Method for producing bio-organic fertilizer by using production solid waste and agricultural solid waste

Abstract

The invention relates to a method for producing a bio-organic fertilizer by using production solid waste and agricultural solid waste and application of the bio-organic fertilizer in agricultural planting, flower and plant cultivation and environmental protection, and belongs to the field of agriculture and ecological protection. Fermentation liquid residues generated by a lactic acid fermentation system in the production process of a lactic acid production enterprise, sludge residues generated by a sewage treatment system and crop straws are used as raw materials, and strains are added for composting fermentation to obtain the bio-organic fertilizer. The production efficiency and quality of the bio-organic fertilizer can be improved, comprehensive utilization of production solid waste can be promoted, the environmental influence is effectively reduced, resource circulation and environmental protection are achieved, and agricultural sustainable development is promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for producing bio-organic fertilizer using production solid waste and agricultural solid waste, and its application in agricultural planting, flower and plant cultivation and environmental protection, belonging to the field of agriculture and ecological protection. BACKGROUND

[0002] In agricultural production, bio-organic fertilizer is widely used in soil improvement and crop growth. The existing technology mainly uses organic waste (such as crop straw, livestock and poultry manure, kitchen waste, etc.) to convert into bio-organic fertilizer through a specific fermentation process. The fermentation process usually adopts anaerobic or aerobic fermentation, which utilizes the decomposition of microorganisms to convert organic matter into nutrients that can be absorbed by plants.

[0003] Common bio-organic fertilizer production structures include fermentation tanks, stirring equipment, temperature control systems, and aeration systems, etc. Temperature sensors and oxygen sensors are usually installed inside the fermentation tank to monitor and adjust the fermentation conditions. The principle of fermentation is mainly through the decomposition of microorganisms (such as bacteria, fungi, etc.) to organic matter, releasing nitrogen, phosphorus, potassium and other nutrients required by plants, while improving the physical and chemical properties of the soil.

[0004] Although the existing bio-organic fertilizer production technology has achieved certain success in agriculture, there are still some problems and shortcomings: 1) Low fermentation efficiency: In the traditional fermentation process, due to the large variety of microorganisms and the large changes in environmental conditions, the fermentation efficiency is often not high, and the production time is long. This is mainly because the temperature, humidity and oxygen content in the fermentation tank are difficult to maintain in the optimal range, thereby affecting the activity and reproduction rate of microorganisms. 2) Nutrient composition is not uniform: The existing technology in the raw material mixing and fermentation process is prone to uneven distribution of nutrient composition, affecting the quality of the final fertilizer. This problem is mainly due to the different characteristics of raw materials (such as carbon-nitrogen ratio, water content, etc.) and uneven stirring in the fermentation process. 3) Odor and pollution problems: During the fermentation process, especially anaerobic fermentation, it is easy to produce odor and harmful gases, increasing the risk of environmental pollution. In addition, if not properly handled, it may lead to the discharge of fermentation waste liquid and secondary pollution of soil and water. 4) High equipment investment cost: The existing bio-organic fertilizer production equipment usually requires a large investment, especially involving complex control systems and large-scale fermentation facilities, which poses an economic pressure on small farms and small-scale producers.

[0005] The present application aims to use production solid waste and agricultural solid waste to make bio-organic fertilizer, in order to solve the problems of low fermentation efficiency, high equipment investment cost and comprehensive utilization of fermentation solid waste in the existing technology. SUMMARY

[0006] In order to solve the above technical problems, the present application uses the fermentation liquid residue generated by the lactic acid fermentation system in the production process of the lactic acid production enterprise, the sludge residue generated by the sewage treatment system and the crop straw as raw materials, and obtains the bio-organic fertilizer through the addition of the strain composting fermentation.

[0007] One of the technical solutions provided by the present application is a method for producing organic fertilizer, which uses solid residues of a lactic acid fermentation system, sludge residues of a sewage treatment system and straw as fermentation raw materials, and is prepared through composite microbial strain fermentation; Further, the solid residue of the lactic acid fermentation system is a solid residue generated after the solid-liquid separation of the lactic acid fermentation liquid; the water content of the solid residue is less than 65%, preferably the water content is less than 60%; Further, the lactic acid fermentation liquid is subjected to inactivation of the bacterial cells and enzymes before being subjected to solid-liquid separation; Preferably, the solid-liquid separation means is plate and frame filtration; Further, the sludge residue of the sewage treatment system is a solid residue obtained after the lactic acid fermentation wastewater is treated by the sewage treatment system; in the solid residue of the sewage treatment system, the nitrogen content is 3.0%-6.0%, the phosphorus content is 2.5%-5.0%, the potassium content is 0.8%-1.5%, and the water content is 30%-45%, wherein the above "%" is the weight percentage of each component in the dry sludge; Further, the straw includes but is not limited to wheat straw and corn straw; Further, the fermentation raw materials are compounded in the following weight ratio: 0.5-2 of the solid residue of the lactic acid fermentation system, 0.5-2 of the sludge residue of the sewage treatment system and 3-5 of the straw; Further, the addition amount of the composite microbial strain is 0.1-0.4‰ (w / w) of the total weight of the fermentation raw materials; Further, the composite microbial strain includes Lactococcus lactis, Bacillus subtilis, Bacillus megaterium and Azotobacter chroococcum; Further, the composite microbial strain is compounded in the following viable bacterial number ratio: 40-50 of Lactococcus lactis, 25-30 of Bacillus subtilis, 15-20 of Bacillus megaterium and 10-12 of Azotobacter chroococcum; Preferably, the Lactococcus lactis has the strain number ATCC19435; Preferably, the Bacillus subtilis has the strain number CGMCC No.1.3358; Preferably, the Bacillus megaterium has the strain number CICC 23692; Preferably, the Azotobacter chroococcum has the strain number CGMCC No.1.142; Further, the fermentation conditions of the complex microbial strain are as follows: the complex microbial strain is added at 0.1-0.4 ‰ (w / w) of the total mass of the fermentation raw material, mixed uniformly, covered with a nano membrane for fermentation, and after 15-20 days of fermentation, the temperature in the material is reduced to below 50 DEG C, and the organic fertilizer fermentation is completed; Further, water is sprayed during the mixing of the raw material and the strain, and the total weight of the mixed material is 5-20% (w / w). Further, during the nano membrane covered fermentation, the moisture is controlled to be above 65%, and the fermentation temperature is not more than 65 DEG C. Further, during the nano membrane covered fermentation, the water is supplemented by opening the spraying machine at regular intervals, and the moisture is controlled to be above 65%. Further, after the fermentation is completed, granulation and packaging are performed, and the biological organic fertilizer is obtained.

[0008] The second technical solution of the present application is an organic fertilizer prepared by the method of the first technical solution.

[0009] Beneficial effects: 1. The present application provides a method for producing biological organic fertilizer from production solid waste and agricultural solid waste, which is simple and convenient to operate, high in production efficiency, environmentally friendly, and promotes sustainable agricultural development.

[0010] 2. The prior art equipment has high investment cost, and the current biological organic fertilizer production equipment usually needs large initial investment, which limits the participation of small-scale producers. The nano membrane covered fermentation scheme provided by the present application has small investment, simple production, and convenient operation, so that small farms and individual farmers can also produce biological organic fertilizer at a lower cost.

[0011] 3. Jindan Technology is a fermentation enterprise, but there are limitations in the use of production solid waste, and the resource value of solid waste cannot be fully utilized, and with the increase of production capacity, the environmental pressure is increasing. The present application develops a complete solid waste treatment and utilization system, promotes the comprehensive utilization of production solid waste, realizes the recycling of resources and environmental protection.

[0012] By solving the above technical problems, the present application can not only improve the production efficiency and quality of biological organic fertilizer, but also effectively reduce the environmental impact and promote sustainable agricultural development. BRIEF DESCRIPTION OF DRAWINGS Figure 1 The process flowchart of the present application DETAILED DESCRIPTION The present application is described below by specific embodiments. The technical means not specifically described in the present application are methods known to those skilled in the art. In addition, the embodiments are understood to be illustrative, rather than limiting the scope of the present application, the essence and scope of the present application are limited only by the claims. For those skilled in the art, various changes or modifications to the ingredients and amounts of the materials in these embodiments without departing from the essence and scope of the present application also fall within the protection scope of the present application.

[0013] The solid residue of the lactic acid fermentation system used in the preparation of the organic fertilizer of the present application is a solid residue with a water content of less than 65% obtained by inactivating the bacterial cells and enzymes of the lactic acid fermentation liquid and then performing solid-liquid separation. The skilled person can use common separation means in the art, such as filtration, pressure filtration, centrifugation, etc., to ensure that the water content in the solid residue is less than 65% and it can be used for the preparation of the organic fertilizer of the present application.

[0014] The sludge residue of the sewage treatment system used in the preparation of the organic fertilizer of the present application is sludge obtained by sewage treatment and separation of lactic acid fermentation wastewater. The nitrogen content in the sludge is 3.0%-6.0%, the phosphorus content is 2.5%-5.0%, the potassium content is 0.8%-1.5%, and the water content is 30%-45%. The above "% " refers to the weight percentage (w / w) of each component in the dry sludge. The skilled person can use common treatment and separation means in the art, such as AAO biological treatment system, plate and frame pressure filtration, etc., to ensure that the nitrogen content in the obtained sludge is 3.0%-6.0%, the phosphorus content is 2.5%-5.0%, the potassium content is 0.8%-1.5%, and the water content is 30%-45%, and it can be used for the preparation of the organic fertilizer of the present application.

[0015] In some embodiments of the present application, a method for preparing the solid residue of the lactic acid fermentation system is provided, which is specifically as follows: 1. Raw material pretreatment (1) Corn crushing: corn kernels are crushed to 40-60 mesh to increase the exposure area of starch; during the corn crushing process, water is added according to a dry starch: water mass ratio of 1:2-2.5; (2) Liquefaction: α-amylase is added at 0.5-1.0 L / ton of dry starch, the pH is adjusted to 6.0-6.5, and the temperature is adjusted to 85-90°C for 90-120 min of liquefaction until the DE value is 12-18%; Further, the pH is adjusted by adding 0.1-0.2% (w / w) of CaCl2; (3) Saccharification: Add saccharifying enzyme at 1.0-1.5 L / ton of dry starch, adjust the pH to 4.2-4.5, and saccharify at 60-62℃ for 24-48 h until the glucose concentration is ≥30% (w / v) and the light transmittance is >90% to obtain the saccharified solution; 2. Lactic acid fermentation Inoculate the saccharification solution with 5-10% (v / v) of Lactococcus lactis (ATCC19435) seed culture (seed culture OD). 600 (1.8-2.2) The fermentation process is as follows: temperature 42±1℃, pH 5.8-6.2, dissolved oxygen (DO) ≤0.1 ppm, stirring speed 100-150rpm, fermentation time 48-72 h; the fermentation endpoint is residual sugar ≤0.5% (w / v), and the fermentation is stopped when the lactic acid concentration reaches 12-15% (w / v). During fermentation, pH stability is maintained by adding CaCO3 suspension (concentration 20-30%).

[0016] 3. Fermentation broth pretreatment (before plate and frame filtration) Inactivation and demulsification: Heat the fermentation broth to 85-90℃ and maintain for 20 minutes to inactivate the bacteria and enzymes.

[0017] 4. Plate and frame filter press process (core byproduct: plate and frame filter residue) (1) Filtering preparation Filter cloth selection: Polypropylene (PP) material, pore size 5-10 μm.

[0018] Pre-coating: Diatomaceous earth (2-3 mm thick) to improve filtration efficiency.

[0019] (2) Feed control Feed solids content: 8-12% (w / v), dilution is required if too high; feed pressure: 0.2-0.6 MPa, with step-up pressure to prevent filter cloth clogging; feed temperature: 60-70℃ to reduce viscosity and increase flow rate; (3) Filtration cycle Pressurization phase: Hold at 0.6 MPa for 30-60 min; Drying stage: Backflushing with compressed air (0.8 MPa) for 10-15 min to reduce the moisture content of the slag; Slag discharge standards: Composition of plate and frame residue: microbial protein (30-40%), residual CaSO4, undegraded polysaccharides, and pigments; Moisture content: ≤65%, preferably below 60%.

[0020] In some embodiments of the present invention, a method for preparing sludge residue from a wastewater treatment system is provided, as detailed below: 1. pH adjustment Lactic acid fermentation wastewater is usually acidic (pH 3.0 - 5.0), which will inhibit microbial activity if directly entering the biological treatment system. Alkaline agent (lime milk Ca(OH)2) is added to neutralize it to near neutral (pH 6.5 - 7.5 (optimal 6.8 - 7.2)).

[0021] 2. AAO biological treatment system The pH-adjusted fermentation wastewater is introduced into the AAO biological treatment system to degrade organic pollutants (COD, BOD), nitrogen (ammonia nitrogen, organic nitrogen), and phosphorus in the wastewater using microorganisms (activated sludge). The standard for discharging treated wastewater is COD≤100 mg / L, pH 6.00-9.00, ammonia nitrogen 15 mg / l or less, and total phosphorus 1.0 mg / L or less. Finally, AAO-treated sludge is obtained. 3. Sludge concentration The water content of the sludge obtained from the AAO biological treatment system is controlled at 95%-97%; Further, the sludge is first separated from water in the secondary sedimentation tank to reduce the water content in the sludge to 99.2%-99.5%; then the sludge is introduced into the gravity concentration tank to reduce the water content to 95%-97%; 4. Sludge conditioning (chemical conditioning) To destroy the colloidal structure of the sludge, release bound water, improve the dewatering performance of the sludge (reduce specific resistance), make it more suitable for plate and frame filter pressing, obtain a filter cake (plate and frame residue) with lower water content, and improve the filter pressing efficiency, lime slurry is first added to the concentrated sludge and mixed thoroughly; CPAM (cationic polyacrylamide) solution is added and slowly mixed to form large flocs; after a short period of standing (maturation) of about 5-20 minutes, the sludge is pumped into the feed inlet of the plate and frame filter press; Further, the lime dosage is 10% - 25% (w / w) of the dry sludge weight, until the sludge pH rises to 11.0-12.5; Further, the lime is added and mixed rapidly and intensively for 1-2 minutes to ensure complete reaction; Further, the CPAM dosage is 0.1% - 0.5% (w / w) of the dry sludge weight; the addition point should be after the lime; Further, the CPAM is added and mixed slowly and gently for 1-3 minutes to avoid breaking the formed flocs; low-speed stirring or static mixers are usually used.

[0022] 5. Plate and frame filter pressing By high-pressure extrusion, the water in the sludge is discharged through the filter cloth to form a solid filter cake with a water content of 30%-45%, i.e. plate and frame residue.

[0023] Further, the plate-frame filter parameters are as follows: Feed pressure: 0.6-0.8 Mpa; feed time: 30-90 minutes; pressing pressure: 1.2-1.5 Mpa; pressing time: 15-30 minutes; blowing pressure: 0.6-0.8 Mpa; blowing time: 10-20 minutes; filter cake thickness: 25-35 mm; filter cake moisture content target: 30%-45%; Filter cycle time: including feeding, pressing, blowing, unloading, and plate combining, usually 1.5-3.5 hours / cycle.

[0024] The final obtained sludge contains 3.0%-6.0% of nitrogen, 2.5%-5.0% of phosphorus, 0.8%-1.5% of potassium, and 30%-45% of moisture content (the above "%" refers to the weight percentage of each component in dry sludge).

[0025] The strain used in the fermentation preparation of the organic fertilizer according to the embodiments of the present application is as follows: Lactococcus lactis, strain number ATCC19435; Bacillus subtilis, strain number CGMCC No.1.3358; Bacillus megaterium, strain number CICC 23692; Azotobacter chroococcum, strain number CGMCC No.1.142.

[0026] The present application is further explained and described through specific embodiments.

[0027] Example 1 Preparation of fermentation liquid solid residue of lactic acid fermentation system 1. Raw material pretreatment (1) Corn crushing: corn kernels are crushed to 40-60 mesh to increase the starch exposure area; during the corn crushing process, water is added according to a dry starch: water mass ratio of 1:2.

[0028] (2) Liquefaction: α-amylase is added at 1.0 L / ton of dry starch, the pH is adjusted to 6.4 by adding 0.1% CaCl2, and the temperature is 85-90℃ for 95 min of liquefaction until the DE value is 12.5%; (3) Saccharification: Saccharifying enzyme is added at 1.5 L / ton of dry starch, the pH is adjusted to 4.2-4.5, and the temperature is 60℃ for 40 h of saccharification until the glucose concentration is ≥30% (w / v) and the transmittance is >90%, obtaining a saccharification liquid; 2. Lactic acid fermentation Inoculate the saccharification solution with 5% (v / v) of Lactococcus lactis ATCC19435 seed culture (seed culture OD). 600 =1.9). The preparation method of lactic acid bacteria seed culture is as follows: A single colony is picked up using a sterile inoculation loop and streaked onto an MRS solid agar slant. The slant is incubated in a 30℃ incubator for 20 hours. Then, it is inoculated into an Erlenmeyer flask containing an appropriate amount of sterile MRS broth. When the target growth state (OD) is reached... 600 When the concentration reaches 1.9, the seed liquid can be harvested.

[0029] The fermentation process is as follows: temperature 42±1℃, add 25% CaCO3 suspension to maintain pH 5.8-6.2, dissolved oxygen (DO) ≤0.1 ppm, stirring speed 100-150 rpm, fermentation time 50 h; the fermentation endpoint index is residual sugar ≤0.5% (w / v), and the fermentation is discharged when the lactic acid concentration reaches 14% (w / v).

[0030] 3. Fermentation broth pretreatment (before plate and frame filtration) Inactivation and demulsification: The fermentation broth was heated to 88°C and maintained for 20 minutes to inactivate the bacteria and enzymes.

[0031] 4. Fermentation broth plate and frame filter press process (core byproduct: plate and frame residue) (1) Filtering preparation Filter cloth selection: Polypropylene (PP) material, pore size 10 μm.

[0032] Pre-coating: Diatomaceous earth (2-3 mm thick) to improve filtration efficiency.

[0033] (2) Feed control Feed solids content: 10% (w / v), if too high, dilution is required; feed pressure: 0.2-0.6 MPa stepped pressure increase to prevent filter cloth clogging; feed temperature: 65℃ to reduce viscosity and increase flow rate; (3) Filtration cycle Pressurization phase: Hold pressure at 0.6 MPa for 50 min; Drying stage: Compressed air (0.8 MPa) is used for backflushing for 10 minutes to reduce the moisture content of the slag; Slag discharge standards: Composition of plate and frame residue: microbial protein (35%), residual CaSO4, undegraded polysaccharides, and pigments; Moisture content: 58%.

[0034] Example 2: Preparation method of sludge plate and frame residue for sewage treatment system 1. pH adjustment Lactic acid fermentation wastewater is neutralized to pH 6.8-7.2 by adding an alkaline agent (lime milk Ca(OH)2). 2. AAO biological treatment system The pH-adjusted fermentation wastewater is introduced into the AAO biological treatment system to degrade organic pollutants (COD, BOD), nitrogen (ammonia nitrogen, organic nitrogen), and phosphorus in the wastewater using microorganisms (activated sludge). The treated wastewater is discharged with a standard of COD≤100 mg / L, pH 6.00-9.00, ammonia nitrogen 15 mg / L or less, and total phosphorus 1.0 mg / L or less. AAO-treated sludge is obtained. 3. Sludge concentration The sludge obtained from the AAO biological treatment system is first separated from water in a secondary sedimentation tank to reduce the water content in the sludge to 99.2%-99.5%. Then the sludge is introduced into a gravity thickener to reduce the water content to 95.5%. 4. Sludge conditioning (chemical conditioning) First, lime slurry is added to the concentrated sludge, with the lime dosage accounting for 10% of the dry sludge weight, until the sludge pH rises to 11.0. After adding lime, rapid and strong mixing is performed for 2 minutes to ensure complete reaction. Then CPAM is added, with the CPAM dosage accounting for 0.1% of the dry sludge weight. After adding CPAM, slow and low-speed stirring is performed for 2 minutes to avoid breaking the formed flocs. After 10 minutes of standing (maturation), the sludge is pumped into the feed inlet of a plate-and-frame filter press.

[0035] 5. Plate-and-frame filter pressing Through high-pressure extrusion, the water in the sludge is discharged through the filter cloth, forming a solid filter cake with a water content of 35%, i.e., plate-and-frame residue.

[0036] The plate-and-frame filter pressing parameters are as follows: Feed pressure: 0.65 Mpa; feed time: 50 minutes; pressing pressure: 1.2 Mpa; pressing time: 30 minutes; blow-off pressure: 0.65 Mpa; blow-off time: 20 minutes; filter cake thickness: 25 mm; target filter cake water content: 35%; filter pressing cycle time: 2 hours / cycle.

[0037] The final sludge residue obtained after plate-and-frame filter pressing has a nitrogen content of 3.0%, a phosphorus content of 3.0%, a potassium content of 0.8%, and a water content of 35%.

[0038] Example 3: Optimization of fermentation strains 1. Mix 4 tons of wheat straw, 1 ton of lactic acid fermentation solid residue (prepared in Example 1), and 1 ton of sludge residue (prepared in Example 2) in a ratio of 4:1:1, mix uniformly using a turnover machine, and spray 1 ton of water using a spraying machine during the turnover process. 2. Divide the uniformly mixed material into five equal parts, and add Lactococcus lactis, Bacillus subtilis, Bacillus megaterium, Azotobacter chroococcus, and a compound microbial strain (Lactococcus lactis: Bacillus subtilis: Bacillus megaterium: Azotobacter chroococcus = 47:27:17:11 (live count ratio)) at a ratio of 0.15‰ respectively; all the above strains are added in the form of freeze-dried powder; 3. Cover all the mixed materials with a nano-membrane for fermentation, and turn on the sprayer regularly to add water, keeping the moisture content above 65% and the fermentation temperature below 65℃. 4. After 18 days of fermentation, the fermentation of organic fertilizer ends when the temperature inside the material drops below 50℃.

[0039] 5. Five samples of materials were taken and tested respectively. The test results are shown in Table 1 below.

[0040] Table 1. Fermentation test data of the strain (NY 884-2012 standard control) and fermentation effect verification data.

[0041] As shown in Table 1, the compound microbial inoculant was the optimal choice in this experiment. It met all the basic indicators and demonstrated significant advantages in total nutrients, germination index, and effective viable bacteria count. This proves that in organic fertilizer fermentation, the strategy of using multiple microbial strains for inoculation is far more efficient and reliable than using a single strain. The complementary functions of the compound microorganisms form a symbiotic chain, maximizing the utilization of the fermentation substrate and jointly resisting adverse environments, thereby maximizing the effect.

[0042] Example 4 Optimization of Fermentation Raw Materials 1. The control group used 100% wheat straw (6 tons); 2. Treatment group 1 used wheat straw: lactic acid fermentation solid residue (prepared in Example 1) at a ratio of 70%:30%; 3. Treatment group 2 used wheat straw: sludge residue (prepared in Example 1) at a ratio of 70%:30%; 4. The treatment group used wheat straw: lactic acid fermentation solid residue: sludge residue in a ratio of 70%: 15%: 15%; 5. Add 0.15‰ of compound microbial strain (Lactococcus lactis: Bacillus subtilis: Bacillus megaterium: Azotobacter chrysophyte = 46:25:15:10 (live count ratio)) to each of the above four groups (same as Table 2), mix them evenly using a turning machine, and spray 1 ton of water using a sprayer during the turning process; 6. Cover the mixed materials with a nano-membrane for fermentation. According to the moisture requirements of organic fertilizer, turn on the sprayer regularly to replenish water, keep the moisture content above 65% and the fermentation temperature below 65℃. 4. After 16 days of fermentation, when the temperature in the material drops below 50°C, the fermentation of the organic fertilizer is completed.

[0043] 5. The four groups of materials were sampled and detected according to the standard of NY 884-2012, and the detection results are as shown in Table 3.

[0044] Table 2 Test grouping (dry matter ratio)

[0045] Table 3 Black preservation mixed fermentation basic percentage (product detection data (NY 884-2012 standard comparison)

[0046] From the above data, the organic matter content of all groups meets the standard, but it gradually decreases from the control group to the treatment group 3. The main reason is that the organic matter content of wheat straw is high, while the organic matter content of added lactic acid fermentation residue or sludge residue is low. With the increase of the proportion, the dilution effect is obvious. The organic matter content of treatment group 3 is moderate, which is more conducive to decomposition and safety. The total nutrient of the control group is insufficient, and the treatment groups all meet the standard, with the highest in treatment group 3. The nutrient of wheat straw itself is low, the lactic acid residue contains high nitrogen, phosphorus and potassium, and the sludge residue is rich in nutrient salt. The two are complementary, and the total nutrient is improved by the promotion of microorganisms. The germination index of the control group does not meet the standard, and the treatment groups are significantly improved, with the best in treatment group 3. The straw is easy to produce toxic substances such as ammonia and organic acid during fermentation. After adding the residue, the lactic acid residue can reduce the pH and reduce ammonia volatilization, and the sludge residue can adsorb harmful substances and buffer toxicity. The two further improve the safety. The cadmium content of all groups meets the standard, but the treatment groups are higher than the control group. The sludge residue may introduce cadmium, and the content of treatment group 2 (30% sludge) is the highest. The cadmium content of treatment group 3 is lower than that of treatment group 2 due to the dilution of lactic acid residue or the adsorption of microorganisms. The viable bacterial count of all groups meets the standard, and the treatment groups are higher than the control group, with the highest in treatment group 3. The addition of residue provides more balanced nutrition for microorganisms, the lactic acid residue promotes the growth of bacterial flora, and the sludge residue may slightly inhibit it. However, the mixed use of the two creates a suitable environment and enhances the synergistic proliferation of bacterial flora.

[0047] Example 5 A method for preparing an organic fertilizer 1. Mix 5 tons of corn straw, 2 tons of fermentation plate frame slag (prepared in example 1), and 2 tons of fermentation sludge plate frame slag (prepared in example 2) according to the mass ratio of 5:2:2, and mix them evenly with a turning machine; 2. Add compound microbial strains (lactococcus lactis: bacillus subtilis: bacillus megaterium: azotobacter chroococcum = 45:28:15:10 (proportion of viable bacterial count)) according to the proportion of 0.2‰ of the total raw material weight, mix them evenly using a turning machine, and spray 1 ton of water using a spraying machine during the turning process. 3. Cover the well-mixed organic fertilizer with a nano-membrane for fermentation (control the temperature not to exceed 65℃). According to the water requirements of the organic fertilizer (control the water content to be above 65% during fermentation), turn on the sprinkler to add water at regular intervals. 4. After 15 days of fermentation, the fermentation of organic fertilizer ends when the temperature inside the material drops below 50℃.

[0048] 5. The test results are shown in Table 4. All indicators meet the requirements of the (NY 884-2012) standard. Finally, the product is granulated and packaged to obtain bio-organic fertilizer.

[0049] Table 4

[0050] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various changes, modifications, substitutions and variations in form and detail to these embodiments without departing from the spirit and principles of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for producing organic fertilizer, characterized in that, The method uses solid residue from a lactic acid fermentation system, sludge residue from a wastewater treatment system, and straw as fermentation raw materials, and obtains the product through fermentation with compound microbial strains. The solid residue of the lactic acid fermentation system is the solid residue generated after solid-liquid separation of the lactic acid fermentation broth. The sludge residue of the wastewater treatment system is the solid residue obtained after treating lactic acid fermentation wastewater through the wastewater treatment system. The composite microbial strains include: Lactococcus lactis, Bacillus subtilis, Bacillus megaterium, and Azotobacter chrysophyte.

2. The method for producing organic fertilizer as described in claim 1, characterized in that, The solid residue of the lactic acid fermentation system has a moisture content of less than 65%; the lactic acid fermentation broth undergoes solid-liquid separation after inactivation of the bacteria and enzymes.

3. A method for producing organic fertilizer as described in claim 1, characterized in that, The solid residue of the wastewater treatment system contains nitrogen content of 3.0% - 6.0%, phosphorus content of 2.5% - 5.0%, potassium content of 0.8% - 1.5%, and moisture content of 30% - 45%.

4. The method for producing organic fertilizer as described in claim 1, characterized in that, The straw includes, but is not limited to: wheat straw and corn straw.

5. A method for producing organic fertilizer as described in claim 1, characterized in that, The fermentation raw materials are compounded in the following weight ratio: 0.5-2 parts solid residue from the lactic acid fermentation system, 0.5-2 parts sludge residue from the sewage treatment system, and 3-5 parts straw.

6. A method for producing organic fertilizer as described in claim 1, characterized in that, The amount of the compound microbial strain added is 0.1 to 0.4‰ of the total weight of the fermentation raw materials; The compound microbial strains are compounded according to the following ratio of live bacteria: Lactococcus lactis 40-50: Bacillus subtilis 25-30: Bacillus megaterium 15-20: Azotobacter chrysophagus 10-12.

7. A method for producing organic fertilizer as described in claim 6, characterized in that, The *Lactococcus lactis* strain number is ATCC19435; the *Bacillus subtilis* strain number is CGMCC No.1.3358; the *Bacillus megaterium* strain number is CICC 23692; and the *Azotobacter chrysophyte* strain number is CGMCC No.1.

142.

8. A method for producing organic fertilizer as described in claim 1, characterized in that, The fermentation conditions of the compound microbial strain are as follows: add compound microbial strain at 0.1~0.4‰ of the total mass of fermentation raw materials, mix evenly, cover with a nano-membrane for fermentation, and after 15~20 days of fermentation, when the temperature inside the material drops below 50℃, the organic fertilizer fermentation is completed.

9. A method for producing organic fertilizer as described in claim 8, characterized in that, During the mixing of raw materials and microbial strains, spray water at a concentration of 5-20% (w / w) of the total weight of the mixture; during fermentation covered by nanofilm, control the moisture content to be above 65% and the fermentation temperature to not exceed 65℃.

10. A bio-organic fertilizer prepared by the method according to any one of claims 1-9.

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