Carbon fixation system

Abstract

To provide a carbon fixation system that enables reduction of carbon dioxide emissions resulting from organic matter.SOLUTION: A carbon fixation system 1 is configured to fix methane M, generated by fermentation of organic matter O, as inorganic carbon C. The carbon fixation system 1 comprises a biogas production apparatus 2 for producing a biogas B containing methane M by fermenting the organic matter O, and a carbon fixation apparatus 3 for fixing the methane M, derived from the biogas B, as inorganic carbon C on a surface of a treatment target T.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a carbon fixation system. [Background technology]

[0002] In recent years, the magnitude of the impact of human activities on the global environment has become a concern, and from the perspective of reducing the burden on the global environment, it is desirable to reuse waste as a resource as much as possible. Therefore, technologies have been studied to reuse organic waste, which has traditionally been incinerated, as resources such as methane through fermentation (e.g., Patent Document 1). When organic waste is fermented in an anaerobic atmosphere, biogas containing methane is obtained. Biogas obtained by fermenting organic waste has traditionally been used as fuel for generators and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-115812 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a strong desire to reduce carbon dioxide emissions in order to lessen the burden on the global environment. However, when biogas is used as fuel for generators and other equipment, the methane in the biogas is burned and ultimately turns into carbon dioxide, so this does not result in a reduction in carbon dioxide emissions.

[0005] The present invention has been made in view of the above problems, and aims to provide a carbon fixation system that can reduce the amount of carbon dioxide generated from organic matter. [Means for solving the problem]

[0006] One aspect of the present invention is a carbon fixation system that fixes methane produced by fermentation of organic matter as inorganic carbon, comprising: a biogas production device for producing biogas containing methane by fermenting the organic matter; and a carbon fixation device that fixes methane derived from the biogas as inorganic carbon on the surface of an object to be treated. [Effects of the Invention]

[0007] The carbon fixation system includes a biogas production apparatus and a carbon fixation apparatus. After producing biogas by fermenting organic matter in the biogas production apparatus, the methane in the biogas can be fixed as inorganic carbon on the surface of the object to be treated in the carbon fixation apparatus. The inorganic carbon fixed in the carbon fixation apparatus will not become carbon dioxide unless it reacts with oxygen through combustion or other means. Therefore, by fixing methane as inorganic carbon in the carbon fixation apparatus, the amount of carbon dioxide generated from organic matter can be reduced.

[0008] As described above, according to the above-described embodiment, it is possible to provide a carbon fixation system that can reduce the amount of carbon dioxide generated from organic waste. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic configuration of a carbon fixation system according to the first embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing a schematic configuration of a carbon fixation system equipped with a temperature adjustment unit in the second embodiment. [Figure 3] FIG. 3 is an explanatory diagram showing a schematic configuration of a carbon fixation system including a processing device in the third embodiment. [Figure 4] FIG. 4 is an explanatory diagram showing a schematic configuration of a carbon fixation system equipped with a concentration adjuster according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Embodiment 1) An embodiment of the carbon fixation system will be described with reference to Fig. 1. The carbon fixation system 1 of this embodiment is configured to fix methane M produced by fermentation of organic matter O as inorganic carbon C. The carbon fixation system 1 includes a biogas production apparatus 2 that produces biogas B containing methane M by fermentation of organic matter O, and a carbon fixation apparatus 3 that fixes the methane M derived from the biogas B as inorganic carbon C on the surface of a treatment target T.

[0011] In the carbon fixation system 1, there are no particular limitations on the organic matter O used as the raw material for the biogas B. Examples of raw materials for the biogas B include domestic wastewater containing organic matter O, such as sewage sludge and food waste, and industrial wastewater containing organic matter O, such as waste water-soluble coolant recovered from machining equipment.

[0012] The organic matter O that is the raw material for the biogas B is preferably derived from a fossil fuel. That is, the biogas production apparatus 2 is preferably configured to produce the biogas B by fermenting the organic matter O produced from a fossil fuel. In this way, by generating the biogas B from the organic matter O derived from a fossil fuel and further fixing the methane M in the biogas B as inorganic carbon C, it is possible to reduce the amount of carbon dioxide generated that is derived from the fossil fuel.

[0013] The organic matter O is fermented in the biogas production apparatus 2 to produce biogas B containing methane M. In the carbon fixation system 1 of this example, various methods can be used to supply the organic matter O to the biogas production apparatus 2. For example, the carbon fixation system 1 of this embodiment has a raw material tank 11 in which the raw material for biogas B is stored, and is configured so that the raw material can be supplied from the raw material tank 11 to the biogas production apparatus 2.

[0014] The specific embodiment of the biogas production apparatus 2 is not particularly limited as long as it can ferment the organic matter O, and various embodiments are possible. For example, the biogas production apparatus 2 of this embodiment has a fermenter 21 that brings microorganisms into contact with the organic matter O. The biogas production apparatus 2 can ferment the organic matter O to produce biogas B by bringing the microorganisms into contact with the organic matter O in the fermenter 21.

[0015] The contact between the microorganisms and the organic matter O in the fermenter 21 can take various forms. For example, the fermenter 21 may be configured to ferment the organic matter O by mixing the organic matter O with the microorganisms. Alternatively, the fermenter 21 may be configured to ferment the organic matter O by mixing the organic matter O with a composition containing the microorganisms (e.g., soil or sludge).

[0016] The fermenter 21 of this embodiment has a microorganism carrier 22 on which microorganisms are supported, and by bringing the organic matter O into contact with the microorganism carrier 22 in the fermenter 21, the organic matter O can be fermented.

[0017] The biogas production apparatus 2 may further include a fermentation promotion unit for promoting fermentation of the organic matter O. Examples of the fermentation promotion unit include an agitation unit (not shown) for further improving the contact efficiency between the organic matter O and the microorganisms, a temperature adjustment unit 23 for adjusting the temperature in the fermenter 21 to increase the activity of the microorganisms, and a pH adjustment unit (not shown) for adjusting the pH in the fermenter 21 to increase the activity of the microorganisms.

[0018] It is sufficient that the microorganisms used in the biogas production apparatus 2 include at least methanogens. By using microorganisms including methanogens to ferment organic matter O in an anaerobic atmosphere, biogas B containing methane M can be reliably produced.

[0019] When the raw material for biogas B contains hydrocarbons such as mineral oil, it is more preferable that the microorganisms include methanogens, hydrolytic bacteria, and acid-producing bacteria. When methanogens, hydrolytic bacteria, and acid-producing bacteria are brought into contact with hydrocarbons in the biogas production apparatus 2, the hydrocarbons are digested by the hydrolytic bacteria and acid-producing bacteria, producing acetic acid, hydrogen, and carbon dioxide. These products are then further digested by the methanogens, which is believed to enable more efficient generation of biogas B containing methane M.

[0020] The biogas B produced in the biogas production apparatus 2 may be introduced directly to the carbon fixation apparatus 3. Furthermore, the biogas B produced in the biogas production apparatus 2 may contain, in addition to methane M, gases G other than methane M, such as carbon dioxide and hydrogen sulfide. In this case, the methane M in the biogas B may be separated from the gases G other than methane M, and then the methane M may be introduced to the carbon fixation apparatus 3. In either case, by fixing the methane M as inorganic carbon C on the surface of the treatment target T in the carbon fixation apparatus 3, the amount of carbon dioxide generated from the organic matter O can be reduced.

[0021] The carbon fixation system 1 of this embodiment has a gas separation device 12 that separates methane M in the biogas B from gases G other than methane M, and is configured to introduce the biogas B generated in the biogas production device 2 into the gas separation device 12 to separate the gases G other than methane M from the methane M. The amount of biogas B generated in the biogas production device 2 and the concentration of methane M in the biogas B may vary depending on the type of organic matter O used as raw material, the fermentation conditions, and the like. Even in such cases, high-purity methane M can be stably obtained by separating the methane M from the gases G other than methane M using the gas separation device 12. As a result, carbon fixation in the carbon fixation device 3 can be performed more easily.

[0022] The method for separating methane M from gas G other than methane M in the gas separation device 12 is not particularly limited, and known gas separation techniques can be employed. For example, the gas separation device 12 may have a gas separation membrane that separates methane M from gas G other than methane M. In this case, methane M can be separated from gas G other than methane M by contacting the biogas B with the gas separation membrane. Furthermore, for example, the gas separation device 12 may be configured to remove gas G other than methane M from the biogas B and separate methane M by contacting the biogas B with an adsorbent that adsorbs gas G other than methane M or a gas absorption liquid that dissolves gas G other than methane M.

[0023] The methane M separated from the biogas B in the gas separation device 12 may be introduced directly to the carbon fixation device 3, or may be temporarily stored in a tank or the like and then introduced to the carbon fixation device 3. As shown in FIG. 1 , the carbon fixation system 1 of this embodiment has a methane tank 13 that stores the methane M separated from the biogas B in the gas separation device 12. By storing the methane M separated from the biogas B in the methane tank 13 in this way, fluctuations in the amount of methane M supplied to the carbon fixation device 3 can be suppressed even if the amount of biogas B produced in the biogas production device 2 or the concentration of methane M in the biogas B fluctuates. Furthermore, in this case, methane M can be supplied as needed when the carbon fixation device 3 is used. Therefore, by providing the methane tank 13, the carbon fixation device 3 can be operated more efficiently.

[0024] Furthermore, gas G other than methane M separated from methane M in the gas separation device 12 may be discarded or may be used for other purposes depending on its composition, etc. For example, the carbon fixation system 1 of this embodiment has an anaerobic gas tank 14 that stores gas G other than methane M separated from methane M in the gas separation device 12, and is configured to be able to supply gas G in the anaerobic gas tank 14 to the biogas production device 2. Biogas B produced in the biogas production device 2 contains almost no oxygen. Therefore, by guiding gas G other than methane M separated from biogas B to the anaerobic gas tank 14, gas G containing almost no oxygen can be stored in the anaerobic gas tank 14.

[0025] Furthermore, the atmosphere inside the biogas production apparatus 2 may become an aerobic atmosphere, for example, when the apparatus is opened for maintenance. Even in such a case, the atmosphere inside the biogas production apparatus 2 can be quickly adjusted to an anaerobic atmosphere suitable for producing methane M by supplying the gas G stored in the anaerobic gas tank 14 to the biogas production apparatus 2. This allows the biogas production apparatus 2 to be operated more efficiently.

[0026] The carbon fixation device 3 is configured to fix methane M produced in the biogas production apparatus 2 as inorganic carbon C on the surface of the treatment target T. The specific embodiment of the carbon fixation device 3 is not particularly limited, and various embodiments are possible. For example, the carbon fixation device 3 may be configured to fix inorganic carbon C on the surface of the treatment target T by performing a carburizing treatment on the treatment target T made of metal. In other words, the carbon fixation device 3 may be a carburizing furnace such as a gas carburizing furnace, a vacuum gas carburizing furnace, or a plasma carburizing furnace.

[0027] In the carburization process, methane M is decomposed on the surface of the object T to be treated and fixed as inorganic carbon C. Furthermore, the inorganic carbon C generated on the surface of the object T to be treated diffuses into the interior of the object T to be treated, forming a carburized layer on the surface of the object T to be treated. The inorganic carbon C contained in the carburized layer will not become carbon dioxide unless it reacts with oxygen through combustion or other means. Therefore, by using methane M derived from organic matter O in the carburization process, the amount of carbon dioxide generated from organic matter O can be reduced.

[0028] When carburizing treatment is performed in the carbon fixation device 3, a steel material can be used as the treatment object T. More specifically, the treatment object T may be a component part of an engine, clutch, differential, transmission, or the like, or a mechanical part that requires high surface hardness, such as a bearing or gear.

[0029] The carbon fixation device 3 may also be configured to fix inorganic carbon C to the surface of the treatment object T by forming a coating made of diamond-like carbon on the surface of the treatment object T. Furthermore, the carbon fixation device 3 may also be configured to fix inorganic carbon C to the surface of the treatment object T by epitaxially growing diamond on the surface of a diamond crystal as the treatment object T. That is, the carbon fixation device 3 may be a CVD device such as a thermal CVD (chemical vapor deposition) device or a plasma CVD device.

[0030] In the CVD method, methane M is decomposed on the surface of the object to be treated T to become inorganic carbon C. This inorganic carbon C is then fixed to the surface of the object to be treated T, thereby forming a diamond-like carbon coating or a diamond epitaxial layer on the surface of the object to be treated T. The inorganic carbon C fixed to the surface of the object to be treated T in this way will not become carbon dioxide unless it reacts with oxygen through combustion or the like. Therefore, by using methane M derived from the organic matter O to form a diamond-like carbon coating or a diamond epitaxial layer, the amount of carbon dioxide generated from the organic matter O can be reduced.

[0031] The amount of methane M supplied from the methane tank 13 to the carbon fixation device 3 may be appropriately set depending on the carbon fixation method used in the carbon fixation device 3. Furthermore, in order to adjust the concentration of methane M supplied to the carbon fixation device 3, gases other than methane M may be added to the methane M supplied from the methane tank 13 to the carbon fixation device 3, as necessary. For example, when CVD is performed in the carbon fixation device 3, a carrier gas such as argon, nitrogen, or hydrogen may be added to the methane M, and a mixed gas of methane M and the carrier gas may be supplied to the carbon fixation device 3. Furthermore, when atoms other than inorganic carbon (C) are to be added to the film formed by CVD, a dopant gas containing the desired atom may be added to the methane M, and the mixed gas of methane M and the dopant gas may be supplied to the carbon fixation device 3. Furthermore, in order to supply a sufficient amount of carbon atoms to the carbon fixation device 3, a hydrocarbon gas may be added to the methane M, and the mixed gas of methane M and the hydrocarbon gas may be supplied to the carbon fixation device 3.

[0032] As described above, the carbon fixation system 1 of this embodiment includes the biogas production apparatus 2 and the carbon fixation apparatus 3. After producing biogas B by fermenting organic matter O in the biogas production apparatus 2, the methane M in the biogas B can be fixed as inorganic carbon C on the surface of the treatment target T in the carbon fixation apparatus 3. The inorganic carbon C fixed in the carbon fixation apparatus 3 will not become carbon dioxide unless it reacts with oxygen by combustion or the like. Therefore, by fixing methane M as inorganic carbon C in the carbon fixation apparatus 3, the amount of carbon dioxide generated from the organic matter O can be reduced.

[0033] (Embodiment 2) In this embodiment, one aspect of a carbon fixation system that does not have a gas separation device will be described. Note that, among the symbols used in this embodiment and subsequent embodiments, the same symbols as those used in the previous embodiments represent the same components as those in the previous embodiments, unless otherwise specified.

[0034] 2 , the carbon fixation system 102 of this embodiment includes a raw material tank 11 that stores raw materials containing organic matter O, a biogas production apparatus 2 that ferments the organic matter O to produce biogas B, and a carbon fixation apparatus 3 that fixes methane in the biogas B as inorganic carbon C on the surface of a treatment target T. The configurations of the raw material tank 11 and the biogas production apparatus 2 in the carbon fixation system 102 of this embodiment are the same as the configurations of the corresponding parts in the carbon fixation system 1 of the first embodiment.

[0035] The carbon fixation system 102 has a biogas tank 15 that stores the biogas B produced in the biogas production apparatus 2. The biogas B stored in the biogas tank 15 is introduced into the carbon fixation apparatus 3 and used for carbon fixation.

[0036] The carbon fixation system 102 of this embodiment has a concentration adjustment device 4 that adjusts the concentration of hydrocarbon gas HC in biogas B. The concentration adjustment device 4 has a concentration measurement unit 41 that measures the methane concentration in biogas B, an addition amount calculation unit 42 that calculates the amount of hydrocarbon gas HC to be added to biogas B based on a preset target value for the total hydrocarbon concentration and the methane concentration, and a hydrocarbon addition unit 43 that adds the amount of hydrocarbon gas HC calculated in the addition amount calculation unit 42 to biogas B.

[0037] The specific aspects of the concentration measurement unit 41, the addition amount calculation unit 42, and the hydrocarbon addition unit 43 are not particularly limited and may take various forms. For example, the concentration measurement unit 41 in this embodiment is a methane sensor provided in the biogas tank 15. The concentration measurement unit 41 can measure the concentration of methane stored in the biogas tank 15.

[0038] Although not shown in the figure, the addition amount calculation unit 42 in this embodiment is a computer equipped with an arithmetic unit, a storage device, an input device, and an output device. The storage device stores a program for calculating the amount of hydrocarbon gas HC to be added to biogas B. The input device is connected to the concentration measurement unit 41 and is configured to store the methane concentration measured by the concentration measurement unit 41 in the storage device. The input device also has a man-machine interface for inputting a target value for the total hydrocarbon concentration. The target value for the total hydrocarbon concentration input from the input device is stored in the storage device.

[0039] The calculation device calculates the amount of hydrocarbon gas HC to be added to the biogas B in the biogas tank 15 from the target value of the total hydrocarbon concentration and the methane concentration in accordance with the program stored in the storage device. The amount of hydrocarbon gas HC calculated by the calculation device is then output to the hydrocarbon addition unit 43 via the output device.

[0040] The hydrocarbon addition unit 43 adds the amount of hydrocarbon gas HC calculated by the addition amount calculation unit 42 to the biogas tank 15 in accordance with the calculation result of the addition amount calculation unit 42 .

[0041] In this way, by measuring the methane concentration of biogas B produced in the biogas production apparatus 2 and adding hydrocarbon gas HC to biogas B as needed, it is possible to reliably adjust the total hydrocarbon concentration in biogas B to a range suitable for carbon fixation. Then, by supplying biogas B with an adjusted total hydrocarbon concentration to the carbon fixation apparatus 3, carbon fixation can be carried out more efficiently in the carbon fixation apparatus 3.

[0042] The hydrocarbon gas HC added to the biogas B from the concentration adjusting device 4 is preferably derived from a fossil fuel. In this case, the hydrocarbons derived from the fossil fuel can be fixed as inorganic carbon. As a result, the amount of carbon dioxide generated from the fossil fuel can be reduced.

[0043] In addition, the carbon fixation system 102 of this embodiment can achieve the same effects as the carbon fixation system 1 of the first embodiment.

[0044] (Embodiment 3) In this embodiment, one aspect of a carbon fixation system including a processing apparatus will be described. As shown in Fig. 3, the carbon fixation system 103 of this embodiment includes a raw material tank 11 that stores raw materials containing organic matter O, a biogas production apparatus 2 that ferments the organic matter O to produce biogas B, a biogas tank 15 that stores the biogas B, a concentration adjustment device 4 that adds hydrocarbon gas HC to the biogas B as needed, and a carbon fixation device 3 that fixes methane in the biogas B as inorganic carbon C on the surface of the treatment target T. The configurations of the carbon fixation system 103 of this embodiment, other than the raw material tank 11 and the carbon fixation device 3, are the same as the configurations of the corresponding parts in the carbon fixation system 102 of the second embodiment.

[0045] The carbon fixation system 103 of this embodiment has a processing device 5 that uses a water-soluble coolant to machine the workpiece W. The processing device 5 may be a cutting device, a grinding device, or a polishing device. The carbon fixation system 103 may have one processing device 5, or two or more processing devices 5.

[0046] The carbon fixation system 103 of this embodiment is configured to recover waste water-soluble coolant U and use it as a raw material for biogas B. The waste water-soluble coolant U discharged from the processing device 5 contains organic matter O such as mineral oil. Therefore, by recovering the waste water-soluble coolant U from the processing device 5 and fermenting it in the biogas production device 2, biogas B containing methane can be produced.

[0047] The method of recovering the waste water-soluble coolant U from the processing apparatus 5 is not particularly limited and can take various forms. Although not shown in the figure, for example, the waste water-soluble coolant tank of the processing apparatus 5 and the raw material tank 11 may be connected by a pipe for recovering the waste water-soluble coolant U. In this case, the waste water-soluble coolant U discharged from the processing apparatus 5 can be recovered by guiding it to the raw material tank 11 via the pipe. Furthermore, as shown in FIG. 3, for example, the waste water-soluble coolant U discharged from the processing apparatus 5 can also be recovered using a transfer container 51. In this case, the waste water-soluble coolant U can be transferred from the waste water-soluble coolant tank of the processing apparatus 5 to the transfer container 51, and then transferred from the transfer container 51 to the raw material tank 11.

[0048] The biogas production apparatus 2 of this embodiment is configured to produce biogas B by fermenting organic matter O in waste water-soluble coolant U recovered from the processing device 5. The waste water-soluble coolant U contains organic matter O derived from fossil fuels such as mineral oil. Therefore, by producing biogas B using the waste water-soluble coolant U as a raw material and fixing the methane in the biogas B as inorganic carbon C, it is possible to reduce the amount of carbon dioxide generated that is derived from fossil fuels.

[0049] Furthermore, the carbon fixation system 103 of this embodiment is preferably configured such that the processing device 5 machines the workpiece W to produce the workpiece T, and the carbon fixation device 3 fixes methane in the biogas B as inorganic carbon C on the surface of the workpiece T. In this case, the waste water-soluble coolant U discharged from the processing device 5 can be reused as a resource, thereby reducing the amount of waste water-soluble coolant U that is discarded. Furthermore, by producing biogas B from the waste water-soluble coolant U and fixing it as inorganic carbon C on the surface of the workpiece T, it is expected that the amount of hydrocarbon gas used when forming a carburized layer or a diamond-like carbon coating on the workpiece T can be reduced. Therefore, the carbon fixation system 103 configured in this manner is expected to further reduce the environmental impact of the series of processes that machine the workpiece W to produce the workpiece T, and then carburize the workpiece T and form a diamond-like carbon coating on it.

[0050] In addition, the carbon fixation system 103 of this embodiment can achieve the same effects as the carbon fixation system 102 of the second embodiment.

[0051] (Embodiment 4) In this embodiment, one aspect of a carbon fixation system configured to perform carburization treatment in a carbon fixation device will be described. As shown in Figure 4, the carbon fixation system 104 of this embodiment includes a raw material tank 11, a biogas production device 204, a biogas tank 15, and a carbon fixation device 304.

[0052] In the carbon fixation system 104 of this embodiment, the raw material for biogas B is stored in a raw material tank 11. The raw material in the raw material tank 11 is supplied to a biogas production device 204 as needed.

[0053] The biogas production apparatus 204 has a fermenter 21 in which organic matter O is fermented by microorganisms, and a temperature adjustment unit 24 that adjusts the temperature inside the fermenter 21. The fermenter 21 is configured to ferment the organic matter O by bringing the microorganisms into contact with the organic matter O, thereby producing biogas B containing methane. Furthermore, the temperature adjustment unit 24 in the biogas production apparatus 204 of this embodiment is configured to adjust the temperature inside the fermenter 21 using waste heat H generated in the carbon fixation device 304, as will be described later.

[0054] Biogas B produced by fermentation of organic matter O in fermenter 21 is introduced into biogas tank 15 and stored therein. Biogas B in biogas tank 15 is supplied to carbon fixation device 304 as needed. Carbon fixation device 304 in this embodiment has a carburizing furnace 31 that performs a carburizing treatment on treatment target T. Carbon fixation device 304 also has a carburizing temperature control unit 32 that adjusts the heating temperature in the carburizing treatment based on the methane concentration in biogas B.

[0055] The specific embodiment of the carburizing temperature control unit 32 is not particularly limited and various embodiments are possible. For example, the carburizing temperature control unit 32 in this embodiment has a methane sensor 321 provided in the biogas tank 15 and a target temperature calculation unit 322 that calculates a target value for the temperature inside the carburizing furnace 31 based on the methane concentration in the biogas B measured by the methane sensor 321. The methane sensor 321 is configured to be able to measure the methane concentration of the biogas B in the biogas tank 15.

[0056] Although not shown in the figure, the target temperature calculation unit 322 in this embodiment is a computer equipped with an arithmetic unit, a storage device, an input device, and an output device. The storage device stores a program for calculating the target value of the temperature inside the carburizing furnace 31 based on the methane concentration of biogas B. The input device is connected to the methane sensor 321 and is configured to store the methane concentration measured by the methane sensor 321 in the storage device.

[0057] The computing device calculates the target temperature in the carburizing furnace 31 based on the methane concentration in accordance with a program stored in the storage device. In the carburizing process, the higher the methane concentration in biogas B and the higher the heating temperature, the higher the carbon concentration of the carburized layer formed. However, if the carbon concentration in the carburized layer becomes excessively high, problems such as embrittlement of the carburized layer may occur. Therefore, when the methane concentration in biogas B is high, it is preferable to lower the temperature in the carburizing furnace 31 to prevent the carbon concentration in the carburized layer from becoming excessively high.

[0058] On the other hand, when the methane concentration in the biogas B is low, the amount of inorganic carbon C fixed on the surface of the treatment object T is small, and the carbon concentration of the carburized layer is likely to be low. Therefore, for example, when the methane concentration is low, it is preferable to increase the temperature inside the carburizing furnace 31 to promote the diffusion of inorganic carbon C into the treatment object T.

[0059] Therefore, the program stored in the storage device is preferably configured to calculate a target value such that the temperature inside the carburizing furnace 31 decreases as the methane concentration of the biogas B increases.

[0060] The target temperature value calculated by the calculation device is output via the output device to the carburizing furnace 31. The carburizing furnace 31 adjusts the temperature inside the furnace in accordance with the target temperature value output from the output device. In this way, by adjusting the heating temperature in the carburizing treatment in the carburizing temperature control unit 32 according to the methane concentration of the biogas B, it is possible to more easily form a carburized layer having a desired carbon concentration on the surface of the treatment object T.

[0061] In addition, the waste heat H generated in the carburizing furnace 31 is guided to the temperature adjustment unit 24 of the biogas production apparatus 204 via a heat medium, and is used to adjust the temperature in the fermentation tank 21 as needed. By adjusting the temperature in the fermentation tank 21 using the waste heat H from the carburizing furnace 31 in this way, it is expected that the energy required to operate the biogas production apparatus 204 will be reduced.

[0062] In addition, the carbon fixation system 104 of this embodiment can achieve the same effects as the carbon fixation system 1 of the first embodiment.

[0063] The carbon fixation system has been described above based on embodiments 1 to 4, but the specific aspects of the carbon fixation system according to the present invention are not limited to the aspects of the above embodiments, and the configuration can be changed as appropriate within the scope of the gist of the present invention.

[0064] For example, in the first and fourth embodiments, carbon fixation systems that do not include processing equipment have been described, but these carbon fixation systems can also include processing equipment as in the third embodiment, and carbon fixation can be performed using waste water-soluble coolant discharged from the processing equipment. [Explanation of symbols]

[0065] 1, 102-104 Carbon fixation system 2, 204 Biogas production equipment 3.304 Carbon fixation device B. Biogas C Inorganic carbon M methane O organic matter T Processing object

Claims

1. A carbon fixation system that fixes methane produced by fermentation of organic matter as inorganic carbon, a biogas production device for producing biogas containing methane by fermenting the organic matter; a carbon fixation device that fixes methane derived from the biogas as inorganic carbon on the surface of an object to be treated.

2. The carbon fixation system according to claim 1 , further comprising a gas separation device that separates methane in the biogas from gases other than methane.

3. 3. The carbon fixation system according to claim 2, further comprising an anaerobic gas tank that stores gases other than methane separated from methane in the gas separation device and supplies the gases to the biogas production device.

4. The carbon fixation system comprises: a concentration measuring unit that measures the methane concentration in the biogas; an addition amount calculation unit that calculates an amount of hydrocarbon gas to be added to the biogas based on a preset target value of the total hydrocarbon concentration and the methane concentration; 2. The carbon fixation system according to claim 1, further comprising a concentration adjusting device including a hydrocarbon adding unit that adds the amount of hydrocarbon gas calculated by the addition amount calculating unit to the biogas.

5. The carbon fixation system of claim 3 , wherein the hydrocarbon gas is derived from a fossil fuel.

6. The carbon fixation system of claim 1 , wherein the organic matter is derived from a fossil fuel.

7. 2. The carbon fixation system according to claim 1, wherein the carbon fixation system includes a processing device that performs mechanical processing on an object to be processed using a water-soluble coolant, and the biogas production device is configured to produce the biogas by fermenting organic matter in the waste water-soluble coolant recovered from the processing device.

8. 8. The carbon fixation system according to claim 7, wherein the processing device performs machining on the object to be processed to produce the object to be treated, and the carbon fixation device fixes methane in the biogas as inorganic carbon on a surface of the object to be treated.

9. 9. The carbon fixation system according to claim 1, wherein the carbon fixation device is configured to fix inorganic carbon to a surface of the object to be treated, the object being made of metal, by performing a carburization treatment on the object.

10. 10. The carbon fixation system according to claim 9, wherein the carbon fixation device has a carburization temperature control unit that adjusts the heating temperature in the carburization treatment based on the methane concentration in the biogas.

11. 10. The carbon fixation system according to claim 9, wherein the biogas production apparatus comprises: a fermentation tank in which the organic matter is fermented by microorganisms; and a temperature adjustment unit that adjusts the temperature inside the fermentation tank by using waste heat generated in the carbon fixation apparatus.

12. The carbon fixation system according to claim 9 , wherein the object to be treated is made of a steel material.

13. The carbon fixation system according to any one of claims 1 to 8, wherein the carbon fixation device is configured to fix inorganic carbon to the surface of the object to be treated by forming a coating made of diamond-like carbon on the surface of the object to be treated.

14. The carbon fixation system according to any one of claims 1 to 6, wherein the carbon fixation device is configured to fix inorganic carbon to the surface of the object to be treated by epitaxially growing diamond on the surface of a diamond crystal as the object to be treated.

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