Microbial mass calculation device and microbial mass calculation method

Abstract

To provide a microbial level calculation device and a microbial level calculation method that can suppress excessive consumption of microbes for methane fermentation.SOLUTION: A processor 212 of a control device 210 includes an oxygen level acquisition unit 212a that acquires the oxygen level in biomass to be put into a methane fermentation tank 12, and a microbial level calculation unit 212d that calculates the level of microbes to be put into the methane fermentation tank 12 for methane fermentation of biomass.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a microbial biomass calculation apparatus and a microbial biomass calculation method. [Background Art]

[0002] Conventionally, it is known to generate biogas (methane) from biomass, which is a renewable resource derived from organisms such as wood, livestock manure, and food waste (for example, Patent Document 1). [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-107233 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] However, when generating biogas from biomass, if methanogens for methane fermentation are excessively added into a fermentation tank, there arises a problem that the methanogens are excessively consumed.

[0005] In view of the above problem, an object of the present disclosure is to provide a microbial biomass calculation apparatus and a microbial biomass calculation method that can suppress excessive consumption of microorganisms for methane fermentation. [Means for Solving the Problem]

[0006] The gist of the present disclosure is as follows.

[0007] (1) an oxygen amount acquisition unit that acquires an oxygen amount contained in biomass introduced into a methane fermentation tank; a microbial biomass calculation unit that calculates an amount of microorganisms to be introduced into the methane fermentation tank for methane fermentation of the biomass in accordance with the oxygen amount; and a microbial biomass calculation apparatus comprising:

[0008] (2) The microbial amount calculation device according to (1) above, wherein the microbial amount calculation unit calculates the amount of microorganisms such that the amount of microorganisms increases as the amount of oxygen increases.

[0009] (3) The methane fermentation tank is further equipped with a microbial quantity acquisition unit for acquiring the amount of microorganisms remaining in the tank. The microbial amount calculation device according to (1) or (2) above, wherein the microbial amount calculation unit calculates the amount of microorganisms to be introduced into the methane fermentation tank based on the amount of oxygen and the amount of microorganisms remaining in the methane fermentation tank.

[0010] (4) Further comprising a molecular weight acquisition unit for obtaining the molecular weight of substances contained in biomass, The microbial amount calculation unit calculates the amount of microorganisms such that the amount of microorganisms to be introduced into the methane fermentation tank increases as the amount of substances with high molecular weights in the biomass increases, as described in any of (1) to (3) above.

[0011] (5) Obtain the amount of oxygen contained in the biomass that is put into the methane fermentation tank, The amount of microorganisms to be introduced into the methane fermentation tank to ferment biomass into methane, according to the amount of oxygen, A method for calculating microbial mass, comprising the following features.

[0012] (6) The method for calculating the amount of microorganisms as described in (5) above, wherein the amount of microorganisms is calculated such that the amount of microorganisms increases as the amount of oxygen increases.

[0013] (7) Further comprising obtaining the amount of microorganisms remaining in the methane fermentation tank, A method for calculating the amount of microorganisms to be introduced into a methane fermentation tank, as described in (5) or (6) above, based on the amount of oxygen and the amount of microorganisms remaining in the methane fermentation tank.

[0014] (8) Further comprising obtaining the molecular weight of substances contained in biomass, The method for calculating the amount of microorganisms according to any one of the above (5) to (7), wherein the amount of said microorganisms to be introduced into the methane fermentation tank is calculated such that the more substances having a large molecular weight are contained in biomass, the larger the amount of said microorganisms. [Effects of the Invention]

[0015] According to the present disclosure, there is provided a microorganism amount calculation apparatus and a microorganism amount calculation method capable of suppressing excessive consumption of microorganisms for methane fermentation. [Brief Description of Drawings]

[0016] [Figure 1] It is a diagram schematically showing a treatment step of generating biogas from biomass. [Figure 2] It is a diagram showing an example of a map that defines the relationship between the oxygen content contained in biomass and the amount of methanogenic bacteria to be introduced. [Figure 3] It is a schematic diagram showing the configuration of an information processing apparatus for calculating the amount of microorganisms. [Figure 4] It is a schematic diagram showing functional blocks of a processor of a control device provided in the information processing apparatus. [Figure 5] It is a flowchart showing processing performed by a processor of a control device provided in the information processing apparatus. [Mode for Carrying Out the Invention]

[0017] Hereinafter, several embodiments according to the present invention will be described with reference to the drawings. However, these descriptions are intended merely as examples of preferred embodiments of the present invention, and are not intended to limit the present invention to such specific embodiments. In the following description, the same reference numerals are assigned to similar constituent elements.

[0018] Biomass is collected from business establishments such as factories, households, or the like. When biomass is introduced into a methane fermentation tank and methanogenic bacteria (hereinafter also simply referred to as microorganisms) are added, biogas containing methane, carbon dioxide, and the like is generated.

[0019] Fig. 1 is a diagram schematically showing treatment process 100 for generating biogas from biomass. Biomass contains organic substances such as carbohydrates, proteins, fats, and fibers. These organic substances are converted into low-molecular-weight compounds including monosaccharides and lower fatty acids through hydrolysis and acid fermentation in an acid fermentation tank 10. During the acid fermentation, acid-fermenting bacteria are introduced into the acid fermentation tank 10.

[0020] Monosaccharides, lower fatty acids and the like obtained by acid fermentation are introduced in a liquefied state into a methane fermentation tank 12. In addition, methanogens are introduced into the methane fermentation tank 12. In the methane fermentation tank 12, biogas containing methane, carbon dioxide and the like is generated through methane fermentation under an anaerobic atmosphere. Methane gas contained in the biogas is used as fuel, for example, for power generation. Carbon dioxide contained in the biogas can also be used for applications such as agricultural purposes. Further, the remaining fermented processed product is used as fertilizer or the like.

[0021] During methane fermentation, if the amount of methanogens introduced into the methane fermentation tank 12 is excessive relative to the biomass, the excess methanogens do not contribute to the reaction and die. In this case, although biogas can be generated from the biomass, methanogens will be consumed excessively.

[0022] The amount of methanogens required for methane fermentation is determined by the oxygen content contained in the biomass. For example, fermentation from a monosaccharide (glucose (C6H 12 O6)) is represented by the following chemical formula. C6H 12 O6→3CO2+3CH4···(1)

[0023] As shown in the chemical formula above, methane fermentation produces amounts of carbon dioxide (CO2) and methane (CH4) corresponding to the amount of oxygen contained in the biomass raw material. Furthermore, the methane-producing bacteria that ferment the biomass depend on the oxygen in the biomass to survive; they cannot survive if the oxygen level is low. Therefore, the amount of methane-producing bacteria needed for biomass fermentation is also determined by the oxygen level, and the amount of methane-producing bacteria that contributes to the reaction is proportional to the oxygen level. Consequently, if an excessive amount of methane-producing bacteria is added relative to the oxygen level in the biomass, the excess bacteria will not contribute to the reaction and will die. On the other hand, if too little methane-producing bacteria is added relative to the oxygen level in the biomass, the amount of biogas produced will decrease, and the decomposition efficiency of methane fermentation will decline. Therefore, it is necessary to add an optimal amount of methane-producing bacteria relative to the oxygen level in the biomass.

[0024] Therefore, in this embodiment, the amount of oxygen contained in the biomass (chemical oxygen demand (COD)) is detected before methane fermentation. The amount of methane-producing bacteria to be introduced into the methane fermentation tank 12 is then determined according to the detected amount of oxygen. As a result, the correct amount of methane-producing bacteria necessary for methane fermentation is introduced into the methane fermentation tank 12, preventing excessive consumption of methane-producing bacteria and enabling efficient biogas generation.

[0025] The amount of oxygen (COD) in biomass is detected by a method using potassium permanganate solution, as shown in JIS K0102 "Test Methods for Industrial Wastewater." In this case, for example, an arbitrary amount (weight or volume) is quantitatively taken from the biomass before methane fermentation, and the amount of oxygen (expressed as the mass of oxygen atoms) is detected by adding potassium permanganate solution to it. Then, the amount of oxygen contained in the total amount of biomass is determined by multiplying the detected amount of oxygen by a coefficient obtained by dividing the total amount of biomass (weight or volume) by the arbitrary amount mentioned above. Note that the detection of the amount of oxygen is performed before inputting into the acid fermentation tank 10 or before inputting into the methane fermentation tank 12. The detection of the amount of oxygen (COD) may also be performed using an automatic COD measuring instrument specified in JIS K0806 "Automatic Chemical Oxygen Consumption (COD) Measuring Instruments."

[0026] The relationship between the amount of oxygen contained in the biomass and the amount of methane-producing bacteria introduced is predetermined, for example, by a map. Figure 2 shows an example of a map that defines the relationship between the amount of oxygen contained in the biomass and the amount of methane-producing bacteria (microbial mass) introduced. As shown in Figure 2, there is basically a linear relationship between the amount of oxygen contained in the biomass and the amount of methane-producing bacteria introduced: the more oxygen contained in the biomass, the greater the amount of methane-producing bacteria that can be introduced. This relationship may be estimated from the chemical formula of methane fermentation, or it may be determined experimentally. Once the amount of oxygen contained in the biomass is determined by the method described above, the amount of methane-producing bacteria to be introduced can be determined by applying the determined amount of oxygen to the map. As a result, an amount of methane-producing bacteria corresponding to the amount of oxygen contained in the biomass is introduced into the methane fermentation tank 12.

[0027] When adding new biomass after biogas has been generated from the first batch of biomass, theoretically, the methane-producing bacteria should not die during the first fermentation process, provided that the amount of methane-producing bacteria added is appropriate relative to the amount of biomass added in the first batch. Therefore, when adding new biomass after biogas has been generated from the first batch of biomass, it is sufficient to add approximately the same amount of biomass as the first batch.

[0028] On the other hand, it is conceivable that the amount of methane-producing bacteria may increase or decrease during the fermentation process due to various factors. For example, if the amount of methane-producing bacteria is excessive relative to the amount of oxygen in the biomass at the time of the first input, the excess methane-producing bacteria will die, and the amount of methane-producing bacteria will decrease. For this reason, at the time of the second input, the amount of new biomass or methane-producing bacteria to be added may be adjusted according to the amount of methane-producing bacteria remaining in the methane fermentation tank 12.

[0029] In this case, after generating biogas from the biomass introduced the first time, when introducing new biomass, the amount of biomass introduced may be increased or decreased compared to the first input amount, taking into account the increase or decrease in methane-producing bacteria due to the first fermentation.

[0030] Alternatively, the amount of newly introduced microorganisms may be adjusted by subtracting the amount of remaining methane-producing bacteria from the amount of microorganisms determined from the amount of oxygen contained in the newly introduced biomass. For example, if the amount of methane-producing bacteria decreases after the first fermentation, the amount of methane-producing bacteria may be replenished by the same amount as the first time, and the same amount of biomass may be introduced.

[0031] As a result, even if the number of methane-producing bacteria increases or decreases during the first fermentation, when biomass is added for the second time, there will be an appropriate amount of methane-producing bacteria in the methane fermentation tank 12 relative to the amount of biomass. This suppresses excessive consumption of methane-producing bacteria and allows for efficient biogas generation. Subsequently, the amount of biomass and methane-producing bacteria added to the methane fermentation tank 12 will be appropriately controlled using the same method.

[0032] The amount of methanogenic bacteria remaining in the methane fermentation tank 12 is detected by methods such as the EB fluorescence method or the CFDA fluorescence method. If the amount of methanogenic bacteria decreases during the first fermentation process, the amount of decrease in methanogenic bacteria can be determined from the difference between the amount of methanogenic bacteria at the time of the first input and the amount of methanogenic bacteria remaining in the methane fermentation tank 12 after fermentation.

[0033] Next, we will explain a method for more accurately determining the amount of methane-producing bacteria to be introduced into the methane fermentation tank 12. As mentioned above, the amount of methane-producing bacteria to be introduced into the methane fermentation tank 12 is basically determined by the amount of oxygen contained in the biomass. On the other hand, in order to more accurately determine the amount of methane-producing bacteria to be introduced into the methane fermentation tank 12, it is preferable to increase the amount of methane-producing bacteria as the molecular weight of the substances contained in the biomass increases.

[0034] Typically, biomass contains various substances such as fatty acids, sulfuric acid, and acetic acid. For example, if biomass contains only glucose and no other substances, the amount of methanogenic bacteria required in proportion to the detected oxygen level is sufficient for methane fermentation. However, if the biomass contains substances with higher molecular weights than glucose, simply adding the amount of methanogenic bacteria corresponding to the detected oxygen level may result in an insufficient amount of methanogenic bacteria, potentially leading to incomplete fermentation. Thus, the higher the molecular weight of the substances in the biomass, the more methanogenic bacteria are actually required.

[0035] Therefore, in order to more accurately determine the amount of methanogenic bacteria to be introduced into the methane fermentation tank 12, it is preferable to measure the molecular weight of the substances contained in the biomass and increase the amount of methanogenic bacteria as the biomass contains more substances with high molecular weights. As a method for measuring the molecular weight of substances (polymers) contained in the biomass, for example, size exclusion chromatography (SEC) can be used to obtain information on the average molecular weight and molecular weight distribution simultaneously.

[0036] The relationship between the amount of oxygen in the biomass, the molecular weight of the substances in the biomass, and the amount of methane-producing bacteria to be introduced is predetermined, for example, by a map. This relationship may also be determined experimentally. Once the amount of oxygen in the biomass and the molecular weight of the substances in the biomass are determined, the amount of methane-producing bacteria to be introduced can be determined by applying these to the map. This improves the accuracy of the relationship between the amount of methane-producing bacteria and the amount of biomass introduced, suppresses excessive consumption of methane-producing bacteria, and enables efficient biogas generation.

[0037] Furthermore, the activity level of methanogenic bacteria is affected by temperature, with lower temperatures resulting in lower activity. Therefore, more methanogenic bacteria can be added at lower temperatures.

[0038] Figure 3 is a schematic diagram showing the configuration of an information processing system 200 for calculating the amount of methane-producing bacteria to be introduced into the methane fermentation tank 12. The information processing system 200 includes a control device 210, a storage device 220, and an input device 230.

[0039] The control device 210 includes a processor 212, a memory 214, and a communication interface 216. The processor 212 has one or more CPUs (Central Processing Units) and their peripheral circuits. The processor 212 may further have other arithmetic circuits such as a logic unit, a numerical unit, or a graphics processing unit. The processor 212 provides functions that match a predetermined purpose by executing a computer program that is executablely deployed in the working area of ​​the memory 214. The memory 214 includes, for example, volatile semiconductor memory and non-volatile semiconductor memory. Various types of information are stored in the memory 214. The communication interface 216 has an interface circuit for connecting the control device 210 to a network within the information processing system 200 or to a communication network such as the Internet.

[0040] The storage device 220 includes, for example, a hard disk drive or an optical recording medium and its access device. The storage device 220 stores a map that defines the relationship between the amount of oxygen contained in the biomass and the amount of methane-producing bacteria introduced. The storage device 220 also stores a map that defines the relationship between the amount of oxygen contained in the biomass, the molecular weight of the substances contained in the biomass, and the amount of methane-producing bacteria introduced. The storage device 220 may also store a computer program for executing processes performed on the processor 212.

[0041] The input device 230 is a user interface such as a keyboard or mouse, and various information is input through user operation. The information input to the input device 230 includes the amount of oxygen contained in the biomass, the amount of microorganisms remaining in the methane fermentation tank 12, and the molecular weight of substances contained in the biomass, which are detected by the method described above.

[0042] Figure 4 is a schematic diagram showing the functional blocks of the processor 212 of the control device 210 provided in the information processing system 200. The processor 212 of the control device 210 is one embodiment of the microbial quantity calculation device according to this disclosure and includes an oxygen quantity acquisition unit 212a, a microbial quantity acquisition unit 212b, a molecular weight acquisition unit 212c, and a microbial quantity calculation unit 212d. Each of these parts of the processor 212 is a functional module realized, for example, by a computer program running on the processor 212. In other words, each of these parts of the processor 212 consists of the processor 212 and a program (software) to make it function. The program may also be recorded in the memory 214 of the control device 210 or on an externally connected recording medium. Alternatively, each of these parts of the processor 212 may be a dedicated arithmetic circuit provided on the processor 212.

[0043] The oxygen amount acquisition unit 212a of the processor 212 acquires the amount of oxygen contained in the biomass that is fed into the methane fermentation tank 12. The oxygen amount acquisition unit 212a acquires the amount of oxygen that is detected by the method shown in the above-mentioned JIS K0102 "Test Method for Factory Wastewater" and input to the input device 230.

[0044] The microbial quantity acquisition unit 212b of the processor 212 acquires the amount of microorganisms remaining in the methane fermentation tank 12. The microbial quantity acquisition unit 212b acquires the amount of microorganisms detected by the EB fluorescence method, CFDA fluorescence method, etc., as described above, and input to the input device 230.

[0045] The molecular weight acquisition unit 212c of the processor 212 acquires the molecular weight of substances contained in the biomass. The molecular weight acquisition unit 212c acquires the molecular weight that has been measured by the size exclusion chromatography or the like described above and input to the input device 230.

[0046] The microbial quantity calculation unit 212d of the processor 212 calculates the amount of microorganisms to be introduced into the methane fermentation tank 12 for methane fermentation of biomass, according to the amount of oxygen contained in the biomass. For example, the microbial quantity calculation unit 212d calculates the amount of microorganisms by applying the amount of oxygen acquired by the oxygen acquisition unit 212a to the map in Figure 2. The microbial quantity calculation unit 212d calculates the amount of microorganisms such that the amount of methane-producing bacteria increases as the amount of oxygen increases.

[0047] The microbial quantity calculation unit 212d may calculate the amount of microorganisms based on the amount of oxygen contained in the biomass and the amount of microorganisms remaining in the methane fermentation tank 12. For example, the microbial quantity calculation unit 212d may calculate the amount of microorganisms to be introduced into the methane fermentation tank by subtracting the amount of microorganisms remaining in the methane fermentation tank 12 from the amount of microorganisms determined from the amount of oxygen contained in the biomass. Alternatively, the microbial quantity calculation unit 212d may calculate the amount of microorganisms such that the amount of microorganisms increases as the amount of substances with high molecular weights in the biomass increases.

[0048] Figure 5 is a flowchart showing the processing performed by the processor 212 of the control device 210 provided in the information processing system 200. First, the oxygen amount acquisition unit 212a of the processor 212 acquires the amount of oxygen contained in the biomass introduced into the methane fermentation tank 12 (step S10). Next, the microbial amount acquisition unit 212b of the processor 212 acquires the amount of microorganisms remaining in the methane fermentation tank 12 (step S12).

[0049] Next, the molecular weight acquisition unit 212c of the processor 212 acquires the molecular weight of the substances contained in the biomass (step S14). Next, the microbial amount calculation unit 212d of the processor 212 calculates the amount of microorganisms to be introduced into the methane fermentation tank 12 for methane fermentation of the biomass, according to the amount of oxygen contained in the biomass (step S16). In step S16, the microbial amount calculation unit 212d may calculate the amount of microorganisms based on the amount of oxygen and the amount of microorganisms remaining in the methane fermentation tank 12. Alternatively, in step S16, the microbial amount calculation unit 212d may calculate the amount of microorganisms such that the amount of microorganisms increases as the amount of substances with high molecular weights in the biomass increases.

[0050] As described above, according to this embodiment, the amount of microorganisms to be introduced into the methane fermentation tank 12 for methane fermentation of biomass is calculated according to the amount of oxygen contained in the biomass, and the calculated amount of microorganisms is introduced into the methane fermentation tank 12. Therefore, the amount of microorganisms necessary for methane fermentation is introduced into the methane fermentation tank 12 without excess or deficiency, so that excessive consumption of microorganisms is suppressed and biogas can be generated efficiently. [Explanation of Symbols]

[0051] 10. Acid fermentation tank 12 methane fermentation tanks 100 processing steps 200 Information Processing Devices 210 Control device 212 processors 212a Oxygen quantity acquisition unit 212b Microbial Amount Acquisition Department 212c Molecular weight acquisition section 212d Microbial amount calculation department 214 memory 216 Communication Interfaces 220 storage devices 230 Input devices

Claims

1. An oxygen quantity acquisition unit that acquires the amount of oxygen contained in biomass that is introduced into a methane fermentation tank in a liquefied state, expressed as the mass of oxygen atoms, A molecular weight acquisition unit that obtains the molecular weight of substances contained in biomass, A microorganism quantity calculation unit calculates the amount of microorganisms to be introduced into a methane fermentation tank for methane fermentation of biomass, based on the relationship between the amount of oxygen contained in the biomass, the molecular weight of the substances contained in the biomass, and the amount of microorganisms to be introduced into the methane fermentation tank, according to the amount of oxygen obtained, and calculates the amount of microorganisms to be introduced into the methane fermentation tank in such a way that the amount of microorganisms introduced into the methane fermentation tank increases as the amount of substances with high molecular weight contained in the biomass increases. A device for calculating microbial mass, equipped with the necessary components.

2. The microbial amount calculation device according to claim 1, wherein the microbial amount calculation unit calculates the amount of microorganisms such that the amount of microorganisms increases as the amount of oxygen increases.

3. The methane fermentation tank is further equipped with a microbial quantity acquisition unit that acquires the amount of microorganisms remaining in the tank. The microbial amount calculation device according to claim 1 or 2, wherein the microbial amount calculation unit calculates the amount of microorganisms to be introduced into the methane fermentation tank based on the amount of oxygen and the amount of microorganisms remaining in the methane fermentation tank.

4. To obtain the amount of oxygen contained in the biomass that is introduced into the methane fermentation tank in a liquefied state, expressed as the mass of oxygen atoms, To obtain the molecular weight of substances contained in biomass, Based on the relationship between the amount of oxygen contained in the biomass, the molecular weight of the substances contained in the biomass, and the amount of microorganisms introduced into the methane fermentation tank, as predetermined in the map, the amount of microorganisms to be introduced into the methane fermentation tank for methane fermentation of the biomass is calculated according to the amount of oxygen obtained, and the amount of microorganisms to be introduced into the methane fermentation tank is calculated so that the more substances with high molecular weight are contained in the biomass, the greater the amount of microorganisms introduced into the methane fermentation tank. A method for calculating microbial mass, comprising the following features.

5. The method for calculating the amount of microorganisms according to claim 4, wherein the amount of microorganisms is calculated such that the amount of microorganisms increases as the amount of oxygen increases.

6. Furthermore, it is equipped to obtain the amount of microorganisms remaining in the methane fermentation tank. A method for calculating the amount of microorganisms to be introduced into a methane fermentation tank, according to claim 4 or 5, wherein the amount of microorganisms to be introduced into the methane fermentation tank is calculated based on the amount of oxygen and the amount of microorganisms remaining in the methane fermentation tank.

Images