Livestock and poultry manure biochar-based fertilizer and preparation method thereof

Abstract

The present invention discloses a livestock and poultry manure biochar-based fertilizer, comprising the following raw materials in parts by weight: 10-42% of dilute protein solution and collagenase-modified livestock and poultry manure biochar, 20-40% of urea, 7-25% of diammonium phosphate, 7-24% of potassium chloride or potassium sulfate, 0.5-1% of modified starch, and 6-23% of bentonite. The livestock and poultry manure is selected from one of chicken manure, cow manure, and pig manure. After the biochar is modified with collagenase, the surface of the biochar has more phenolic hydroxyl groups, carboxyl groups, aldehyde groups, and hydroxyl functional groups, which are effective for NH4 + , PO4 3‑ , K + , has a stronger adsorption effect, collagenase modification makes the protein distribution more uniform, and the generated groups form a stable chemical bond with the biochar surface: it improves the dispersibility of the modified biochar in aqueous solution and reduces agglomeration; it has better chemical stability in acidic and alkaline environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of fertilizers, and in particular relates to a livestock and poultry excrement biochar-based fertilizer and a preparation method thereof. Background Art

[0002] Existing biochar in charcoal-based fertilizers is primarily derived from plant materials such as straw and rice husks. While biochar has a high carbon content, strong adsorption properties, and a certain slow-release effect, it is lightweight and low in nutrients. This makes granulation difficult during production, and it can easily clump or become powdery after granulation. Furthermore, biochar's low nutrient content requires more fertilizer than chemical fertilizers to ensure adequate nutrient input per unit area of land. Furthermore, biochar is alkaline, potentially causing ammonia volatilization and reducing phosphorus availability. The revised 2020 version of the Law on the Prevention and Control of Environmental Pollution by Solid Waste stipulates that agricultural solid waste such as straw and livestock excrement are now subject to new regulatory requirements. To protect the environment, relevant companies will now have the obligation and responsibility to properly dispose of and effectively utilize waste. Against this backdrop, the widespread adoption of proper waste treatment technologies that achieve resource recycling is imperative. In view of the current shortcomings in the harmless treatment and resource utilization of livestock and poultry manure in China, such as long composting time, incomplete harmlessness, low production capacity, high cost investment, and difficulty in promotion, the development of a new livestock and poultry manure biochar-based fertilizer and its preparation method is a technical problem that needs to be urgently solved. Summary of the Invention

[0003] In response to the deficiencies in the prior art, the present invention provides a new livestock and poultry manure biochar-based fertilizer and a preparation method thereof. After the livestock and poultry manure biochar in the present invention is modified with collagenase, the organic matter and structure on the surface of the biochar can be effectively changed, making it more active. This is because collagenase is a protease that can specifically catalyze the hydrolysis reaction of proteins. There is a modified layer of protein or other nitrogen-containing organic matter on the surface of proteinized biochar. When collagenase acts on it, it decomposes the surface-modified protein into smaller polypeptides or amino acids by cutting specific peptide bonds. This decomposition process exposes more functional groups (such as carboxyl groups, hydroxyl groups, and phenolic hydroxyl groups), thereby enhancing the chemical activity of the surface.

[0004] Furthermore, during the enzymatic treatment process, local structural reorganization may occur on the biochar surface due to the decomposition of macromolecules and the exposure of functional groups. For example, protein decomposition can make the molecular arrangement of the modified layer more loose or regular, thereby changing the surface roughness and pore characteristics of the biochar. This structural reorganization helps to increase the specific surface area and the accessibility of active sites. Collagenase treatment allows small molecules (such as amino acids) produced by protein decomposition to further react chemically with active groups on the biochar surface to generate new functional groups. At the same time, these small molecules are also retained on the biochar surface due to adsorption, changing its surface hydrophilicity, polarity, and charge distribution. This change in chemical properties can enhance the adsorption performance or catalytic activity of biochar. After collagenase treatment of the biochar surface, the newly added functional groups and more active chemical bonds (such as carboxyl, hydroxyl, and phenolic hydroxyl groups) increase the surface free energy. This means that the treated biochar has a stronger chemical reaction ability with other molecules or ions, thereby exhibiting higher activity.

[0005] That is, collagenase can significantly change the surface chemical properties and structure of proteinized biochar by specifically catalyzing protein decomposition and indirectly modifying the surface. The treated biochar exhibits a higher specific surface area, richer active functional groups and stronger chemical reaction ability, thus becoming "more active" and having more phenolic hydroxyl, carboxyl, aldehyde and hydroxyl functional groups on the surface, which is more responsive to NH4 + , PO4 3- , K + , has a stronger adsorption effect.

[0006] Specifically, the livestock and poultry manure biochar-based fertilizer provided by the present invention includes the following raw materials in parts by weight: 10-42% of dilute protein solution and collagenase-modified livestock and poultry manure biochar, 20-40% of urea, 7-25% of diammonium phosphate, 7-24% of potassium chloride or potassium sulfate, 0.5-1% of modified starch, and 6-23% of bentonite. The livestock and poultry manure is selected from one of chicken manure, cow manure, and pig manure.

[0007] Furthermore, the steps for modifying livestock and poultry manure biochar with dilute protein solution and collagenase are as follows:

[0008] Step S1: crushing the agricultural and livestock waste into an average particle size of 2-5 mm using a crusher, and drying in an oven at 60-70° C. for 24-48 hours to obtain pretreated biomass;

[0009] Step S2: placing the pretreated biomass into a high-temperature furnace and carbonizing it in the absence of oxygen, using a gradual heating method to obtain preliminary biochar;

[0010] Step S3, mixing the preliminary biochar and the dilute protein solution, ultrasonically treating for 20-30 minutes, standing for 24-48 hours, drying and solidifying, washing with 500-3000 ml of deionized water 3-5 times to remove unadsorbed protein, and finally drying in an oven at 60-80° C. to constant weight to obtain proteinized biochar;

[0011] Step S4: mixing the proteinized biochar with the collagenase solution, stirring or oscillating the mixture in a constant temperature stirrer, terminating the enzyme reaction, and drying it in an oven at 60-80° C. to constant weight to obtain finished biochar, i.e., collagenase-modified livestock and poultry manure biochar.

[0012] Furthermore, the gradual heating in step S2 is specifically as follows: first, maintain the temperature at 200-300° C. for 1-2 hours, then increase the temperature to 400-500° C. and maintain it for 2-3 hours, and finally increase the temperature to 600° C. and maintain it for 1 hour.

[0013] Furthermore, the drying and curing in step S3 is specifically drying in an oven at 40-50°C for 24 hours, and then heating and curing at 80-100°C.

[0014] Furthermore, the diluted protein solution in step S3 is prepared by dissolving the protein in a buffer solution, such as PBS, at a protein concentration of 1-5 mg / mL. Ensure that the protein solution is uniform and avoid aggregation. The protein may be collagen or gelatin with a molecular weight of 30,000-50,000 kD.

[0015] Furthermore, step S3 of mixing the preliminary biochar with the dilute protein solution specifically involves adding the biochar to the protein solution at a liquid-to-solid ratio of 1:5-10, stirring at 30-40°C and a stirring speed of 120-150 rpm for 24-48 hours. This process facilitates the adsorption or binding of protein molecules on the biochar surface, forming a hydrophilic protein film and enhancing the functionality of the biochar.

[0016] Furthermore, the concentration of the collagenase solution in step S4 is 1-5 U / mL, where U represents the enzyme activity unit. A buffer is used to maintain the pH of the mixture of the proteinized biochar and the collagenase solution at 6.5-7.0, at which the optimal activity of the collagenase can be maintained.

[0017] Furthermore, in step S4, the biochar and collagenase solution are mixed at a liquid-to-solid ratio of 1:5-10, and the mixture is stirred or shaken in a constant temperature stirrer at 30-40°C for 24-48 hours at a stirring speed of 120-150 rpm.

[0018] Furthermore, the enzyme reaction in step S4 is terminated by filtering out the collagenase solution, or by washing the biochar 3-5 times with 500-3000 ml of deionized water to remove unreacted collagenase.

[0019] The present invention also provides a method for preparing the livestock and poultry manure biochar-based fertilizer as described above, wherein the mixed powder is placed in a disc granulator, and a modified starch solution is evenly sprayed on the mixed powder. After rolling granulation in the disc granulator, the fertilizer granules with a particle size of 3.35 to 4.75 mm are screened by a screening machine with a 4-6 mesh sieve, and the fertilizer granules are dried at 40° C. to 50° C. to obtain the final product.

[0020] After the biochar is modified with collagenase, the surface of the biochar has more phenolic hydroxyl, carboxyl, aldehyde and hydroxyl functional groups, which are more effective for NH4 + , PO4 3- , K + , has a stronger adsorption effect, and the enhancement of this effect is based on the following reasons:

[0021] First, protein hydrolysis. Collagenase is a specific protease that can hydrolyze peptide bonds in proteins, breaking them down into smaller peptides and amino acid molecules. During this process, the following functional groups are exposed or generated: carboxyl (-COOH) - in the amino acid molecules generated by protein decomposition, structures with carboxyl termini are released and attached to the biochar surface; phenolic hydroxyl (-OH) - the phenolic hydroxyl groups on the side chains of certain amino acids (such as tyrosine) are exposed after decomposition; hydroxyl (-OH) - after the decomposition of certain hydroxyl-containing amino acids in proteins (such as serine and threonine), their hydroxyl groups are retained and distributed on the biochar surface.

[0022] Second, the chemical modification of the biochar surface. During the enzymatic hydrolysis process of proteinized biochar, its surface modification layer will undergo a series of chemical changes and modifications, further enhancing the generation of oxygen-containing groups and exposing the intrinsic groups of biochar. While the protein is being degraded, the protein layer covering the biochar surface is partially peeled off, and the previously hidden hydroxyl, phenolic hydroxyl and carboxyl groups are re-exposed, and the aldehyde and hydroxyl groups generated in the oxidation process. The protein degradation process may be accompanied by oxidation reactions, especially the surface of biochar rich in carbon skeletons is prone to generate aldehyde and hydroxyl groups under oxidative conditions.

[0023] Third, the secondary effect of enzymatic hydrolysis products. The small molecular products (such as peptides and amino acids) generated after the protein is degraded by collagenase will be adsorbed and chemically reacted with the surface of biochar, thereby further introducing new oxygen-containing functional groups, such as carboxyl and phenolic hydroxyl groups; some amino acids (such as glutamic acid and tyrosine) contain more carboxyl and phenolic hydroxyl groups, and their degradation products may adhere to the surface of biochar, further such as the generation of aldehyde groups; amino acids or peptides may undergo oxidative deamination reactions (deaminoation) during the enzymatic hydrolysis process, and part of the carbon skeleton in its structure will form aldehyde groups.

[0024] Fourth, the indirect effect of collagenase on the structure of biochar. The action of collagenase is not limited to the degradation of proteins, but also indirectly affects the structure and surface chemical properties of the biochar itself; the exposure of surface pores. After the protein layer is removed, the porous structure of the biochar is exposed, which increases the specific surface area and active sites; local oxidation reaction. Enzymatic degradation may trigger oxidation reactions in the microenvironment, converting the original carbon skeleton structure on the biochar surface into oxygen-containing functional groups such as aldehydes and hydroxyls.

[0025] Fifth, the synergistic effect of ultrasound and static process. During the ultrasonic treatment and static process, the interaction between protein and biochar accelerated the generation and distribution optimization of groups. The mechanical action of ultrasound made the protein more evenly attached to the surface of biochar and promoted the adequacy of enzyme reaction. The static process enhanced the binding between the biochar surface and the enzymatic hydrolysis products, further increasing the density of phenolic hydroxyl groups, carboxyl groups, aldehyde groups and hydroxyl groups.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. After the biochar is modified with collagenase, the surface of the biochar has more phenolic hydroxyl, carboxyl, aldehyde and hydroxyl functional groups, which are more effective for NH4 + , PO4 3- , K + , has a stronger adsorption effect;

[0028] 2. The proportion of biochar from livestock and poultry manure is relatively large, and when making carbon-based fertilizer, it can completely overcome the shortcomings of making carbon-based fertilizer from plant-derived biochar;

[0029] 3. Advantages of livestock and poultry manure biochar after enzyme modification and activation:

[0030] 3.1. Rich functional groups and improved chemical activity

[0031] The modified biochar surface has more oxygen-containing functional groups (such as phenolic hydroxyl, carboxyl, aldehyde, hydroxyl, etc.). These groups have the following functions: enhance the adsorption of ions, provide active sites for catalytic reactions, and are beneficial to chemical processes such as redox reactions and esterification reactions; improve the hydrophilicity of biochar, making it more dispersible in aqueous environments;

[0032] 3.2. Increased specific surface area and enhanced adsorption capacity

[0033] During the collagenase modification process, protein degradation and reorganization make the surface modification layer thinner and more uniform, and partially masked pores are exposed again, resulting in a significant increase in specific surface area, providing more contact sites for adsorption reactions; the optimization of the pore structure enhances the physical adsorption capacity of ions;

[0034] 3.3. Green and environmentally friendly modification process

[0035] Collagenase is a biocatalyst with mild and efficient properties: the modification process is carried out at low temperature and in weak acid or neutral conditions, without the need for high temperature or strong acid or alkaline conditions, thus reducing environmental pollution. The enzyme itself is biodegradable, avoiding the secondary pollution problems that may be caused by traditional chemical modifiers.

[0036] 3.4. Improved selective adsorption capacity

[0037] Through collagenase modification, the surface of proteinized biochar has more polar and oxygen-containing groups, showing higher selective adsorption performance for specific molecules or ions;

[0038] 3.5. Enhanced mechanical strength and stability

[0039] Collagenase modification makes the protein distribution more uniform, and the generated groups form a stable chemical bond with the biochar surface: it improves the dispersibility of the modified biochar in aqueous solution and reduces agglomeration; it also has better chemical stability in acidic and alkaline environments;

[0040] 4. Compared with plant-derived charcoal fertilizers, livestock and poultry manure contains higher nutrient content, so less chemical fertilizer is added to livestock and poultry manure biochar-based fertilizers, reducing production costs. In addition, livestock and poultry manure biochar-based fertilizers have higher nutrient content than plant-derived biochar-based fertilizers, which can reduce the amount of fertilizer applied per unit area of land, making it more acceptable to farmers.

[0041] 5. Carbon-based fertilizer equipment includes commonly used disc granulator or drum granulator, screening machine, oven, etc. The production equipment cost is low and can be produced in a separate factory with low investment and production cost. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0043] Example 1

[0044] This embodiment provides a livestock and poultry manure biochar-based fertilizer, comprising the following raw materials in parts by weight: 27% of dilute protein solution and collagenase-modified livestock and poultry manure biochar, 34% of urea, 11% of diammonium phosphate, 8% of potassium chloride, 1% of modified starch, and 19% of bentonite, wherein the livestock and poultry manure is selected from chicken manure.

[0045] The steps for modifying livestock and poultry manure biochar with diluted protein solution and collagenase are as follows:

[0046] Step S1: crushing the agricultural and livestock waste into an average particle size of 3 mm using a crusher, and drying in an oven at 60° C. for 48 hours to obtain pretreated biomass;

[0047] Step S2: placing the pretreated biomass into a high-temperature furnace and carbonizing it under anaerobic conditions by gradually increasing the temperature to obtain preliminary biochar; the gradual temperature increase is specifically as follows: first, maintaining it at 200°C for 2 hours, then increasing the temperature to 450°C and maintaining it for 2 hours, and finally increasing the temperature to 600°C and maintaining it for 1 hour;

[0048] Step S3, mixing the preliminary biochar and the dilute protein solution, ultrasonically treating for 20-30 minutes, standing for 24-48 hours, drying and solidifying, washing with 2000 ml of deionized water 5 times, and finally drying in an oven at 60-80°C to constant weight to obtain proteinized biochar; drying and solidification are specifically drying in an oven at 45°C for 24 hours, and then heating and solidifying at 90°C. The dilute protein solution is collagen dissolved in PBS buffer, and the protein concentration is 3 mg / mL.

[0049] The step S3 of mixing the preliminary biochar and the dilute protein solution specifically involves adding the biochar to the protein solution at a liquid-to-solid ratio of 1:10, and stirring for 48 hours at 40° C. and a stirring speed of 150 r / min.

[0050] Step S4: mixing the proteinized biochar with the collagenase solution, stirring or oscillating the mixture in a constant temperature stirrer, terminating the enzyme reaction, and drying it in an oven at 60° C. to constant weight to obtain finished biochar, i.e., collagenase-modified livestock and poultry manure biochar.

[0051] The concentration of the collagenase solution in step S4 is 3 U / mL, and a buffer solution is used to maintain the pH of the mixture of proteinized biochar and collagenase solution at 7.0.

[0052] In step S4, the biochar and collagenase solution are mixed at a liquid-to-solid ratio of 1:10, and the mixture is stirred or shaken in a constant temperature stirrer at 40° C. for 48 hours at a stirring speed of 150 rpm.

[0053] The enzyme reaction in step S4 is terminated by filtering out the collagenase solution to remove unreacted collagenase.

[0054] Example 2

[0055] This embodiment provides a method for preparing the livestock and poultry manure biochar-based fertilizer as described in Example 1, specifically, placing the mixed powder in a disc granulator, evenly spraying the modified starch solution, rolling granulation in the disc granulator, screening the fertilizer granules with a particle size of 4.75 mm through a screening machine with a 4-mesh sieve, and drying at 40°C to obtain the final product.

[0056] Performance testing:

[0057] Weigh 1.0 g of dilute protein solution and collagenase-modified biochar and unmodified biochar, and add them into 100 mL of ammonium sulfate, potassium dihydrogen phosphate, and potassium sulfate solution, respectively. The concentrations of ammonium sulfate, potassium dihydrogen phosphate, and potassium sulfate are 1000 mg / L, 2000 mg / L, and 2000 mg / L, respectively. Oscillate the mixture on a constant temperature oscillator for 24 h. After the oscillation is completed, centrifuge and measure the NH4 + , PO4 3- , K + The concentration of biochar was calculated, and the adsorption capacity of each biochar was calculated. The group with modified biochar was recorded as the experimental group, and the group with unmodified biochar was recorded as the experimental group control group. The results are shown in the table:

[0058] project Experimental group control group <![CDATA[NH4 after adsorption + Concentration (mg / L)]]> 53.12 86.16 <![CDATA[PO4 after adsorption 3- Concentration (mg / L)]]> 116.60 224.69 <![CDATA[K after adsorption + Concentration (mg / L)]]> 451.20 492.25 <![CDATA[Adsorption capacity (NH4 + mg / g)]]> 6.36 4.81 <![CDATA[Adsorption amount (PO4 3- mg / g)]]> 13.48 9.16 Adsorption capacity (K+mg / g) 18.82 17.16

[0059] From the test results, it can be seen that after biochar is modified with collagenase, the surface has more phenolic hydroxyl, carboxyl, aldehyde and hydroxyl functional groups, which are more sensitive to NH4 + , PO4 3- , K + , has a stronger adsorption effect.

[0060] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A livestock and poultry manure biochar-based fertilizer, characterized in that: The method comprises the following raw materials in parts by weight: 10-42% of dilute protein solution and collagenase-modified livestock and poultry manure biochar, 20-40% of urea, 7-25% of diammonium phosphate, 7-24% of potassium chloride or potassium sulfate, 0.5-1% of modified starch, and 6-23% of bentonite, wherein the livestock and poultry manure is selected from one of chicken manure, cow manure, and pig manure; The steps for modifying livestock and poultry manure biochar with dilute protein solution and collagenase are as follows: Step S1: crushing the agricultural and livestock waste into an average particle size of 2-5 mm using a crusher, and drying in an oven at 60-70° C. for 24-48 hours to obtain pretreated biomass; Step S2: placing the pretreated biomass into a high-temperature furnace and carbonizing it in the absence of oxygen, using a gradual heating method to obtain preliminary biochar; Step S3, mixing the preliminary biochar and the dilute protein solution, ultrasonically treating for 20-30 minutes, standing for 24-48 hours, drying and solidifying, washing with 500-3000 ml of deionized water for 3-5 times, and finally drying in an oven at 60-80° C. to constant weight to obtain proteinized biochar; Step S4: mixing the proteinized biochar with the collagenase solution, stirring or oscillating the mixture in a constant temperature stirrer, terminating the enzyme reaction, and drying the mixture in an oven at 60-80° C. to a constant weight to obtain finished biochar.

2. The livestock and poultry manure biochar-based fertilizer according to claim 1, characterized in that: The gradual heating in step S2 is specifically as follows: first, keep the temperature at 200-300° C. for 1-2 hours, then heat to 400-500° C. and keep for 2-3 hours, and finally heat to 600° C. and keep for 1 hour.

3. The livestock and poultry manure biochar-based fertilizer according to claim 2, characterized in that: The drying and curing in step S3 is specifically drying in an oven at 40-50°C for 24 hours, and then heating and curing at 80-100°C.

4. The livestock and poultry manure biochar-based fertilizer according to claim 1, characterized in that: The diluted protein solution in step S3 is prepared by dissolving the protein in a buffer solution, with a protein concentration of 1-5 mg / mL.

5. The livestock and poultry manure biochar-based fertilizer according to claim 2, characterized in that: The step S3 of mixing the preliminary biochar and the dilute protein solution specifically involves adding the biochar to the protein solution at a liquid-to-solid ratio of 1:5-10, and stirring at 30-40° C. and a stirring speed of 120-150 rpm for 24-48 hours.

6. The livestock and poultry manure biochar-based fertilizer according to claim 1, characterized in that: The concentration of the collagenase solution in step S4 is 1-5 U / mL, and a buffer solution is used to maintain the pH of the mixture of proteinized biochar and collagenase solution at 6.5-7.

0.

7. The livestock and poultry manure biochar-based fertilizer according to claim 1, characterized in that: In step S4, the biochar and collagenase solution are mixed at a liquid-to-solid ratio of 1:5-10, and the mixture is stirred or shaken in a constant temperature stirrer at 30-40° C. for 24-48 hours at a stirring speed of 120-150 rpm.

8. The livestock and poultry manure biochar-based fertilizer according to claim 1, characterized in that: The enzyme reaction in step S4 is terminated by removing the collagenase solution by filtration or by washing the biochar 3-5 times with 500-3000 ml of deionized water to remove unreacted collagenase.

9. The method for preparing the livestock and poultry manure biochar-based fertilizer according to any one of claims 1 to 8, characterized in that: The mixed powder is placed in a disc granulator and evenly sprayed with the modified starch solution. After rolling granulation in the disc granulator, the fertilizer granules are screened with a 4-6 mesh sieve to obtain granules with a particle size of 3.35-4.75 mm and dried at 40-50°C to obtain the final product.