Method for producing culture solution of microalgae using waste and method for culturing microalgae using the culture solution

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 the cement raw material, 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 have been made to reduce the NOx emission amount by selecting fuels with less nitrogen components and regulating NOx emissions using denitration agents. 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 (CO2), etc. are required as nutrients. The exhaust gas discharged from the 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 a cement factory also 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 (NO2), 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 treatment, it is difficult for algae to take in nitrogen (N) as a nutrient, and it is not effective.

[0006] As a conventional method for culturing microalgae, for example, Japanese Patent Application Laid-Open No. 2022-160029 (Patent Document 1) describes an algae culture 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 cultured in the algae culture device.

[0007] In addition, Japanese Patent Application Laid-Open No. 2023-103646 (Patent Document 2) describes a method for culturing microalgae using exhaust gas as an algae culture method, 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, which is a culturing method for culturing microalgae in a changing culturing environment. The method includes a setting step of setting the nutritional mode of the microalgae according to the culturing 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, so sufficient reduction of the environmental load cannot be achieved, and it is not a culturing system that can effectively utilize multiple types of nutrient sources for microalgae culturing. and Moreover, it is not a culturing system that can effectively utilize multiple types of nutrient sources for microalgae culturing.

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, effectively utilize waste such as exhaust gas and desalination dust generated in cement factories and the like, contribute to reducing the environmental load, and provide a plurality of nutrient sources derived from these wastes and the like as a culture solution for microalgae. It is to provide a method for producing a culture solution for microalgae.

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

Means for Solving the Problems

[0013] (1) The method for producing a culture solution of microalgae according to the present invention comprises a step (1) of blending an oxidizing agent with the exhaust gas containing NOx discharged from a cement manufacturing facility to oxidize NO in the NOx to NO2, and then bringing the exhaust gas containing NO2 into contact with water to dissolve NO2 in the exhaust gas in water to obtain a nitrate nitrogen-containing solution, a step (2) of blending a pH adjusting agent with 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, and separating it into a precipitate and an aqueous solution containing phosphorus and / or potassium adjusted to pH 8 to 10, and a step (3) of blending the aqueous solution containing phosphorus and / or potassium adjusted to pH 8 to 10 obtained in the step (2) with the nitrate nitrogen-containing solution obtained in the step (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 of microalgae containing nitrogen, phosphorus and / or potassium. It is a method for producing a culture solution of microalgae using waste.

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

[0015] (3) More preferably, in the method for producing a culture solution of microalgae using waste according to (1) or (2) above, the exhaust gas further contains CO2, and by the contact of the exhaust gas with water, CO2 in the exhaust gas is also dissolved in water to prepare a culture solution of microalgae in which CO2 is further dissolved. It is a method for producing a culture solution of microalgae using waste.

[0016] (4) The method for culturing microalgae of the present invention uses nitrogen, phosphorus, and / or potassium of 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. It is a method for culturing microalgae, characterized in that.

[0017] (5) Another method for culturing microalgae of the present invention uses nitrogen, phosphorus, and / or potassium of nitrate nitrogen in the culture solution of microalgae obtained by the method of (3) above as nutrients for microalgae, uses CO2 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. It is a method for culturing microalgae, characterized in that.

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 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 utilizing waste, and it is possible to contribute to the realization of a circular economy for exhaust gas and waste.

[0019] In addition, the method for culturing microalgae of the present invention can effectively use the culture solution produced by the method of the present invention for culturing microalgae, so that microalgae can utilize multiple types of nutrient sources necessary for culturing microalgae. Therefore, microalgae can be cultured efficiently, and since it is produced by effectively utilizing waste such as exhaust gas and desalinated dust generated in a cement factory or the like, the environmental load can be reduced, and it is possible to contribute to the realization of a circular economy for exhaust gas and waste. Also, by using the waste heat from the cement manufacturing facility, it is possible to obtain dried bodies 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 below with reference to FIG. 1 according to the following preferred embodiments, but is not limited thereto.

[0022] The method for producing a culture solution of microalgae according to the present invention comprises a step (1) of blending an oxidizing agent with exhaust gas containing NOx discharged from cement manufacturing facilities or the like to oxidize NO in the NOx to NO2, and then bringing the exhaust gas containing NO2 into contact with water to dissolve NO2 in the exhaust gas in water to obtain a nitric acid nitrogen-containing solution; a step (2) of blending a pH adjusting agent into 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 cement manufacturing facilities or the like with water, and separating it into a precipitate and an aqueous solution containing phosphorus and / or potassium adjusted to pH 8 to 10; and a step (3) of blending the aqueous solution containing phosphorus and / or potassium adjusted to pH 8 to 10 obtained in the step (2) into the nitric acid nitrogen-containing solution obtained in the step (1), adjusting the pH of the mixed solution of the aqueous solution containing phosphorus and / or potassium and the nitric acid nitrogen-containing solution to 5 to 8, and preparing a culture solution of microalgae containing nitrogen, phosphorus and / or potassium. It is a method for producing a culture solution of microalgae using waste.

[0023] Also, preferably, the exhaust gas further contains CO2, and by the contact of the exhaust gas with water, CO2 in the exhaust gas is also dissolved in water to prepare a culture solution of microalgae in which CO2 is further dissolved. It is a method for producing a culture solution of microalgae using waste.

[0024] Hereinafter, as an example, the use of exhaust gas and waste from cement manufacturing facilities will be described as an example. Generally, in a cement factory, in manufacturing cement, there are a raw material pulverization process for pulverizing each raw material, a clinker firing process for firing the pulverized raw materials to produce cement clinker, and then a cement finishing process for pulverizing the cement clinker and mixing it with gypsum to produce cement through these processes.

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

[0026] As shown in FIG. 1, the exhaust gas from the cement manufacturing facility is not particularly limited as long as it is exhaust gas discharged in the cement manufacturing process and can be used in the present invention. Examples of the exhaust gas include, for example, exhaust gas discharged by firing cement raw materials in a cement kiln, exhaust gas from burning fuel to keep the cement kiln at a high temperature, etc. These gases used in the present invention contain dust such as cement dust and desalination dust, nitrogen oxides, CO2, etc.

[0027] Preferably, exhaust gas discharged from the cement kiln and, for example, exhaust gas discharged after denitration treatment by adding a denitration agent in a preheater can be used. Examples of the denitration agent include ammonia and urea, etc. The denitration treatment is, for example, a treatment in which aqueous ammonia or aqueous urea is sprayed in a cement firing furnace and brought into contact with NO to reduce NO. The reaction is shown by the following formula. Urea CO(NH2)2 + H2O → 2NH3 + CO2 4NO + 4NH3 + O2 → 4N2 + 6H2O Ammonia 4NO + 4NH3 + O2 → 4N2 + 6H2O

[0028] In addition, the method of the present invention can be applied not only to exhaust gas from a cement factory but also to 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, such as combustion gas, contains various dusts as described above. The dust in the exhaust gas is collected by, for example, an electrostatic precipitator and separated into dust and exhaust gas. It is desirable to cool the separated exhaust gas, for example, to about 40°C while indirectly recovering heat using a heat exchanger.

[0030] The cooled exhaust gas contains carbon dioxide and nitrogen oxides (NOx) such as nitrogen monoxide (NO) and nitrogen dioxide (NO2). The amount of NOx contained is, for example, in the range of 300 to 500 ppm, with an average of about 480 ppm, and the amount of NO therein is about 90%. 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 NOx after dust separation is brought into contact with an oxidizing agent to oxidize NO in the exhaust gas to NO2. 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 NO2. An example is a method in which the above oxidizing gas is blown into the exhaust gas containing NOx using a nozzle for contact and mixing to oxidize NO to NO2. In this way, NOx contained in the exhaust gas is oxidized to NO2.

[0032] Next, the exhaust gas in which NO in the exhaust gas has been oxidized to NO2, for example, the exhaust gas cooled to 40°C or lower, is brought into contact with water to dissolve NO2 in the exhaust gas in water to prepare a nitric acid nitrogen-containing liquid (step (1)). The step (1) of preparing the nitric acid nitrogen-containing liquid is a step that utilizes a process for absorbing NOx with water.

[0033] Specifically, since NO2 dissolves in water, as described above, the exhaust gas in which NO has been oxidized to NO2 is brought into contact with water to absorb the NO2 contained in the exhaust gas in water, thereby obtaining a nitric acid nitrogen-containing liquid. As the water brought into contact with the exhaust gas containing NO2, industrial water, seawater, artificial seawater, etc. can be used according to the growth environment of algae. For example, by blowing the above exhaust gas in which NO has been oxidized to NO2 into water and aerating it to react NO2 with water, or by indirectly recovering heat using a heat exchanger and reacting NO2 with water, a nitric acid 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 equations. NO + O3 → NO2 + O2 2NO2 + O3 → N2O5 + O2 2NO + O2 → 2NO2 Also, as shown in the following reaction equations, when NO2 comes into contact with water, for example, nitric acid nitrogen is generated. 2NO2 + H2O + 1 / 3O3 → 2HNO3 N2O5 + H2O → 2HNO3

[0035] The volume ratio of (HNO3 / containing liquid) in the obtained nitric acid nitrogen-containing liquid is not particularly limited, and for example, 0.01 to 0.15, preferably 0.01 to 0.08 can be exemplified. In the preparation step (1) of the nitric acid nitrogen-containing liquid, as described above, water is used as the NO2 dissolution liquid and no chemical liquids such as chemicals are used, so the cost can be kept low. Also, since it can be recovered as a nitric acid nitrogen-containing liquid and used for the culture solution of microalgae, 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 a cement incinerator, contains carbon dioxide in addition to nitrogen oxides, and generally contains about 10 to 30% by volume of carbon dioxide. After oxidizing NO in the exhaust gas to NO2, the exhaust gas is brought into contact with water to prepare a nitric acid nitrogen-containing liquid. At this time, since the CO2 contained in the exhaust gas also comes into contact with the water, the CO2 can also be dissolved in the water, and carbon dioxide can be included in the nitric acid nitrogen-containing liquid. Thereby, it can be contained in the culture solution from which carbon dioxide is obtained, and it becomes possible to effectively use the carbon dioxide 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, waste such as nitrogen-containing waste, for example, coal ash, general incineration ash, construction-generated soil, incinerated 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 water used to wash the dust, 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 as the phosphorus and / or potassium-containing washing water serving as a source of phosphorus and / or potassium, together with the above-mentioned nitrate nitrogen-containing solution.

[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 an alkaline range of about pH 8 to 10, preferably pH 8.5 to 9.5, 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 acid nitrogen-containing solution obtained in the above step (1) and containing dissolved carbon dioxide 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 with the nitric acid nitrogen-containing solution obtained in the above step (1) and containing dissolved carbon dioxide, 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 growing 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 with the above acidic nitric acid nitrogen-containing solution obtained in step (1) to prepare the above neutral range mixed solution, and a culture solution for microalgae can be produced for use as a pH adjuster for the culture solution of microalgae and a nutrient source. Or, when it does not contain heavy metals or contains only a trace amount if any, since the washing water obtained by washing dust such as desalting dust hardly contains heavy metals, when the washing water containing phosphorus and / or potassium is directly introduced together with the nitric acid nitrogen-containing solution obtained in step (1) to prepare a culture solution, it is also possible to adjust the pH of the culture solution to the above pH in the neutral range by introducing a pH adjusting material as necessary. Here, as the pH adjusting material, the above pH adjusting material can be used.

[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 nitrogen, phosphorus and / or potassium, and carbon dioxide which are nutrient sources for microalgae and necessary for photosynthesis. By using the culture solution for culturing microalgae, the nitrogen, phosphorus and / or potassium, and carbon dioxide contained in the culture solution can be effectively utilized by the microalgae, 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, gray algae, diatoms, brown algae, chlamydomonas algae, 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 to obtain dried microalgae. The exhaust gas is adjusted to less than 300 °C by, for example, a heat exchanger and 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, etc.

[0048] In this way, the method for producing and culturing the culture solution of microalgae according to the present invention can effectively utilize waste such as exhaust gas and desalination dust discharged from a cement factory, etc., and use nitrogen, phosphorus and / or potassium, which are nutrient sources necessary for culturing microalgae, and carbon dioxide to supply microalgae to obtain a culture solution that can be cultured. 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, etc., 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, etc. that manufactures cement, and in the industry that cultures microalgae, it is possible to apply it to effectively culture microalgae by using the culture solution produced according to the present invention.

Claims

1. An oxidant is added to the exhaust gas containing NOx and CO2 discharged from the cement manufacturing facility to oxidize NO in the NOx to NO ２ and then the exhaust gas containing NO ２ and CO2 is brought into contact with water to dissolve NO ２ and CO2 in the exhaust gas in water to obtain a nitric acid nitrogen and CO2-containing solution (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 added to the nitric acid nitrogen and CO2-containing solution obtained in Step 1, and the pH of the mixed solution of the aqueous solution containing phosphorus and / or potassium and the nitric acid nitrogen and CO2-containing solution is adjusted to 5 to 8 to prepare a culture solution of microalgae containing nitrogen, phosphorus and / or potassium, and CO2 (Step 3). A method for producing a culture solution of 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, wherein the oxidizing agent is oxygen or ozone, a method for producing a culture solution of microalgae using waste.

3. In the method for culturing microalgae, 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 CO2 in the culture solution is used for photosynthesis of microalgae, and the culture solution containing the cultured microalgae is centrifuged, and the obtained microalgae are dried using waste heat from cement manufacturing equipment to obtain dried algal bodies.

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