JP2023125168A - compost - Google Patents

Abstract

To provide a compost in which an odor is depressed and a manufacturing method thereof.SOLUTION: A compost includes carbide, phosphorus, iron, and ammonia-oxidizing archaebacteria. In the compost, the total phosphate concentration is 2.0 wt.% or more and 5.0 wt.% or less, the iron concentration is 0.4 wt.% or more and 6.0 wt.% or less, and the number of the ammonia-oxidizing archaebacteria is 0.04% or more and 0.10% or less of the total number of bacteria. The carbide concentration may be 2 wt.% or more and 40 wt.% or less. The specific surface of the carbide may be 100 m2/g or more and 900 m2/g or less.SELECTED DRAWING: Figure 1

Description

One embodiment of the present invention relates to compost. For example, one embodiment of the present invention relates to a compost in which odor generation is significantly suppressed and a method for producing the same.

Organic waste of biological origin, such as food waste, excrement from animals such as livestock, and food residue, can be used as raw materials for compost. For example, Patent Document 1 discloses that compost can be obtained by mixing nitrogen-containing organic waste, activated carbon, and fermentation bacteria that decompose ammonia. Patent Document 2 discloses that compost can be obtained by mixing nitrogen-containing organic waste with a microorganism having a denitrifying function and a fermentation promoter.

Japanese Patent Application Publication No. 2005-145769 International Publication No. 2007/114324

One of the embodiments of the present invention aims to provide a compost and a method for producing the same. Alternatively, one of the objects of an 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 with suppressed odor and a method for producing the same.

One embodiment of the present invention is compost. This compost contains char, phosphorus, iron, and ammonia-oxidizing archaea. The total phosphoric acid concentration of the compost is 2.0% by weight or more and 5.0% by weight or less, the iron concentration is 0.4% by weight or more and 6.0% by weight or less, and the number of ammonia-oxidizing archaea is smaller than the total number of bacteria. The ratio is 0.04% or more and 0.10% or less.

1 is a flowchart showing a method for producing compost according to one embodiment of the present invention. 1 is a conceptual diagram illustrating carbon dioxide storage using the compost manufacturing method according to one embodiment of the present invention. Graph showing the content of ammonia contained in the compost of Examples and Comparative Examples. Graph showing the content of Nitrosospaera wienensis contained in the compost of Examples and Comparative Examples.

Hereinafter, each embodiment of the present invention will be described with reference to the drawings and the like. However, the present invention can be implemented in various forms without departing from the scope thereof, and should not be construed as being limited to the contents described in the embodiments exemplified below.

As used herein, the term "phosphorus" includes not only phosphorus alone but also compounds containing phosphorus. Therefore, phosphorus also includes phosphoric acid. Here, the term "phosphoric acid" does not only mean phosphoric acid in the narrow sense, that is, a compound represented by the chemical formula H ₃ PO ₄ , but also refers to various phosphoric acids in addition to phosphoric acid (H ₃ PO ₄ ). The term is used to indicate acid salts, monohydrogen phosphate, and dihydrogen phosphate. Therefore, for example, iron phosphate means not only iron phosphate, but also monohydrogen iron phosphate and dihydrogen iron phosphate, unless otherwise specified. Further, there is no restriction on the valence of the metal contained in the phosphate; for example, the iron ion of iron phosphate may be divalent or trivalent.

1. Compost The compost according to one embodiment of the present invention includes char, phosphorus, iron, and ammonia-oxidizing archaea. The compost may further contain water and a binder. The compost may further include sodium hypochlorite. The compost may further contain sulfur-containing compounds, manganese-containing compounds, boron-containing compounds, fibers, etc. contained in fertilizer auxiliaries. Each of these components will be explained below.

1-1. Carbide The carbide contained in this compost is a porous material containing carbon as a main component and having pores with a cross-sectional diameter of several nanometers to several tens of micrometers. The concentration (composition) of char in the present compost is, for example, 2% by weight or more and 40% by weight or less, or 5% by weight or more and 35% by weight or less. By containing carbonized materials within the above-mentioned range, a high composition of ammonia-oxidizing archaea, which will be described later, can be maintained. The specific gravity of the carbide may be 0.05 g/cm ³ or more and 0.8 g/cm ³ or less, or 0.1 g/cm ³ or more and 0.5 g/cm ³ or less. The specific surface area of the carbide is, for example, 100 m ² /g or more and 900 m ² /g or less, 100 m ² /g or more and 800 m ² /g or less, or 150 m ² /g or more and 400 m ² /g or less. The specific surface area is measured using a mercury intrusion method, a gas adsorption method such as the BJH method, or the HK method.

1-2. Phosphorus This compost contains phosphorus at a concentration of 2.0% by weight or more and 5.0% by weight or less as total phosphoric acid (that is, the total amount of phosphorus). At least a portion of the phosphorus contained in this compost is contained as divalent or trivalent iron phosphate. As will be described later, in the production of this compost, a mixture containing iron and carbide (iron-containing carbide) is treated with water containing phosphoric acid. Therefore, iron (III) phosphate is mainly derived from water containing iron and phosphoric acid in iron-containing carbides.

In this compost, another part of the phosphorus may exist as water-insoluble phosphoric acid. Water-insoluble phosphoric acid is phosphoric acid that is insoluble in water and soluble in a 2% aqueous citric acid solution (citric acid-soluble phosphoric acid). Examples of the water-insoluble phosphoric acid include calcium hydrogen phosphate, calcium dihydrogen phosphate, calcium phosphate, magnesium monohydrogen phosphate, and magnesium phosphate. These water-insoluble phosphate metal ions are derived from charred materials, which are raw materials for compost, and organic fertilizer sources.

The present compost may further contain water-soluble phosphoric acid. Water-soluble phosphoric acids include phosphates such as lithium phosphate, sodium phosphate, potassium phosphate, and ammonium phosphate, lithium monohydrogen phosphate, sodium monohydrogen phosphate, potassium monohydrogen phosphate, and monohydrogen phosphate. Examples include monohydrogen phosphates such as ammonium, lithium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate. These water-soluble phosphate metal ions also come from carbide and organic fertilizer sources.

Ammonium vanadomolybdate spectrophotometry can be used to quantify the total amount of phosphorus contained in this compost, that is, total phosphoric acid. For example, a predetermined amount of compost is decomposed using nitric acid or perchloric acid, and then ammonium vanadate (V), hexaammonium heptamolybdate, and nitric acid are added. Total phosphoric acid is quantified by measuring the absorption (for example, absorption at 420 nm) of the formed phosphovanadomolybdate using an ultraviolet/visible spectrophotometer.

The concentration of water-soluble phosphoric acid can be determined using, for example, ammonium vanadomolybdate spectrophotometry. In this method, for example, water is added to the 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-orthophosphate to orthophosphate ions. Ammonium vanadate(V), hexaammonium heptamolybdate and nitric acid are then added to form phosphovanadomolybdate. Water-soluble phosphoric acid is quantified by measuring the absorption (for example, absorption at 420 nm) of phosphorus vanadomolybdate using an ultraviolet/visible spectrophotometer.

1-3. Iron The main compost contains iron at a concentration (composition) of 0.4% by weight or more and 6.0% by weight or less. At least a portion of the iron contained in this compost exists as iron phosphate. Further, the other part may exist as metallic iron (that is, zero-valent iron), or may exist as iron oxide or iron hydroxide. These iron and iron compounds are components mainly derived from iron and iron oxide added in the manufacturing process of this compost. For example, metallic iron is caused by the fact that the added iron exists in the compost without being oxidized. Trivalent iron (III) phosphate is produced when a mixture of carbide and iron (iron-containing carbide) is treated with water containing phosphoric acid. As will be described later, in the production of this compost, iron-containing carbide is treated together with an organic fertilizer source under anaerobic conditions, and in this process iron (III) phosphate is reduced to form divalent iron ions and phosphate. Gives ions. This divalent iron ion is subsequently oxidized under aerobic conditions to produce iron(III) oxide and iron(III) hydroxide. As a result, the compost may contain iron(III) hydroxide in addition to the iron(III) oxide added during manufacture.

1-4. Ammonia-oxidizing archaea This compost contains at least one of Nitrososphaera viennensis and Nitrosopumilus maritimus as ammonia-oxidizing archaea. The ratio of the number of ammonia-oxidizing archaea to the total number of bacteria in this compost is 0.04% or more and 0.10% or less. As shown in the examples, by including ammonia-oxidizing archaea in such a relatively high proportion, ammonia is nitrified by ammonia-oxidizing archaea in the compost manufacturing process, so the generation of odor is greatly suppressed. Moreover, the generation of odor from the obtained main compost is also effectively suppressed. Therefore, even if organic waste is used as a raw material, it is possible to provide compost in which the generation of bad odor caused by ammonia is suppressed.

The number of total bacteria and ammonia-oxidizing archaea in this compost can be measured by genome analysis of the compost.

As mentioned above, the present compost contains char, which is a porous material, and further has a relatively high total phosphoric acid concentration. The porous material and the phosphoric acid provide oxygenated space and nutrients, respectively, for the ammonia-oxidizing archaea to grow. Due to this, the present compost has a high proportion of ammonia-oxidizing archaea, and as a result, ammonia generated during compost production is quickly nitrified, and odor caused by ammonia is suppressed.

1-5. Binder A binder is used to efficiently disperse carbides, iron powder, and iron oxide and to integrate them in the compost manufacturing process described below. Although there are no restrictions on the type of binder, organic binders and/or inorganic binders can be used. Examples of the organic binder include molasses, blackstrap molasses, starch, dextrin, corn starch, rice bran, polyvinyl alcohol, copolymer of vinyl acetate and ethylene or saponified product thereof, pulp waste liquid, lignin sulfonate, carboxymethylcellulose, hydroxypropyl. Examples include one or more selected from methylcellulose, sodium alginate, phenolic resin, tar pitch, and the like. Among them, molasses is inexpensive, has few harmful components, and has many solid components, so using molasses makes it easy to mold the removal material. Examples of the inorganic binder include cement, pulverized blast furnace slag, fly ash, gypsum (calcium sulfate), calcined gypsum obtained by heating and dehydrating gypsum, and sodium silicate.

1-6. Oxidizing agent In the production process of this compost, an oxidizing agent such as sodium hypochlorite or sulfuric acid may be added for sterilization. Therefore, sodium hypochlorite and sulfuric acid derived from the remaining oxidizing agent may be contained in the compost. The concentration (composition) of sodium hypochlorite and sulfuric acid in this compost may be, for example, 100 ppm or more and 1% or less.

1-7. Other Components Examples of the sulfur-containing compound 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 the boron-containing compound 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. Sulfur-containing compounds, sulfur-containing compounds, manganese-containing compounds, boron-containing compounds, and fibers are mainly derived from fertilizer aids.

As mentioned above, this compost contains a relatively high proportion of ammonia-oxidizing archaea that nitrify ammonia. Furthermore, the total phosphoric acid concentration is also high. Therefore, it can be said that this compost is a compost that greatly suppresses the generation of odor and is rich in fertilizer components that contribute to plant growth.

2. Compost Manufacturing Method Hereinafter, the present compost manufacturing method according to one embodiment of the present invention will be described. The flow of this manufacturing method is shown in FIG.

2-1. Preparation of carbide First, prepare carbide. Specifically, organic materials such as biomass are heated at low oxygen concentrations. Here, biomass is a type of organic matter, which is a substance derived from a living body and its metabolites. Biomass that can be used in the preparation of char includes materials derived from wood. Specifically, wooden molded products such as plate-shaped or columnar wood, thinned wood, pruning waste wood, construction waste wood, powdered sawdust, and particle boats can be mentioned. There are no restrictions on the type of wood; cedar, cypress, or bamboo may be used. 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. Biomass also includes plants that are raw materials for fibers such as hemp, flax, cotton, sisal, abaca, and coconut wool. Alternatively, the biomass may be algae such as seaweed, food residue, or silage obtained from animal waste.

Specifically, carbide can be obtained by heating an organic substance 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. When carbonization is performed in a reduced pressure atmosphere, a low vacuum state of 10 ² Pa or more and 10 ⁵ Pa or less, a medium vacuum state of 10 ^-1 Pa or more and 10 ² Pa or less, or a high vacuum state of 10 ^-5 Pa or more and 10 ^-1 Pa or less. , or in an ultra-high vacuum state of 10 ⁻⁵ Pa or less. When carbonization is performed in a low oxygen atmosphere, the oxygen concentration can be 0.01% or more and 3% or less, or 0.1% or more and 2% or less. The heating temperature in carbonization may be 400°C or more and 1200°C or less, 500°C or more and 1100°C or less, 600°C or more and 1000°C or less, or 600°C or more and 900°C or less. The heating time may be 10 minutes or more and 10 days or less, or 10 minutes or more and 5 hours or less.

Carbonization is performed using an internal combustion type or external heat type carbonization furnace. Examples of the carbonization furnace include a batch-type closed charcoal kiln, a continuous rotary kiln, a rocking carbonization furnace, and a screw furnace. Carbonization of organic matter generates carbonized gas, and pores with various shapes and sizes are formed, which is a complex mixture of pores caused by the structure of the organic matter and pores formed by the desorption of carbonized gas. A carbonized carbide is formed. Note that carbonization gas mainly includes gases that are flammable or have reducing power, such as hydrogen, carbon monoxide, and alkanes represented by methane, propane, butane, and the like. Since the carbonized gas is extracted at a high temperature (700° C. to 1300° C.), its thermal energy and flammability may be used as an energy source for power generation, hot water supply, etc.

2-2. Preparation of iron-containing carbide Next, carbide and iron powder are mixed to obtain iron-containing carbide. As the iron powder, iron powder that is partially oxidized and contains iron oxide or iron hydroxide on the surface may be used. Furthermore, iron oxide powder may be added at the same time as iron powder. At this time, a binder and water may be further added. By adding a binder and water, it is possible to prevent the generation of dust caused by carbides, iron powder, and iron oxide powder, and to achieve uniform mixing.

There are no restrictions on the shape of the iron powder or iron oxide powder used at this time; for example, iron powder or iron oxide powder having an average circularity of 50 or more and 100 or less, 70 or more and 95 or less, or 80 or more and 90 or less may be used. Here, the average circularity is one of the parameters that expresses the shape of each particle contained in the powder, and the image obtained by observing the powder with a microscope is analyzed to determine the circularity of multiple particles. This is the average value. As the circularity, for example, a value obtained by dividing the circumference of a circle having an area equal to the area of the projection surface by the circumference of the projection surface of each particle in the microscope image can be used. Alternatively, a value obtained by dividing the area of the projection surface by the area of a circle inscribing the projection surface may be adopted as the degree of circularity. There are no restrictions on the average particle size of the iron powder or iron oxide powder, and is, for example, 20 μm or more and 500 μm or less, or 50 μm or more and 200 μm or less. Here, the average particle size of the powder is a value obtained by analyzing an image obtained by observing the powder under a microscope, determining the particle size of a plurality of particles, and averaging the results. As the particle size of each particle, for example, the diameter of a circle inscribing the projection surface of each particle in a microscope image or the length of one side of a square can be adopted.

The amount of carbide during mixing is 20% by weight or more and 80% by weight or less, 40% by weight or more and 80% by weight or less, or 60% by weight or more and 80% by weight based on the total weight of the carbide, binder, iron powder, and iron oxide powder. It may be selected from a range of % by weight or less. The total amount of iron powder and iron oxide powder is 5% by weight or more and 35% by weight or less, 5% by weight or more and 25% by weight or less, or 5% by weight or more and 20% by weight or less based on the total weight of carbide, binder, and iron powder. You can choose from the range. When both iron powder and iron oxide powder are used, their weight ratio (iron powder: iron oxide powder) may be selected, for example, from a range of 1:5 or more to 5:1. The amount of the binder is 5% to 50% by weight, 15% to 50% by weight, or 20% to 50% by weight based on the total weight of the carbide, binder, iron powder, and iron oxide powder. Just select from the range.

The obtained iron-containing carbide may be appropriately granulated and molded into a certain shape. Molding can be performed using a granulator. Examples of the granulator 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 formed into a pellet shape (for example, approximately cylindrical shape) using an extrusion type granulator.

After this, the iron-containing carbide may be further dried. Drying is performed, for example, at a temperature selected from the range of 30°C or higher and lower than 400°C, 50°C or higher and 300°C or lower, and 100°C or higher and 300°C or lower. The humidity during drying may be 20% or more and 95% or less, or 50% or more and 90% or less. The drying time is also appropriately selected from the range of 1 minute to 1 week, 1 hour to 3 days, or 3 hours to 1 day. The atmosphere during drying may be, for example, air, nitrogen, a rare gas such as argon, or a mixture thereof.

2-3. Preparation of iron phosphate-containing carbide The iron phosphate-containing carbide is prepared by bringing the iron-containing carbide obtained in the steps up to this point into contact with water containing phosphoric acid (hereinafter referred to as treated water). The treated water may be prepared by dissolving a phosphate such as sodium phosphate or potassium phosphate in water, or water from a body of water such as a river, lake, or sea may be used as the treated water. For example, a container filled with iron-supported carbide may be placed in a river, lake, or ocean, and the iron-containing carbide may be brought into contact with water in the body of water. As a result, phosphoric acid contained in rivers, lakes, and sea water reacts with iron, iron oxide, and/or iron hydroxide contained in iron-containing carbides, and iron phosphate (III), which has low solubility in water, reacts with iron, iron oxide, and/or iron hydroxide contained in iron-containing carbides. ) is adsorbed or supported on carbides, and phosphoric acid and phosphorus-containing organic compounds in water bodies are removed. That is, by this method, not only can iron phosphate-containing carbide be prepared at low cost, but also water purification and water quality improvement of various water bodies can be performed at the same time.

2-4. Composting Next, compost the iron phosphate-containing carbide as one of the raw materials.

(1) Mixing of iron phosphate-containing carbide and organic fertilizer source First, the iron phosphate-containing carbide obtained by the method described above and the organic fertilizer source are mixed. There is no restriction on the amount of iron phosphate-containing carbide relative to the organic fertilizer source, but for example, if 1% to 40% by weight or 5% to 25% by weight of iron phosphate-containing carbide is added to the organic fertilizer source. good. If the resulting mixture (primary mixture) has a high viscosity, water may be further added to adjust the viscosity. Organic fertilizer sources include easily degradable organic matter of biological origin, such as animal feces and urine such as cow manure, pig manure, and chicken manure, food waste such as food residue, agricultural waste, food waste, and sludge. Can be mentioned. To determine whether or not it is an easily decomposable organic substance, for example, the amount of carbon dioxide generated after mixing with soil or the content of acid detergent soluble organic substance (AD soluble organic substance) can be used as one of the indicators.

The amount of carbon dioxide generated from an organic fertilizer source can be determined by adding water to a mixture of a predetermined amount of sample and soil, starting culture, and quantifying the amount of carbon dioxide generated during the culture. The generated carbon dioxide can be collected with an aqueous sodium hydroxide solution, barium chloride is added to this to precipitate it as barium carbonate, and carbon dioxide can be quantified by titrating the barium carbonate with hydrochloric acid. For example, if the amount of carbon dioxide generated up to 10 days after the start of culture is 200 mg or more, 300 mg or more, or 400 mg or more per 1 g of dry sample, this sample is easily degradable organic matter, and it is necessary to produce this compost. It can be judged that it can be used as a source of organic fertilizer.

For the determination of AD-soluble organic substances, for example, a sample is boiled for 1 hour in an acidic detergent solution (for example, a solution of 20 g of cetyltrimethylammonium bromide dissolved in 1 L of 0.5 mol/L sulfuric acid), and then filtered. Wash, dry and weigh the residue. Thereafter, the residue is incinerated and weighed, and the difference in weight from before incineration is determined as the amount of acidic detergent fiber (ADF). Since AD soluble organic matter is an organic matter other than ADF, AD soluble organic matter is calculated by subtracting the weight of ADF and the residue after ashing from the sample weight. 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 1 g of the dry sample, this sample is easily decomposable organic matter, and it is considered that the sample is an easily decomposable organic matter, and it is suitable as an organic fertilizer for producing this compost. It can be determined that it can be used as a source.

However, in the embodiment of the present invention, the organic fertilizer source is not limited by the above-mentioned index or its numerical value, and any organic substance that can be decomposed by anaerobic microorganisms can be used as the organic fertilizer source.

The mixing of the iron phosphate-containing carbide and the organic fertilizer source may be performed in a closed chamber or in an open space. The primary mixture is obtained as a plurality of lumps (blocks) with an average diameter from a few cm to several tens of cm, or a volume on the order of a few ^cm3 to several thousand ^cm3 .

(2) Fermentation The primary mixture is subsequently subjected to fermentation treatment. Specifically, first, the primary mixture is exposed to an atmosphere containing oxygen. The atmosphere containing oxygen may be an atmospheric atmosphere or an atmosphere containing oxygen and an inert gas such as nitrogen or argon. The fermentation process may be carried out at the temperature of the outside air, or may be carried out in an environment where the temperature is controlled within the range of 30°C or higher and 60°C or lower. The fermentation treatment time can also be arbitrarily set, and may be appropriately selected from the range of, for example, 1 day to 120 days, 10 days to 60 days, or 15 days to 30 days. Through this treatment, the surface of each mass of the primary mixture is exposed to aerobic conditions, and the interior thereof is exposed to anaerobic conditions. As a result, aerobic fermentation progresses on the surface of each lump, and at the same time anaerobic fermentation progresses inside. In each mass of the primary mixture, the portion where aerobic fermentation proceeds is limited to approximately the surface, so anaerobic fermentation proceeds in most of the primary mixture.

Anaerobic fermentation is facilitated by the action of anaerobic microorganisms contained in organic fertilizer sources. For this reason, in mixing the above-mentioned iron phosphate-containing carbide and organic fertilizer source, anaerobic microorganisms that promote the decomposition of organic matter may be added. Examples of anaerobic microorganisms include nitrate-reducing bacteria, iron-reducing bacteria, sulfate-reducing bacteria, acid-producing bacteria, acetogenic bacteria, and methanogenic archaea, with iron-reducing bacteria and methanogenic archaea being preferred.

In this fermentation process, as organic matter is decomposed by anaerobic fermentation, the inside of each lump of the primary mixture becomes a reducing environment, and the oxidation-reduction potential (ORP) becomes negative and large. Therefore, trivalent iron phosphate is reduced to divalent iron phosphate within the primary mixture. Since divalent iron phosphate has a higher solubility in water than trivalent iron phosphate, at least a portion of iron phosphate dissolves in the water contained in the primary mixture, and divalent iron ions and phosphate Dissociates into acid ions. For example, when the trivalent iron phosphate contained in the iron compound-containing carbide is FePO ₄ , divalent iron phosphate Fe ₃ (PO ₄ ) ₂ is generated. In addition, since the iron phosphate-containing carbide contains carbide derived from organic matter such as biomass, it contains many alkali metal and alkaline earth metal ions. Similarly, organic fertilizer sources also contain large amounts of alkali metals and alkaline earth ions. These ions ionically bond with phosphate ions to give water-soluble phosphoric acid or water-insoluble phosphoric acid. Proteins contained in organic fertilizer sources also decompose into ammonia, resulting in the production of ammonium phosphate from ammonia, phosphate ions, and water.

(3) Treatment under aerobic conditions After the fermentation treatment, the inside of each mass of the primary mixture is treated under aerobic conditions. Specifically, each lump of the primary mixture is crushed and the inside thereof is brought into contact with oxygen. The pulverization may be performed in the atmosphere or in an atmosphere containing oxygen and an inert gas such as nitrogen or argon. Through this step, divalent iron phosphate is rapidly oxidized by oxygen to give iron (III) oxide and iron (III) hydroxide. At this time, due to the low solubility of iron (III) oxide in water, the reaction between iron (III) oxide and phosphoric acid can be almost ignored, and the phosphate ions produced in the fermentation process are alkali metal ions, It ionically bonds with alkaline earth ions or ammonium ions to give water-soluble phosphoric acid and water-insoluble phosphoric acid. In the compost of the present invention, the porous material and the phosphoric acid provide a space capable of supplying oxygen and nutrients for the growth of ammonia-oxidizing archaea, respectively. Therefore, aerobic conditions can be maintained for a long time, so ammonia-oxidizing archaea proliferate, ammonia generated during compost production is nitrified, and odor caused by ammonia is suppressed.

2-5. Sterilization Treatment Although the compost according to one of the embodiments of the present invention can be produced through the above steps, a sterilization treatment may be performed subsequently. The sterilization treatment is preferably performed by treating the compost with an oxidizing agent. The oxidative agent treatment may be carried out by, for example, spraying water containing sodium hypochlorite or sulfuric acid. Alternatively, the compost may be irradiated with ultraviolet light. Furthermore, the water content may be appropriately controlled by evaporating water contained in the organic fertilizer source or water added separately, thereby making it possible to obtain compost that is easy to handle.

As described above, trivalent iron phosphate is reduced by the anaerobic fermentation that progresses inside the primary mixture to produce divalent iron phosphate. Divalent iron phosphate dissolves in water and phosphate ions are liberated. On the other hand, ammonia is produced by the decomposition of organic fertilizer sources.

Under subsequent aerobic conditions, divalent iron ions are oxidized and precipitated as iron oxide (III) with low solubility, so that trapping of phosphate ions by iron ions is suppressed. On the other hand, the primary mixture contains alkali metal ions and alkaline earth metal ions derived from organic matter and organic fertilizer sources that are raw materials for carbide. For this reason, phosphate ions liberated by anaerobic fermentation and phosphoric acid generated in the equilibrium between phosphate ions and water combine with ammonia, alkali metal ions, and alkaline earth metal ions, and become water-soluble along with water-insoluble phosphoric acid. Produces phosphoric acid. As a result, the resulting compost functions as an excellent source of water-soluble phosphoric acid and can contribute to plant growth as a fast-acting fertilizer.

Here, with anaerobic fermentation, the organic fertilizer source produces ammonia. However, the charred material that is the raw material for this compost is a porous material with a large number of pores, and can provide space for ammonia-oxidizing archaea to proliferate. Furthermore, in the production process of this compost, phosphoric acid reacts with iron, iron oxide, and/or iron hydroxide contained in the iron-containing carbide, and is adsorbed or supported on the carbide as iron (III) phosphate with low solubility. The subsequent anaerobic fermentation provides soluble or insoluble phosphoric acid. Therefore, ammonia-oxidizing archaea can proliferate using phosphoric acid as nutrients. As a result, this compost contains a high proportion of ammonia-oxidizing archaea, so that the ammonia-oxidizing archaea functions effectively and efficiently nitrifies the generated ammonia. Due to the contribution of such a mechanism, it is possible to effectively suppress the generation of odor during compost production, and it is also possible to reduce the generation of odor from the compost.

2-6. Other Steps The obtained compost may be used alone as a fertilizer, or after being mixed with a fertilizer auxiliary containing the above-mentioned sulfur-containing compound, manganese-containing compound, or boron-containing compound. In this case, the fertilizer aid may be added so that the concentration of the sulfur-containing compound, manganese-containing compound, or boron-containing compound in the compost is, for example, 0.01% by weight or more and 1% by weight or less. Mixing may be carried out using a mixer, and the mixer can be arbitrarily selected from a free fall mixer, a forced mixer, a Y-branch mixer, an agitator mixer, a paddle mixer, and the like.

Furthermore, the obtained compost may be dried, molded, etc. In shaping, compost may be processed into any shape such as pellets, rods, granules, or powder. If necessary, crushing or 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 or more and 10 mm or less. Crushing may be carried out using a crusher, such as a vibration mill, jet mill, ball mill, roller mill, rod mill, hammer mill, impact mill, rotary mill, pin mill, pin-disc mill, or planetary mill. can be used. By crushing the compost using a crusher, the surface area increases, and as a result, the elution of water-soluble phosphoric acid into the soil is promoted. Classification is performed using a classifier, and either a dry classifier or a wet classifier may be adopted as the classifier. Examples of classifiers include airflow classifiers, gravity field classifiers, inertial force field classifiers, and centrifugal force field classifiers.

The compost according to one embodiment of the present invention produced by the method described above not only contains abundant phosphoric acid, but also has significantly suppressed odor caused by ammonia. Therefore, it can contribute to the growth of plants as a compost that is easy to handle.

Here, carbonized material, which is the main component of compost, can be obtained by carbonizing biomass. That is, charcoal is prepared by effectively utilizing biomass derived from plants produced by fixing carbon dioxide through photosynthesis. Furthermore, in the process of producing compost using this char, it is possible to improve the water quality of various water systems, and by distributing this compost to the soil, carbon dioxide fixed by plants can be stored underground as char. can.

More specifically, as shown in FIG. 2, according to an embodiment of the present invention, biomass is carbonized to prepare a carbide (1), and an iron-containing carbide is further prepared from the carbide (2). This iron-containing carbide contributes to water purification when converted to iron-phosphate-containing carbide (3) and undergoes a series of processes including mixing with an organic fertilizer source, fermentation treatment, and treatment under aerobic conditions. It is converted into compost containing porous carbonized material originating from biomass (4). This compost is applied to the soil as a fertilizer containing water-soluble phosphoric acid and water-insoluble phosphoric acid, and is used for growing plants (5). Plants fix atmospheric carbon dioxide through photosynthesis, provide food and structural materials, and produce biomass as a by-product, which is the raw material for charcoal (6).

Through the cycle established by this series of processes (1) to (6), carbon dioxide in the atmosphere is fixed as organic matter through photosynthesis, and this organic matter is used as food and materials, and biomass is produced as a by-product. . Biomass is converted into charred material through carbonization, which is eventually spread underground as compost. Therefore, it can be said that the compost and the method for producing the same according to one embodiment of the present invention contribute to the reduction of atmospheric carbon dioxide by storing atmospheric carbon dioxide underground as carbon.

In this example, production of compost and evaluation thereof according to one embodiment of the present invention will be described.

1. Preparation of iron phosphate-containing carbide Add irregularly shaped charcoal (woody biomass gasification power generation waste charcoal), iron powder, iron oxide powder, blast furnace slag powder as a binder, and water, and knead at room temperature for 30 minutes to form a powder. A mixture was obtained. Next, the obtained powder mixture was put into a granulator and formed into pellets having a diameter of 4 mm and a height of 10 mm. Thereafter, the molded powder mixture was dried (cured) at 20° C. for 24 hours to obtain an iron-containing carbide.

The iron content in the iron-containing carbide is determined by extracting iron by treating the crushed iron-containing carbide according to JIS K 1474, and measuring the extracted iron content using an inductively coupled plasma emission spectrometer (manufactured by PerkinElmer, Inc., Optima 5300 DV). As a result, it was confirmed that 10% by weight of iron was contained based on the total amount of iron-containing carbides.

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

2. Fermentation Cow dung was used as an organic fertilizer source. In the examples, a primary mixture of an organic fertilizer source and an iron phosphate-containing carbide (weight ratio: organic fertilizer source: iron phosphate-containing carbide = 1:0.05 to 1:1) was prepared, and this primary mixture was mixed with a resin. The mixture was filled into bottles (capacity: approximately 500 L), sealed, and fermented at 60° C. for 5 days. During the fermentation process, the primary mixture was stirred once a day.

On the other hand, in a comparative example, an organic fertilizer source was fermented under the same conditions as in the example without using the iron phosphate-containing carbide.

After fermentation, test method for fertilizers (Agriculture, Forestry and Fisheries Consumer Safety Technology Center) 4.1.2. Ammonia contained in the sample was evaporated according to the a-distillation method. The volatilized ammonia was trapped with a trapping agent (0.25M aqueous sulfuric acid solution), and the ammonia concentration was measured by back titrating the trapping agent with a 0.1M aqueous sodium hydroxide solution. The results are shown in FIG. As shown in Figure 3, the amount of ammonia generated in the example was less than half that of the comparative example, indicating that the amount of ammonia generated can be significantly reduced by using carbide on which iron phosphate is adsorbed or supported. I understand.

The samples of Examples and Comparative Examples after fermentation were subjected to genome analysis, and the amount of Nitrosospaella wienensis contained in the samples was measured. The results are shown in FIG. As can be seen from FIG. 4, it was confirmed that the amount of Nitrosospaera wienensis contained in the sample of the example was about 8 times that of the comparative example. From this, it can be said that by using a charcoal material in which iron phosphate is adsorbed or supported, the growth of ammonia-oxidizing archaea is promoted, and as a result, the amount of ammonia generated during composting is reduced.

The embodiments described above as embodiments of the present invention can be implemented in appropriate combinations as long as they do not contradict each other. Additions, deletions, or design changes to components based on each embodiment by those skilled in the art are also included in the scope of the present invention, as long as they have the gist of the present invention.

Even if there are other effects that are different from those brought about by each of the embodiments described above, those that are obvious from the description of this specification or that can be easily predicted by a person skilled in the art are naturally included in the present invention. It is understood that this is brought about by

Claims (6)

Contains carbide, phosphorus, iron, and ammonia-oxidizing archaea;
The total phosphoric acid concentration is 2.0% by weight or more and 5.0% by weight or less,
The concentration of iron is 0.4% by weight or more and 6.0% by weight or less,
A compost in which the number of ammonia-oxidizing archaea with respect to the total number of bacteria is 0.04% or more and 0.10% or less. The compost according to claim 1, containing the charred material at a concentration of 2% by weight or more and 40% by weight or less. The compost according to claim 1, wherein the specific surface area of the carbide is 100 m ² /g or more and 900 m ² /g or less. Compost according to claim 1, wherein at least a portion of the phosphorus and the iron are present as iron phosphate. The compost according to claim 1, wherein the ammonia-oxidizing archaea comprises at least one of Nitrosospaera wienensis and Nitrosopumilus maritimus. The compost of claim 1, further comprising a binder.

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