A method for land reclamation by coal-based solid waste in cooperation with agricultural waste

Abstract

The application provides a method for land improvement by coal-based solid waste in cooperation with agricultural waste, and belongs to the technical field of solid waste recycling. The method provided by the application takes coal gangue and other solid waste as the main raw material, provides different application modes for land restoration in mining areas and land improvement in desertification, and is suitable for solving the problems of land desertification in mining areas and the ecological restoration demand of the mining areas. The method provides a feasible solution for the regions taking coal-based industry and animal husbandry as the pillar industries, achieves the ecological restoration effect of waste treatment and waste utilization, and is suitable for solving the problems of land desertification in mining areas and the ecological restoration demand of the mining areas. The results of the embodiments show that when the method is used for land improvement, the soil bulk density and the field moisture capacity can be effectively improved, the nutrient content in the soil is greatly improved, and the improved soil meets the standard of "soil environmental quality agricultural land soil pollution risk control standard (trial)" (GB15618-2018).

Description

Technical Field

[0001] This invention relates to the field of solid waste recycling technology, and in particular to a method for land improvement using coal-based solid waste in conjunction with agricultural waste. Background Technology

[0002] Coal, as a crucial traditional energy source, is consumed in large quantities annually, resulting in a significant amount of coal-based solid waste. Coal gangue, a major solid waste generated during coal mining and washing, occupies vast areas, poses a high risk of heavy metal leaching, and may spontaneously combust during weathering and oxidation, causing environmental pollution and contributing to desertification. This poses a significant challenge to the sustainable use of surrounding land resources. Simultaneously, agricultural production and livestock farming generate substantial amounts of organic waste, such as straw and livestock manure. The accumulation and improper disposal of this organic waste not only pollutes land resources but also leads to greenhouse gas emissions.

[0003] Furthermore, the improvement and ecological restoration of desertified land in mining areas requires a focus on improving soil structure and increasing nutrients, necessitating the use of soils with good water retention and fertility. In contrast, the ecological restoration of coal mining areas must ensure that the soil possesses a certain level of organic matter content and biological activity to promote plant growth and ecosystem recovery. However, traditional topsoil covering methods are labor-intensive in the ecological restoration of mining areas, resulting in slow progress in the improvement and ecological restoration of desertified land.

[0004] Coal gangue shares similarities with natural soil and has a relatively high organic content, making it a natural organic mineral resource. Therefore, extensive research has been conducted in China on the soil utilization of coal gangue. Directly covering soil with coal gangue achieves the goal of large-scale application and convenience, but its particle size is large, capillary porosity is low, and water retention is poor. Methods such as producing coal gangue compound fertilizers through chemical activation or microbial methods, and using coal gangue to make porous ecological restoration materials, have advantages such as high nutrient utilization, excellent water and fertilizer retention, and environmental friendliness; however, these methods are complex and costly.

[0005] Patent CN110999753A discloses an artificial ecological matrix based on coal gangue and its preparation method. It uses coal gangue and plant-derived organic matter as raw materials, and composts them by adding microbial agents to produce an environmentally friendly, safe, nutrient-rich ecological matrix suitable for plant growth. However, the above method has a low utilization rate of coal gangue and presents environmental problems such as odor and gas emissions. Patent CN118020599A discloses a coal gangue-based artificial soil, its preparation method, and its application. After crushing and screening the coal gangue, it is mixed and cultured with microbial strains and solvents to obtain activated coal gangue. This activated coal gangue is then mixed and cultured with activated fly ash to finally produce coal gangue-based artificial soil. Patent CN117281010A discloses a method for preparing artificial soil primarily composed of coal gangue. The method involves screening coal gangue and diatomaceous earth, crushing and mixing them, then heating and dehydrating them at 450-550℃, followed by rapid cooling with water to maintain moisture. The soil is then piled up for 15-30 days for natural maturation. Most of these methods add coal gangue as a soil conditioner, failing to achieve the goal of soil reconstruction. They also suffer from high costs, complex operations, complicated production processes, and environmental unfriendliness.

[0006] Therefore, how to achieve the synergistic resource utilization of coal-based solid waste and agricultural and forestry waste is of great significance for improving the ecological environment, enhancing soil quality, and promoting the circular economy. Summary of the Invention

[0007] The purpose of this invention is to provide a method for land improvement using coal-based solid waste and agricultural waste. The method provided by this invention uses solid waste such as coal gangue as the main raw material for land improvement, and adopts different improvement methods for different land conditions. It can significantly improve the quality of the land and can be used for land restoration.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for land improvement using coal-based solid waste in conjunction with agricultural waste, comprising: When the land improvement is for mining area land remediation, the land improvement method includes: mixing coal gangue, construction waste and organic fertilizer to obtain activated artificial soil, and then using the activated artificial soil for mining area land remediation; When the land improvement is for desertified land improvement, the land improvement method includes: mixing a sandy soil conditioner and sandy soil to obtain improved soil, and then using the improved soil for desertified land improvement; the sandy soil conditioner includes coal gangue and porous materials.

[0009] Preferably, the activated artificial soil comprises 30-80% coal gangue, 15-20% construction waste, and ≤10% organic fertilizer, based on a mass percentage of 100%.

[0010] Preferably, when the land improvement is for mining area land remediation, the coal gangue includes small coal gangue particles of 0.5-1mm, medium coal gangue particles of 1-2mm, and large coal gangue particles of >2mm.

[0011] Preferably, based on the mass of coal gangue as 100%, the proportion of small-particle coal gangue is 40-80%; the proportion of medium-particle coal gangue is ≤30%; and the proportion of large-particle coal gangue is ≤30%.

[0012] Preferably, the construction waste is solid waste-based porous brick; the particle size of the solid waste-based porous brick is 1~3mm.

[0013] Preferably, the activated artificial soil also includes a mycorrhizal fungal agent.

[0014] Preferably, the content of coal gangue in the sandy soil conditioner is 60-85 wt.%, and the content of porous material is 15-40 wt.%.

[0015] Preferably, the particle size of the coal gangue is <0.5mm.

[0016] Preferably, the porous material includes at least one of biochar, water-retaining agent, and solid waste-based porous brick.

[0017] Preferably, the mass ratio of the soil conditioner to the soil is 4:6 to 1:9.

[0018] This invention provides a method for land improvement using coal-based solid waste in conjunction with agricultural waste, comprising: when the land improvement is for mining area land remediation, the method includes: mixing coal gangue, construction waste, and organic fertilizer to obtain activated artificial soil, and then using the activated artificial soil for mining area land remediation; when the land improvement is for desertification land improvement, the method includes: mixing a sandification soil conditioner and sandification soil to obtain improved soil, and then using the improved soil for desertification land improvement; the sandification soil conditioner includes coal gangue and porous materials. This invention provides a method that uses solid waste such as coal gangue as the main raw material, offering different application methods for mine land remediation and desertified land improvement. Through a scientific, rational, economical, and safe ecological restoration approach, it is suitable for addressing desertification in mining areas and meeting the ecological restoration needs of these areas. It provides a practical solution for regions where coal-based industries and animal husbandry are pillar industries, achieving the ecological restoration effect of treating waste with waste and turning waste into treasure. The organic matter content of coal gangue is maintained between 15% and 25%, and it is rich in trace elements, which is beneficial to plant growth. The addition of biochar improves the soil pore structure, enhances the soil's water retention capacity, and also contains nutrients and fixes heavy metals in the soil. Water-retaining agents can improve the soil's water retention capacity. The addition of porous bricks based on solid waste facilitates the adsorption of bacteria and other microorganisms, thereby decomposing the organic components in the mixture and improving soil fertility. Construction waste or porous materials facilitate the adsorption of bacteria and other microorganisms, thereby decomposing the organic components in the mixture and improving soil fertility. The results of the embodiments show that when the method provided by the present invention is used for land improvement, it can effectively increase the bulk density and field water holding capacity of primary artificial soil and reduce the air-water ratio, thereby helping the artificial soil to better retain moisture. After 3 months, 6 months and 12 months of planting vegetation, the nutrients in the soil are significantly improved. At the same time, the improved soils all meet the standards of the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB15618-2018). Detailed Implementation

[0019] This invention provides a method for land improvement using coal-based solid waste in conjunction with agricultural waste, comprising: When the land improvement is for mining area land remediation, the land improvement method includes: mixing coal gangue, construction waste and organic fertilizer to obtain activated artificial soil, and then using the activated artificial soil for mining area land remediation; When the land improvement is for desertified land improvement, the land improvement method includes: mixing a sandy soil conditioner and sandy soil to obtain improved soil, and then using the improved soil for desertified land improvement; the sandy soil conditioner includes coal gangue and porous materials.

[0020] In this invention, when the land improvement is for mining area land remediation, the land improvement method includes: mixing coal gangue, construction waste and organic fertilizer to obtain activated artificial soil, and then using the activated artificial soil for mining area land remediation.

[0021] In this invention, the activated artificial soil preferably comprises 30-80% coal gangue, 15-20% construction waste, and ≤10% organic fertilizer, based on a mass percentage of 100%.

[0022] In this invention, taking the activated artificial soil as 100% by mass, the activated artificial soil preferably comprises 30-80% coal gangue. As one embodiment of this invention, the mass percentage of the coal gangue can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%. By using coal gangue as a raw material, this invention not only consumes a large amount of coal gangue, reducing costs, but also, because coal gangue is rich in minerals such as silicon, aluminum, and calcium, mixing it with organic fertilizer can improve its adsorption and nutrient slow-release capacity.

[0023] In this invention, the coal gangue includes small coal gangue particles of 0.5-1 mm, medium coal gangue particles of 1-2 mm, and large coal gangue particles >2 mm. In this invention, based on the mass of the coal gangue as 100%, the proportion of small coal gangue particles is preferably 40-80%; the proportion of medium coal gangue particles is preferably ≤30%; and the proportion of large coal gangue particles is preferably ≤30%. As one embodiment of this invention, the proportion of small coal gangue particles can be 40%, 45%, 50%, 55%, 60%, 65%, 70 wt.%, 75%, or 80%; the proportion of medium coal gangue particles can be 5%, 10%, 15%, 20%, 25%, or 30%; and the proportion of large coal gangue particles can be 5%, 10%, 15%, 20 wt.%, 25%, or 30%. In this invention, the organic matter content of coal gangue is maintained between 15% and 25%, and it is rich in trace elements, which is beneficial to plant growth.

[0024] In this invention, the activated artificial soil preferably comprises 15-20% construction waste, with the activated artificial soil comprising 100% by mass. The construction waste is preferably solid waste-based porous bricks; the particle size of the solid waste-based porous bricks is preferably 1-3 mm. As one embodiment of this invention, the mass percentage of construction waste can be 15%, 16%, 17%, 18%, 19%, or 20%; the particle size of the solid waste-based porous bricks can be 1 mm, 1.5 mm, 2 mm, 2.5 mm, or 3 mm. This invention, by adding solid waste-based porous bricks, facilitates the adsorption of bacteria and other microorganisms, thereby decomposing the organic components in the mixture and improving soil fertility.

[0025] In this invention, taking the activated artificial soil as 100% by mass, the activated artificial soil preferably includes ≤10% organic fertilizer, more preferably 1-10%. As one embodiment of this invention, the mass percentage of the organic fertilizer can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. By adding organic fertilizer, this invention effectively improves soil properties, enhances the diversity of microorganisms in the soil, strengthens soil enzyme activity, and reduces salinization.

[0026] In this invention, the organic fertilizer is preferably a coal-based solid waste and agricultural waste modified organic fertilizer.

[0027] In this invention, the method for preparing the coal-based solid waste and agricultural waste-modified organic fertilizer preferably includes the following steps: (1) Mix coarse coal gangue, long straw and fly ash to obtain a filler for livestock sheds; the particle size of the coarse coal gangue is 2~10mm; the length of the long straw is ≤5cm; (2) Mix fine coal gangue, short straw and filler to obtain topsoil for livestock sheds; the particle size of the fine coal gangue is <2mm; the length of the short straw is ≤1cm; (3) Lay the livestock shed filling material obtained in step (1) to obtain the livestock shed filling material layer, and then use the livestock shed topsoil obtained in step (2) to lay the livestock shed topsoil layer on the upper surface of the livestock shed filling material layer to obtain the underground pit livestock shed structure. (4) Livestock breeding is carried out in the underground pit-type livestock house structure obtained in step (3). During the livestock breeding process, the manure is cleaned and stored. After the livestock breeding is completed, the topsoil layer, the filling layer and the stored manure are composted to obtain coal-based solid waste synergistic agricultural waste modified organic fertilizer. The preparation of steps (1) and (2) is not sequential.

[0028] The present invention preferably mixes coarse coal gangue, long straw and fly ash to obtain a filler for livestock sheds.

[0029] In this invention, the particle size of the coarse coal gangue is preferably 2-10 mm. Preferably, the coarse coal gangue is prepared by crushing and screening coal gangue. This invention does not impose specific limitations on the crushing and screening operations, as long as the particle size of the coarse coal gangue meets the requirements. As one embodiment of this invention, the particle size of the coarse coal gangue can be 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm.

[0030] In this invention, the length of the long straw is preferably ≤5cm. The long straw is preferably obtained by cutting straw. This invention does not impose any special limitations on the specific cutting operation, as long as the length of the long straw meets the requirements. As one embodiment of this invention, the length of the long straw can be 1.5~5cm, or it can be 2cm, 2.5cm, 3cm, 3.5cm, 4cm, or 4.5cm.

[0031] This invention does not specifically limit the source of the coal gangue, straw, and fly ash; any coal gangue, straw, and fly ash well-known to those skilled in the art can be used. This invention uses coal gangue, straw, and fly ash as raw materials, all of which are solid wastes. This not only allows for the large-scale consumption of solid wastes, avoiding environmental pollution, but also enables their high-value resource utilization and reduces production costs.

[0032] In this invention, the livestock shed filler material preferably comprises, by mass percentage, 60-70% coarse coal gangue, 15-20% long straw, and 10-30% fly ash. As one embodiment of this invention, the mass percentage of coarse coal gangue in the livestock shed filler material can be 60%, 62%, 65%, 68%, or 70%; the mass percentage of long straw can be 15%, 16%, 17%, 18%, 19%, or 20%; and the mass percentage of fly ash can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, or 30%. By controlling the proportions of these three components, this invention can form a livestock shed filler material with a porosity of 15-20% after mixing. In this invention, coal gangue and fly ash serve as the main skeleton materials. Due to their high mechanical strength and stable physicochemical properties, they provide a robust support structure, ensuring the stability of the livestock shed filling layer during long-term use and preventing structural damage caused by self-weight settling or external forces. They also prevent the pores of the filling layer from collapsing, thus maintaining a good infiltration environment and air permeability. Long straw enhances the infiltration capacity of the livestock shed filling. Its fibrous structure not only facilitates the uniform infiltration of urine and feces, preventing uneven decomposition caused by local accumulation, but also optimizes moisture management. By adjusting the pore moisture content, it prevents the system from becoming excessively dry, affecting microbial activity, or from becoming excessively moist, causing anaerobic putrefaction, thus ensuring a stable aerobic fermentation environment. The livestock shed filling material provided by this invention has good cation exchange performance. The surface of coal gangue and fly ash can effectively adsorb ammonium nitrogen in urine, reduce the release of ammonia and other volatile organic compounds, reduce the risk of environmental pollution, and improve the retention and recycling efficiency of nitrogen, so that it can be further fixed by microorganisms or converted into an effective nitrogen source that can be absorbed and utilized by plants. At the same time, by adjusting the air permeability, moisture content and carbon-nitrogen ratio of the livestock shed filling material, the metabolic activities of the microbial community can be optimized, so that organic matter can be decomposed at a preset rate, avoiding the overheating effect caused by excessively rapid degradation or the generation of malodor and anaerobic putrefaction due to incomplete degradation.

[0033] The present invention does not have any particular limitation on the specific method of mixing the coarse coal gangue, long straw and fly ash, as long as they are mixed evenly.

[0034] The present invention preferably mixes fine coal gangue, short straw and filler to obtain the topsoil for livestock sheds.

[0035] In this invention, the particle size of the fine-grained coal gangue is preferably <2 mm. The fine-grained coal gangue is preferably prepared from coal gangue through crushing and screening. This invention does not impose any particular limitation on the specific crushing and screening operations, as long as the particle size of the fine-grained coal gangue meets the requirements. As one embodiment of this invention, the particle size of the fine-grained coal gangue can be 0.1~1.8 mm, and can also be 0.2 mm, 0.3 mm, 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, or 1.5 mm.

[0036] In this invention, the length of the short straw is preferably ≤1cm. The short straw is preferably obtained by cutting straw. This invention does not impose any special limitations on the specific cutting operation, as long as the length of the short straw meets the requirements. As one embodiment of this invention, the length of the short straw can be 0.1~1cm, or it can be 0.2cm, 0.3cm, 0.5cm, 0.6cm, or 0.8cm.

[0037] In this invention, the filler preferably comprises slag and / or loess. In this invention, the particle size of the slag is preferably ≤1 cm.

[0038] In this invention, the topsoil used for livestock sheds preferably comprises 60-70% fine-grained coal gangue, 15-20% short straw, and 15-20% filler, by weight percentage. As one embodiment of this invention, the weight percentage of fine-grained coal gangue in the topsoil can be 60%, 62%, 65%, 68%, or 70%; the weight percentage of short straw can be 15%, 16%, 17%, 18%, 19%, or 20%; and the weight percentage of filler can be 15%, 16%, 17%, 18%, 19%, or 20%. In this invention, livestock move above the topsoil layer, and their urine naturally seeps down through the topsoil to the filler layer for storage and initial fermentation. Manure accumulates in the topsoil layer and is scraped away after reaching a certain level, then temporarily stored for further composting.

[0039] After obtaining the livestock shed filler and the livestock shed topsoil, the present invention preferably lays the livestock shed filler to obtain a livestock shed filler layer, and then uses the livestock shed topsoil to lay a livestock shed topsoil layer on the upper surface of the livestock shed filler layer to obtain an underground pit livestock shed structure.

[0040] The present invention does not have any special limitation on the specific method of laying the livestock shed filling material. Any laying method known to those skilled in the art can be used to ensure that the thickness of the livestock shed filling material layer meets the requirements.

[0041] In this invention, the livestock shed filler is preferably laid on a seepage-proof layer. The thickness of the seepage-proof layer is preferably 0.3~0.5m.

[0042] In this invention, the raw materials for preparing the impermeable layer preferably include fly ash, carbide slag, desulfurized gypsum, and water. By using the above-mentioned components as raw materials, this invention enables the impermeable layer to have a good impermeability, preventing urine and other substances from seeping into the ground and polluting groundwater during aquaculture.

[0043] In this invention, the raw materials for preparing the impermeable layer preferably include 60-70 parts of fly ash, 20-30 parts of carbide slag, 10-20 parts of desulfurized gypsum, and water, by weight. By controlling the amounts of fly ash, carbide slag, and desulfurized gypsum, this invention can further improve the impermeability of the impermeable layer.

[0044] In this invention, the amount of water used is preferably such that the solid-liquid ratio is 0.50 to 0.70. By controlling the amount of water used, this invention can ensure that the raw materials have good fluidity after mixing, thereby facilitating subsequent coating into an impermeable layer.

[0045] In this invention, the preferred method for preparing the impermeable layer includes: mixing fly ash, carbide slag, desulfurized gypsum, and water, and then coating the mixture onto the bottom and sides of the underground pit to form an impermeable layer. This invention does not impose any specific limitations on the mixing method; any method that ensures the fly ash, carbide slag, desulfurized gypsum, and water are mixed evenly is acceptable.

[0046] In this invention, the thickness of the livestock shed filler layer is preferably 1.5~2m. In this invention, the livestock shed filler layer has a porous structure, playing multiple roles in livestock farming, including storing urine, promoting fermentation, supporting the filler, regulating filtration, cation exchange, and controlled decomposition.

[0047] In this invention, the livestock shed filling layer preferably further includes an exhaust pipe and a microbial agent inoculation pipe. The invention does not impose any particular limitation on the arrangement of the exhaust pipe and microbial agent inoculation pipe; it can be determined based on the technical knowledge of those skilled in the art. In this invention, the exhaust pipe is preferably an inside-out exhaust pipe; the microbial agent inoculation pipe is preferably an outside-in microbial agent inoculation pipe. The exhaust pipe facilitates the collection and emission of fermentation gases; the microbial agent inoculation pipe is used to regulate the fermentation process and inoculate microbial agents, thereby improving the fermentation efficiency within the livestock shed filling layer.

[0048] The present invention does not have any special limitations on the specific operation of laying the topsoil for the livestock shed, as long as it can ensure that it does not affect the structure of the filler layer of the livestock shed and that the thickness of the topsoil layer of the livestock shed meets the requirements.

[0049] In this invention, the thickness of the topsoil layer used for lining the livestock shed is preferably 0.3~0.5m. This invention facilitates livestock farming by controlling the thickness of the topsoil layer.

[0050] After obtaining the underground pit-type livestock shed structure, the present invention preferably conducts poultry and livestock breeding in the underground pit-type livestock shed structure. During the poultry and livestock breeding process, the manure is cleaned and stored. After the poultry and livestock breeding is completed, the topsoil layer, the filling layer and the stored manure are composted to obtain coal-based solid waste synergistic agricultural waste modified organic fertilizer.

[0051] This invention does not specifically limit the types of poultry and livestock raised; the types of poultry and livestock raised can be determined based on the technical knowledge of those skilled in the art. In one embodiment of this invention, the poultry and livestock raised can be pigs, cattle, sheep, chickens, ducks, or geese.

[0052] In this invention, the preferred time for raising poultry and livestock is from September to April of the following year. By raising poultry and livestock during this period, this invention can avoid the death of poultry and livestock due to low outdoor temperatures. At the same time, during the raising process, the urine and other substances stored in the bedding layer of the livestock shed will generate heat through fermentation, which can reduce the energy consumption for keeping the poultry and livestock warm.

[0053] In this invention, the preferred cleaning method is scraper cleaning. This invention does not have a specific limitation on the cleaning time interval; it can be determined based on the technical knowledge of those skilled in the art, as long as it avoids the negative impact of manure accumulation on livestock.

[0054] This invention does not impose any special limitations on the storage method; storage can be carried out in accordance with the technical common sense of those skilled in the art.

[0055] Preferably, this invention involves excavating the topsoil and filler layers of the livestock shed before composting, and then mixing them with the stored manure before composting. This invention does not have specific limitations on the excavation process; it simply requires transferring the excavated material to the composting site and mixing it with the manure.

[0056] In this invention, the moisture content of the raw materials during composting is preferably 45-65%; the composting time is preferably 20-30 days; the composting temperature is preferably 50-65℃; the composting temperature is preferably ≥55℃ for at least 5 days; and the compost turning frequency is preferably: once a day when the composting time is ≤12 days, once every 2-3 days for the remaining composting time, and 2-4 times every 2 days when the composting temperature is ≥60℃. This invention improves the quality of organic fertilizer by controlling the composting process; and improves composting efficiency by regularly turning the compost to promote oxygen supply and uniform temperature distribution.

[0057] The present invention preferably also includes adding bacterial solution and additives during composting.

[0058] In this invention, the bacterial solution is preferably a commercially available EM bacterial solution; the amount of the bacterial solution used is preferably 0.05~0.2% of the total mass of the raw materials during composting, more preferably 0.1%. In this invention, the main components of the EM bacterial solution are composed of more than 80 microorganisms from 10 genera, including photosynthetic bacteria, lactic acid bacteria, yeast, and actinomycetes, which can improve the efficiency of composting.

[0059] In this invention, the additives are preferably chemical additives and / or physical additives; the chemical additives preferably include at least one of magnesium hydroxide, potassium dihydrogen phosphate, and magnesium chloride; the amount of the chemical additives is preferably 0.5-2% of the total mass of the raw materials during composting, more preferably 1-1.5%; the physical additives preferably include biochar and / or bentonite; the amount of the physical additives is preferably 2.5-10% of the total mass of the raw materials during composting, more preferably 3-8%, and even more preferably 4-6%. This invention, by adding additives, can further improve the efficiency of composting and the fertility of organic fertilizers.

[0060] This invention uses coal gangue, straw, and fly ash as raw materials to prepare the livestock shed filler layer, and coal gangue, straw, and filler as raw materials to prepare the livestock shed topsoil layer. During the livestock raising process, livestock move on the topsoil layer, and their urine naturally seeps through the topsoil layer into the filler layer for storage and initial fermentation. Manure gradually accumulates on the topsoil layer and is periodically removed and stored for later use. The filler layer, relying on the synergistic effect of porous materials such as coarse coal gangue, fly ash, and straw, can not only uniformly absorb and store urine, but also... Preventing localized excessive moisture or dryness also optimizes the infiltration environment, promotes the slow-release decomposition of manure and nitrogen fixation, reduces the emission of harmful gases such as ammonia, and improves the air quality of the farm. After the livestock and poultry breeding is completed, the filling layer and topsoil layer of the livestock shed are cleaned up as a whole, and the partially decomposed organic matter and nitrogen-adsorbed filling material are removed and centrally composted. Combined with measures such as adjusting the carbon-nitrogen ratio, turning the compost to increase oxygen, and strengthening with microbial agents, the degradation and maturation of organic matter are further accelerated, so that it is eventually transformed into highly efficient and stable organic fertilizer.

[0061] In this invention, the activated artificial soil preferably further comprises ≤10% biochar, more preferably 1-10%. As one embodiment of this invention, the mass percentage of the biochar can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. This invention does not impose a specific limitation on the particle size of the biochar; it can be determined based on the technical knowledge of those skilled in the art. In this invention, biochar can provide a small amount of nutrients and fix heavy metals in the soil.

[0062] In this invention, the activated artificial soil preferably further includes an mycorrhizal fungal agent (AMF). The amount of AMF added is preferably 0.01-0.1% of the mass of the activated artificial soil. As one embodiment of this invention, the amount of AMF added can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1% of the mass of the activated artificial soil. The addition of AMF in this invention enables a mutually beneficial symbiotic relationship with plant roots, improves the rhizosphere microenvironment, reduces the application of chemical fertilizers, and solidifies heavy metals through mycelial secretions.

[0063] In this invention, the preferred method for using the activated artificial soil for mine land remediation is to transfer the activated artificial soil to a pit in the mine area or to directly cover it, followed by planting vegetation. In this invention, the covering material is preferably mine soil. This invention does not impose any special limitations on the thickness of the covering; it can be determined based on the technical knowledge of those skilled in the art.

[0064] This invention does not impose any specific limitation on the type of vegetation; any easily cultivated vegetation known to those skilled in the art can be used. As one embodiment of this invention, the vegetation can be pasture grass suitable for local climate and soil conditions.

[0065] This invention uses the above-mentioned method to remediate land in mining areas. After about 0.5 to 3 years, the soil can become activated nutrient soil, achieving self-sustaining growth. It can be used to plant other plants or crops, and can also be used as nutrient soil for direct covering in other sites.

[0066] In this invention, when the land improvement is for desertified land improvement, the land improvement method includes: mixing a sandy soil conditioner and sandy soil to obtain improved soil, and then using the improved soil for desertified land improvement; the sandy soil conditioner includes coal gangue and porous materials.

[0067] In this invention, the preferred content of coal gangue in the soil conditioner is 60-85 wt.%; the preferred content of porous material in the soil conditioner is 15-40 wt.%. As one embodiment of this invention, the content of coal gangue in the soil conditioner can be 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, or 85 wt.%; the content of porous material in the soil conditioner can be 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, or 40 wt.%.

[0068] In this invention, the particle size of the coal gangue is preferably <0.5 mm. Using the aforementioned coal gangue allows for more uniform mixing with porous materials.

[0069] In this invention, the porous material preferably includes at least one of biochar, a water-retaining agent, and solid waste-based porous bricks; the water-retaining agent preferably includes at least one of polymeric water-retaining agents, microbial water-retaining agents, mineral water-retaining agents, and organosilicon water-retaining agents. In this invention, the biochar content in the desertified soil conditioner is preferably 0-10 wt.%; the water-retaining agent content in the desertified soil conditioner is preferably 0-10 wt.%; the solid waste-based porous brick content in the desertified soil conditioner is preferably 15-20 wt.%; and the particle size of the solid waste-based porous bricks is preferably 1-3 mm. In one embodiment of the present invention, the biochar content in the desertified soil conditioner can be 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, or 10 wt.%; the water-retaining agent content in the desertified soil conditioner can be 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, or 10 wt.%; the solid waste-based porous brick content in the desertified soil conditioner can be 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, or 20 wt.%; and the particle size of the solid waste-based porous brick can be 1 mm, 1.5 mm, 2 mm, 2.5 mm, or 3 mm. In this invention, the organic matter content of coal gangue is maintained between 15% and 25%, and it is rich in trace elements, which is beneficial to plant growth. The addition of biochar improves the soil pore structure, enhances the soil's water retention capacity, and also contains nutrients and fixes heavy metals in the soil. The water-retaining agent can enhance the soil's water retention capacity. The addition of porous bricks based on solid waste facilitates the adsorption of bacteria and other microorganisms, thereby decomposing the organic components in the mixture and improving soil fertility.

[0070] In this invention, the preferred mass ratio of the soil conditioner to the desertified soil is 4:6 to 1:9. As one embodiment of this invention, the mass ratio of the soil conditioner to the desertified soil can be 3:7 or 2:8. By controlling the ratio of the two, this invention can reduce the cost of improving desertified soil.

[0071] In this invention, the improved soil preferably also includes organic fertilizer; the organic fertilizer is preferably a modified organic fertilizer made from coal-based solid waste and agricultural waste. In this invention, the preparation method of the modified organic fertilizer made from coal-based solid waste and agricultural waste is preferably the same as the aforementioned preparation method, and will not be repeated here. In this invention, the amount of organic fertilizer is preferably 0-10% of the mass of the sandy soil conditioner, more preferably 1-8%, and even more preferably 2-5%. This invention, by adding organic fertilizer, effectively improves soil properties, enhances the diversity of microorganisms in the soil, strengthens soil enzyme activity, and reduces the degree of salinization.

[0072] The present invention preferably further includes adding an mycorrhizal fungal inoculant (AMF) to the improved soil. In this invention, the amount of AMF added is preferably 0.01-0.1% of the improved soil mass. As one embodiment of the present invention, the amount of AMF added can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1% of the improved soil mass. The addition of AMF in this invention enables a mutually beneficial symbiotic relationship with plant roots, improves the soil root microenvironment, reduces the application of chemical fertilizers, and immobilizes heavy metals through mycelial secretions.

[0073] This invention provides different application methods for mine land restoration and desertified land improvement. Through scientific, reasonable and economical ecological restoration methods, it is applicable to solving the needs of mine land desertification and ecological restoration. It provides a practical solution for regions with coal-based industries and animal husbandry as pillar industries, achieving the ecological restoration effect of treating waste with waste and turning waste into treasure.

[0074] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0075] The preparation method of the coal-based solid waste and agricultural waste-modified organic fertilizer used in the examples and comparative examples includes the following steps: (1) Based on the mass of the livestock shed filler as 100%, 65% coarse coal gangue, 15% long straw and 20% fly ash are mixed evenly to obtain a livestock shed filler with a porosity of about 20%; the particle size of the coarse coal gangue is 2~10mm and the length of the long straw is 1.5~5cm. (2) Based on the mass of the topsoil used for laying livestock sheds being 100%, 60% fine coal gangue, 20% short straw, and 20% slag are mixed evenly to obtain the topsoil used for laying livestock sheds; the particle size of the fine coal gangue is <2mm; the length of the short straw is ≤1cm. (3) The livestock shed filling material obtained in step (1) is laid on the upper surface of the seepage-proof layer to obtain a livestock shed filling material layer with a thickness of 2m. An exhaust pipe from the inside to the outside and a microbial agent injection pipe from the outside to the inside are set in the livestock shed filling material layer. Then, a livestock shed topsoil layer with a thickness of 0.5m is laid on the upper surface of the livestock shed filling material layer to obtain an underground pit livestock shed structure. The seepage-proof layer is prepared by mixing 65 parts of fly ash, 25 parts of carbide slag and 10 parts of desulfurized gypsum by mass, then adding water to adjust the solid-liquid ratio to 0.65, stirring evenly and then coating it on the bottom and around the underground pit to form a seepage-proof layer with a thickness of 0.5m. (4) Shanxi beef cattle are raised in the underground pit-type livestock shed structure obtained in step (3). The raising period is from September to April of the following year. During the raising of Shanxi beef cattle, the manure is scraped and stored. After the raising of Shanxi beef cattle is completed, the topsoil layer, the filling layer and the stored manure are composted. The moisture content of the raw materials during composting is 50-60%. The composting time is 30 days. The composting temperature is 50-65℃. The composting temperature is ≥55℃ for 6 days. The preferred frequency of turning the compost is: once a day during the first 10 days of composting, once every 2 days during the remaining composting time, and 4 times every 2 days when the composting temperature is ≥60℃, to obtain coal-based solid waste synergistic agricultural waste modified organic fertilizer.

[0076] Analysis of the obtained coal-based solid waste and agricultural waste modified organic fertilizer showed that it met the requirements of the "Organic Fertilizer Standard" (NY / T 525-2021), effectively realizing the comprehensive utilization of solid waste.

[0077] Examples 1-5 Coal gangue and construction waste are mixed to obtain primary artificial soil. Then, the primary artificial soil is mixed with coal-based solid waste and agricultural waste modified organic fertilizer to obtain activated artificial soil. The activated artificial soil is then transferred to the pit in the mining area and finally planted with vegetation to prepare local forage. Based on the mass percentage of activated artificial soil being 100%, the activated artificial soil is composed of 75% coal gangue, 20% solid waste-based porous bricks, and 5% coal-based solid waste synergistic agricultural waste modified organic fertilizer; the particle size of the solid waste-based porous bricks is 2mm. The coal gangue is composed of small coal gangue particles of 0.5-1mm, medium coal gangue particles of 1-2mm, and large coal gangue particles of >2mm; the proportions of small, medium, and large coal gangue particles are shown in Table 1.

[0078] Comparative Example 1 Coal gangue and construction waste are mixed to obtain primary artificial soil, which is then transferred to a pit in the mining area and finally planted with vegetation. Based on a mass percentage of 100% for the primary artificial soil, the primary artificial soil consists of 80% coal gangue and 20% solid waste-based porous bricks; the particle size of the solid waste-based porous bricks is 2mm.

[0079] Table 1. Particle size distribution of coal gangue in Examples 1-5 and Comparative Example 1

[0080] The performance parameters of the primary artificial soils obtained in Examples 1-5 and Comparative Example 1 are shown in Table 2: Table 2 shows the performance parameters of the primary artificial soil obtained in Examples 1-5 and Comparative Example 1.

[0081] As can be seen from Table 2, by selecting coal gangue of different grades during the preparation of primary artificial soil, this invention can effectively increase the bulk density and field water holding capacity of primary artificial soil, and reduce the air-water ratio, thereby helping the artificial soil to better retain moisture and laying the foundation for subsequent vegetation planting.

[0082] Table 3 shows the nutrient composition of vegetation (local pasture) planted in the artificial soil provided in Examples 1-5 and Comparative Example 1 after 3 months, 6 months, and 12 months: Table 3. Nutrient composition of artificial soil-grown vegetation in Examples 1-5 and Comparative Example 1 at 3, 6, and 12 months.

[0083] As can be seen from Table 3, after adding the coal-based solid waste and agricultural waste modified organic fertilizer provided by this invention to the artificial soil, the nutrient content in the soil far exceeded that of the comparative sample after 3 months, 6 months and 12 months of planting vegetation. This indicates that the coal-based solid waste and agricultural waste modified organic fertilizer provided by this invention can effectively improve soil fertility.

[0084] Example 6 Based on Example 1, adjustments were made to the activated artificial soil, which consisted of 77% coal gangue, 20% solid waste-based porous bricks, and 3% coal-based solid waste synergistic agricultural waste modified organic fertilizer, with the activated artificial soil comprising 100% by mass. AMF was added to the activated artificial soil at a rate of 0.05% of its mass. Other conditions were the same as in Example 1.

[0085] Comparative Example 2 Activated farmland soil is obtained by mixing farmland soil and coal-based solid waste with modified organic fertilizer made from agricultural waste. Based on the mass percentage of activated farmland soil being 100%, the activated farmland soil consists of 95% farmland soil and 5% coal-based solid waste synergistic agricultural waste modified organic fertilizer.

[0086] The physicochemical properties of the activated artificial soil obtained in Examples 1 and 6 and the activated farmland soil provided in Comparative Example 2 were tested. pH and conductivity were determined using the electrode method, available phosphorus was determined using the sodium bicarbonate extraction-molybdenum-antimony anti-spectrophotometric method, and alkaline nitrogen was determined using the alkaline diffusion method. The results are shown in Table 4. Table 4. Physicochemical properties and nutrient changes of the activated artificial soil obtained in Examples 1 and 6 and the activated farmland soil provided in Comparative Example 2.

[0087] As shown in Table 4, when organic fertilizer is reduced, the addition of AMF has a significant effect on reducing the EC value of the rhizosphere in artificial soil and increasing rhizosphere nutrients.

[0088] Example 7 Coal gangue with a particle size <0.5mm and porous bricks based on solid waste with a particle size of 2mm were mixed to obtain a soil conditioner for desertification. The content of porous bricks based on solid waste in the soil conditioner was 15wt.%. Then, the soil conditioner and desertified soil were mixed at a mass ratio of 4:6 to obtain a mixture. Finally, coal-based solid waste synergistic agricultural waste modified organic fertilizer was added at a dosage of 10% of the mass of the soil conditioner to improve desertified land.

[0089] Example 8 The mass ratio of the soil conditioner to the soil was 3:7, and other conditions were the same as in Example 7.

[0090] Example 9 The mass ratio of the soil conditioner to the soil was 2:8, and other conditions were the same as in Example 7.

[0091] Example 10 The mass ratio of the soil conditioner to the sandy soil was 1:9, and other conditions were the same as in Example 7.

[0092] Comparative Example 3 No soil conditioner was added, and all other conditions were the same as in Example 7.

[0093] The moisture characteristics of the mixtures obtained in Examples 7-10 and the sandy soil in Comparative Example 3 are shown in Table 5: Table 5 shows the moisture characteristics of the mixtures obtained in Examples 7-10 and the sandy soil in Comparative Example 3.

[0094] The water infiltration characteristics of the mixtures obtained in Examples 7-10 and the sandy soil in Comparative Example 3 are shown in Table 6: Table 6 shows the water infiltration characteristics of the mixtures obtained in Examples 7-10 and the sandy soil in Comparative Example 3.

[0095] As can be seen from Tables 5 and 6, with the increase of coal gangue content, the saturated moisture content, field water holding capacity and total porosity of the mixture gradually increase, the water infiltration rate decreases, the cumulative infiltration amount decreases, and the water retention capacity is enhanced.

[0096] The heavy metal risk assessment of the primary artificial soil in Example 1, the activated artificial soil in Example 4, and the mixture in Example 7 was conducted by full digestion, and the contents of As, Cd, Cr, Hg, and Pb were measured as shown in Table 7. Table 7. Heavy metal content of the primary artificial soil in Example 1, the activated artificial soil in Example 4, and the mixture in Example 7.

[0097] As can be seen from Table 7, the above soils all meet the standards of the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (Trial)" (GB15618-2018), indicating that the solution of the present invention will not lead to an increase in the heavy metal content in the soil.

[0098] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for land improvement using coal-based solid waste in conjunction with agricultural waste, comprising: When the land improvement is for mining area land remediation, the land improvement method includes: mixing coal gangue, construction waste and organic fertilizer to obtain activated artificial soil, and then using the activated artificial soil for mining area land remediation; Based on a mass percentage of 100% for activated artificial soil, the activated artificial soil comprises 30-80% coal gangue, 15-20% construction waste, and ≤10% organic fertilizer; the organic fertilizer is a modified organic fertilizer made from coal-based solid waste and agricultural waste. The activated artificial soil is used for land remediation in mining areas by transferring it to pits in the mining area or directly covering them, and then planting vegetation; the covering material used is mining area soil. When the land improvement is for desertified land improvement, the land improvement method includes: mixing a sandy soil conditioner and sandy soil to obtain improved soil, and then using the improved soil for desertified land improvement; the sandy soil conditioner includes coal gangue and porous materials; The sandy soil conditioner contains 60-85 wt.% coal gangue and 15-40 wt.% porous material; the improved soil also includes organic fertilizer; the organic fertilizer is a modified organic fertilizer made from coal-based solid waste and agricultural waste; the amount of organic fertilizer used is 1-8% of the mass of the sandy soil conditioner. The mass ratio of the soil conditioner to the desertified soil is 4:6 to 1:

9. The preparation method of the coal-based solid waste and agricultural waste-modified organic fertilizer includes the following steps: (1) Mix coarse coal gangue, long straw and fly ash to obtain livestock shed filler; the particle size of the coarse coal gangue is 2~10mm; the length of the long straw is ≤5cm; by mass percentage, the livestock shed filler includes 60~70% coarse coal gangue, 15~20% long straw and 10~30% fly ash; (2) Mix fine coal gangue, short straw and filler to obtain topsoil for livestock sheds; the particle size of the fine coal gangue is <2mm; the length of the short straw is ≤1cm; by mass percentage, the topsoil for livestock sheds includes 60-70% fine coal gangue, 15-20% short straw and 15-20% filler; (3) The livestock shed filling material obtained in step (1) is laid to obtain a livestock shed filling material layer. Then, the livestock shed topsoil obtained in step (2) is used to lay a livestock shed topsoil layer on the upper surface of the livestock shed filling material layer to obtain an underground pit livestock shed structure. The thickness of the livestock shed filling material layer is 1.5~2m. The thickness of the livestock shed topsoil layer is 0.3~0.5m. (4) Livestock breeding is carried out in the underground pit-type livestock shed structure obtained in step (3). During the livestock breeding process, the manure is cleaned and stored. After the livestock breeding is completed, the topsoil layer, the filler layer and the stored manure are composted to obtain coal-based solid waste synergistic agricultural waste modified organic fertilizer. The moisture content of the raw materials during composting is 45-65%. The composting time is 20-30 days. The composting temperature is 50-65℃. The composting temperature is ≥55℃ for ≥5 days. The composting turning frequency is: once a day when the composting time is ≤12 days, once every 2-3 days during the remaining composting time, and 2-4 times every 2 days when the composting temperature is ≥60℃. The preparation of steps (1) and (2) is not sequential.

2. The method according to claim 1, characterized in that, When the land improvement is for mining area land remediation, the coal gangue includes small coal gangue particles of 0.5~1mm, medium coal gangue particles of 1~2mm, and large coal gangue particles of >2mm.

3. The method according to claim 2, characterized in that, Based on the mass of coal gangue as 100%, the proportion of small-particle coal gangue is 40-80%; the proportion of medium-particle coal gangue is ≤30%; and the proportion of large-particle coal gangue is ≤30%.

4. The method according to claim 1, characterized in that, The construction waste is solid waste-based porous brick; the particle size of the solid waste-based porous brick is 1~3mm.

5. The method according to claim 1, characterized in that, The activated artificial soil also includes mycorrhizal fungi inoculants.

6. The method according to claim 1, characterized in that, The particle size of the coal gangue is <0.5mm.

7. The method according to claim 1, characterized in that, The porous material includes at least one of biochar, water-retaining agent, and solid waste-based porous brick.

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