Method for fixing carbon dioxide in controlled landfill site

Abstract

To provide a method for fixing carbon dioxide in a controlled landfill site, which efficiently reduces carbon dioxide in the atmosphere toward carbon neutrality, and simultaneously facilitates early stabilization of the controlled landfill so that the leachate meets discharge standards toward decommissioning.SOLUTION: In a method for fixing carbon dioxide, for example, target waste W in a moist state is landfilled in a land area 3 of a controlled landfill site 1 on the sea, and is cured for a predetermined period, ensuring that carbon dioxide is fixed in the target waste W and the target waste W is neutralized. This enables carbon dioxide in the atmosphere to be efficiently reduced toward carbon neutrality, and simultaneously allows the controlled landfill site 1 to be stabilized so that the leachate meets discharge standards toward decommissioning.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for fixing carbon dioxide in a controlled landfill site, which fixes carbon dioxide in waste buried in the controlled landfill site and neutralizes the waste. [Background technology]

[0002] As a long-standing concern about global warming, it is necessary to reduce carbon dioxide in the atmosphere in order to achieve carbon neutrality. Meanwhile, municipal and industrial waste such as incineration ash, coal ash, and other waste are landfilled in managed landfill sites on land or at sea. For example, a managed sea surface disposal site is a facility constructed in an area of ​​sea where municipal and industrial waste are reclaimed. In the early stages of landfilling, the inside of a managed sea surface disposal site is filled with seawater (referred to as retained water), but when landfilling is completed, it is filled with waste and is eventually covered with soil to become land. As landfilling progresses, the pH value of the retained water in a managed sea surface disposal site becomes more alkaline due to the waste, and in many cases, when landfilling is completed, the pH value of the pore water in the reclaimed land is alkaline, at 9.0 or more.

[0003] The reclaimed land of a managed sea surface disposal site is managed to maintain a constant water level (managed water level), and by law, in order to abolish a managed sea surface disposal site, when excess leachate generated by rainfall or other factors within the site is discharged into the open sea, the pH value of the excess leachate must be between 5.0 and 9.0. In short, there are many types of waste that are brought to a managed sea surface disposal site and buried, and some of these waste items contain hydroxide ions (OH) in the reclaimed land and retained water of the managed sea surface disposal site at the time of landfill. - ) and is highly alkaline due to its origin from waste materials.

[0004] These managed marine landfill sites are important infrastructure in the waste resource circulation field, especially in port areas in metropolitan areas, and are ideally located for industry and logistics, so it is hoped that the sites will be able to be used as soon as possible after landfilling is completed. However, early decommissioning is currently not possible due to reasons such as the fact that leachate from landfill waste does not meet effluent standards. For this reason, landfill site operators in various regions have been taking measures based on various considerations, but the problem has not yet been resolved. Therefore, it is necessary to take measures that will lead to early stabilization and early decommissioning from the landfill process onwards.

[0005] Therefore, as a conventional technology proposed to solve the above-mentioned problems, Patent Document 1 describes a method for stabilizing an existing managed waste disposal site, in which an air supply pipe is buried so that the exhaust outlet is located near the lower limit of the retained water level in the waste pile where waste is piled up, and neutralizing gas containing carbon dioxide is supplied from the air supply pipe. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-166504 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the stabilization method for an existing managed waste disposal site described in Patent Document 1, the neutralizing gas from the exhaust port of the air intake pipe dissolves in the interstitial water located in a very close range around the exhaust port of the air intake pipe, and can only neutralize with the alkaline components in the interstitial water. In addition, the water with carbon dioxide dissolved in it does not basically flow and remains in that position, so the purification range is an extremely narrow range around the exhaust port, and the purification efficiency does not increase. Therefore, in order to expand the purification range, it is necessary to provide multiple air intake pipes and repeat the installation and removal work of each air intake pipe many times, but this construction is not efficient, especially in terms of construction period, construction cost, etc. In the stabilization method for an existing managed waste disposal site described in Patent Document 1, it is difficult to efficiently reduce carbon dioxide in the atmosphere toward carbon neutrality and stabilize the leachate so that it meets the discharge standard toward the abolition of the managed sea surface disposal site.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a method for fixing carbon dioxide at a managed landfill, which can efficiently reduce carbon dioxide in the atmosphere toward carbon neutrality, while also stabilizing the leachate so that it meets the effluent standards in preparation for the abolition of the managed landfill. [Means for solving the problem]

[0009] As a means for solving the above problems, the invention of claim 1 is characterized in that wet waste is buried in a controlled disposal site and cured for a specified period of time, thereby fixing carbon dioxide in the waste and neutralizing the waste. In the invention of claim 1, when the waste is in a wet state, for example, the water content is 5% or more, the waste is buried as it is in a controlled disposal site (including the form of banking) and cured for a predetermined period of time, whereby carbon dioxide in the atmosphere is attached and fixed on the particle surface of the waste as calcium carbonate derived from calcium contained in the waste, and the waste can be neutralized. As a result, carbon dioxide in the atmosphere can be reduced, and the hydroxide ions (OH -) and as a result, alkalization in the controlled sea surface disposal site can be suppressed. In the following description, "filling" on land of the controlled disposal site includes "banking".

[0010] In other words, by burying wet waste and curing it for a certain period of time, CO 2 (in the atmosphere)+H 2 O (water content) → 2H + +CO 3 2- , and CaO (waste) + H 2 O (water content)→Ca 2+ +2OH - While reacting with, on land, 2 hours + +2OH - →2H 2 It reacts with O to form Ca 2+ +CO 3 2- →CaCO 3 The calcium carbonate (CaCO 3 ) adheres to the surface of the waste particles while the waste is neutralized. As a result, carbon dioxide in the atmosphere can be reduced, and hydroxide ions (OH - ) and stabilize the leachate in preparation for the decommissioning of managed landfill sites.

[0011] Even if the waste has an appropriate moisture content, when the waste is buried outdoors, evaporation occurs due to the influence of the surrounding environment such as sunlight, wind, temperature, and humidity, and the moisture content decreases, while the moisture content may increase due to rainfall, etc. In order to efficiently perform a carbonation coating on the waste particles, it is important to contact the waste with a large amount of carbon dioxide while maintaining a predetermined moisture content. Therefore, for example, the waste in a wet state, i.e., with a predetermined moisture content, is transported indoors and buried indoors, making it possible to maintain the predetermined moisture content. In this case, carbon dioxide, which is an exhaust gas from many facilities, can be introduced indoors or many facilities can be arranged indoors, thereby filling the indoors with carbon dioxide at a higher concentration than that in the atmosphere, and as a result, it is possible to promote the fixation of carbon dioxide in the waste (reduction of carbon dioxide in the atmosphere) and the neutralization of the waste.

[0012] The invention of claim 2 is characterized in that wet waste is buried in a controlled disposal site as a thin layer of soil of 20 cm or less and cured for a specified period of time, thereby fixing carbon dioxide in the waste and neutralizing the waste. In the invention of claim 2, when wet waste is buried, it is expanded so that the contact area between the waste and the atmosphere is larger, and the waste is buried as a thin embankment layer with a thickness of 20 cm or less, preferably 10 cm ± 5 cm. This enables carbon dioxide in the atmosphere to penetrate sufficiently to the waste at the bottom of the embankment, facilitating the fixation of carbon dioxide in the waste (reduction of carbon dioxide in the atmosphere) and the neutralization of the waste.

[0013] The invention of claim 3 is characterized in that wet waste is buried in a controlled disposal site as a coarse, breathable fill layer without compaction, and left to cure for a prescribed period of time, thereby fixing carbon dioxide in the waste and neutralizing the waste. In the invention of claim 3, when wet waste is buried, the waste is buried as a coarse, breathable soil layer, which allows carbon dioxide from the atmosphere to penetrate sufficiently into the gaps at the bottom of the soil layer, thereby facilitating the fixation of carbon dioxide in the waste (reduction of carbon dioxide in the atmosphere) and the neutralization of the waste.

[0014] The invention of claim 4 is characterized in that waste landfilled in a controlled disposal site is treated with water spraying and then cured for a specified period of time, thereby fixing carbon dioxide in the waste and neutralizing the waste. In the invention of claim 4, by performing a water sprinkling treatment on waste buried in a managed landfill site, it is possible to make the waste wet, i.e., have a desired moisture content, and as a result, it is possible to promote the fixation of carbon dioxide in the waste (reduction of carbon dioxide in the atmosphere) and the neutralization treatment of the waste. In addition, for example, the water retained in a managed sea surface disposal site is alkalized, and it has been confirmed that carbon dioxide dissolves more easily in this alkaline water than in general seawater. Then, for example, when performing a water sprinkling treatment on waste buried on land in a managed sea surface disposal site, the amount of carbon dioxide supplied to the waste is increased by sprinkling the retained water in which carbon dioxide has been dissolved, and as a result, it is possible to promote the neutralization treatment of the waste.

[0015] The invention of claim 5 is characterized in that in the invention of any one of claims 1 to 4, an uneven portion is formed on the surface of the fill layer of the waste buried in the controlled disposal site. In the invention of claim 5, by forming unevenness on the entire surface of the embankment layer of waste buried in a controlled disposal site, it is possible to increase the contact area between the atmosphere and the waste. As a result, it is possible to promote the fixation of carbon dioxide in the waste (reduction of carbon dioxide in the atmosphere) and the neutralization of the waste.

[0016] The invention of claim 6 is the invention according to any one of claims 1 to 4, characterized in that the soil layer of the waste buried in a controlled disposal site is agitated. In the invention of claim 6, even if the thickness of the waste embankment is thick and there is some distribution of moisture content in the vertical direction within the embankment, or even if carbon dioxide does not reach the bottom of the waste embankment, the moisture content of the waste embankment can be leveled in the vertical direction by stirring the waste upside down, and calcium that has migrated to the bottom of the embankment together with moisture and dissolved therein can be moved to the surface and its reaction with carbon dioxide can be promoted. As a result, the fixation of carbon dioxide in the waste (reduction of carbon dioxide in the atmosphere) and the neutralization of the waste can be promoted.

[0017] The invention of claim 7 is the invention according to any one of claims 1 to 4, characterized in that the waste buried in a controlled disposal site is cured for 1 to 10 days. In the invention of claim 7, which is related to the moisture content of the waste and the thickness of the waste embankment layer, by burying the waste and curing it for 1 to 10 days, the amount of carbon dioxide fixed in the atmosphere in the waste embankment layer becomes saturated, and the next landfill of waste can be carried out quickly. This allows the main work of landfilling the waste to be carried out without delay. In short, by setting the curing period with precision, it is possible to suppress a decrease in the efficiency of landfill work.

[0018] The invention of claim 8 is the invention according to any one of claims 1 to 4, characterized in that a plurality of embankment layers after carbon dioxide has been fixed in the waste are stacked in a controlled disposal site. According to the invention of claim 8, the onshore portion of a managed sea surface disposal site and the space of a managed land disposal site can be effectively utilized.

[0019] The invention of claim 9 is characterized in that, in the invention described in any one of claims 1 to 4, in a controlled disposal site, the fill layer after carbon dioxide has been fixed in the waste is compacted to increase its density. In the invention of claim 9, the embankment layer after carbon dioxide has been fixed in the waste is compacted to increase its density, thereby reducing the volume of the embankment layer, thereby increasing the amount of waste to be landfilled and improving the strength of the ground.

[0020] The invention of claim 10 is characterized in that, in the invention described in any one of claims 1 to 4, the controlled disposal site is a controlled marine disposal site, and after carbon dioxide is fixed in the waste buried on land, the waste is dumped into the retained water of the controlled marine disposal site and buried. In the invention of claim 10, after carbon dioxide is fixed in the waste buried on land in the managed sea surface disposal site, in other words, after calcium carbonate and the like adhere to the surface of the waste particles buried on land, the waste is dumped into the water held in the managed sea surface disposal site and buried there, which suppresses the elution of alkaline components from the waste in the held water and suppresses alkalization in the managed sea surface disposal site. This makes it possible to reduce carbon dioxide in the atmosphere and stabilize the leachate in preparation for the abolition of the managed sea surface disposal site.

[0021] The invention of claim 11 is characterized in that in the invention according to any one of claims 1 to 4, the waste material is selected based on its pH value. In the invention of claim 11, waste that can easily fix carbon dioxide is selected by measuring the pH value in advance. In other words, a wide variety of waste is brought in and buried in a controlled disposal site every day. However, only a portion of the waste alkalizes the interstitial water and retained water in the landfill ground of a controlled disposal site. In such a case, it would be costly and time-consuming to carry out treatment work to fix carbon dioxide in the landfill work for all types of waste, which is not desirable in terms of cost-effectiveness.

[0022] For this purpose, a portion of the waste dumped at a controlled disposal site (on land in a controlled offshore disposal site) is sampled and the pH value is measured. This pH measurement allows waste with a high pH value, for example a pH value of 12.0 or higher, to be evaluated as waste that can alkalize the controlled disposal site and easily fix carbon dioxide. By carrying out such advance pH measurement tests, it is possible to select waste that can easily fix carbon dioxide, and to efficiently fix carbon dioxide in the waste (reducing carbon dioxide in the atmosphere) and promote the neutralization of the waste in a limited onshore area. Effect of the Invention

[0023] The method of fixing carbon dioxide at a controlled landfill site according to the present invention can efficiently reduce carbon dioxide in the atmosphere toward carbon neutrality, and can also stabilize leachate so that it meets effluent standards in preparation for the closure of the controlled landfill site. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic perspective view showing the overall structure of a managed marine disposal site. [Diagram 2] FIG. 2 is a perspective view showing the target waste that has been dumped and dumped on land at a controlled sea surface disposal site being spread out and leveled by heavy machinery. [Diagram 3] Figure 3 is a plan view of the surface of the fill layer reclaimed on the land portion of the controlled marine disposal site. [Figure 4] FIG. 4 is a perspective view of a mesh cylinder for forming an uneven portion on the surface of an embankment layer reclaimed on the land portion of a controlled sea surface disposal site. [Diagram 5] Figure 5 is a perspective view showing a state in which a mesh plate material is attached to the back of a backhoe's skeleton in order to form an uneven (grooved) portion on the surface of an embankment layer that has been reclaimed on the land portion of a controlled sea surface disposal site. [Figure 6]Figure 6 is a perspective view showing how the target waste (which has undergone carbon dioxide fixation treatment) that has been buried as multiple layers of embankment on the land portion of the managed marine landfill site is dumped into the underwater portion (retained water) of the managed marine landfill site and buried. [Figure 7] FIG. 7 is a schematic diagram showing how carbon dioxide fixation treatment (using a pump) is carried out on target waste placed in an indoor space. [Figure 8] FIG. 8 is a schematic diagram showing how carbon dioxide fixation treatment (using a cylinder) is carried out on target waste placed in an indoor space. [Figure 9] FIG. 9 is a perspective view showing the state in which watering (using sprinklers) is being carried out on the target waste buried on land in a controlled sea surface disposal site. [Figure 10] FIG. 10 is a perspective view showing the state in which water sprinkling treatment (using a mist device) is being carried out on the target waste buried on land in a controlled sea surface disposal site. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, an embodiment of the present invention will be described in detail with reference to Figs. With reference to FIG. 1, for example, a managed sea surface disposal site 1 is installed adjacent to the open sea as a managed disposal site, with seawater surrounded by a water-impermeable revetment (a sloping embankment 2 in FIG. 1) and the like as the retained water. In addition, during the reclamation process, the managed sea surface disposal site 1 has an underwater part 4 in which seawater surrounded by a water-impermeable revetment and the like is the retained water, and a part of the land part 3 that is reclaimed with waste W. The waste W includes various types of waste, such as general waste and industrial waste (cinders, sludge, slag, coal ash, dust, construction waste soil, etc.). Among these, incineration ash (bottom ash and fly ash) burned at a general waste incineration plant, and industrial waste slag (slag from steelworks) and coal ash (by-products from power plants) have a high potential to increase the pH value of the retained water and the reclaimed land. The managed offshore disposal site 1 will eventually be completed when waste W is piled up in the underwater part 4 (retaining water) of the managed offshore disposal site 1, rising above the controlled water level, and then covered with soil on top of that in the land part 3, where it will exceed the controlled water level.

[0026] Referring to FIG. 2, a large amount of waste W is dumped and buried on the land part 3 of the managed sea surface disposal site 1. At this time, waste W that can easily fix carbon dioxide is selected from the various types of waste W by a simple test that measures the pH value. In the simple test, a part of the waste W dumped (buried) on the land part 3 of the managed sea surface disposal site 1 is collected, placed in a container of a certain volume, and shaken for a certain time (for example, 1 minute or 3 minutes) with a solvent (preferably seawater in this case, but tap water or pure water is also acceptable) in a certain ratio (for example, 100 g of solvent for 10 g of waste), and the pH value of the overlying water is measured after leaving it to stand until the waste W settles. Based on this preliminary simple test, the carbon dioxide fixation treatment described later is performed only on waste W with a high pH value, i.e., a pH value of 12.0 or more (hereinafter referred to as target waste W).

[0027] Then, the waste selected as the target waste W is subjected to carbon dioxide fixation treatment. As a method for carbon dioxide fixation treatment of the target waste W, first, the water content of the target waste W is measured. Since the method for measuring the water content is well known, detailed description will be omitted here. As a result, referring to FIG. 2, if the target waste W is in a wet state, for example, the water content is 5% or more, the target waste W is buried as it is in the land part 3 of the managed sea surface disposal site 1 and cured for a predetermined period. The curing period is appropriately set based on various factors related to carbon dioxide fixation, such as the water content of the target waste W, the layer thickness T of the embankment layer 10 described later, the surrounding environment (indoor space 19 or outdoors, etc. described later), the carbon dioxide concentration based on the surrounding environment (indoor space 19 or outdoors, etc. described later), the type and properties (pH value, etc.) of the target waste W, and is, for example, one day, three days, or about one week (within 10 days).

[0028] In this way, by curing the wet target waste W for a certain period of time, CO 2 (in the atmosphere)+H 2 O (water content) → 2H + +CO 3 2- , and CaO (target waste W) + H 2 O (water content)→Ca 2+ +2OH - While reacting with, on land, 2 hours + +2OH - →2H 2 Neutralization reaction as O, Ca 2+ +CO 3 2- →CaCO 3 It reacts with calcium carbonate (CaCO 3 ) adheres to the particle surfaces of the target waste W, while the target waste W is neutralized. The standard for the curing period is the time when the amount of carbon dioxide in the atmosphere fixed in the embankment layer 10 of the target waste W reaches a saturated state.

[0029] Therefore, referring to FIG. 2, when the wet target waste W is to be buried in the managed sea surface disposal site 1, the target waste W dumped and thrown onto the land portion 3 is spread out so as to be flat and leveled by heavy machinery such as a backhoe, a wheel loader, a motor grader, etc., so that the contact area between the target waste W and the atmosphere is increased. At that time, the target waste W is buried as a thin layer of embankment layer 10 having a layer thickness T of 20 cm or less, preferably about 10 cm ± 5 cm. In addition, when the target waste W is buried, the embankment immediately after the burial is not compacted by heavy machinery such as a roller, but is buried as a coarse embankment layer 10 that is breathable in its natural state. In other words, when the target waste W is buried, there is no need to increase the density by compaction, etc., and the target waste W is buried as a loose embankment layer 10 with many gaps inside so that the air permeability coefficient is as high as possible.

[0030] In this way, referring to FIG. 3, the embankment layer 10 of the target waste W has a large number of linear grooves 12, 12 formed at intervals on its surface (including groove cutting), or the grooves 12, 12 are formed in a lattice shape, thereby forming an uneven portion 13 over the entire surface of the embankment layer 10. The uneven portion 13 is formed deeper and the width between the opposing walls (concave and convex portions) is smaller so that the contact area between the surface of the embankment layer 10 and the atmosphere is increased. Referring to FIG. 4, the uneven portion 13 can be formed by rolling a net cylinder 16, which is made by rolling a net plate material having a lattice shape with a plurality of openings into a substantially circular shape, on the surface of the embankment layer 10. Also, referring to FIG. 5, the uneven portion 13 can be formed by attaching a net plate material having a lattice shape with a plurality of openings to the back side (the back side of the concave portion) of the skeleton 6 of the backhoe, and driving the net plate material 17 into the surface of the embankment layer 10.

[0031] After that, when a predetermined curing period, for example, a 7-day curing period, is completed, the carbon dioxide in the atmosphere is attached to and fixed on the particle surface of the target waste W in the entire first embankment layer 10 as calcium carbonate, i.e., when the amount of fixed carbon dioxide in the atmosphere in the target waste W in the entire first embankment layer 10 reaches a saturated state, the first embankment layer 10 is rolled with a heavy machine such as a roller cart. As a result, the first embankment layer 10 becomes hard and dense. Next, when the rolling work on the first embankment layer 10 is completed, the wet target waste W is spread on the first embankment layer 10 as the second embankment layer 10 as described above, and after curing for a predetermined period, it is rolled on the second embankment layer 10. This work is repeated, and multiple embankments 10, 10 filled with the target waste W in which the carbon dioxide in the atmosphere has been fixed are stacked on the land portion 3, as shown in FIG. 6. Thereafter, when the curing period for the uppermost embankment layer 10 is completed, the target waste W of the multiple embankments 10, 10 that have been subjected to the carbon dioxide fixation treatment on the land portion 3 is dumped into the underwater portion 4 (retained water) of the managed marine disposal site 1 and landfilled. If there is sufficient space on the land portion 3, the multiple embankments 10, 10 that have been subjected to the carbon dioxide fixation treatment may be left as is.

[0032] In the above-mentioned embodiment, the target waste W in a wet state is buried in the land part 3 (outdoors) of the managed sea surface disposal site 1, and carbon dioxide in the atmosphere is fixed in the target waste W, and the target waste W is also neutralized. However, referring to FIG. 7, the target waste W may be carried into an indoor space 19, and similarly to the outdoor operation, the target waste W is spread out so that the contact area between the target waste W and the atmosphere is larger and the layer thickness is set to a predetermined thickness T, and after a predetermined period of curing, the carbon dioxide fixation treatment work of rolling is repeated, and a plurality of embankment layers 10, 10 of the target waste W in which carbon dioxide has been fixed may be stacked in the indoor space 19. After that, the target waste W in the plurality of embankment layers 10, 10 in which carbon dioxide fixation treatment has been performed in the indoor space 19 is dumped into the underwater part 4 (retained water) of the managed sea surface disposal site 1 and buried, similarly to the outdoor operation. The indoor space 19 may be formed by providing, for example, a large tent or a building (simple prefabricated building, etc.) on the land part 3.

[0033] In addition, by opening a part of the indoor space 19, the air may be allowed to flow into the indoor space 19. Also, a ventilation fan (not shown) may be installed to actively allow the air to flow into the indoor space 19. Furthermore, referring to FIG. 7, exhaust gas containing carbon dioxide discharged from equipment 20 such as various heavy machinery such as backphones and generators used in landfill work may be pumped into the indoor space 19 by a pump 21. Also, referring to FIG. 8, the carbon dioxide discharged from the equipment 20 may be supplied to the indoor space 19 by a gas cylinder 24 that collects the carbon dioxide. Furthermore, although not shown, the equipment 20 such as various heavy machinery and generators may be arranged in the indoor space 19, and the indoor space 19 may be filled with exhaust gas from the equipment 20 such as various heavy machinery and generators, thereby supplying the indoor space 19 with carbon dioxide at a higher concentration than that in the atmosphere. This allows the indoor space 19 to be filled with carbon dioxide at a higher concentration than that in the atmosphere, and as a result, the neutralization treatment of the target waste W can be promoted. Furthermore, it is possible to reduce the amount of carbon dioxide emitted into the atmosphere from the facility 20, thereby contributing to carbon neutrality.

[0034] The optimal values ​​for the various settings related to the carbon dioxide fixation treatment described above, i.e., the moisture content (lower limit) of the target waste W in a wet state, the layer thickness T, and the curing period, etc., are determined based on their mutual relationships, the surrounding environment (indoor space 19 or outdoors, etc.), the carbon dioxide concentration based on the surrounding environment (indoor space 19 or outdoors, etc.), the type and properties (pH value, etc.) of the target waste W, etc., while minimizing energy consumption (amount of carbon dioxide released) and efficiently fixing carbon dioxide in the target waste W, and neutralizing the target waste W, while being appropriately verified.

[0035] In this embodiment, when the target waste W in a wet state is buried outdoors or indoors (indoor space 19) in the land portion 3 of the managed sea surface disposal site 1, if the thickness T of the embankment layer 10 becomes thicker than 20 cm due to circumstances, it is preferable to mix the embankment layer 10 by turning it upside down at an appropriate timing during the curing period. Even if the thickness T of the embankment layer 10 is 20 cm or less, it may be mixed by turning it upside down.

[0036] In addition, when the target waste W to be buried in the managed sea surface disposal site 1 is dry with a water content of less than 5%, or when the water content of the target waste W is 5% or more but is to be increased in consideration of the surrounding environment such as sunlight, wind, temperature, and humidity, the target waste W may be subjected to water sprinkling treatment. The water sprinkling treatment may be performed outdoors or indoors. For example, when the water sprinkling treatment is performed outdoors, a sprinkler, for example, is installed as the water sprinkling equipment 22 on the land part 3 of the managed sea surface disposal site 1 with reference to FIG. 9. Around the water sprinkling equipment 22 (at the water sprinkling location), a steel plate 23 is laid as a water impermeable material. The target waste W is piled on the steel plate 23 with an appropriate layer thickness. Then, the target waste W piled on the steel plate 23 is water sprinkled by the water sprinkling equipment 22. In this way, by laying an impermeable material such as the steel plate 23 in advance, it is possible to prevent the sprinkled water from seeping into the landfill ground of the land portion 3, and to minimize the energy consumption (emission of carbon dioxide) of the sprinkling pump etc. on the target waste W. Referring to Fig. 10, a mist device may be installed as the sprinkling equipment 22 on the land portion 3 of the managed sea surface disposal site 1 to sprinkle water on the target waste W piled up on the steel plate 23. Naturally, the sprinkling treatment may be performed without using the steel plate 23.

[0037] In this embodiment, the water to be sprinkled is the retained water in the underwater section 4 of the managed sea surface disposal site 1. Seawater, industrial water, or tap water may be used as the water to be sprinkled, but by sprinkling retained water in which carbon dioxide has been dissolved, the amount of carbon dioxide supplied to the waste W is increased, and as a result, the neutralization treatment of the waste W can be promoted. Then, after the target waste W reaches a desired water content by the sprinkling equipment 22, the target waste W is subjected to carbon dioxide fixation treatment in an outdoor or indoor space 19 as described above.

[0038] In the present embodiment described above, the target waste W in a wet state, for example with a water content of 5% or more, is buried in the land portion 3 of a controlled disposal site, for example a controlled sea surface disposal site 1, and cured for a predetermined period of time, whereby the target waste W can be neutralized while carbon dioxide in the atmosphere is attached to the particle surfaces of the target waste W as calcium carbonate (carbonate) derived from the calcium contained in the target waste W. Note that the metal that becomes the carbonate is mainly calcium, but not only calcium but also magnesium contained in the target waste W can become carbonates such as magnesium carbonate.

[0039] As a result, the target waste W can be neutralized while reducing carbon dioxide in the atmosphere, and the target waste W can be dumped into the underwater section 4 (retained water) of the managed sea surface disposal site 1. After the waste is landfilled, the hydroxide ions (OH - ) can be reduced, and as a result, alkalization of the managed sea surface disposal site 1 can be suppressed. This allows atmospheric carbon dioxide to be efficiently fixed in the target waste W as carbonate, contributing to carbon neutrality, and stabilizing the leachate so that it meets the discharge standards in preparation for the decommissioning of the managed sea surface disposal site 1.

[0040] In addition, in this embodiment, when the wet target waste W is buried, it is expanded so that the contact area between the target waste W and the atmosphere is larger, and it is buried as a thin embankment layer 10 with a layer thickness T of 20 cm or less, preferably 10 cm ± 5 cm, which makes it possible for carbon dioxide in the atmosphere to sufficiently penetrate to the target waste W at the bottom of the embankment layer 10, thereby facilitating the fixation of carbon dioxide in the target waste W (reduction of carbon dioxide in the atmosphere) and the neutralization process of the target waste W.

[0041] Furthermore, in this embodiment, when the wet target waste W is buried, the target waste W is buried as a coarse, breathable embankment layer 10, which allows carbon dioxide in the atmosphere to penetrate sufficiently into the gaps at the bottom of the embankment layer 10 of the target waste W, thereby facilitating the fixation of carbon dioxide in the target waste W (reduction of carbon dioxide in the atmosphere) and the neutralization process of the target waste W.

[0042] Furthermore, in this embodiment, the target waste W buried on the land portion 3 of the managed marine disposal site 1 can be subjected to a water sprinkling treatment to make the target waste W moist, i.e., to have a desired moisture content, thereby promoting the fixation of carbon dioxide in the target waste W (reduction of carbon dioxide in the atmosphere) and the neutralization treatment of the target waste W.

[0043] Furthermore, in this embodiment, by forming an uneven portion 13 on the entire surface of the embankment layer 10 of the target waste W buried in the controlled disposal site, it is possible to increase the contact area between the atmosphere and the target waste W. As a result, it is possible to promote fixation of carbon dioxide in the target waste W (reduction of carbon dioxide in the atmosphere) and neutralization treatment of the target waste W.

[0044] Furthermore, in this embodiment, particularly when the layer thickness T of the embankment layer 10 of the target waste W is thick, for example, when the layer thickness T is thicker than 20 cm, the water content of the embankment layer 10 of the target waste W can be leveled in the vertical direction by stirring the target waste W upside down at appropriate times during the curing period, and calcium that has migrated to the bottom of the embankment layer 10 together with the water and dissolved therein can be moved to the surface layer, accelerating the reaction with carbon dioxide. As a result, the fixation of carbon dioxide in the target waste W (reduction of carbon dioxide in the atmosphere) and the neutralization treatment of the target waste W can be promoted.

[0045] Furthermore, in this embodiment, a plurality of embankment layers 10, 10 in which carbon dioxide is fixed to the target waste W are stacked on the land portion 3 of the managed sea surface disposal site 1. This allows the land portion 3 of the managed sea surface disposal site 1 to be effectively utilized.

[0046] Furthermore, in this embodiment, the embankment layer 10 in which carbon dioxide is fixed in the target waste W is compacted to increase its density, thereby reducing the volume of the embankment layer 10. As a result, the amount of the target waste W that is landfilled can be increased, and the strength of the landfill ground can be improved.

[0047] Furthermore, in this embodiment, after carbon dioxide is fixed in the waste buried in the land portion 3 of the managed sea surface disposal site 1, the target waste W is dumped into the underwater portion 4 (retained water) of the managed sea surface disposal site 1 and buried there, which suppresses the elution of alkaline components from the waste in the retained water and suppresses alkalization within the managed sea surface disposal site 1. This makes it possible to reduce carbon dioxide in the atmosphere and stabilize the leachate in preparation for the closure of the managed sea surface disposal site 1.

[0048] Furthermore, in this embodiment, the pH value of some of the waste W buried on the land portion 3 of the managed sea surface disposal site 1 is measured in advance, and the waste W that affects the alkalinization of the managed sea surface disposal site 1 and can easily fix carbon dioxide, that is, the waste W with a pH value of 12.0 or more, is selected for carbon dioxide fixation treatment. By carrying out such a simple test in advance (measurement of pH value), it is possible to efficiently fix carbon dioxide in the waste W (reduction of carbon dioxide in the atmosphere) and promote neutralization treatment of the waste W in the limited land portion 3.

[0049] In this embodiment, carbon dioxide is fixed and the target waste W is neutralized for the target waste W that is buried on the land portion 3 of the managed marine disposal site 1, but carbon dioxide can also be fixed and the waste W is neutralized for the waste W that is buried in a managed land-based disposal site. [Explanation of symbols]

[0050] 1 Managed sea surface disposal site (managed disposal site), 3 Land area, 4 Underwater area (retaining water), 10 Filling layer, 13 Uneven area, 22 Watering equipment, W Target waste (waste)

Claims

1. A method for fixing carbon dioxide at a controlled landfill site, comprising the steps of: filling wet waste material in the controlled landfill site and curing the waste material for a prescribed period of time, thereby fixing carbon dioxide in the waste material and neutralizing the waste material.

2. A method for fixing carbon dioxide at a controlled landfill site, comprising filling wet waste with a thin layer of soil of 20 cm or less at the controlled landfill site and curing the waste for a prescribed period of time, thereby fixing carbon dioxide in the waste and neutralizing the waste.

3. A method for fixing carbon dioxide at a controlled landfill site, comprising the steps of filling wet waste in a controlled landfill site as a coarse, breathable fill layer without compaction, and curing the waste for a prescribed period of time, thereby fixing carbon dioxide in the waste and neutralizing the waste.

4. A method for fixing carbon dioxide at a controlled landfill site, comprising the steps of: sprinkling water on waste disposed of at the controlled landfill site and curing the waste for a prescribed period of time, thereby fixing carbon dioxide in the waste and neutralizing the waste.

5. 5. The method for fixing carbon dioxide in a controlled landfill according to claim 1, further comprising forming an uneven portion on the surface of the fill layer of the waste buried in the controlled landfill.

6. 5. The method for fixing carbon dioxide in a controlled landfill according to claim 1, further comprising mixing the soil layer of the waste material buried in the controlled landfill.

7. 5. The method for fixing carbon dioxide in a controlled landfill site according to claim 1, wherein the waste buried in the controlled landfill site is cured for 1 to 10 days.

8. 5. The method for fixing carbon dioxide in a controlled landfill according to claim 1, further comprising stacking a plurality of embankment layers in the controlled landfill after the carbon dioxide has been fixed in the waste.

9. 5. The method for fixing carbon dioxide in a controlled landfill according to any one of claims 1 to 4, characterized in that in the controlled landfill, the fill layer after the carbon dioxide is fixed in the waste is compacted to increase its density.

10. 5. The method for fixing carbon dioxide at a controlled disposal site according to any one of claims 1 to 4, characterized in that the controlled disposal site is a controlled offshore disposal site, and after carbon dioxide is fixed in the waste buried on land, the waste is dumped into the retained water of the controlled offshore disposal site and buried therein.

11. 5. The method for fixing carbon dioxide in a controlled landfill site according to claim 1, wherein the waste is selected based on its pH value.

Images