Cultivation method and culture device

Abstract

A culture device (10) comprises: a gas supply unit (16); and a plurality of containers (12a-12c). The gas supply unit is connected with the plurality of containers through a plurality of gas supply lines (20, 22a, 22b), respectively. The plurality of gas supply lines are provided with a plurality of valves (24a-24c), respectively. While microalgae are cultured in the plurality of containers, the opening degrees of the plurality of valves are adjusted. By such adjustment of the opening degrees, a greater amount of gas is supplied to one (12a) of the plurality of containers than those of the other containers (12b, 12c).

Description

[Technical Field]

[0001] The present invention relates to a culture method and a culture device for culturing microalgae in a culture solution. [Background technology]

[0002] Efforts aimed at mitigating or reducing the impact of climate change have been ongoing, and research and development into reducing carbon dioxide emissions has been conducted to achieve this. From this perspective, microalgae have attracted attention because they consume carbon dioxide through photosynthesis. Therefore, microalgae culture devices are expected to contribute to mitigating or reducing the impact of climate change.

[0003] The culture solution and microalgae are contained in a storage unit. A culture gas is supplied to the storage unit in an amount sufficient for the microalgae to perform photosynthesis. The culture solution and microalgae are diffused to some extent by the culture gas, but the microalgae settle in the culture solution. When the microalgae settle, the amount of light received by the microalgae decreases. As a result, photosynthesis becomes insufficient. From this perspective, in the prior art described in JP 2018-537948 A, a precipitation prevention gas is intermittently supplied to the culture solution in the storage unit. In this prior art, the precipitation prevention gas is supplied to the culture solution once every 30 minutes to levitate the microalgae that settle in the culture solution. Summary of the Invention

[0004] It is expected that microalgae will be cultured simultaneously in multiple storage units, and in this case, a large amount of microalgae can be cultured, which is expected to result in a large amount of carbon dioxide being consumed.

[0005] In this case, precipitation prevention gas is supplied to multiple storage units. In this configuration, when precipitation prevention gas is supplied to all storage units simultaneously, the valves provided in each of the multiple storage units open simultaneously, as shown in Figure 4, and a large amount of precipitation prevention gas is temporarily supplied from the gas supply unit. For this reason, even though the precipitation prevention gas is supplied intermittently, the gas supply unit must have the capacity to simultaneously supply a large amount of precipitation prevention gas.

[0006] A gas supply unit with such a capacity consumes a large amount of power per unit time, making it difficult to reduce the running costs of the culture.

[0007] The present invention aims to solve the above-mentioned problems.

[0008] According to one embodiment of the present invention, there is provided a culture method for culturing microalgae in a culture device comprising a plurality of storage sections for storing culture solution and microalgae, a gas supply section for supplying gas to the plurality of storage sections, and a plurality of gas supply lines respectively connecting the gas supply section and the plurality of storage sections, the culture method comprising: an opening adjustment process for adjusting the opening of at least one of the plurality of valves while culturing the microalgae in the plurality of storage sections; and an agitation process for culturing the microalgae with the opening of at least one of the plurality of valves adjusted, wherein in the opening adjustment process, the opening of at least one of the plurality of valves is adjusted to stop the supply of the gas to at least one of the plurality of storage sections or reduce the supply flow rate, and increase the supply flow rate of the gas to at least one remaining storage section.

[0009] According to another embodiment of the present invention, there is provided a culture apparatus for culturing microalgae in a culture solution, comprising: a plurality of storage units for storing the culture solution and the microalgae; a gas supply unit for supplying gas to the plurality of storage units; a plurality of gas supply lines connecting the gas supply unit to the plurality of storage units; a plurality of valves provided on the plurality of gas supply lines; and a control unit for individually adjusting the opening degrees of the plurality of valves, wherein the control unit adjusts the opening degree of at least one of the plurality of valves while culturing the microalgae in the plurality of storage units, thereby stopping the supply of the gas to at least one of the plurality of storage units or reducing the supply flow rate, and increasing the supply flow rate of the gas to at least one remaining storage unit.

[0010] By adjusting the opening degree, the gas supply is stopped or the supply flow rate is reduced in at least one of the multiple storage sections, while the gas supply flow rate is increased in at least one remaining storage section. In other words, the gas supply flow rate is adjusted.

[0011] Therefore, even if the gas supply flow rate from the gas supply unit is constant, a large amount of gas can be temporarily supplied to at least one of the multiple storage units. Therefore, it is not necessary to select a gas supply unit with excess capacity. Here, excess capacity means the capacity to simultaneously supply gas for stirring to the multiple storage units in addition to the gas supplied in the general process.

[0012] That is, according to the present invention, it is possible to use a gas supply unit that has an appropriate capacity and consumes less power per unit time, thereby reducing the running costs of the culture.

[0013] In the storage section where the gas supply flow rate is temporarily increased, the microalgae and culture solution are agitated. This prevents the microalgae from settling or flocculating. This allows light to be incident on the microalgae approximately evenly. Furthermore, as the culture solution is agitated, carbon dioxide is diffused throughout the storage section. For these reasons, the microalgae actively carry out photosynthesis. As a large amount of carbon dioxide is fixed in the microalgae through photosynthesis, it is expected that this will contribute to mitigating or reducing the impact of climate change. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic system diagram of a culture device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic flow diagram of a culture method according to an embodiment of the present invention. [Figure 3] FIG. 3 is a graph showing the opening degree of the valves provided in the first to third containers during culture and the change in gas supply flow rate according to the opening degree of the valves. [Figure 4] FIG. 4 is a graph showing the change in the opening degree of the valves provided in the multiple containers and the change in the gas supply flow rate according to the opening degree of the valves in the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0015] FIG. 1 is a schematic system diagram of a culture device 10 according to this embodiment. The culture device 10 includes a plurality of storage units. In the first embodiment, for ease of understanding, a case where the number of storage units is three is illustrated. In addition, to make it easier to distinguish between the three storage units, the storage unit located on the leftmost side in FIG. 1 is referred to as the first storage unit 12a. The storage unit adjacent to the right of the first storage unit 12a in FIG. 1 is referred to as the second storage unit 12b. The storage unit located on the rightmost side in FIG. 1 is referred to as the third storage unit 12c. The first storage unit 12a, the second storage unit 12b, and the third storage unit 12c have the same shape and capacity.

[0016] The first to third storage sections 12a to 12c store a culture solution L and microalgae, respectively. As can be understood from this, the first to third storage sections 12a to 12c are culture tanks for culturing microalgae. The culture solution L is typically water. It is preferable to add phosphorus, nitrogen, potassium, etc. to the culture solution L in advance.

[0017] The first storage section 12a, the second storage section 12b, and the third storage section 12c are stored in the first water storage section 14a, the second water storage section 14b, and the third water storage section 14c, respectively. The first water storage section 14a, the second water storage section 14b, and the third water storage section 14c are each formed from a light-transmitting material. Water W is stored in the first water storage section 14a, the second water storage section 14b, and the third water storage section 14c, respectively. The water W is a cooling medium that cools the culture solution L in the first storage section 12a to the third storage section 12c.

[0018] The culture device 10 includes an air pump 16 as a gas supply unit. The air pump 16 sucks in and compresses atmospheric air. The air pump 16 is electrically connected to a control unit 18.

[0019] The upstream end of the flow pipe 20 is connected to the air pump 16. The flow pipe 20 extends toward the third storage section 12c. A first branch pipe 22a and a second branch pipe 22b are provided midway along the extension of the flow pipe 20. The first branch pipe 22a extends toward the first storage section 12a, and the second branch pipe 22b extends toward the second storage section 12b. The first branch pipe 22a, the second branch pipe 22b, and the downstream end 23 of the flow pipe 20 are each a gas supply line. That is, the culture device 10 is provided with a plurality of gas supply lines (three in this embodiment).

[0020] A first solenoid valve 24a is provided in the first branch pipe 22a. A second solenoid valve 24b is provided in the second branch pipe 22b, and a third solenoid valve 24c is provided at the downstream end 23 of the flow pipe 20. The first solenoid valve 24a, the second solenoid valve 24b, and the third solenoid valve 24c are electrically connected to the control unit 18. That is, the first solenoid valve 24a, the second solenoid valve 24b, and the third solenoid valve 24c open and close in response to command signals from the control unit 18. The control unit 18 can also set the first solenoid valve 24a, the second solenoid valve 24b, and the third solenoid valve 24c to any opening degree between fully open and fully closed.

[0021] A first main pipe 28a is provided at the bottom of the first water storage section 14a. The first branch pipe 22a is connected to the first main pipe 28a. The first main pipe 28a extends horizontally at the bottom of the first water storage section 14a. A plurality of first secondary pipes 30a branch off from the first main pipe 28a. The first secondary pipes 30a extend substantially vertically.

[0022] A plurality of first guide portions 32a are provided inside the first storage portion 12a. The first guide portions 32a are disposed above the first secondary pipe 30a and receive the gas (compressed air) discharged from the first secondary pipe 30a. The entire first guide portions 32a are immersed in the culture solution L.

[0023] The first accommodating section 12a is provided with a first temperature sensor 36a and a first actinometer 38a. The first temperature sensor 36a detects the temperature of the culture solution L in the first accommodating section 12a. The first actinometer 38a measures the amount of light incident on the first accommodating section 12a.

[0024] The second storage section 12b and the third storage section 12c are both configured similarly to the first storage section 12a. That is, the second storage section 12b has a second main pipe 28b, a second sub-pipe 30b, and a second guide section 32b. The second branch pipe 22b is connected to the second main pipe 28b. The second storage section 12b is provided with a second temperature sensor 36b and a second actinometer 38b. The third storage section 12c has a third main pipe 28c, a third sub-pipe 30c, and a third guide section 32c. The downstream end 23 of the flow pipe 20 is connected to the third main pipe 28c. The third storage section 12c is provided with a third temperature sensor 36c and a third actinometer 38c. The first temperature sensor 36a, the second temperature sensor 36b, and the third temperature sensor 36c are temperature detectors. The first actinometer 38a, the second actinometer 38b, and the third actinometer 38c are light amount measuring devices.

[0025] The first temperature sensor 36a, the second temperature sensor 36b, and the third temperature sensor 36c are electrically connected to the control unit 18. The control unit 18 receives the temperatures detected by the first temperature sensor 36a, the second temperature sensor 36b, and the third temperature sensor 36c as information signals. That is, the control unit 18 receives the temperatures of the culture solution L in the first accommodating unit 12a, the second accommodating unit 12b, and the third accommodating unit 12c.

[0026] The first actinometer 38a, the second actinometer 38b, and the third actinometer 38c are electrically connected to the control unit 18. The control unit 18 receives the amounts of light measured by the first actinometer 38a, the second actinometer 38b, and the third actinometer 38c as information signals. That is, the control unit 18 receives the amounts of light incident on the first housing unit 12a, the second housing unit 12b, and the third housing unit 12c.

[0027] The control unit 18 includes a first time measurement circuit 40 and a second time measurement circuit 42. The first time measurement circuit 40 measures the elapsed time from a gas supply start step S1 (described later) or the elapsed time from the end of a general step S5 (described later). The second time measurement circuit 42 separately measures the elapsed time from the start of an opening degree adjustment step S3 (described later).

[0028] A threshold temperature, which is the allowable lower limit of temperature, and a threshold light intensity, which is the allowable lower limit of light intensity, are input to the control unit 18 in advance. The control unit 18 compares the temperature of the culture solution L detected by the first temperature sensor 36a to the third temperature sensor 36c with the threshold temperature. The control unit 18 compares the light intensity measured by the first actinometer 38a to the third actinometer 38c with the threshold light intensity. Furthermore, a predetermined time is input to the control unit 18 in advance. The control unit 18 compares the elapsed time measured by the first time measurement circuit 40 or the second time measurement circuit 42 with the predetermined time.

[0029] Next, the culture method according to this embodiment will be described with reference to the schematic flow chart shown in Fig. 2. This culture method includes a gas supply start step S1, a first determination step S2, an opening adjustment step S3, a second determination step (stirring step) S4, a general step S5, and a third determination step S6. These steps S1 to S6 are executed based on sequence control by the control unit 18.

[0030] The operator inputs a command signal to "execute gas supply start step S1" to the control unit 18. This command signal is input to the control unit 18, for example, when a switch provided in the control unit 18 is turned on.

[0031] Upon receiving this command signal, the control unit 18 starts the air pump 16. The control unit 18 also adjusts the opening of the first solenoid valve 24a, the second solenoid valve 24b, and the third solenoid valve 24c to, for example, about 1 / 3 of full opening. The air pump 16 sucks in and compresses the atmosphere. Since the atmosphere contains carbon dioxide, the atmosphere compressed by the air pump 16 is a carbon dioxide-containing gas.

[0032] After activation, the air pump 16 discharges a constant amount of carbon dioxide-containing gas. That is, the air pump 16 operates at a constant output and at a rated capacity. Hereinafter, this state is also referred to as "steady operation."

[0033] Because the opening degrees of the first solenoid valve 24a, the second solenoid valve 24b, and the third solenoid valve 24c are the same, the carbon dioxide-containing gas circulating from the air pump 16 to the circulation pipe 20 is distributed approximately evenly to the first storage section 12a, the second storage section 12b, and the third storage section 12c. That is, approximately one-third of the carbon dioxide-containing gas discharged from the air pump 16 is distributed to the first branch pipe 22a and flows into the first main pipe 28a. Another approximately one-third of the carbon dioxide-containing gas discharged from the air pump 16 is distributed to the second branch pipe 22b and flows into the second main pipe 28b. The remaining approximately one-third of the carbon dioxide-containing gas discharged from the air pump 16 flows from the downstream end 23 of the circulation pipe 20 into the third main pipe 28c.

[0034] Fig. 3 is a graph showing changes in the apertures of the first solenoid valve 24a, the second solenoid valve 24b, and the third solenoid valve 24c, and changes in the supply flow rate of the carbon dioxide-containing gas to the first main pipe 28a, the second main pipe 28b, and the third main pipe 28c. Region A in Fig. 3 represents a state in which the air pump 16 is in steady operation and the apertures of the first solenoid valve 24a, the second solenoid valve 24b, and the third solenoid valve 24c are the same.

[0035] In the first storage unit 12a, the carbon dioxide-containing gas flows from the first branch pipe 22a through the first main pipe 28a and the first sub-pipe 30a into the culture solution L, and then flows into the first guide section 32a. Similarly, in the second storage unit 12b, the carbon dioxide-containing gas flows from the second branch pipe 22b through the second main pipe 28b and the second sub-pipe 30b into the culture solution L, and then flows into the second guide section 32b. Similarly, in the third storage unit 12c, the carbon dioxide-containing gas flows from the downstream end 23 of the circulation pipe 20 through the third main pipe 28c and the third sub-pipe 30c into the culture solution L, and then flows into the third guide section 32c.

[0036] In the first storage unit 12a to the third storage unit 12c, the microalgae perform photosynthesis based on the carbon dioxide in the carbon dioxide-containing gas. This allows the microalgae to be cultured in the first storage unit 12a to the third storage unit 12c. This culture causes the carbon dioxide in the culture solution L to be fixed by the microalgae. As can be seen from this, culturing the microalgae consumes carbon dioxide, which can contribute to mitigating or reducing the impact of climate change. When phosphorus, nitrogen, potassium, etc. are added to the culture solution L, the microalgae take up these inorganic substances as nutrients.

[0037] The carbon dioxide-containing gas supplied to the culture solution L stirs the culture solution L and the microalgae in the first to third storage units 12a to 12c. However, the microalgae tend to settle over time. The microalgae also tend to settle when the temperature or the amount of light decreases. To prevent the microalgae from settling, the control unit 18 controls the first to third storage units 12a to 12c to temporarily supply a large amount of carbon dioxide-containing gas. This will be explained in detail below.

[0038] The process in which microalgae cultivation progresses while the air pump 16 is operating steadily is the general process. During the general process, a first determination process S2 is executed. In the first determination process S2, the control unit 18 determines whether or not predetermined conditions preset in the control unit 18 are satisfied. In this embodiment, the predetermined conditions are the following first condition, second condition, and third condition. The first condition is that "a predetermined time has elapsed since the gas supply start process S1 was executed." The second condition is that "the temperature of the culture solution L in the first storage unit 12a to the third storage unit 12c reaches a threshold temperature." The third condition is that "the amount of light incident on the first storage unit 12a to the third storage unit 12c reaches a threshold light amount."

[0039] To make the above determination, the control unit 18 receives inputs of the temperatures detected by the first temperature sensor 36a to the third temperature sensor 36c and the light intensities measured by the first actinometer 38a to the third actinometer 38c. When the culture device 10 is installed outdoors, the light incident on the first storage unit 12a to the third storage unit 12c is sunlight. During the day, there is almost no significant difference in the temperature and light intensity. Therefore, the temperature almost never reaches the threshold temperature, and the light intensity almost never reaches the threshold light intensity. In other words, during the day, the second and third conditions are almost never met.

[0040] Meanwhile, the first time measurement circuit 40 of the control unit 18 measures the elapsed time immediately after the gas supply start step S1 is executed. When this elapsed time reaches a predetermined time input in advance to the control unit 18, the first condition is satisfied ("YES" in S2). In this case, the control unit 18 first executes the opening degree adjustment step S3, and then maintains the state in which the opening degrees of the first solenoid valve 24a to the third solenoid valve 24c are adjusted. That is, the control unit 18 executes the second determination step S4. Thereafter, the control unit 18 executes the general step S5.

[0041] In this embodiment, an example is shown in which the opening adjustment step S3 is performed first, mainly using the first solenoid valve 24a, then the opening adjustment step S3 is performed mainly using the second solenoid valve 24b, and finally the opening adjustment step S3 is performed mainly using the third solenoid valve 24c. Here, "opening adjustment mainly using the first solenoid valve 24a" refers to increasing the opening of the first solenoid valve 24a and decreasing the openings of the second solenoid valve 24b and the third solenoid valve 24c in the opening adjustment step S3. "opening adjustment mainly using the second solenoid valve 24b" refers to increasing the opening of the second solenoid valve 24b and decreasing the openings of the first solenoid valve 24a and the third solenoid valve 24c in the opening adjustment step S3. "opening adjustment mainly using the third solenoid valve 24c" refers to increasing the opening of the third solenoid valve 24c and decreasing the openings of the first solenoid valve 24a and the second solenoid valve 24b in the opening adjustment step S3.

[0042] On the other hand, the general process S5 is a process of cultivating microalgae under the condition that the air pump 16 is in steady operation and the opening degrees of the first to third solenoid valves 24a to 24c are not adjusted, as described above.

[0043] As described above, in this embodiment, the opening degree adjustment mainly performed by the first solenoid valve 24a, the opening degree adjustment mainly performed by the second solenoid valve 24b, and the opening degree adjustment mainly performed by the third solenoid valve 24c are performed in this order. That is, the opening degree adjustment mainly performed by the first solenoid valve 24a, the opening degree adjustment mainly performed by the second solenoid valve 24b, and the opening degree adjustment mainly performed by the third solenoid valve 24c are not performed simultaneously (do not overlap). In this way, a time difference is provided between the opening degree adjustment mainly performed by the first solenoid valve 24a and the opening degree adjustment mainly performed by the second solenoid valve 24b. Similarly, a time difference is provided between the opening degree adjustment mainly performed by the second solenoid valve 24b and the opening degree adjustment mainly performed by the third solenoid valve 24c.

[0044] The following describes the opening adjustment mainly performed by the first solenoid valve 24a. In this case, when a predetermined time has elapsed since the gas supply start step S1 was performed, the control unit 18 increases the opening of the first solenoid valve 24a from its previous opening. At the same time, the control unit 18 decreases the opening of the second solenoid valve 24b and the third solenoid valve 24c from their previous openings. For example, the control unit 18 fully opens the first solenoid valve 24a and fully closes the second solenoid valve 24b and the third solenoid valve 24c. As a result, the entire amount of carbon dioxide-containing gas from the air pump 16 is supplied to the first storage unit 12a. In contrast, the supply flow rate of the carbon dioxide-containing gas to the second storage unit 12b and the third storage unit 12c is 0. This situation is shown in area B of FIG. 3.

[0045] The second time measurement circuit 42 of the control unit 18 measures the elapsed time from immediately after the opening adjustment step S3 mainly performed by the first solenoid valve 24a is executed. During this measurement, the second determination step S4 is executed. That is, the control unit 18 determines whether the elapsed time since the opening adjustment step S3 mainly performed by the first solenoid valve 24a has reached a predetermined time input to the control unit 18 in advance.

[0046] When the elapsed time reaches a predetermined time ("YES" in S4), the control unit 18 transitions the culture method to the general step S5. Specifically, when the elapsed time since the opening adjustment step S3 has been performed reaches a predetermined time, the control unit 18 reduces the opening of the first solenoid valve 24a to a value smaller than that in the opening adjustment step S3. At the same time, the control unit 18 increases the opening of the second solenoid valve 24b and the third solenoid valve 24c to a value larger than that in the opening adjustment step S3. For example, the control unit 18 returns the first solenoid valve 24a to its original opening (one-third of full open), and returns the second solenoid valve 24b and the third solenoid valve 24c to their original openings (one-third of full open). As a result, the carbon dioxide-containing gas from the air pump 16 is distributed approximately evenly to the first storage unit 12a to the third storage unit 12c, as described above. This situation is shown in region C of FIG. 3. Note that the predetermined time may be, for example, an appropriate time between several tens of seconds and several minutes. The same applies below.

[0047] In this way, a large amount of carbon dioxide-containing gas is supplied to the first storage unit 12a from the time the opening adjustment step S3 is performed until the process moves to the general step S5 (while the second determination step S4 is being performed). This large amount of carbon dioxide-containing gas stirs the culture solution L in the first storage unit 12a. Therefore, the microalgae in the culture solution L are also stirred. In this way, the second determination step S4 is an agitation step that vigorously stirs the culture solution L and the microalgae.

[0048] Because the culture solution L and the microalgae are strongly stirred, precipitation or aggregation of the microalgae in the first storage section 12a is prevented. Therefore, light is incident on the microalgae in the first storage section 12a approximately evenly. This allows the microalgae in the first storage section 12a to actively photosynthesize and sufficiently fix carbon dioxide. As a result, a sufficient amount of carbon dioxide can be consumed.

[0049] In the third determination step S6, the first time measurement circuit 40 of the control unit 18 measures the elapsed time from immediately after the general step S5 is executed. When this elapsed time reaches a predetermined time input in advance to the control unit 18 ("YES" in S6), the control unit 18 executes the opening degree adjustment step S3, which mainly controls the second solenoid valve 24b.

[0050] Specifically, when a predetermined time has elapsed since the execution of the general step S5, the control unit 18 increases the opening degree of the second solenoid valve 24b. At the same time, the control unit 18 decreases the opening degrees of the first solenoid valve 24a and the third solenoid valve 24c. For example, the control unit 18 fully opens the second solenoid valve 24b and fully closes the first solenoid valve 24a and the third solenoid valve 24c. As a result, the entire amount of carbon dioxide-containing gas from the air pump 16 is supplied to the second storage unit 12b. In contrast, the supply flow rate of the carbon dioxide-containing gas to the first storage unit 12a and the third storage unit 12c is 0. This situation is shown in area D of FIG. 3.

[0051] The second time measurement circuit 42 of the control unit 18 measures the elapsed time from immediately after the opening adjustment step S3 mainly performed by the second solenoid valve 24b is executed. During this measurement, the second determination step S4 is executed. That is, the control unit 18 determines whether the elapsed time since the opening adjustment step S3 mainly performed by the second solenoid valve 24b has reached a predetermined time input to the control unit 18 in advance.

[0052] When the elapsed time reaches a predetermined time, the control unit 18 transitions the culture method to the general step S5. Specifically, when the elapsed time since the opening adjustment step S3, mainly performed by the second solenoid valve 24b, reaches a predetermined time, the control unit 18 reduces the opening of the second solenoid valve 24b to a value smaller than that during the opening adjustment step S3. At the same time, the control unit 18 increases the opening of the first solenoid valve 24a and the third solenoid valve 24c to a value larger than that during the opening adjustment step S3. For example, the control unit 18 returns the second solenoid valve 24b to its original opening (one-third of full open), and returns the first solenoid valve 24a and the third solenoid valve 24c to their original openings (one-third of full open). As a result, the carbon dioxide-containing gas from the air pump 16 is distributed approximately evenly to the first to third storage sections 12a to 12c, as described above. This situation is shown in region E of FIG. 3.

[0053] A large amount of carbon dioxide-containing gas is supplied to the second storage unit 12b from the time when the opening adjustment step S3, mainly performed by the second solenoid valve 24b, is executed until the general step S5 is executed. This large amount of carbon dioxide-containing gas stirs the culture solution L in the second storage unit 12b. Therefore, the microalgae in the culture solution L are also stirred. This prevents the microalgae from settling or flocculating in the second storage unit 12b. Therefore, light is incident on the microalgae in the second storage unit 12b approximately evenly. This allows the microalgae in the second storage unit 12b to actively photosynthesize and sufficiently fix carbon dioxide. As a result, a sufficient amount of carbon dioxide can be consumed.

[0054] The first time measurement circuit 40 of the control unit 18 measures the elapsed time immediately after the general step S5 is executed. When this elapsed time reaches a predetermined time input in advance to the control unit 18, the control unit 18 executes the opening degree adjustment step S3, which mainly controls the third solenoid valve 24c.

[0055] Specifically, when a predetermined time has elapsed since the execution of the general step S5, the control unit 18 increases the opening degree of the third solenoid valve 24c from the previous opening degree. At the same time, the control unit 18 decreases the opening degrees of the first solenoid valve 24a and the second solenoid valve 24b from the previous opening degrees. For example, the control unit 18 fully opens the third solenoid valve 24c and fully closes the first solenoid valve 24a and the second solenoid valve 24b. As a result, the entire amount of carbon dioxide-containing gas from the air pump 16 is supplied to the third storage unit 12c. In contrast, the supply flow rate of the carbon dioxide-containing gas to the first storage unit 12a and the second storage unit 12b is 0. This situation is represented by region F in FIG. 3.

[0056] The second time measurement circuit 42 of the control unit 18 measures the elapsed time from immediately after the opening adjustment step S3 mainly performed by the third solenoid valve 24c is executed. During this measurement, the second determination step S4 is executed. That is, the control unit 18 determines whether the elapsed time since the opening adjustment step S3 mainly performed by the third solenoid valve 24c has reached a predetermined time input to the control unit 18 in advance.

[0057] When the elapsed time reaches a predetermined time, the control unit 18 transitions the culture method to the general step S5. Specifically, when the elapsed time since the opening adjustment step S3, mainly performed by the third solenoid valve 24c, reaches a predetermined time, the control unit 18 reduces the opening of the third solenoid valve 24c to a value smaller than that during the opening adjustment step S3. At the same time, the control unit 18 increases the opening of the first solenoid valve 24a and the second solenoid valve 24b to a value larger than that during the opening adjustment step S3. For example, the control unit 18 returns the third solenoid valve 24c to its original opening (one-third of full open), and returns the first solenoid valve 24a and the second solenoid valve 24b to their original openings (one-third of full open). As a result, the carbon dioxide-containing gas from the air pump 16 is distributed approximately evenly to the first to third storage sections 12a to 12c, as described above. This situation is illustrated in area G of FIG. 3.

[0058] A large amount of carbon dioxide-containing gas is supplied to the third storage unit 12c from the time when the opening adjustment step S3, mainly performed by the third solenoid valve 24c, is executed until the general step S5 is executed. This large amount of carbon dioxide-containing gas agitates the culture solution L in the third storage unit 12c. Therefore, the microalgae in the culture solution L are also agitated. This prevents the microalgae from settling or flocculating in the third storage unit 12c. Therefore, light is incident on the microalgae in the third storage unit 12c approximately evenly. This allows the microalgae in the third storage unit 12c to actively photosynthesize and sufficiently fix carbon dioxide. As a result, a sufficient amount of carbon dioxide can be consumed.

[0059] As a result, microalgae can be cultured satisfactorily in the first to third storage sections 12a to 12c.

[0060] At night, the temperature of the culture solution L drops compared to daytime, and the amount of light incident on the first to third storage units 12a to 12c decreases. Under such circumstances, the second or third condition may be met before the first condition is met. In this case, the control unit 18 sequentially adjusts the opening degree primarily using the first solenoid valve 24a, the second solenoid valve 24b, and the third solenoid valve 24c, as described above. Therefore, even under circumstances where microalgae tend to settle in a relatively short time, such as at night, microalgae can be successfully cultivated in the first to third storage units 12a to 12c.

[0061] As described above, according to this embodiment, by performing the opening adjustment step S3, a large amount of carbon dioxide-containing gas can be temporarily supplied to the culture solution L. Therefore, while the microalgae are being cultured as described above, the air pump 16 is maintained in steady operation. That is, even when a large amount of carbon dioxide-containing gas is supplied to the culture solution L in order to agitate the microalgae, it is not necessary to increase the discharge rate of the carbon dioxide-containing gas from the air pump 16. For the reasons described above, it is not necessary to select an air pump 16 with excessive capacity that discharges a large amount of carbon dioxide-containing gas.

[0062] In other words, according to this embodiment, it is possible to select an air pump 16 with an appropriate capacity to discharge a sufficient amount of carbon dioxide-containing gas for culturing microalgae. Therefore, an increase in power consumption per unit time is avoided. This allows for a reduction in the running costs of culturing microalgae.

[0063] As described above, this embodiment is a culture method for culturing microalgae in a culture device (10) including a plurality of storage units (12a to 12c) for storing a culture solution (L) and microalgae, a gas supply unit (16) for supplying gas to the plurality of storage units, and a plurality of gas supply lines (20, 22a, 22b) for connecting the gas supply unit to the plurality of storage units, wherein a plurality of valves (24a to 24c) are provided on the plurality of gas supply lines, and during the culturing of the microalgae in the plurality of storage units, The present invention discloses a culture method comprising an opening adjustment step (S3) of adjusting the opening of at least one of the plurality of valves, and an agitation step (S4) of culturing the microalgae in a state in which the opening of at least one of the plurality of valves is adjusted, wherein in the opening adjustment step, the opening of at least one of the plurality of valves is adjusted to stop the supply of the gas to at least one storage section among the plurality of storage sections or reduce the supply flow rate, and increase the supply flow rate of the gas to at least one remaining storage section.

[0064] This embodiment discloses a culture device (10) for culturing microalgae in a culture solution (L), comprising: a plurality of storage sections (12a to 12c) for storing the culture solution and the microalgae; a gas supply section (16) for supplying gas to the plurality of storage sections; a plurality of gas supply lines (20, 22a, 22b) connecting the gas supply section to the plurality of storage sections; a plurality of valves (24a to 24c) provided on the plurality of gas supply lines; and a control section (18) for individually adjusting the apertures of the plurality of valves, wherein the control section adjusts the aperture of at least one of the plurality of valves while the microalgae are being cultured in the plurality of storage sections, thereby stopping the supply of the gas to at least one of the plurality of storage sections or reducing the supply flow rate, and increasing the supply flow rate of the gas to at least one remaining storage section.

[0065] By adjusting the opening degree, the gas supply is stopped or the supply flow rate is reduced in at least one of the multiple storage sections, while the gas supply flow rate is increased in at least one remaining storage section. In other words, the gas supply flow rate is adjusted.

[0066] Therefore, even if the gas supply flow rate from the gas supply unit is constant, a large amount of gas can be temporarily supplied to at least one of the multiple storage units, eliminating the need to select a gas supply unit with excess capacity.

[0067] That is, in this embodiment, it is possible to use a gas supply unit that consumes less power per unit time, thereby reducing the running costs for the culture.

[0068] In the storage section where the gas supply flow rate is temporarily increased, the microalgae and culture solution are agitated. This prevents the microalgae from settling or flocculating. This allows light to be incident on the microalgae approximately evenly. Furthermore, as the culture solution is agitated, carbon dioxide is diffused throughout the storage section. For these reasons, the microalgae actively carry out photosynthesis. As a large amount of carbon dioxide is fixed in the microalgae through photosynthesis, it is expected that this will contribute to mitigating or reducing the impact of climate change.

[0069] This embodiment discloses a culture method that includes multiple opening adjustment steps, including the opening adjustment step, and that increases the gas supply flow rate in all of the multiple storage sections by performing the multiple opening adjustment steps.

[0070] This embodiment discloses a culture device in which the control unit performs multiple opening adjustments, including adjusting the opening of at least one of the multiple valves, and by performing the multiple opening adjustments, the supply flow rate of the gas is increased in all of the multiple storage sections.

[0071] This allows the gas supply flow rate to all of the storage units to be temporarily increased in sequence. Therefore, even if the gas supply flow rate from the gas supply unit is constant, it is possible to prevent the precipitation or aggregation of microalgae in all of the storage units. As a result, it becomes possible for the microalgae to carry out active photosynthesis in all of the storage units.

[0072] This embodiment discloses a culture method in which the multiple opening degree adjustment steps for the multiple storage sections do not overlap with each other.

[0073] This embodiment discloses an incubation device in which the control unit performs the plurality of opening degree adjustments for the plurality of storage units without overlapping each other.

[0074] In this case, simultaneous supply of gas to a plurality of storage units is avoided, and therefore, gas can be supplied at a sufficient flow rate to storage units that require stirring of the culture solution.

[0075] This embodiment discloses a culture method in which, in the opening degree adjusting step, at least one valve among the plurality of valves is fully opened, and at least one remaining valve is fully closed.

[0076] This embodiment discloses a culture device in which the control unit fully opens at least one valve among the plurality of valves and fully closes at least one remaining valve.

[0077] In this case, no gas is distributed to the container with the fully closed valve. On the other hand, a large amount of gas is distributed to the container with the fully open valve. Therefore, a larger amount of gas can be supplied to the container that requires agitation of the culture solution.

[0078] This embodiment discloses a culture method in which the opening degree adjusting step is executed when a predetermined condition is satisfied.

[0079] This embodiment discloses a culture device in which the control unit adjusts the degree of opening of at least one of the plurality of valves when a preset condition is satisfied.

[0080] The predetermined condition is, for example, a condition that makes it easy for microalgae to settle. When such a situation occurs, the opening adjustment is performed, so that the microalgae can be prevented from settling or agglomerating.

[0081] Even when sufficient gas for culturing microalgae is continuously supplied to the storage unit, the microalgae tend to settle over time. To avoid this, it is preferable to perform the opening adjustment and the second opening adjustment after a predetermined time has elapsed. In other words, this embodiment discloses a culture method in which the predetermined condition is met after a predetermined time has elapsed.

[0082] This embodiment discloses a culture device in which the specified condition is the passage of a specified time, and the control unit adjusts the opening degree of at least one of the plurality of valves when the specified time has passed.

[0083] Microalgae are also prone to settling when the ambient temperature drops. To avoid this, it is preferable to perform the opening adjustment and the second opening adjustment when the temperature of the culture solution reaches the lower limit of tolerance. That is, this embodiment discloses a culture method in which the predetermined condition is when the temperature of the culture solution reaches a threshold temperature or lower.

[0084] This embodiment discloses a culture device that includes a temperature detector (36a to 36c) that measures the temperature of the culture solution, the predetermined condition being that the temperature reaches a threshold temperature or lower, and the control unit adjusts the opening degree of at least one of the plurality of valves when the temperature reaches the threshold temperature or lower.

[0085] Microalgae also tend to settle when the amount of light incident on the storage units decreases. To avoid this, it is preferable to perform the opening adjustment and the second opening adjustment when the amount of light reaches the allowable lower limit. That is, this embodiment discloses a culture method in which the predetermined condition is when the amount of light irradiated to the multiple storage units reaches or exceeds a threshold light amount.

[0086] This embodiment discloses a culture device that includes a light intensity meter (38a to 38c) that measures the amount of light irradiated to the plurality of storage sections, the predetermined condition being that the amount of light reaches or falls below a threshold amount of light, and the control unit adjusts the opening degree of at least one of the plurality of valves when the amount of light reaches or falls below the threshold amount of light.

[0087] This embodiment discloses a culture method in which a pump (16) is used as the gas supply unit, and the output of the pump is kept constant when the opening adjustment step is performed and when a general step (S5) of supplying the gas to all of the plurality of storage units is performed without performing the opening adjustment step.

[0088] In this embodiment, the gas supply unit is a pump (16), and the culture apparatus is disclosed in which the pump operates at a constant output when adjusting the opening of at least one of the plurality of valves, and when supplying the gas to all of the plurality of storage units without making the adjustment.

[0089] As described above, according to this embodiment, even if the gas supply flow rate from a gas supply unit such as a pump is constant, a large amount of carbon dioxide-containing gas can be temporarily supplied to a specified storage unit. In other words, even when a large amount of carbon dioxide-containing gas is supplied to the culture solution to agitate the microalgae, the pump can be operated at a constant output.

[0090] That is, in this case, when a large amount of carbon dioxide-containing gas is temporarily supplied to one storage unit, there is no need to increase the pump discharge rate. Therefore, there is no need to select a pump with excessive capacity to discharge a large amount of carbon dioxide-containing gas. In other words, it is possible to select a pump with appropriate capacity to discharge a sufficient amount of gas for culturing microalgae. Therefore, an increase in power consumption per unit time is avoided. This makes it possible to reduce the running costs of culturing microalgae.

[0091] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention.

[0092] For example, the number of storage units is not limited to 3. The number of storage units may be 2, or may be 4 or more. The number of gas supply lines and valves is determined depending on the number of storage units.

[0093] In the opening adjustment step S3, it is sufficient that the opening of the main valve is larger than the opening of the other valves. In other words, the opening of each valve is not particularly limited. For example, the opening of the main valve (the valve whose opening is larger) is not limited to being fully open. Similarly, the opening of the other valves (the valve whose opening is smaller) is not limited to being fully closed.

Claims

1. A culture method for culturing microalgae in a culture device (10) including a plurality of storage sections (12a to 12c) for storing a culture solution (L) and microalgae, a gas supply section (16) for supplying gas to the plurality of storage sections, and a plurality of gas supply lines (20, 22a, 22b) for respectively connecting the gas supply section and the plurality of storage sections, a plurality of valves (24a to 24c) are provided on the plurality of gas supply lines, respectively; An opening adjustment step (S3) of adjusting the opening of at least one of the plurality of valves while culturing the microalgae in the plurality of storage units; A stirring step (S4) of culturing the microalgae while adjusting the opening degree of at least one of the plurality of valves; and In the opening degree adjusting step, by adjusting the opening degree of at least one of the plurality of valves, the supply of the gas to at least one of the plurality of storage units is stopped or the supply flow rate is reduced, and the supply flow rate of the gas to at least one remaining storage unit is increased; A culture method in which a pump (16) is used as the gas supply unit, and the output of the pump is kept constant when the opening adjustment step is performed and when a general step (S5) of supplying the gas to all of the plurality of storage units is performed without performing the opening adjustment step.

2. The culture method according to claim 1, further comprising a plurality of opening degree adjustment steps including the opening degree adjustment step, The culture method, wherein the gas supply flow rate is increased in all of the plurality of storage sections by performing the opening degree adjustment step multiple times.

3. 3. The culture method according to claim 2, wherein the plurality of opening degree adjusting steps for the plurality of containers do not overlap with each other.

4. 2. The culture method according to claim 1, wherein the opening adjustment step is performed by fully opening at least one of the plurality of valves and fully closing at least one remaining valve.

5. 2. The culture method according to claim 1, wherein the opening adjustment step is carried out when a predetermined condition is satisfied for at least one of the elapsed time since the supply of the gas to the plurality of storage sections started, the temperature of the culture solution, and the amount of light irradiated to the plurality of storage sections.

6. 6. The culture method according to claim 5, wherein the condition is when the elapsed time reaches a set time.

7. 6. The culture method according to claim 5, wherein the condition is when the temperature of the culture medium reaches a threshold temperature or lower.

8. 6. The culture method according to claim 5, wherein the condition is that the amount of light irradiated onto the plurality of containers reaches a threshold amount of light or less.

9. A culture device (10) for culturing microalgae in a culture solution (L), A plurality of storage units (12a to 12c) for storing the culture solution and the microalgae; a gas supply unit (16) that supplies gas to the plurality of storage units; a plurality of gas supply lines (20, 22a, 22b) respectively connecting the gas supply unit and the plurality of storage units; a plurality of valves (24a to 24c) respectively provided on the plurality of gas supply lines; a control unit (18) that individually adjusts the opening degrees of the plurality of valves; Equipped with The control unit adjusts the opening degree of at least one of the plurality of valves while culturing the microalgae in the plurality of storage units, thereby stopping the supply of the gas to at least one of the plurality of storage units or reducing the supply flow rate, and increasing the supply flow rate of the gas to at least one remaining storage unit. The gas supply unit is a pump (16), and the pump is operated at a constant output when adjusting the opening of at least one of the plurality of valves, and when supplying the gas to all of the plurality of storage units without making the adjustment.

10. 10. The culture apparatus according to claim 9, wherein the control unit adjusts the opening degree of the at least one of the plurality of valves a plurality of times, The culture device increases the supply flow rate of the gas in all of the plurality of storage sections by adjusting the opening degree multiple times.

11. The culture apparatus according to claim 10, wherein the control unit performs the plurality of opening degree adjustments for the plurality of storage units without overlapping each other.

12. 10. The culture apparatus according to claim 9, wherein the control unit controls at least one of the plurality of valves to be fully open and at least one remaining valve to be fully closed.

13. 10. The culture apparatus according to claim 9, wherein the control unit adjusts the opening degree of at least one of the plurality of valves when a predetermined condition is satisfied for at least one of the elapsed time since the supply of the gas to the plurality of storage units started, the temperature of the culture solution, and the amount of light irradiated to the plurality of storage units.

14. 14. The culture apparatus according to claim 13, wherein the control unit adjusts the opening degree of at least one of the plurality of valves when the elapsed time reaches a set time.

15. The culture device according to claim 13, further comprising a temperature detector (36a to 36c) for measuring the temperature of the culture solution, and the control unit adjusts the opening degree of at least one of the plurality of valves when the temperature reaches or falls below a threshold temperature.

16. The culture device according to claim 13, further comprising a light intensity meter (38a to 38c) for measuring the amount of light irradiated to the plurality of storage sections, and the control unit adjusts the opening degree of at least one of the plurality of valves when the amount of light reaches or falls below a threshold light intensity.

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