Compost and its production method

Abstract

To provide compost rich in water-soluble phosphate having immediate effectivity and a manufacturing method of the same.SOLUTION: A manufacturing method of compost includes: a first step of preparing an admixture by blending iron phosphate-containing carbide with an organic fertilizer source; a second step of simultaneously treating a surface of the admixture under an aerobic condition and treating its inside under an anaerobic condition; and a third step of treating the inside of the admixture treated under the anaerobic condition in an aerobic condition. The method may further include a step of preparing the iron phosphate-containing carbide by bringing iron-containing carbide into contact with water that includes phosphate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention relates to a compost and a method for producing the compost. For example, one embodiment of the present invention relates to a compost rich in water-soluble phosphate and a method for producing the compost. [Background technology]

[0002] Animal waste, such as livestock waste, can be used as an organic fertilizer source for compost. For example, Patent Document 1 discloses that compost effective for plant growth can be produced by mixing animal waste, such as feces, with steel slag containing calcium oxide, magnesium oxide, silicon oxide, manganese oxide, and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-180266 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 compost and a method for producing the same. For example, an object of one embodiment of the present invention is to provide a compost having a novel composition and a method for producing the same. Alternatively, an object of one embodiment of the present invention is to provide a compost rich in fast-acting water-soluble phosphate and a method for producing the same. [Means for solving the problem]

[0005] One embodiment of the present invention is a method for producing compost, which includes a first step of mixing an iron phosphate-containing carbide with an organic fertilizer source to prepare a mixture, a second step of simultaneously treating the surface of the mixture under aerobic conditions and the interior under anaerobic conditions, and a third step of treating the interior of the mixture that has been treated under anaerobic conditions under aerobic conditions.

[0006] One embodiment of the present invention is a compost comprising porous charcoal, water-soluble phosphoric acid, water-insoluble phosphoric acid, and further comprising iron(III) oxide and / or iron(III) hydroxide. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a flow chart showing a method for producing compost according to one embodiment of the present invention. [Figure 2] FIG. 1 is a conceptual diagram illustrating carbon dioxide storage using a compost production method according to one embodiment of the present invention. [Figure 3] 1 is a plot of the temperature change of compost during compost production in the Examples and Comparative Examples. [Figure 4] The ratio of water-soluble phosphate concentration to total phosphate concentration before and after fermentation of the primary mixture of the example and the organic fertilizer source of the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, various embodiments 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 spirit of the present invention, and should not be construed as being limited to the description of the embodiments exemplified below.

[0009] In this specification, the term "phosphoric acid" does not only refer to phosphoric acid in the narrow sense, i.e., a compound represented by the chemical formula H3PO4, but also refers to various phosphates, monohydrogen phosphates, and dihydrogen phosphates in addition to phosphoric acid (H3PO4). Thus, for example, unless otherwise specified, iron phosphate refers not only to iron phosphate but also to iron monohydrogen phosphate and iron dihydrogen phosphate, and the iron ions contained therein may be divalent or trivalent.

[0010] 1. Compost A compost according to one embodiment of the present invention contains porous charcoal, water-soluble phosphoric acid, and water-insoluble phosphoric acid, and further contains iron (III) oxide and / or iron (III) hydroxide. The compost may further contain iron (zero-valent iron). As other components, the compost may contain water and a binder, and may further contain sulfur-containing compounds, manganese-containing compounds, boron-containing compounds, fiber, and the like contained in the organic fertilizer source that is the raw material for the compost. Each of these components will be described below.

[0011] 1-1.Porous carbide Porous charcoal is a porous material containing carbon as a main component and having pores with cross-sectional diameters of several nanometers to several tens of micrometers. The composition of the porous charcoal in the compost is, for example, 2% by weight to 40% by weight or 5% by weight to 35% by weight. The specific gravity of the porous charcoal is 0.05 g / cm. 3 More than 0.8g / cm 3 or less than 0.1g / cm 3 More than 0.5g / cm 3 The specific surface area of ​​the porous carbide may be, for example, 100 m 2 / g or more 900m 2 / g or less, 100m 2 / g or more 800m 2 / g or less, or 150m 2 / g or more 400m 2 The specific surface area is measured by mercury intrusion porosimetry or a gas adsorption method such as the BJH method or HK method.

[0012] 1-2. Water-soluble phosphate Examples of water-soluble phosphates include phosphates such as lithium phosphate, sodium phosphate, potassium phosphate, and ammonium phosphate; monohydrogen phosphates such as lithium monohydrogen phosphate, sodium monohydrogen phosphate, potassium monohydrogen phosphate, and ammonium monohydrogen phosphate; dihydrogen phosphates such as lithium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate; and representative examples include alkali metal phosphates such as sodium phosphate and potassium phosphate, and alkali metal monohydrogen phosphates such as sodium monohydrogen phosphate and potassium monohydrogen phosphate. The metal ions of these water-insoluble phosphates are derived from porous charcoal or organic fertilizer sources (described below).

[0013] The compost contains water-soluble phosphate at a relatively high concentration. Specifically, the concentration may be 30% to 70%, 40% to 60%, or 40% to 50% of the total phosphate in the compost. Note that total phosphate refers to the total of water-soluble and water-insoluble phosphate. For example, the compost contains water-soluble and water-insoluble phosphate at a concentration of 1% to 21% by weight or 5% to 15% by weight.

[0014] The concentration of water-soluble phosphate can be determined, for example, using ammonium vanadomolybdate spectrophotometry. In this method, for example, water is added to compost and a predetermined amount of the water-soluble portion is collected as a sample. Nitric acid (1+1) is added to this sample and heated to hydrolyze non-orthophosphates into orthophosphate ions. Ammonium vanadate(V), hexaammonium heptamolybdate, and nitric acid are then added to produce phosphovanadomolybdate. The water-soluble phosphate is quantified by measuring the absorption of phosphovanadomolybdate (e.g., at 420 nm) using a UV-visible spectrophotometer.

[0015] The ammonium vanadomolybdate spectrophotometric method can be used to quantify total phosphate. For example, a predetermined amount of compost is digested with nitric acid or perchloric acid, and then ammonium vanadate(V), hexaammonium heptamolybdate, and nitric acid are added. The absorbance of the resulting phosphovanadomolybdate (e.g., at 420 nm) is measured using a UV-visible spectrophotometer to quantify total phosphate.

[0016] 1-3. Water-insoluble phosphate Water-insoluble phosphates are phosphoric acid that is insoluble in water but soluble in a 2% citric acid solution (citric acid-soluble phosphate). Examples of water-insoluble phosphates include calcium hydrogen phosphate, calcium dihydrogen phosphate, calcium phosphate, magnesium monohydrogen phosphate, and magnesium phosphate. The metal ions in these water-insoluble phosphates are also derived from porous charcoal or organic fertilizer sources.

[0017] 1-4. Iron(III) oxide and iron(III) hydroxide Iron(III) oxide and iron(III) hydroxide are components derived primarily from the iron mentioned above. As described below, iron(III) phosphate is produced when a mixture of porous charcoal and iron (iron-containing charcoal) is treated with water containing phosphoric acid. When iron-containing charcoal is treated with an organic fertilizer source under anaerobic conditions, iron(III) phosphate is reduced to give divalent iron ions and phosphate ions. These divalent iron ions are subsequently oxidized under aerobic conditions to form iron(III) oxide and iron(III) hydroxide. The composition of iron(III) oxide in compost is, for example, 1% by weight or more and 20% by weight or less. The composition of iron(III) hydroxide in compost is, for example, 1% by weight or more and 20% by weight or less.

[0018] 1-4.Iron The iron mentioned here is zero-valent iron, which originates from the iron powder used in the compost manufacturing process described below. In other words, at least a portion of the iron exists as iron powder.

[0019] 1-6. Binder The binder is used to efficiently disperse the porous carbide and iron powder and integrate the iron powder with the porous carbide during the compost production process (described later). There are no restrictions on the type of binder, and organic and / or inorganic binders can be used. Examples of organic binders include one or more selected from the group consisting of molasses, blackstrap molasses, starch, dextrin, cornstarch, rice bran, polyvinyl alcohol, vinyl acetate-ethylene copolymers or their saponified forms, pulp waste liquor, lignin sulfonate, carboxymethyl cellulose, hydroxypropyl methyl cellulose, sodium alginate, phenolic resin, and tar pitch. Molasses, among others, is inexpensive, contains few harmful components, and has a high solid content, making it easy to mold the removal material. Examples of inorganic binders include cement, ground granulated blast furnace slag, fly ash, gypsum (calcium sulfate), calcined gypsum obtained by heating and dehydrating gypsum, and sodium silicate.

[0020] 1-7.Other ingredients Examples of sulfur-containing compounds include sulfates of alkali metals and alkaline earth metals. Examples of manganese-containing compounds include manganese salts such as manganese sulfate, manganese nitrate, manganese chloride, manganese carbonate, and manganese borate. Examples of boron-containing compounds include the above-mentioned manganese borate and boric acid. The concentrations of these sulfur-containing compounds, manganese-containing compounds, and boron-containing compounds in the compost may be, for example, 0.01% by weight or more and 1% by weight or less.

[0021] As mentioned above, this compost contains a relatively high concentration of water-soluble phosphate, allowing it to function as a fast-acting fertilizer for plant growth. It also contains a porous carbonized material. This carbonized material not only improves soil moisture retention, but also functions as a bioreactor, allowing the microorganisms and animals living in the pores to supply the soil with nutrients, water, oxygen, and other nutrients in a balanced manner. This means that this compost can also contribute to soil improvement.

[0022] 2. Compost production method A method for producing this compost according to one embodiment of the present invention will be described below. The flow of this production method is shown in Figure 1.

[0023] 2-1. Preparation of porous carbide First, porous charcoal is prepared. Specifically, organic matter such as biomass is heated at a low oxygen concentration. Here, biomass refers to a type of organic matter, specifically, biologically derived substances and their metabolites. Examples of biomass that can be used to prepare porous charcoal include wood-derived materials. Specific examples include plank-shaped or pillar-shaped wood, thinned wood, pruning waste, construction waste, powdered sawdust, and wooden molded products such as particle boats. There are no restrictions on the type of wood, and cedar, cypress, and bamboo are also suitable. 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 of biomass include plants that are used to produce fibers, such as hemp, flax, cotton, sisal, abaca, and palm fiber. Alternatively, biomass can be algae such as seaweed, food waste, or silage obtained from animal manure.

[0024] Specifically, a porous carbonized material can be obtained by heating an organic material under an inert gas atmosphere such as nitrogen gas or argon gas, an oxygen-free atmosphere, a low-oxygen atmosphere, a reducing atmosphere, or a reduced-pressure atmosphere. 2 Pa or more 10 5 Low vacuum state below 10 Pa -1 Pa or more 10 2 Medium vacuum state below 10 Pa -5 Pa or more 10 -1 High vacuum state below 10 Pa or -5 The carbonization can be carried out in an ultra-high vacuum of 100 Pa or less. When carbonization is carried out in a low-oxygen atmosphere, the oxygen concentration can be set to 0.01% to 3%, or 0.1% to 2%. The heating temperature for carbonization can be 400°C to 1200°C, 500°C to 1100°C, 600°C to 1000°C, or 600°C to 900°C. The heating time can be 10 minutes to 10 days, or 10 minutes to 5 hours.

[0025] Carbonization is carried out using internal combustion or externally heated carbonization furnaces. Examples of carbonization furnaces include batch-type sealed charcoal kilns, continuous rotary kilns, rocking carbonization furnaces, and screw furnaces. Carbonization of organic matter generates carbonization gases, and a porous charcoal product is produced, with pores of various shapes and sizes formed by a complex mixture of pores due to the structure of the organic matter and pores formed by the desorption of the carbonization gases. The carbonization gases primarily contain flammable or reducing gases, such as hydrogen, carbon monoxide, and alkanes, such as methane, propane, and butane. Because the carbonization gases are extracted at high temperatures (700°C to 1300°C), their thermal energy and flammability can be used as energy sources for power generation and hot water supply.

[0026] 2-2. Preparation of iron-containing carbides Next, the porous carbide and iron powder are mixed to obtain an iron-containing carbide. At this time, a binder and / or water may be further added. Adding a binder and / or water can prevent the generation of dust and allow the porous carbide and iron powder to be mixed more uniformly.

[0027] The shape of the iron powder used is not limited; for example, iron powder with an average circularity of 50 to 100, 70 to 95, or 80 to 90 may be used. Here, average circularity is one of the parameters that describe the shape of each iron particle contained in the iron powder. It is calculated by analyzing an image obtained by observing the iron powder under a microscope, determining the circularity of multiple iron particles, and averaging the results. For example, the circularity can be calculated by dividing the perimeter of a circle with an area equal to the area of ​​the projection surface of each iron particle in the microscope image by the perimeter of the projection surface of the iron particle. Alternatively, the circularity can be calculated by dividing the area of ​​the projection surface by the area of ​​a circle inscribed in the projection surface. The average particle size of the iron powder is also not limited; for example, it can be 20 μm to 500 μm or 50 μm to 200 μm. Here, the average particle size of the iron powder is calculated by analyzing an image obtained by observing the iron powder under a microscope, determining the particle sizes of multiple iron particles, and averaging the results. The particle size of each iron particle can be, for example, the diameter of a circle inscribed in the projection plane of each iron particle in the microscope image or the length of one side of a square.

[0028] The amount of porous carbide when mixed may be selected from the range of 20% by weight to 80% by weight, 40% by weight to 80% by weight, or 60% by weight to 80% by weight, based on the total weight of the porous carbide, binder, and iron powder. The amount of iron powder may be selected from the range of 5% by weight to 35% by weight, 5% by weight to 25% by weight, or 5% by weight to 20% by weight, based on the total weight of the porous carbide, binder, and iron powder. The amount of binder may be selected from the range of 5% by weight to 50% by weight, 15% by weight to 50% by weight, or 20% by weight to 50% by weight, based on the total weight of the porous carbide, binder, and iron powder.

[0029] The iron powder may be partially oxidized to include iron oxide or iron hydroxide on the surface.

[0030] The obtained iron-containing carbide may be appropriately granulated and molded into a certain shape. Molding can be carried out using a granulator. Examples of granulators include a compression granulator, an extrusion granulator, a roll granulator, a blade granulator, a melt granulator, and a spray granulator. For example, the iron-containing carbide may be molded into a pellet shape (e.g., a roughly cylindrical shape) using an extrusion granulator.

[0031] The iron-containing carbide may then be further dried. Drying is carried out at a temperature selected from the ranges of, for example, 30°C or higher but lower than 400°C, 50°C or higher but 300°C or lower, and 100°C or higher but 300°C or lower. The humidity during drying may be 20% or higher but 95% or lower, or 50% or higher but 90% or lower. The drying time may also be appropriately selected from the ranges of 1 minute or higher but 1 week or lower, 1 hour or higher but 3 days or lower, or 3 hours or higher but 1 day or lower. The atmosphere during drying may also be, for example, air, nitrogen, a rare gas such as argon, or a mixture of these.

[0032] 2-3. Preparation of iron phosphate-containing carbide Iron phosphate-containing carbide is prepared by contacting the iron-containing carbide obtained in the above steps with water containing phosphoric acid (hereinafter referred to as treated water). Treated water can be prepared by dissolving phosphates, such as sodium phosphate or potassium phosphate, in water. Alternatively, water from a body of water, such as a river, lake, or ocean, can be used as the treated water. For example, a container filled with iron-loaded carbide can be placed in a river, lake, or ocean, and the iron-loaded carbide can be brought into contact with the water. This allows the phosphoric acid present in the water from the river, lake, or ocean to react with the iron, iron oxide, and / or iron hydroxide contained in the iron-loaded carbide, resulting in iron(III) phosphate, which has low solubility in water, being adsorbed or supported on the porous carbide. At the same time, organic compounds containing phosphorus and phosphorus are removed from the water. This method not only enables the low-cost preparation of iron phosphate-containing carbide, but also allows for the purification and improvement of water quality in various bodies of water.

[0033] 2-4. Composting Subsequently, composting is carried out using the iron phosphate-containing carbide as one of the raw materials.

[0034] (1) Mixing iron phosphate-containing carbide with organic fertilizer sources First, the iron phosphate-containing carbide obtained by the above-described method is mixed with an organic fertilizer source. There are no restrictions on the amount of iron phosphate-containing carbide relative to the organic fertilizer source; for example, 10% to 40% by weight or 15% to 25% by weight of iron phosphate-containing carbide can be added to the organic fertilizer source. If the resulting mixture (primary mixture) has a high viscosity, additional water can be added to adjust the viscosity. Examples of organic fertilizer sources include readily decomposable organic matter of biological origin, such as animal feces and urine (e.g., cow, pig, or chicken), food waste (e.g., food residue), agricultural waste, food waste, and sludge. The amount of carbon dioxide generated after mixing with soil and the content of acid detergent-soluble organic matter (AD-soluble organic matter) can be used as indicators to determine whether a given organic matter is readily decomposable.

[0035] The amount of carbon dioxide generated from organic fertilizer sources can be quantified by adding water to a mixture of a specified amount of sample and soil, initiating incubation, and quantifying the amount of carbon dioxide generated during incubation. The generated carbon dioxide can be captured with an aqueous solution of sodium hydroxide, and barium chloride can be added to the mixture to precipitate barium carbonate, which can then be titrated with hydrochloric acid to quantify the amount of carbon dioxide. For example, if the amount of carbon dioxide generated by 10 days after the start of incubation is 200 mg or more, 300 mg or more, or 400 mg or more per gram of dried sample, the sample can be determined to be readily decomposable organic matter and usable as an organic fertilizer source for producing this compost.

[0036] To quantify AD-soluble organic matter, for example, a sample is boiled for 1 hour in an acid detergent solution (e.g., 20 g of cetyltrimethylammonium bromide dissolved in 1 L of 0.5 mol / L sulfuric acid) and then filtered. The residue is washed, dried, and weighed. The residue is then incinerated and weighed. The weight difference before and after incineration is calculated as the amount of acid detergent fiber (ADF). Since AD-soluble organic matter is organic matter other than ADF, the weight of the ADF and the incinerated residue is subtracted from the sample weight to calculate the AD-soluble organic matter. If the amount of AD-soluble organic matter obtained in this way is 500 mg or more, 600 mg or more, or 700 mg or more per gram of dried sample, the sample can be determined to be readily decomposable organic matter and usable as an organic fertilizer source for producing this compost.

[0037] However, in an embodiment of the present invention, the organic fertilizer source is not limited by the above-mentioned indicators and their numerical values, and any organic matter that can be decomposed by anaerobic microorganisms can be used as the organic fertilizer source.

[0038] The iron phosphate-containing carbide and the organic fertilizer source may be mixed in a closed chamber or in an open space. The primary mixture may have an average diameter of several centimeters to several tens of centimeters, or may be a mixture of several centimeters. 3 from several thousand cm 3 It is obtained as multiple blocks with a volume of about 10 ...

[0039] (2) Fermentation The primary mixture is then subjected to a fermentation treatment. Specifically, the primary mixture is first exposed to an oxygen-containing atmosphere. The oxygen-containing atmosphere may be air or an atmosphere containing oxygen and an inert gas such as nitrogen or argon. The fermentation treatment may be carried out at ambient temperature or in a temperature-controlled environment ranging from 30°C to 60°C. The fermentation treatment time can be set arbitrarily, for example, from 1 day to 120 days, from 10 days to 60 days, or from 15 days to 30 days. This treatment exposes the surface of each mass of the primary mixture to aerobic conditions and the interior to anaerobic conditions. As a result, aerobic fermentation proceeds on the surface of each mass, while anaerobic fermentation proceeds within the interior. Since aerobic fermentation proceeds only on the surface of each mass of the primary mixture, anaerobic fermentation proceeds throughout most of the primary mixture.

[0040] Anaerobic fermentation is promoted by the action of anaerobic microorganisms contained in the organic fertilizer source. Therefore, anaerobic microorganisms that promote the decomposition of organic matter may be added when mixing the iron phosphate-containing carbide with the organic fertilizer source. Examples of anaerobic microorganisms include nitrate-reducing bacteria, iron-reducing bacteria, sulfate-reducing bacteria, acid-producing bacteria, acetogenic bacteria, and methanogenic archaea. Iron-reducing bacteria and methanogenic archaea are preferred.

[0041] During this fermentation process, as organic matter decomposes during anaerobic fermentation, the interior of each block of the primary mixture becomes a reducing environment, resulting in a negative oxidation-reduction potential (ORP). Therefore, within the primary mixture, trivalent iron phosphate is reduced to divalent iron phosphate. Because divalent iron phosphate has a higher solubility in water than trivalent iron phosphate, at least a portion of the iron phosphate dissolves in the water contained in the primary mixture and dissociates into divalent iron ions and phosphate ions. For example, if the trivalent iron phosphate contained in iron-compound-containing carbides is FePO4, divalent iron phosphate Fe3(PO4)2 is produced. Furthermore, iron phosphate-containing carbides contain porous carbides derived from organic matter such as biomass, and therefore contain large amounts of alkali metal and alkaline earth metal ions. Similarly, organic fertilizer sources also contain large amounts of alkali metal and alkaline earth ions. These ions ionically bond with phosphate ions to produce soluble and insoluble phosphate. Additionally, proteins contained in organic fertilizer sources are decomposed into ammonia through anaerobic fermentation, resulting in the production of ammonium phosphate from ammonia, phosphate ions, and water.

[0042] (3) Treatment under aerobic conditions After the fermentation process, the interior of each lump of the primary mixture is treated under aerobic conditions. Specifically, each lump of the primary mixture is pulverized, and the interior is exposed to oxygen. The pulverization can be carried out in air or in an atmosphere containing oxygen and an inert gas such as nitrogen or argon. In this process, the divalent iron phosphate is rapidly oxidized by oxygen to produce iron(III) oxide and iron(III) hydroxide. Due to the low solubility of iron(III) oxide in water, the reaction between iron(III) oxide and phosphoric acid is largely negligible. The phosphate ions produced in the fermentation process ionically bond with alkali metal ions, alkaline earth ions, or ammonium ions to produce water-soluble and water-insoluble phosphoric acid.

[0043] 2-5. Sterilization treatment The above steps allow the production of a compost according to one embodiment of the present invention, but a sterilization treatment may be carried out subsequently. The sterilization treatment is preferably carried out by treating the compost in an oxidizing atmosphere. Treatment in an oxidizing atmosphere may be carried out, for example, by bringing an oxygen-containing gas (oxygen gas, air) into contact with the compost (aeration). At this time, ultraviolet light may also be irradiated onto the compost. This sterilization treatment can remove or reduce bacteria and microorganisms contained in the organic fertilizer source. Furthermore, the water content can be appropriately controlled by evaporating the water contained in the organic fertilizer source or water added separately, resulting in a compost that is easy to handle.

[0044] As mentioned above, anaerobic fermentation in the primary mixture reduces iron(III) phosphate to iron(II) phosphate, which dissolves in water and liberates phosphate ions. Meanwhile, ammonia is produced by the decomposition of organic fertilizer sources.

[0045] Under subsequent aerobic conditions, the ferrous iron ions are oxidized and precipitated as less soluble iron(III) oxide, suppressing the trapping of phosphate ions by the iron ions. Meanwhile, the primary mixture contains large amounts of alkali metal ions and alkaline earth metal ions derived from the organic matter and organic fertilizer sources used to make the porous carbon. Therefore, the phosphate ions liberated by anaerobic fermentation and the phosphoric acid generated by the equilibrium between phosphate ions and water combine with ammonia, alkali metal ions, and alkaline earth metal ions to produce large amounts of soluble phosphate, along with water-insoluble phosphate. As a result, the resulting compost functions as an excellent source of water-soluble phosphate and can contribute to plant growth as a fast-acting fertilizer.

[0046] 2-6. Other processes The resulting compost can be used alone as a fertilizer, or it can be mixed with a fertilizer aid containing the sulfur-, manganese-, or boron-containing compound described above. In this case, the fertilizer aid can be added so that the concentration of the sulfur-, manganese-, or boron-containing compound in the compost is, for example, 0.01% by weight to 1% by weight. Mixing can be performed using a mixer, which can be selected from a free-fall mixer, forced mixer, Y-branch mixer, agitator mixer, paddle mixer, etc.

[0047] The resulting compost may then be dried and molded. The compost may be molded into any desired shape, such as pellets, rods, granules, or powder. If necessary, the compost may be crushed or classified to adjust its particle size. For example, the compost may be crushed and classified so that the average particle size is 10 mm or less, or 0.1 mm to 10 mm. Crushing may be performed using a crusher, such as a vibrating mill, jet mill, ball mill, roller mill, rod mill, hammer mill, impact mill, rotary mill, pin mill, pin-disk mill, or planetary mill. Crushing the compost using a crusher increases the surface area, thereby facilitating the release of water-soluble phosphate into the soil. Classification may be performed using a classifier, which may be either a dry or wet type. Examples of classifiers include airflow classifiers, gravity field classifiers, inertial field classifiers, and centrifugal field classifiers.

[0048] The compost according to one embodiment of the present invention produced by the above-described method is rich in water-soluble phosphate, exhibits immediate effects comparable to chemical fertilizers, and can function as a fertilizer suitable for top dressing. Furthermore, because the main components, carbonized materials and organic fertilizer sources, are derived from natural resources, farming methods using this compost can also be recognized as a type of organic farming.

[0049] As described above, in a compost production method according to one embodiment of the present invention, the organic fertilizer source is not fermented alone, but rather in the presence of an iron phosphate-containing carbide. As shown in the examples, the coexistence of an iron phosphate-containing carbide, including a porous carbide, promotes the fermentation of the organic fertilizer source. This contributes to shortening the fermentation time and improving the compost production efficiency. Furthermore, this production method can reduce the amount of methane generated, which can be said to contribute to reducing greenhouse gas emissions.

[0050] Furthermore, charcoal, the main component of compost, can be obtained by carbonizing biomass. That is, charcoal is prepared by effectively utilizing plant-derived biomass produced by the fixation of carbon dioxide through photosynthesis. Furthermore, the water quality of various water systems can be improved during the compost production process, and by spreading this compost on soil, the carbon dioxide fixed by plants can be stored underground as charcoal.

[0051] More specifically, as shown in Figure 2, according to an embodiment of the present invention, biomass is carbonized to prepare porous charcoal (1), and iron-containing charcoal is then prepared from the porous charcoal (2). This iron-containing charcoal contributes to water purification when converted into iron phosphate-containing charcoal (3), and is then converted into compost containing porous charcoal derived from biomass through a series of processes including mixing with organic fertilizer sources, fermentation, and treatment under aerobic conditions (4). This compost is then spread on soil as a fast-acting fertilizer and used to grow plants (5). Plants fix carbon dioxide from the atmosphere through photosynthesis, providing food and structural materials, while also producing biomass as a by-product (6), which can be used as a raw material for charcoal.

[0052] This cycle, constructed through a series of processes (1) to (6), fixes atmospheric carbon dioxide as organic matter through photosynthesis, which is then used as food or materials, with biomass being produced as a by-product. The biomass is converted into charcoal through carbonization, and is ultimately spread into the ground as compost. Therefore, atmospheric carbon dioxide is stored in the ground as carbon, thereby contributing to the reduction of atmospheric carbon dioxide. Furthermore, by using carbonate as a base when producing this compost, carbon dioxide can be fixed as iron carbonate, further contributing to the reduction of atmospheric carbon dioxide. [Example]

[0053] In this example, the results of an investigation into the effect of iron phosphate-containing carbide in promoting the fermentation of organic fertilizer sources are described.

[0054] 1. Preparation of Iron Phosphate-containing Carbide Irregularly shaped charcoal (waste coal from woody biomass gasification power generation), iron powder, iron oxide powder, blast furnace slag powder as a binder, and water were mixed and kneaded at room temperature for 30 minutes to obtain a powder mixture. The resulting powder mixture was then placed in a granulator and formed into pellets with a diameter of 4 mm and a height of 10 mm. The formed powder mixture was then dried (cured) at 20°C for 24 hours to obtain iron-containing carbide.

[0055] The iron content in the iron-containing carbide was determined by extracting iron by treating the pulverized iron-containing carbide according to JIS K 1474, and measuring the extracted iron content with an inductively coupled plasma optical emission spectrometer (PerkinElmer, Optima 5300 DV). As a result, it was confirmed that the iron content of the iron-containing carbide was 10 wt % of the total weight.

[0056] The obtained iron-containing carbide was packed into a glass column, and sewage sludge dewatering filtrate containing 100 mg / L of phosphoric acid was passed through it at a flow rate of 23 L / day for 12 days. The sewage sludge dewatering filtrate used here was the filtrate obtained by centrifuging sludge at a sewage treatment plant in Kanagawa Prefecture. The obtained iron phosphate-containing carbide was then dried at room temperature for 24 hours to prepare iron phosphate-containing carbide.

[0057] 2. Fermentation Cow manure and food waste were used as the organic fertilizer source. In the examples, a primary mixture of the organic fertilizer source and iron phosphate-containing carbide (weight ratio: organic fertilizer source: iron phosphate-containing carbide = 3:1) was prepared, and this primary mixture was subjected to fermentation treatment in an insulated container under atmospheric pressure. In the comparative examples, the organic fertilizer source was subjected to fermentation treatment under the same conditions, but without the iron phosphate-containing carbide. Figure 3 shows a plot of the temperatures of the primary mixture and the organic fertilizer source during fermentation treatment.

[0058] As shown in Figure 3, the fermentation temperature was higher when iron phosphate-containing carbide was added to all organic fertilizer sources, clearly demonstrating that iron phosphate-containing carbide promotes the fermentation of organic fertilizer sources.

[0059] 3. Water-soluble phosphate concentration For the above-mentioned Examples and Comparative Examples, which used cow manure as an organic fertilizer source, the total phosphate concentration and water-soluble phosphate concentration were measured using ammonium vanadomolybdate absorptiometry. The results are shown in Figure 4. As shown in Figure 4, the concentration of water-soluble phosphate relative to total phosphate increased in both the Examples and Comparative Examples due to fermentation treatment, but the increase in water-soluble phosphate was greater in the Examples (approximately 130%) than in the Comparative Examples. Furthermore, the concentration of water-soluble phosphate in the fermented compost of the Examples was 1.62 times that of the Comparative Examples. These results demonstrate that application of an embodiment of the present invention enables more efficient production of water-soluble phosphate by fermenting organic fertilizer sources, providing compost rich in water-soluble phosphate that can be used by plants.

[0060] The above-described embodiments of the present invention may be combined as appropriate as long as they are not mutually inconsistent. A product in which a person skilled in the art appropriately adds or deletes components or modifies the design based on each embodiment is also included within the scope of the present invention as long as it includes the gist of the present invention.

[0061] Even if there are other effects and advantages different from those brought about by the above-described embodiments, those that are clear from the description in this specification or that can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention.

Claims

1. A first step of mixing carbide and iron powder to prepare an iron-containing carbide; a second step of preparing an iron phosphate-containing carbide by contacting the iron-containing carbide with water containing phosphoric acid; a third step of mixing the iron phosphate-containing carbide with an organic fertilizer source to prepare a mixture; a fourth step of simultaneously treating the surface of the mixture under aerobic conditions and the interior under anaerobic conditions; and A method for producing compost, comprising a fifth step of treating the interior of the mixture treated under anaerobic conditions under aerobic conditions.

2. The fourth step is carried out by exposing the mass of the mixture to an atmosphere containing oxygen; The method of claim 1 , wherein the fifth step is carried out by crushing the mass and contacting the interior with oxygen.

3. 10. The method of claim 1, wherein the organic fertilizer source comprises at least one of animal manure and food waste.

4. Porous carbide, Water-soluble phosphate, water-insoluble phosphoric acid, and containing iron(III) oxide and / or iron(III) hydroxide, A compost in which the ratio of the water-soluble phosphoric acid to total phosphoric acid is 30% or more and 70% or less.

5. 5. The compost of claim 4, further comprising iron.

6. 5. The compost according to claim 4, wherein the total phosphoric acid is contained at a concentration of 1% by weight or more and 21% by weight or less.

7. 5. The compost according to claim 4, containing the porous carbonized material in an amount of 2% by weight or more and 20% by weight or less.

8. Porous carbide, Water-soluble phosphate, water-insoluble phosphoric acid, and containing iron(III) oxide and / or iron(III) hydroxide, The water-soluble phosphoric acid includes ammonium phosphate and potassium phosphate, The compost, wherein the water-insoluble phosphoric acid comprises calcium phosphate.

9. The compost described in claim 8, further containing iron.

10. A compost as described in claim 8, containing total phosphoric acid at a concentration of 1% by weight or more and 21% by weight or less.

11. Compost as described in claim 8, containing the porous carbonized material in a proportion of 2% by weight or more and 20% by weight or less.

Images