Method for manufacturing nutrient salt sustained-release block and nutrient salt sustained-release block

Abstract

Provided are: a method for manufacturing a nutrient salt sustained-release block that utilizes recycled resources and enables nutrient salts to be supplied in a targeted manner over a long period of time; and the nutrient salt sustained-release block. A method for manufacturing a nutrient salt sustained-release block according to the present invention is a method for manufacturing a concrete block capable of releasing nutrient salts in a sustained manner. The method includes a step in which concrete raw materials and a recycled phosphorus compound (5) recovered in a resource recycling process are contained in the composition of the concrete block, wherein the content of the recycled phosphorus compound (5) in the concrete block is adjusted so that the compressive strength of the concrete block is 18 N / mm2 or more.

Description

Manufacturing method of nutrient salt sustained release block and nutrient salt sustained release block

[0001] The present invention relates to a method for producing a nutrient salt sustained-release block and a nutrient salt sustained-release block.

[0002] The impact of global warming caused by carbon dioxide emissions from socioeconomic activities is becoming more pronounced, and decarbonization efforts to mitigate this are being considered. Energy-saving technologies that reduce carbon dioxide emissions from power generation and renewable energy technologies such as solar and wind power have been developed and are now in the social implementation phase. Furthermore, development is underway on direct air capture (DAC) technology, which directly captures atmospheric carbon dioxide from the air, as a carbon-negative technology to promote decarbonization.

[0003] While industrial-based DAC technologies using absorbents and other materials are currently at the forefront, research is also underway into nature-based technologies such as green carbon, which is DAC in forests, and blue carbon, which is DAC in marine ecosystems. These nature-based technologies are expected to be relatively inexpensive and may also have the added benefit of improving the environment beyond just global warming.

[0004] Blue carbon, in particular, is a technological field that has seen accelerated research in recent years due to its advantages over green carbon, such as a greater potential for carbon capture and a longer carbon fixation period. It has been scientifically proven that carbon capture using blue carbon takes place in marine ecosystems such as seagrass and algae beds, mangrove forests, salt marshes, and phytoplankton breeding areas, and a wide range of knowledge is currently being accumulated.

[0005] Carbon dioxide capture through blue carbon is quantified through ocean monitoring, ultimately converted into carbon offset credits, and traded in the carbon dioxide emissions market. In the above-mentioned ocean monitoring, for example, the area of ​​seaweed beds and mangrove forests is generally assessed using underwater measurements and satellite remote sensing. Assuming that this area is proportional to the amount of carbon dioxide absorbed, carbon offsets are granted according to the amount of area maintained and expanded.

[0006] The area of ​​seaweed beds and mangrove forests in the target marine areas is affected by several factors, but it is known that the main factors are the nutrients necessary for the proliferation of seaweed, marine algae, and mangroves, namely nitrogen and phosphorus.For this reason, carbon offsets from seaweed beds and mangrove forests maintained and expanded through appropriate nutrient management in the target marine areas will be awarded to the entities implementing measures related to nutrient management.

[0007] There are several sources of nutrients in the coastal waters of the target sea area, with sewage treatment plants and wastewater treatment facilities being the main sources. If carbon offsets were granted through measures to properly manage the amount of nutrients supplied to the sea area where they are discharged, it would provide an incentive for the operators of sewage treatment plants and wastewater treatment facilities to optimize the quality of treated water for nitrogen and phosphorus, and it is expected that efforts to contribute to decarbonization will become even more active. Furthermore, methods of supplying nutrients to the sea area are not limited to the effluent from sewage treatment plants as mentioned above, but methods using materials and equipment (equipment and materials) that can be used to prioritize supply to areas where they are needed are also being considered.

[0008] Nutrients from effluents from sewage treatment plants and other facilities are transported and diffused in the ocean areas where they are discharged, helping to improve the nutrient concentration levels throughout the ocean. In such cases, it can be difficult to selectively supply nutrients to areas where they are most needed, such as seaweed beds or aquaculture farms.

[0009] Furthermore, the nutrient concentration in effluent from sewage treatment plants fluctuates depending on the quantity and quality of sewage flowing into the plant at any given time, as well as seasonal fluctuations in water temperature and the activity of sewage treatment microorganisms (activated sludge). Therefore, it can be difficult to provide sufficient amounts of nutrients for the growth of marine ecosystems. One known way to solve or mitigate these problems is to install equipment that can locally supply nutrients to areas where they are needed.

[0010] For example, Patent Document 1 (Patent Document 1) exemplifies a sustained-release component that releases nutrients containing nitrogen, phosphorus, and iron over a long period of time. Specifically, Patent Document 1 discloses a sustained-release component having at least a first layer containing an iron-containing component and a second layer containing a chelating agent laminated on the surface of the first layer. Patent Document 1 also describes the use of a biodegradable material, specifically a resin film containing an iron-containing component and a biodegradable resin, as the first layer. Patent Document 1 also describes the use of a biodegradable material, specifically a mixed paper containing a cellulose-based material and a chelating agent, as the second layer. This method is expected to enable pinpoint delivery of nutrients to areas where they are needed by placing the equipment in appropriate locations.

[0011] Furthermore, Patent Document 2 discloses a nutrient supplying material made by mixing shells with digestive fluid obtained by methane fermentation of sewage sludge, livestock excrement, etc. This material and equipment can procure some of the nutrients used from materials recovered from waste such as sewage sludge, making it a desirable means of utilizing recycled resources.

[0012] JP 2022-149442 A JP 2023-176981 A

[0013] As mentioned above, the technology disclosed in Patent Document 1 is expected to eliminate or alleviate the objective of pinpointing the long-term supply of nutrients to areas where they are needed. Furthermore, the technology disclosed in Patent Document 2 is expected to eliminate or alleviate the objective of utilizing renewable resources. However, for large-scale application of blue carbon for the purpose of carbon dioxide absorption and storage, it is necessary to simultaneously eliminate or alleviate both objectives from the perspective of applicability. Conventional technologies, including those in Patent Documents 1 and 2, have yet to establish an appropriate means of simultaneously eliminating or alleviating both objectives.

[0014] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a nutrient salts sustained-release block and a nutrient salts sustained-release block that utilizes recycled resources and can supply nutrients to areas where they are needed for a long period of time with pinpoint accuracy.

[0015] The present invention provides a sustained-release (gradual release and sustained effect) material that utilizes recycled phosphorus compounds recovered from sewage treatment processes as a means to simultaneously alleviate and resolve the aforementioned issues of long-term supply to required locations and sustainable utilization of recycled resources. From a practical standpoint, it is required that the material be able to maintain a predetermined strength even when a nutrient salt additive (recycled phosphorus compound) is added to the base raw material (cement in this case). The present invention includes multiple means for achieving this, examples of which are as follows.

[0016] The method for producing a nutrient salts release block according to the present invention, which has solved the above-mentioned problems, is a method for producing a concrete block capable of releasing nutrients in a sustained manner, and the concrete block contains a concrete raw material and a recycled phosphorus compound recovered in a resource recycling process as a composition thereof, and the content of the recycled phosphorus compound in the concrete block is adjusted so that the compressive strength of the concrete block is 18 N / mm ２ The process includes adjusting the temperature so that the temperature is as described above.

[0017] According to the present invention, it is possible to provide a method for producing a nutrient salts sustained-release block that utilizes recycled resources and that can supply nutrients to areas where they are needed for a long period of time with pinpoint accuracy, and a nutrient salts sustained-release block.

[0018] Fig. 1 is a flow diagram illustrating a method for manufacturing a nutrient salts sustained-release block according to the present embodiment; Fig. 2 is a flow diagram illustrating an example of a flow of a block material adjustment process; Fig. 3 is a flow diagram illustrating an example of a flow of a recycled phosphorus compound content adjustment process; Fig. 4 is a graph illustrating an example of the relationship between the content of recycled phosphorus compounds in concrete block materials and the compressive strength of concrete blocks; Fig. 5 is a flow diagram illustrating an example of a flow of a block manufacturing process.

[0019] Hereinafter, a method for manufacturing a nutrient salts sustained-release block (hereinafter sometimes simply referred to as "this manufacturing method") and a nutrient salts sustained-release block (hereinafter sometimes simply referred to as "block") according to one embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description of the embodiment, substantially identical or similar components will be given the same reference numerals, and redundant descriptions may be omitted.

[0020] This manufacturing method and block are targeted at blue carbon, which is a method of direct air capture of carbon dioxide from the atmosphere related to decarbonization. This manufacturing method and block are a manufacturing technology for sustained-release materials that can supply nutrients over a long period of time, contributing to the maintenance and expansion of marine ecosystems such as seaweed beds, which are the main source of the capture effect.

[0021] <Method for Manufacturing Nutrient Release Blocks> In this embodiment, an example of a method for manufacturing a nutrient release block utilizing a recycled phosphorus compound manufactured through a resource recycling process is described. FIG. 1 is a flow diagram illustrating a method for manufacturing a nutrient release block according to this embodiment. In this manufacturing method, a recycled phosphorus compound 5 manufactured at a resource recycling facility 10 is used as one of the materials. The resource recycling facility 10 here refers to a facility that processes waste containing phosphorus, a fertilizer component, to make it usable for manufacturing fertilizers and blocks 20.

[0022] Specifically, the resource recycling facility 10 treats sewage sludge and wastewater sludge, which are condensed wastewater and sewage containing concentrated phosphorus. Crystallization is a typical treatment process used in the resource recycling facility 10. This crystallization process can produce, for example, magnesium ammonium phosphate (MAP), a phosphate fertilizer. Since Japan relies almost entirely on imports for the phosphorus resources used as industrial raw materials and fertilizers, utilizing phosphorus recycled from waste, i.e., recycled phosphorus compound 5, as in this embodiment, is important not only for resource recycling but also for mitigating competition for the use of valuable phosphorus resources. In addition to MAP, other recycled phosphorus compounds such as HAP (calcium hydroxyapatite) and ash-extracted calcium phosphate can also be used as the recycled phosphorus compound 5.

[0023] In the block production facility 100, the regenerated phosphorus compound 5 is used to produce blocks 20 in three steps shown in Figure 1: a block material preparation step 200, a regenerated phosphorus compound content adjustment step 300, and a block production step 400. These steps will be described in detail below.

[0024] FIG. 2 is a flow diagram illustrating an example of the block material preparation process 200. This process prepares the block 20 materials for use in the subsequent block production process 400. In the initial block material delivery process 210, the block 20 materials are delivered to the block production facility 100. Block 20 materials include at least cement, aggregate, and recycled phosphorus compound 5. Sand and gravel are typically used as aggregate. Other materials may be added depending on the purpose and application. For example, reusable waste material may include water purification soil, which is residue generated during water purification treatment at a water purification facility (not shown). Water purification soil is a mixture of turbidity components (mainly silicon) in raw water and flocculant components (such as aluminum hydroxide). By effectively utilizing this soil at a mixing ratio that ensures the mechanical strength of the resulting block 20 is within an acceptable range, it can also reduce the amount of cement used.

[0025] In the next block material particle size adjustment step 220, the particles are adjusted to a uniform particle size so as not to impair the material's compatibility or uniformity. Specifically, this is done by crushing or sieving. If the material already has been particle-sized at the time of the block material delivery step 210, this step can be omitted.

[0026] In the next block material weighing step 230, the mass or volume of each material is measured for the subsequent steps. This step can be omitted if the subsequent block manufacturing step 400 has the equipment to supply each material in a specified amount. This concludes the description of an example flow of the block material adjustment step 200.

[0027] 3 is a flow diagram showing an example of the process for adjusting the content of the recycled phosphorus compound 5 in the block 20. This process adjusts the content of the recycled phosphorus compound 5 in the block 20 so that the block 20 has the proper performance. The performance here refers to the compressive strength of the block 20.

[0028] In the regenerated phosphorus compound moisture content confirmation step 310, the moisture content of the regenerated phosphorus compound 5 delivered in the block material preparation step 200 is confirmed. The moisture content of the regenerated phosphorus compound 5 may be measured on-site at the storage location using a moisture content meter, or may be calculated by sampling a portion and calculating the moisture content from the mass before and after drying. If the moisture content of the regenerated phosphorus compound 5 is known at the time of delivery, this step can be omitted.

[0029] In the recycled phosphorus compound content upper limit confirmation step 320, the upper limit of the recycled phosphorus compound 5 content that allows the block 20 to satisfy a predetermined compressive strength is confirmed. The higher the recycled phosphorus compound 5 content, the better in order to dissolve more nutrients and supply them to the installation area, but this tends to decrease the compressive strength of the block 20. Therefore, in order to satisfy the predetermined compressive strength, the upper limit of the recycled phosphorus compound 5 content is determined and the content is set to be below that limit.

[0030] In this process, the upper limit of the content of the recycled phosphorus compound 5 is set based on the content P [mass %] of the recycled phosphorus compound 5 in the concrete block material and the compressive strength S [N / mm ２ ] can be used (S = F(P)). Here, the content P is the weight ratio of the recycled phosphorus compound 5 to the cement, which is the main material. FIG. 4 is a graph illustrating an example of the relationship between the content P of the recycled phosphorus compound 5 in the concrete block material and the compressive strength S of the concrete block. This relationship F provides a curve between the content P and the compressive strength S. This relationship F is prepared as a function approximation based on test data. Alternatively, rather than being a continuous function, it may be in the form of a data table listing the level of compressive strength S for the content P of the recycled phosphorus compound 5 divided into several numerical ranges. This relationship F may be prepared, for example, for each type of cement, which is the main raw material of the block 20, or for each type of aggregate, such as sand or gravel, which is the secondary material.

[0031] By using this relational expression F, the content P of the regenerated phosphorus compound 5 relative to the required compressive strength S of the block 20 can be calculated. Note that the content P here is a value based on the dry weight, not on the wet weight including moisture. The required compressive strength S of the block 20 is set to satisfy a predetermined standard value. In this manufacturing method, from the viewpoint of the versatility and performance of the block 20, the compressive strength S of the block 20 is set to 18 N / mm ２ The content P of the recycled phosphorus compound 5 that satisfies the compressive strength S is, for example, 5 to 10 mass %, but is not limited to this range. ２ If the content P of the regenerated phosphorus compound 5 is 5 to 10 mass %, the block 20 can contain more than 10 mass % of the regenerated phosphorus compound 5. When the content P of the regenerated phosphorus compound 5 is 5 to 10 mass %, the compressive strength S of the block 20 can be increased to 18 N / mm in many cases. ２ The higher the compressive strength S of the block 20, the better. There is no particular upper limit, but for example, 45 N / mm ２ etc.

[0032] The recycled phosphorus compound 5 preferably contains, for example, citric acid-soluble phosphorus in terms of solubility. Furthermore, the recycled phosphorus compound 5 preferably has a granular shape of about 5 mm or less. By using a recycled phosphorus compound 5 having these properties, a desirable block 20 can be manufactured in terms of solubility and ease of manufacture.

[0033] The phosphorus content of the blocks 20 may be, but is not limited to, 5 to 10 mass % relative to the cement, which is the main material. When the phosphorus content of the blocks 20 is within this range, nutrients can be appropriately and reliably supplied to the area where the blocks 20 are installed.

[0034] In the recycled phosphorus compound content setting process 330, staff at the block manufacturing facility 100 sets the content P of recycled phosphorus compound 5 within the upper limit value range of the content P of recycled phosphorus compound 5 determined in the recycled phosphorus compound content upper limit confirmation process 320, depending on the application (whether the emphasis is on the amount of nutrient salt leaching or on compressive strength).

[0035] 5 is a flow diagram illustrating an example of the flow of the block manufacturing process 400. In this process, a block 20 is manufactured according to the content P of the recycled phosphorus compound 5 set in the recycled phosphorus compound content setting process 330. In the first block material mixing process 410, measured amounts of cement, aggregate, and recycled phosphorus compound 5 are placed in a mixer and kneaded together with water and, if necessary, pigments.

[0036] In the block molding process 420, the kneaded material is supplied from the mixer to a molding machine. The material supplied to the molding machine is poured into molds in fixed amounts and compacted and molded using vibration and pressure. At this stage, the block 20 has not yet completely solidified, so the block 20 is further hardened by applying heat in the next block curing process 430. In the final block processing process 440, the block 20 is cut into a predetermined shape, completing the block 20. The size and shape of the block 20 can be set as desired. For example, the block 20 can be formed into a variety of shapes, such as the size and shape of a pebble, the size and shape of a wave-dissipating block, or the size and shape of a telephone pole.

[0037] Through these processes, recycled phosphorus compounds 5 recovered at resource recycling facilities 10, such as sewage sludge treatment plants, can be effectively utilized to produce blocks 20 that can supply phosphate fertilizer components to target marine areas over the long term. Utilizing these blocks 20 is expected to promote the cyclical use of phosphorus, a valuable resource, while also promoting the development of marine ecosystems such as seaweed beds and increasing the amount of carbon dioxide absorbed and stored by blue carbon, ultimately contributing to decarbonization.

[0038] <Nutrient Salt Slow-Release Block> The block 20 according to this embodiment is suitably manufactured by the manufacturing method described above. As described above, the block 20 contains a concrete block composition including a concrete raw material and a phosphorus compound. The phosphorus compound is preferably recycled phosphorus compound 5 recovered in a resource recycling process. The block 20 is manufactured by adjusting the content P of the phosphorus compound (recycled phosphorus compound 5) in the concrete block so that the compressive strength S of the concrete block is 18 N / mm ２ The block 20 is adjusted to have a compressive strength S of 18 N / mm or more. Therefore, the block 20 is excellent in terms of versatility and performance. The content P of the phosphorus compound (regenerated phosphorus compound 5) in the block 20 can be, for example, 5 to 10 mass %, but is not limited to this range. ２If the content P of the phosphorus compound (regenerated phosphorus compound 5) is more than 10 mass %, the block 20 can contain the phosphorus compound (regenerated phosphorus compound 5) in an amount of 5 to 10 mass %. In many cases, the compressive strength S of the block 20 can be increased to 18 N / mm ２ or more, for example, 18 to 45 N / mm ２ The phosphorus content of the block 20 is preferably, for example, 5 to 10% by mass relative to the cement, which is the main material. When the phosphorus content of the block 20 is within this range, nutrients can be appropriately and reliably supplied to the area in which the block 20 is installed. The phosphorus compound (recycled phosphorus compound 5) in the block 20 is preferably MAP, which can be obtained at the resource recycling facility 10. In this way, phosphorus recycled from waste is utilized, which not only contributes to resource circulation but also alleviates competition for the use of valuable phosphorus resources. The size and shape of the block 20 can be set as desired, as described above.

[0039] Block 20 effectively utilizes recycled phosphorus compounds 5 recovered at resource recycling facilities 10, such as sewage sludge treatment plants, and can supply phosphate fertilizer components to the target sea area over the long term. Utilizing Block 20 is expected to promote the cyclical use of phosphorus, a valuable resource, while also promoting the development of marine ecosystems such as seaweed beds and increasing the amount of carbon dioxide absorbed and stored by blue carbon, thereby contributing to decarbonization.

[0040] As described above, the present manufacturing method and block 20 utilize renewable resources and can provide pinpoint supply of nutrients to areas where they are needed over a long period of time. The manufacturing method for a nutrient release block and the nutrient release block according to the present invention have been described in detail using embodiments. However, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those that include all of the described components. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0041] 5 Recycled phosphorus compound 10 Resource recycling facility 20 Block 100 Block manufacturing facility 200 Block material adjustment process 210 Block material delivery process 220 Block material particle size adjustment process 230 Block material measurement process 300 Recycled phosphorus compound content adjustment process 310 Recycled phosphorus compound moisture content confirmation process 320 Recycled phosphorus compound content upper limit confirmation process 330 Recycled phosphorus compound content setting process 400 Block manufacturing process 410 Block material mixing process 420 Block molding process 430 Block curing process 440 Block processing process

Claims

1. A method for manufacturing a concrete block capable of sustained release of nutrients, comprising: incorporating a concrete raw material and a recycled phosphorus compound recovered through a resource recycling process as a composition of the concrete block; and adjusting the content of the recycled phosphorus compound in the concrete block so that the compressive strength of the concrete block is 18 N / mm ２ A method for producing a nutrient salt sustained release block, comprising the step of adjusting the block to the above.

2. The method for producing a nutrient salt sustained release block according to claim 1, wherein the regenerated phosphorus compound is magnesium ammonium phosphate.

3. A method for manufacturing a nutrient salt slow-release block according to claim 1, characterized in that the content of the regenerated phosphorus compound in the concrete block is 5 to 10 mass %.

4. A concrete block capable of gradually releasing nutrients, the composition of the concrete block containing a concrete raw material and a phosphorus compound, and the content of the phosphorus compound in the concrete block is adjusted so that the compressive strength of the concrete block is 18 N / mm ２ The nutrient salt sustained release block is characterized by being adjusted to the above.

5. The nutrient salt slow-release block according to claim 4, wherein the phosphorus compound is a recycled phosphorus compound recovered in a resource recycling process.

6. The nutrient salt slow-release block according to claim 4, wherein the phosphorus compound is magnesium ammonium phosphate.

7. A nutrient salt slow-release block according to claim 4, characterized in that the content of the phosphorus compound in the concrete block is 5 to 10 mass %.

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