a graph showing the results of an experiment demonstrating that the incorporation of livestock manure-derived charcoal into soil 11 stably increases the power output of a microbial fuel cell over a long period of time. Graph G7 in FIG. 5 shows the change over time in the maximum ideal power of a microbial fuel cell 1 using soil 11 without chicken manure charcoal. Graph G8 in FIG. 5 shows the change over time in the maximum ideal power of a microbial fuel cell 1 using soil 11 containing 50% chicken manure charcoal. Note that iron was also added to the soil 11 in both microbial fuel cells 1. Graph G7 in FIG. 5 shows the change over time in the maximum ideal power of a microbial fuel cell 1 over a period of more than five months under the same conditions as graph G3 in FIG. 3. Similarly, graph G8 in FIG. 5 shows the change over time in the maximum ideal power of a microbial fuel cell 1 over a period of more than five months under the same conditions as graph G4 in FIG. 3. From FIG. 5, it can be seen that the incorporation of livestock manure-derived charcoal into soil 11 not only temporarily but also stably increases the power output of a microbial fuel cell over a long period of time. [Explanation of symbols]

[0038] 1...Microbial fuel cell, 10...Container, 11...Soil, 12...Anode electrode, 13...Cathode electrode, 14...Anode side conductor, 15...Cathode side conductor, 16...Lid, 17...Water.

Claims

1. Soil mixed with carbonized material derived from livestock excrement; an anode electrode disposed in the anaerobic environment of the soil; a cathode electrode disposed in the aerobic environment of the soil; A microbial fuel cell comprising:

2. Metal species have been artificially mixed into the soil The microbial fuel cell according to claim 1.

3. The metal species includes iron metal species. The microbial fuel cell according to claim 2.

4. The carbonized material derived from livestock waste includes chicken manure charcoal. The microbial fuel cell according to claim 1.

Images