Fertilizer and method for producing the same

Abstract

To provide a fertilizer and a method for producing the fertilizer.SOLUTION: A fertilizer includes a base material, and the base material includes a core containing porous carbide and a first binder, and a coating layer that covers at least a part of the core and contains a magnesium compound and a second binder. The coating layer may contain Mg in an amount of 1 mass% or more and 30 mass% or less with respect to the total mass of the base material. The base material has a total phosphate concentration of 0.1 mass% or more and 30 mass% or less. The base material may have a citric acid-soluble phosphate concentration of 0.1 mass% or more and 30 mass% or less.SELECTED DRAWING: Figure 1B

Description

[Technical field]

[0001] One embodiment of the present invention relates to a fertilizer and a method for producing the same. [Background technology]

[0002] It is known that an adsorbent containing iron and a porous carbide having carbon prepared from biomass as a basic material can adsorb phosphate ions derived from phosphoric acid, and can therefore be used to improve the water quality of water bodies such as rivers, lakes, and oceans. In addition, since phosphorus is fixed in the adsorbent after the water quality has been improved, the adsorbent with phosphorus fixed thereto can also be used as a fertilizer (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-138550 [Patent Document 2] JP 2022-138628 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one embodiment of the present invention is to provide a fertilizer having a novel structure and a method for producing the same. Alternatively, an object of one embodiment of the present invention is to provide a system for storing carbon by fixing carbon dioxide in the atmosphere using the fertilizer. [Means for solving the problem]

[0005] One embodiment of the present invention is a fertilizer. The fertilizer includes a base material, the base material having a core including a porous carbide and a first binder, and a coating layer covering at least a portion of the core and including a magnesium compound and a second binder. The coating layer includes magnesium in an amount of 1% by mass or more and 30% by mass or less with respect to the total mass of the base material. The total phosphoric acid concentration of the base material is 0.1% by mass or more and 30% by mass or less.

[0006] One embodiment of the present invention is a method for producing a fertilizer. The method includes preparing a base material by treating a precursor with water containing at least one of phosphorus and nitrogen. The precursor has a core containing a porous carbide and a first binder, and a coating layer covering at least a portion of the core and containing a magnesium compound and a second binder. The coating layer contains 1% by mass or more and 30% by mass or less of magnesium with respect to the total mass of the base material. [Brief description of the drawings]

[0007] [Figure 1A] FIG. 2 is a schematic perspective view of a matrix contained in a fertilizer according to one embodiment of the present invention. [Figure 1B] FIG. 2 is a schematic end view of a matrix contained in a fertilizer according to one embodiment of the present invention. [Diagram 2] FIG. 1 is a conceptual diagram showing a carbon dioxide storage system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, each embodiment of the present invention will be described with reference to the drawings, etc. However, the present invention can be embodied in various forms without departing from the gist of the present invention, and should not be construed as being limited to the description of the embodiments exemplified below.

[0009] In order to make the explanation clearer, the drawings may show the width, thickness, shape, etc. of each part diagrammatically compared to the actual embodiment, but these are merely examples and are not intended to limit the interpretation of the present invention.

[0010] In this specification and claims, the expression "a structure is exposed from another structure" means an embodiment in which a part of a structure is not covered by another structure, and includes an embodiment in which the part not covered by the other structure is covered by yet another structure.

[0011] Hereinafter, a fertilizer according to one embodiment of the present invention, a method for producing the fertilizer, and a carbon dioxide storage system using the fertilizer will be described.

[0012] 1. Composition of fertilizer A fertilizer according to an embodiment of the present invention has a base material and may further contain a fertilizer auxiliary. The composition ratio of the base material and the fertilizer auxiliary can be determined arbitrarily, and for example, the weight ratio of the base material in the fertilizer may be 30% or more and 100% or less, 50% or more and 100% or less, or 70% or more and 100% or less.

[0013] 1-1. Base material FIG. 1A shows a schematic perspective view of the base material 100, and FIG. 1B shows a schematic view of an end surface perpendicular to the length direction. As shown in these figures, the base material 100 basically comprises a core 102 and a coating layer 104 covering the core 102. The coating layer 104 may cover the entire surface of the core 102, or, although not shown, may cover only a part of the surface of the core 102. In the latter case, the other part of the surface of the core 102 is exposed from the coating layer 104. By covering the surface of the core 102 with the coating layer 104, physical strength is imparted to the base material 100, and phosphorus and nitrogen, which are effective as fertilizer components, can be introduced. As will be described later, in the process of fixing phosphorus and nitrogen to the base material 100, the precursor of the base material 100 is brought into contact with water containing phosphorus and nitrogen. Even if the precursor is placed in water for a long period of time in this process, the precursor is prevented from being eroded by water and from collapsing, and the shape can be maintained for a long period of time.

[0014] The shape of the base material 100 is arbitrary, and may be a plate or powder, or may be a pellet as shown in FIG. 1A. In the case of a pellet, the shape of the base material 100 may be a sphere or a cylinder, or may be a cylinder (prism) with polygonal end faces, such as an elliptical cylinder, triangular prism, quadrangular prism, pentagonal prism, or hexagonal prism (not shown). Therefore, the base material 100 may have the shape of a sphere, a cylinder, an elliptical cylinder, or a prism with a missing part. In addition, the base material 100 does not need to have the shape of a perfect sphere, cylinder, or prism, and may occupy, for example, 75% or more of the volume of the base material 100 relative to the total volume of a cylinder having the minimum volume in which the base material 100 is inscribed.

[0015] When the base material 100 is a cylinder or can be regarded as a cylinder, its diameter D may be 1 mm or more and 20 mm or less, 2 mm or more and 11 mm or less, or 3 mm or more and 8 mm or less. 2 More than 300mm 2 The aspect ratio of the base material 100, i.e., the ratio of the length L to the diameter D (L / D), is also arbitrary and can be, for example, 0.5 to 5.0. Specifically, the length L can be 0.5 mm to 100 mm, 1 mm to 20 mm, 3 mm to 15 mm, or 6 mm to 12 mm.

[0016] When the base material 100 is in powder form, the average particle size may be, for example, 100 μm to 5 mm, 100 μm to 5 mm, 500 μm to 2 mm, or 500 μm to 1 mm. As described below, the powdered base material 100 is produced by crushing a larger plate- or pellet-shaped base material 100. Thus, the present fertilizer includes the powdered base material 100 in which a part of the surface of the core 102 is covered with the coating layer 104.

[0017] (1) Core The core 102 determines the shape of the base material 100 and fixes the coating layer 104 that allows the base material 100 to exhibit the function of fixing phosphorus and nitrogen. The core 102 has a porous carbide as a basic skeleton and further contains a binder (hereinafter, a first binder).

[0018] Porous charcoal is a charcoal produced by using organic matter as a raw material and heating and carbonizing the organic matter under conditions of low oxygen concentration. An example of organic matter is biomass. Here, biomass refers to substances derived from living organisms and their metabolites. Specifically, wooden molded products such as plank-shaped or column-shaped wood, thinning wood, pruning waste, construction waste wood, powdered sawdust, and particle boats can be mentioned. There is no restriction on the type of wood, and cedar, cypress, and bamboo can be used. Other examples of biomass include agricultural waste such as rice husks, bagasse, corn cobs and leaves, and agricultural by-products such as straw, wheat straw, and hay. Other examples include plants that are the raw material for fibers such as hemp, flax, cotton, sisal, abaca, and palm hair. Other examples include algae such as seaweed. Other examples include food waste and silage obtained from animal manure. As will be described later, by using biomass as the raw material for porous charcoal, a system for storing carbon dioxide in the atmosphere can be constructed.

[0019] The first binder functions as an auxiliary component for forming the core 102 in the granulation process described later. As the first binder, an organic binder and / or an inorganic binder can be used. As the organic binder, for example, one or more selected from molasses, blackstrap molasses, starch, dextrin, corn starch, rice bran, polyvinyl alcohol, a copolymer of vinyl acetate and ethylene or its saponified form, pulp waste liquor, lignin sulfonate, carboxymethyl cellulose, hydroxypropyl methyl cellulose, sodium alginate, phenolic resin, and tar pitch can be mentioned. As the inorganic binder, for example, cement, blast furnace slag powder, fly ash, gypsum (calcium sulfate), calcined gypsum obtained by heating and dehydrating gypsum, sodium silicate, etc. can be mentioned. In particular, inorganic binders are easy to handle and have low solubility in water, so that they are less likely to run off into water areas, and therefore have a small impact on the environment. In addition, inorganic binders are preferable because they have high weather resistance and can provide a core 102 with sufficient strength.

[0020] (2) Coating layer The coating layer 104 includes a magnesium compound and a binder (hereinafter, referred to as a second binder). There are no restrictions on the thickness of the coating layer 104, and it may be, for example, from 10 μm to 5 mm, from 20 μm to 3 mm, from 50 μm to 500 μm, or from 100 μm to 300 μm.

[0021] The magnesium compound includes at least magnesium ammonium phosphate, and may further include one or more selected from magnesium hydroxide, magnesium sulfate, magnesium carbonate, magnesium bicarbonate, and magnesium oxide.

[0022] The second binder may contain materials that can be used in the first binder. The second binder and the first binder may contain the same materials or different materials.

[0023] (3) Composition of the base material The porous carbide, which is the basic skeleton of the core 102, is contained in the base material 100 at a composition of 20% by mass to 99% by mass, 50% by mass to 90% by mass, or 60% by mass to 90% by mass with respect to the dry mass of the base material 100 (i.e., the total mass of the core 102 and the coating layer 104 excluding water, which is taken as 100% by mass). By adopting the above composition, the core 102 can be formed with light weight and sufficient strength. The composition of the porous carbide is controlled by adjusting the charge ratio during the production of the base material 100. The composition of the porous carbide in the base material 100 may also be determined from a quantitative value of carbon obtained by using, for example, a combustion / infrared absorption method.

[0024] The first binder is contained in the base material 100 in a composition of 1% by mass or more and 50% by mass or less, 10% by mass or more and 40% by mass or less, or 10% by mass or more and 30% by mass or less with respect to the total mass of the base material 100. By adopting the above composition, the core 102 can be easily molded and sufficient shape stability can be given to the core 102. The composition of the first binder is controlled by adjusting the charge ratio during the manufacture of the base material 100. The composition of the first binder may also be determined from a measured value. For example, when the first binder contains calcium sulfate, the composition may be determined from a quantitative value of sulfur obtained using ICP atomic emission spectrometry (ICP-AES) or combustion / infrared absorption method, or a quantitative value of calcium obtained using atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), potassium permanganate volumetric method, or the like.

[0025] The magnesium compound contained in the coating layer 104 is contained in a composition of 1% by mass to 30% by mass, 5% by mass to 30% by mass, or 5% by mass to 25% by mass with respect to the total mass of the base material 100. Alternatively, magnesium is contained in a composition of 1% by mass to 40% by mass, 5% by mass to 25% by mass, or 5% by mass to 25% by mass with respect to the total mass of the base material 100. Since the mass of the coating layer 104 is extremely small compared to the mass of the core 102, the coating layer 104 contains an extremely high concentration of magnesium. Specifically, the coating layer 104 may contain 1% by mass to 30% by mass of magnesium with respect to the dry mass of the coating layer 104. The magnesium composition may be determined by quantifying magnesium by applying ICP-OES or inductively coupled plasma mass spectrometry (ICP-MS) to the base material 100.

[0026] The second binder is contained in a composition of 0.1% by mass to 10% by mass, 1% by mass to 5% by mass, or 1% by mass to 3% by mass with respect to the total mass of the base material 100. The composition of the second binder is also controlled by adjusting the charge ratio during the manufacture of the base material 100. As with the first binder, the composition of the second binder may be determined from a measured value. When the magnesium compound and the second binder contained in the coating layer 104 satisfy the above composition, the precursor is prevented from collapsing in water, and the precursor can exhibit high adsorption ability (described later) for phosphorus and nitrogen.

[0027] Furthermore, the base material 100 contains phosphorus and nitrogen at a relatively high composition due to the immobilization of phosphorus and nitrogen described later. For example, the total phosphoric acid concentration based on the dry mass of the base material 100 is 0.1 mass% to 30 mass%, 0.5 mass% to 20 mass%, or 1 mass% to 5 mass%. The total nitrogen concentration based on the dry mass of the base material 100 is 0.02 mass% to 6 mass%, or the citrate-soluble phosphoric acid (phosphoric acid soluble in a 2% citric acid aqueous solution) concentration based on the dry mass of the base material 100 is 0.1 mass% to 30 mass%, 0.5 mass% to 20 mass%, or 1 mass% to 5 mass%. The total phosphoric acid concentration, citrate-soluble phosphoric acid concentration, and total nitrogen concentration can be measured by appropriately using a known method. For example, the total phosphate concentration and citric acid-soluble phosphate concentration may be measured using molybdenum blue absorptiometry, and the total nitrogen concentration may be measured using alkaline potassium peroxodisulfate ultraviolet absorptiometry.

[0028] 1-1. Fertilizer additives The optional fertilizer aid is an aid containing fertilizer components essential for plant growth. The fertilizer components include one or more selected from potassium, calcium, manganese, silicic acid, and boron. Specific examples of the fertilizer aid include calcium sulfate, oil cake, flavored chicken droppings, fish meal, bone meal, rice bran, bat guano, compost, wood ash, lime, chemical fertilizer, compost, and livestock manure.

[0029] 2. Fertilizer manufacturing method A fertilizer according to one embodiment of the present invention can be manufactured by preparing a base material 100 and, if necessary, mixing the base material 100 with a fertilizer auxiliary. In manufacturing the base material 100, first, a mixture of a porous carbide and a first binder is granulated to form a core 102, and then the core 102 is coated with a coating layer 104 to obtain a precursor of the base material 100. Then, phosphorus and nitrogen are fixed to the precursor to manufacture the base material 100. These steps are described below.

[0030] (1) Preparation of porous carbide Porous carbonization is achieved by heating and carbonizing an organic material in an inert gas atmosphere such as argon gas, a low-oxygen atmosphere, a reducing atmosphere, or a reduced-pressure atmosphere. 2 Pa or more 10 5 The carbonization may be performed by heating the organic matter at a pressure of 10 Pa or less. Alternatively, the carbonization may be performed by heating at normal pressure under conditions of an oxygen concentration of 0.01% to 3% or 0.1% to 2%. The heating temperature in the carbonization may be 400°C to 1200°C, 500°C to 1100°C, or 600°C to 1000°C. The heating time may be 10 minutes to 10 days, or 10 minutes to 5 hours.

[0031] Carbonization is carried out using an internal combustion or external heat carbonization furnace. Carbonization of biomass generates dry distillation gas, and a porous carbonized material is produced in which pores of various shapes and sizes are formed, which are a complex mixture of pores due to the structure of the biomass and pores formed by desorption of the dry distillation gas. Dry distillation gas mainly contains combustible or reducing gases such as hydrogen, carbon monoxide, and alkanes such as methane, propane, and butane. Dry distillation gas is extracted at high temperatures (700°C to 1300°C), so its thermal energy and combustibility can be used as an energy source for power generation and hot water supply. Therefore, amorphous carbonized material obtained by gasification power generation of biomass (waste coal from wood biomass gasification power generation) can be used as the porous carbonized material. If the porous carbonized material obtained by carbonization contains pellet-shaped porous carbonized material, it is appropriately crushed and processed into powder before the subsequent granulation process.

[0032] (2) Granulation Thereafter, the porous carbide is mixed with the first binder and granulated. At this time, water may be added as appropriate. Granulation may be performed using a compression type granulator, an extrusion type granulator, a roll type granulator, a blade type granulator, a melt type granulator, or a spray type granulator. The porous carbide formed by granulation may be appropriately cured. For example, the curing may be performed by leaving the mixture at rest at a temperature of room temperature or higher and 50° C. or lower for a period of one day or more and one month or less. Through the above steps, the core 102 is formed.

[0033] (3) Formation of coating layer The coating layer 104 can be formed by mixing the magnesium compound and the second binder with the core 102. For example, the magnesium compound and the second binder, or a mixture thereof, may be brought into contact with the core 102 while stirring the core 102. At this time, a solvent such as water or an alcohol such as ethanol or isopropanol may be used as appropriate. The solvent is preferably added in a mist state. The magnesium compound used at this time is selected from magnesium hydroxide, magnesium sulfate, magnesium carbonate, magnesium hydrogen carbonate, and magnesium oxide. Among these magnesium compounds, magnesium hydroxide, magnesium oxide, or magnesium carbonate is preferred, as they can coat the core 102 more effectively.

[0034] Alternatively, a dispersion obtained by mixing a mixture of the magnesium compound and the second binder with a solvent may be added to the core 102. Examples of the solvent include water and alcohol as described above. The dispersion is spray-coated or dip-coated onto the core 102 to form a coating layer 104 on the surface of the core 102. After the coating layer 104 is formed, curing may be performed as necessary. As with the curing after granulation, curing may be performed by leaving the mixture at rest for one day to one month at a temperature between room temperature and 50°C. The precursor of the base material 100 is obtained by the above steps.

[0035] (4) Phosphorus and nitrogen fixation Subsequently, phosphorus and nitrogen are fixed to the precursor. The fixation of phosphorus and nitrogen may be performed by contacting the precursor with water containing phosphorus and nitrogen (hereinafter, the water to be treated). This process may be performed in a batch manner or a continuous manner. For example, the precursor may be filled in a container or bag made of a meshed metal plate, cloth, or the like, and brought into contact with the water to be treated.

[0036] The water to be treated may contain nitrogen (particularly inorganic nitrogen such as ammonia nitrogen) and phosphorus (particularly inorganic phosphorus such as orthophosphate phosphorus and polymerized phosphorus). For example, artificially prepared water to be treated may be brought into contact with the precursor. In this case, water to be treated may contain, as a phosphorus source, for example, phosphoric acid, phosphates such as sodium phosphate, sodium hydrogen phosphate, and potassium phosphate, and as a nitrogen source, ammonium chloride, nitrates such as ammonium nitrate and sodium nitrate, and nitrites such as ammonium nitrite and sodium nitrite. Alternatively, water from various bodies of water such as rivers, lakes, and oceans, or water stored in purified water reservoirs may be used as the water to be treated. The coating layer 104 contains a magnesium compound such as magnesium hydroxide, and magnesium ammonium phosphate is produced by the reaction between inorganic nitrogen and inorganic phosphorus. Magnesium ammonium phosphate has low solubility in water, and is fixed to the coating layer 104 and the core 102. As a result, phosphorus and nitrogen are fixed to the precursor, and the base material 100 can contain phosphorus and nitrogen at a relatively high concentration.

[0037] In this process, phosphorus and nitrogen contained in the water to be treated are removed. Since phosphorus and nitrogen are typical water pollutants, in this process the precursor also functions as an adsorbent to remove pollutants from various water bodies and purified water reservoirs. Furthermore, since the core 102 contains porous carbonized material, it is possible to adsorb and remove various organic compounds such as trihalomethanes and their precursors, anionic surfactants, and pesticides that may be contained in the water. Therefore, it can be said that the production of fertilizer containing the base material 100 also greatly contributes to improving water quality.

[0038] The base material 100 obtained by the above-mentioned process can be used directly as a fertilizer, but it may also be used as a fertilizer after being mixed with a fertilizer auxiliary. In this case, it is preferable to use the base material 100 after crushing and classifying it according to the type and size of the fertilizer auxiliary used so that the base material 100 and the fertilizer auxiliary are mixed more uniformly. In addition, the base material 100 may be mixed with the fertilizer auxiliary, fermented, and used as a fertilizer. A fertilizer according to one embodiment of the present invention is produced by the above-mentioned process.

[0039] 3. Carbon dioxide storage system A carbon dioxide storage system can be constructed through the production and use of a fertilizer according to one embodiment of the present invention. Specifically, as shown in Fig. 2, in the production of the base material 100, a porous charcoal obtained by carbonizing an organic matter such as biomass is one of the raw materials. At this time, by using the dry distillation gas obtained by carbonizing the biomass as an energy source, it is possible to generate electricity, produce hot water, and the like (Fig. 2, (1)).

[0040] The resulting porous charcoal is mixed with a first binder to give a core 102, which is coated with a coating layer 104 to give a precursor (Fig. 2, (2)). As described above, the precursor improves water quality by adsorbing phosphorus and nitrogen contained in various water bodies and reservoirs, and fixes the phosphorus and nitrogen as magnesium ammonium phosphate to give a base material 100 (Fig. 2, (3)). The base material 100 is mixed with a fertilizer aid as appropriate. The phosphorus and nitrogen fixed in the base material 100 are essential elements for plant growth, and therefore the base material 100 containing phosphorus and nitrogen functions as a fertilizer and contributes to plant growth. Plants use the phosphorus and nitrogen released from the base material 100 as part of their nutrients and fix carbon dioxide by photosynthesis (Fig. 2, (4)). This provides not only food but also materials such as wood, and the residues of food and materials can be used again as biomass.

[0041] In this way, by applying the embodiment of the present invention, a cycle is established that includes (1) the production of a porous charcoal from biomass, (2) the production of a precursor, (3) the production of a fertilizer containing the base material 100 through water quality improvement using the precursor, and (4) the growth of plants that use this fertilizer and the regeneration of biomass. In this cycle, the carbon dioxide in the atmosphere that is fixed by the plants is used as a porous charcoal that constitutes an organic matter decomposition material, and is also stored in the ground in the form of carbon. Therefore, this cycle is a system that reduces and stores carbon dioxide in the atmosphere in the ground, and contributes not only to water quality improvement but also to the reduction of carbon dioxide in the atmosphere. EXAMPLES

[0042] In this embodiment, an example is shown in which the base material 100 is produced as a fertilizer.

[0043] As the raw material, porous charcoal (waste coal from gasification power generation at Uchiko Biomass Power Plant) of irregular shape was used. Water and ground granulated blast furnace slag (JFE Mineral Corporation, ground granulated blast furnace slag 4000) as a first binder were added to this charcoal and mixed, and the resulting mixture was put into a granulator and formed into a pellet shape with a diameter of 4 mm and a height of 4 to 15 mm to obtain a core. The mass ratio of the charcoal to the ground granulated blast furnace slag (charcoal: ground granulated blast furnace slag) was 80:20. The obtained core was cured in air at 50°C for 7 days, and then the core was put into a pan-type granulator, and a mixture of magnesium hydroxide and gypsum as a second binder was added in several portions while rotating the core to perform coating. At this time, coating was performed while adding water using a sprayer. After that, the precursor of the example was produced by curing in air at room temperature for 1 day. The mass ratio of the core, magnesium hydroxide, and second binder (core:magnesium hydroxide:second binder) was 88:10:2, and the moisture content calculated from the amount of added water was 38%.

[0044] To fix phosphorus and nitrogen to the precursor, an aqueous solution of sodium hydrogen phosphate, sodium dihydrogen phosphate, and ammonium chloride was prepared as the water to be treated. The water to be treated was adjusted so that both phosphorus and nitrogen were 50 ppm. 153 g of the precursor was packed into a cylindrical column (diameter 25 cm), and 62 L of the water to be treated was supplied to the column and circulated for 7 days. The flow rate of the water to be treated was 0.37 L / h. The water to be treated was then filtered to obtain the base material.

[0045] The total amount of phosphoric acid, soluble phosphoric acid, citric acid, and water-soluble phosphoric acid in the base material were analyzed using the ammonium vanadomolybdate spectrophotometric method of the Fertilizer Testing Methods (2022). The total nitrogen concentration was measured using alkaline potassium peroxodisulfate ultraviolet spectrophotometric method. The results are shown in Table 1. From the results in Table 1, it was confirmed that the base material of the example contains high concentrations of phosphoric acid and nitrogen.

[0046] [Table 1]

[0047] The above results suggest that the base material according to one embodiment of the present invention contains high amounts of phosphorus and nitrogen, which suggests that the water pollutants phosphorus and nitrogen can be fixed and removed during the production process of the base material, and that the base material can function as a fertilizer.

[0048] The above-described embodiments of the present invention may be combined as appropriate as long as they are not mutually inconsistent. Any embodiment in which a person skilled in the art appropriately adds or deletes components or modifies the design based on each embodiment is also included in the scope of the present invention as long as it includes the gist of the present invention.

[0049] Even if there are other effects and advantages different from those brought about by the respective embodiments described above, those which are clear from the description in this specification or which can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention. [Explanation of symbols]

[0050] 100: base material, 102: core, 104: coating layer

Claims

1. Including the base material, The base material is a core comprising a porous carbide and a first binder; and a coating layer covering at least a portion of the core and including a magnesium compound and a second binder; the coating layer contains magnesium in an amount of 1 mass % or more and 30 mass % or less with respect to the total mass of the base material, A fertilizer having a total phosphoric acid concentration of the base material of 0.1% by mass or more and 30% by mass or less.

2. The fertilizer according to claim 1, wherein the base material has a citrate-soluble phosphoric acid concentration of 0.1% by mass or more and 30% by mass or less.

3. 2. The fertilizer according to claim 1, wherein the total nitrogen concentration of the base material is 0.1% or more and 5.0% or less.

4. 2. The fertilizer of claim 1, wherein the magnesium compound comprises magnesium ammonium phosphate.

5. The fertilizer according to claim 1 , wherein the porous carbide is contained in a composition of 20% by mass or more and 99% by mass or less with respect to the total mass.

6. The fertilizer according to claim 1 , wherein the first binder is contained in a composition of 1 mass % or more and 50 mass % or less with respect to the total mass.

7. The fertilizer according to claim 1 , wherein the second binder is contained in a composition of 0.1 mass % or more and 5 mass % or less with respect to the total mass.

8. 2. The fertilizer of claim 1, wherein the first binder and the second binder each include a material selected from sodium silicate, potassium silicate, silicon oxide, gypsum, and cement.

9. 10. The fertilizer of claim 1, wherein the first binder and the second binder comprise the same material.

10. 10. The fertilizer of claim 1 further comprising a fertilizer adjuvant.

11. preparing a base material by treating a precursor with water containing at least one of phosphorus and nitrogen; The precursor is a core comprising a porous carbide and a first binder; and a coating layer covering at least a portion of the core and including a magnesium compound and a second binder; The coating layer contains 1 mass% or more and 30 mass% or less of magnesium with respect to the total mass of the base material.

12. The method of claim 11 further comprising mixing the base material with a fertilizer adjuvant.

13. The method according to claim 11 , wherein the porous carbide is contained in a composition of 20 mass % or more and 99 mass % or less with respect to the total mass.

14. The method according to claim 11 , wherein the first binder is contained in a composition of 1 mass % to 50 mass % with respect to the total mass.

15. The method according to claim 11 , wherein the second binder is contained in a composition of 0.1 mass % to 5 mass % with respect to the total mass.

16. The method of claim 11 , wherein the first binder and the second binder each include a material selected from sodium silicate, potassium silicate, silicon oxide, gypsum, and cement.

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