Methods for preparing culture fluid for microalgae using wastes and methods for culturing microalgae using the culture fluid

Abstract

To provide a method of making a culture fluid for microalgae.SOLUTION: The disclosed method for preparing a culture fluid for microalgae comprises: a step of oxidizing NO in NOx-containing discharged gas from a cement manufacturing equipment to NO2 with an oxidant, then contacting the NO2-containing waste gas with water to dissolve the NO2 into the water to obtain a nitrate nitrogen-containing solution; a step of washing desalted dust discharged from the cement manufacturing equipment with water, where the desalted dust contains phosphorus and / or potassium, to obtain washing water used for washing desalted dust containing phosphorus and / or potassium, adding a pH adjustor to the washing water to separate precipitates from an aqueous solution containing phosphorus and / or potassium of which adjusted pH is from 8 to 10; a step of mixing the aqueous solution containing phosphorus and / or potassium (pH8 to pH10) and the nitrate-nitrogen containing solution of the former step, and adjusting the pH of the mixture to from 5 to 8, thereby preparing a culture fluid containing nitrogen, phosphorus and / or potassium for microalgal culture.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing a culture solution of microalgae using waste and a method for culturing algae using the culture solution. In particular, the present invention relates to a method for producing a culture solution of microalgae that effectively uses waste such as exhaust gas and desalination dust generated in the cement manufacturing process and the like as a nutrient source for microalgae, and a method for culturing microalgae using the culture solution.

Background Art

[0002] Generally, in the cement manufacturing process and the like, the exhaust gas generated by burning coal, heavy oil, and recycled fuel is used for drying cement raw materials, and then the collected dust contained therein is recovered in the dust collection process and discharged outside the system. In the exhaust gas discharged outside the system, in addition to carbon dioxide and trace amounts of chlorides, nitrogen oxides (hereinafter referred to as "NOx") generated by fuel combustion and the like are also contained in large amounts. NOx causes environmental burdens such as acid rain and has an adverse effect on the human body such as the respiratory system, and is one of the causes of environmental problems.

[0003] In view of such problems, in cement factories and the like, efforts are being made to reduce the NOx emission amount by selecting fuels with less nitrogen content and regulating NOx emissions using denitration agents. In addition, in view of global warming, it is required to reduce carbon dioxide emissions, and the realization of carbon neutrality is expected.

[0004] On the other hand, for algae to grow, nitrogen (N), phosphorus (P), potassium (K), carbon dioxide (CO 2 ) etc. are required as nutrients. The exhaust gas discharged from a cement factory contains nitrogen, which is an essential nutrient for the growth of plants including algae, and has the potential to be used as a nutrient source for microalgae. Furthermore, the exhaust gas discharged from the cement factory contains carbon dioxide. If this carbon dioxide can be utilized in the cultivation of algae, it will lead to the reduction of carbon dioxide and contribute to the realization of carbon neutrality. In addition, the realization of a circular economy that effectively utilizes the waste discharged in the cement manufacturing process is also expected.

[0005] However, approximately 90% of the nitrogen oxides in the exhaust gas discharged during the cement manufacturing process are nitric oxide (NO), which is insoluble in water, and only about 10% is nitrogen dioxide (NO 2 2), which is water-soluble. Therefore, even if the exhaust gas discharged during the cement manufacturing process is directly used for the cultivation of microalgae without being treated, it is difficult for the algae to take in nitrogen (N) as a nutrient, and it is not effective.

[0006] As a conventional method for cultivating microalgae, for example, Japanese Unexamined Patent Application Publication No. 2022-160029 (Patent Document 1) describes an algae cultivation method in which a carbon dioxide-containing gas is supplied by a carbon dioxide source, a carbon dioxide lean absorption liquid is brought into contact with the carbon dioxide-containing gas by a carbon dioxide recovery unit to obtain a carbon dioxide rich absorption liquid, the carbon dioxide rich absorption liquid is supplied from the carbon dioxide recovery unit to an algae culture solution as a nutrient source, and algae are cultivated in the algae cultivator.

[0007] In addition, Japanese Unexamined Patent Application Publication No. 2023-103646 (Patent Document 2) describes a method for cultivating microalgae using exhaust gas, which includes a separation and supply step of separating useful components from the exhaust gas and supplying the useful components to a culture solution, and a stirring step of using the exhaust gas after separating the useful components as a stirring power for the culture solution to stir the culture solution.

[0008] Furthermore, Japanese Patent Application Laid-Open No. 2023-47761 (Patent Document 3) discloses a method for culturing microalgae in a changing culture environment, the method comprising: a setting step of setting the nutritional mode of the microalgae according to the culture environment; and a culturing step of culturing the microalgae in the nutritional mode set in the setting step. When photoautotrophy is set in the setting step, in the culturing step, a gas containing carbon dioxide and light are supplied to the microalgae. When heterotrophy is set in the setting step, in the culturing step, an organic substance is supplied to the microalgae. A culturing method is described.

[0009] However, in these conventional microalgae culturing methods, the exhaust gas discharged from cement factories and the like is not fully utilized, and the waste from cement factories and the like is not effectively recycled. Thus, it is impossible to sufficiently reduce the environmental load, and it is not a culturing system that can effectively utilize multiple types of nutrient sources for culturing microalgae.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0011] An object of the present invention is to solve the above problems, contribute to environmental load reduction by effectively utilizing exhaust gas and waste such as desalination dust generated in cement factories and the like, and provide a plurality of nutrient sources derived from these wastes and the like as a culture solution for microalgae, thereby providing a method for producing a culture solution for microalgae.

[0012] Another object of the present invention is to provide a method for culturing microalgae, which can effectively culture microalgae using the culture solution of microalgae prepared by the above method of the present invention, and further utilize the waste heat from a cement factory or the like to prepare a dried product of the cultured microalgae.

Means for Solving the Problems

[0013] (1) The method for producing a culture solution of microalgae according to the present invention comprises blending an oxidizing agent with the exhaust gas containing NOx discharged from a cement manufacturing facility to oxidize NO in the NOx to NO 2 , and then bringing the exhaust gas containing NO 2 into contact with water to dissolve NO 2 in the exhaust gas in water to obtain a nitrate nitrogen-containing solution in step (1), washing the desalted dust containing phosphorus and / or potassium discharged from the cement manufacturing facility with water and separating it to obtain a desalted dust washing water containing phosphorus and / or potassium, blending a pH adjuster into the desalted dust washing water containing phosphorus and / or potassium, and separating it into a precipitate and an aqueous solution containing phosphorus and / or potassium adjusted to pH 8 to 10 in step (2), and blending the aqueous solution containing phosphorus and / or potassium adjusted to pH 8 to 10 obtained in step (2) into the nitrate nitrogen-containing solution obtained in step (1), adjusting the pH of the mixed solution of the aqueous solution containing phosphorus and / or potassium and the nitrate nitrogen-containing solution to 5 to 8, and preparing a culture solution of microalgae containing nitrogen, phosphorus and / or potassium in step (3). The method for producing a culture solution of microalgae using waste is characterized by comprising the above steps.

[0014] (2) Preferably, in the method for producing a culture solution of microalgae using waste according to the above (1), the oxidizing agent is oxygen or ozone. The method for producing a culture solution of microalgae using waste is characterized by this.

[0015] (3) More preferably, in the method for producing a culture solution of microalgae using waste according to the above (1) or (2), the exhaust gas further contains CO 2 , and by the above contact of the exhaust gas with water, CO 2 in the exhaust gas is also dissolved in water, and further CO 2A method for producing a culture solution of microalgae using waste, characterized by preparing a culture solution of microalgae in which waste has been dissolved.

[0016] (4) The method for culturing microalgae of the present invention uses nitrogen, phosphorus, and / or potassium in nitrate nitrogen in the culture solution of microalgae obtained by the method of (1) or (2) above as nutrients for culturing microalgae, centrifuges the culture solution containing the cultured microalgae, and dries the obtained microalgae using the waste heat from the cement manufacturing facility to obtain dried algal bodies. This is a method for culturing microalgae.

[0017] (5) Another method for culturing microalgae of the present invention uses nitrogen, phosphorus, and / or potassium in nitrate nitrogen in the culture solution of microalgae obtained by the method of (3) above as nutrients for microalgae, and uses CO 2 in the culture solution for the photosynthesis of microalgae, centrifuges the culture solution containing the cultured microalgae, and dries the obtained microalgae using the waste heat from the cement manufacturing facility to obtain dried algal bodies. This is a method for culturing microalgae.

Advantages of the Invention

[0018] The method for producing a culture solution of microalgae of the present invention can effectively utilize waste such as exhaust gas and desalinated dust generated in a cement factory or the like to produce a culture solution of microalgae containing multiple types of nutrient sources, and can also effectively utilize waste and the like. Therefore, it is possible to suppress the emission of nitrogen oxides into the atmosphere and reduce the environmental load by effectively using waste, contributing to the realization of a circular economy for exhaust gas and waste.

[0019] In addition, in the method for culturing microalgae of the present invention, since the culture solution produced by the method of the present invention can be effectively used for culturing microalgae, microalgae can utilize a plurality of types of nutrient sources necessary for culturing microalgae. Therefore, microalgae can be cultured efficiently. Moreover, since it is produced by effectively using waste such as exhaust gas and desalination dust generated in a cement factory or the like, the environmental load can be reduced, and it becomes possible to contribute to the realization of a circular economy for exhaust gas and waste. Further, by utilizing the waste heat from the cement manufacturing facility, it becomes possible to obtain a dried product of the cultured microalgae.

Brief Description of the Drawings

[0020]

Figure 1

Embodiments for Carrying Out the Invention

[0021] The present invention will be described by the following preferred embodiments with reference to FIG. 1, but it is not limited thereto.

[0022] In the method for producing a culture solution of microalgae of the present invention, an oxidizing agent is added to the exhaust gas containing NOx discharged from a cement manufacturing facility or the like, and NO in the NOx is oxidized to NO 2 , and then the exhaust gas containing NO 2 is brought into contact with water so that NO in the exhaust gas 2A process (1) of dissolving it in water to obtain a nitrate nitrogen-containing solution, a process (2) of separating the desalted dust containing phosphorus and / or potassium discharged from cement manufacturing equipment or the like by washing it with water and then adding a pH adjuster to the desalted dust washing water containing phosphorus and / or potassium thus obtained to separate it into a precipitate and an aqueous solution containing phosphorus and / or potassium adjusted to pH 8 to 10, and a process (3) of formulating the aqueous solution containing phosphorus and / or potassium adjusted to pH 8 to 10 obtained in the process (2) into the nitrate nitrogen-containing solution obtained in the process (1) and adjusting the pH of the mixed solution of the aqueous solution containing phosphorus and / or potassium and the nitrate nitrogen-containing solution to 5 to 8 to prepare a culture solution for microalgae containing nitrogen, phosphorus and / or potassium. This is a method for producing a culture solution for microalgae using waste materials.

[0023] Also, preferably, the exhaust gas further contains CO 2 which is contained, and by the contact of the exhaust gas with water, CO 2 in the exhaust gas is also dissolved in water to further prepare a culture solution for microalgae in which CO 2 is dissolved. This is a method for producing a culture solution for microalgae using waste materials.

[0024] Hereinafter, as an example, the use of exhaust gas, waste materials, etc. from cement manufacturing equipment will be described as an example. Generally, in a cement factory, when manufacturing cement, it goes through a raw material grinding process of grinding each raw material, a clinker firing process of firing the ground raw materials to produce cement clinker, and then a cement finishing process of grinding the cement clinker and mixing it with gypsum to produce cement.

[0025] To produce cement clinker, fuel is burned to set the firing temperature at about 1300 to 1500 °C, and the cement raw materials are fired in a cement kiln to produce cement clinker, and exhaust gas is discharged from the cement manufacturing equipment.

[0026] As shown in FIG. 1, the exhaust gas from the cement manufacturing equipment is not particularly limited as long as it is the exhaust gas discharged in the cement manufacturing process and can be used in the present invention. Examples of the exhaust gas include, for example, the exhaust gas discharged from firing cement raw materials in a cement kiln, the exhaust gas from burning fuel for maintaining the cement kiln at a high temperature, etc. These gases used in the present invention include dust such as cement dust and desalination dust, nitrogen oxides, CO 2 , etc. are included.

[0027] Preferably, the exhaust gas discharged from the cement kiln, for example, the exhaust gas discharged after adding a denitration agent in a preheater and performing denitration treatment can be used. Examples of the denitration agent include ammonia and urea. The denitration treatment is a treatment in which, for example, aqueous ammonia or aqueous urea is sprayed in a cement firing furnace and brought into contact with NO to reduce NO. The reaction is represented by the following formula. Urea CO(NH 2 ) 2 +H 2 O → 2NH 3 +CO 2 4NO + 4NH 3 +O 2 → 4N 2 + 6H 2 O Ammonia 4NO + 4NH 3 +O 2 → 4N 2 + 6H 2 O

[0028] In addition, the method of the present invention can be applied not only to the exhaust gas from a cement factory but also to the exhaust gas from a woody biomass power plant, a coal-fired power plant, a waste incineration plant, and an ironworks.

[0029] The exhaust gas from the cement manufacturing facility, for example, the combustion gas contains various dusts as described above. The dust in the exhaust gas is collected, for example, by an electrostatic precipitator, separated into dust and exhaust gas, and the separated exhaust gas is cooled, for example, cooled to about 40°C while indirectly recovering heat using a heat exchanger.

[0030] In the cooled exhaust gas, there are carbon dioxide and nitrogen oxides (NOx) such as nitrogen monoxide (NO) and nitrogen dioxide (NO 2 2 ). However, since NO does not dissolve in water, as it is, it is not possible to supply nitrogen (N) as a nutrient source for microalgae.

[0031] Therefore, in the method of the present invention, the exhaust gas containing the above NOx after dust separation is brought into contact with an oxidizing agent to oxidize NO in the exhaust gas to NO 2 2 Examples of the oxidizing agent include oxidizing gases such as oxygen and ozone. Oxidation is carried out using at least one of these oxidizing agents, and the contact method is not particularly limited as long as NO in the exhaust gas can be oxidized to NO 2 2 2 2 In this way, NOx contained in the exhaust gas is oxidized to NO 2 2

[0032] Next, the exhaust gas in which NO in the exhaust gas is oxidized to NO 2 2 2 2 The above step (1) of preparing the nitric acid nitrogen-containing solution is a step that utilizes a NOx absorption process with water.

[0033] Specifically, since NO 2 2 2 2 2 2 2 2As the water that comes into contact with the exhaust gas containing [it], industrial water, seawater, artificial seawater, etc. can be used according to the growth environment of algae. For example, into the water, the above exhaust gas in which NO is oxidized to NO 2 is blown in and aerated, and by reacting NO 2 with water, or by indirectly recovering heat using a heat exchanger and reacting NO 2 with water, a nitrate nitrogen-containing liquid can be obtained.

[0034] The oxidation of NOx by ozone in the exhaust gas from cement manufacturing facilities is represented by the following equation. NO + O 3 → NO 2 + O 2 2NO 2 + O 3 → N 2 O 5 + O 2 2NO + O 2 → 2NO 2 Also, as shown in the following reaction formula, when NO 2 comes into contact with water, for example, nitrate nitrogen is generated. 2NO 2 + H 2 O + 1 / 3O 3 → 2HNO 3 N 2 O 5 + H 2 O → 2HNO 3

[0035] The volume ratio of (HNO 3 / containing liquid) in the obtained nitrate nitrogen-containing liquid is not particularly limited, but for example, 0.01 to 0.15, preferably 0.01 to 0.08 can be exemplified. The preparation step (1) of the nitrate nitrogen-containing liquid is, as described above, NO 2Water is used as the dissolution liquid, and chemical solutions such as chemicals are not used, so the cost can be kept low. In addition, it is recovered as a nitric acid nitrogen-containing liquid and can be used for the culture solution of microalgae. Therefore, nitric acid nitrogen can be used as a nutrient source for microalgae, and the contained nitrogen can be effectively used for culturing microalgae.

[0036] Also, as described above, the exhaust gas separated from the dust, for example, the exhaust gas from the cement incinerator, contains carbon dioxide in addition to nitrogen oxides. Generally, it contains about 10 to 30% by volume of carbon dioxide. NO in the above exhaust gas is oxidized to NO 2 After that, the exhaust gas is brought into contact with water to prepare a nitric acid nitrogen-containing liquid. At this time, CO 2 contained in the exhaust gas also comes into contact with the water, so that the CO 2 can also be dissolved in the water, and carbon dioxide can be included in the nitric acid nitrogen-containing liquid. Thereby, carbon dioxide can be contained in the obtained culture solution, and the carbon dioxide can be effectively used for photosynthesis when culturing microalgae.

[0037] Also, the dust separated from the exhaust gas discharged from the cement manufacturing facility, for example, desalted dust, is washed with water. As the water to be used, industrial water, seawater, artificial seawater, etc. can be used depending on the growth environment of the algae.

[0038] As the fuel for manufacturing cement, from the viewpoint of effective utilization of waste, waste such as household waste, sewage sludge, waste acid / waste alkali, waste plastic, dried sludge, waste clay, wood chips, recycled oil, ASR, PKS, etc. are used, and the waste is burned, and the obtained heat source is used as the heat source for the cement clinker firing process. Also, as cement raw materials, nitrogen-containing wastes such as coal ash, general incineration ash, construction-generated soil, burned shells, sludge, foundry sand, steelmaking dust, slowly cooled slag, etc. may be used as raw materials.

[0039] Many of these fuels and raw materials contain phosphorus and potassium. Since the dust discharged from cement manufacturing facilities, such as desalination dust, contains phosphorus and / or potassium derived from these raw materials and fuels, phosphorus and / or potassium will dissolve in the washing water obtained by washing the dust with water, resulting in an aqueous solution containing phosphorus and / or potassium. After washing the dust with the washing water, it is separated into the aqueous solution containing phosphorus and / or potassium and the precipitate. The separated precipitate can be reused by blending it with the raw materials of the cement factory, etc.

[0040] Furthermore, the dust may contain heavy metals. In the washing water obtained by washing the dust, heavy metals may also dissolve and be contained in addition to phosphorus and / or potassium. In this case, it is necessary to remove the heavy metals dissolved in the aqueous solution. Or, for dust such as desalination dust that does not contain heavy metals, since the washing water obtained by washing the dust does not contain heavy metals, it can be directly added to the culture solution together with the above-mentioned nitrate nitrogen-containing solution as the phosphorus and / or potassium-containing washing water serving as a phosphorus and / or potassium source.

[0041] When heavy metals are contained in the washing water, in order to separate the heavy metals from phosphorus and / or potassium, a pH adjuster is added to the washing water so that the pH of the aqueous solution becomes in the alkaline range, and the dissolved heavy metals are precipitated as a precipitate and separated.

[0042] Examples of the pH adjuster include sodium hydroxide, potassium hydroxide, calcium hydroxide, hydrochloric acid, sulfuric acid, etc. By adjusting the pH of the washing water to about pH 8 to 10, preferably pH 8.5 to 9.5, which is in the alkaline range, the heavy metals contained in the washing water are precipitated, for example, precipitated as hydroxides of heavy metals, and separated by known separation means to obtain an aqueous solution in which phosphorus and / or potassium are dissolved (step (2)).

[0043] The nitric nitrogen-containing solution obtained in the above step (1) in which carbon dioxide is also dissolved has an acidic pH range and cannot be used as a culture solution for microalgae as it is. Therefore, the phosphorus and / or potassium dissolved aqueous solution with a pH adjusted to about 8 to 10 obtained in the above step (2) is blended into the nitric nitrogen-containing solution obtained in the above step (1) in which carbon dioxide is also dissolved, and the pH of the resulting mixed solution is adjusted to the neutral range, for example, pH 5 to 8, preferably pH 6 to 7.5 (step (3)).

[0044] Specifically, in order to make the pH of the culture solution of microalgae that grows in the neutral range (pH 5 to 8) the above neutral range, for example, the phosphorus and / or potassium dissolved aqueous solution with a pH adjusted to about 8 to 10 obtained in step (2) is blended into the acidic nitric nitrogen-containing solution obtained in step (1) to prepare the above neutral range mixed solution, and a culture solution for microalgae can be manufactured for use as a pH adjuster for the microalgae culture solution and a nutrient source. Or, when it does not contain heavy metals or contains only trace amounts even if it contains them, since the washing water obtained by washing dust such as desalted dust hardly contains heavy metals, when the washing water containing phosphorus and / or potassium is directly introduced together with the nitric nitrogen-containing solution obtained in step (1) to prepare the culture solution, it is also possible to adjust the pH of the culture solution to the above pH in the neutral range by adding a pH adjuster as necessary. Here, as the pH adjuster, it is possible to use the above pH adjuster.

[0045] Using the culture solution of microalgae obtained by the method of the present invention thus obtained, microalgae are cultured. The culture solution obtained by the method of the present invention contains a nutrient source for microalgae, nitrogen, phosphorus and / or potassium necessary for photosynthesis, and carbon dioxide. By using the culture solution for culturing microalgae, microalgae can effectively utilize the nitrogen, phosphorus and / or potassium, and carbon dioxide contained in the culture solution, and the microalgae can be cultured and grown efficiently.

[0046] The microalgae that can be cultured by applying the culture solution produced according to the present invention are not particularly limited, and can be used for any freshwater or seawater microalgae. For example, cyanobacteria, red algae, green algae, grey algae, diatoms, brown algae, euglenoids, etc. can be exemplified. In particular, it can be effectively used for the culture of Chlorella, Euglena, Spirulina, Nannochloropsis, Chlamydomonas, etc.

[0047] The microalgae cultured in this way are separated into a liquid component and microalgae by means such as a centrifuge using the culture solution containing the cultured microalgae. The separated microalgae can be dried by using waste heat such as exhaust heat from a cement factory or the like, and thus dried microalgae can be obtained. The exhaust heat gas is adjusted to less than 300 °C by, for example, a heat exchanger and then used. Different from the exhaust gas in the above step (1), in the cement manufacturing process, it means hot gas such as air that is warmed outside the cement kiln and does not contain cement dust or the like.

[0048] In this way, the method for producing and culturing the culture solution of microalgae of the present invention can effectively utilize waste such as exhaust gas and desalination dust discharged from a cement factory or the like, and can be used as a culture solution that can supply nitrogen, phosphorus and / or potassium, which are nutrient sources necessary for culturing microalgae, and carbon dioxide to the microalgae for culturing. At the same time, by using exhaust gas and waste, the environmental load can be reduced, waste can be recycled, and it can also contribute to the reduction of the environmental load.

Industrial Applicability

[0049] It becomes possible to produce a culture solution containing nutrient sources that can be effectively used for culturing microalgae by using waste such as exhaust gas and desalination dust discharged from a cement factory or the like, and the environmental load can be reduced. Therefore, the method for producing the culture solution of the present invention can be effectively applied in a cement factory or the like that manufactures cement, and in the industry that cultures microalgae, it can be applied to effectively culture microalgae by using the culture solution produced according to the present invention.

Claims

1. An oxidizing agent is added to the exhaust gas containing NOx discharged from the cement manufacturing facility to oxidize NO in the NOx to NO ２ and then the exhaust gas containing NO ２ is brought into contact with water to dissolve NO ２ in the exhaust gas in water to obtain a nitric acid nitrogen-containing liquid (Step 1). The desalted dust washing water containing phosphorus and / or potassium obtained by washing and separating the desalted dust containing phosphorus and / or potassium discharged from the cement manufacturing facility with water is mixed with a pH adjuster to separate it into a precipitate and an aqueous solution containing phosphorus and / or potassium adjusted to pH 8 to 10 (Step 2). The aqueous solution containing phosphorus and / or potassium adjusted to pH 8 to 10 obtained in Step (2) is mixed with the nitric acid nitrogen-containing liquid obtained in Step (1), and the pH of the mixed liquid of the aqueous solution containing phosphorus and / or potassium and the nitric acid nitrogen-containing liquid is adjusted to 5 to 8 to prepare a culture solution for microalgae containing nitrogen, phosphorus and / or potassium (Step 3). A method for producing a culture solution for microalgae using waste, characterized by comprising the above steps.

2. In the method for producing a culture solution of microalgae using waste according to Claim 1, the oxidizing agent is oxygen or ozone. A method for producing a culture solution of microalgae using waste, characterized by this.

3. In the method for producing a culture solution of microalgae using the waste according to claim 1 or 2, the exhaust gas further contains CO ２ and by the contact of the exhaust gas with water, CO ２ in the exhaust gas is also dissolved in water to prepare a culture solution of microalgae in which further CO ２ is dissolved. A method for producing a culture solution of microalgae using waste, characterized by this.

4. Nitrogen, phosphorus, and / or potassium of nitrate nitrogen in the culture solution of microalgae obtained by the method according to Claim 1 or 2 are used for culturing microalgae as nutrients for microalgae, and the culture solution containing the cultured microalgae is centrifuged. A method for culturing microalgae, characterized in that the obtained microalgae are dried using waste heat from cement manufacturing equipment to obtain dried algal bodies.

5. Using nitrogen, phosphorus and / or potassium of nitrate nitrogen in the culture solution of microalgae obtained by the method according to claim 3 as nutrients for the microalgae, and using CO ２ in the culture solution for the photosynthesis of the microalgae, centrifuging the culture solution containing the cultured microalgae, and drying the obtained microalgae using the waste heat from the cement manufacturing facility to obtain dried algal bodies. A method for culturing microalgae, characterized by this.

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