Methane fermentation system and methane fermentation method

Abstract

To provide a methane fermentation system and a methane fermentation method capable of improving carrying-out workability of high water content solid biomass and cleaning workability of a fermentation chamber.SOLUTION: The methane fermentation system includes a fermentation chamber 1, a second storage part 32 provided below a floor surface 12 of the fermentation chamber 1 and storing a first fermentation raw material 7 having a TS (solid concentration) of less than 15%, and a box body part 2 installed in the fermentation chamber 1 and storing a second fermentation raw material 8 having a TS of 15% or more. When the first fermentation raw material 7 stored in the second storage part 32 is supplied and brought into contact with the second fermentation raw material 8, at least a part of the first fermentation raw material 7 is dropped through a separation hole 23 bored in the bottom plate 21 to be separated from the second fermentation raw material 8.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a methane fermentation system and a methane fermentation method used to ferment biomass resources such as agricultural residues and livestock manure. [Background technology]

[0002] BACKGROUND ART Conventionally, methane fermentation technology, which efficiently ferments stored biomass resources, has been studied as a method for effectively utilizing biomass resources as energy resources.

[0003] One method for efficiently fermenting biomass resources is to repeatedly contact the solid biomass by circulating a digestion solution as a seed culture solution through a fermentation chamber storing solid biomass. In this method, the solid biomass after fermentation absorbs water from the digestion solution and becomes high-moisture solid biomass, which tends to collapse and makes it difficult to transport from the fermentation chamber. In addition, the high-moisture solid biomass tends to stick to the walls and floor of the fermentation chamber, making it difficult to clean even by spraying water. Therefore, when implementing this methane fermentation method, it is necessary to improve the ease of transporting and cleaning the high-moisture solid biomass.

[0004] Patent Document 1 discloses a fermenter having a liquid groove formed on the floor of the fermenter to accommodate a liquid raw material, and a fermenter installed inside the fermenter to accommodate a solid raw material, to which the fermentation liquid contained in the liquid groove is supplied, and the fermentation liquid and solid biomass are separated by a rice husk layer on the surface of the liquid groove. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-744 Summary of the Invention [Problem to be solved by the invention]

[0006] The fermenter disclosed in Patent Document 1 allows for smooth replacement of biomass. However, the fermenter disclosed in Patent Document 1 has problems in that it is not possible to improve the ease of unloading biomass from the viewpoint of preventing collapse of the high-moisture biomass load, and it is not possible to improve the ease of cleaning the inside of the fermenter because rice husks are laid in the liquid groove.

[0007] The present invention has been devised in consideration of the above-mentioned problems, and its object is to provide a methane fermentation system and a methane fermentation method that improve the ease of transporting high-moisture solid biomass and the ease of cleaning the fermentation chamber. [Means for solving the problem]

[0008] The methane fermentation system of the first invention comprises a fermentation chamber, a storage section that is located below the floor of the fermentation chamber and that stores a first fermentation raw material having a TS (solids concentration) of less than 15%, and a box section that is installed in the fermentation chamber and that stores a second fermentation raw material having a TS of 15% or more, and is characterized in that when the first fermentation raw material stored in the storage section is supplied and comes into contact with the second fermentation raw material, the box section separates at least a portion of the first fermentation raw material from the second fermentation raw material by allowing it to fall through separation holes drilled in the bottom plate.

[0009] The methane fermentation system of the second invention is characterized in that, in the first invention, the box parts include an upper box part and a lower box part, each of which accommodates the second fermentation raw material, and when the first fermentation raw material accommodated in the accommodation part is supplied and comes into contact with the second fermentation raw material, the upper box part separates at least a portion of the first fermentation raw material from the second fermentation raw material by causing it to fall through an upper separation hole perforated in the bottom plate of the upper box part, and when the first fermentation raw material that has fallen from the upper box part is supplied and comes into contact with the second fermentation raw material, the lower box part separates at least a portion of the first fermentation raw material from the second fermentation raw material by causing it to fall through a lower separation hole perforated in the bottom plate of the lower box part.

[0010] The methane fermentation system of the third invention is characterized in that, in the first or second invention, the box portion is supplied with the first fermentation raw material to produce biogas, and the storage portion is supplied with the biogas produced by the box portion.

[0011] The methane fermentation method of the fourth invention is characterized by comprising a raw material supplying step of supplying a first fermentation raw material contained in a storage section that is located below the floor of a fermentation chamber and that contains a first fermentation raw material with a TS of less than 15% to a box section that is installed in the fermentation chamber and that contains a second fermentation raw material with a TS of 15% or more; and a separation step of separating at least a portion of the first fermentation raw material that has been supplied to the box section by the raw material supplying step and that has come into contact with the second fermentation raw material by passing it through separation holes drilled in the bottom plate of the box section and dropping it, thereby separating it from the second fermentation raw material. [Effects of the Invention]

[0012] According to the first and second inventions, the methane fermentation system includes a housing that separates the first fermentation raw material from the second fermentation raw material by allowing the first fermentation raw material to fall through a separation hole when the first fermentation raw material is supplied from the housing located below the floor of the fermentation chamber. This prevents the second fermentation raw material, which has a high moisture content, from collapsing and sticking to the inside of the fermentation chamber. This improves the ease of transporting the high-moisture solid biomass and the ease of cleaning the fermentation chamber in the methane fermentation system.

[0013] In particular, according to the second invention, the system includes an upper box portion that, when the first fermentation raw material contained in the storage portion is supplied, drops it through an upper separation hole to separate it from the second fermentation raw material contained therein, and a lower box portion that, when the first fermentation raw material dropped from the upper box portion is supplied, drops it through a lower separation hole to separate it from the second fermentation raw material contained therein. This allows for efficient fermentation of a large amount of fermentation raw material regardless of the volume of the box portion. This improves the biogas production efficiency of the methane fermentation system.

[0014] In particular, according to the third invention, the storage unit is supplied with biogas produced by the box-shaped unit. That is, the biogas produced by the box-shaped unit comes into contact with the first fermentation raw material and the products of fermentation of the first fermentation raw material contained in the storage unit, and hydrogen sulfide and ammonia in the biogas may be eluted. Therefore, there is no need to provide equipment for desulfurization and ammonia removal of the produced biogas. This allows for the miniaturization of the methane fermentation device. Furthermore, because carbon dioxide in the produced biogas is also eluted, it is possible to produce biogas with a purified methane concentration and high calorific value. This reduces the costs required for gas transportation, storage, etc., and improves the usefulness of biogas.

[0015] According to the fourth aspect of the present invention, the methane fermentation method includes a raw material supplying step of supplying a first fermentation raw material contained in a storage section provided below the floor of the fermentation chamber to a box section containing a second fermentation raw material, and a separation step of separating the first fermentation raw material from the second fermentation raw material by allowing the first fermentation raw material to fall through a separation hole. This prevents the high-moisture second fermentation raw material from collapsing and sticking to the inside of the fermentation chamber. This improves the ease of transporting high-moisture solid biomass and the ease of cleaning the fermentation chamber in the methane fermentation system. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic perspective view showing an example of a methane fermentation system according to this embodiment. [Figure 2] FIG. 2 is a schematic perspective view showing an example of a fermentation chamber that constitutes the methane fermentation system of this embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view showing an example of a fermentation chamber corresponding to the cross section AA in FIG. [Figure 4] FIG. 4 is a schematic plan view showing an example of a box body that constitutes the methane fermentation system in this embodiment. [Figure 5] FIG. 5 is a schematic cross-sectional view showing an example of a housing part corresponding to the cross section BB in FIG. [Figure 6]FIG. 6 is a schematic cross-sectional view showing an example of a process included in the operation of the methane fermentation system in this embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing an example of a process included in the operation of the methane fermentation system in this embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view showing an example of a process included in the operation of the methane fermentation system in this embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view showing a first modified example of the steps included in the operation of the methane fermentation system in this embodiment. [Figure 10] FIG. 10 is a schematic perspective view showing a second modified example of the fermentation chamber that constitutes the methane fermentation system of this embodiment. [Figure 11] FIG. 11 is a schematic cross-sectional view showing an example of a process included in the operation of the methane fermentation system corresponding to the cross-section BB of FIG. [Figure 12] FIG. 12 is a schematic cross-sectional view showing an example of a process included in the operation of the methane fermentation system corresponding to the cross-section BB of FIG. [Figure 13] FIG. 13 is a schematic cross-sectional view showing an example of a process included in the operation of the methane fermentation system corresponding to the cross-section BB of FIG. [Figure 14] FIG. 14 is a schematic cross-sectional view showing an example of a process included in the operation of the methane fermentation system corresponding to the cross-section BB of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, a methane fermentation system 100 and an example of a methane fermentation method according to an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, a first horizontal direction X is defined, one direction perpendicular to the first horizontal direction X is defined as a second horizontal direction Y, and a direction perpendicular to each of the first horizontal direction X and the second horizontal direction Y is defined as a height direction Z. The configurations in each drawing are shown schematically for the purpose of explanation, and for example, the size of each component and the size comparison between components may differ from those shown in the drawings.

[0018] (Methane Fermentation System 100) An example of a methane fermentation system 100 according to this embodiment will be described with reference to the drawings.

[0019] The methane fermentation system 100 is a system that promotes methane fermentation and produces biogas by bringing into contact a fermentation raw material (first fermentation raw material) having a TS (solids concentration) of less than 15%, which may include seed culture liquid, livestock manure, digestive fluid, etc., with a fermentation raw material (second fermentation raw material) having a TS of 15% or more, which may include solid biomass such as rice husks and waste materials. Note that the unit "%" for TS refers to % by mass.

[0020] 1 , the methane fermentation system 100 includes one or more fermentation chambers 1 each having an opening / closing section 11, and a box-shaped section 2. The methane fermentation system 100 may also include, for example, a biogas collection tank T for storing biogas generated in the fermentation chamber 1. In the methane fermentation system 100, an operator U carries the box-shaped section 2 containing the second fermentation raw material into the fermentation chamber 1, closes the opening / closing section 11, and after methane fermentation is completed, opens the opening / closing section 11 and carries the box-shaped section 2 out of the fermentation chamber 1.

[0021] 2 and 3, the methane fermentation system 100 includes a storage section 3 that is provided below the floor surface 12 of the fermentation chamber 1 (the inner surface of the floor plate material of the fermentation chamber 1) and that stores a first fermentation raw material having a TS of less than 15%. Here, the storage section 3 below the floor surface 12 means that the height of the bottom of the storage section 3 in the height direction Z (vertical direction) is lower than the height of the inner surface (floor surface 12) of the floor plate material of the fermentation chamber 1. Specifically, the storage section 3 below the floor surface 12 includes a case where the storage section 3 is integral with the floor surface 12 and inseparable from the fermentation chamber 1, such as a groove portion cut out of the floor surface 12, and a case where the storage section 3 is separate from the floor surface 12 and separated from the fermentation chamber 1, such as a storage space provided vertically (see FIG. 10) or diagonally below the floor surface 12.

[0022] 4 and 5, the methane fermentation system 100 is a box having a box body part 2 made up of a bottom plate 21 and a side plate 22 and an opening O that opens upward, and the bottom plate 21 is pre-drilled with separation holes 23 that allow the first fermentation raw material to pass through but not the second fermentation raw material. Therefore, in the methane fermentation system 100, when the first fermentation raw material stored in the storage part 3 is supplied to the box body part 2 and comes into contact with the second fermentation raw material, at least a portion of the first fermentation raw material can be separated from the second fermentation raw material by passing through the separation holes 23 and dropping.

[0023] In the prior art, repeated contact between the first fermentation raw material and the second fermentation raw material increases the moisture content of the second fermentation raw material, resulting in problems with the ease of removal and cleaning, such as the high-moisture second fermentation raw material collapsing within the fermentation chamber 1 or sticking to the floor or walls of the fermentation chamber 1. On the other hand, the methane fermentation system 100 of the present invention prevents the high-moisture second fermentation raw material from leaking from the box-shaped portion 2, and allows the first fermentation raw material to be discharged through the separation hole 23 in the box-shaped portion 2. This prevents the high-moisture second fermentation raw material from collapsing and sticking to the inside of the fermentation chamber 1. This improves the ease of removal of the high-moisture solid biomass from the methane fermentation system 100 and the ease of cleaning the fermentation chamber 1. Furthermore, because the storage portion 3 is located below the floor 12, the fermentation raw material in the fermentation chamber 1 can be efficiently replaced by driving a vehicle such as a forklift over the floor 12. This makes it possible to improve the efficiency of the work of transporting high-moisture solid biomass from the methane fermentation system 100.

[0024] The methane fermentation system 100 may further include a drainage pipe 4, a water pump 5, and a sprinkler pipe 6, as shown in Fig. 2, for example. The methane fermentation system 100 drains the first fermentation raw material stored in the storage unit 3 from the storage unit 3 via the drainage pipe 4, supplies the first fermentation raw material from above the box unit 2 via the water pump 5 and the sprinkler pipe 6, and then recovers the first fermentation raw material in the storage unit 3, repeating this process. In this case, promotion of methane fermentation can be sustained without adding the first fermentation raw material. This allows the methane fermentation system 100 to improve its operability and economy.

[0025] <Fermentation Room 1> The fermentation chamber 1 is a closed space that can be opened and closed and that contains fermentation raw materials and that performs methane fermentation. When the methane fermentation system 100 includes multiple fermentation chambers 1, each fermentation chamber 1 is an independent closed space. The material for the fermentation chamber 1 may be any material that can seal the interior of the fermentation chamber 1 and is strong enough to allow vehicles such as forklifts to travel inside, such as concrete or steel.

[0026] The shape and dimensions of the fermentation chamber 1 can be any as long as it can accommodate one or more box sections 2 and has sufficient floor area to form the accommodation section 3, but for example, it is an approximately rectangular parallelepiped with a width of 1 to 10 m, a height of 1 to 10 m, and a depth of 1 to 50 m.

[0027] 2 and 3, the fermentation chamber 1 is a closed space surrounded by an opening / closing section 11, a floor 12, side surfaces 13, and a ceiling 14. The fermentation chamber 1 is formed by cutting out one or more storage sections 3 in the floor 12.

[0028] The fermentation chamber 1 has a substantially horizontal floor 12, for example, in consideration of ease of installation of the box body 2. The fermentation chamber 1 may also be formed such that the floor 12 slopes downward from the opening / closing part 11 toward the depth of the fermentation chamber 1 on the drainage pipe 4 side (first horizontal direction X in FIG. 2). In this case, it is possible to prevent the first fermentation raw material from passing through the opening / closing part 11 and leaking out of the fermentation chamber 1. This can improve the economic efficiency of the methane fermentation system 100.

[0029] <Box part 2> The second fermentation raw material having a TS of 15% or more is accommodated in the box body 2. The box body 2 is made of a material such as steel, which has rigidity.

[0030] The shape and dimensions of the box body 2 are arbitrary as long as it can be installed independently within the fermentation chamber 1, but for example, it is a substantially rectangular parallelepiped with a width of 0.5 m to 2.5 m, a height of 0.5 m to 2.5 m, and a depth of 0.5 m to 2.5 m. The box body 2 is preferably a columnar body extending in the height direction Z, such as a polygonal column or a cylindrical column. In this case, multiple box body parts 2 can be stacked in the height direction Z, and the amount of the second fermentation raw material used in methane fermentation can be flexibly adjusted regardless of the dimensions of the box body parts 2. This improves the manufacturability of the methane fermentation system 100. It is also easy to design dimensions that allow the operator U to easily carry in and out. This improves the operability of the methane fermentation system 100.

[0031] As shown in Figs. 4 and 5, for example, the box body 2 has a bottom plate 21, side plates 22, separation holes 23, and an opening O. The box body 2 accommodates the second fermentation raw material inside or discharges the accommodated second fermentation raw material through the opening O. The box body 2 is composed of side plates 22 made of, for example, one or more known steel plates, and a bottom plate 21 made by stacking a grid-shaped steel plate and a punched metal, and in this case, the gaps between the grid and the punched holes correspond to the separation holes 23. The thickness of the bottom plate 21 and the side plates 22 is, for example, 0.1 mm to 50 mm.

[0032] <<Separation hole 23>> One or more separation holes 23 are pre-punched in the bottom plate 21 of the box body 2. The width of the separation hole 23 (width in the first horizontal direction X in FIG. 5) is, for example, 0.05 mm to 10 mm. When a plurality of separation holes 23 are drilled, they are drilled at predetermined intervals from one another. The separation holes 23 can separate multiple different fermentation raw materials that are in contact with or mixed with each other by dropping solids or fluids that are smaller than the width of the separation hole 23, among the fermentation raw materials accommodated in the box body 2, into the second accommodation section 32.

[0033] When a first fermentation raw material is supplied to the box part 2, which previously accommodates a second fermentation raw material, and comes into contact with the second fermentation raw material, at least a portion of the first fermentation raw material passes through and falls through the separation hole 23, thereby separating it from the second fermentation raw material. Here, some of the components contained in the second fermentation raw material that are eluted as a result of methane fermentation caused by contact between the first fermentation raw material and the second fermentation raw material are considered to be the first fermentation raw material that passes through the separation hole 23 and falls. In other words, as methane fermentation progresses, the volume of the first fermentation raw material increases, and the volume of the second fermentation raw material may decrease.

[0034] <Containment Unit 3> The storage section 3 stores the first fermentation raw material having a TS of less than 15%. As shown in Figures 2 and 3, the storage section 3 is in the shape of a groove formed by cutting out the floor surface 12 of the fermentation chamber 1. That is, the groove-shaped storage section 3 is provided below the floor surface 12, which is the inner surface of the floor board material of the fermentation chamber 1.

[0035] The storage section 3 may be formed by cutting out any shape from the floor surface 12, for example, as long as it is spaced from the opening / closing section 11, and may have a shape that combines one or more rectangles, trapezoids, triangles, etc. in a plan view. For example, one portion (one end) of the storage section 3 is formed on the floor surface 12 on the opening / closing section 11 side, and the other portion (the other end) is formed on the floor surface 12 on the side surface 13 side. For example, the other end of the storage section 3 is connected to a drain pipe 4. At this time, the first fermentation raw material stored in the storage section 3 flows from one end to the other end within the storage section 3 and is drained from the storage section 3 via the drain pipe 4.

[0036] The width of the housing section 3 (the width in the second horizontal direction Y in FIG. 2) is arbitrary, but is, for example, 100 mm to 500 mm.

[0037] 2, the storage section 3 may include a first storage section 31, a second storage section 32, and a third storage section 33. The storage sections 31, 32, and 33 are separated from each other, for example, at one end and merge at the other end. In this case, the first fermentation raw material is less likely to accumulate at one end than when the first fermentation raw material merges at one end and the other end, and can be efficiently caused to flow toward the drainage pipe 4 and drained from the storage section 3. This can improve the productivity of the methane fermentation system 100.

[0038] 3, the bottom surface of the storage section 3 is formed to be approximately horizontal. In this case, the space for storing the first fermentation raw material can be expanded more easily than when the bottom surface of the storage section 3 is formed to slope downward toward the depth of the fermentation chamber 1, and more first fermentation raw material can be stored and used for methane fermentation in one methane fermentation run. This allows for improved manufacturability of the methane fermentation system 100.

[0039] The storage section 3 may be formed so as to slope downward, for example, from one end to the other end. In this case, the first fermentation raw material is less likely to remain in the storage section 3, and can be efficiently drained from the storage section 3. This can improve the productivity of the methane fermentation system 100.

[0040] <Drainage pipe 4> One end of the drain pipe 4 is connected to the storage unit 3, and the other end is connected to the water pump 5. The drain pipe 4 drains the first fermentation raw material stored in the storage unit 3. The drain pipe 4 is made of, for example, resin.

[0041] In the example of Figures 2 and 3, the drainage pipe 4 is installed to communicate between the inside and outside of the fermentation chamber 1 so as to connect to a water pump 5 installed outside the fermentation chamber 1, but this is not limited to this and the drainage pipe 4 may also be connected to a water pump 5 installed inside the fermentation chamber 1.

[0042] <Water pump 5> One end of the water pump 5 is connected to the drain pipe 4, and the other end is connected to the sprinkler pipe 6. The water pump 5 sends the first fermentation raw material drained from the storage section 3 to the drain pipe 4 to the sprinkler pipe 6. As the water pump 5, for example, a known water pump is used.

[0043] <Sprinkler pipe 6> One end of the sprinkler pipe 6 is connected to the water pump 5, and the other end is disposed inside the fermentation chamber 1. The sprinkler pipe 6 is made of, for example, resin.

[0044] 2 and 3, the other end of the sprinkler pipe 6 is provided near the ceiling 14 of the fermentation chamber 1. When the sprinkler pipe 6 is rigid, it penetrates the side surface 13 and is fixed thereto, and extends along the ceiling 14; when the sprinkler pipe 6 is flexible, it penetrates the side surface 13 and is fixed to the ceiling 14.

[0045] Sprinkler pipe 6 has sprinkler holes (not shown) drilled in advance on the side of the pipe on the other end side located inside fermentation chamber 1, and sprinkles the first fermentation raw material through the sprinkler holes, which is pumped from one end side using water pump 5 as power. In other words, sprinkler pipe 6 can supply the first fermentation raw material stored in storage section 3 to box section 2 installed inside fermentation chamber 1 by spraying the first fermentation raw material from above inside fermentation chamber 1 and causing it to drop.

[0046] The sprinkler pipes 6 may include a first sprinkler pipe 61, a second sprinkler pipe 62, and a third sprinkler pipe 63, as shown in Fig. 2, for example. Each sprinkler pipe 61, 62, 63 branches off from a single pipe at one end within the fermentation chamber 1, and is separated from each other at the other end. In this case, the first fermentation raw material can be sprayed more evenly over a wider area than when the first fermentation raw material is sprayed from a single pipe that does not branch off, and methane fermentation can be sustained for a greater number of fermentation raw materials. This improves the productivity of the methane fermentation system 100.

[0047] <Biogas collection tank T> The biogas collection tank T is a tank for collecting the biogas produced in the fermentation chamber 1. The biogas collection tank T is directly connected to the fermentation chamber 1, for example.

[0048] The biogas collection tank T only collects and discharges the biogas generated in the fermentation chamber 1, and does not generate biogas within the biogas collection tank T. The material of the biogas collection tank T may be, for example, steel or a resin material such as polyvinyl chloride, which is the same as that of known gas holders.

[0049] (Methane fermentation method) Next, as a methane fermentation method in this embodiment, an example of the operation of the methane fermentation system 100 will be described with reference to the drawings. The methane fermentation method includes, for example, a raw material supplying step and a separation step.

[0050] In this embodiment, for ease of explanation, an example is given in which the second storage section 32 of the storage section 3 and the second sprinkler pipe 62 of the sprinkler pipe 6 are used, but this is not limited to this, and the first storage section 31, the third storage section 33, or the first sprinkler pipe 61, the third sprinkler pipe 63 may also be used.

[0051] In addition, in this embodiment, for each step of the methane fermentation method, the methane fermentation system 100 may control each component and execute each step based on a program or the like installed in a publicly known computer (not shown) equipped in the methane fermentation system 100, or the operator U may take the lead in operating each component of the methane fermentation system 100 to execute each step of the methane fermentation method.

[0052] First, as fermentation raw materials used in the methane fermentation method of this embodiment, we will explain the first fermentation raw material A and the second fermentation raw material B. The first fermentation raw material A corresponds to the above-mentioned first fermentation raw material, and the second fermentation raw material B corresponds to the above-mentioned second fermentation raw material.

[0053] <First fermentation ingredient A> The first fermentation raw material A is stored in advance in the second storage section 32, and is circulated by repeatedly draining the water from the storage section 32 and spraying water into the fermentation chamber 1 using a water pump 5 as power. The first fermentation raw material A undergoes wet methane fermentation in the fermentation chamber 1. For example, the first fermentation raw material A is a fluid biomass resource with a TS of 2% to 5% or more and less than 15%, and includes seed culture liquid, livestock manure, digestive fluid, etc. By using the first fermentation raw material A that satisfies the above-mentioned TS, the liquid first fermentation raw material A circulates within the fermentation chamber 1 while maintaining sufficient fluidity, and it is expected that the activity of the microorganisms required for methane fermentation will be actively carried out.

[0054] <Second fermentation ingredient B> The second fermentation raw material B is placed in the box body 2 in advance. The second fermentation raw material B undergoes dry methane fermentation within the box body 2. The second fermentation raw material B is, for example, a solid biomass resource with a TS of 15% or more and less than 30% to 40%, including solid biomass such as rice husks and waste wood. A typical single dry methane fermentation is operated using a raw material with a moisture content of approximately 60% to 80%, which corresponds to a TS of approximately 20% to 40%. Therefore, 40% is generally considered to be the upper limit for the TS of the second fermentation raw material B to be subjected to dry methane fermentation. By using a second fermentation raw material B that satisfies the above-mentioned TS, fermentation proceeds while the solid biomass second fermentation raw material B appropriately retains moisture, and it is expected that methane will be produced efficiently.

[0055] Next, the methane fermentation method of this embodiment will be described in detail. Note that the solid arrows in the drawings indicate the flow direction of the first fermentation raw material A.

[0056] <Advance preparation> As a preliminary preparation, for example, as shown in Fig. 6, the first fermentation raw material A is stored in advance in the second storage section 32, and the second fermentation raw material B is stored in advance in the box body section 2. Methane-producing bacteria are already present in the first fermentation raw material A or the second fermentation raw material B. Here, the first fermentation raw material A stored in the second storage section 32 is referred to as the first fermentation raw material Aa.

[0057] In addition, in order to create an anaerobic environment in the fermentation chamber 1 that promotes methane fermentation, the worker U places the first fermentation raw material A and the second fermentation raw material B in the fermentation chamber 1 with the opening / closing section 11 open, then closes the opening / closing section 11 to seal the fermentation chamber 1, and degass (deoxygenate) the fermentation chamber 1 as necessary.

[0058] <Raw material supply process> In the raw material supply step, the methane fermentation system 100 drains the first fermentation raw material A by causing it to flow from the second storage section 32 to the drain pipe 4 via the water supply pump 5, as shown in Fig. 6, for example. Thereafter, the methane fermentation system 100 sends the first fermentation raw material Aa drained into the drain pipe 4 to a second sprinkler pipe 62 installed above the fermentation chamber 1, as shown in Fig. 7, for example. Here, the first fermentation raw material A sent to the second sprinkler pipe 62 is referred to as the first fermentation raw material Ab.

[0059] Next, as shown in Fig. 7, the methane fermentation system 100 sprays water onto the first fermentation raw material Ab from above in the fermentation chamber 1 through spray holes (not shown) drilled in the second spray pipe 62. Here, the first fermentation raw material A sprayed from above in the fermentation chamber 1 is referred to as the first fermentation raw material Ac.

[0060] Next, in the methane fermentation system 100, as shown in Fig. 8, at least a portion of the first fermentation raw material Ac is sprayed from above the fermentation chamber 1 via the water pump 5 and the second sprinkler pipe 62 into the inside of the box body 2 in which the second fermentation raw material B has been previously accommodated. Here, the first fermentation raw material A supplied to the box body 2 is referred to as the first fermentation raw material Ad.

[0061] At this time, the second fermentation raw material B that has come into contact with the first fermentation raw material Ad undergoes methane fermentation due to the action of the methanogens. As a result, the second fermentation raw material B undergoes dry methane fermentation, and biogas and digested liquid are produced in the box body 2. The biogas produced from the second fermentation raw material B in the box body 2 moves upward within the fermentation chamber 1 and is collected in a gas collection tank T installed above the fermentation chamber 1.

[0062] <Separation process> 8, the methane fermentation system 100 passes the first fermentation raw material Ad through a separation hole 23 drilled in advance in the bottom plate 21 of the box body 2 and drops it into the second storage section 32 below the box body 2. Here, the first fermentation raw material A passing through the separation hole 23 is referred to as the first fermentation raw material Ae, and the first fermentation raw material A passing through the separation hole 23 and dropping into the second storage section 32 is referred to as the first fermentation raw material Af.

[0063] That is, the methane fermentation method of this embodiment includes a raw material supply step of supplying the first fermentation raw material A contained in the second storage section 32 to the box section 2 containing the second fermentation raw material B, and a separation step of separating the supplied first fermentation raw material A from the second fermentation raw material B by allowing it to fall through the separation hole 23. In this case, it is possible to prevent the high-moisture content second fermentation raw material B from collapsing and sticking to the inside of the fermentation chamber 1. This can improve the ease of transporting high-moisture content solid biomass and the ease of cleaning the fermentation chamber 1 in the methane fermentation system 100.

[0064] Similarly to the first fermentation raw material Ae, the digestion liquid generated from the second fermentation raw material B that has undergone dry methane fermentation inside the box-shaped portion 2 passes through the separation hole 23 and flows downward into the second storage portion 32. The digestion liquid that has flowed downward into the second storage portion 32 is discharged from the second storage portion 32 together with the first fermentation raw material Af or instead of the first fermentation raw material Af, and is sprayed from above the fermentation chamber 1 via the drain pipe 4, the water pump 5, and the second sprinkler pipe 62, and is supplied to the box-shaped portion 2.

[0065] At this time, in the second storage section 32, the first fermentation raw material A and the digestive liquid repeatedly flow down from the box section 2, stirring the first fermentation raw material A, which in turn promotes wet methane fermentation of the first fermentation raw material A and produces biogas and digestive liquid in the second storage section 32. The biogas produced from the first fermentation raw material A in the second storage section 32 moves upward within the fermentation chamber 1 and is collected in a gas collection tank T provided above the fermentation chamber 1.

[0066] The digested liquid produced in the second storage section 32 is supplied to the box-shaped section 2, which is above the second storage section 32, and then flows down into the second storage section 32. In this case, there is no need to provide an agitator for agitating the fermentation raw material, etc., to promote methane fermentation. This allows the methane fermentation system 100 to be made more compact. Furthermore, the digested liquid produced in the second storage section 32 may contain more eluted NPK components due to contact with the second fermentation raw material B stored in the box-shaped section 2 and the products of fermentation of the second fermentation raw material B. This increases the NPK component content, allowing the liquid to be used as a higher-quality bio-liquid fertilizer. This reduces the labor required for applying the liquid fertilizer, thereby improving the usefulness of the liquid fertilizer.

[0067] After the above-described steps are performed, the operation of the methane fermentation system 100 in this embodiment is completed. Note that in the methane fermentation system 100, the above-described steps may be repeatedly performed, for example.

[0068] (First Modification of Methane Fermentation System 100) In the methane fermentation system 100, for example, as shown in FIG. 9, the housing part 2 may include an upper housing part 2' and a lower housing part 2'' that accommodate the second fermentation raw materials B' and B'', respectively.

[0069] In addition, with respect to the upper box portion 2' and the lower box portion 2'', the bottom plates 21', 21'', the side plates 22', 22'', and the separation holes 23', 23'' have the same shapes and functions as the bottom plate 21, the side plate 22, and the separation hole 23, respectively. In addition, the second fermentation raw materials B', B'' are fermentation raw materials similar to the second fermentation raw material B.

[0070] That is, the methane fermentation system 100 comprises an upper box-shaped portion 2' which, when supplied, drops the first fermentation raw material A contained in the second storage portion 32 through the upper separation hole 23' to separate it from the contained second fermentation raw material B', and a lower box-shaped portion 2'' which, when supplied, drops the first fermentation raw material A that has dropped from the upper box-shaped portion 2' through the lower separation hole 23'', to separate it from the contained second fermentation raw material B''. In this case, a large amount of fermentation raw material can be fermented efficiently regardless of the volume of the box-shaped portion 2. This allows the methane fermentation system 100 to improve its biogas productivity.

[0071] 9 illustrates two adjacent upper and lower box sections 2′ and 2″ stacked in the height direction Z, but is not limited to this. The upper and lower box sections 2′ and 2″ may be, for example, any two adjacent box sections 2 among three or more box sections 2 stacked in the height direction Z, or any two spaced apart box sections 2. The upper and lower box sections 2′ and 2″ may be two box sections 2 that are spaced apart from each other in a plan view and are arranged at different heights, as long as the separation hole 23′ of the upper box section 2′ and the opening O of the lower box section 2″ are capable of supplying the first fermentation raw material A via a known resin pipe or the like.

[0072] Next, the methane fermentation method of this modified example will be described in detail.

[0073] <Raw material supply process> In the raw material supply step, the methane fermentation system 100 supplies at least a portion of the first fermentation raw material Ac, which has been sprayed from above the fermentation chamber 1 via the water pump 5 and the second sprinkler pipe 62, into the upper box portion 2' in which the second fermentation raw material B' has been previously accommodated, as shown in Figure 9. Here, the first fermentation raw material A supplied to the upper box portion 2' is referred to as the first fermentation raw material Ag.

[0074] At this time, the second fermentation raw material B' that has come into contact with the first fermentation raw material Ag undergoes methane fermentation due to the action of methanogens. As a result, the second fermentation raw material B' undergoes dry methane fermentation, and biogas and digested liquid are produced in the upper box section 2'. The biogas produced from the second fermentation raw material B' in the upper box section 2' moves upward within the fermentation chamber 1 and is collected in the gas collection tank T installed above the fermentation chamber 1.

[0075] <Separation process> In the separation process, the methane fermentation system 100 passes, for example, the first fermentation raw material Ag through a separation hole 23' drilled in advance in the bottom plate 21' of the upper box section 2' and drops it into the lower box section 2'' below the upper box section 2'. Here, the first fermentation raw material A that passes through the separation hole 23' and drops into the lower box section 2'' is referred to as the first fermentation raw material Ah.

[0076] Thereafter, the methane fermentation system 100 supplies at least a portion of the first fermentation raw material Ah that has passed through, for example, the upper separation hole 23' and fallen from the upper box portion 2' to the inside of the lower box portion 2'' in which the second fermentation raw material B'' has already been accommodated. Here, the first fermentation raw material A supplied to the lower box portion 2'' is referred to as the first fermentation raw material Ai.

[0077] At this time, the second fermentation raw material B" that has come into contact with the first fermentation raw material Ai undergoes methane fermentation due to the action of methanogens. As a result, the second fermentation raw material B" undergoes dry methane fermentation, and biogas and digested liquid are produced in the lower box portion 2". The biogas produced from the second fermentation raw material B" in the lower box portion 2" moves upward within the fermentation chamber 1 and is collected in the gas collection tank T located above the fermentation chamber 1.

[0078] Thereafter, the methane fermentation system 100 passes, for example, the first fermentation raw material Ai through a separation hole 23'' pre-drilled in the bottom plate 21'' of the lower box body portion 2'' and drops it into the second storage portion 32 below the lower box body portion 2''. Here, the first fermentation raw material A passing through the separation hole 23'' is referred to as the first fermentation raw material Aj, and the first fermentation raw material A passing through the separation hole 23 and dropping into the second storage portion 32 is referred to as the first fermentation raw material Ak.

[0079] That is, in the methane fermentation method of this modified example, in the raw material supply step, the first fermentation raw material A stored in the second storage section 32 is supplied to the upper box section 2' storing the second fermentation raw material B'. In the separation step, the first fermentation raw material A supplied in the raw material supply step is allowed to fall through the separation holes 23' to be separated from the second fermentation raw material B', and the first fermentation raw material A supplied to the lower box section 2'' storing the second fermentation raw material B'' is allowed to fall through the separation holes 23'' to be separated from the second fermentation raw material B''. In this case, a large amount of fermentation raw material can be fermented efficiently regardless of the volume of the box section 2. This can improve the biogas productivity of the methane fermentation system 100.

[0080] (Second Modification of Methane Fermentation System 100) 10 , the methane fermentation system 100 may have the accommodation section 3 (underfloor accommodation section 34) located below the floor surface 12 of the fermentation chamber 1 and separated from the fermentation chamber 1. The methane fermentation system 100 may further include, for example, a gas recovery pipe 7, a gas pump 8, and a gas injection pipe 9.

[0081] In addition, the sprinkler pipe 6 may further have, for example, a first sprinkler pipe 61 branching off from a base extending in the first horizontal direction X and extending in the second horizontal direction Y, and a second sprinkler pipe 62 branching off from the first sprinkler pipe 61 and extending in the first horizontal direction X.

[0082] <Underfloor storage space 34> The underfloor storage section 34 is provided, for example, below the floor surface 12 of the fermentation chamber 1. The underfloor storage section 34 stores the first fermentation raw material having a TS of less than 15%. The underfloor storage section 34 is connected (communicates) with the fermentation chamber 1, and the first fermentation raw material and the like in the fermentation chamber 1 fall into and flow into the underfloor storage section 34.

[0083] 10 , the underfloor storage section 34 is provided vertically below the floor surface 12 and is connected to the fermentation chamber 1 via one or more perforations 121 drilled through a portion of the floor surface 12. That is, when cleaning the inside of the fermentation chamber 1, cleaning water drops into the underfloor storage section 34 via the perforations 121 and fills the underfloor storage section 34. Therefore, the inside of the fermentation chamber 1 and the inside of the underfloor storage section 34 can be cleaned simultaneously by cleaning the inside of the fermentation chamber 1 and the underfloor storage section 34 and pumping the cleaning water out of the underfloor storage section 34. In this case, the time required for cleaning the methane fermentation system 100 can be shortened. This improves the cleaning workability of the methane fermentation system 100.

[0084] The shape and dimensions of the underfloor storage section 34 are arbitrary as long as it has enough space to store the first fermentation raw material, but for example it is a roughly rectangular parallelepiped with a width of 1 to 10 m, a height of 1 to 10 m, and a depth of 1 to 50 m.

[0085] <Gas recovery pipe 7> One end of the gas recovery pipe 7 is disposed inside the fermentation chamber 1, and the other end is connected to a gas pump 8. The gas recovery pipe 7 recovers, for example, biogas produced by fermentation of the second fermentation raw material contained in the box portion 2 inside the fermentation chamber 1. The gas recovery pipe 7 is made of, for example, resin.

[0086] The gas recovery pipe 7 may further include a first gas recovery pipe 71 and a second gas recovery pipe 72 branching off from a base portion extending in the first horizontal direction X, for example.

[0087] <Gas Pump 8> One end of the gas pump 8 is connected to the gas recovery pipe 7, and the other end is connected to the gas injection pipe 9. The gas pump 8 sends the biogas discharged from the fermentation chamber 1 to the gas recovery pipe 7 to the gas injection pipe 9. As the gas pump 8, for example, a known gas pump can be used.

[0088] <Gas injection pipe 9> One end of the gas blowing pipe 9 is connected to the gas pump 8, and the other end is disposed inside the underfloor storage section 34. The gas blowing pipe 9 blows the biogas discharged from the fermentation chamber 1 into the first fermentation raw material stored in the underfloor storage section 34. The gas blowing pipe 9 is made of a material such as resin.

[0089] The gas blowing pipe 9 may further include a first gas blowing pipe 91 and a second gas blowing pipe 92 branching from a base portion extending in the first horizontal direction X, for example.

[0090] That is, in the methane fermentation system 100, the storage section 3 (underfloor storage section 34) is supplied with gas produced by the box section 2. That is, the biogas produced by the box section 2 comes into contact with the first fermentation raw material and the products of fermentation of the first fermentation raw material stored in the storage section 3, and hydrogen sulfide and ammonia in the biogas may be eluted. In this case, there is no need to provide equipment for desulfurization and ammonia removal of the produced biogas. This allows for the miniaturization of the methane fermentation apparatus. Furthermore, because carbon dioxide in the produced biogas is also eluted in the same way, it is possible to produce biogas with a purified methane concentration and high calorific value. This reduces the costs required for gas transportation, storage, etc., and improves the usefulness of biogas.

[0091] Next, the methane fermentation method of this modified example will be described in detail. Figures 11 to 14 are schematic cross-sectional views showing an example of the operation of the methane fermentation system corresponding to the cross section BB of Figure 10.

[0092] <Advance preparation> As a preliminary preparation, for example, as shown in Fig. 11, the first fermentation raw material A is stored in advance in the underfloor storage section 34, and the second fermentation raw material B is stored in advance in the box body section 2. Methane-producing bacteria are already present in the first fermentation raw material A or the second fermentation raw material B. Here, the first fermentation raw material A stored in the underfloor storage section 34 is referred to as the first fermentation raw material Al.

[0093] Here, the box body 2 may be installed on the floor surface 12 via the legs 24, for example, by attaching the legs 24 to the bottom plate 21 in advance. In this case, a space is formed between the bottom plate 21 and the floor surface 12, so that the supplied first fermentation raw material A can pass through the separation holes 23 even if the box body 2 is not placed in the fermentation chamber 1 so that the separation holes 23 and the perforations 121 overlap in plan view.

[0094] In addition, in order to create an anaerobic environment in the fermentation chamber 1 that promotes methane fermentation, the worker U places the first fermentation raw material A and the second fermentation raw material B in the fermentation chamber 1 with the opening / closing section 11 open, then closes the opening / closing section 11 to seal the fermentation chamber 1, and degass (deoxygenate) the fermentation chamber 1 as necessary.

[0095] <Raw material supply process> In the raw material supply step, the methane fermentation system 100 drains the first fermentation raw material A by flowing it from the underfloor storage section 34 to the drain pipe 4 via the water pump 5, as shown in Fig. 12, for example. Thereafter, the methane fermentation system 100 sends the first fermentation raw material Am drained into the drain pipe 4 to a second sprinkler pipe 62 installed above the fermentation chamber 1, for example. Here, the first fermentation raw material A sent to the second sprinkler pipe 62 is referred to as the first fermentation raw material An.

[0096] Next, the methane fermentation system 100 sprays water onto, for example, the first fermentation raw material An from above in the fermentation chamber 1 through spray holes (not shown) drilled in the second spray pipe 62. Here, the first fermentation raw material A sprayed from above in the fermentation chamber 1 is referred to as the first fermentation raw material Ao.

[0097] Next, in the methane fermentation system 100, as shown in Fig. 13, at least a portion of the first fermentation raw material Ao sprayed from above the fermentation chamber 1 via the water pump 5 and the second sprinkler pipe 62 is supplied into the inside of the box body 2 which has previously contained the second fermentation raw material B. Here, the first fermentation raw material A supplied to the box body 2 is referred to as the first fermentation raw material Ap.

[0098] At this time, the second fermentation raw material B that has come into contact with the first fermentation raw material Ap undergoes methane fermentation due to the action of methanogens. As a result, the second fermentation raw material B undergoes dry methane fermentation, and biogas Ga (G) and digested liquid are produced in the box body 2. The biogas Ga produced from the second fermentation raw material B in the box body 2 moves upward within the fermentation chamber 1 and is recovered in a gas recovery pipe 7 installed above the fermentation chamber 1. Here, the biogas G recovered in the gas recovery pipe 7 is referred to as biogas Gb.

[0099] The gas pump 8 then injects the biogas Gb collected in the gas collection pipe 7 into the first fermentation raw material Al stored in the underfloor storage section 34 via the gas injection pipe 9. Here, the biogas G sent to the underfloor storage section 34 is referred to as biogas Gc, and the biogas G injected into the first fermentation raw material Al in the underfloor storage section 34 is referred to as biogas Gd. After some components of the biogas Gd come into contact with the first fermentation raw material Al and are eluted, the biogas Gd passes through the perforations 121 and flows into the fermentation chamber 1, and is then collected in the gas collection pipe 7 together with or instead of the biogas Ga.

[0100] <Separation process> 14, the methane fermentation system 100 passes the first fermentation raw material Ap through separation holes 23 drilled in advance in the bottom plate 21 of the box body 2 and drops it into the underfloor storage section 34 below the box body 2. Here, the first fermentation raw material A passing through the separation holes 23 is referred to as the first fermentation raw material Aq, the first fermentation raw material A passing through the separation holes 23 and flowing on the floor surface 12 is referred to as the first fermentation raw material Ar, and the first fermentation raw material A passing through the perforations 121 from the floor surface 12 and dropping into the underfloor storage section 34 is referred to as the first fermentation raw material As.

[0101] Similarly to the first fermentation raw material Aq, the digestion liquid generated from the second fermentation raw material B that has undergone dry methane fermentation inside the box-body part 2 passes through the separation holes 23 and flows on the floor surface 12, passes through the perforations 121, and flows down into the underfloor storage part 34. The digestion liquid that has flowed down into the underfloor storage part 34 is discharged from the underfloor storage part 34 together with or instead of the first fermentation raw material As, and is sprayed from above the fermentation chamber 1 via the drain pipe 4, the water pump 5, and the second sprinkler pipe 62, and is supplied to the box-body part 2.

[0102] At this time, in the underfloor storage section 34, the first fermentation raw material A and the digestive liquid repeatedly flow down from the box section 2, stirring the first fermentation raw material A, which promotes wet methane fermentation of the first fermentation raw material A and produces biogas and digestive liquid in the underfloor storage section 34. The biogas produced from the first fermentation raw material A in the underfloor storage section 34 moves upward within the fermentation chamber 1 and is collected in a gas collection pipe 7 provided above the fermentation chamber 1.

[0103] The digested liquid produced in the underfloor storage section 34 is supplied to the box-shaped section 2, which is above the underfloor storage section 34, and then flows down into the underfloor storage section 34. In this case, there is no need to provide an agitator for agitating the fermentation raw material, etc., to promote methane fermentation. This allows the methane fermentation system 100 to be made more compact. Furthermore, the digested liquid produced in the underfloor storage section 34 may contain more eluted NPK components due to contact with the second fermentation raw material B stored in the box-shaped section 2 and the products of fermentation of the second fermentation raw material B. This increases the NPK component content, allowing the liquid to be used as a higher-quality bio-liquid fertilizer. This reduces the labor required for applying the liquid fertilizer, thereby improving the usefulness of the liquid fertilizer.

[0104] According to this embodiment, the methane fermentation system 100 is provided with a box section 2 that, when supplied, drops the first fermentation raw material 7 stored in a storage section 3 provided below the floor surface 12 of the fermentation chamber 1 through a separation hole 23 to separate it from the second fermentation raw material 8. This prevents the high-moisture content second fermentation raw material 8 from collapsing and sticking to the inside of the fermentation chamber 1. This improves the ease of transporting high-moisture solid biomass and the ease of cleaning the fermentation chamber 1 in the methane fermentation system 100.

[0105] Furthermore, according to this embodiment, the methane fermentation system 100 is provided with an upper box-shaped portion 2' that, when supplied, drops the first fermentation raw material 7 contained in the storage portion 3 through the upper separation hole 23' to separate it from the contained second fermentation raw material 8', and a lower box-shaped portion 2'' that, when supplied, drops the first fermentation raw material 7 that has dropped from the upper box-shaped portion 2' through the lower separation hole 23'' to separate it from the contained second fermentation raw material 8''. Therefore, a large amount of fermentation raw material can be fermented efficiently regardless of the volume of the box-shaped portion 2. This allows the methane fermentation system 100 to improve its biogas productivity.

[0106] Furthermore, according to this embodiment, the storage unit 3 is supplied with the biogas G produced by the box-shaped unit 2. That is, the biogas G produced by the box-shaped unit 2 comes into contact with the first fermentation raw material A and the products of fermentation of the first fermentation raw material A stored in the storage unit 3, and hydrogen sulfide and ammonia in the biogas G may be eluted. Therefore, there is no need to provide equipment for desulfurization and ammonia removal of the generated biogas G. This allows for the miniaturization of the methane fermentation apparatus. Furthermore, because carbon dioxide in the generated biogas G is also eluted in the same manner, it is possible to produce biogas G with a purified methane concentration and high calorific value. This reduces the costs required for gas transportation, storage, etc., and improves the usefulness of the biogas G.

[0107] Furthermore, according to this embodiment, the methane fermentation method includes a raw material supplying step of supplying the first fermentation raw material 7 stored in the storage section 3 provided below the floor surface 12 of the fermentation chamber 1 to the box section 2 storing the second fermentation raw material 8, and a separation step of separating the supplied first fermentation raw material 7 from the second fermentation raw material 8 by allowing it to fall through the separation holes 23. This makes it possible to prevent the high-moisture second fermentation raw material 8 from collapsing and sticking to the inside of the fermentation chamber. This improves the ease of unloading high-moisture solid biomass and the ease of cleaning the fermentation chamber 1 in the methane fermentation system 100.

[0108] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0109] 100 Methane Fermentation System 1 Fermentation room 11 Opening and Closing Section 12 Floor 121 Perforation 13 Wall 14 Ceiling 2 Box part 2' Upper box part 2'' Lower Case 21, 21', 21'' bottom plate 22, 22', 22'' side panels 23, 23', 23'' separation hole 24 Legs 3. Storage section 31, 32, 33 Storage section 34 Underfloor storage area 4. Drainage pipe 5. Water pump 6. Watering pipe 61, 62, 63, 64, 65 Sprinkler pipes 7, 71, 72 Gas recovery pipes 8. Gas Pump 9, 91, 92 Gas injection pipe A, Aa-As First fermentation raw material B, B', B'' Second fermentation ingredients G, Ga~Gd Biogas T Gas collection tank O opening U Worker

Claims

1. Fermentation room and A storage section provided below the floor surface of the fermentation chamber and configured to store a first fermentation raw material having a TS (solid concentration) of less than 15%; a box portion installed in the fermentation chamber and containing a second fermentation raw material having a TS of 15% or more; Equipped with When the first fermentation raw material contained in the container is supplied and comes into contact with the second fermentation raw material, the box portion separates at least a part of the first fermentation raw material from the second fermentation raw material by dropping the first fermentation raw material through a separation hole formed in a bottom plate. A methane fermentation system characterized by:

2. the case includes an upper case and a lower case, each of which accommodates the second fermentation raw material; When the first fermentation raw material contained in the containing section is supplied and contacts the second fermentation raw material, the upper case section separates at least a portion of the first fermentation raw material from the second fermentation raw material by dropping the first fermentation raw material through an upper separation hole formed in a bottom plate of the upper case section, When the first fermentation raw material dropped from the upper case part is supplied and contacts the second fermentation raw material, the lower case part separates at least a part of the first fermentation raw material from the second fermentation raw material by dropping the first fermentation raw material through a lower separation hole formed in a bottom plate of the lower case part. The methane fermentation system according to claim 1,

3. the housing portion is supplied with the first fermentation raw material to generate biogas, The storage section is supplied with the biogas generated by the box section.

3. The methane fermentation system according to claim 1 or 2,

4. a raw material supplying step of supplying the first fermentation raw material accommodated in an accommodation section that is provided below the floor surface of the fermentation chamber and accommodates a first fermentation raw material having a TS of less than 15% into a box section that is provided in the fermentation chamber and accommodates a second fermentation raw material having a TS of 15% or more; a separation step of separating at least a portion of the first fermentation raw material that has been supplied to the box portion in the raw material supply step and has come into contact with the second fermentation raw material by passing through a separation hole formed in a bottom plate of the box portion and dropping the first fermentation raw material from the second fermentation raw material; Having A methane fermentation method characterized by:

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