Fertilizer composition for promoting seaweed growth and fertilizing method using the same

Abstract

The fertilizer composition for promoting seaweed growth according to the present invention comprises an iron (Fe) source and coffee grounds in a weight ratio of 3:1 to 1:9.

Description

Technology Field

[0001] The present invention relates to a fertilizer composition for promoting the growth of seaweed and a method of fertilization using the same. Background Technology

[0002] Excessive coastal development, an increase in herbivores, and climate change have had a significant impact on coastal ecosystems, and in particular, the phenomenon of coastal desertification, characterized by the loss of seaweed, is becoming very serious. According to a survey on the status of coastal desertification in the Korean Peninsula provided by the Korea Fisheries Resources Agency (FIRA), the total damaged area of ​​coastal desertification nationwide was reported to be 19,100 hectares as of 2020, which is equivalent to 44 times the area of ​​Yeouido. One of the causes of this desertification phenomenon is identified as the blockage of inorganic nutrients necessary for the growth of seaweed flowing into rivers due to excessive coastal development, such as land reclamation and land filling.

[0003] Since the mid-to-late 2000s, Japan has been manufacturing iron-based fertilizers and conducting tests on their effectiveness in growing seaweed and restoring coastal erosion areas. As a result, it has been reported that iron treatment is effective for the growth of gametophytes and young leaves of Laminaria japonica. Meanwhile, in Korea, technology utilizing iron sulfate and leaf mold as seaweed growth promoters has also been reported. The purpose of developing such iron-based fertilizers is to resolve the iron deficiency among nutrients in coastal areas affected by coastal erosion and to supply Fe, which is necessary for the photosynthesis and young leaf growth of seaweed.

[0004] Generally, seawater exhibits a slightly alkaline pH of approximately 8.0 to 8.4. Since the solubilization of inorganic nutrients, including iron, varies depending on pH conditions, it is necessary to maintain an appropriate pH or supply inorganic nutrients in a form suitable for the pH conditions. In particular, in the case of slightly alkaline seawater, the degree of solubilization of iron varies significantly depending on the form of the salt. Generally, when iron fertilizer salts (divalent iron) used for crops are applied to seawater, they are rapidly oxidized by dissolved oxygen in the seawater and converted into insoluble trivalent iron, making it unavailable to seaweed. Consequently, a method has been proposed to facilitate the movement of iron in solution by adding humic acid to chelate the iron. However, applying iron salts to seawater as fertilizer along with humic acid has the disadvantage of requiring additional processes, such as installing nets or devices to prevent fertilizer loss.

[0005] Meanwhile, 159,000 tons of coffee grounds are generated annually in Korea (as of 2016), and accordingly, various studies utilizing coffee grounds have been conducted. The problem to be solved

[0006] One aspect of the present invention for solving the aforementioned problem is to provide a fertilizer composition for promoting seaweed growth and a fertilization method using the same, which can recycle iron (Fe) from steel and industrial by-products as a raw material, mix an iron source with coffee grounds in an appropriate ratio to smoothly supply iron in a solubilized form that can be utilized by seaweed even in a seawater environment, and is manufactured as a solid fertilizer such as a pellet or block type that can be supplied in seawater for a long period of time.

[0007] The technical problems to be solved in this document are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this invention belongs from the description below. means of solving the problem

[0008] To achieve the above objective, a fertilizer composition for promoting algae growth according to one embodiment of the present invention may include an iron (Fe) source and coffee grounds in a weight ratio of 3:1 to 1:9.

[0009] In addition, the iron source according to one embodiment of the present invention may include one or more selected from iron, steelmaking slag, steelmaking dust, and non-ferrous slag.

[0010] In addition, the fertilizer composition according to one embodiment of the present invention may further include 4 to 12 weight percent of any one selected from a binder, a base, and a mixture thereof.

[0011] In addition, the binder according to one embodiment of the present invention may include any one selected from starch, molasses, and mixtures thereof.

[0012] In addition, the fertilizer composition according to one embodiment of the present invention may be in the form of a powder, block, or pellet.

[0013] In addition, the fertilizer composition in the pellet form according to one embodiment of the present invention may be in a shape including one or more of spherical, cylindrical, polygonal, hexahedral, and irregular shapes.

[0014] In addition, the fertilizer composition of the pellet formulation according to one embodiment of the present invention may have a moisture content of 10% to 20% by weight.

[0015] In addition, the fertilizer composition in the pellet form according to one embodiment of the present invention may have a compressive strength of 40 N or more.

[0016] In addition, the fertilizer composition according to one embodiment of the present invention may be for the growth of one or more seaweeds selected from green laver, wakame, kelp, Ecklonia cava, and Sargassum fusiforme.

[0017] In addition, a method for manufacturing a fertilizer for promoting the growth of seaweed according to one embodiment of the present invention comprises the steps of: mixing an iron source and coffee grounds; and preparing the mixture into a pellet formulation; wherein the iron source and coffee grounds may be included in a weight ratio of 3:1 to 1:9.

[0018] In addition, the pellet according to one embodiment of the present invention may have a shape including one or more of spherical, cylindrical, polygonal, hexahedral, and irregular shapes.

[0019] In addition, a method for applying a fertilizer for promoting seaweed growth according to one embodiment of the present invention may include the step of introducing a fertilizer composition for promoting seaweed growth, comprising an iron source and coffee grounds in a weight ratio of 3:1 to 1:9, into seawater where seaweed is growing. Effects of the invention

[0020] According to the present invention, iron (Fe) can be recycled from steel and industrial by-products as a raw material, and by mixing an iron source and coffee grounds in an appropriate ratio, iron can be smoothly supplied in a solubilized form that can be utilized by seaweed even in a seawater environment, and a fertilizer composition for promoting seaweed growth can be provided that is manufactured as a solid fertilizer such as a pellet or block type and can be supplied in seawater for a long time.

[0021] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below. Brief explanation of the drawing

[0022] Figure 1 is a diagram showing the leaching concentration of soluble iron in seawater according to the weight ratio of an iron source and coffee grounds according to one embodiment of the present invention. Figure 2 is a figure showing the results of confirming the polyphenol content according to the weight ratio of the iron source and coffee grounds according to one embodiment of the present invention. FIG. 3 is a drawing showing a cylindrical pellet fertilizer according to one embodiment of the present invention. Figure 4 is a diagram showing the results of measuring compressive strength according to the moisture content of pellet fertilizer according to one embodiment of the present invention. FIG. 5 is a drawing showing a spherical pellet fertilizer according to one embodiment of the present invention. Figure 6 is a diagram showing the results of measuring compressive strength according to the binder content of pellet fertilizer according to one embodiment of the present invention. FIG. 7 is a diagram showing the measurement results of the length change of Ecklonia cava grown by treating it with the fertilizer of the present invention in an actual sea test field according to one embodiment of the present invention. Specific details for implementing the invention

[0023] Preferred embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the relevant technical field.

[0024] The terms used in this application are used merely to describe specific examples. For this reason, singular expressions include plural expressions unless the context clearly requires them to be singular. Additionally, it should be noted that terms such as “comprising” or “comprising” used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the existence of other features, steps, functions, components, or combinations thereof.

[0025] Meanwhile, unless otherwise defined, all terms used in this specification shall be understood to have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Accordingly, unless explicitly defined in this specification, specific terms should not be interpreted in an overly ideal or formal sense. For instance, singular expressions in this specification include plural expressions unless the context clearly indicates an exception.

[0026] Additionally, terms such as "about," "substantially," etc., in this specification are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values ​​are mentioned to aid in understanding the invention.

[0027] The present invention aims to provide a fertilizer for promoting the growth of seaweed that supplies iron (Fe) necessary for the growth and development of seaweed by utilizing steel and industrial by-products as iron raw materials and mixing coffee grounds in an appropriate ratio, thereby supplying iron in a solubilized state that seaweed can utilize even under seawater pH conditions.

[0028] A fertilizer composition for promoting seaweed growth according to one embodiment of the present invention comprises an iron (Fe) source and coffee grounds.

[0029] The seaweed to which the present invention can be applied may include green laver, wakame, kelp, Ecklonia cava, and Sargassum fusiforme, but is not limited thereto.

[0030] The following describes in detail a fertilizer composition for promoting the growth of seaweed.

[0031] The above iron source may be used without restriction as long as it is a raw material for supplying iron commonly used in the industry, and preferably, iron (Fe), steel containing iron components, or industrial by-products may be used, and specifically, steel by-products such as steelmaking slag and steelmaking dust, and industrial by-products such as non-ferrous slag may be used.

[0032] The above iron source may be included in the form of powder or granules, for example, steelmaking slag may be included in the form of powder that is dried at 100°C to 150°C for 1 hour to 48 hours and then ground to 500 µm or less.

[0033] The above iron source may be included in the fertilizer composition in an amount of 9% to 75% by weight, preferably 15% to 50% by weight, and more preferably 15% to 25% by weight. If the iron source is less than 9% by weight, it may be difficult to supply sufficient iron necessary for photosynthesis and leaf growth of seaweed, and if it exceeds 75% by weight, it may be difficult for the iron to move in seawater or to exist in a soluble state.

[0034] Meanwhile, iron is an inorganic nutrient that can exist in the form of divalent or trivalent iron under the pH conditions of seawater, which is weakly alkaline with a pH of 8.0 to 8.4. Iron used as fertilizer may be divalent iron, and it can be converted into insoluble trivalent iron by dissolved oxygen in seawater.

[0035] Accordingly, in the present invention, by mixing coffee grounds in an appropriate ratio with an iron source in a fertilizer composition for promoting the growth of seaweed, it is possible to supply soluble iron that can be utilized by seaweed even in seawater.

[0036] The above coffee grounds are a byproduct remaining after extracting coffee liquid from coffee beans, and are rich in fiber, organic matter, lignin, caffeine, polyphenol compounds, etc., which are useful for plant cultivation.

[0037] Although the leaching of soluble iron increases as the content of the coffee grounds increases, the mixing ratio of the iron source and the coffee grounds is of the utmost importance because an excessively high content of the coffee grounds can reduce the density of the fertilizer. Accordingly, in the present invention, by mixing the iron source and the coffee grounds at an optimal ratio, the oxidation of iron into an insoluble form in seawater can be prevented and the leaching of soluble iron can be optimized. Furthermore, by fertilizing the iron salt to facilitate the movement of iron in the solution state, the function as a fertilizer for use under marine conditions can also be appropriately controlled.

[0038] The above coffee grounds may be included in the form of dried powder, for example, by drying the coffee grounds at 50°C to 90°C and grinding them as needed to obtain a powder form.

[0039] In the present invention, the method of grinding coffee grounds into powder is not particularly limited and may be done, for example, by hot air drying, oven drying, etc., and preferably by oven drying. The method of obtaining the powder form is also not particularly limited and may be ground, for example, by an impact grinding method using a ball mill, etc.

[0040] The above iron source and coffee grounds may be included in a weight ratio of 3:1 to 1:9, preferably in a weight ratio of 1:1 to 1:5, and more preferably in a weight ratio of 1:3 to 1:5.

[0041] If the above iron source exceeds 3 times the weight ratio of the coffee grounds (3:1), the chelating effect of the coffee grounds relative to the iron supply is weakened, and the iron supply may not be smooth. If the coffee grounds source exceeds 9 times the weight ratio of the iron source (9:1), the leaching of soluble iron may not be smooth, and it may be difficult to manufacture solid fertilizer in the form of pellets or blocks. There is also a problem that the excessive amount of coffee grounds relative to the iron supply may chelate and supply cations other than iron.

[0042] In particular, in order to more effectively leach soluble iron under seawater conditions and supply it in a form of soluble iron suitable for use by seaweed, it is preferable that the iron source and coffee grounds be included in a weight ratio of 1:1 to 1:5, and more preferably in a weight ratio of 1:3 to 1:5.

[0043] In addition, the fertilizer composition for promoting seaweed growth according to the present invention may further include any one selected from a binder, a base, and a mixture thereof to supplement strength considering the transportation, storage, and use of the fertilizer.

[0044] Specifically, the binder or base may be used without limitation as long as it can be used to manufacture solid fertilizer. For example, one or more selected from starch, molasses, lignin, and waste molasses may be used, and preferably, starch, molasses, or a mixture thereof may be used. The base may be rare earth minerals such as monazite or zeolite.

[0045] The binder or base may be included in the fertilizer composition in an amount of 4% to 12% by weight, preferably 8% to 12% by weight, and more preferably 10% by weight. When the binder content is within the above range, appropriate strength can be maintained, making it easiest to handle and fertilize with seawater flow when considering the transportation, storage, and use of the fertilizer.

[0046] In addition, the fertilizer composition for promoting seaweed growth according to the present invention may be in the form of a powder, block, or pellet, and preferably may be in the form of a pellet.

[0047] Specifically, the fertilizer composition in the pellet form may be in a shape including one or more of spherical, cylindrical, polygonal, hexahedral, and irregular shapes.

[0048] When the fertilizer composition is in the form of pellets, the moisture content may be 10% to 20% by weight, preferably 15% by weight. If the moisture content is less than 10% by weight or exceeds 20% by weight, the compressive strength of the pellets may decrease, making it difficult to transport, store, and use the fertilizer.

[0049] In addition, if the fertilizer composition is in the form of pellets, the compressive strength may be 40 N or more, and preferably 40 N or more and 80 N or less. When the strength is within the above range, handling and fertilization with seawater flow may be easiest when considering the transportation, storage, and use of the fertilizer.

[0050] In addition, a method for manufacturing a fertilizer for promoting the growth of seaweed according to one embodiment of the present invention may include the step of mixing an iron source and coffee grounds; and the step of manufacturing the mixture into a pellet formulation.

[0051] The above iron source can be used in powder form by drying iron (Fe), steelmaking slag containing iron components, steelmaking dust, and other steelmaking by-products, and non-ferrous slag at 100°C to 150°C for 1 hour to 48 hours, and then grinding them to a size of 500 μm or less.

[0052] The above coffee grounds can be used after drying at 50 to 100°C for 1 to 48 hours.

[0053] The above-mentioned powdered iron source and coffee grounds can be mixed in a weight ratio of 3:1 to 1:9, preferably 1:1 to 1:5, and more preferably 1:3 to 1:5.

[0054] The above iron source and coffee grounds mixture may further include any one selected from a binder, a base, and a mixture thereof in an amount of 4% to 12% by weight.

[0055] The above mixture can be mixed using a homogenizer and then manufactured into a pellet formulation using a pellet compression molding machine. At this time, the pellet may have a shape including one or more of spherical, cylindrical, polygonal, hexahedral, and irregular shapes.

[0056] Subsequently, after manufacturing into the above pellet formulation, it can be cooled and dried using a cooling device or the like to produce a pellet formulation fertilizer.

[0057] The seaweed growth-promoting fertilizer of the present invention, manufactured in the above pellet formulation, may have a moisture content of 10% to 20% by weight, preferably 15% by weight. In addition, the compressive strength of the seaweed growth-promoting fertilizer in the above pellet formulation may be 40N or more, preferably 40N or more and 80N or less.

[0058] In addition, a method for applying a fertilizer for promoting seaweed growth according to one embodiment of the present invention may include the step of introducing a fertilizer composition for promoting seaweed growth, comprising an iron (Fe) source and coffee grounds in a weight ratio of 3:1 to 1:9, into seawater where seaweed is growing.

[0059] The above-mentioned step of adding the fertilizer composition may be added to seawater at a weight of 5 to 200 times the weight of the fertilizer composition for promoting seaweed growth, and preferably to seawater at a weight of 10 to 100 times.

[0060] The present invention will be explained in more detail below through the following examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited thereto.

[0061] Example 1. Preparation of fertilizer for promoting seaweed growth

[0062] Steel slag (Gwangyang Steelworks), coffee grounds, and coffee grounds (Go Around Coffee) were used as raw materials to manufacture fertilizer for promoting the growth of seaweed.

[0063] First, unaged steel slag (Gwangyang Steelworks) was purchased from Hyoseok Co., Ltd., dried at 105°C for 24 hours, and ground to a diameter of 500㎛ or less to prepare it in powder form. Coffee grounds were supplied by 'Go Around Coffee' and dried at 80°C for 24 hours for use. Subsequently, the above-mentioned powdered steel slag and coffee grounds are mixed so that their weight ratios are 1:20 (7.14g:142.86g), 1:14 (10g:140g), 1:10 (13.6g:136.4g), 1:9 (15g:135g), 1:5 (25g:125g), 1:3 (37.5g:112.5g), 1:1 (75g:75g), 3:1 (112.5g:37.5g), 5:1 (125g:25g), 9:1 (135g:15g), 10:1 (136.4g:13.6g), 14:1 (140g:10g), and 20:1 (142.86g:7.14g) to produce a fertilizer for promoting the growth of seaweed. Manufactured.

[0064] To test the leaching concentration of soluble iron and polyphenol content under seawater conditions (pH 8.2) according to the mixing weight ratio of iron source and coffee grounds, the following experiment was conducted.

[0065] First, 0.4 L of sterilized seawater collected from Odori Beach in Pohang was filtered through a membrane filter, and then a fertilizer for promoting seaweed growth was prepared by varying the weight ratio of the steel slag and coffee grounds to 20:1, 14:1, 10:1, 9:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:9, 1:10, 1:14, and 1:20, respectively, and stirred at room temperature for 2 days.

[0066] Subsequently, the Fe leaching concentration of the membrane-filtered supernatant was quantitatively analyzed using ICP-MS, and a polyphenol content test based on the Folin Ciocalteu method was performed. The Folin Ciocalteu method is widely used as a polyphenol analysis method, and the GAE (Gallic acid equivalent) value was derived by measuring the color change of the molybdenum salt using a UV-spectrophotometer.

[0067] Figure 1 shows the results of analyzing the Fe leaching concentration. As shown in Figure 1, the leaching concentration of soluble iron tended to increase as the content of coffee grounds increased. In particular, it was confirmed that soluble iron was leached more effectively when steel slag and coffee grounds were mixed in a weight ratio of 3:1 to 1:9 compared to when steel slag and coffee grounds were mixed in weight ratios of 20:1, 14:1, 10:1, 9:1, 5:1, 1:10, 1:14, and 1:20. In particular, it was confirmed that soluble iron was leached most effectively when steel slag and coffee grounds were mixed in a weight ratio of 1:3 to 1:5. Through these results, it was found that when a fertilizer is manufactured by mixing an iron source and coffee grounds in a weight ratio of 3:1 to 1:9, the leaching effect of soluble iron can be expected even under seawater conditions.

[0068] Figure 2 shows the results of confirming the polyphenol content according to the weight ratio of steelmaking slag and coffee grounds. As shown in Figure 2, the total weight of polyphenols was found to be 0.1 to 1.8 mg GAE / g dw depending on the weight ratio of steelmaking slag and coffee grounds, and it was found that this result indicates that the higher the content of coffee grounds relative to the steel byproduct, the higher the polyphenol content.

[0069] In the following experiments, considering the leaching concentration of soluble iron under seawater conditions and the density of fertilizer, an iron source and coffee grounds were mixed in a weight ratio of 1:3 and the experiment was conducted.

[0070] Example 2. Measurement of compressive strength according to moisture content of pellet fertilizer

[0071] 150g of steel byproduct, 450g of coffee grounds powder, and purified water were weighed and mixed in a homogenizer so that the moisture content was 5 to 25% by weight, and then the mixture was processed using a pellet compression molding machine. Afterward, the mixture was cooled and dried using a cooling device to produce a cylindrical pellet formulation fertilizer with a length of 2 to 3 cm as shown in Fig. 3.

[0072] The compressive strength according to the moisture content of the cylindrical pellet fertilizer prepared above was measured, and the results are shown in Figure 4.

[0073] Compressive strength was measured using a compressive strength measuring device (BONGSHIN DBBP-500). The average value (unit N) of three measurements was taken by placing the pellet-form fertilizer inside the device and applying a conveying speed of 15 mm / min.

[0074] As shown in Figure 4, at moisture content of 5 wt% and 25 wt%, the compressive strength of the pellet-form fertilizer was found to be low at 40 N or less, respectively, but at moisture content of 10 wt% to 20 wt%, it was confirmed that the compressive strength of the pellet-form fertilizer was high at 40 N or more. In particular, at a moisture content of 15 wt%, it was confirmed that the compressive strength of the pellet-form fertilizer reached a maximum of 234 N. Through these results, it was found that when manufacturing fertilizer in a pellet form, a moisture content of 10 wt% to 20 wt% is desirable.

[0075] Example 3. Measurement of compressive strength according to binder content of pellet fertilizer

[0076] 150g of steel byproduct, 450g of coffee grounds powder, and a binder were homogeneously mixed and then fed into a pelletizing machine, and molded into spheres while simultaneously spraying a binder solution. Subsequently, spherical pellet fertilizer formulations as shown in Fig. 5 were prepared by hot-air drying at 60°C. At this time, starch and molasses were used as binders, respectively, and the mixing weight ratio of starch and molasses was adjusted to 0% to 16% by weight.

[0077] Compressive strength according to binder content was measured using the spherical pellet formulation fertilizer prepared above, and the results are shown in Fig. 6.

[0078] As shown in Figure 6, when spherical pellet fertilizers were manufactured without adding a binder, the compressive strength was measured to be 5 N or less. On the other hand, when molasses was used as a binder, a strength of 40 N or more could be secured under conditions of a mixing content of 4 wt% to 12 wt%, while at 14 wt% or more, the strength tended to weaken to 20 N or less. In addition, in the case of starch, a strength of 40 N or more could be secured under conditions of an incorporation content of 8 wt% to 12 wt%. As a result of the experiment, it was confirmed that using molasses as a binder component was more advantageous for improving strength, and that the strength reached a maximum of 78 N when molasses was mixed at 10 wt%.

[0079] Example 4. Actual sea test

[0080] 150g of steel byproduct, 450g of coffee grounds, and 30g of molasses as a binder were mixed and molded using a pelletizing machine, and then oven-dried at a temperature of 60℃ to produce spherical pellet fertilizer.

[0081] To verify the spherical pellet fertilizer manufactured above in a real sea environment, 130 kg of pellet fertilizer was applied to an artificial reef off the coast of Namyang-ri, Ulleungdo (latitude 37.28, longitude 130.49). After applying the fertilizer, the growth changes of the dominant seaweed species *Ecklonia cava* attached to the artificial reef were compared for 4 months (February to June 2022). The changes in *Ecklonia cava* length between the control group and the treatment group are shown in Figure 7.

[0082] As shown in Figure 7, before fertilizer application (i.e., before the treatment group and before the control group), the length of the sea tangle was 29.5 cm for the control group and 29.8 cm for the treatment group, showing almost no difference. However, 4 months after fertilizer application, the length growth of the sea tangle in the treatment group increased by 21.5 cm compared to before treatment, while in the control group it increased by 6.1 cm, confirming that there was no significant change in length growth.

[0083] Although embodiments of the invention disclosed above have been illustrated and described, the disclosed invention is not limited to the specific embodiments described above, and various modifications may be made by those skilled in the art to which the disclosed invention belongs without departing from the essence claimed in the claims.

Claims

Claim 1 A fertilizer composition comprising an iron source in powder form obtained by grinding steel slag to 500 μm or less and coffee grounds in a weight ratio of 1:1 to 1:5, wherein the fertilizer composition comprises a binder comprising one or more selected from starch, molasses, lignin, and waste molasses; a base selected from monazite, zeolite, and mixtures thereof, or a mixture thereof, in an amount of 4 to 12 weight%, and comprises a powder formulation; a block formulation; A fertilizer composition for promoting the growth of one or more seaweeds selected from Ulva lactuca, Undaria pinnatifida, Laminaria japonica, Ecklonia cava, and Sargassum fusiformis, wherein the fertilizer composition is in the form of a pellet, comprising one or more of spherical, cylindrical, polygonal, hexahedral, and irregular shapes, and when the fertilizer composition is in the form of a pellet, the moisture content is 10% to 20% by weight, the compressive strength is 40N or more and 80N or less, the iron leaching concentration under seawater conditions is 5.5 to 11.4 mg / L, and the total weight of polyphenols is 0.1 to 1.8 mg GAE / g dw. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 delete Claim 10 delete Claim 11 delete Claim 12 delete

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