compost

Abstract

To provide compost and a method for producing the same.SOLUTION: The compost includes carbide, water-soluble phosphate, and at least one of iron(III) oxide, iron(III) carbonate, and iron(III) hydroxide. The compost may contain total phosphoric acid at a concentration of 1 wt.% or more and 21 wt.% or less, and the ratio of water-soluble phosphoric acid to the total phosphoric acid may be 30% or more and 70% or less. A method of producing the compost includes: preparing a mixture by mixing a carbide containing iron(III) phosphate with an organic fertilizer source, treating the mixture under anaerobic conditions, and mixing the anaerobically treated mixture with a base.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Animal waste, such as that from livestock, 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, and manganese oxide. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2012-180266 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] One embodiment of the present invention aims to provide compost and a method for producing the same. For example, one embodiment of the present invention aims to provide compost having a novel composition and a method for producing the same. Alternatively, one embodiment of the present invention aims to provide compost rich in fast-acting water-soluble phosphorus 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. This method includes preparing a mixture by mixing a carbonized material containing iron(III) phosphate with an organic fertilizer source, treating the mixture under anaerobic conditions, and mixing the mixture treated under anaerobic conditions with a base.

[0006] One embodiment of the present invention is compost. This compost comprises carbonized material, water-soluble phosphoric acid, and at least one of iron(III) oxide, iron(III) carbonate, and iron(III) hydroxide. [Brief explanation of the drawing]

[0007] [Figure 1] A flowchart illustrating a method for producing compost according to one embodiment of the present invention. [Figure 2] A schematic diagram of a manufacturing apparatus for producing compost according to one embodiment of the present invention. [Figure 3] A conceptual diagram showing carbon dioxide storage using a composting method according to one embodiment of the present invention. [Modes for carrying out the invention]

[0008] The embodiments of the present invention will be described below with reference to the drawings and other materials. However, the present invention can be implemented in various forms without departing from its spirit, and is not to be interpreted as being limited to the embodiments described below.

[0009] While drawings may schematically represent the width, thickness, shape, etc., of each part compared to the actual embodiment in order to clarify the explanation, they are merely examples and do not limit the interpretation of the present invention.

[0010] In this specification, the term "phosphate" refers not only to phosphate in the narrow sense, i.e., compounds represented by the chemical formula H3PO4, but also to various phosphates, monohydrogen phosphates, and dihydrogen phosphates in addition to phosphate (H3PO4). Therefore, for example, iron phosphate, unless otherwise specified, refers not only to iron phosphate but also to monohydrogen phosphate and dihydrogen phosphate, and the iron ions contained may be divalent or trivalent.

[0011] 1. Compost A compost according to one embodiment of the present invention contains charcoal, water-soluble phosphoric acid, and at least one iron compound selected from iron(III) oxide, iron(III) carbonate, and iron(III) hydroxide. In addition to water, other components may include water-insoluble phosphoric acid (for example, phosphoric acid that is insoluble in water but soluble in a 2% citric acid aqueous solution (citric acid-soluble phosphoric acid)), sulfur-containing compounds, manganese-containing compounds, boron-containing compounds, and fibrous materials contained in the organic fertilizer source that is the raw material for the compost. Each of these components will be described below.

[0012] 1-1. Carbides Carbides are porous materials that primarily consist of carbon and have pores with cross-sectional diameters ranging from a few nanometers to tens of micrometers. The specific gravity of carbides is 0.05 g / cm³. 3 More than 0.8g / cm 3 The following, or 0.1 g / cm³ 3 More than 0.5g / cm 3 The following is also possible: The char may contain zero-valent iron, or it may contain divalent or trivalent iron compounds such as iron phosphate, iron chloride, iron sulfate, iron nitrate, iron oxide, and iron bromide. These irons and iron compounds are contained in the char in the form of adsorption or support on the surface or within the pores of the char. There is no limit to the proportion of char contained in this compost, but for example, it may be 2% by weight or more and 40% by weight or 5% by weight or more and 35% by weight or less.

[0013] 1-2. Water-soluble phosphoric acid Examples of water-soluble phosphoric acids include phosphates such as lithium phosphate, sodium phosphate, potassium phosphate, and ammonium phosphate; hydrogen phosphates such as lithium hydrogen phosphate, sodium hydrogen phosphate, potassium hydrogen phosphate, and ammonium hydrogen phosphate; and dihydrogen phosphates such as lithium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate. Typically, alkali metal phosphates such as sodium phosphate and potassium phosphate, and alkali metal hydrogen phosphates such as sodium hydrogen phosphate and potassium hydrogen phosphate are mentioned. These water-soluble phosphoric acids are contained in this compost at a relatively high concentration. Specifically, they may be contained at a concentration of 30% or more and 70% or less, 40% or more and 60% or less, or 40% or more and 50% or less with respect to the total phosphoric acid in this compost. Note that the total phosphoric acid refers to the whole of water-soluble phosphoric acid and water-insoluble phosphoric acid, and is contained, for example, at a concentration of 1% by weight or more and 21% by weight or less, or 5% by weight or more and 15% by weight or less in this compost.

[0014] The concentration of water-soluble phosphoric acid can be determined, for example, using the ammonium vanadomolybdate spectrophotometric method. In this method, for example, water is added to the compost, and a predetermined amount of the water-soluble portion is taken as a sample. Nitric acid (1+1) is added to this sample and heated to hydrolyze non-orthophosphoric acid into orthophosphate ions. Then, ammonium vanadate (V), hexammonium heptamolybdate, and nitric acid are added to form ammonium phosphovanadomolybdate. The water-soluble phosphoric acid is quantified by measuring the absorption of ammonium phosphovanadomolybdate (for example, the absorption at 420 nm) using an ultraviolet-visible spectrophotometer.

[0015] For the quantification of total phosphoric acid, the ammonium vanadomolybdate spectrophotometric method can be used. For example, a predetermined amount of the compost is decomposed using nitric acid or perchloric acid, and then ammonium vanadate (V), hexammonium heptamolybdate, and nitric acid are added. The total phosphoric acid is quantified by measuring the absorption of the resulting ammonium phosphovanadomolybdate (for example, the absorption at 420 nm) using an ultraviolet-visible spectrophotometer.

[0016] 1-3. Iron compounds The iron compound contains at least one of iron(III) oxide, iron(III) carbonate, and iron(III) hydroxide. The iron compound may be composed of a single compound or may be a mixture. In the compost, a part of the iron compound may be adsorbed or supported on the carbide, and another part may exist in a free state from the carbide. The iron compound may be contained in the compost at a concentration of 0.1% by weight or more and 10% by weight or less.

[0017] 1-4. Other components Examples of the above-mentioned water-insoluble phosphoric acids include calcium hydrogen phosphate, calcium dihydrogen phosphate, calcium phosphate, magnesium hydrogen phosphate, magnesium phosphate, and the like. These water-insoluble phosphoric acids are, for example, compounds supported or adsorbed on the carbide used as a raw material in the compost manufacturing process described later, and / or derived from an organic fertilizer source.

[0018] Examples of the sulfur-containing compounds include sulfates of alkali metals and alkaline earth metals. Examples of the manganese-containing compounds include manganese salts such as manganese sulfate, manganese nitrate, manganese chloride, manganese carbonate, and manganese borate. Examples of the boron-containing compounds include boric acid in addition to the above-mentioned manganese borate. The concentration of each 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.

[0019] As described above, since the compost contains water-soluble phosphoric acid at a relatively high concentration, the compost can function as a fertilizer with immediate effect on plant growth. In addition, the compost contains a carbide which is a porous material. Such a carbide not only improves the moisture retention of the soil but also functions as a bioreactor, and can supply nutrients, moisture, oxygen, etc. to the soil in a balanced manner by microanimals and microorganisms symbiotic in the pores. Therefore, the compost can also contribute to soil improvement.

[0020] 2. Method for producing compost The following describes a method for producing this compost according to one embodiment of the present invention. The flow chart of this production method is shown in Figure 1.

[0021] 2-1. Carbides (1) Preparation of carbonized materials by carbonization of biomass First, carbonized material is prepared. Specifically, organic matter such as biomass is heated at a low oxygen concentration. Here, biomass is a type of organic matter, consisting of living organisms and their metabolites. Examples of biomass that can be used in the preparation of carbonized material include wood-derived materials. Specifically, this includes plank or columnar timber, thinned wood, pruning waste, construction waste wood, powdered sawdust, and wooden molded products such as particleboard. There are no restrictions on the type of wood; cedar, cypress, or bamboo are also acceptable. Alternatively, agricultural waste such as rice husks, bagasse, corn cobs and leaves, and agricultural by-products such as straw, wheat straw, and hay can also be cited as examples of biomass. Plants that are raw materials for fibers such as hemp, flax, cotton, sisal, abaca, and coconut hair can also be cited as biomass. Alternatively, biomass can also be algae such as seaweed, food waste, or silage obtained from animal manure.

[0022] (2) Supporting iron compounds on carbides Next, iron compounds are adsorbed or supported onto the surface or within the pores of the carbide obtained by carbonizing biomass. Specifically, the carbide is immersed in a solution or suspension containing iron compounds under normal or reduced pressure to adsorb or support the iron compounds onto the carbide. Typical examples of iron compounds include iron(II) sulfate, iron(III) sulfate (including polyferrous sulfate), iron(II) nitrate, iron(III) nitrate, iron(II) chloride, iron(III) chloride, iron(II) oxide, iron(III) oxide, iron(II) bromide, iron(III) bromide, iron(II) carbonate, and iron(III) carbonate.

[0023] Next, the carbide on which the iron compound is adsorbed or supported is heated. The heating temperature can be appropriately selected within the range of 100°C to 900°C, 500°C to 800°C, or 600°C to 750°C. The water is removed by heating, and the iron compound-supported carbide is obtained.

[0024] The heating of the carbide after immersion may be carried out under a reducing gas atmosphere such as hydrogen or carbon monoxide. As a result, some of the iron compounds may be reductively thermally decomposed to become zero-valent iron metal, while some of the iron compounds will be adsorbed or supported on the surface or within the pores of the carbide as divalent or trivalent iron compounds, or mixtures thereof.

[0025] The iron content in the iron-supported carbide can be adjusted by adjusting the immersion and heating conditions so that it is between 1% and 50% by mass, 3% and 30% by mass, 5% and 25% by mass, or 10% and 25% by mass relative to the iron-supported carbide. The iron contained in the iron-supported carbide can be quantified, for example, using an inductively coupled plasma mass spectrometer (ICP-MS).

[0026] (3) Preparation of carbides containing iron phosphate Next, the iron compound-supported carbide is brought into contact with water containing phosphate (hereinafter referred to as treated water) to prepare iron phosphate-containing carbide. The treated water may be prepared by dissolving phosphates such as sodium phosphate or potassium phosphate in water, but water from rivers, lakes, or the sea may also be used as treated water. For example, a container filled with iron compound-supported carbide may be placed in a river, lake, or the sea, and the iron compound-supported carbide may be brought into contact with the water in the body. As a result, the phosphate contained in the water of rivers, lakes, or the sea reacts with the iron compound on the iron compound-supported carbide, and is adsorbed or supported on the carbide as iron(III) phosphate, which has low solubility in water, and at the same time, phosphate and phosphorus-containing organic compounds in the water are removed. In other words, this method not only allows for the preparation of iron phosphate-containing carbide at low cost, but also enables water purification and water quality improvement in various water bodies at the same time.

[0027] 2-2. Composting We will continue using iron phosphate-containing carbonized material as one of the raw materials for composting.

[0028] (1) Mixing with organic fertilizer sources First, the iron phosphate-containing char obtained by the method described above is mixed with an organic fertilizer source. There are no restrictions on the amount of iron phosphate-containing char relative to the organic fertilizer source, but for example, 10% to 40% or 15% to 25% by weight of iron phosphate-containing char should be added to the organic fertilizer source. If the viscosity of the resulting mixture (primary mixture) is high, water may be added to adjust the viscosity. Examples of organic fertilizer sources include easily decomposable organic matter of biological origin, such as animal manure and urine such as cow manure, pig manure, and chicken manure, food waste such as food residues, agricultural waste, kitchen waste, and sludge. To determine whether or not an organic matter is easily decomposable, for example, the amount of carbon dioxide generated after mixing with soil or the content of acid detergent-soluble organic matter (AD-soluble organic matter) can be used as indicators.

[0029] The amount of carbon dioxide generated from an organic fertilizer source can be quantified by adding water to a predetermined amount of sample and soil mixture, starting a culture, and then quantifying the carbon dioxide generated during the culture. The generated carbon dioxide can be collected with an aqueous sodium hydroxide solution, and then barium chloride can be added to precipitate it as barium carbonate. The carbon dioxide can then be quantified by titrating the barium carbonate with hydrochloric acid. For example, if the amount of carbon dioxide generated within 10 days from the start of the culture is 200 mg or more, 300 mg or more, or 400 mg or more per gram of dry sample, then this sample can be determined to be easily decomposable organic matter and usable as an organic fertilizer source for producing this compost.

[0030] The quantification of AD-soluble organic matter can be performed by, for example, boiling the sample in an acidic detergent solution (e.g., a solution of 20 g of cetyltrimethylammonium bromide dissolved in 1 L of 0.5 mol / L sulfuric acid) for 1 hour and filtering. The residue is washed, dried, and weighed. Then, the residue is ashed and weighed, and the weight difference from before ashing is determined as the amount of acid detergent fiber (ADF). Since AD-soluble organic matter is organic matter other than ADF, the amount of AD-soluble organic matter is calculated by subtracting the weight of ADF and the weight of the residue after ashing from the weight of the sample. 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, then the sample can be determined to be easily decomposable organic matter and usable as an organic fertilizer source for producing this compost.

[0031] However, in the embodiments of the present invention, the organic fertilizer source is not limited by the indicators or their numerical values ​​described above, and any organic matter that can be decomposed by anaerobic microorganisms can be used as an organic fertilizer source.

[0032] The mixing of iron phosphate-containing char and organic fertilizer source can be carried out in a sealed chamber or a chamber capable of maintaining anaerobic conditions, and there are no restrictions on the configuration or shape of the chamber. For example, as shown in Figure 2, the iron phosphate-containing char and organic fertilizer source are introduced into a chamber 100 equipped with a hopper 104. A screw feeder 106 may be provided between the hopper 104 and the chamber 100 to transport the iron phosphate-containing char and organic fertilizer source to the chamber 100. To promote decomposition by anaerobic microorganisms, the chamber 100 may be configured to rotate, or a stirrer 102 may be provided inside the chamber. The chamber 100 may be configured to be sealed to block out outside air. Although not shown, one or more openings may be provided in the chamber 100 for adding water or for replacing the gas inside the chamber 100. Furthermore, if an anaerobic environment is maintained, it is not necessarily required to mix the iron phosphate-containing char and organic fertilizer source inside the chamber. For example, iron phosphate-containing carbonized material and organic fertilizer sources may be piled up and fermented, creating an anaerobic environment inside.

[0033] (2) Anaerobic treatment Subsequently, the primary mixture obtained by mixing iron phosphate-containing carbonized material with an organic fertilizer source is treated under anaerobic conditions to decompose the organic matter contained in the organic fertilizer source. This anaerobic treatment may be carried out in chamber 100 or in a chamber different from chamber 100. The anaerobic treatment may be carried out by the action of anaerobic microorganisms contained in the organic fertilizer source, but anaerobic microorganisms may be added separately to promote the decomposition of organic matter. Examples of anaerobic microorganisms include nitrate-reducing bacteria, iron-reducing bacteria, sulfate-reducing bacteria, acid-producing bacteria, acetic acid-producing bacteria, and methane-producing archaea, with iron-reducing bacteria and methane-producing archaea being preferred. The anaerobic treatment may be carried out at the temperature of the external environment in which chamber 100 is placed, or while heating using a heater (not shown). If heating is used, the temperature should be, for example, 30°C to 60°C. The duration of the anaerobic treatment can also be set arbitrarily, for example, from a range of 1 day to 120 days, 10 days to 60 days, or 15 days to 30 days.

[0034] In this anaerobic treatment, the decomposition of organic matter creates a reducing environment inside chamber 100, causing the oxidation-reduction potential (ORP) of the primary mixture to become negatively large. As a result, trivalent iron phosphate is reduced to divalent iron phosphate. Therefore, if iron-reducing bacteria that utilize trivalent iron compounds as electron acceptors are present, these bacteria will reduce the trivalent iron phosphate in the iron compound-containing char to divalent iron phosphate. Since divalent iron phosphate has 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 in the iron compound-containing char is FePO4, divalent iron phosphate Fe3(PO4)2 is produced.

[0035] (3) Addition of base Next, the anaerobically treated primary mixture is mixed with a base. As the base, a base can be used in which an anion that combines with trivalent iron ions to give an iron compound with low solubility in water, and a cation that combines with phosphate ions to give soluble phosphate, are ionically bonded. Specifically, examples include alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates. The base may be added as an aqueous solution or in solid form. Upon addition of the base, ion exchange occurs, and the divalent iron ions and phosphate ions dissociated by the anaerobic treatment ionically bond with the anion and cation of the base, respectively. For example, when an alkali metal hydroxide is used as the base, an alkali metal salt of phosphate is produced, along with divalent iron hydroxide. When an alkali metal carbonate or bicarbonate is used as the base, an alkali metal salt of phosphate is produced, along with divalent iron carbonate and iron bicarbonate, respectively.

[0036] The addition of the base may be carried out in the chamber 100 in which the organic fertilizer source and the iron compound-containing carbide are mixed, or it may be carried out in a chamber different from chamber 100. For example, as shown in Figure 2, the primary mixture may be transported to chamber 110 connected to chamber 100 via a valve 108 such as a rotary valve, and the base may be added to chamber 110. Although not shown, chambers 100 and 110 do not have to be connected to each other. Similar to chamber 100, chamber 110 may also be equipped with a hopper 112 and a stirrer 114, and a screw feeder (not shown) may also be provided. The mixture obtained after mixing with the base (secondary mixture) can be removed from chamber 110 using a valve 116 such as a rotary valve.

[0037] Furthermore, the anaerobic treatment described in (2) and the addition of the base described in (3) may be carried out simultaneously. For example, a base may be added to a primary mixture obtained by mixing iron phosphate-containing charcoal and an organic fertilizer source, and then the mixture may be treated under anaerobic conditions to decompose the organic matter contained in the organic fertilizer source. Alternatively, the iron phosphate-containing charcoal, the organic fertilizer source, and the base may be mixed, and then the mixture may be treated under anaerobic conditions to decompose the organic matter contained in the organic fertilizer source.

[0038] (4) Sterilization By following the steps described above, compost according to one embodiment of the present invention can be produced, but a sterilization treatment may be carried out thereafter. 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 contained in the organic fertilizer source, or separately added water, can be evaporated to appropriately control the moisture content, and as a result, compost that is easy to handle can be obtained.

[0039] As described above, the phosphate ions released from divalent iron phosphate produced by anaerobic treatment react with the cations of the added base to give alkali metal phosphates, monohydrogen phosphates, and dihydrogen phosphates. Since these salts are water-soluble, the compost according to one embodiment of the present invention functions as an excellent source of water-soluble phosphate and can contribute to plant growth as a fast-acting fertilizer.

[0040] On the other hand, iron(II) ions released from divalent iron phosphate produced by anaerobic treatment react with base anions to produce divalent iron compounds (such as iron(II) hydroxide, iron(II) carbonate, and iron(II) bicarbonate). These divalent iron compounds are rapidly oxidized by oxygen contained in the primary or secondary mixture, or by oxygen in the oxidizing atmosphere during sterilization, to form trivalent iron compounds (such as iron(III) hydroxide, iron(III) carbonate, and iron(III) oxide). For example, iron(II) bicarbonate present in water is also oxidatively decomposed to yield iron(III) hydroxide. Because these trivalent iron compounds have low solubility in water, they precipitate in the compost. Therefore, the frequency factor of the reaction (ion exchange) between the precipitated trivalent iron compounds and water-soluble phosphate is extremely small, and these reactions are very slow. As a result, water-soluble phosphate is hardly lost due to the precipitated trivalent iron compounds, and this compost can maintain its function as a fast-acting fertilizer.

[0041] (5) Other processes The resulting compost may be used alone as fertilizer, or it may be used after being mixed with a fertilizer additive containing the aforementioned sulfur-containing compounds, manganese-containing compounds, or boron-containing compounds. In this case, the fertilizer additive should be added so that the concentration of the sulfur-containing compounds, manganese-containing compounds, or boron-containing compounds in the compost is, for example, between 0.01% by weight and 1% by weight. Mixing can be done using a mixer, which can be arbitrarily selected from free-fall mixers, forced mixers, Y-branch mixers, agitator mixers, or paddle mixers.

[0042] Furthermore, the obtained compost may be dried and shaped. For shaping, the compost can be processed into any shape, such as pellets, rods, granules, or powder. If necessary, crushing and classification may be performed to adjust the particle size of the compost. 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 can be done using a crusher, such as a vibratory mill, jet mill, ball mill, roller mill, rod mill, hammer mill, impact mill, rotary mill, pin mill, pin-disc mill, or planetary mill. Crushing the compost using a crusher increases the surface area, which in turn promotes the leaching of water-soluble phosphate into the soil. Classification is performed using a classifier, and either a dry classifier or a wet classifier may be used. Examples of classifiers include airflow classifiers, gravity field classifiers, inertial force field classifiers, and centrifugal force field classifiers.

[0043] The compost produced by the method described above, according to one embodiment of the present invention, is rich in water-soluble phosphorus, and therefore exhibits a rapid effect comparable to chemical fertilizers, making it suitable as a top dressing fertilizer. Furthermore, since the main components, carbonized material and organic fertilizer sources, are derived from natural resources, the farming method using this compost can be recognized as a type of organic farming.

[0044] Furthermore, the main component, carbonized material, can be obtained by carbonizing biomass. In other words, carbonized material is prepared by effectively utilizing biomass derived from plants, which is produced by the fixation of carbon dioxide through photosynthesis. Moreover, the process of manufacturing compost using this carbonized material can improve the water quality of various water systems, and by spreading this compost on the soil, carbon dioxide fixed by plants can be stored in the ground as carbonized material.

[0045] More specifically, as shown in Figure 3, according to each embodiment of the present invention, biomass is carbonized to prepare charred material (1), and further charred material with an iron compound supported is prepared from the charred material (2). This iron compound-supported charred material contributes to water purification when it is converted into iron phosphate-containing charred material (3), and is converted into compost containing biomass-derived charred material through a series of processes including mixing with an organic fertilizer source, anaerobic treatment, and mixing with a base (4). This compost is spread on the soil as a fast-acting fertilizer and used for plant growth (5). Plants fix carbon dioxide from the atmosphere through photosynthesis, providing food and structural materials, and also produce biomass as a by-product that can be used as raw material for charred material (6).

[0046] The cycle established by this series of processes from (1) to (6) fixes atmospheric carbon dioxide as organic matter through photosynthesis, and this organic matter is used as food and materials, while biomass is produced as a by-product. The biomass is converted into carbonized material through carbonization and is ultimately spread into the soil as compost. Therefore, atmospheric carbon dioxide is stored in the soil 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, making an even greater contribution to the reduction of atmospheric carbon dioxide. [Examples]

[0047] 1. Preparation of iron phosphate-containing carbides 400 g of charred material obtained by carbonizing cedar wood was immersed in 10 L of an aqueous solution of ferric(II) polysulfate (iron content 11%) at a gauge pressure of -0.09 MPa (normal atmospheric pressure is considered zero) at room temperature for 10 minutes. The charred material was then dried at 105°C for 24 hours, and further heated at 900°C for 1 hour in the presence of nitrogen and carbon monoxide gas to obtain iron-supported charred material. The iron content in the iron-supported charred material was determined by extracting iron from the pulverized iron-supported charred material according to JIS K 1474, and then measuring the extracted iron content using an inductively coupled plasma atomic emission spectrometer (PerkinElmer Optima 5300 DV). The results confirmed that the iron-supported charred material contained 21% by weight of iron relative to its total volume.

[0048] A column packed with 2 kg of iron compound-supported carbide was passed through which sewage sludge dewatering filtrate was passed at a flow rate of 2 L / day for 4 days. The sewage sludge dewatering filtrate used here was the filtrate obtained by centrifuging sludge at a sewage treatment plant in Kanagawa Prefecture. Subsequently, the resulting iron phosphate-containing carbide was dried at 105°C for 8 hours. 2. Example 1 This example describes the results of treating iron phosphate-containing carbide under anaerobic conditions. 2-1. Experiment 40 mL of water, 5 g of iron phosphate-containing charcoal, and 2 g of paddy field soil were added to a 200 mL polypropylene container. Furthermore, 1 g of dog feed (Pedigree®, manufactured by MARS) was added as an organic fertilizer source, and the resulting primary mixture was stirred. Subsequently, 1 g of organic fertilizer source was added daily, and stirring continued for 13 days. The total amount of organic fertilizer source was 13 g. As Comparative Example 1, a similar experiment was conducted using 2 g of charcoal produced as a by-product of a gasification power generation device and 1.5 g of iron(III) phosphate (iron(III) phosphate n-hydrate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) instead of iron phosphate-containing charcoal.

[0049] The pH of the obtained primary mixture was measured using a pH meter (metric type JF25 manufactured by HORIBA), and the oxidation-reduction potential ORP was measured using a glass electrode type hydrogen ion concentration indicator D-52 manufactured by HORIBA. The total iron content and the iron content in the water-soluble part were measured in the same manner as the measurement of the iron content of the iron compound-supported carbide. For the measurement of the total iron content, a sample sampled with the primary mixture stirred uniformly was used. On the other hand, for the measurement of the iron content in the water-soluble part, the mixture was filtered, and the obtained filtrate was used as a sample.

[0050] 2-2. Results and Discussion The measurement results of the primary mixture are shown in Table 1. As shown in Table 1, there is no significant difference in pH and ORP between Example 1 and Comparative Example 1. The initial pH of the primary mixture in Example 1 and Comparative Example 1 is 9.1 and 9.2, respectively. Compared with these initial pH values, the pH after 13 days has decreased significantly. This result means that a reducing environment is obtained by the action of anaerobic microorganisms contained in the paddy soil used in Example 1 and Comparative Example 1. Here, when comparing the weight ratio (W Fe / T Fe ) of iron in the water-soluble part to total iron, it can be seen that Example 1 is extremely high compared to Comparative Example 1. The low W Fe / T Fe in Comparative Example 1 is considered to be because iron(III) phosphate derived from the reagent has a strong binding force between iron ions and phosphate ions and hardly dissolves in the primary mixture. On the other hand, the high W Fe / T Fe obtained in Example 1 is considered to be because the iron(III) phosphate supported on the carbide was formed by binding at room temperature, so the binding force between iron ions and phosphate ions is weak and the solubility is high.

Table 1

[0051] The above results suggest that, due to the action of anaerobic microorganisms, the reduction of iron(III) phosphate proceeds rapidly in the primary mixture of iron phosphate-containing carbide and organic fertilizer source, and iron(II) phosphate soluble in water is efficiently generated.

[0052] 3. Example 2 This example describes the results of treating a primary mixture of iron phosphate-containing char and an organic fertilizer source under anaerobic conditions, followed by mixing in a base.

[0053] 3-1. Experiment The primary mixture was treated under anaerobic conditions for 13 days in the same manner as in Example 1. After this, sodium carbonate was added to the primary mixture and stirred for 24 hours. The amount of sodium carbonate added was varied to 4.5 g, 9.0 g, and 22.5 g to obtain the secondary mixtures of Examples 2 to 4, respectively.

[0054] pH, ORP, total iron content, and water-soluble iron content were measured in the same manner as in Example 1. Total phosphate concentration and water-soluble phosphate concentration were both measured by ammonium vanadomolybdate spectrophotometric analysis. A Shimadzu UV-2600 ultraviolet-visible spectrophotometer was used.

[0055] 3-2. Results and Discussion The analysis results are shown in Table 2. As shown in Examples 2 to 4 in Table 2, by adding sodium carbonate, the weight ratio of iron in the water-soluble portion to the total amount of iron (W Fe / T Fe The amount tends to increase. This is thought to be because the addition of sodium carbonate generates carbon dioxide in the secondary mixture, promoting the anaerobic reaction, which in turn promotes the reduction of iron and increases the amount of iron(II) ions in the water-soluble portion.

[0056] Weight ratio of water-soluble phosphoric acid to total phosphoric acid in the secondary mixture W p / T p This increases as the amount of base added increases. Also, in Comparative Example 2, where no base was added, W p / T p The level is extremely low. This indicates that phosphate ions derived from water-soluble iron(II) phosphate produced by treatment under anaerobic conditions ionically bond with alkali metal ions contained in the base and exist as water-soluble sodium phosphate in the secondary mixture. [Table 2]

[0057] The above results indicate that when a mixture of carbonized material containing iron phosphate and an organic fertilizer source is treated under anaerobic conditions and then mixed with a base containing an alkali metal as a cation, ion exchange between the iron(II) phosphate produced under anaerobic conditions and the base proceeds, resulting in the production of water-soluble phosphoric acid (alkali metal phosphate). From this, it can be understood that compost rich in water-soluble phosphoric acid can be produced by applying the manufacturing method according to one embodiment of the present invention.

[0058] The embodiments described above as examples of the present invention can be combined and implemented as appropriate, insofar as they do not contradict each other. Additions, deletions, or design modifications of components based on these embodiments, made by those skilled in the art, are also included within the scope of the present invention, as long as they retain the essence of the invention.

[0059] Any effects or benefits other than those brought about by the embodiments described above, if they are clear from the description herein or easily predictable to those skilled in the art, are naturally understood to be brought about by the present invention. [Explanation of Symbols]

[0060] 100: Chamber, 102: Agitator, 104: Hopper, 106: Screw feeder, 108: Valve, 110: Chamber, 112: Hopper, 114: Agitator, 116: Valve

Claims

1. carbide, Water-soluble phosphoric acid, and Compost containing iron(III) carbonate.

2. The compost according to claim 1, wherein it contains total phosphorus at a concentration of 1% by weight or more and 21% by weight or less.

3. The compost according to claim 2, wherein the ratio of the water-soluble phosphoric acid to the total phosphoric acid is 30% or more and 70% or less.

4. The compost according to claim 1, comprising the aforementioned carbonized material in a proportion of 2% by weight or more and 20% by weight or less.

5. The compost according to claim 1, further comprising at least one of a sulfur-containing compound, a manganese-containing compound, and a boron-containing compound.

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