Algae cultivation system and algae cultivation method

Abstract

To provide an algae culture system and an algae culture method in which energy loss does not occur in separating carbon dioxide.SOLUTION: An algae culture system comprises: a carbon dioxide supply source which supplies gas containing carbon dioxide; a carbon dioxide recovery part which brings carbon dioxide lean absorption liquid in contact with the gas containing carbon dioxide to obtain carbon dioxide rich absorption liquid; and an algae culture device which is provided adjacent to the carbon dioxide supply source and the carbon dioxide recovery part, is supplied with the carbon dioxide rich absorption liquid as a nutrient source from the carbon dioxide recovery part, and capable of culturing algae.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an algae cultivation system and an algae cultivation method capable of cultivating algae. [Background technology]

[0002] A method for recycling carbon dioxide generated from a thermal power plant or the like is known (see, for example, Patent Document 1). In this method, exhaust gas from the thermal power plant or the like is passed through an amine or the like, causing the amine or the like to absorb the carbon dioxide. The carbon dioxide absorbed by the amine or the like is separated from the amine or the like by heating or other means and recovered. The recovered carbon dioxide is added to a microalgae culture pond attached to the thermal power plant or the like. The microalgae cultured in the microalgae culture pond are recovered and dried, and then used as fuel or the like in the thermal power plant or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-276648 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above Patent Document 1, in order to separate carbon dioxide from the amine or the like that has adsorbed carbon dioxide, it is necessary to heat the amine or the like to a high temperature of, for example, 100° C. or higher. Therefore, a huge energy loss occurs when separating carbon dioxide from the amine or the like.

[0005] Therefore, an object of the present invention is to provide an algae cultivation system and an algae cultivation method that do not cause energy loss during carbon dioxide separation. [Means for solving the problem]

[0006] The above problems are solved by the present invention described below.

[0007] That is, the algae culture system of the present invention (1) comprises a carbon dioxide supply source that supplies a carbon dioxide-containing gas; a carbon dioxide recovery unit that contacts the carbon dioxide-containing gas with a carbon dioxide-lean absorption liquid to obtain a carbon dioxide-rich absorption liquid; an algae cultivator capable of cultivating algae by receiving the carbon dioxide-rich absorption solution from the carbon dioxide recovery unit as a nutrient source; Equipped with.

[0008] The algae culture system of the present invention (2) is the algae culture system according to (1), wherein the carbon dioxide lean absorption liquid and the carbon dioxide rich absorption liquid are absorption liquids containing an absorbent, The absorbent is ammonia or an amine compound.

[0009] In the algae culture system of the present invention (3), the absorbent is ammonia or an organic amine compound.

[0010] The algae culture system of the present invention (4) is the algae culture system according to any one of (1) to (3), The apparatus further includes an algae harvesting device for harvesting the algae cultivated in the algae culturing vessel.

[0011] The algae culture system of the present invention (5) is the algae culture system according to any one of (1) to (4), wherein the algae are photosynthetic algae.

[0012] The method for cultivating algae according to the present invention (6) includes supplying a carbon dioxide-containing gas from a carbon dioxide supply source, a carbon dioxide-rich absorption liquid is obtained by contacting the carbon dioxide-containing gas with a carbon dioxide-lean absorption liquid in a carbon dioxide recovery section; The carbon dioxide-rich absorbing liquid is supplied from the carbon dioxide recovery unit to an algae culture vessel as a nutrient source, and algae are cultured in the algae culture vessel.

[0013] The algae culture method of the present invention (7) is the algae culture method according to (6), wherein the carbon dioxide lean absorption liquid and the carbon dioxide rich absorption liquid are absorption liquids containing an absorbent, The absorbent is ammonia or an amine compound.

[0014] The method for cultivating algae according to the present invention (8) is the method for cultivating algae according to the present invention (7), wherein the absorbent is ammonia or an organic amine compound.

[0015] The method for cultivating algae according to the present invention (9) is the method for cultivating algae according to any one of (6) to (8), wherein the algae are capable of photosynthesis. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide an algae cultivation system and an algae cultivation method that do not cause energy loss during carbon dioxide separation. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a system diagram showing an algae culture system according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram showing a carbon dioxide recovery unit of the algae cultivation system shown in FIG. [Figure 3] FIG. 2 is a top view showing the open pond raceway type algae cultivator of the algae cultivating system shown in FIG. 1. [Figure 4] FIG. 10 is a front view showing a closed algae culturing vessel of the algae culturing system of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] An algae cultivation system of the present invention will be described with reference to Figure 1. The algae cultivation system 10 includes a carbon dioxide supply source 1 that supplies exhaust gas (carbon dioxide-containing gas), a carbon dioxide recovery unit 2 that recovers carbon dioxide from the exhaust gas (carbon dioxide-containing gas) generated by the carbon dioxide supply source 1, an algae cultivator 5 that is provided adjacent to the carbon dioxide supply source 1 and the carbon dioxide recovery unit 2 or at a location remote from them, and an algae recovery device 6 that recovers algae cultivated in the algae cultivator 5. The algae recovery device 6 is composed of, for example, a power shovel or other heavy machinery that can recover the cultivated algae from the bottom of the algae cultivator 5. The algae recovery device 6 is not limited to heavy machinery, and may also be a pump that can pump up the algae together with the culture solution.

[0019] The carbon dioxide supply source 1 is a factory or the like that releases a carbon dioxide-containing gas as an exhaust gas, and is, for example, equipment such as a blast furnace, lime kiln, heating furnace, reactor, or boiler found in a power plant, steel mill, cement plant, oil refinery, chemical plant, etc. Alternatively, the carbon dioxide supply source 1 may be the atmosphere.

[0020] 2, the carbon dioxide capture unit 2 is formed in the shape of a tower extending in the vertical direction. The carbon dioxide capture unit 2 has a cylindrical absorption tower 11 having a contact mechanism 19a provided therein and composed of a mesh filter (mesh) or the like, a first storage section 14a for storing the carbon dioxide-lean absorption solution 3, a first flow path 21 connecting the upper part of the absorption tower 11 and the first storage section 14a, a second storage section 15a for storing the carbon dioxide-rich absorption solution 4 after the carbon dioxide absorption reaction, a second flow path 22 connecting the lower part of the absorption tower 11 and the second storage section 15a, and a third flow path 23 connecting the carbon dioxide supply source 1 and the lower part of the absorption tower 11.

[0021] The first flow path 21 can supply the carbon dioxide-lean absorption solution 3 from the first storage section 14a to the absorption tower 11. The second flow path 22 can flow the carbon dioxide-rich absorption solution 4 from the absorption tower 11 toward the second storage section 15a. The third flow path 23 can supply gaseous carbon dioxide from the carbon dioxide supply source 1 into the absorption tower 11.

[0022] The carbon dioxide lean absorbing solution 3 is an absorbing solution that has not absorbed carbon dioxide. The carbon dioxide lean absorbing solution 3 becomes a carbon dioxide rich absorbing solution 4 after absorbing carbon dioxide.

[0023] Examples of the absorbent contained in the carbon dioxide lean absorption solution 3 include ammonia and all amine-based compounds, for example, alkanolamines such as monoethanolamine, diethanolamine, diisopropanolamine, dimethyldiethanolamine, and triethanolamine, amino alcohols such as aminodiethylene glycol, hindered amine-based compounds, piperazine-based compounds, piperidine-based compounds, polyalkylpolyamine-based compounds, amino acid-based compounds such as 5-aminolevulinic acid, amino acid salt-based compounds, and derivatives thereof, and organic amine-based compounds.

[0024] The absorbent is preferably ammonia or an organic amine compound. The absorbent may be one type or a combination of two or more types in any mixing ratio. The absorbent preferably has a high absorption rate, a large amount of carbon dioxide absorption, and is thermally stable.

[0025] The carbon dioxide lean absorbing solution 3 can be, for example, an aqueous solution of an absorbent. The absorbing solution is an aqueous solution of ammonia or any amine compound, preferably an aqueous solution of ammonia or an organic amine, and more preferably an aqueous solution of ammonia, alkanolamine, or 5-aminolevulinic acid. When an aqueous solution of alkanolamine is used as the carbon dioxide lean absorbing solution 3, an aqueous solution of alkanolamine with a concentration of 15 to 45 mass % is particularly preferred.

[0026] The carbon dioxide lean absorption liquid 3 and the carbon dioxide rich absorption liquid 4 are preferably non-toxic to algae, but compounds that are somewhat harmful to algae are acceptable. For example, by installing the algae culture vessel 5 as an open system outdoors and enlarging it to a certain extent (an oval circuit shape with a total length of 50 m to several km, an open pond / raceway shape), toxicity can be reduced through dilution. Furthermore, with regard to ammonia, this is because naturally occurring nitrifying bacteria (ammonia-oxidizing bacteria, nitrite-oxidizing bacteria) can nitrify ammonia to nitrite and then to nitrate. Nitrate can be absorbed by algae as a nutrient (nitrogen source). Similarly, amine compounds other than ammonia (organic amine compounds) are decomposed by naturally occurring bacteria (e.g., Bacillus bacteria living in the bottom sediment of the algae culture vessel 5) and absorbed by algae as nutrients. 5-aminolevulinic acid is not toxic to algae; rather, it is absorbed directly by algae, promoting their growth. Furthermore, instead of constantly supplying the carbon dioxide-rich absorbing solution 4, supplying it intermittently at predetermined time intervals can also reduce toxicity to algae due to the dilution effect.

[0027] The algae cultivator 5 may be provided at a position adjacent to the carbon dioxide supply source 1 and the carbon dioxide capture unit 2. Alternatively, if space cannot be secured adjacent to the carbon dioxide supply source 1 and the carbon dioxide capture unit 2, the algae cultivator 5 may be provided at a position physically separated from them. In this case, the carbon dioxide-rich absorbing liquid 4 can be transported from the carbon dioxide capture unit 2 to the algae cultivator 5 by an appropriate transport means such as a vehicle such as a tanker truck or a ship such as a tanker. Alternatively, the carbon dioxide-rich absorbing liquid 4 may be supplied from the carbon dioxide capture unit 2 to the algae cultivator 5 via a pipeline or the like.

[0028] 3, the algae culture vessel 5 has a tank-shaped algae culture vessel main body 31 filled with a culture solution, a water wheel mechanism 32 mounted on a float member, a water intake section 33 for taking in the culture solution from the algae culture vessel main body 31, a mixing section 34 for mixing the carbon dioxide-rich absorbing solution 4 with the culture solution taken in from the water intake section 33, and a drainage section 35 for returning the culture solution and the carbon dioxide-rich absorbing solution 4 mixed in the mixing section 34 to the algae culture vessel main body 31. The mixing section 34 is connected to a second storage section 15a in which the carbon dioxide-rich absorbing solution 4 is stored.

[0029] The algae culture vessel main body 31 is preferably installed in a sunny location so that the algae to be grown can efficiently photosynthesize. Furthermore, the algae culture vessel main body 31 is preferably installed in a relatively warm location throughout the year. The algae culture vessel main body 31 can be constructed in a variety of forms. The algae culture vessel main body 31 can be formed by digging a hole in the ground and covering the bottom with a waterproof sheet, or it can be constructed without a waterproof sheet. Alternatively, the algae culture vessel main body 31 can be constructed by combining multiple concrete blocks into a tank shape.

[0030] The water wheel mechanism 32 is connected to a drive source such as a motor (not shown), and by rotating it can stir the culture solution in the algae culture vessel 5 and mix the culture solution uniformly. It is preferable that the float member is fixed in position relative to the algae culture vessel main body 31 by a rope or the like. There may be multiple water wheel mechanisms 32.

[0031] The algae to be cultured are so-called green algae. The algae to be cultured contain chloroplasts and can grow and multiply by photosynthesis using sunlight. In other words, the algae to be cultured are algae capable of photosynthesis. An appropriate culture medium can be selected and used depending on the type of algae to be grown. For example, if the algae to be grown is Chlorella, then the known culture mediums shown in Table 1, such as urea culture medium, nitrate culture medium (N-25), nitrate culture medium (N-30), and nitrate culture medium (N-50), can be used as the culture medium.

[0032] [Table 1] * Fe: 1.0, Ca: 0.5, Zn: 0.1, Mn: 0.1, Cu: 0.02, Mo: 0.01 ppm

[0033] A mixture obtained by mixing, for example, 1 to 30% by mass, preferably 5 to 10% by mass, of the carbon dioxide-rich absorption solution 4 as a nitrogen source and a carbon source with the above culture solution (urea culture solution, nitrate culture solution) can be used as the modified culture solution.

[0034] Alternatively, when the algae to be grown are Euglena, for example, the well-known Cramer and Myers medium (CM medium) shown in Table 2 can be used as the culture medium.

[0035] [Table 2]

[0036] A mixture obtained by mixing, for example, 1 to 30% by mass, preferably 5 to 10% by mass of the carbon dioxide-rich absorption solution 4 as a nitrogen source and a carbon source with the above culture solution (CM medium) can be used as the modified culture solution.

[0037] When the algae to be grown are Euglena, for example, the known Koren and Hunter medium (KH medium) shown in Table 3 can be used as the culture medium.

[0038] [Table 3]

[0039] The modified culture medium can be prepared by mixing, for example, 1 to 30% by mass, preferably 5 to 10% by mass, of the carbon dioxide-rich absorption solution 4 with the above culture medium (KH medium) as a nitrogen source and a carbon source. When the algae to be grown are other than those mentioned above, a known culture medium (medium) suitable for culturing the algae can be appropriately used, and the modified culture medium can be prepared by mixing, for example, 1 to 30% by mass, preferably 5 to 10% by mass of the carbon dioxide-rich absorption solution 4 with the algae as a nitrogen source and a carbon source.

[0040] Next, the operation of the algae cultivation system 10 of this embodiment will be described with reference to FIGS. 1 to 3. Exhaust gas (gaseous carbon dioxide) is supplied from the carbon dioxide supply source 1 to the lower part of the absorption tower 11 via the third flow path 23. By driving a pump or the like (not shown), the carbon dioxide-lean absorbing solution 3 in the first storage section 14a is supplied to the upper part of the absorption tower 11 via the second flow path 22. Therefore, the gaseous carbon dioxide flows upward in the absorption tower 11. On the other hand, the carbon dioxide-lean absorbing solution 3 flows downward in the absorption tower 11. As a result, the gaseous carbon dioxide and the carbon dioxide-lean absorbing solution 3 come into contact with each other in a countercurrent manner in the absorption tower 11. At this time, the carbon dioxide in the gaseous carbon dioxide supply source 1 reacts with the absorbent in the carbon dioxide-lean absorbing solution 3. As a result, the carbon dioxide is reactively absorbed by the carbon dioxide-lean absorbing solution 3. As a result, a carbon dioxide-rich absorbing solution 4 is produced and accumulates at the bottom of the absorption tower 11. The carbon dioxide-rich absorption solution 4 accumulated at the bottom of the absorption tower 11 is sent to the second storage section 15a by gravity via the second flow path 22. The residue gas 7 purified by recovering carbon dioxide from the gaseous carbon dioxide is released into the atmosphere from the top of the absorption tower 11.

[0041] The carbon dioxide-rich absorption liquid 4 stored in the second storage section 15a is supplied into the algae culture vessel 5 by driving a pump or the like (not shown). The algae culture vessel 5 is filled in advance with a known culture solution. Algae to be grown are placed in the algae culture vessel 5 in advance.

[0042] When the algae to be cultured is Chlorella, the culture medium may be a urea culture medium or a nitrate culture medium (N-25, N-30, or N-50). When the algae to be cultured is Euglena, the culture medium may be a CM medium or a KH medium. To such a known culture medium, 1 to 30% by mass, preferably 5 to 10% by mass, of a carbon dioxide-rich absorbing solution 4 is mixed as a nitrogen source. Furthermore, when the carbon dioxide-rich absorbing solution 4 is decomposed by the action of microorganisms in the algae culture vessel 5, carbon dioxide is appropriately released into the culture medium. Therefore, the algae to be cultured can use this carbon dioxide as a carbon source when growing by photosynthesis. When a 5-aminolevulinic acid aqueous solution is used as the carbon dioxide-rich absorbing solution 4, the 5-aminolevulinic acid can be absorbed by the algae together with carbon dioxide before decomposition.

[0043] The carbon dioxide-rich absorbing solution 4 can be supplied to the algae cultivator 5 intermittently at regular intervals, or at a constant rate. The culture solution mixed with the carbon dioxide-rich absorbing solution 4 becomes a modified culture solution enriched in nitrogen and carbon sources. When a 5-aminolevulinic acid aqueous solution is used as the carbon dioxide-rich absorbing solution 4, the carbon source is enriched and the culture solution promotes algae growth. The carbon dioxide-rich absorbing solution 4 is mixed uniformly with the original culture solution by the action of the waterwheel mechanism 32. Algae are efficiently grown and cultivated in the modified culture solution enriched in nitrogen and carbon sources through photosynthesis. The grown and cultivated algae are recovered by an algae recovery device 6, consisting of a power shovel or pump, and used for various purposes. The recovered algae can be extracted, for example, as liquid fuel or to extract active ingredients as supplements. The extracted residue can be used as biomass fuel in thermal power plants or as livestock feed.

[0044] When the culture medium is reduced, an appropriately modified culture medium can be added to replenish it. That is, a modified culture medium can be prepared by mixing, for example, 1 to 30 mass %, preferably 5 to 10 mass %, of the carbon dioxide-rich absorption liquid 4 as a nitrogen source and a carbon source with the culture medium (urea culture medium, nitrate culture medium, CM medium, KH medium, or other medium), and this mixture can be replenished to the algae culture vessel 5.

[0045] According to the first embodiment, the following can be said: A carbon dioxide algae cultivation system 10 includes a carbon dioxide supply source 1 that supplies a carbon dioxide-containing gas, a carbon dioxide recovery unit 2 that brings the carbon dioxide-containing gas into contact with a carbon dioxide-lean absorption solution 3 to obtain a carbon dioxide-rich absorption solution 4, and an algae cultivator 5 that is provided adjacent to the carbon dioxide supply source 1 and the carbon dioxide recovery unit 2 and receives the carbon dioxide-rich absorption solution 4 from the carbon dioxide recovery unit 2 as a nutrient source, and is capable of cultivating algae.

[0046] The algae cultivation method includes supplying a carbon dioxide-containing gas from a carbon dioxide source 1, contacting the carbon dioxide-containing gas with a carbon dioxide-lean absorption liquid 3 in a carbon dioxide recovery unit 2 to obtain a carbon dioxide-rich absorption liquid 4, supplying the carbon dioxide-rich absorption liquid 4 from the carbon dioxide recovery unit 2 to an algae culture vessel 5 as a nutrient source, and cultivating algae in the algae culture vessel 5.

[0047] According to these configurations, carbon dioxide from the carbon dioxide supply source 1 can be absorbed into the carbon dioxide-lean absorbing solution 3 to obtain a carbon dioxide-rich absorbing solution 4. Furthermore, the carbon dioxide-rich absorbing solution 4 can be used as is as part of the algae culture solution (nitrogen source) without desorbing carbon dioxide from it. This makes it possible to eliminate the energy required for the heat treatment required to desorb carbon dioxide from the carbon dioxide-rich absorbing solution 4. As a result, it is possible to efficiently cultivate large amounts of algae at low cost.

[0048] In this case, the carbon dioxide lean absorbing solution 3 and the carbon dioxide rich absorbing solution 4 are absorbing solutions containing an absorbent, and the absorbent is ammonia or an amine compound.

[0049] According to this configuration, carbon dioxide can be efficiently recovered from the carbon dioxide supply source by the ammonia or amine compound, thereby enabling efficient algae cultivation.

[0050] In this case, the absorbent is ammonia or an organic amine compound. According to this configuration, carbon dioxide can be efficiently recovered from the carbon dioxide supply source by the ammonia or the organic amine compound, thereby enabling efficient algae cultivation.

[0051] In this case, an algae collection device 6 is provided to collect the algae cultured in the algae culture vessel 5. According to this configuration, the algae collection device 6 can efficiently collect and utilize the algae that have grown in the algae culture vessel 5.

[0052] In this case, the algae are algae capable of photosynthesis. According to this configuration, the carbon dioxide contained in the carbon dioxide-rich absorbing solution 4 is appropriately released when the carbon dioxide-rich absorbing solution 4 is decomposed by the action of microorganisms present in nature in the algae culture vessel 5. Therefore, the algae can grow by using this carbon dioxide as a carbon source when performing photosynthesis. As described above, it is possible to culture a large amount of algae efficiently at low cost.

[0053] In the following embodiment, differences from the first embodiment will be mainly described, and illustrations or descriptions of parts common to the first embodiment will be omitted. [Second embodiment]

[0054] An algae culture system 10 of this embodiment will be described with reference to Figure 4. In this embodiment, the configuration of the algae culture vessel 5 is different from that of the first embodiment, but other parts are common to the first embodiment. Therefore, the algae culture vessel 5 will be mainly described.

[0055] The algae cultivator 5 of this embodiment may be provided adjacent to the carbon dioxide supply source 1 and the carbon dioxide capture unit 2. Alternatively, if space cannot be secured adjacent to the carbon dioxide supply source 1 and the carbon dioxide capture unit 2, the algae cultivator 5 may be provided at a location physically separated from them. In this case, the carbon dioxide-rich absorbing liquid 4 can be transported from the carbon dioxide capture unit 2 to the algae cultivator 5 by an appropriate transportation means, such as a vehicle such as a tanker truck or a ship such as a tanker. Alternatively, the carbon dioxide-rich absorbing liquid 4 may be supplied from the carbon dioxide capture unit 2 to the algae cultivator 5 via a pipeline or the like. The algae cultivator 5 is preferably provided in a sunny location so that the algae to be grown can efficiently photosynthesize. Furthermore, the algae cultivator 5 is preferably provided in a relatively warm climate throughout the year.

[0056] The algae cultivator 5 is a closed culture system isolated from the outside world. The algae cultivator 5 includes a processing unit 51 connected to the second storage unit 15a of the carbon dioxide capture unit, a filter unit 52 that filters the liquid processed by the processing unit 51 to a sterile state, a tank 53 that receives the liquid filtered by the filter unit 52 and stores the algae culture solution and algae, a pipe unit 54 that extends from the tank 53 and is formed into a cylindrical shape from a translucent plastic material, a plurality of supports 55 that support the pipe unit 54, and a pump 56 that is provided midway along the pipe unit 54. The pump 56 may be located anywhere within the pipe unit 54 as long as it can circulate the culture solution and the algae to be cultured.

[0057] The treatment unit 51 is formed in the shape of a sealed tank and stores water in which an aquatic microbial ecosystem, such as nitrifying bacteria (ammonia-oxidizing bacteria, nitrite-oxidizing bacteria) and Bacillus bacteria, has been established. The water in which an aquatic microbial ecosystem has been established can be prepared, for example, by adding soil and organic matter (bonito broth or corn soaking liquid) to water and leaving it for 2 to 4 weeks while aerating it. The treatment unit 51 can appropriately decompose ammonia or amine compounds in the carbon dioxide-rich absorbing liquid 4 supplied from the second storage unit 15a. That is, when an aqueous ammonia solution is used as the carbon dioxide-rich absorbing liquid 4, the ammonia is nitrified by the nitrifying bacteria into nitrite and then nitrate. During this decomposition of ammonia, carbon dioxide is released from the carbon dioxide-rich absorbing liquid. While some of the carbon dioxide is released into the air in the tank 53, the majority remains dissolved in the liquid.

[0058] When an aqueous solution of any amine compound is used as the carbon dioxide-rich absorbing liquid 4, it is appropriately decomposed by Bacillus bacteria, and carbon dioxide is released from the carbon dioxide-rich absorbing liquid during the decomposition. The decomposition products of nitrates and amine compounds are absorbed by the algae to be cultured as a nitrogen source (nutrient). The provision of the processing unit 51 and the filter unit 52 is optional. For example, when an aqueous solution of 5-aminolevulinic acid is used as the carbon dioxide-rich absorbing liquid 4, the carbon dioxide-rich absorbing liquid 4 is not harmful to the algae and actually has the effect of promoting their growth, so the carbon dioxide-rich absorbing liquid 4 can be supplied directly to the tank 53 without passing through the processing unit 51.

[0059] The filter section 52 includes a bacterial filter and can remove microorganisms, bacteria, etc. from the liquid. A cellulose ester membrane with micropores of 0.2 mm or less can be suitably used as the bacterial filter. To prevent clogging of the bacterial filter, multiple auxiliary filters with coarser meshes than the bacterial filter may be provided upstream of the bacterial filter.

[0060] The pipe section 54 is formed as a long, single pipe line by alternating straight and curved sections. The pipe section 54 is formed to be transparent. By passing the culture solution and the algae to be cultured inside the pipe section 54, the algae to be cultured can photosynthesize inside the pipe section 54, allowing the algae to grow and be cultured.

[0061] The support pole 55 rests on the ground 57 , but the lower part of the support pole 55 may be buried in the ground 57 .

[0062] Next, the operation of the algae culture system 10 of this embodiment will be described. The carbon dioxide-rich absorbing liquid 4 is produced in the same manner as in the first embodiment. The carbon dioxide-rich absorbing liquid 4 stored in the second storage section 15a of the carbon dioxide capture unit 2 is mixed with water in a treatment section 51 in which an aquatic microbial ecosystem, such as nitrifying bacteria (ammonia-oxidizing bacteria, nitrite-oxidizing bacteria) and Bacillus bacteria, has been established. When the mixture of the carbon dioxide-rich absorbing liquid 4 and the water in the treatment section 51 is left in the treatment section 51 for several days to several weeks, the carbon dioxide-rich absorbing liquid 4 is decomposed by the action of the bacteria in the aquatic microbial ecosystem. When the carbon dioxide-rich absorbing liquid 4 is composed of an aqueous solution of ammonia, it is nitrified to nitrite and then to nitrate by the action of nitrifying bacteria (ammonia-oxidizing bacteria, nitrite-oxidizing bacteria) and the like. When the carbon dioxide-rich absorbing liquid 4 is composed of an aqueous solution of an amine compound, it is appropriately decomposed by the action of Bacillus bacteria and the like. When the carbon dioxide-rich absorbing liquid 4 is decomposed, the carbon dioxide held in the carbon dioxide-rich absorbing liquid is appropriately released into the liquid.

[0063] The liquid treated in the treatment unit 51 is supplied to the filter unit 52 and filtered. The nitrifying bacteria, Bacillus bacteria, and other bacteria are removed in the filter unit 52. When an aqueous ammonia solution is used as the carbon dioxide-rich absorption liquid 4, the nitrates (nitrate ions) and carbon dioxide in the liquid are supplied to the tank 53 together with the filtrate.

[0064] When an aqueous solution of any amine compound is used as the carbon dioxide-rich absorbing liquid 4, the amine decomposition product and carbon dioxide in the liquid are supplied together with the filtrate to the tank 53. When an aqueous solution of 5-aminolevulinic acid is used as the carbon dioxide-rich absorbing liquid 4, the liquid is supplied directly to the tank 53 without passing through the processing unit 51 and the filter unit 52. The carbon dioxide-rich absorbing liquid 4 (decomposition-treated liquid of the carbon dioxide-rich absorbing liquid 4) may be supplied to the tank 53 constantly, or may be supplied to the tank 53 intermittently at predetermined time intervals.

[0065] The algae to be cultured are placed in advance in tank 53, and an algae culture solution is stored therein. When the algae to be cultured is Chlorella, the culture solution may be a known urea culture solution or a known nitrate culture solution (N-25, N-30, N-50). When the algae to be cultured is Euglena, the culture solution may be a known CM medium or KH medium.

[0066] In this way, 1 to 30 mass %, preferably 5 to 10 mass %, of the carbon dioxide-rich absorbing solution 4 is mixed with the culture solution containing the algae to be cultured to prepare the modified culture solution in the tank 53. More specifically, this carbon dioxide-rich absorbing solution 4 is a filtrate that has been decomposed in the processing unit 51 and filtered in the filter unit 52.

[0067] A mixture of the culture solution containing the algae to be cultured and the carbon dioxide-rich absorption solution 4 is sent into the pipe section 54 by driving the pump 56. When sunlight is irradiated onto the pipe section 54, the algae in the pipe section 54 undergo photosynthesis and grow. During this process, nitrates (nitrate ions) are absorbed by the algae as a nitrogen source. Amine decomposition products are also absorbed by the algae as a nitrogen source. Carbon dioxide is also absorbed by the algae as a carbon source. 5-aminolevulinic acid is absorbed as is by the algae, promoting their growth.

[0068] This mixture is circulated through the pipe 54, and after a predetermined period of time has passed and the algae have grown sufficiently, the algae are collected together with the culture solution. An algae collection device (not shown) can be used for this purpose. One example of an algae collection device is a filter device (filter) that can pick up algae from the culture solution.

[0069] The collected algae can be used for various purposes, such as extracting liquid fuel or extracting active ingredients to produce supplements, and the extracted residue can be used as biomass fuel in thermal power plants or as livestock feed.

[0070] When the culture solution decreases, the culture solution modified as described above can be added as needed to replenish it. That is, the modified culture solution is prepared by mixing, for example, 1 to 30 mass %, preferably 5 to 10 mass %, of the carbon dioxide-rich absorbing solution 4 with the culture solution (urea culture solution, nitrate culture solution, CM medium, KH medium, or other medium) or by decomposing the carbon dioxide-rich absorbing solution 4 in a processing unit 51 and filtering it in a filter unit 52. The modified culture solution can be replenished to the tank 53.

[0071] The above-described embodiment can be implemented with various substitutions and modifications. [Explanation of symbols]

[0072] 1. Carbon dioxide source 2 Carbon dioxide capture section 3. Carbon dioxide lean absorbent 4. Carbon dioxide-rich absorbent 5 Algae incubator 6. Algae collection device 10 Algae cultivation system

Claims

1. a carbon dioxide source that supplies a carbon dioxide-containing gas; a carbon dioxide recovery unit that contacts the carbon dioxide-containing gas with a carbon dioxide-lean absorption liquid to obtain a carbon dioxide-rich absorption liquid; an algae cultivator capable of cultivating algae by receiving the carbon dioxide-rich absorption solution from the carbon dioxide recovery unit as a nutrient source; Equipped with The carbon dioxide lean absorption liquid and the carbon dioxide rich absorption liquid are absorption liquids containing an absorbent, The algae cultivation system, wherein the absorbent is ammonia or an amine-based compound.

2. The algae culture system according to claim 1 , wherein the absorbent is ammonia or an organic amine compound.

3. The algae culture system according to claim 1 or 2, further comprising an algae recovery device that recovers the algae cultured in the algae culture vessel.

4. The algae culture system according to any one of claims 1 to 3, wherein the algae are photosynthetic algae.

5. providing a carbon dioxide-containing gas via a carbon dioxide source; a carbon dioxide-rich absorption liquid is obtained by contacting the carbon dioxide-containing gas with a carbon dioxide-lean absorption liquid in a carbon dioxide recovery section; An algae culture method for supplying the carbon dioxide-rich absorption liquid from the carbon dioxide recovery unit to an algae culture vessel as a nutrient source and cultivating algae in the algae culture vessel, The carbon dioxide lean absorption liquid and the carbon dioxide rich absorption liquid are absorption liquids containing an absorbent, The method for cultivating algae, wherein the absorbent is ammonia or an amine compound.

6. The method for cultivating algae according to claim 5 , wherein the absorbent is ammonia or an organic amine compound.

7. 7. The method for cultivating algae according to claim 5, wherein the algae are capable of photosynthesis.

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