Coal gangue organic fertilizer and preparation method thereof

Abstract

The invention provides a coal gangue organic fertilizer and a preparation method thereof, and belongs to the technical field of fertilizers. The coal gangue organic fertilizer is prepared by uniformly mixing modified coal gangue, forestry and agricultural residues and a microbial agent, performing high-temperature aerobic composting and aging. Organic components of the coal gangue and nutrient elements such as nitrogen, phosphorus, potassium, calcium and the like required by plant growth are fully utilized, the carrier effect of the coal gangue is also played, and the coal gangue organic fertilizer prepared from the modified coal gangue has a relatively high decomposition degree and is greatly beneficial to seed growth. According to the invention, on one hand, the problems of large stockpiling land occupation and environmental pollution of coal gangue, forestry and agricultural residues and other solid wastes are relieved, and on the other hand, the prepared organic fertilizer can turn waste into wealth and realize solid waste recycling.

Description

Technical Field

[0001] The invention belongs to the technical field of fertilizers, and in particular relates to a gangue organic fertilizer and a preparation method thereof. Background Art

[0002] Gangue, as waste generated during coal mining and processing, is often abandoned and not used for stacking treatment. It not only occupies land, but also pollutes the surrounding soil and groundwater with leaching water from gangue, seriously affecting the ecological environment. Moreover, gangue contains certain combustibles, which will spontaneously combust under suitable conditions, emitting harmful gases such as sulfur dioxide, nitrogen oxides, carbon oxides and smoke, which pollute the atmospheric environment. At present, gangue recycling is mainly used to manufacture building materials such as cement, concrete, and refractory bricks. In addition, it can also be used to recycle coal for power generation. Gangue contains 10% to 40% organic matter and a certain amount of silicon, calcium, iron, nitrogen, phosphorus, potassium and other elements. Therefore, using gangue to prepare organic fertilizer can not only improve the environment, but also realize waste utilization.

[0003] Commonly used organic fertilizers are mainly formed by composting and fermenting organic solid wastes such as crop straw, weeds, leaves, peat, organic household waste, kitchen waste, sludge, human and animal feces, wine lees, and mushroom bran. They generally have high organic matter and nutrients such as nitrogen, phosphorus, and potassium. However, due to the influence of factors such as the source of raw materials, processing conditions, and composting fermentation processes, the product composition and properties of compost vary significantly, and the mineral content in organic fertilizers is relatively low, which to a certain extent limits the application and promotion of organic fertilizer products.

[0004] At present, some methods for preparing organic fertilizer by aerobic composting of coal gangue have been reported in the literature. For example, Chinese patent CN113896578A discloses an organic fertilizer prepared by coal gangue and its preparation method, wherein 400-500 mesh coal gangue and organic solid waste are fermented at 31-32°C to obtain organic fertilizer, which has good water retention and good air permeability, but lacks the fermentation treatment link at high temperature, so the maturity of the product is not high enough. Chinese patent CN114605191A discloses a modified coal gangue bio-organic fertilizer and its preparation method and application, wherein the nutrient components contained in the coal gangue are released by calcining and modifying the coal gangue, but the organic components in the coal gangue are consumed after high-temperature calcination and are not fully utilized. Chinese patent CN114702361A discloses mixing coal gangue with bacterial agents for aerobic fermentation to obtain an organic fertilizer product for improving desertified soil. However, the coal gangue is only used as a matrix and carrier, and the organic components and other nutritional minerals in the coal gangue are not fully utilized.

[0005] Therefore, how to make full use of the organic components and nutrients in coal gangue, improve the effectiveness of organic fertilizer, and give full play to its role as a carrier matrix has become a problem that needs to be solved urgently. At the same time, this problem also restricts the application and promotion of coal gangue resources. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a coal gangue organic fertilizer and a preparation method thereof, so that the organic components and nutrients in the coal gangue are fully released to obtain an organic fertilizer with a high degree of maturity.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The invention provides a coal gangue organic fertilizer, comprising the following raw materials in mass fraction: 3-50% of modified coal gangue and 50-97% of agricultural and forestry wastes, and also comprising 2-6‰ of a microbial fermentation agent based on the total mass of the raw materials, wherein the modified coal gangue is modified by any one of ball milling, oxidation treatment and ultrasonic treatment.

[0009] As an implementation mode, the ball milling treatment includes grinding the coal gangue with a ball mill; the oxidation treatment includes soaking the coal gangue with an oxidant; the ultrasound is ultrasonic treatment of the coal gangue, the sound energy density is 100 to 1200 W / L, and the ultrasonic frequency is 20 kHz.

[0010] Preferably, the modification treatment time is 2 to 8 hours.

[0011] The gangue is crushed and screened before modification, and the crushing is preferably selective crushing so that the particle size of the gangue is 1 to 5 mm.

[0012] In the present invention, the agricultural and forestry wastes include any one or more of livestock and poultry manure, crop straw, wood chips and branches and leaves.

[0013] In the present invention, the microbial fermentation agent includes Bacillus subtilis and Bacillus licheniformis.

[0014] The present invention also provides a method for preparing coal gangue organic fertilizer, and the specific operating steps are as follows:

[0015] The agricultural and forestry waste is crushed and screened, and the coal gangue is modified by ball milling, oxidation treatment or ultrasonic treatment; the screened agricultural and forestry waste is mixed with the modified coal gangue, and the microbial fermentation agent is added to perform composting fermentation; the composting fermentation is performed at 45-70°C for main fermentation for 15-20 days, and at 40-45°C for aging fermentation for 15-30 days.

[0016] As an implementation mode, the particle size of the agricultural and forestry waste after screening is ≤20mm.

[0017] As an embodiment, during the fermentation, the material temperature is above 55° C. for 7 to 10 days.

[0018] As an embodiment, the main fermentation is turned over once every two days, and the aging fermentation is turned over once every five days.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a coal gangue organic fertilizer and a preparation method thereof, which fully utilizes the waste resources of coal gangue and agricultural and forestry wastes, and the coal gangue is modified to prepare the organic fertilizer. The modified coal gangue can be fermented to fully release the organic components and trace elements and other substances rich therein, and the prepared organic fertilizer has a high degree of maturity and can provide sufficient nutrition for subsequent plants. The coal gangue in the present invention not only participates in the humification process of organic components as a reaction subject, but also has a porous structure and strong adsorption property, which makes it a carrier for the attachment of beneficial bacteria, promotes bacterial aggregation and microbial chemical action, promotes the humification process of raw materials and the humification of compost, strengthens the release of nutrients such as nitrogen, phosphorus, potassium and the like in the compost raw materials, and improves the content of nutrient components in the compost product.

[0021] The present invention fully mixes coal gangue with organic solid wastes such as agricultural and forestry wastes, adds an appropriate amount of microbial agents, and then performs high-temperature aerobic composting. After sufficient decomposition, most of the harmful eggs and weed species in the waste die. After testing, the organic matter mass fraction (on a drying basis) in the coal gangue organic fertilizer finally obtained by the present invention is above 60%, and its seed germination index (GI) is about 127% on average, and the GI can reach up to 169.64%, far exceeding the organic matter mass fraction (on a drying basis) ≥30% and GI ≥70% specified in NY525-2021 "Organic Fertilizer". At the same time, the pH value (pH) of the obtained organic fertilizer is about 7.5, which is suitable for agricultural planting and can effectively improve the pH value of the soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a flow chart of coal gangue organic fertilizer and its preparation method. DETAILED DESCRIPTION

[0023] The invention provides a coal gangue organic fertilizer, comprising the following raw materials in mass fraction: 3-50% of coal gangue and 50-97% of agricultural and forestry wastes, and also comprising 2-6‰ of microbial fermentation agent based on the total mass of the raw materials; the coal gangue is modified coal gangue, and the modification method is any one of ball milling, oxidation treatment and ultrasonic treatment.

[0024] The present invention uses coal gangue as raw material to prepare organic fertilizer. In the classification of coal gangue, the coal gangue is divided into four levels according to the fixed carbon content in the coal gangue, namely, the first level is less than 4% low carbon, the second level is 4% to 6% low carbon, the third level is 6% to 20% medium carbon and the fourth level is higher than 20% high carbon. As an embodiment, the coal gangue raw material used in the present invention has an ash content of ≤75%, fixed carbon>5.5%, and volatile matter ≥8.5%. When the ash content of the coal gangue is ≥75%, the coal gangue needs to be crushed and screened to ≤75%, fixed carbon>5.5%, and volatile matter ≥8.5%. As an embodiment, in the ash composition of the coal gangue raw material, SiO 2 Content ≤60%, Al 2 O 3 Content ≥20%, SiO 2 / Al 2 O 3 ratio ≤2.5, and K 2 O content ≥ 1.10%, P 2 O 5 The content is ≥ 1.10%. The mass fraction of the added coal gangue of the present invention is 3 to 50%, more preferably 10 to 45 wt%, and further preferably 20 to 40 wt%.

[0025] The particle size of the gangue of the present invention is 1 to 5 mm. Large particles of gangue are conducive to ventilation and air permeability during the fermentation process, and promote the full decomposition of the fermentation raw materials. The present invention modifies the gangue, and the modification treatment method is any one of ball milling, oxidation treatment and ultrasonic treatment. As an embodiment, the ball milling is carried out with a ball mill. The ball milling time is preferably 2 to 8 hours, and more preferably 3 to 5 hours. As an embodiment, the oxidation treatment is carried out with an oxidant, specifically, the gangue is mixed with 10% of the oxidant in a mass volume ratio of 1: (3 to 7), the mixture is fully stirred and oxidized, washed with water to neutrality, and dried at 60°C to a constant weight. Optional oxidants include hydrogen peroxide and nitric acid. The preferred oxidation time is 2 to 8 hours, and more preferably 3 to 5 hours. As an embodiment, ultrasound is carried out in an ultrasonic machine, specifically, the gangue is placed in a sonic device with an ultrasonic frequency of 20kHz for ultrasound. The ultrasonic energy density is preferably 100-1200W / L, more preferably 200-800W, and further more preferably 400-600W / L; the ultrasonic time is preferably 2-8h, and more preferably 3-5h. The modified gangue has improved activity, improved adsorption capacity and carrying capacity of gangue particles, promoted bacterial aggregation and microbial fermentation, and the prepared organic fertilizer has high maturity, can promote crop seed germination, and has high agricultural economic benefits.

[0026] In the present invention, the mass fraction of agricultural and forestry waste is 50-97%, and the mass fraction is further preferably 55-90%, and the mass fraction is further 60-80%. In the present invention, agricultural and forestry waste includes any one or more of livestock and poultry manure, crop straw, sawdust and branches and leaves. Among them, livestock and poultry manure includes fresh cow dung, sheep dung, pig dung, chicken dung and other livestock and poultry manure produced by farms and farmers, as well as human feces and urine. More preferably, fresh cow dung, sheep dung, pig dung, chicken dung, etc. In the present invention, crop straw is the residue after harvesting seeds of wheat, rice, corn, potatoes, rapeseed, cotton, sugarcane and other crops. Sawdust is waste generated in the process of wood processing. Branches and leaves include fallen leaves, dead branches, withered flowers produced by natural withering of garden plants, and young branches formed by artificial pruning. In the present invention, agricultural and forestry waste must be crushed and screened before application. The crushing is preferably selective crushing, and the particle size of agricultural and forestry waste after screening is ≤20mm. Furthermore, the mesh of the grading sieve for screening is preferably 20 mm. The present invention preferably selects the undersize as the agricultural and forestry waste component of the organic fertilizer compost raw material, and the undersize that does not meet the particle size standard is crushed and screened until the target particle size is reached. Further preferably, the particle size of branches and leaves is 5 to 10 mm, the particle size of crop straw is 2 to 10 mm, and the particle size of wood chips is 2 to 5 mm.

[0027] In the present invention, a microbial fermentation agent is further used, and the microbial fermentation agent includes Bacillus subtilis and Bacillus licheniformis. The present invention does not particularly limit the source of the microbial fermentation agent, and can be a commercially available product or a laboratory-preserved strain. The present invention uses a microbial fermentation agent rich in Bacillus subtilis and Bacillus licheniformis in the preparation of organic fertilizer, effectively degrading substances such as cellulose in fertilizers, promoting the decomposition process of raw materials and the humification of compost, and having a good fermentation effect and a high degree of decomposition. At the same time, these beneficial bacteria act synergistically to inhibit the growth of harmful microorganisms in waste.

[0028] In the present invention, a microbial fermentation agent with a total mass of 2 to 6‰ of the raw materials is used, and more preferably, a microbial fermentation agent with a total mass of 3 to 5‰ of the raw materials is used. As an embodiment, the present invention also includes activation and / or expansion of the microbial fermentation agent before fermentation. The activation is to inoculate the microbial fermentation agent into a common culture medium, and the inoculation amount is preferably 3 to 4% of the mass of the culture medium. The microbial fermentation agent of the present invention comprises Bacillus subtilis and Bacillus licheniformis. After inoculation, the culture is shaken at 180 rpm for 24 hours at 30°C to obtain a seed solution with an effective viable count of ≥ 220 million CFU / mL. The expansion culture includes inoculating a seed solution with a mass fraction of 2 to 6‰ into a fermentation tank filled with a pretreated culture medium, and aerobically culturing for 12 to 48 hours at 30°C to obtain an inoculated agent. The preparation of the culture medium in the fermentation tank includes: crushing corn stalks through a 200-mesh sieve, mixing wheat bran, sawdust and corn stalk powder in a mixing ratio of 2:2:1, and adjusting the carbon-nitrogen ratio to 20:1-25:1 with livestock and poultry breeding wastewater.

[0029] The present invention also provides a preparation method of coal gangue organic fertilizer, which comprises the following steps: crushing and screening the agricultural and forestry waste, modifying the coal gangue by ball milling, oxidation treatment or ultrasonic treatment; mixing the screened agricultural and forestry waste with the modified coal gangue, adding the microbial fermentation agent for composting fermentation; the composting fermentation is carried out at 45-70°C for main fermentation for 15-20 days, wherein the material temperature is ≥55°C for 7-10 days, and aging fermentation is carried out at 40-45°C for 15-30 days. Wherein, the main fermentation process is turned over once every two days, the moisture content is controlled to be 50%-60%, and the carbon-nitrogen ratio (C / N) of the mixed material after stacking is: (20-30):1; the aging fermentation is turned over once every five days, the moisture content in the fermentation product after aging is: 25%-30%, and the carbon-nitrogen ratio in the fermentation product after aging is (C / N): ≤23:1.

[0030] The technical solution provided by the present invention, on the existing basis, further makes full use of the waste resources of coal gangue and agricultural and forestry waste, and modifies the coal gangue to prepare organic fertilizer. The modified coal gangue can fully release the organic components and trace elements and other substances rich therein by fermentation. The prepared organic fertilizer has a high degree of maturity and can provide sufficient nutrition for subsequent plants. After testing, the organic matter mass fraction (on a drying basis) in the coal gangue organic fertilizer finally obtained by the present invention is more than 60%, and its seed germination index (GI) is between 87.95% and 169.64%, which is far more than the organic matter mass fraction (on a drying basis) 30% and GI 70% specified in NY525-2021 "Organic Fertilizer". At the same time, the pH value (pH) of the obtained organic fertilizer is about 7.5, which is suitable for agricultural planting and can effectively improve the pH value of the soil.

[0031] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0032] Example 1

[0033] The gangue from a coal mine in Guangdong (water content 6.22%, ash content 78.37%, volatile matter 9.51%, organic carbon 13.27%) was selected, and the gangue was crushed and sieved into 5 mm materials for standby use. The gangue was then ball milled in a ball mill for 4 hours.

[0034] The preparation of seed liquid is to inoculate 4% of microbial fermentation agent into the culture medium, and culture it at 180 rpm for 24 hours at 30°C to obtain seed liquid with an effective viable count of ≥ 220 million CFU / mL. 3‰ of seed liquid is inoculated into a fermenter containing pretreated culture medium, and cultured aerobically at 30°C for 24 hours to obtain an inoculated agent for standby use. The preparation of the culture medium in the fermenter includes: crushing corn stalks through a 200-mesh sieve, mixing wheat bran, sawdust and corn stalk powder in a mixing ratio of 2:2:1, and adjusting the carbon-nitrogen ratio to 23:1-25:1 with livestock and poultry wastewater.

[0035] 50% by mass of wheat straw and cow dung are crushed and sieved to a particle size of ≤20 mm. The treated wheat straw and cow dung are fully mixed with 50% by mass of modified coal gangue to obtain compost fermentation materials. Inoculate the compost fermentation materials with an inoculation amount of the fermentation agent of 3‰ of the total mass of the mixed materials.

[0036] Solid composting main fermentation: fermentation cycle is 15-20 days, composting fermentation temperature is 45-70℃, 7-10 days are required for composting to be ≥55℃, turning over every two days, controlling moisture content to 50%-60%, carbon-nitrogen ratio (C / N) of the mixed material after stacking is: (20-30):1, and the main fermentation product is obtained.

[0037] Solid compost aging and fermentation: The temperature of the main fermentation product is stabilized at about 40°C, and the aging and fermentation is continued. The aging period is 15 to 30 days, the aging temperature is controlled at 40 to 45°C, and the compost is turned over every five days. The moisture content of the fermentation product after aging is 25% to 30%, and the carbon-nitrogen ratio (C / N) of the fermentation product after aging is ≤23:1.

[0038] During the composting process, the compost and ambient temperature were monitored three times a day (9:00, 14:00 and 18:00), and the average temperature was recorded. Compost samples were collected after 35 days, and the gangue organic fertilizer product was obtained by testing the compost 35 days later. The results were measured according to the index requirements in NY525-2021 "Organic Fertilizer".

[0039] Example 2

[0040] The difference between this embodiment and embodiment 1 is that the crushed and screened coal gangue is subjected to ultrasonic treatment. Specifically, the coal gangue is placed in an ultrasonic wave device with a sound energy density of 450W / L and an ultrasonic frequency of 20kHz for ultrasonic treatment for 4 hours. The rest of the operation method is the same as that of embodiment 1.

[0041] Example 3

[0042] The difference between this embodiment and embodiment 1 is that the coal gangue after crushing and screening is treated by soaking in hydrogen peroxide for oxidation, specifically, the coal gangue is mixed with 10% hydrogen peroxide at a mass volume ratio of 1g:5mL, the mixture is fully stirred and oxidized for 4h, washed with water until neutral, and dried at 60°C to a constant weight. The rest of the operation method is the same as that of embodiment 1.

[0043] Comparative Example 1

[0044] The difference between this embodiment and embodiment 1 is that the coal gangue after crushing and screening is not processed, and the rest of the operation method is the same as that of embodiment 1.

[0045] Table 1 Maturity results

[0046]

[0047] As a result, it is found from the results in Table 1 that the pH of the organic fertilizer obtained by using different modification treatment methods is between 7.19 and 7.89, and the conductivity meets the range required by organic fertilizer (i.e. ≤4ms / cm -1 ), the seed germination index (GI) is much greater than 70%, and the mass fraction of organic matter in the organic fertilizer (on a drying basis) is above 60%. The organic matter content in the organic fertilizer is reduced, which means that the higher the degree of decomposition, the more humus can be produced. Compared with Comparative Example 1, the modified activation treatment of coal gangue in Examples 1, 2, and 3 significantly improves the germination index of seeds, among which the compost product obtained by the coal gangue ball milling treatment group has the highest seed germination index, the highest degree of decomposition, and the best quality, which is more suitable for agricultural production.

[0048] Example 4

[0049] Coal gangue (water content 3.25%, ash content 67.46%, volatile matter 13.56%, organic carbon 21.68%) from a coal mine in Guangdong was selected, and the coal gangue was crushed and sieved into materials of different particle sizes for standby use. The coal gangue was then ball milled in a ball mill for 4 hours. The remaining operation methods were the same as those in Example 1.

[0050] As a result, it was found that the use of coal gangue with a particle size of 1 to 5 mm can not only provide organic components during the fermentation process, but also use its porosity to provide attachment sites for microorganisms, thereby promoting the maturity of the compost product. When the particles are smaller than 1 mm, the material is too fine to easily create an anaerobic environment, which is not conducive to the maturity of the compost. When the particles are larger than 5 mm, the material is too coarse to be conducive to heat preservation, resulting in low quality of the fermented product.

[0051] Example 5

[0052] Coal gangue (water content 3.56%, ash content 77.85%, volatile matter 14.10%, organic carbon 16.77%) from a coal mine in Guangdong was selected, and the coal gangue was crushed and sieved into 5 mm materials for standby use. The coal gangue was then ball milled in a ball mill for 2 hours. The remaining operation methods were the same as those in Example 1.

[0053] Example 6

[0054] Coal gangue (water content 3.69%, ash content 62.74%, volatile matter 15.48%, organic carbon 14.56%) from a coal mine in Guangdong was selected, and the coal gangue was crushed and sieved into 5 mm materials for standby use. The coal gangue was then ball milled in a ball mill for 4 hours. The remaining operation methods were the same as those in Example 1.

[0055] Example 7

[0056] Coal gangue (water content 3.65%, ash content 76.39%, volatile matter 13.02%, organic carbon 19.88%) from a coal mine in Guangdong was selected, and the coal gangue was crushed and sieved into 5 mm materials for standby use. The coal gangue was then ball milled in a ball mill for 6 hours. The remaining operation methods were the same as those in Example 1.

[0057] Example 8

[0058] Coal gangue (water content 4.17%, ash content 77.37%, volatile matter 11.22%, organic carbon 15.45%) from a coal mine in Guangdong was selected, and the coal gangue was crushed and sieved into 5 mm materials for standby use. The coal gangue was then ball milled in a ball mill for 8 hours. The remaining operation methods were the same as those in Example 1.

[0059] Table 2 Maturity results

[0060]

[0061] As a result, it can be seen from the results in Table 2 that after treating the gangue for different time periods, the pH value of the organic fertilizer obtained is between 7.09 and 7.35, and the conductivity meets the range required for organic fertilizer (i.e., ≤4ms / cm -1), the seed germination index (GI) is much greater than 70%, averaging 125%, and the mass fraction of organic matter in organic fertilizer (on a drying basis) is above 57%. After ball milling, the adsorption capacity and carrying capacity of gangue particles are improved. The compost product obtained by ball milling of gangue for 4 hours has the highest seed germination index, the highest degree of decomposition, and the best quality, which is more suitable for agricultural production.

[0062] Example 9

[0063] Coal gangue (water content 4.62%, ash content 81.90%, volatile matter 8.65%, organic carbon 12.86%) from a coal mine in Guangdong was selected, and the coal gangue was crushed and sieved into 5 mm materials for standby use. The coal gangue was subjected to ball milling for 4 hours for modification treatment. Except for the following grouping, which is different from Example 1, the rest of the operation method is the same as Example 1.

[0064] Table 3 Experimental groups

[0065]

[0066] Solid compost fermentation, collect compost samples after 50 days, test the compost 50 days later to obtain the gangue organic fertilizer product, and refer to the index requirements in NY525-2021 "Organic Fertilizer" for determination results.

[0067] Table 4 Maturity results

[0068]

[0069] As a result, it can be found from the results in Table 4 that the compost products with added microbial agents have a higher degree of maturity and better product quality than those without added microbial agents; the compost products with added coal gangue have a higher degree of maturity and better product quality than those without added microbial agents, and the degree of maturity is the highest. The compost products with both microbial agents and coal gangue added have the best quality.

[0070] Example 10

[0071] The difference between this embodiment and embodiment 1 is that nine treatment groups are set, namely a blank control group (CK) with 0% gangue addition, a treatment group (T1) with 3% gangue addition, a treatment group (T2) with 5% gangue addition, a treatment group (T3) with 8% gangue addition, a treatment group (T4) with 10% gangue addition, a treatment group (T5) with 20% gangue addition, a treatment group (T6) with 30% gangue addition, a treatment group (T7) with 40% gangue addition, and a treatment group (T8) with 50% gangue addition. The gangue is crushed and sieved into 5 mm materials for standby use, and the gangue is subjected to ball milling for 4 hours for modification. Preparation of seed liquid, inoculate 4% of microbial fermentation agent into the culture medium, shake and culture at 180 rpm for 24 hours at 30°C to obtain seed liquid, and the effective viable count is ≥ 220 million CFU / mL. Inoculate 3‰ of seed liquid into a fermenter containing pretreated culture medium, aerobically culture for 24 hours at 30°C to obtain an inoculated agent for standby use. The preparation of the culture medium in the fermenter includes: crushing corn stalks through a 200-mesh sieve, mixing wheat bran, sawdust and corn stalk powder in a mixing ratio of 2:2:1, and adjusting the carbon-nitrogen ratio to 20:1-25:1 with livestock and poultry wastewater. Crush and sieve wheat straw, cow dung, and sawdust to a particle size of ≤20mm. Mix the crushed and sieved wheat straw, cow dung, and sawdust with the aforementioned different amounts of coal gangue, make up to a mass fraction of 100%, fully stir and mix evenly, and obtain compost fermentation materials. Inoculate the composting fermentation material with inoculated bacteria, and the inoculation amount of the fermentation bacteria is 3‰ of the total mass of the mixed material.

[0072] Solid compost fermentation, collect compost samples after 42 days, test the compost 42 days to obtain the gangue organic fertilizer product, and refer to the indicator requirements in NY525-2021 "Organic Fertilizer" for determination results.

[0073] Table 5 Maturity results

[0074]

[0075] As a result, it can be found from the results in Table 5 that when 40% of coal gangue is added, the compost product obtained has the highest degree of maturity and the best quality, and the germination index can reach 152.58%, far exceeding the 70% stipulated in NY525-2021 "Organic Fertilizer".

[0076] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A coal gangue organic fertilizer, characterized in that: The invention comprises the following raw materials in mass fractions: 3-50% of coal gangue and 50-97% of agricultural and forestry wastes, and also comprises 2-6‰ of microbial fermentation agent of the total mass of the raw materials; the coal gangue is modified coal gangue, and the modification method is any one of ball milling, oxidation treatment and ultrasonic treatment.

2. The coal gangue organic fertilizer according to claim 1, characterized in that The particle size of the coal gangue is 1 to 5 mm.

3. The coal gangue organic fertilizer according to claim 1, characterized in that, The ball milling time is 2 to 8 hours.

4. The coal gangue organic fertilizer according to claim 1, characterized in that The oxidation treatment includes soaking the coal gangue with an oxidant for 2 to 8 hours.

5. The coal gangue organic fertilizer according to claim 1, characterized in that, The ultrasound is to directly ultrasound the coal gangue for 2 to 8 hours, with a sound energy density of 100 to 1200 W / L and an ultrasonic frequency of 20 kHz.

6. The coal gangue organic fertilizer according to claim 1, characterized in that, The microbial fermentation agent includes Bacillus subtilis and Bacillus licheniformis.

7. The coal gangue organic fertilizer according to claim 1, characterized in that, The agricultural and forestry wastes include any one or more of livestock and poultry manure, crop straw, wood chips and branches and leaves.

8. The method for preparing the gangue organic fertilizer according to any one of claims 1 to 7, characterized in that: The agricultural and forestry waste is crushed and screened, and the coal gangue is modified by ball milling, oxidation treatment or ultrasonic treatment; the screened agricultural and forestry waste is mixed with the modified coal gangue, and the microbial fermentation agent is added to perform composting fermentation; the composting fermentation is performed at 45-70°C for main fermentation for 15-20 days, and at 40-45°C for aging fermentation for 15-30 days.

9. The preparation method according to claim 8, characterized in that: The particle size of the agricultural and forestry waste after screening is ≤20mm.

10. The preparation method according to claim 8, characterized in that: During the fermentation, the material temperature is kept above 55° C. for 7 to 10 days.

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