JP2021065816A - Manufacturing method of biogas using used sanitary articles - Google Patents

Abstract

To provide an effective manufacturing method of a biogas from used sanitary article-derived solid wastes.SOLUTION: This method produces a biogas by using used sanitary article-derived solid wastes involving a high water-absorbing polymer, a pulp fiber, a synthetic resin material and excrement. This method includes a breaking step S1 of breaking used sanitary articles in an inactivation aqueous solution capable of inactivation of a high water-absorbing polymer; a forming step S2 of forming a process liquid involving a decomposition product of excrement and the high water-absorbing polymer by separating the high water-absorbing polymer, the pulp fiber and the synthetic resin material from the inactivation aqueous solution involving the broken used sanitary articles; and a biogas manufacturing step S3 for manufacturing a biogas using the process liquid.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing biogas using used hygiene products.

A method for producing biogas by biologically treating an organic substance (eg, fermentation, anaerobic treatment) is known. As a method for producing such a biogas, for example, Patent Document 1 discloses an anaerobic treatment method and an apparatus for cell material-containing waste. This method is a method for producing biogas by anaerobicizing pulp-containing waste. This method decomposes the organic components of the suspension in the steps of mechanically treating the waste, especially crushing, suspending / dissolving the crushed waste in treated water, and the biological treatment step. Purification and / or methanation, separation of corrosion residues into plastic-rich and pulp-rich parts, and plastic-rich and pulp-rich parts from renewable materials, fuels or deposits. Includes the process of adjusting to the product. Examples of pulp-containing waste include used sanitary products containing urine and excrement (eg, diapers and incontinence products).

Special Table 2009-502455 Gazette

In the method of Patent Document 1, used sanitary goods are used as a raw material for biogas production. In this method, sanitary plastics and pulp are separated from the corrosion residue after the biogas is produced in the biological treatment stage. Therefore, the treated water containing waste, which is the target of biological treatment at the biological treatment stage, that is, the raw material for biogas production, contains a mixture of plastics and pulps that are difficult to be treated by biological treatment. There is. Therefore, in the biological treatment, the efficiency of the treatment is increased due to the fact that the plastic or pulp inhibits the treatment, or that the organic component of the waste adheres to the plastic or pulp and the amount of the organic component to be treated is reduced. May fall off. Therefore, when biogas is produced from waste derived from used sanitary products, there is room for improvement from the viewpoint of efficient production.

An object of the present invention is to provide a method for producing biogas, which can be efficiently produced when producing biogas from waste derived from used sanitary goods.

The present invention is a method for producing biogas using waste derived from used sanitary products including highly water-absorbent polymer, pulp fiber, synthetic resin material and excrement, and the highly water-absorbent polymer can be inactivated. The highly water-absorbent polymer, the pulp fiber, and the synthetic resin material are separated from the inactivated aqueous solution containing the crushed used sanitary goods and the crushing step of crushing the used sanitary goods in the inactivated aqueous solution. A method comprising a production step of producing a treatment liquid containing the excrement and a decomposition product of the highly water-absorbent polymer, and a biogas production step of producing biogas using the treatment liquid. is there.

In this method, the highly water-absorbent polymer, pulp fiber and synthetic resin material, which are difficult to be subjected to biological treatment, are separated in advance from the treatment liquid used as a raw material in the biogas production process. Therefore, the amounts of the highly water-absorbent polymer, pulp fiber, and synthetic resin material contained in the treatment liquid are smaller than those in the case where they are not separated in advance. In addition, the treatment solution is rich in organic components such as excrement to be biologically treated and decomposition products of highly absorbent polymers. Therefore, when the treatment liquid is subjected to biological treatment, the synthetic resin material or pulp fiber inhibits the biological treatment, or the organic component adheres to the synthetic resin material or pulp fiber, and the organic component to be treated is organic. It is possible to suppress the decrease of the components. Thereby, the decrease in the efficiency of biological processing can be suppressed. Further, although biological treatment is difficult for the highly water-absorbent polymer itself, biological treatment is possible for the decomposition product of the highly water-absorbent polymer. Therefore, in this method, the amount of biogas generated can be increased by using the decomposition product of the highly water-absorbent polymer as a raw material in the biogas production process. As a result, when biogas is produced from waste derived from used sanitary products, it can be produced more efficiently.

According to the present invention, when biogas is produced from waste derived from used sanitary goods, it is possible to provide a method for producing biogas that can be efficiently produced.

It is a block diagram which shows the example of the manufacturing method of biogas which concerns on embodiment. It is a flowchart which shows the example of the generation process which concerns on embodiment. It is a flowchart which shows the other example of the generation process which concerns on embodiment. It is a block diagram which shows the example of the recycling system which concerns on embodiment. It is a flowchart which shows the example of the recycling method which concerns on embodiment. It is a flowchart which shows an example of the recycling method of the used hygiene article which concerns on embodiment.

Hereinafter, a method for producing biogas using waste derived from used sanitary products including highly water-absorbent polymer, pulp fiber, synthetic resin material and excrement according to the embodiment will be described. However, hygienic products include, for example, absorbent articles, and absorbent articles include, for example, disposable diapers, urine absorbing pads, sanitary napkins, and bed sheets. Examples of excrement include urine, feces, and menstrual blood. A used hygiene product is a hygiene product that is used by the user and absorbs and retains the user's excrement. However, some of them may be used but do not absorb and retain excrement, or unused but discarded.

First, a configuration example of an absorbent article, which is an example of hygiene products, will be described. The absorbent article includes a front surface sheet, a back surface sheet, and an absorbent body arranged between the front surface sheet and the back surface sheet. An example of the size of the absorbent article is a length of about 15 to 100 cm and a width of 5 to 100 cm. The absorbent article may further include other members included in the general absorbent article, such as a diffusion sheet, a leak-proof wall, and a side sheet.

Examples of the constituent members of the surface sheet include a liquid-permeable non-woven fabric, a synthetic resin film having liquid-permeable holes, and a composite sheet thereof. Examples of the constituent members of the back sheet include a liquid-impermeable non-woven fabric, a liquid-impermeable synthetic resin film, and a composite sheet thereof. Examples of the constituent members of the diffusion sheet include a liquid-permeable non-woven fabric. Examples of the constituent members of the leak-proof wall and the side sheet include a liquid-impermeable non-woven fabric, and the leak-proof wall may include an elastic member such as rubber. Here, the material of the non-woven fabric or the synthetic resin film is not particularly limited as long as it can be used as an absorbent article, but for example, an olefin resin such as polyethylene or polypropylene, or a polyamide such as 6-nylon or 6,6-nylon. Examples thereof include polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Therefore, the front surface sheet, the back surface sheet, the diffusion sheet, the leakage-proof wall, the side sheet, and the like are mainly composed of a film or a non-woven fabric made of a synthetic resin member.

Examples of the constituent members of the absorber include an absorber material, that is, pulp fiber and a highly water-absorbent polymer. The pulp fiber is not particularly limited as long as it can be used as an absorbent article, and examples thereof include cellulosic fibers. Examples of cellulosic fibers include wood pulp, crosslinked pulp, non-wood pulp, regenerated cellulose, semi-synthetic cellulose and the like. As the size of the pulp fiber, the average value of the major axis of the fiber is, for example, several tens of μm, preferably 20 to 40 μm, and the average value of the fiber length is, for example, several mm, preferably 2 to 5 mm. The super absorbent polymer (SAP) is not particularly limited as long as it can be used as an absorbent article. Examples of the highly water-absorbent polymer include polyacrylate-based, polysulfonate-based, and maleic anhydride-based water-absorbent polymers, and three-dimensionally crosslinked sodium polyacrylate is preferable. The weight average molecular weight of the highly water-absorbent polymer is, for example, about several million. As the size of the highly water-absorbent polymer (when dried), the average value of the particle size is, for example, several hundred μm, preferably 200 to 500 μm. The absorber may include a core wrap formed of a liquid permeable sheet.

One surface and the other surface of the absorber are bonded to the front surface sheet and the back surface sheet, respectively, via an adhesive. In a plan view, the portion of the front surface sheet that extends outside the absorber so as to surround the absorber (peripheral portion) is outside the absorber so as to surround the absorber in the back sheet. It is joined to the extended portion (peripheral portion) via an adhesive. Therefore, the absorber is wrapped inside the joint between the front surface sheet and the back surface sheet. The adhesive can be used as an absorbent article and is not particularly limited, and examples thereof include a hot melt type adhesive.

Next, a method for producing biogas using waste derived from used sanitary products will be described. FIG. 1 is a block diagram showing an example of a biogas production method according to an embodiment, FIG. 2 is a flowchart showing an example of the production process of FIG. 1, and FIG. 3 is a flowchart showing another example of the production process of FIG. It is a flowchart which shows. However, the method for producing biogas in the present embodiment is to recycle the highly water-absorbent polymer, pulp fiber and synthetic resin material of the used sanitary goods from the used sanitary goods including excrement, and the highly water-absorbent polymer and pulp. Waste (solution containing excrement, etc.) generated at the same time when the fiber and synthetic resin materials are recovered is used for the production of biogas. Specifically, it is as shown below.

The method for producing the biogas of the present embodiment comprises a crushing step S1 for crushing the used sanitary goods in an inactivating aqueous solution capable of inactivating the highly water-absorbent polymer, and the crushed used sanitary goods. A production step S2 for separating the highly water-absorbent polymer, the pulp fiber, and the synthetic resin material from the inactivated aqueous solution containing the mixture to generate a treatment liquid containing the excrement and the decomposition product of the highly water-absorbent polymer. It includes a biogas production step S3 for producing biogas using the treatment liquid.

The inactivated aqueous solution inactivates the highly water-absorbent polymer in used hygiene products and reduces the water absorption capacity of the highly water-absorbent polymer. As a result, the highly water-absorbent polymer is dehydrated and the particle size is reduced, which facilitates handling in subsequent steps and improves treatment efficiency. Examples of the inactivated aqueous solution include an acidic aqueous solution, that is, an aqueous solution of an inorganic acid and an organic acid. In an acidic aqueous solution, the degree of inactivation (the particle size and specific gravity of a highly water-absorbent polymer) can be easily adjusted by pH. The pH of the acidic aqueous solution is preferably 1.0 or more and 4.0 or less, and more preferably 1.2 or more and 2.5 or less. If the pH is too high, the water absorption capacity of the highly water-absorbent polymer cannot be sufficiently reduced. In addition, the bactericidal ability may be reduced. If the pH is too low, there is a risk of equipment corrosion, and a large amount of alkaline chemicals are required for neutralization treatment during wastewater treatment. Examples of the organic acid include citric acid, tartaric acid, glycolic acid, malic acid, succinic acid, acetic acid, ascorbic acid, etc., but hydroxycarbonate-based organic acids such as citric acid, tartaric acid, gluconic acid, etc. are particularly preferable. , Citric acid is more preferred. The chelating effect of citric acid traps and removes metal ions and the like in excrement, and the cleaning effect of citric acid is expected to have a high effect of removing dirt components. On the other hand, examples of the inorganic acid include sulfuric acid, hydrochloric acid and nitric acid, but sulfuric acid is preferable from the viewpoint of not containing chlorine and cost. Since the pH changes depending on the water temperature, the pH in the present specification refers to the pH measured at an aqueous solution temperature of 20 ° C. The organic acid concentration of the organic acid aqueous solution is not particularly limited, but when the organic acid is citric acid, it is preferably 0.5% by mass or more and 4% by mass or less. The concentration of the inorganic acid in the aqueous solution of the inorganic acid is not particularly limited, but when the inorganic acid is sulfuric acid, it is preferably 0.1% by mass or more and 0.5% by mass or less.

The case where the used hygiene product is crushed in the inactivated aqueous solution includes not only the case where the used hygiene product is completely immersed in the inactivated aqueous solution during crushing, but also the following cases. That is, in that case, a part of the used hygiene product is immersed in the inactivated aqueous solution, the used hygiene product being crushed is sprayed with the inactivated aqueous solution, or the used hygiene product is used. Is immersed in an inactivated aqueous solution while being crushed, or is immersed in an inactivated aqueous solution immediately after the used hygiene product is crushed.

The method (S1) for crushing used sanitary products is not particularly limited as long as the members constituting the sanitary products can be crushed into a state and size that can be easily separated from each other. A method using a type crusher, a biaxial differential crusher, a biaxial shear crusher) can be mentioned. Examples of the size of the crushed material include an average value of 50 mm or more and 100 mm or less. If the size is too small, all the members will be too fine and will be mixed finely with each other, making it difficult to separate them. If the size is too large, the joints between the members will not be easily peeled off, and the solution (treatment liquid) will permeate into the members. It's hard to know because it's hard.

The method (S2) for separating the highly water-absorbent polymer, pulp fiber and synthetic resin material from the inactivated aqueous solution containing crushed used hygiene products is not particularly limited, depending on the type and size of the member to be separated. A known method can be appropriately selected. Examples of the separation method include a method using a screen separator or a centrifuge. Further, the type and order of separation of the members to be separated are not particularly limited, and a plurality of types of members may be separated at the same time in one separation step, or only one type of member may be separated.

The decomposition product of the highly water-absorbent polymer (eg, the weight average molecular weight is about several million) is not particularly limited as long as it is an organic substance produced by decomposition of the highly water-absorbent polymer. Examples of the decomposed product of the highly water-absorbent polymer include organic substances having a weight average molecular weight of about several hundreds to one thousand, preferably 5,000 or less, and more preferably 3,000 or less. The method for decomposing the highly water-absorbent polymer is not particularly limited, and examples thereof include physical and / or chemical methods, such as decomposition by heat, light and electricity, and decomposition by oxidation, reduction and water addition. Be done.

The treatment liquid contains excrement and a decomposition product of a highly water-absorbent polymer, and is not particularly limited as long as it does not adversely affect the microorganisms used in biogas production. The treatment liquid may contain, for example, the above-mentioned inactivated aqueous solution, or may be an aqueous solution containing ozone. When the treatment liquid is an acidic aqueous solution, the acidity (or pH) may be such that it does not adversely affect the microorganisms used in the biogas production of the treatment liquid.

The method for producing biogas (S3) is not particularly limited as long as biogas can be produced from excrement or a decomposition product of a highly water-absorbent polymer as a raw material. Examples of such a method include an anaerobic treatment method described in Patent Document 1, particularly a biological treatment step of methanizing an organic component of a treatment liquid containing waste using a bioreactor.

In this method, the highly water-absorbent polymer, pulp fiber and synthetic resin material, which are difficult to be subjected to biological treatment, are separated in advance from the treatment liquid used as a raw material in the biogas production process. Therefore, the amounts of the highly water-absorbent polymer, pulp fiber, and synthetic resin material contained in the treatment liquid are smaller than those in the case where they are not separated in advance. In addition, the treatment solution is rich in organic components such as excrement to be biologically treated and decomposition products of highly absorbent polymers. Therefore, when the treatment liquid is subjected to biological treatment, the synthetic resin material or pulp fiber inhibits the biological treatment, or the organic component adheres to the synthetic resin material or pulp fiber, and the organic component to be treated is organic. It is possible to suppress the decrease of the components. Thereby, the decrease in the efficiency of biological processing can be suppressed. Further, although biological treatment is difficult for the highly water-absorbent polymer itself, biological treatment is possible for the decomposition product of the highly water-absorbent polymer. Therefore, in this method, the amount of biogas generated can be increased by using the decomposition product of the highly water-absorbent polymer as a raw material in the biogas production process. Therefore, when biogas is produced from waste derived from used sanitary goods, it can be produced more efficiently.

As a preferred embodiment in the present embodiment, in the production step S2, the inactivated aqueous solution containing the highly water-absorbent polymer, the synthetic resin material, and the excrement from the inactivated aqueous solution containing the crushed used sanitary goods. S201 for taking out the pulp fiber containing the highly water-absorbent polymer, and ozone treatment of the pulp fiber containing the highly water-absorbent polymer in an aqueous solution to decompose the highly water-absorbent polymer. From the first ozone treatment step S202 for producing the first ozone treatment liquid containing the removed pulp fiber and the decomposed product of the removed highly water-absorbent polymer, and the first ozone treatment liquid, the said The biogas production step S3 includes a separation step S203 for separating the pulp fibers, and the biogas production step S3 is the first ozone treatment liquid containing at least the pulp fibers separated and a decomposition product of the highly water-absorbent polymer as the treatment liquid. Is used.

A method of extracting pulp fibers containing a highly water-absorbent polymer from an inactivated aqueous solution containing crushed used sanitary products (S201), in other words, separating an inactivated aqueous solution containing a highly water-absorbent polymer, synthetic resin material and excrement. The method is not particularly limited, and a known method can be appropriately selected depending on the type and size of the member to be separated. Examples of the separation method include a method using a screen separator or a centrifuge. Further, the type and order of separation of the members to be separated are not particularly limited, and a plurality of types of members may be separated at the same time in one separation step, or only one type of member may be separated.

As a method (S202) of ozone-treating pulp fibers containing a highly water-absorbent polymer in an aqueous solution, any method can be used as long as the pulp fibers (containing the highly water-absorbent polymer) can be brought into contact with ozone in the aqueous solution. There are no particular restrictions. As a method thereof, for example, in a treatment tank in which an aqueous solution containing pulp fibers is stored, microbubble-like ozone gas is released from below the treatment tank while stirring the aqueous solution to bring the pulp fibers into contact with zon. Can be mentioned. Alternatively, in an aspirator (ejector) in which a supply port and an discharge port are connected to a treatment tank in which an aqueous solution containing pulp fibers is stored, a gas containing ozone is circulated from the supply port to the discharge port while the aqueous solution containing pulp fibers is circulated. There is a method of bringing the pulp fiber into contact with ozone by sucking the pulp fiber from the suction port. Alternatively, there is a method in which ozone gas containing ozone and an aqueous solution containing pulp fibers are mixed at high speed in a turbo mixer pump and sent out into a treatment tank. Alternatively, a method in which one or a plurality of the above methods are continuously performed in series can be mentioned.

The method for separating pulp fibers from the first ozone treatment liquid (S203) is not particularly limited, and a known method can be appropriately selected according to the type and size of the member to be separated. For example, a screen separator can be used. The method to be used is mentioned, and a plurality of kinds of methods may be used in series.

In the above preferred embodiment, pulp fibers containing a highly water-absorbent polymer separated from used hygiene products are ozone-treated in an aqueous solution. As a result, the highly water-absorbent polymer adhering to the pulp fibers can be decomposed by ozone and contained in the first ozone treatment liquid as a decomposition product of the highly water-absorbent polymer. Therefore, the decomposition product of the highly water-absorbent polymer can be used as a raw material for biogas. At that time, even if the first ozone treatment liquid contains fine pulp fibers and organic substances derived from excrement that could not be completely separated, they are damaged by ozone and are decomposed in some cases. Since it is easily subjected to biological treatment, it can be used as a raw material for biogas. In this way, it is possible to increase the amount of waste that can be used as a raw material for biogas from among the wastes derived from used sanitary goods, so that biogas can be produced more efficiently. Furthermore, when the highly water-absorbent polymer is decomposed with ozone, the treatment liquid itself is sterilized. Therefore, when the decomposition product of the highly water-absorbent polymer or the first ozone treatment liquid is used as a raw material for biogas, biological treatment is performed. It can suppress bacteria that adversely affect the microorganisms used in. Thereby, the biogas can be produced more efficiently.

In another preferred embodiment of the present embodiment, the production step S2 separates the highly water-absorbent polymer, the synthetic resin material and the pulp fiber from the inactivated aqueous solution containing the crushed used sanitary ware. A separation step S211 for producing a mixed solution having the inactivated aqueous solution containing the excrement and the residual high water absorption polymer, and ozone treatment of the mixed solution to produce the excrement and the residual high water absorption. A second ozone treatment step S212 for producing a second ozone treatment liquid containing a decomposition product of a sex polymer is included, and the biogas production step S3 uses at least the second ozone treatment liquid as the treatment liquid. To produce biogas.

The method (S211) for separating the highly water-absorbent polymer, the synthetic resin material and the pulp fiber from the inactivated aqueous solution containing the crushed used sanitary goods is not particularly limited, and the type and size of the members to be separated are not particularly limited. A known method can be appropriately selected accordingly. Examples of the separation method include a method using a screen separator or a centrifuge. Further, the type and order of separation of the members to be separated are not particularly limited, and a plurality of types of members may be separated at the same time in one separation step, or only one type of member may be separated.

As a method (S212) of ozone-treating a mixed solution having an inactivated aqueous solution containing excrement and a residual highly water-absorbent polymer, a method in which the excrement or the highly water-absorbent polymer and ozone can come into contact with each other in the mixed solution. If so, there are no particular restrictions. The method is as described in, for example, the method of ozone-treating pulp fibers containing a highly water-absorbent polymer in an aqueous solution (S202).

In another preferred embodiment described above, the mixed solution containing the inactivated aqueous solution containing the excrement and the residual highly water-absorbent polymer separated from the used sanitary goods is ozone-treated. As a result, not only the excrement but also the highly water-absorbent polymer remaining in the mixed solution can be used as a raw material for biogas as a decomposition product of the highly water-absorbent polymer. Further, at that time, even if fine pulp fibers that could not be completely separated are present in the second ozone treatment liquid, they are damaged by ozone and are decomposed in some cases, so that the biological treatment is performed. Since it is easily used, it can be used as a raw material for biogas. In this way, it is possible to increase the amount of waste that can be used as a raw material for biogas from among the wastes derived from used sanitary goods, so that biogas can be produced more efficiently. Furthermore, when the highly water-absorbent polymer is decomposed with ozone, the treatment liquid itself is sterilized. Therefore, when the decomposition product of the highly water-absorbent polymer or the second ozone treatment liquid is used as a raw material for biogas, biological treatment is performed. It can suppress bacteria that adversely affect the microorganisms used in. Thereby, the biogas can be produced more efficiently.

As another preferred embodiment of the present embodiment, the production step S2 is carried out in an inactivated aqueous solution.
In this embodiment, since not only the pulverization step but also the production step is carried out in the inactivated aqueous solution, the highly water-absorbent polymer in the used hygiene product is further dehydrated, and the excrement contained in the highly water-absorbent polymer is highly water-absorbent. It can be released from the polymer to the outside. Thereby, the excrement released from the highly water-absorbent polymer can also be used as a raw material for biogas. In this way, it is possible to increase the amount of waste that can be used as a raw material for biogas from among the wastes derived from used sanitary goods, so that biogas can be produced more efficiently.

As another preferred embodiment of the present embodiment, the inactivated aqueous solution contains an organic acid.
In this aspect, the inactivated aqueous solution contains an organic acid. Therefore, the organic acid can also be used as a raw material for biogas. In this way, it is possible to increase the amount of waste that can be used as a raw material for biogas from among the wastes derived from used sanitary goods, so that biogas can be produced more efficiently.

As another preferred embodiment of the present embodiment, the organic acid comprises citric acid.
In this aspect, citric acid is used as the organic acid in the inactivated aqueous solution. Therefore, by using the citric acid as a raw material for biogas, biogas can be produced more efficiently.

Next, in order to recycle the highly water-absorbent polymer, pulp fiber and synthetic resin material of the used sanitary goods according to the embodiment, the highly water-absorbent polymer, pulp fiber and synthetic resin material are selected from the used sanitary goods including excrement. An example of the method of collecting will be described. The method for recovering the highly water-absorbent polymer, pulp fiber and synthetic resin material from used sanitary goods containing excrement is not particularly limited, and for example, the following method can be used.

FIG. 4 is a block diagram showing an example of the recycling system 1 according to the present embodiment. The recycling system 1 includes a recycling device 10 for recovering highly water-absorbent polymer, pulp fiber and synthetic resin material (film, non-woven fabric d) from used hygiene products. The recycling device 10 includes a bag breaking device 11 to a pH adjusting device 23, and may further include a water storage tank 24 and a recovery device 25. FIG. 5 is a flowchart showing an example of the recycling method according to the embodiment. The recycling method includes a recycling step S10 for recovering a highly absorbent polymer, pulp fiber and synthetic resin material from used sanitary goods. The recycling step S10 includes a drilling step S11 to a pH adjusting step S23, and may further include a second resupply step S24 and a first resupply step S25. To. Hereinafter, each step will be specifically described.

In this embodiment, used sanitary goods are collected / acquired from the outside for reuse (recycling) and used. At that time, a plurality of used hygiene products are enclosed in a collection bag so that excrement, fungi, and odors do not leak to the outside. The individual used hygiene products in the collection bag are mainly rolled up with a surface sheet on which excrement is excreted so that excrement and fungi are not exposed on the front side and odor does not spread to the surroundings. It is collected in a folded state.

The drilling step S11 is executed by the bag breaking device 11. The bag breaking device 11 includes a solution tank for storing an inactivating aqueous solution containing an inactivating agent, and a bag breaking blade that rotates in the solution tank. The bag-breaking device 11 makes a hole in the collection bag put into the solution tank with a bag-breaking blade in an inactivated aqueous solution. As a result, a mixed solution 91 of the collection bag in which the inactivated aqueous solution has penetrated through the holes and the inactivated aqueous solution is generated. The inactivated aqueous solution inactivates the highly absorbent polymer of the used absorbent article in the collection bag. Hereinafter, a case where an acidic aqueous solution is used as the inactivating aqueous solution will be described as an example.

The crushing step S12 is executed by the crushing device 12. The crusher 12 includes a twin-screw crusher. The crushing device 12 crushes the collection bag containing the used sanitary goods of the mixed liquid 91 together with the collection bag. As a result, a mixed solution 92 having a crushed product of a collection bag containing a used absorbent article and an acidic aqueous solution is produced, and almost all highly absorbent polymers of used hygiene products are inactivated. However, the crushed material includes pulp fibers and highly water-absorbent polymers, and other materials (eg, synthetic resin materials such as films, non-woven fabrics, collection bags).

The crushing step S12, or the drilling step S11 and the crushing step S12 can be referred to as a crushing step S1.

The first separation step S13 is executed by the first separation device 13. The first separation device 13 includes a pulper separator having a stirring separation tank that functions as a washing tank and a sieving tank. The first separation device 13 stirs the mixed solution 92 to remove excrement and the like from the crushed material, and separates the pulp fiber, the highly water-absorbent polymer, the excrement and the acidic aqueous solution from the mixed solution 92. As a result, a mixed solution 93 containing pulp fibers, a highly water-absorbent polymer, excrement, and an acidic aqueous solution is produced, and materials such as films, non-woven fabrics, and collection bags of used absorbent articles are recovered. These materials can be reused as solid fuel or the like by being melted and solidified after being washed with washing water, for example.

The first dust removing step S14 is executed by the first dust removing device 14. The first dust remover 14 includes a screen separator, and separates the mixed liquid 93 into pulp fibers, a highly water-absorbent polymer and excrement in an acidic aqueous solution and other materials (foreign substances) by a screen. As a result, a mixed solution 94 containing pulp fibers, a highly absorbent polymer, excrement and an acidic aqueous solution in which the amount of foreign matter is reduced is produced, and other materials are removed.

The second dust removing step S15 is executed by the second dust removing device 15. The second dust remover 15 is provided with a screen separator, and the mixture 94 is used as a screen finer than the first dust remover 14, and is a pulp fiber, a highly water-absorbent polymer, excrement, and other materials (small foreign substances) in an acidic aqueous solution. Separate into and. As a result, a mixed solution 95 containing pulp fibers, a highly absorbent polymer, excrement and an acidic aqueous solution in which the amount of foreign matter is further reduced is produced, and other materials are further removed.

The third dust removing step S16 is executed by the third dust removing device 16. The third dust remover 16 is provided with a cyclone separator, and separates the mixture 95 into pulp fibers, a highly water-absorbent polymer and excrement in an acidic aqueous solution and other materials (foreign substances having a heavy specific gravity) by centrifugation. .. As a result, a mixed solution 96 containing pulp fibers, a highly water-absorbent polymer, excrement and an acidic aqueous solution in which the amount of foreign matter is further reduced is produced, and other materials having a high specific gravity are removed.

At least one of the first dust removing device 14 to the third dust removing device 16 may be omitted depending on the state of the mixed liquid 92 and the like (example: amount and size of foreign matter).

The second separation step S17 is executed by the second separation device 17. The second separation device 17 includes a drum screen separator, and separates the mixture 96 into a highly water-absorbent polymer in an acidic aqueous solution and pulp fibers by a drum screen. As a result, a mixture 97 containing a highly water-absorbent polymer, excrement and an acidic aqueous solution is produced, and pulp fibers are removed as the mixture 98.

The third separation step S18 is executed by the third separation device 18. The third separation device 18 includes an inclined screen, and separates the mixture 97 into a solid containing a highly water-absorbent polymer and a liquid containing excrement and an acidic aqueous solution by the screen. As a result, the super absorbent polymer (SAP) is recovered, and a mixed solution 101 containing an acidic aqueous solution containing excrement, a superabsorbent polymer remaining unseparable, and a decomposition product of the polymer absorbent polymer is generated. To.

The first oxidant treatment step S19 is executed by the first oxidant treatment apparatus 19. The first oxidant treatment device 19 includes a treatment tank for storing the oxidant aqueous solution and an oxidant supply device for supplying the oxidant into the treatment tank. The first oxidant treatment apparatus 19 puts the mixture 98 into the treatment tank from the upper part or the lower part of the treatment tank and mixes it with the oxidant aqueous solution in the treatment tank. Then, the highly water-absorbent polymer contained in the pulp fibers is decomposed in the oxidant aqueous solution by the oxidant supplied from the lower part of the treatment tank by the first oxidant supply device, and solubilized in the oxidant aqueous solution. As a result, a mixed solution 99 having a pulp fiber from which the highly water-absorbent polymer has been removed and an aqueous solution of an oxidizing agent containing a decomposition product of the highly water-absorbent polymer is produced. The oxidizing agent is an oxidizing agent capable of decomposing a highly water-absorbent polymer, and examples thereof include ozone. Ozone has high bactericidal and bleaching powers and is preferable. In the first oxidizing agent treatment step S19, a plurality of treatments may be continuously performed from the viewpoint of more reliably performing the decomposition treatment of the highly water-absorbent polymer.

The ozone concentration in the oxidant aqueous solution is preferably 1 to 50 parts by mass. If the concentration is too low, the highly absorbent polymer cannot be completely solubilized, and the highly absorbent polymer may remain in the pulp fibers. If the concentration is too high, the pulp fibers may be damaged. The treatment time with the ozone is short when the ozone concentration in the aqueous oxidizing agent solution is high, and long when the ozone concentration is low, typically 5 to 120 minutes. The product of the ozone concentration (ppm) and the treatment time (minutes) in the oxidant aqueous solution (hereinafter, also referred to as “CT value”) is preferably 100 to 6000 ppm · min. If the CT value is too small, the highly absorbent polymer cannot be completely solubilized, and if the CT value is too large, the pulp fibers may be damaged.

When ozone is used as the oxidizing agent, the first oxidizing agent supply device is an ozone supply device, and supplies ozone-containing gas, which is a gaseous substance, to the treatment tank. The nozzle of the ozone supply device is arranged at the bottom of the treatment tank, and supplies the ozone-containing gas as a plurality of fine bubbles into the oxidant aqueous solution. As the oxidant aqueous solution, an acidic aqueous solution is preferable from the viewpoint of suppressing the inactivation of ozone and inactivating the highly water-absorbent polymer. Furthermore, when an acidic aqueous solution is used as the inactivated aqueous solution in the crushing treatment or dust removal treatment, since there is continuity between each treatment, the aqueous solution can be used without waste, the amount of water can be reduced, and it is stable. Processing can be performed accurately and reliably. Further, as the acid used for the acidic aqueous solution, and therefore the acid used as the inactivating agent for the inactivating aqueous solution, an organic acid is preferable from the viewpoint of reducing the influence of the acid on workers and equipment, and among them, a metal. Citric acid is preferred from the standpoint of removal.

The ozone concentration in the aqueous solution of the oxidizing agent is not particularly limited as long as it can decompose the highly water-absorbent polymer, but is preferably 1 to 50 mass ppm. If the concentration is too low, the highly absorbent polymer cannot be completely solubilized, and the highly absorbent polymer may remain in the pulp fibers. If the concentration is too high, the pulp fibers may be damaged. The treatment time in the first oxidant treatment apparatus 19 is not particularly limited as long as it can decompose the highly water-absorbent polymer, but it is short if the ozone concentration in the oxidant aqueous solution is high, and if the ozone concentration is low. Lengthen, typically 5 to 120 minutes. The product of the ozone concentration (ppm) in the oxidant aqueous solution and the treatment time (minutes) of the treatment step (hereinafter, also referred to as “CT value”) is preferably 100 to 6000 ppm · min. If the CT value is too small, the highly water-absorbent polymer cannot be completely solubilized and the high water-absorbent polymer may remain in the pulp fibers, and if the CT value is too large, the pulp fibers may be damaged.

The fourth separation step S20 is executed by the fourth separation device 20. The fourth separation device 20 includes a screen separator, and separates the mixture 99 into pulp fibers and an aqueous solution of an oxidizing agent by a screen. As a result, pulp fibers are produced, and a mixed solution 104 of an aqueous oxidant solution containing a decomposition product of a highly water-absorbent polymer is delivered. The mixed solution 104 can be said to be a first ozone treatment solution (FIG. 5) containing pulp fibers from which the highly water-absorbent polymer has been decomposed and removed, and a decomposition product of the highly water-absorbent polymer that has been removed.

In the first resupply step S25, the mixture 104 separated in the fourth separation step S20 is resupplied to the first oxidant treatment step S19 (first oxidant treatment apparatus 19) by a liquid feed pump or the like. It is reused as an oxidizer aqueous solution. In addition, the washing water which washed the pulp fiber separated may be mixed with the mixed liquid 104. Further, the mixed solution 104 may be mixed with the mixture 98 and then re-supplied to the first oxidant treatment step S19 (first oxidant treatment device 19) before returning to the first oxidant treatment device 19. In this way, the mixed solution 104, that is, the oxidant aqueous solution is used cyclically, so that the amount of water used for the oxidant aqueous solution can be reduced.

The second oxidant treatment step S22 is executed by the second oxidant treatment apparatus 22. The second oxidant treatment device 22 includes a treatment tank for storing an aqueous solution (eg, an acidic aqueous solution as an inactivating aqueous solution, a part of a pre-treated mixed solution 101, etc.) and an oxidant in the aqueous solution in the treatment tank. It is equipped with an oxidant supply device for supplying. The second oxidant treatment device 22 puts the mixed liquid 101 supplied from the third separation device 18 into the treatment tank from the upper part or the lower part of the treatment tank and mixes it with the aqueous solution in the treatment tank. In addition to the acidic aqueous solution, the mixed solution 101 contains excrement, a super absorbent polymer that could not be completely removed, and a decomposition product of the polymer absorbent polymer having a relatively large molecular weight. Its viscosity is relatively high (example: 8 mPa · s or more). The second oxidant treatment device 22 is an oxidant supplied from the lower part of the treatment tank by the oxidant supply device, and decomposes organic substances having a relatively large molecular weight such as excrement contained in the aqueous solution into an aqueous solution. Solubilize. As a result, a mixed solution 102 having an acidic aqueous solution containing an organic substance having a relatively small molecular weight is produced. The viscosity of the mixture 102 is relatively low (eg, less than 5 mPa · s). In addition, sterilization can be performed as well as decomposition and solubilization. However, the oxidizing agent is an oxidizing agent capable of decomposing an organic substance having a relatively large molecular weight such as excrement, and examples thereof include ozone, which is preferable because of its high bactericidal activity and bleaching ability.

When ozone is used as the oxidant, the oxidant supply device is an ozone supply device, as in the case of the first oxidant treatment device 19, and supplies ozone-containing gas, which is a gaseous substance, to the treatment tank. From the viewpoint of more reliably performing the decomposition treatment of the highly water-absorbent polymer, the second oxidant treatment device 22 may be connected in series and the treatment may be continuously performed a plurality of times.

In the present embodiment, the second oxidant treatment apparatus 22 performs at least two stages of treatment. The first-stage treatment is performed by a liquid feed pump (eg, turbo mixer pump) capable of mixing ozone, which is arranged in front of the treatment tank. In order to improve efficiency, this first-stage process mixes ozone and mixed solution 101 at high speed in the liquid feeding pump to make ozone into microbubbles, and then temporarily at the outlet of the liquid feeding pump. By pressurizing the ozone, the efficiency of dissolving ozone in the mixed solution 101 is enhanced. As a result, the contact efficiency between the organic substance having a relatively large molecular weight and ozone is increased, and the decomposition efficiency of the organic substance is enhanced. However, if the amount of organic matter is too large and the viscosity of the mixture 101 becomes too high, the microbubbles may be difficult to disappear, and a foaming state (paste-like state) may occur, making it difficult to reuse as an acidic aqueous solution. .. Therefore, as the second stage treatment, the mixture 101 containing the ozone microbubbles sent from the above liquid feed pump is sent to the treatment tank, and a relatively large ozone gas bubble (example: diameter 1 mm or more) is sent by the ozone supply device. Is supplied to the mixed solution 101 from below the treatment tank. By bubbling ozone gas in the mixed liquid 101 in this way, the decomposition of the organic matter can be further promoted, and the decomposition efficiency of the organic matter can be further improved. As a result, the viscosity of the mixed liquid 101 can be further reduced, and the remaining microbubbles can be easily removed from the mixed liquid 101 by adhering to or being absorbed by the large bubbles. As a result, a reusable mixed solution 101, that is, a mixed solution 102 in which the organic matter is decomposed is produced.

If the viscosity of the mixed solution 101 does not become too high, either one of the first step and the second step can be omitted. Alternatively, the first-stage processing may be omitted, the first-stage and second-stage processing may be combined, and the microbubbles may be used in the second-stage processing. Further, also in the first oxidant treatment apparatus 19, a two-step treatment such as the second oxidant treatment apparatus 22 may be used, or one of the first stage and the second stage treatment, or A process in which both are combined may be used.

The ozone concentration in the acidic aqueous solution is not particularly limited as long as it can decompose the highly water-absorbent polymer, but is preferably 1 to 50 mass ppm. If the concentration is too low, the organic substance having a relatively large molecular weight cannot be completely solubilized, and the viscosity of the acidic aqueous solution may be difficult to decrease. If the concentration is too high, the equipment may be damaged. The treatment time in the second oxidant treatment apparatus 22 is not particularly limited as long as it can decompose an organic substance having a relatively large molecular weight, but it is short if the ozone concentration in the acidic aqueous solution is high, and the ozone concentration is low. Longer, typically 5 to 120 minutes. The product of the ozone concentration (ppm) in the acidic aqueous solution and the treatment time (minutes) of the treatment step (hereinafter, also referred to as “CT value”) is preferably 100 to 6000 ppm · min. If the CT value is too small, organic substances having a relatively large molecular weight cannot be completely solubilized, and the viscosity of the acidic aqueous solution may be difficult to decrease. If the CT value is too large, the equipment may be damaged.

The pH adjusting step S23 is executed by the pH adjusting device 23. The pH adjusting device 23 includes, for example, a treatment tank for adjusting pH, a pH sensor for measuring the pH of an aqueous solution (or an aqueous solution of an oxidizing agent) in the processing tank, and a pH adjusting agent supplying a pH adjusting agent in the processing tank. It is equipped with a device. For example, the pH adjusting device 23 supplies the mixed solution 102 supplied from the second oxidizing agent processing device 22 to the processing tank, and if the pH of the mixed solution 102 is not within a predetermined pH range, the pH adjusting agent is processed. The pH is adjusted by supplying the mixture 102 in the tank. As a result, a pH-adjusted mixed solution 102, that is, a mixed solution 103 is produced. The mixed solution 103 can be said to be a reusable acidic aqueous solution in which organic substances are decomposed, and is a second ozone treatment solution (FIG. 5) containing excrement and a residual decomposition product of a highly water-absorbent polymer. Can be done. The pH adjuster is not particularly limited as long as the pH can be adjusted, but water for raising the pH of the acidic aqueous solution (approaching neutrality) and water for lowering the pH (making it more acidic). Citric acid can be mentioned. If the pH of the mixed solution 101 is stable, the pH adjusting device 23 may not be used. In that case, the mixed liquid 102 can be said to be the second ozone treatment liquid.

The mixed solution 103 in which the pH adjuster is adjusted, that is, the reusable acidic aqueous solution is re-supplied to the recycling device 10 (such as the bag-breaking device 11 or the crushing device 12 or the first separation device 13) and reused. To.

The water storage tank 24 stores the portion of the mixed liquid 103 that is not reused. Further, the recovery device 25 is an inactivating agent (eg, an organic acid such as citric acid) or an inactivating aqueous solution (eg, citric acid aqueous solution) from the mixed solution 105, which is the mixed solution 103 stored in the water storage tank 24. Organic acid aqueous solution) is recovered.

In the second resupply step S24 (resupply step), the mixed solution 103 (acidic aqueous solution) whose pH is adjusted to a predetermined pH range in the pH adjusting step S23 is recycled into the recycling device 10 (example:: It is re-supplied to the drilling step S11, the crushing step S12, and the first separation step S13) and reused as an inactivating aqueous solution. In this way, the mixed liquid 103, that is, the acidic aqueous solution is cyclically used, so that the amount of water used for the acidic aqueous solution can be reduced. The mixed liquid 103 may be supplied to another step (device) if necessary. The surplus of the mixed liquid 103 is stored in the water storage tank 24.

When the amount of the component other than the acidic aqueous solution of the mixed solution 103 increases, the viscosity of the mixed solution 103 becomes relatively high even if the component is an organic substance having a relatively small molecular weight, and the second oxidizing agent treatment is performed. Even in step S22, it may be difficult to keep the viscosity relatively low. In that case, the organic acid aqueous solution can be reused by removing impurities (excrement, etc.) by the method for recovering the organic acid aqueous solution described later.

By the above method, in order to recycle the highly water-absorbent polymer, pulp fiber and synthetic resin material of the used sanitary goods according to the embodiment, the highly water-absorbent polymer, pulp fiber and synthetic resin from the used sanitary goods including excrement are recycled. The material can be recovered. At the same time, by this method, as a treatment liquid containing excrement and a decomposition product of the highly water-absorbent polymer, for example, a mixed liquid 104 which is a first ozone treatment liquid and / or a mixed liquid which is a second ozone treatment liquid. 103 (or 102) can be generated.

In this embodiment, the oxidizing agent is ozone, but other oxidizing agents such as chlorine dioxide, hydrogen peroxide, hypochlorous acid, salts of hypochlorous acid, and at least one of peracetic acid may be contained. Good. These oxidizing agents can decompose the highly water-absorbent polymer to reduce the molecular weight by the oxidizing action, whereby the highly water-absorbent polymer can be effectively used for biogas production in the form of a decomposition product. ..

Further, another method for producing biogas of the embodiment regenerates the acidic aqueous solution in the mixed solution 103 (mixed solution 105) generated when recovering the highly water-absorbent polymer or the like from the used sanitary goods, and then regenerates the acidic aqueous solution. The discharged waste or the regenerated acidic aqueous solution is used for the production of biogas. Specifically, it is as shown below.

Hereinafter, an example of a method for regenerating the organic acid in the mixed liquid 103 (mixed liquid 105) produced when recovering the highly water-absorbent polymer or the like from the used sanitary goods according to another embodiment will be described. When the acidic aqueous solution of the mixed solution 105 is an organic acid aqueous solution, impurities (excretions, etc.) in the organic acid aqueous solution can be removed and recovered as a relatively high-purity organic acid aqueous solution 107 by the recovery method shown below. .. FIG. 6 is a flowchart showing an example of a method for recovering an aqueous organic acid solution according to another embodiment.

The method of recovering the organic acid aqueous solution is carried out by the recovery device 25. The method includes a precipitation step S31, a mixture collection step S32, an organic acid generation step S33, and an organic acid aqueous solution acquisition step S34. In the precipitation step S31, a water-insoluble salt of an organic acid is precipitated by adding a metal salt containing a divalent or higher-valent metal or a base containing a divalent or higher-valent metal to the organic acid aqueous solution of the mixed solution 105. In the mixture collection step S32, a solid substance, which is a mixture of a water-insoluble salt of an organic acid and a solid excrement derived from excrement, is collected from the aqueous organic acid solution that has undergone the precipitation step, and the liquid substance 106 is separated. In the organic acid production step S33, an aqueous solution containing a free organic acid, an acid capable of producing a water-insoluble salt, and water is added to the solid substance, and the organic acid, the water-insoluble salt, and the solid excrement are contained. To form. The organic acid aqueous solution acquisition step S34 removes water-insoluble salts and solid excreta from the aqueous solution to obtain an organic acid aqueous solution 107 containing an organic acid.

In the precipitation step S31, a metal salt containing a divalent or higher metal or a base containing a divalent or higher metal in the organic acid aqueous solution of the mixed solution 105 containing the excrement and the organic acid stored in the water storage tank 24 (hereinafter, By adding (also referred to as "salt for producing water-insoluble salt"), (i) a water-insoluble salt of an organic acid and excreta, that is, (ii) solid excrement and (iii) liquid excrement, (iii) iv) Obtain an organic acid aqueous solution containing an aqueous salt. Examples of the divalent or higher valent metal constituting the water-insoluble salt-forming base include Mg, Ca, Ba, Fe, Ni, Cu, Zn and Al, and a group consisting of any combination thereof. Examples of the base for producing a water-insoluble salt include magnesium hydroxide, calcium hydroxide, copper hydroxide, zinc hydroxide and the like. The water-insoluble salt-forming base is added in an amount preferably 0.8 to 3.0 times the equivalent of the organic acid. (I) From the viewpoint of forming a water-insoluble salt of an organic acid. In the precipitation step S31, (i) a water-insoluble salt of the organic acid is formed, and the salt crystallizes and precipitates. At that time, of the (ii) solid excreta dispersed in the organic acid aqueous solution, fine ones adhere to the surface of (i) the water-insoluble salt of the organic acid, and (i) the organic acid is water-insoluble. It is taken up by the crystals of the sex salt and aggregates. Therefore, in the mixture collection step S32, fine (ii) solid excrement is collected as solid [(i) water-insoluble salt of organic acid and (ii) solid excrement], and liquid 106 [(iii). It is less likely to be contained in liquid excrement and (iv) water-soluble salt]. As a result, the concentration of suspended solids (SS) in the liquid material 106 becomes low, and it becomes difficult for the filter and the like to be clogged during the solid-liquid separation for separating the liquid material 106 and the solid material, and the liquid material 106 is separated. The amount of sludge generated during microbial treatment is reduced.

In the mixture collection step S32, the organic acid aqueous solution that has undergone the precipitation step S31 is mixed with a solid substance [(i) a water-insoluble salt of an organic acid and (ii) solid excrement] and a liquid substance 106 [(iii) liquid excrement. It is separated into the substance and (iv) water-soluble salt]. Since the liquid substance 106 contains liquid excrement, it can be used for producing biogas.

In the organic acid production step S33, an acid capable of producing a free organic acid and a water-insoluble salt (hereinafter, also referred to as “free organic acid-producing acid”) and water are added to the solid substance (v). ) Form an aqueous solution containing an organic acid, (vi) a water-insoluble salt, and (ii) solid excreta. The free organic acid generated acid can be an acid dissociation constant (pK _a, water) the organic acid is an acid having a smaller acid dissociation constant than (pK _a, water) preferably the organic or inorganic acid, and It is preferably an inorganic acid. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, nitric acid, iodic acid, bromic acid and the like. The free organic acid-producing acid is added in an amount preferably 0.8 to 2.0 times equivalent to the organic acid. This is from the viewpoint of (i) converting the water-insoluble salt of the organic acid into (v) the organic acid in the free state. As the water used here, for example, a part or all of the solution corresponding to the amount of the washing water separated from the mixed solution 104 may be used.

In the organic acid aqueous solution acquisition step S34, a solid substance, that is, (vi) water-insoluble salt and (ii) solid excrement are removed from the aqueous solution, and a liquid substance, that is, (v) an organic acid is contained (vii). An aqueous organic acid solution 107 is obtained. Since the organic acid aqueous solution 107 contains an organic acid (eg, citric acid), it can be used for producing biogas.

The absorbent article of the present invention is not limited to the above-described embodiments, and can be appropriately combined or modified as long as it does not deviate from the object and purpose of the present invention.

S1 crushing process S2 production process S3 biogas manufacturing process

Claims (6)

A method for producing biogas using wastes derived from used sanitary products, including highly absorbent polymers, pulp fibers, synthetic resin materials and excrement.
A crushing step of crushing the used sanitary goods in an inactivating aqueous solution capable of inactivating the highly water-absorbent polymer, and
A treatment in which the highly water-absorbent polymer, the pulp fiber and the synthetic resin material are separated from the inactivated aqueous solution containing the crushed used hygiene product, and the excrement and the decomposition product of the highly water-absorbent polymer are contained. The production process to generate the liquid and
A biogas manufacturing process for producing biogas using the treatment liquid, and
To prepare
Method. The production step is
The inactivated aqueous solution containing the crushed used sanitary goods is separated from the inactivated aqueous solution containing the highly water-absorbent polymer, the synthetic resin material and the excrement, and the highly water-absorbent polymer is contained. The extraction process to take out the pulp fiber and
The pulp fiber containing the highly water-absorbent polymer was ozone-treated in an aqueous solution to decompose and remove the highly water-absorbent polymer, and a decomposition product of the removed highly water-absorbent polymer. A first ozone treatment step for producing a first ozone treatment liquid containing
A separation step for separating the pulp fibers from the first ozone treatment liquid, and
Including
In the biogas production step, the first ozone treatment liquid in which at least the pulp fibers are separated and containing a decomposition product of the highly water-absorbent polymer is used as the treatment liquid.
The method according to claim 1. The production step is
The highly water-absorbent polymer, the synthetic resin material and the pulp fiber are separated from the inactivated aqueous solution containing the crushed used hygiene product, and the excrement and the residual highly water-absorbent polymer are contained. A separation step to generate a mixed solution with an inactivated aqueous solution, and
A second ozone treatment step of treating the mixed liquid with ozone to generate a second ozone treatment liquid containing the excrement and the residual decomposition product of the highly water-absorbent polymer.
Including
In the biogas production step, biogas is produced using at least the second ozone treatment liquid as the treatment liquid.
The method according to claim 1. The production step is carried out in the inactivated aqueous solution.
The method according to any one of claims 1 to 3. The inactivated aqueous solution contains an organic acid.
The method according to claim 4. The organic acid includes citric acid.
The method according to claim 5.

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