Culture system and method for controlling culture system

Abstract

To provide a technology for appropriately supplying carbon dioxide to algae.SOLUTION: A culture system comprises: a circulation piping path which has, on the path, a bioreactor formed using a light-transmissive material capable of transmitting light and allows a liquid containing algae to circulate; a supply section for supplying a gas containing carbon dioxide into the circulation piping path such that a gas-liquid two-phase flow is formed at least in the bioreactor; a sensor section for measuring a state of the liquid flowing in the circulation piping path; and a control section for controlling supply of the gas in the supply section based on a measured value measured by the sensor section.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a culture system and a method for controlling a culture system. [Background technology]

[0002] Carbon dioxide (CO2) in the air is fixed in algae through photosynthesis by the algae. Patent Document 1 discloses a method and a bioreactor for culturing microorganisms. Patent Document 2 discloses a microalgae culture device for increasing the dissolution rate of carbon dioxide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5992451 [Patent Document 2] Patent No. 7102597 Summary of the Invention [Problem to be solved by the invention]

[0004] Bioreactors, such as algae culture devices, have been designed, manufactured, and operated primarily for the production and sale of relatively high-value products such as medicines, foods, and cosmetics. Bioreactors used in experimental and demonstration equipment for research and development have also been designed, manufactured, and operated for the production of fuels, plastics, and other products. Because stable cultivation is the primary goal in such bioreactors, an excess amount of carbon dioxide tends to be supplied to the algae compared to the amount required for algae growth. As a result, excessive amounts of unreacted carbon dioxide have been released into the atmosphere. When excessive amounts of carbon dioxide are supplied to the algae, the driving energy of pumps and other devices used to supply carbon dioxide is wasted. Therefore, despite the high energy consumption, excessive amounts of unreacted carbon dioxide are released into the atmosphere. Conventionally, carbon dioxide is supplied to algae for product manufacturing, etc., resulting in increased carbon dioxide supply and energy consumption. Furthermore, conventional methods for dissolving carbon dioxide sufficiently in the culture solution require highly compressed carbon dioxide using compressors or other devices, resulting in the breakup of bubbles and subsequent supply to the culture solution, which requires a significant amount of power energy. In order to fix carbon dioxide in the algae without excess or deficiency while reducing energy consumption, it is necessary to supply carbon dioxide to the algae appropriately.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique for appropriately supplying carbon dioxide to algae. [Means for solving the problem]

[0006] A culture system according to one aspect of the present invention comprises a circulation piping path having a bioreactor formed using a light-transmitting material on the path and through which a liquid containing algae circulates, a supply unit that supplies a gas containing carbon dioxide into the circulation piping path so as to form a two-phase gas-liquid flow at least in the bioreactor, a sensor unit that measures the state of the liquid flowing through the circulation piping path, and a control unit that controls the supply of the gas in the supply unit based on measurements measured by the sensor unit. According to the above culture system, the supply of gas in the supply unit that supplies a gas containing carbon dioxide into the circulation piping path so as to form a two-phase gas-liquid flow at least in the bioreactor is controlled based on measurements measured by the sensor unit that measures the state of the liquid flowing through the circulation piping path. This makes it possible to maintain a state in which the liquid flowing through the circulation piping path and the gas containing carbon dioxide are in contact not only near the supply unit but also along the entire length of the bioreactor. By maintaining this state, the carbon dioxide contained in the gas can be reduced. The carbon dioxide is gradually consumed throughout the entire length of the bioreactor, not just near the supply section, so that the carbon dioxide can be supplied appropriately to the algae. As a result, it is possible to fix just the right amount of carbon dioxide to the algae while reducing energy consumption in the culture system.

[0007] The sensor unit has an upstream sensor provided in the circulation piping path upstream of the gas supply position, and the upstream sensor measures the pH value of the liquid flowing through the circulation piping path, thereby making it possible to control the gas supply in the supply unit based on the pH value of the liquid measured by the upstream sensor.

[0008] The sensor unit has a downstream sensor provided downstream of the gas supply position in the circulation piping and an upstream sensor provided upstream of the gas supply position, and the downstream sensor and the upstream sensor measure the pH value of the liquid flowing through the circulation piping, thereby making it possible to control the gas supply in the supply unit based on the pH values ​​measured by the downstream sensor and the upstream sensor.

[0009] The sensor unit has a downstream sensor provided downstream of the gas supply position in the circulation piping and an upstream sensor provided upstream of the gas supply position, and the downstream sensor and the upstream sensor measure the amount of dissolved oxygen in the liquid flowing through the circulation piping. This makes it possible to control the supply of gas in the supply unit based on the amount of dissolved oxygen measured by the downstream sensor and the upstream sensor.

[0010] The sensor unit has a downstream sensor provided downstream of the gas supply position in the circulation piping, and a first upstream sensor and a second upstream sensor provided upstream of the gas supply position, the first upstream sensor measuring the pH value of the liquid flowing through the circulation piping, and the downstream sensor and the second upstream sensor measuring the amount of dissolved oxygen in the liquid flowing through the circulation piping. This makes it possible to control the supply of gas in the supply unit based on the pH value measured by the first upstream sensor and the amount of dissolved oxygen measured by the downstream sensor and the second upstream sensor.

[0011] The sensor unit includes a first downstream sensor and a second downstream sensor provided downstream of a gas supply position in the circulation piping, and a first upstream sensor and a second upstream sensor provided upstream of the gas supply position, the first downstream sensor and the first upstream sensor measuring a pH value of the liquid flowing through the circulation piping, and the second downstream sensor and the second upstream sensor measuring an amount of dissolved oxygen in the liquid flowing through the circulation piping. This makes it possible to control the supply of gas in the supply unit based on the pH value measured by the first downstream sensor and the first upstream sensor and the amount of dissolved oxygen measured by the second downstream sensor and the second upstream sensor.

[0012] The bioreactor is installed in a building. By installing a bioreactor in a building, the building can be used more effectively.

[0013] According to one aspect of the present invention, there is provided a control method for a culture system having a circulation piping path through which a liquid containing algae circulates, the circulation piping path having a bioreactor formed using a translucent material that can transmit light, the control method comprising: a supply step of supplying a gas containing carbon dioxide into the circulation piping path so as to form a gas-liquid two-phase flow in at least the bioreactor; a measurement step of measuring the state of the liquid flowing through the circulation piping path; and a control step of controlling the supply of the gas in the supply step based on the measurement value measured in the measurement step. [Effects of the Invention]

[0014] According to the present invention, carbon dioxide can be appropriately supplied to algae. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic configuration diagram of a culture system according to an embodiment. [Figure 2] FIG. 2 is a schematic configuration diagram of a culture system according to an embodiment. [Figure 3] FIG. 3 is a schematic configuration diagram of a culture system according to an embodiment. [Figure 4] FIG. 4 is a flowchart showing an example (first control) of the control unit. [Figure 5] FIG. 5 is a flowchart showing an example (second control) of the control unit. [Figure 6] FIG. 6 is a schematic configuration diagram of a culture system according to an embodiment. [Figure 7] FIG. 7 is a schematic configuration diagram of a culture system according to an embodiment. [Figure 8] FIG. 8 is a schematic diagram of a culture system according to the first modification. [Figure 9] FIG. 9 is a schematic configuration diagram of a culture system according to the second modification. [Figure 10]FIG. 10 is a schematic diagram of a culture system according to the third modification. [Figure 11] FIG. 11 is a schematic diagram of a culture system according to the fourth modification. [Figure 12] FIG. 12 is a schematic diagram of a culture system according to the fifth modification. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments will be described with reference to the drawings. The embodiment described below is one aspect of the present application and does not limit the scope of the present application.

[0017] First, we will explain conventional bioreactors. In order to fix carbon dioxide in the algae without excess or deficiency, it is necessary to constantly monitor the amount of carbon dioxide required by the algae in the bioreactor. In this case, the amount of carbon dioxide required fluctuates greatly because the photosynthetic activity of the algae varies depending on factors such as whether the algae in the bioreactor are healthy, whether there is sufficient light for photosynthesis, whether the water temperature is appropriate, and whether there is sufficient nutrition. If too much carbon dioxide is supplied to the bioreactor, excessive unreacted carbon dioxide will be released into the atmosphere. On the other hand, if too little carbon dioxide is supplied to the bioreactor, it may cause serious damage to the algae culture.

[0018] However, it is not easy to grasp the amount of carbon dioxide required by algae in a bioreactor in real time for the following reasons:

[0019] (Reason 1) One method involves measuring the carbon dioxide concentration at the outlet and the carbon dioxide concentration at the inlet, and determining the carbon dioxide surplus or deficiency based on the difference between the two. The carbon dioxide concentration at the outlet is the concentration of carbon dioxide contained in the gas released from the tank into the atmosphere. The carbon dioxide concentration at the inlet is the concentration of carbon dioxide contained in the gas supplied to the liquid in the tank. Generally, there is a significant time lag of several hours between the time when the carbon dioxide-containing gas is supplied to the liquid in the tank and the time when a change in the carbon dioxide concentration at the outlet appears. This is due to many factors, but generally includes (A) the large capacity of the bioreactor itself, (B) the fact that the photochemical reaction at the beginning of the photosynthetic reaction is instantaneous, while the Calvin cycle at the end is a relatively slow reaction, and (C) even if the same amount of carbon dioxide is present in the water, the amount of carbon dioxide released as a gas varies depending on the water's pH, alkalinity, water temperature, etc. Therefore, this method cannot achieve the appropriate amount of carbon dioxide to be added in real time.

[0020] (Reason 2) When measuring the amount of carbon dioxide dissolved in water to determine whether there is an excess or deficiency of carbon dioxide, the carbon dioxide dissolved in water is not only CO2 but also HCO3 - and CO3 2- Therefore, it is not possible to grasp the actual amount of dissolved carbon dioxide unless the total amount of carbon dioxide that covers all of these is measured. However, measuring the total amount of carbon dioxide in real time is It is said that the measurement principle is difficult, and therefore this method cannot realize the proper amount of carbon dioxide injection in real time.

[0021] (Reason 3) Even if you measure the pH of water to determine whether there is an excess or deficiency of carbon dioxide, you cannot determine the total amount of dissolved carbon unless you also measure the alkalinity of the water. However, it is said that measuring the alkalinity of water in real time is difficult in principle. Therefore, this method cannot realize the appropriate amount of carbon dioxide injection in real time.

[0022] FIG. 1 is a schematic diagram of a culture system 1 according to an embodiment. The culture system 1 has a bioreactor 2 on the path and a circulation piping path 3 through which a liquid containing algae (circulating liquid) circulates. The bioreactor 2 is made of a translucent material that can transmit light. The light irradiated onto the bioreactor 2 may be sunlight or light emitted from a light source such as an LED (Light Emitting Diode). The bioreactor 2 is made of a continuous, sealed tube. Therefore, the liquid flowing inside the bioreactor 2 is not exposed to the outside air. Furthermore, the parts of the circulation piping path 3 other than the bioreactor 2 also have a sealed structure, and the liquid circulating through the circulation piping path 3 is not exposed to the outside air.

[0023] A tank 10 and a pump 11 are provided in the circulation piping path 3. The tank 10 temporarily stores the liquid delivered from the bioreactor 2. The pump 11 is a device for delivering the liquid in the tank 10 into the bioreactor 2, and is located downstream of the tank 10. The circulation piping path 3 is provided with a downstream sensor unit (inlet sensor unit) 12 and an upstream sensor unit (outlet sensor unit) 13 that measure the state of the liquid flowing through the circulation piping path 3. The downstream sensor unit 12 and the upstream sensor unit 13 may be integrated.

[0024] The culture system 1 includes a supply unit 20. The supply unit 20 supplies a gas containing carbon dioxide into the circulation piping path 3 so as to form a gas-liquid two-phase flow at least in the bioreactor 2. The supply unit 20 may supply the gas into the circulation piping path 3 using gas stored in the culture system 1. The supply unit 20 may be, for example, a blower or a compressor. The supply unit 20 may supply the gas into the circulation piping path 3 using gas provided from outside the culture system 1. The culture system 1 includes a control unit 21. Measured values ​​measured by the upstream sensor unit 13 and measured values ​​measured by the downstream sensor unit 12 are sent to the control unit 21. The control unit 21 controls the supply of gas in the supply unit 20 based on the measured values. The supply of gas in the supply unit 20 is controlled using an electric valve, a solenoid valve, or the like. The control unit 21 is a controller that controls the entire culture system 1, and is, for example, a programmable logic controller (PLC).

[0025] The downstream sensor unit 12 has a first downstream sensor (first inlet sensor) 14 and a second downstream sensor (second inlet sensor) 15. The first downstream sensor 14 and the second downstream sensor 15 are provided at positions downstream of the gas supply position A1 in the circulation piping path 3. The first downstream sensor 14 and the second downstream sensor 15 are provided in the circulation piping path 3 so that their respective sensing portions come into contact with the liquid flowing through the circulation piping path 3. A small tank may be provided in the circulation piping path 3, and the first downstream sensor 14 and the second downstream sensor 15 may be disposed in the small tank. The positions of the first downstream sensor 14 and the second downstream sensor 15 may be reversed.

[0026] The upstream sensor unit 13 has a first upstream sensor (first outlet sensor) 16 and a second upstream sensor (second outlet sensor) 17. The first upstream sensor 16 and the second upstream sensor 17 are provided at positions upstream of the gas supply position A1 in the circulation piping path 3. The sensing portions of the first upstream sensor 16 and the second upstream sensor 17 are arranged to detect the gas flowing through the circulation piping path 3. A first upstream sensor 16 and a second upstream sensor 17 are provided in the circulation piping path 3 so as to come into contact with the liquid flowing through the piping path 3. A small tank may be provided in the circulation piping path 3, and the first upstream sensor 16 and the second upstream sensor 17 may be disposed in the small tank. The positions of the first upstream sensor 16 and the second upstream sensor 17 may be reversed. The term "upstream" refers to the upstream side in the direction of fluid (gas and liquid) flow in the circulation piping path 3. The term "downstream" refers to the downstream side in the direction of fluid flow in the circulation piping path 3. Although the upstream and downstream sides have been described above with reference to the supply position A1, this is not limiting. For example, the upstream side may be the side where a fluid flows from the tank 10 toward the bioreactor 2 and enters the bioreactor 2, or the downstream side may be the side where a fluid flows from the bioreactor 2 toward the tank 10 and returns to the tank 10.

[0027] The first downstream sensor 14 and the first upstream sensor 16 measure the pH of the liquid flowing through the circulation piping path 3. The measured values ​​measured by the first downstream sensor 14 and the first upstream sensor 16 are sent to the control unit 21. The second downstream sensor 15 and the second upstream sensor 17 measure the amount of dissolved oxygen in the liquid flowing through the circulation piping path 3. The measured values ​​measured by the second downstream sensor 15 and the second upstream sensor 17 are sent to the control unit 21.

[0028] The circulation piping path 3 is provided with a pipe 22 for supplying gas into the circulation piping path 3. The tank 10 is provided with a pipe 23 for releasing the gas in the tank 10 into the atmosphere. A sensor 24 is provided in the pipe 22, and a sensor 25 is provided in the pipe 23. The sensor 24 measures the concentration of carbon dioxide contained in the gas flowing through the pipe 22. Specifically, the sensor 24 measures the concentration of carbon dioxide supplied to the circulation piping path 3. The sensor 25 measures the concentration of carbon dioxide contained in the gas flowing through the pipe 23. Specifically, the sensor 25 measures the concentration of carbon dioxide contained in the gas released from the circulation piping path 3 to the atmosphere.

[0029] FIG. 2 is a schematic diagram of a culture system 1 according to an embodiment. The configuration of the culture system 1 in FIG. 2 may be adopted. In FIG. 2, a first upstream sensor 16 is provided in the tank 10 and measures the pH of the liquid flowing through the circulation piping path 3. Also, in FIG. 2, a second upstream sensor 17 is provided in the tank 10 and measures the amount of dissolved oxygen in the liquid flowing through the circulation piping path 3. FIG. 3 is a schematic diagram of a culture system 1 according to an embodiment. The configuration of the culture system 1 in FIG. 3 may be adopted. The tank 10 shown in FIG. 3 also serves as an expansion tank.

[0030] The first control of the control unit 21 will be described. The control unit 21 may acquire a measurement value (hereinafter referred to as a first pH value) measured by the downstream first sensor 14 and a measurement value (hereinafter referred to as a second pH value) measured by the upstream first sensor 16. The control unit 21 may control the supply of gas in the supply unit 20 based on the first pH value and the second pH value.

[0031] The control unit 21 may control the supply of gas in the supply unit 20 based on the second pH value. For example, if the second pH value deviates from the expected pH range, the control unit 21 changes the set value set in the supply unit 20. An expected pH range suitable for the type of algae is determined in advance and stored in the memory unit of the control unit 21. The expected pH range is, for example, pH = 6 to 8, but is not limited to this range. The control unit 21 may change the set value of the supply unit 20 to change the supply amount of carbon dioxide supplied from the supply unit 20 to the circulation piping path 3. The control unit 21 may change the set value of the supply unit 20 to change the concentration of carbon dioxide contained in the gas supplied from the supply unit 20 to the circulation piping path 3.

[0032] For example, if the second pH value is larger than the expected range (if the pH exceeds 8), it can be determined that there is a tendency for carbon dioxide to be insufficient. The amount of carbon dioxide supplied may be increased, or the concentration of carbon dioxide contained in the gas supplied from the supply unit 20 to the circulation piping path 3 may be increased. For example, if the second pH value becomes smaller than the expected range (if the pH is below 6), it can be determined that there is an excess of carbon dioxide. In this case, the amount of carbon dioxide supplied from the supply unit 20 to the circulation piping path 3 may be decreased, or the concentration of carbon dioxide contained in the gas supplied from the supply unit 20 to the circulation piping path 3 may be reduced. However, if the difference between the first pH value and the second pH value is not large, these operations are not performed because the pH fluctuation is not related to photosynthesis.

[0033] Fig. 4 is a flowchart showing an example (first control) of the control unit 21. The control of the control unit 21 will be described with reference to Fig. 4. After the supply of gas from the supply unit 20 to the circulation piping path 3 starts, the control flow shown in Fig. 4 is executed.

[0034] In step S101, the control unit 21 acquires a first pH value and a second pH value. In step S102, the control unit 21 compares the first pH value with the second pH value and determines whether the difference between the first pH value and the second pH value is within a predetermined range. If the difference between the first pH value and the second pH value is not within the predetermined range (step S102: NO), the process proceeds to step S103. If the difference between the first pH value and the second pH value is within the predetermined range (step S102: YES), the process proceeds to step S106.

[0035] In step S103, the control unit 21 compares the second pH value with a threshold value. If the second pH value is equal to or less than the first threshold value (lower limit value), the process proceeds to step S104. If the second pH value is equal to or greater than the second threshold value (upper limit value), the process proceeds to step S105. If the second pH value is greater than the first threshold value (lower limit value) and less than the second threshold value (upper limit value), the process proceeds to step S106.

[0036] In step S104, the control unit 21 controls the supply of the gas containing carbon dioxide in the supply unit 20 so as to reduce the amount of carbon dioxide supplied from the supply unit 20 to the circulation piping path 3. Alternatively, the control unit 21 may control the supply of the gas containing carbon dioxide in the supply unit 20 so as to reduce the concentration of carbon dioxide contained in the gas supplied from the supply unit 20 to the circulation piping path 3.

[0037] In step S105, the control unit 21 controls the supply of the gas containing carbon dioxide in the supply unit 20 so as to increase the amount of carbon dioxide supplied from the supply unit 20 to the circulation piping path 3. Alternatively, the control unit 21 may control the supply of the gas containing carbon dioxide in the supply unit 20 so as to increase the concentration of carbon dioxide contained in the gas supplied from the supply unit 20 to the circulation piping path 3.

[0038] In step S106, the control unit 21 controls the supply of the gas containing carbon dioxide in the supply unit 20 so as to maintain the supply amount of carbon dioxide supplied from the supply unit 20 to the circulation piping path 3. Alternatively, the control unit 21 may control the supply of the gas containing carbon dioxide in the supply unit 20 so as to maintain the concentration of carbon dioxide contained in the gas supplied from the supply unit 20 to the circulation piping path 3.

[0039] The control flow shown in Fig. 4 is continuously performed at predetermined intervals. That is, after the control flow shown in Fig. 4 ends, the control flow shown in Fig. 4 starts after a predetermined time has elapsed.

[0040] The second control of the control unit 21 will be described. The control unit 21 may acquire a measurement value (hereinafter referred to as a first dissolved oxygen amount) measured by the downstream second sensor 15 and a measurement value (hereinafter referred to as a second dissolved oxygen amount) measured by the upstream second sensor 17. The control unit 21 determines the amount of dissolved oxygen in the supply unit 20 based on the first dissolved oxygen amount and the second dissolved oxygen amount. The supply of gas may be controlled.

[0041] The control unit 21 measures in real time the saturated dissolved oxygen amount (mg / L) for each of the first dissolved oxygen amount (mg / L) and the second dissolved oxygen amount (mg / L) relative to the water temperature at the time of measurement. The control unit 21 calculates and compares the first dissolved oxygen saturation rate (=first dissolved oxygen amount / first saturated dissolved oxygen amount) and the second dissolved oxygen saturation rate (=second dissolved oxygen amount / second saturated dissolved oxygen amount). The first saturated dissolved oxygen amount is the saturated dissolved oxygen amount relative to the water temperature at the time the first dissolved oxygen amount is measured. The second saturated dissolved oxygen amount is the saturated dissolved oxygen amount relative to the water temperature at the time the second dissolved oxygen amount is measured.

[0042] When the photosynthetic activity of the algae in the bioreactor 2 is high, the second dissolved oxygen saturation rate will be higher than the first dissolved oxygen saturation rate. On the other hand, when the photosynthetic activity of the algae in the bioreactor 2 is low, the second dissolved oxygen saturation rate will be the same as or lower than the first dissolved oxygen saturation rate. Therefore, the ratio of the second dissolved oxygen saturation rate to the first dissolved oxygen saturation rate (hereinafter referred to as the dissolved oxygen change rate) serves as an index for determining the photosynthetic activity of the algae in the bioreactor 2 in real time. Note that the dissolved oxygen change rate is not determined using an instantaneous value, but rather, for example, using a moving average value over a period of about 5 to 60 minutes. For example, when the dissolved oxygen change rate is equal to or higher than a predetermined value, the control unit 21 changes the set value set in the supply unit 20. The control unit 21 may increase the amount of carbon dioxide supplied from the supply unit 20 to the circulation piping path 3 by changing the set value of the supply unit 20. The control unit 21 may increase the concentration of carbon dioxide contained in the gas supplied from the supply unit 20 to the circulation piping path 3 by changing the setting value of the supply unit 20 .

[0043] Fig. 5 is a flowchart showing an example (second control) of the control unit 21. The control of the control unit 21 will be described with reference to Fig. 5. After the supply of gas from the supply unit 20 to the circulation piping path 3 starts, the control flow shown in Fig. 5 is executed. The control flow shown in Fig. 5 is executed continuously at predetermined intervals.

[0044] In step S201, the control unit 21 acquires the first dissolved oxygen amount and the second dissolved oxygen amount. In step S202, the control unit 21 calculates a first dissolved oxygen saturation rate based on the first dissolved oxygen amount and the first saturated dissolved oxygen amount, and calculates a second dissolved oxygen saturation rate based on the second dissolved oxygen amount and the second saturated dissolved oxygen amount.

[0045] In step S203, the control unit 21 calculates the dissolved oxygen change rate based on the first dissolved oxygen saturation rate and the second dissolved oxygen saturation rate, and in step S204, the control unit 21 determines whether the dissolved oxygen change rate is less than a predetermined value.

[0046] If the dissolved oxygen change rate is less than the predetermined value (step S204: YES), the process proceeds to step S205. If the dissolved oxygen change rate is not less than the predetermined value (step S204: NO), the process proceeds to step S206.

[0047] In step S205, the control unit 21 controls the supply of the gas containing carbon dioxide in the supply unit 20 so as to maintain the supply amount of carbon dioxide supplied from the supply unit 20 to the circulation piping path 3. Alternatively, in step S205, the control unit 21 may control the supply of the gas containing carbon dioxide in the supply unit 20 so as to maintain the concentration of carbon dioxide contained in the gas supplied from the supply unit 20 to the circulation piping path 3.

[0048] In step S205, the control unit 21 controls the supply unit 20 to supply the carbon dioxide-containing gas so that the amount of carbon dioxide supplied from the supply unit 20 to the circulation piping path 3 decreases. Alternatively, in step S205, control unit 21 may control the supply of the gas containing carbon dioxide in supply unit 20 so that the concentration of carbon dioxide contained in the gas supplied from supply unit 20 to circulation piping path 3 is reduced.

[0049] In step S206, the control unit 21 controls the supply of the gas containing carbon dioxide in the supply unit 20 so as to increase the amount of carbon dioxide supplied from the supply unit 20 to the circulation piping path 3. Alternatively, the control unit 21 may control the supply of the gas containing carbon dioxide in the supply unit 20 so as to increase the concentration of carbon dioxide contained in the gas supplied from the supply unit 20 to the circulation piping path 3.

[0050] Furthermore, before the processing of step S204 is performed, the control unit 21 may determine whether or not the state in which the rate of change in dissolved oxygen is less than a predetermined value has continued for a predetermined time. If the state in which the rate of change in dissolved oxygen is less than the predetermined value has continued for the predetermined time, the control unit 21 returns the setting value of the supply unit 20 to the initial value. Thereafter, the control flow shown in Fig. 5 ends. If the state in which the rate of change in dissolved oxygen is less than the predetermined value has not continued for the predetermined time, the control unit 21 performs the processing of step S204.

[0051] The control flow shown in Fig. 5 is continuously performed at predetermined intervals. That is, after the control flow shown in Fig. 5 ends, the control flow shown in Fig. 5 starts after a predetermined time has elapsed.

[0052] The third control of the control unit 21 will now be described. The third control of the control unit 21 is continuously performed at predetermined intervals. The control unit 21 may acquire a measurement value measured by the sensor 24 (hereinafter referred to as the first carbon dioxide concentration) and a measurement value measured by the sensor 25 (hereinafter referred to as the second carbon dioxide concentration). The control unit 21 may calculate the difference between the second carbon dioxide concentration and the first carbon dioxide concentration by subtracting the first carbon dioxide concentration from the second carbon dioxide concentration. The difference between the first carbon dioxide concentration and the second carbon dioxide concentration (second carbon dioxide concentration - first carbon dioxide concentration) can be used as an index for understanding the activity of photosynthesis.

[0053] When the photosynthetic activity of the algae in the bioreactor 2 is high, the difference between the first carbon dioxide concentration and the second carbon dioxide concentration will be a positive value. When the photosynthetic activity of the algae in the bioreactor 2 is low, the difference between the first carbon dioxide concentration and the second carbon dioxide concentration will be a negative value. However, since it takes several hours for the difference between the first carbon dioxide concentration and the second carbon dioxide concentration to appear, the difference between the first carbon dioxide concentration and the second carbon dioxide concentration is used as a reference value. Specifically, the difference between the first carbon dioxide concentration and the second carbon dioxide concentration is used as information for reinforcing the first control and second control of the control unit 21 and for identifying abnormalities in the growth state (such as weakening of the algae). Note that the difference between the first carbon dioxide concentration and the second carbon dioxide concentration is not determined using an instantaneous value, but rather using a moving average value over, for example, about 5 to 60 minutes.

[0054] When the difference between the first carbon dioxide concentration and the second carbon dioxide concentration is a positive value, the control unit 21 outputs a result indicating that the operating method of the culture system 1 is in a normal state. When the difference between the first carbon dioxide concentration and the second carbon dioxide concentration is a negative value, the control unit 21 outputs a result indicating that the operating method of the culture system 1 is in a caution state. When the difference between the first carbon dioxide concentration and the second carbon dioxide concentration remains a negative value for a predetermined time, the control unit 21 outputs a result indicating that the operating method of the culture system 1 is in a warning state. The result output by the control unit 21 may include information indicating the state of the operating method of the culture system 1, as well as information prompting a change in the operating method of the culture system 1. The result output by the control unit 21 may be displayed on a display unit provided in the culture system 1. The result output by the control unit 21 may be sent to an information processing device of the administrator of the culture system 1. The information processing device is, for example, a personal computer, a smartphone, a tablet terminal, or the like.

[0055] The first to third controls of the control unit 21 may be combined as much as possible. The control unit 21 may perform the first to third controls in parallel, or may perform the first to third controls sequentially. The control unit 21 may perform each process of the control flow shown in FIG. 5 after the control flow shown in FIG. 4 is completed. For example, when the supply amount of carbon dioxide is increased by performing the process of step S105 of the control flow shown in FIG. 4, the supply amount of carbon dioxide may be further increased by performing the process of step S206 of the control flow shown in FIG. 5. For example, when the supply amount of carbon dioxide is increased by performing the process of step S105 of the control flow shown in FIG. 4, the supply amount of carbon dioxide may be decreased, or the increase in the supply of carbon dioxide may be reduced, by performing the process of step S205 of the control flow shown in FIG. 5.

[0056] Next, a method for supplying (introducing) carbon dioxide or a gas containing carbon dioxide to the circulating liquid in the bioreactor 2 will be described. When supplying the gas containing carbon dioxide to the circulation piping path 3, it is not necessary to break down the bubbles. The gas containing carbon dioxide is supplied into the circulation piping path 3 so as to form a gas-liquid two-phase flow in the bioreactor 2. Therefore, there is no need to compress the gas to a high pressure, and the power energy required for the pump or compressor is small. In this case, the reason why the carbon dioxide or the gas containing carbon dioxide in the bioreactor 2 can be a gas-liquid two-phase flow is as follows. The concentration of dissolved carbon dioxide in the liquid (culture solution) in the sealed tube of the bioreactor 2 should naturally decrease gradually due to photosynthesis along with the flow of the liquid. However, due to the action of maintaining the gas-liquid equilibrium state of carbon dioxide, the carbon dioxide in the gas side of the gas-liquid two-phase flow moves (dissolves) to the liquid side. Therefore, in the gas-liquid two-phase flow in the bioreactor 2, the carbon dioxide in the liquid side required for photosynthesis is supplied as needed from the gas side.

[0057] According to the culture system 1 of this embodiment, the supply of gas in the supply unit 20, which supplies a gas containing carbon dioxide into the circulation piping 3, is controlled based on measurements of the state of the liquid flowing through the circulation piping 3 so as to create a gas-liquid two-phase flow at least in the bioreactor 2. This allows the liquid flowing through the circulation piping 3 to be kept in contact with the gas containing carbon dioxide not only near the supply unit 20 but also along the entire length of the bioreactor 2. By maintaining this state, the carbon dioxide contained in the gas is gradually consumed not only near the supply unit 20 but also along the entire length of the bioreactor 2, allowing for an appropriate supply of carbon dioxide to the algae. As a result, an adequate supply of carbon dioxide to the bioreactor 2 can be achieved, enabling highly efficient operation control of the bioreactor 2. In other words, it is possible to reduce energy consumption in the culture system 1 while immobilizing an adequate amount of carbon dioxide in the algae.

[0058] In the culture system 1 according to the embodiment, the installation of the downstream first sensor 14 may be omitted. In this case, the control unit 21 may control the supply of gas in the supply unit 20 based on the second pH value. In the control flow shown in Fig. 4, in step S101, the control unit 21 acquires the second pH value, the process of step S102 is omitted, and the process of step S103 is performed. In the culture system 1 according to the embodiment, the installation of the sensors 24 and 25 may be omitted.

[0059] FIG. 6 is a schematic diagram of the culture system 1 according to the embodiment. The structure of the culture system 1 in FIG. 6 may be adopted. In FIG. 6, the pump 11 is installed in the upper part of the culture system 1. As shown in FIG. 6, by installing the pump 11 relatively higher in the culture system 1, the pressure corresponding to the actual head can be reduced, and power energy can be reduced. In addition, for example, Using an injector or similar device will further reduce power energy consumption.

[0060] FIG. 7 is a schematic diagram of a culture system 1 according to an embodiment. The configuration of the culture system 1 in FIG. 7 may be adopted. In FIG. 7, the pump 11 is installed in the upper part of the culture system 1. As shown in FIG. 7, by installing the pump 11 relatively higher in the culture system 1, the pressure equivalent to the actual head can be reduced, thereby reducing power energy. Furthermore, for example, by utilizing an ejector or the like, power energy can be further reduced. In FIG. 7, the pump 11 is installed so that a gas containing carbon dioxide is supplied to the suction side of the pump 11. In the configuration example shown in FIG. 7, the pump 11 needs to be operated in a gas-liquid two-phase state, which reduces the operating efficiency of the pump 11, but reduces the supply pressure required when supplying gas to the circulation piping path 3.

[0061] FIG. 8 is a schematic diagram of a culture system 1 according to Modification 1. The configuration of the culture system 1 in FIG. 8 may be adopted. In FIG. 8, the bioreactor 2 has a plurality of water tanks 30 and a plurality of control valves 31. The water tanks 30 are formed using a light-transmitting material. In the culture system 1 shown in FIG. 8, the piping resistance is not uniform, so the flow rates of gas and liquid flowing through the plurality of water tanks 30 are controlled by the plurality of control valves 31. In FIG. 8, the bioreactor 2 has a plurality of water tanks 30, but is not limited thereto, and a tank, container, or the like having a light-transmitting window may be used instead of the water tanks 30.

[0062] FIG. 9 is a schematic diagram of a culture system 1 according to Modification 2. The configuration of the culture system 1 in FIG. 9 may be adopted. In FIG. 9, the bioreactor 2 has multiple water tanks 30. The bioreactor 2 is formed using a light-transmitting material that allows light to pass through. In the culture system 1 shown in FIG. 9, the piping resistance is uniform, so the installation of multiple control valves 31 is omitted compared to the culture system 1 shown in FIG. 8. In FIG. 9, the bioreactor 2 has multiple water tanks 30, but this is not limited thereto, and a tank, container, or the like having a light-transmitting window may be used instead of the water tanks 30.

[0063] FIG. 10 is a schematic configuration diagram of a culture system 1 according to Modification 3. The configuration of the culture system 1 in FIG. 10 may be adopted. In FIG. 10, a gas containing carbon dioxide is provided to the supply unit 20 from an exhaust gas treatment device 40. The exhaust gas treatment device 40 may be disposed inside the culture system 1 or may be disposed outside the culture system 1. The exhaust gas treatment device 40 treats exhaust gas from a factory or the like and provides the gas containing carbon dioxide to the supply unit 20. By combining the culture system 1 with a recovery system that uses the exhaust gas treatment device 40, it is possible to efficiently recover and utilize carbon dioxide.

[0064] FIG. 11 is a schematic diagram of a culture system 1 according to Modification 4. The configuration of the culture system 1 in FIG. 11 may be adopted. In FIG. 11, a gas containing carbon dioxide is provided to the supply unit 20 from a DAC (Direct Air Capture) system 50. The DAC system 50 may be disposed inside the culture system 1 or may be disposed outside the culture system 1. The DAC system 50 is a device that separates and captures carbon dioxide from the atmosphere. The DAC system 50 separates and captures carbon dioxide from the atmosphere and provides the gas containing carbon dioxide to the supply unit 20. By combining the culture system 1 with a capture system that uses the DAC system 50, it is possible to efficiently capture and utilize carbon dioxide.

[0065] FIG. 12 is a schematic diagram of the culture system 1 according to Modification 5. The configuration of the culture system 1 in FIG. 12 may be adopted. In FIG. 12, the bioreactor 2 having a planar extension is installed so as to be approximately parallel to the wall (side surface) of the building 60. In this figure, the bioreactor 2 is installed on the wall (side surface) of the building 60, but this is not limitative, and it may also be installed on the roof (top surface) of the building 60. In other words, it may be installed so as to be approximately parallel to the planar portion of the building 60 or at a predetermined incline. The bioreactor 2 may be installed in multiple planar portions of the building 60. By installing the bioreactor 2 in a portion of the building 60, carbon dioxide generated inside the building 60 due to human activity or the like can be supplied to the bioreactor 2. In such a case, a DAC system 50 may be installed between the building 60 and the supply unit 20 of the bioreactor 2 to recover carbon dioxide from the return air of an air conditioning system that conditions rooms in the building 60 or from the air in the ventilation channel. Carbon dioxide may also be supplied from a supply source such as a factory located near or far from the building 60. When the concentration of carbon dioxide supplied from a factory or the like is high, it may be supplied directly to the supply unit 20 without installing a DAC system 50. Furthermore, installing the bioreactor 2 in a portion of the building 60 can insulate the building 60. In such a case, installing insulation or a heat-shielding material between the bioreactor 2 and the building 60 can provide additional benefits. Furthermore, installing the bioreactor 2 also serves an artistic or decorative function. In this modified example, the bioreactor 2 is described as being installed next to a wall or roof, but it may also be installed as part of the wall or roof by being placed within the framework or framework of the wall or roof and covered with a transparent cover.

[0066] The present invention can also be understood as a control method including at least a part of the above processing, a program for causing a computer to execute at least a part of the above processing, or a computer-readable recording medium on which such a program is non-temporarily recorded. The above configurations and processing can be combined to constitute the present invention as long as no technical contradiction occurs. [Explanation of symbols]

[0067] 1: Culture system 2: Bioreactor 3: Circulation piping route 10: Tank 11: Pump 12: Downstream sensor section 13: Upstream sensor section 14: Downstream first sensor 15: Second downstream sensor 16: First upstream sensor 17: Second upstream sensor 20: Supply section 21: Control unit 22, 23: Piping 24, 25: Sensor

Claims

1. a circulation piping path through which a liquid containing algae circulates, the circulation piping path having a bioreactor formed using a light-transmitting material on the path; a supply unit that supplies a gas containing carbon dioxide into the circulation piping path so as to form a gas-liquid two-phase flow at least in the bioreactor; a sensor unit for measuring a state of the liquid flowing through the circulation piping; a control unit that controls the supply of the gas in the supply unit based on a measurement value measured by the sensor unit; A culture system comprising:

2. the sensor unit has an upstream sensor provided at a position upstream of a supply position of the gas in the circulation piping path, The upstream sensor measures the pH value of the liquid flowing through the circulation piping path. The culture system according to claim 1 .

3. the sensor unit includes a downstream sensor provided at a position downstream of a supply position of the gas in the circulation piping path, and an upstream sensor provided at a position upstream of the supply position, the downstream sensor and the upstream sensor measure the pH value of the liquid flowing through the circulation piping path. The culture system according to claim 1 .

4. the sensor unit includes a downstream sensor provided at a position downstream of a supply position of the gas in the circulation piping path, and an upstream sensor provided at a position upstream of the supply position, the downstream sensor and the upstream sensor measure the amount of dissolved oxygen in the liquid flowing through the circulation piping path. The culture system according to claim 1 .

5. the sensor unit includes a downstream sensor provided at a position downstream of a supply position of the gas in the circulation piping path, and a first upstream sensor and a second upstream sensor provided at positions upstream of the supply position, the upstream first sensor measures a pH value of the liquid flowing through the circulation piping path; the downstream sensor and the second upstream sensor measure the amount of dissolved oxygen in the liquid flowing through the circulation piping path. The culture system according to claim 1 .

6. the sensor unit includes a first downstream sensor and a second downstream sensor provided at a position downstream of a supply position of the gas in the circulation piping path, and a first upstream sensor and a second upstream sensor provided at a position upstream of the supply position, the downstream first sensor and the upstream first sensor measure a pH value of the liquid flowing through the circulation piping path; the downstream second sensor and the upstream second sensor measure the amount of dissolved oxygen in the liquid flowing through the circulation piping path. The culture system according to claim 1 .

7. The bioreactor is provided in a building, A culture system according to any one of claims 1 to 6.

8. A control method for a culture system having a circulation piping path through which a liquid containing algae circulates, the circulation piping path having a bioreactor formed using a light-transmitting material on the path, the method comprising: A supply step of supplying a gas containing carbon dioxide into the circulation piping path so as to form a gas-liquid two-phase flow at least in the bioreactor; a measuring step of measuring a state of the liquid flowing through the circulation piping path; a control step of controlling the supply of the gas in the supply step based on the measurement value obtained in the measurement step; A method for controlling a culture system comprising:

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