Method for preparing liquid organic fertilizer based on grinding-enzymatic hydrolysis combined process

Abstract

This invention discloses a method for preparing liquid organic fertilizer based on a combined grinding-enzymatic hydrolysis process, belonging to the field of liquid organic fertilizer preparation technology. The method includes: coarsely screening livestock manure to remove impurities, then mixing it evenly with water to obtain a mixed slurry; mechanically grinding the mixed slurry to obtain an activated slurry; adding a compound enzyme preparation to the activated slurry to obtain an enzymatically hydrolyzed material; heating the enzymatically hydrolyzed material to obtain a heat-shocked material; performing solid-liquid separation on the heat-shocked material to obtain a high-temperature filtrate and a filter residue; adding water-soluble nitrogen, phosphorus, potassium, humic acid, and trace elements to the cooled filtrate, and inoculating with a microbial agent to obtain the liquid organic fertilizer based on the combined grinding-enzymatic hydrolysis process. This invention promotes the conversion of macromolecular nutrients in manure into soluble small molecules through the combined grinding-enzymatic hydrolysis process, while the heat shock treatment simultaneously terminates enzyme activity, inactivates pathogens, and reduces viscosity. Subsequent inoculation with beneficial bacteria ensures long-term survival, resulting in a liquid organic fertilizer that combines rapid-acting nutrition with microecological conditioning functions.

Description

Technical Field

[0001] This invention relates to the field of liquid organic fertilizer preparation technology, and specifically to a method for preparing liquid organic fertilizer based on a combined grinding-enzymatic hydrolysis process. Background Technology

[0002] Livestock manure contains a large amount of undigested cellulose, hemicellulose, protein, and trace elements, making it a raw material for agricultural organic fertilizer. However, in practice, the nutrients in manure exist in complex macromolecular forms, resulting in a very slow decomposition and transformation process when directly applied to the soil. Crops struggle to obtain timely nutrient supply during their growth cycle. Furthermore, manure commonly carries pathogens and parasite eggs, posing a threat to crop safety and the soil ecosystem if not properly treated. Traditional composting methods require weeks to months, during which the material's state is difficult to control and often releases foul odors. Using a single biological enzyme treatment method results in low nutrient conversion efficiency due to the dense structure of the manure raw material and limited reaction interfaces. Additionally, the treated material requires further sterilization, leading to poor overall operational coordination and difficulty in ensuring consistent product performance. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing liquid organic fertilizer based on a combined grinding-enzymatic hydrolysis process, which solves the problems existing in the background technology.

[0004] To address the aforementioned technical problems, this invention provides a method for preparing liquid organic fertilizer based on a combined grinding-enzymatic hydrolysis process, comprising the following steps:

[0005] S1. After coarsely screening and removing impurities from poultry and livestock manure, mix it with water at a mass ratio of 1:1.5 to 1:2.5 to obtain a mixed slurry. Then, mechanically grind the mixed slurry to achieve a fineness of 100 to 120 mesh and adjust the pH of the system to 5.0 to 6.5 to obtain an activated slurry.

[0006] S2, a compound enzyme preparation is added to the activated slurry. The compound enzyme preparation consists of cellulase with an enzyme activity ≥100,000 U / g, β-glucanase with an enzyme activity ≥150,000 U / g, xylanase with an enzyme activity ≥500,000 U / g, pectinase with an enzyme activity ≥300,000 U / g, neutral protease with an enzyme activity ≥250,000 U / g, and α-amylase with an enzyme activity ≥300,000 U / g in a mass ratio of (2-4):(0.5-1.5):(0.5-1.5):(0.3-1):(1-2):(1-2). The mixture is enzymatically hydrolyzed at 50-60℃ and 150-300 rpm for 5-16 hours to obtain the hydrolyzed material. The amount of the compound enzyme preparation added is 0.5-2.0% of the total mass of the activated slurry.

[0007] S3, the enzymatically hydrolyzed material is heated to 90-100°C at a heating rate of 5-15°C / min and kept at a constant temperature for 15-25 minutes to obtain the heat-shocked material;

[0008] S4. The heat-treated material is subjected to solid-liquid separation under the condition of maintaining the temperature at 80-100℃, and high-temperature filtrate and filter residue are collected.

[0009] S5. Cool the high-temperature filtrate to below 35°C, add commercially available water-soluble nitrogen, phosphorus, and potassium sources, humic acid, and trace elements to the cooled filtrate, stir to dissolve, and then inoculate with an effective viable bacterial count of not less than 1.0 × 10⁻⁶. 8 By adjusting the pH of the system to 6.0–7.2 with EM bacterial agent at CFU / mL, a liquid organic fertilizer based on a grinding-enzymatic hydrolysis combined process can be obtained.

[0010] Preferably, in step S1, the coarse screening removes impurities with a particle size ≥ 5 mm.

[0011] Preferably, in step S1, the mechanical grinding is performed using a high-shear colloid mill for multi-stage grinding; the pH of the system is adjusted using an organic acid or a weak base.

[0012] Preferably, in step S2, the compound enzyme preparation is composed of cellulase, β-glucanase, xylanase, pectinase, neutral protease and α-amylase in a mass ratio of 3:1:1:0.5:1.5:1.5; the amount of compound enzyme preparation added is 1.0% of the total mass of the activated slurry.

[0013] Preferably, in step S3, the enzymatically hydrolyzed material is heated to 95°C at a heating rate of 8°C / min and kept at that temperature for 20 minutes.

[0014] Preferably, in step S4, solid-liquid separation is performed using a 100-120 mesh high-frequency vibrating screen.

[0015] Preferably, in step S5, the high-temperature filtrate is cooled by a heat exchanger; the effective viable count of the EM agent is not less than 1.0 × 10⁻⁶. 8 CFU / mL.

[0016] Preferably, in step S5, the water-soluble nitrogen source added to each liter of cooled filtrate is 20g of urea, the phosphorus and potassium source is 15g of potassium dihydrogen phosphate, the humic acid is 10g of potassium fulvate, and the trace element is 2g of EDTA chelated trace element; the inoculation amount of EM bacteria is 2% of the total volume of the cooled filtrate.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] By combining physical grinding with biochemical enzymatic hydrolysis, the contact area of ​​fibrous components in manure is effectively increased, allowing the compound enzymes to act more fully on macromolecules such as cellulose, hemicellulose, protein, and residual starch. This promotes the conversion of solid nutrients into soluble small molecules in the liquid phase, thereby increasing the content of readily available nutrients such as free amino acids and small sugars in the liquid, which is beneficial for the rapid absorption and utilization by crops.

[0019] After enzymatic hydrolysis, a high-temperature heat shock treatment is introduced. On the one hand, the residual enzyme activity is controlled to avoid irreversible degradation fluctuations in the product during storage. On the other hand, pathogenic bacteria and parasite eggs in the material are inactivated, improving the hygiene and safety of the product. The high temperature also reduces the viscosity of the polysaccharide-rich liquid, making the subsequent solid-liquid separation process smoother and improving the recovery efficiency of effective nutrients in the liquid phase.

[0020] High-temperature pretreatment eliminates competition from existing bacteria in the liquid fertilizer solution. Inoculation with beneficial microbial agents during the cooling phase allows the microbial community to maintain a longer survival period in a relatively pure liquid environment. The resulting liquid organic fertilizer combines fast-acting small-molecule nutrients with the conditioning function of live microorganisms. When applied to the soil, it quickly replenishes the nutrients needed by crops and helps improve the rhizosphere microecological environment. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] Example 1

[0023] The preparation method of liquid organic fertilizer based on the combined grinding-enzymatic hydrolysis process uses fresh pig manure as the raw material for poultry and livestock manure, with a moisture content of 60%. Coarse screening is performed using a 5mm sieve to remove straw fragments, sand, and plastic debris. The pig manure after impurity removal is mixed with deionized water at a mass ratio of 1:2 to obtain a mixed slurry. Mechanical grinding is carried out in three stages using a high-shear colloid mill, with the grinding speed controlled within the range of 2000-3000 rpm (2900 rpm in this example). The material is circulated 1-5 times (three times in this example), and all the ground material passes through a 100-mesh sieve. Citric acid is used to adjust the pH of the mixed slurry to 5.5, resulting in an activated slurry. In this activated slurry, the fiber bundles are cut, increasing the substrate area accessible to the enzyme, which is suitable for subsequent compound enzyme preparation.

[0024] The compound enzyme preparation uses cellulase, β-glucanase, xylanase, pectinase, neutral protease, and α-amylase from Xiasheng Industrial Group Co., Ltd., in a mass ratio of 3:1:1:0.5:1.5:1.5. This ratio is within the range of the individual enzyme group proportions. The total amount of the compound enzyme preparation added is 1.0% of the total mass of the activated slurry, which is within the range of 0.5% to 2.0%. After the activated slurry is heated to 55°C, the compound enzyme preparation is added. Under the conditions of an enzymatic hydrolysis temperature of 50-60°C (55°C in this example) and a rpm range of 150-300 rpm (200 rpm in this example), the enzymatic hydrolysis is carried out at a constant temperature for 10 hours, which is within the range of 5-16 hours, to obtain the enzymatically hydrolyzed material.

[0025] The role of this six-enzyme combination in this invention is not limited to the degradation of a single component, but rather to simultaneously break down cellulose, hemicellulose, pectin, protein and residual starch in poultry and livestock manure, thereby transferring solid-phase nutrients to the liquid phase. Compared with treatment methods using only cellulase or protease, this combination reduces local reaction stagnation caused by insufficient substrate exposure, and the content of soluble small molecules in the resulting liquid is more stable.

[0026] The enzymatically hydrolyzed material was heated to 95°C via a steam jacket at a heating rate of 8°C / min and held at that temperature for 20 min to obtain heat-shocked material. This heat shock treatment kept the residual enzyme activity at a low level, making it less likely for the material to continue decomposing during storage and causing viscosity fluctuations, while also reducing the residue of pathogens and parasite eggs. Solid-liquid separation was carried out using a 120-mesh high-frequency vibrating screen with a feed temperature of 85°C, and high-temperature filtrate and filter residue were collected. At this temperature, the polysaccharide system had a low viscosity, resulting in less screen clogging during the screening process and a higher liquid phase recovery rate.

[0027] The high-temperature filtrate was cooled to 30°C using a plate heat exchanger. 20g of urea, 15g of potassium dihydrogen phosphate, 10g of potassium humate, and 2g of EDTA-chelated trace elements were added sequentially to each liter of cooled filtrate, and stirred for 20 minutes until completely dissolved. The EM bacterial agent used had an effective viable count of 2.0 × 10⁻⁶ bacteria. 8 A commercially available microbial agent with a concentration of CFU / mL was used as an inoculum at a rate of 2% of the total volume of the cooled filtrate. After inoculation, the pH of the system was adjusted to 6.5 with potassium hydroxide, and then bottled to obtain liquid organic fertilizer. This liquid organic fertilizer combines the effects of organic small molecule nutrition and live bacteria conditioning, and is suitable for drip irrigation, fertigation, and seedling substrate replenishment.

[0028] Example 2

[0029] The preparation method of liquid organic fertilizer based on the combined grinding-enzymatic hydrolysis process uses dairy cow manure as livestock manure raw material. The coarse screening removes impurities with a particle size of not less than 5 mm. The dairy cow manure and water are mixed at a mass ratio of 1:1.5, mechanically ground to 100 mesh, and the pH of the system is adjusted to 5.0.

[0030] The compound enzyme preparation uses 2 parts cellulase, 0.5 parts β-glucanase, 0.5 parts xylanase, 0.3 parts pectinase, 1 part neutral protease, and 1 part α-amylase, with an addition amount of 0.8%. Enzymatic hydrolysis is carried out at 50℃ and 150rpm for 6 hours. The hydrolysate is heated to 90℃ at 5℃ / min and kept at that temperature for 15min. The heat-shocked material is then subjected to solid-liquid separation at 80℃. The high-temperature filtrate is cooled to 35℃ and then conventionally compounded, inoculated with EM bacteria, and the pH is adjusted to 6.0. This set of parameters is suitable for dairy manure systems with high initial fiber content and low fluidity. The low water content helps to reduce the volumetric load of the pretreatment. Even with a low enzyme dosage, a liquid product that can be directly applied can still be obtained.

[0031] Example 3

[0032] The preparation method of liquid organic fertilizer based on the combined grinding-enzymatic hydrolysis process uses broiler manure as the raw material of poultry and livestock manure. In this embodiment, mechanical grinding is carried out by multi-stage grinding with a high-shear colloid mill; broiler manure and water are mixed at a mass ratio of 1:2.5 and circulated four times with a high-shear colloid mill until the fineness of the material reaches 120 mesh; the pH of the system is adjusted by a weakly alkaline sodium bicarbonate solution to adjust the pH of the activated slurry to 6.5;

[0033] The compound enzyme preparation still consists of cellulase, β-glucanase, xylanase, pectinase, neutral protease, and α-amylase in a ratio of 3:1:1:0.5:1.5:1.5, with the addition amount controlled at 1.0% of the total mass of the activated slurry. Enzymatic hydrolysis is carried out at 60℃ and 300rpm for 16h. The hydrolyzed material is heated to 95℃ at 8℃ / min and kept at that temperature for 20min. This implementation method is suitable for chicken manure systems with high solid content and high nitrogen content. The use of weak alkali adjustment is beneficial to maintaining protease activity and material dispersion. Combined with high shear fineness, it can increase the release of soluble nitrogen into the liquid phase.

[0034] Example 4

[0035] The preparation method of liquid organic fertilizer based on the grinding-enzymatic hydrolysis combined process follows the aforementioned pulping, enzymatic hydrolysis and heat shock treatment steps, only adjusting the separation and post-treatment conditions. In this embodiment, solid-liquid separation is carried out using a 100-mesh high-frequency vibrating screen, and the high-temperature filtrate is cooled by a tubular heat exchanger; the heat-shocked material enters the 100-mesh high-frequency vibrating screen at 82°C, the filter residue on the screen is collected separately, and the high-temperature filtrate below the screen is cooled to 34°C by a tubular heat exchanger.

[0036] The EM agent used is a commercially available product with an effective viable count of 1.2 × 10^8 CFU / mL. After inoculation, the pH of the system is adjusted to 6.8. The 100-mesh sieve balances throughput and anti-clogging ability, making it suitable for continuous processing of liquids with medium solid load. The heat exchanger cooling can shorten the high-temperature residence time and reduce the loss of small molecule nutrients before subsequent viable inoculation.

[0037] Comparative Example 1

[0038] A method for preparing liquid organic fertilizer without mechanical grinding and deviating from core parameters and compound raw materials; Compared with Example 1, Comparative Example 1 omits the mechanical grinding step, and after coarse screening to remove impurities, pig manure and water are mixed at a mass ratio of 1:2, and the pH of the mixed slurry is directly adjusted to 5.5 with citric acid to obtain activated slurry;

[0039] Meanwhile, the amount of cellulase in the compound enzyme preparation was reduced to 1 part and the amount of neutral protease was reduced to 0.5 parts, deviating from the core ratio range. The enzymatic hydrolysis temperature was also reduced to 40℃, deviating from the core temperature range. Furthermore, no compound raw materials such as urea, potassium dihydrogen phosphate, potassium humate, and EDTA chelated trace elements were added to the filtrate after cooling, while the remaining steps remained the same. This comparative example is used to illustrate the effects of mechanical grinding, core enzyme ratio, and enzymatic hydrolysis conditions on substrate degradation, such as cellulose degradation rate and free amino acid release, as well as the necessity of subsequent compound nutrient elements for the overall product effect, such as seed germination index, thereby overcoming the isolation phenomenon.

[0040] Comparative Example 2

[0041] The liquid organic fertilizer preparation method without solid-liquid separation was not used; compared with Example 1, Comparative Example 2 only required that the material after heat shock treatment be naturally cooled to 25°C and then solid-liquid separation was performed using a 120-mesh high-frequency vibrating screen, while the other steps remained the same; this comparative example is used to illustrate the effect of high temperature and low viscosity conditions on screening efficiency and filtrate recovery rate.

[0042] Performance tests were performed on the samples obtained in Examples 1, 2, 3, and 4, as well as Comparative Examples 1 and 2. The cellulose degradation rate was determined by the difference in cellulose content between the raw material and the residue after enzymatic hydrolysis. Free amino acid nitrogen was determined by formaldehyde titration. The apparent viscosity of the liquid was determined by rotational viscometer at 25°C or the corresponding sieving temperature. The sieve penetration rate was calculated based on the mass of the sieved liquid and the total mass of the feed. Escherichia coli was detected by plate counting. The mortality rate of Ascaris eggs was statistically analyzed by microscopic examination. The number of viable EM bacteria was determined by nutrient agar culture counting. Each sample was tested in triplicate, and the average value was taken.

[0043] Each example and comparative example was prepared independently under the same batch of raw material conditions, with each batch of raw material weighing 50 kg. After enzymatic hydrolysis, samples were taken to determine the soluble index. After separation, the sieve penetration rate and apparent viscosity were determined. After filling, the samples were sealed and stored at 25°C for 6 months, and then the effective viable count and appearance stability of EM bacteria were determined. Pathogen indicators were detected within 24 hours after heat shock treatment.

[0044] Table 1 Performance test data of Examples 1-4 and Comparative Examples 1-2

[0045]

[0046] As shown in Table 1, the test data and comparative analysis reveal that both Example 1 and Example 3 achieved high cellulose degradation rates and high free amino acid nitrogen content, indicating that the combination of mechanical grinding and compound enzyme preparation can improve the conversion of macromolecular nutrients into the liquid phase. In Comparative Example 1, after mechanical grinding was removed, both the cellulose degradation rate and the sieve penetration rate decreased, indicating that when the enzyme relies solely on natural diffusion to contact the substrate, the substrate exposure is insufficient.

[0047] In Comparative Example 2, when solid-liquid separation was performed at 25°C, although the level of enzymatic hydrolysis in the first stage was close to that in Example 1, the apparent viscosity increased and the sieve penetration rate decreased, indicating that solid-liquid separation plays a practical role in maintaining continuous sieve separation and liquid phase recovery. No Escherichia coli was detected in any of the examples after heat shock treatment, and the mortality rate of Ascaris eggs was 100%, indicating that heat shock treatment has a stabilizing effect on hygiene indicators. After 6 months of storage, the EM bacteria in the sample of the examples still maintained a high number, indicating that inoculation with live bacteria after cooling and control of pH can balance product stability and microbial activity.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing liquid organic fertilizer based on a combined grinding-enzymatic hydrolysis process, characterized in that, Includes the following steps: S1. After coarsely screening and removing impurities from poultry and livestock manure, mix it with water at a mass ratio of 1:1.5 to 1:2.5 to obtain a mixed slurry. Then, mechanically grind the mixed slurry to achieve a fineness of 100 to 120 mesh and adjust the pH of the system to 5.0 to 6.5 to obtain an activated slurry. S2, a compound enzyme preparation is added to the activated slurry. The compound enzyme preparation consists of cellulase with an enzyme activity ≥100,000 U / g, β-glucanase with an enzyme activity ≥150,000 U / g, xylanase with an enzyme activity ≥500,000 U / g, pectinase with an enzyme activity ≥300,000 U / g, neutral protease with an enzyme activity ≥250,000 U / g, and α-amylase with an enzyme activity ≥300,000 U / g in a mass ratio of (2-4):(0.5-1.5):(0.5-1.5):(0.3-1):(1-2):(1-2). The mixture is enzymatically hydrolyzed at 50-60℃ and 150-300 rpm for 5-16 hours to obtain the hydrolyzed material. The amount of the compound enzyme preparation added is 0.5-2.0% of the total mass of the activated slurry. S3, the enzymatically hydrolyzed material is heated to 90-100°C at a heating rate of 5-15°C / min and kept at a constant temperature for 15-25 minutes to obtain the heat-shocked material; S4. The heat-treated material is subjected to solid-liquid separation under the condition of maintaining the temperature at 80-100℃, and high-temperature filtrate and filter residue are collected. S5. Cool the high-temperature filtrate to below 35°C, add commercially available water-soluble nitrogen, phosphorus, and potassium sources, humic acid, and trace elements to the cooled filtrate, stir to dissolve, and then inoculate with an effective viable bacterial count of not less than 1.0 × 10⁻⁶. 8 By adjusting the pH of the system to 6.0–7.2 with EM bacterial agent at CFU / mL, a liquid organic fertilizer based on a grinding-enzymatic hydrolysis combined process can be obtained.

2. The method for preparing liquid organic fertilizer based on a combined grinding-enzymatic hydrolysis process according to claim 1, characterized in that, In step S1, coarse screening removes impurities with a particle size ≥ 5 mm.

3. The method for preparing liquid organic fertilizer based on a combined grinding-enzymatic hydrolysis process according to claim 1, characterized in that, In step S1, mechanical grinding is performed using a high-shear colloid mill for multi-stage grinding; the pH of the system is adjusted using organic acid or weak base.

4. The method for preparing liquid organic fertilizer based on a combined grinding-enzymatic hydrolysis process according to claim 1, characterized in that, In step S2, the compound enzyme preparation is composed of cellulase, β-glucanase, xylanase, pectinase, neutral protease and α-amylase in a mass ratio of 3:1:1:0.5:1.5:1.5; the amount of compound enzyme preparation added is 1.0% of the total mass of the activated slurry.

5. The method for preparing liquid organic fertilizer based on a combined grinding-enzymatic hydrolysis process according to claim 1, characterized in that, In step S3, the enzymatically hydrolyzed material is heated to 95°C at a heating rate of 8°C / min and kept at that temperature for 20 minutes.

6. The method for preparing liquid organic fertilizer based on a combined grinding-enzymatic hydrolysis process according to claim 1, characterized in that, In step S4, solid-liquid separation is performed using a 100-120 mesh high-frequency vibrating screen.

7. The method for preparing liquid organic fertilizer based on a combined grinding-enzymatic hydrolysis process according to claim 1, characterized in that, In step S5, the high-temperature filtrate is cooled by a heat exchanger; the effective viable count of the EM agent is not less than 1.0 × 10⁻⁶. 8 CFU / mL.

8. The method for preparing liquid organic fertilizer based on a combined grinding-enzymatic hydrolysis process according to claim 1, characterized in that, In step S5, the water-soluble nitrogen source added to each liter of cooled filtrate is 20g of urea, the phosphorus and potassium source is 15g of potassium dihydrogen phosphate, the humic acid is 10g of potassium fulvate, and the trace element is 2g of EDTA chelated trace element; the inoculation amount of EM bacteria is 2% of the total volume of the cooled filtrate.

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