Process for preparing functional organic fertilizer by using subcritical water heat technology to degrade agricultural and forestry organic waste

Abstract

This invention discloses a process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology. First, agricultural and forestry organic waste is selected as raw material. After being crushed to a particle size of 20-80 mesh, deionized water is added to adjust the material's moisture content to 50%-60%. Then, after stirring evenly, the mixture is pretreated at a constant temperature of 30-40℃ for 30-60 minutes. Subsequently, the carbon-nitrogen ratio, cellulose content, heavy metal content, and moisture uniformity of the pretreated mixture are tested. Simultaneously, based on the test results, adjusting components are added, and the mixture is allowed to stand at a constant temperature of 40℃ for 20-30 minutes to allow the adjusting components to fully integrate with the material. Based on this, this invention, through the synergistic effect of segmented subcritical hydrothermal degradation and composite degradation aids, combined with the appropriate adjustment steps for raw material components, has the advantages of achieving complete degradation of recalcitrant components in agricultural and forestry organic waste and improving waste conversion rate.

Description

Technical Field

[0001] This invention relates to the field of organic fertilizer technology, specifically to a process for degrading agricultural and forestry organic waste using subcritical hydrothermal technology and preparing functional organic fertilizer. Background Technology

[0002] Agricultural and forestry organic waste is a general term for various wastes generated during agricultural production, forestry cultivation, and processing. It mainly includes crop straw, livestock and poultry manure, forestry fallen leaves and branches, fruit and vegetable processing residues, and edible fungi residue. These wastes are rich in carbon, nitrogen, phosphorus, potassium, and various trace elements, making them important renewable resources. Efficient resource utilization can solve the environmental pollution problems caused by waste accumulation and compensate for the soil degradation and decreased soil fertility resulting from excessive fertilizer use, thus meeting the requirements of green agricultural development and the "dual carbon" target.

[0003] Currently, the main methods for resource utilization of agricultural and forestry organic waste include composting, pyrolysis carbonization, and anaerobic fermentation, among which composting is the most widely used method for preparing organic fertilizer. However, traditional composting processes have many limitations and cannot meet the needs of large-scale, high-quality organic fertilizer production; although pyrolysis carbonization can produce biochar fertilizers, it consumes a lot of energy and is prone to nutrient loss; anaerobic fermentation is mainly used for biogas production, and the by-product organic fertilizer has poor functionality.

[0004] Subcritical hydrothermal technology is a green treatment technology that utilizes the special physicochemical properties of water (such as decreased dielectric constant, increased ion product, and enhanced solubility) under subcritical conditions (temperature 150-374℃, pressure 0.5-22MPa) to achieve rapid degradation of organic waste. This technology has advantages such as high reaction efficiency, no secondary pollution, and retention of active components in the waste, and has been increasingly applied in the treatment of agricultural and forestry organic waste in recent years. However, the current application of subcritical hydrothermal technology in organic fertilizer preparation still has many shortcomings, as detailed below: 1. Low degradation efficiency and incomplete treatment of recalcitrant components: Recalcitrant components such as lignin, cellulose, and hemicellulose contained in agricultural and forestry organic waste are difficult to completely degrade under conventional subcritical hydrothermal conditions, resulting in low waste conversion rate (usually below 70%) and a large amount of residual solid residue. This not only wastes resources but also affects the quality and application effect of organic fertilizer. Furthermore, the products of subcritical hydrothermal treatment alone have low surface area and poor thermal stability, which further limits the functionality of fertilizer.

[0005] 2. Severe loss of functional components and low added value of organic fertilizer: In the subcritical hydrothermal reaction process, unreasonable control of parameters such as temperature and pressure leads to the decomposition and loss of a large number of functional active components such as amino acids, humic acid, and vitamins in the waste. The organic fertilizer produced can only meet the basic fertility requirements and lacks additional functions such as soil improvement, crop growth promotion, and stress and disease resistance. It is out of touch with the market demand for functional organic fertilizer. In addition, there is also the problem of nitrogen loss due to ammonia volatilization in traditional composting process, which further reduces fertilizer efficiency. Summary of the Invention

[0006] To address the aforementioned technical problems of low degradation efficiency and severe loss of functional components, this invention provides the following technical solution: The process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology includes the following specific steps: S1, Raw material pretreatment: S11 uses agricultural and forestry organic waste as raw material. After being crushed to a particle size of 20-80 mesh, deionized water is added to adjust the moisture content of the material to 50%-60%. S12, add pretreatment additive, stir evenly, and then pretreatment at 30-40℃ for 30-60 minutes, and set aside; S2, Raw material component adaptation and adjustment: S21, detect the carbon-nitrogen ratio, cellulose content, heavy metal content and moisture uniformity of the pretreated mixture; S22, based on the test results, add the adjusting components and let it stand at a constant temperature of 40℃ for 20-30 minutes to allow the adjusting components to fully integrate with the material, so that the carbon-nitrogen ratio of the material is adjusted to 25:1-30:1, the cellulose content is controlled at 20%-30%, the heavy metal content is reduced to below the NY1110-2010 standard limit, and the moisture uniformity deviation is ≤5%; S3, Segmented Subcritical Hydrothermal Degradation: The pretreated material is fed into a subcritical hydrothermal reactor, a composite degradation aid is added, and the reactor is sealed. A segmented temperature and pressure controlled reaction is then carried out, specifically in two stages: First stage: Control the reaction temperature at 140-160℃, the pressure at 5-8MPa, and the reaction time at 40-60min; Second stage: After the first stage reaction is completed, without depressurization, directly raise the reaction temperature to 190-220℃ and the pressure to 9-12MPa, and the reaction time to 30-40min, while simultaneously introducing oxygen. S4, Targeted Regulation of Degradation Products: S41. After the staged hydrothermal degradation is completed, the degradation products are sampled and tested. The test indicators include humic acid content, total amino acid content, pH value and toxic by-product content. S42, based on the test results, add regulators in a targeted manner and stir at a constant temperature of 45-50℃ for 30-40 minutes to ensure uniform product composition, so that the pH value of the degradation product is stabilized at 7.0-8.0, the humic acid content is increased to ≥10%, the total amino acid content is ≥6%, and the content of toxic by-products is reduced to below 0.01%. S43, after completing the regulation, the material is cooled to room temperature and filtered through a 100-mesh sieve to remove undegraded residues, thus obtaining refined degradation products; S5, Synergistic Functional Modification: The refined degradation product is fed into the modification reactor, a functional modifier is added, and the mixture is stirred at a constant temperature of 50-60℃ for 60-90 minutes to achieve functional modification. S6, Post-processing: S61, the functionalized modified material is fed into a vacuum dryer and dried until the moisture content is ≤15%; S62, then crushed to a particle size of 40-60 mesh, and sieved to remove impurities; S63 is then added as a binder, followed by granulation, cooling, and sieving to obtain the finished functional organic fertilizer product.

[0007] As a preferred embodiment of the process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology as described in this invention, wherein: in S11, the agricultural and forestry organic waste is a combination of two or more of the following: crop straw, livestock and poultry manure, forestry dead branches and leaves, fruit and vegetable processing residue, and edible fungus residue.

[0008] As a preferred embodiment of the process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology as described in this invention, in step S12, the pretreatment aid accounts for 0.5%-1.5% of the total mass of the raw materials, and the pretreatment aid is prepared by mixing wood ash and bentonite in a mass ratio of 2:1.

[0009] As a preferred embodiment of the process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology as described in this invention, in step S22, the regulating components are prepared by mixing well-rotted livestock and poultry manure, cellulase, and chelating agent in a mass ratio of 5:1:0.2; the cellulase accounts for 0.1%-0.3% of the total mass of the raw materials; and the chelating agent is EDTA disodium, accounting for 0.05%-0.1% of the total mass of the raw materials.

[0010] As a preferred embodiment of the process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology as described in this invention, in step S3, the composite degradation aid accounts for 1.0%-2.0% of the total mass of the raw materials, and the composite degradation aid is prepared by nano-titanium dioxide and an alkaline regulator in a mass ratio of 1:3, wherein the alkaline regulator is sodium carbonate.

[0011] As a preferred embodiment of the process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology as described in this invention, in the second stage of S3, the oxygen flow rate is set to 0.1-0.2 L / min.

[0012] As a preferred embodiment of the process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology according to the present invention, wherein: in step S42, the regulator is composed of humic acid synergistic mother liquor, amino acid supplement, and alkaline buffer; the humic acid synergistic mother liquor accounts for 1.0%-1.5% of the total mass of the degradation products; the amino acid supplement accounts for 0.5%-1.0% of the total mass of the degradation products, and the amino acid supplement is prepared by glycine and glutamic acid in a mass ratio of 1:1; the alkaline buffer accounts for 0.3%-0.5% of the total mass of the degradation products, and the alkaline buffer is prepared by sodium bicarbonate and potassium dihydrogen phosphate in a mass ratio of 2:1.

[0013] As a preferred embodiment of the process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology as described in this invention, in step S5, the functional modifier accounts for 2.0%-3.0% of the total mass of the refined degradation product, and the functional modifier is prepared by mixing microbial inoculant and humic acid synergist in a mass ratio of 1:2; the microbial inoculant is one or more of Bacillus subtilis, Bacillus licheniformis, and Trichoderma; the humic acid synergist is natural humic acid prepared by hydrothermal treatment of straw.

[0014] As a preferred embodiment of the process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology as described in this invention, in step S61, the drying temperature is set to 60-70℃ and the vacuum degree is set to 0.06-0.08MPa.

[0015] As a preferred embodiment of the process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology as described in this invention, in step S63, the binder accounts for 1.0%-1.5% of the total mass of the functionalized modified material, and the binder is prepared by mixing starch and sodium carboxymethyl cellulose in a mass ratio of 3:1.

[0016] Compared with existing technologies: 1. Through the synergistic effect of segmented subcritical hydrothermal degradation and composite degradation aids, combined with the adjustment steps of raw material components, it has the advantages of achieving complete degradation of the difficult-to-degrade components of agricultural and forestry organic waste and improving the waste conversion rate; 2. By controlling the subcritical hydrothermal reaction intensity through segmented temperature and pressure control, combined with the protective effect of composite additives and the directional regulation of degradation products, it has the advantages of achieving efficient retention of functional active ingredients and avoiding nutrient loss; 3. Through the dual effects of raw material component adaptation and regulation and degradation product directional control, the composition and pH of materials and products can be precisely controlled, which has the advantages of achieving stable organic fertilizer quality, avoiding the harm of by-products, and improving the product qualification rate. 4. By selecting various types of agricultural and forestry organic waste for mixed treatment and combining them with raw material component adaptation and adjustment steps, it has the advantages of achieving synergistic utilization of different waste components, broadening the applicable scope of raw materials, and improving the comprehensive utilization rate of resources. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below. Example

[0018] This invention provides a process for degrading agricultural and forestry organic waste using subcritical hydrothermal technology and preparing functional organic fertilizer, including the following specific steps: S1, Raw material pretreatment: S11, select agricultural and forestry organic waste as raw material, after crushing to a particle size of 20 mesh, add deionized water to adjust the material moisture content to 50%; among which, agricultural and forestry organic waste is two or more combinations of crop straw, livestock and poultry manure, forestry dead branches and fallen leaves, fruit and vegetable processing residue, and edible fungus residue. S12, add pretreatment aid, stir evenly, and pretreat at 30℃ for 30 minutes, then set aside; wherein, the pretreatment aid accounts for 0.5% of the total mass of raw materials, and the pretreatment aid is prepared by mixing wood ash and bentonite in a mass ratio of 2:1. Wood ash is used to adjust the pH of the material and reduce the generation of acidic by-products in the subsequent hydrothermal reaction, while bentonite is used to adsorb heavy metal ions in the material to avoid the accumulation of heavy metals in organic fertilizer, and at the same time improve the dispersibility of the material, laying the foundation for subsequent hydrothermal degradation, and solving the problems of excessive heavy metals and uneven material dispersion in the existing process; S2, Raw material component adaptation and adjustment: S21, detect the carbon-nitrogen ratio, cellulose content, heavy metal content and moisture uniformity of the pretreated mixture; S22, based on the test results, an adjusting component is added and the mixture is kept at a constant temperature of 40℃ for 20 minutes to allow the adjusting component to fully integrate with the material, thereby adjusting the carbon-nitrogen ratio of the material to 25:1, controlling the cellulose content to 20%, reducing the heavy metal content to below the NY1110-2010 standard limit, and reducing the moisture uniformity deviation to ≤5%. The adjusting component is composed of well-rotted livestock and poultry manure (used to adjust the carbon-nitrogen ratio), cellulase, and a chelating agent in a mass ratio of 5:1:0.2. The cellulase accounts for 0.1% of the total raw material mass and is used to pretreat cellulose to assist subsequent hydrothermal degradation. The chelating agent is disodium EDTA, accounting for 0.05% of the total raw material mass. This step solves the problem of uneven composition and unstable degradation efficiency of different mixed raw materials, achieving precise control of raw material compatibility and laying a uniform material foundation for subsequent segmented hydrothermal degradation. This is a creative improvement, distinct from the shortcomings of existing processes that involve "blind mixing and undirected adjustment." S3, Segmented Subcritical Hydrothermal Degradation: The pretreated material is fed into a subcritical hydrothermal reactor, a composite degradation aid is added, and the reactor is sealed. A segmented temperature and pressure controlled reaction is then carried out, specifically in two stages: The first stage (mild degradation stage): the reaction temperature is controlled at 140℃, the pressure at 5MPa, and the reaction time at 40min. This stage mainly degrades the easily degradable components in the material (such as starch, protein, and simple sugars), while initially destroying the surface structure of lignin and cellulose to avoid the loss of functional components due to direct degradation at high temperature. The weak oxidizing properties of subcritical water are used to initially release nutrients in the material. The second stage (deep degradation stage): After the first stage reaction is completed, without depressurization, the reaction temperature is directly raised to 190℃ and the pressure to 9MPa, and the reaction time is 30min. At the same time, oxygen is introduced (the oxygen flow rate is set to 0.1L / min). In this stage, under the synergistic effect of the composite degradation aid and oxygen, lignin, cellulose and other difficult-to-degrade components are completely degraded and transformed into small molecule organic matter (such as humic acid and amino acid precursors) that can be absorbed and utilized by crops. At the same time, the generation of toxic and harmful byproducts is inhibited, solving the problem of incomplete degradation in existing processes. The composite degradation aid accounts for 1.0% of the total mass of the raw materials. The composite degradation aid is prepared by nano-titanium dioxide and alkaline regulator in a mass ratio of 1:3. The alkaline regulator is sodium carbonate. Nano-titanium dioxide acts as a catalyst to reduce the activation energy of degradation of difficult-to-degrade components and improve degradation efficiency. At the same time, it has a photocatalytic oxidation effect in the presence of oxygen, further decomposing toxic by-products. The alkaline regulator is used to adjust the pH of the reaction system (maintaining a pH value of 7.5), reducing the damage of acidic substances to functional components, while promoting the hydrolysis reaction of cellulose, increasing the generation of active components such as humic acid, and avoiding the corrosion problem of equipment caused by acid and alkali reagents in traditional processes.

[0019] S4, Targeted Regulation of Degradation Products: S41. After the staged hydrothermal degradation is completed, the degradation products are sampled and tested. The test indicators include humic acid content, total amino acid content, pH value and toxic by-product (small molecule organic acid, aldehyde) content. S42, based on the test results, a regulator is added in a targeted manner, and the mixture is stirred at 45℃ for 30 minutes to ensure uniform product composition. This stabilizes the pH of the degradation product at 7.0, increases the humic acid content to ≥10%, the total amino acid content to ≥6%, and reduces the content of toxic byproducts to below 0.01%. The regulator consists of a humic acid-enhancing mother liquor, an amino acid supplement, and an alkaline buffer. The humic acid-enhancing mother liquor accounts for 1.0% of the total mass of the degradation product, increasing the humic acid content. The amino acid supplement accounts for 0.5% of the total mass of the degradation product, and is prepared by mixing glycine and glutamic acid in a 1:1 mass ratio. The alkaline buffer accounts for 0.3% of the total mass of the degradation product, and is prepared by mixing sodium bicarbonate and potassium dihydrogen phosphate in a 2:1 mass ratio. This step achieves precise control of the degradation product, solving the problems of large fluctuations in product composition and unstable quality in the original process. Through targeted supplementation and buffer adjustment, it provides a high-quality base material for subsequent functional modification, demonstrating significant innovation and practicality. S43, after completing the regulation, the material is cooled to room temperature and filtered through a 100-mesh sieve to remove undegraded residues, thus obtaining refined degradation products; S5, Synergistic Functional Modification: The refined degradation products are fed into a modification reactor, a functional modifier is added, and the mixture is stirred at a constant temperature of 50℃ for 60 minutes to achieve functional modification, endowing the organic fertilizer with soil improvement and crop growth promotion functions; wherein, the functional modifier accounts for 2.0% of the total mass of the refined degradation products, and the functional modifier is prepared by microbial inoculant and humic acid synergist in a mass ratio of 1:2; the microbial inoculant is one or a mixture of Bacillus subtilis, Bacillus licheniformis, and Trichoderma (viable count ≥ 200 million / g), which can improve the soil micro-ecological environment, inhibit the growth of harmful soil bacteria, and promote crop root development; the humic acid synergist is natural humic acid prepared by hydrothermal treatment of straw (purity ≥ 85%), which can enhance the water and fertilizer retention capacity of organic fertilizer, promote crop nutrient absorption, and at the same time, synergistically work with the active ingredients in the degradation products to enhance the functionality of organic fertilizer and solve the problem of low added value of existing organic fertilizers; S6, Post-processing: S61, the functionalized modified material is fed into a vacuum dryer and dried until the moisture content is ≤15%; wherein, the drying temperature is set to 60℃ and the vacuum degree is set to 0.06MPa; S62, then crushed to a particle size of 40 mesh, and sieved to remove impurities; S63, finally add binder, granulate, cool and screen to obtain functional organic fertilizer product; wherein, binder accounts for 1.0% of the total mass of the functionalized modified material, and binder is prepared by starch and sodium carboxymethyl cellulose in a mass ratio of 3:1. Example

[0020] This invention provides a process for degrading agricultural and forestry organic waste using subcritical hydrothermal technology and preparing functional organic fertilizer, including the following specific steps: S1, Raw material pretreatment: S11, select agricultural and forestry organic waste as raw material, after crushing to a particle size of 40 mesh, add deionized water to adjust the material moisture content to 55%; among which, agricultural and forestry organic waste is two or more combinations of crop straw, livestock and poultry manure, forestry dead branches and fallen leaves, fruit and vegetable processing residue, and edible fungus residue. S12, add pretreatment aid, stir evenly, and pretreatment at 35℃ for 45 minutes, then set aside; wherein, the pretreatment aid accounts for 1.0% of the total mass of raw materials, and the pretreatment aid is prepared by mixing wood ash and bentonite in a mass ratio of 2:1. Wood ash is used to adjust the pH of the material and reduce the generation of acidic by-products in the subsequent hydrothermal reaction, while bentonite is used to adsorb heavy metal ions in the material to avoid the accumulation of heavy metals in organic fertilizer, and at the same time improve the dispersibility of the material, laying the foundation for subsequent hydrothermal degradation, and solving the problems of excessive heavy metals and uneven material dispersion in the existing process; S2, Raw material component adaptation and adjustment: S21, detect the carbon-nitrogen ratio, cellulose content, heavy metal content and moisture uniformity of the pretreated mixture; S22, based on the test results, an adjusting component is added and the mixture is kept at a constant temperature of 40℃ for 25 minutes to allow the adjusting component to fully integrate with the material, thereby adjusting the carbon-nitrogen ratio of the material to 27.5:1, controlling the cellulose content to 25%, reducing the heavy metal content to below the NY1110-2010 standard limit, and reducing the moisture uniformity deviation to ≤5%. The adjusting component is composed of well-rotted livestock and poultry manure (used to adjust the carbon-nitrogen ratio), cellulase, and a chelating agent in a mass ratio of 5:1:0.2. The cellulase accounts for 0.2% of the total raw material mass and is used to pretreat cellulose to assist subsequent hydrothermal degradation. The chelating agent is disodium EDTA, accounting for 0.075% of the total raw material mass. This step solves the problem of uneven composition and unstable degradation efficiency of different mixed raw materials, achieving precise control of raw material compatibility and laying a uniform material foundation for subsequent segmented hydrothermal degradation. This is a creative improvement, distinct from the shortcomings of existing processes that involve "blind mixing and undirected adjustment." S3, Segmented Subcritical Hydrothermal Degradation: The pretreated material is fed into a subcritical hydrothermal reactor, a composite degradation aid is added, and the reactor is sealed. A segmented temperature and pressure controlled reaction is then carried out, specifically in two stages: The first stage (mild degradation stage): the reaction temperature is controlled at 150℃, the pressure at 6.5MPa, and the reaction time at 50min. This stage mainly degrades the easily degradable components in the material (such as starch, protein, and simple sugars), while initially destroying the surface structure of lignin and cellulose to avoid the loss of functional components due to direct degradation at high temperature. The weak oxidizing properties of subcritical water are used to initially release the nutrients in the material. The second stage (deep degradation stage): After the first stage reaction is completed, without depressurization, the reaction temperature is directly raised to 205℃ and the pressure to 10.5MPa, and the reaction time is 35min. At the same time, oxygen is introduced (the oxygen flow rate is set to 0.15L / min). In this stage, under the synergistic effect of the composite degradation aid and oxygen, lignin, cellulose and other difficult-to-degrade components are completely degraded and transformed into small molecule organic matter (such as humic acid and amino acid precursors) that can be absorbed and utilized by crops. At the same time, the generation of toxic and harmful byproducts is inhibited, solving the problem of incomplete degradation in existing processes. The composite degradation aid accounts for 1.5% of the total mass of the raw materials. The composite degradation aid is prepared by nano-titanium dioxide and alkaline regulator in a mass ratio of 1:3. The alkaline regulator is sodium carbonate. Nano-titanium dioxide acts as a catalyst to reduce the degradation activation energy of difficult-to-degrade components and improve degradation efficiency. At the same time, it has a photocatalytic oxidation effect in the presence of oxygen, further decomposing toxic by-products. The alkaline regulator is used to adjust the pH of the reaction system (maintaining a pH value of 8.0), reducing the damage of acidic substances to functional components, while promoting the hydrolysis reaction of cellulose, increasing the generation of active components such as humic acid, and avoiding the corrosion problem of equipment caused by acid and alkali reagents in traditional processes.

[0021] S4, Targeted Regulation of Degradation Products: S41. After the staged hydrothermal degradation is completed, the degradation products are sampled and tested. The test indicators include humic acid content, total amino acid content, pH value and toxic by-product (small molecule organic acid, aldehyde) content. S42, based on the test results, a regulator is added in a targeted manner, and the mixture is stirred at a constant temperature of 47.5℃ for 35 minutes to ensure uniform product composition. This stabilizes the pH value of the degradation product at 7.5, increases the humic acid content to ≥10%, the total amino acid content to ≥6%, and reduces the content of toxic byproducts to below 0.01%. The regulator consists of a humic acid-enhancing mother liquor, an amino acid supplement, and an alkaline buffer. The humic acid-enhancing mother liquor accounts for 1.25% of the total mass of the degradation product, increasing the humic acid content. The amino acid supplement accounts for 0.75% of the total mass of the degradation product, and is prepared by mixing glycine and glutamic acid in a 1:1 mass ratio. The alkaline buffer accounts for 0.4% of the total mass of the degradation product, and is prepared by mixing sodium bicarbonate and potassium dihydrogen phosphate in a 2:1 mass ratio. This step achieves precise control of the degradation product, solving the problems of large fluctuations in product composition and unstable quality in the original process. Through targeted supplementation and buffer adjustment, it provides a high-quality base material for subsequent functional modification, demonstrating significant creativity and practicality. S43, after completing the regulation, the material is cooled to room temperature and filtered through a 100-mesh sieve to remove undegraded residues, thus obtaining refined degradation products; S5, Synergistic Functional Modification: The refined degradation products are fed into a modification reactor, a functional modifier is added, and the mixture is stirred at a constant temperature of 55℃ for 75 minutes to achieve functional modification, endowing the organic fertilizer with soil improvement and crop growth promotion functions; wherein, the functional modifier accounts for 2.5% of the total mass of the refined degradation products, and the functional modifier is prepared by microbial inoculant and humic acid synergist in a mass ratio of 1:2; the microbial inoculant is one or a mixture of Bacillus subtilis, Bacillus licheniformis, and Trichoderma (viable count ≥ 200 million / g), which can improve the soil micro-ecological environment, inhibit the growth of harmful soil bacteria, and promote crop root development; the humic acid synergist is natural humic acid prepared by hydrothermal treatment of straw (purity ≥ 85%), which can enhance the water and fertilizer retention capacity of organic fertilizer, promote crop nutrient absorption, and at the same time, synergistically work with the active ingredients in the degradation products to enhance the functionality of organic fertilizer and solve the problem of low added value of existing organic fertilizers; S6, Post-processing: S61, the functionalized modified material is fed into a vacuum dryer and dried until the moisture content is ≤15%; wherein, the drying temperature is set to 65℃ and the vacuum degree is set to 0.07MPa; S62, then crushed to a particle size of 50 mesh, and sieved to remove impurities; S63, finally add binder, granulate, cool and screen to obtain functional organic fertilizer product; wherein, binder accounts for 1.25% of the total mass of the functionalized modified material, and the binder is made of starch and sodium carboxymethyl cellulose in a mass ratio of 3:1. Example

[0022] This invention provides a process for degrading agricultural and forestry organic waste using subcritical hydrothermal technology and preparing functional organic fertilizer, including the following specific steps: S1, Raw material pretreatment: S11, select agricultural and forestry organic waste as raw material, after crushing to a particle size of 80 mesh, add deionized water to adjust the material moisture content to 60%; among which, agricultural and forestry organic waste is two or more combinations of crop straw, livestock and poultry manure, forestry dead branches and fallen leaves, fruit and vegetable processing residue, and edible fungus residue. S12, add pretreatment aid, stir evenly, and pretreat at 40℃ for 60 minutes, then set aside; wherein, the pretreatment aid accounts for 1.5% of the total mass of raw materials, and the pretreatment aid is prepared by mixing wood ash and bentonite in a mass ratio of 2:1. Wood ash is used to adjust the pH of the material and reduce the generation of acidic by-products in the subsequent hydrothermal reaction, while bentonite is used to adsorb heavy metal ions in the material to avoid the accumulation of heavy metals in organic fertilizer, and at the same time improve the dispersibility of the material, laying the foundation for subsequent hydrothermal degradation, and solving the problems of excessive heavy metals and uneven material dispersion in the existing process; S2, Raw material component adaptation and adjustment: S21, detect the carbon-nitrogen ratio, cellulose content, heavy metal content and moisture uniformity of the pretreated mixture; S22, based on the test results, an adjusting component is added and the mixture is kept at a constant temperature of 40℃ for 30 minutes to allow the adjusting component to fully integrate with the material, thereby adjusting the carbon-nitrogen ratio of the material to 30:1, controlling the cellulose content to 30%, reducing the heavy metal content to below the NY1110-2010 standard limit, and reducing the moisture uniformity deviation to ≤5%. The adjusting component is composed of well-rotted livestock and poultry manure (used to adjust the carbon-nitrogen ratio), cellulase, and a chelating agent in a mass ratio of 5:1:0.2. The cellulase accounts for 0.3% of the total raw material mass and is used to pretreat cellulose to assist subsequent hydrothermal degradation. The chelating agent is disodium EDTA, accounting for 0.1% of the total raw material mass. This step solves the problem of uneven composition and unstable degradation efficiency of different mixed raw materials, achieving precise control of raw material compatibility and laying a uniform material foundation for subsequent segmented hydrothermal degradation. This is a creative improvement, distinct from the shortcomings of existing processes that involve "blind mixing and undirected adjustment." S3, Segmented Subcritical Hydrothermal Degradation: The pretreated material is fed into a subcritical hydrothermal reactor, a composite degradation aid is added, and the reactor is sealed. A segmented temperature and pressure controlled reaction is then carried out, specifically in two stages: The first stage (mild degradation stage): the reaction temperature is controlled at 160℃, the pressure at 8MPa, and the reaction time at 60min. This stage mainly degrades the easily degradable components in the material (such as starch, protein, and simple sugars), while initially destroying the surface structure of lignin and cellulose to avoid the loss of functional components due to direct degradation at high temperature. The weak oxidizing properties of subcritical water are used to initially release nutrients in the material. The second stage (deep degradation stage): After the first stage reaction is completed, without depressurization, the reaction temperature is directly raised to 220℃ and the pressure to 12MPa, and the reaction time is 40min. At the same time, oxygen is introduced (the oxygen flow rate is set to 0.2L / min). In this stage, under the synergistic effect of the composite degradation aid and oxygen, lignin, cellulose and other difficult-to-degrade components are completely degraded and transformed into small molecule organic matter (such as humic acid and amino acid precursors) that can be absorbed and utilized by crops. At the same time, the generation of toxic and harmful byproducts is inhibited, solving the problem of incomplete degradation in existing processes. The composite degradation aid accounts for 2.0% of the total mass of the raw materials. The composite degradation aid is prepared by nano-titanium dioxide and alkaline regulator in a mass ratio of 1:3. The alkaline regulator is sodium carbonate. Nano-titanium dioxide acts as a catalyst to reduce the activation energy of degradation of difficult-to-degrade components and improve degradation efficiency. At the same time, it has a photocatalytic oxidation effect in the presence of oxygen, further decomposing toxic by-products. The alkaline regulator is used to adjust the pH of the reaction system (maintaining a pH value of 8.5), reducing the damage of acidic substances to functional components, while promoting the hydrolysis reaction of cellulose, increasing the generation of active components such as humic acid, and avoiding the corrosion problem of equipment caused by acid and alkali reagents in traditional processes.

[0023] S4, Targeted Regulation of Degradation Products: S41. After the staged hydrothermal degradation is completed, the degradation products are sampled and tested. The test indicators include humic acid content, total amino acid content, pH value and toxic by-product (small molecule organic acid, aldehyde) content. S42, based on the test results, a regulator is added in a targeted manner, and the mixture is stirred at 50℃ for 40 minutes to ensure uniform product composition. This stabilizes the pH of the degradation product at 8.0, increases the humic acid content to ≥10%, the total amino acid content to ≥6%, and reduces the content of toxic byproducts to below 0.01%. The regulator consists of a humic acid-enhancing mother liquor, an amino acid supplement, and an alkaline buffer. The humic acid-enhancing mother liquor accounts for 1.5% of the total mass of the degradation product, increasing the humic acid content. The amino acid supplement accounts for 1.0% of the total mass of the degradation product, and is prepared by mixing glycine and glutamic acid in a 1:1 mass ratio. The alkaline buffer accounts for 0.5% of the total mass of the degradation product, and is prepared by mixing sodium bicarbonate and potassium dihydrogen phosphate in a 2:1 mass ratio. This step achieves precise control of the degradation product, solving the problems of large fluctuations in product composition and unstable quality in the original process. Through targeted supplementation and buffer adjustment, it provides a high-quality base material for subsequent functional modification, demonstrating significant innovation and practicality. S43, after completing the regulation, the material is cooled to room temperature and filtered through a 100-mesh sieve to remove undegraded residues, thus obtaining refined degradation products; S5, Synergistic Functional Modification: The refined degradation products are fed into a modification reactor, a functional modifier is added, and the mixture is stirred at a constant temperature of 60℃ for 90 minutes to achieve functional modification, endowing the organic fertilizer with soil improvement and crop growth promotion functions; wherein, the functional modifier accounts for 3.0% of the total mass of the refined degradation products, and the functional modifier is prepared by microbial inoculant and humic acid synergist in a mass ratio of 1:2; the microbial inoculant is one or a mixture of Bacillus subtilis, Bacillus licheniformis, and Trichoderma (viable bacteria count ≥ 200 million / g), which can improve the soil micro-ecological environment, inhibit the growth of harmful soil bacteria, and promote crop root development; the humic acid synergist is natural humic acid prepared by hydrothermal treatment of straw (purity ≥ 85%), which can enhance the water and fertilizer retention capacity of organic fertilizer, promote crop nutrient absorption, and at the same time, synergistically work with the active ingredients in the degradation products to enhance the functionality of organic fertilizer and solve the problem of low added value of existing organic fertilizers; S6, Post-processing: S61, the functionalized modified material is fed into a vacuum dryer and dried until the moisture content is ≤15%; wherein, the drying temperature is set to 70℃ and the vacuum degree is set to 0.08MPa; S62, then crushed to a particle size of 60 mesh, and sieved to remove impurities; S63, finally add binder, granulate, cool and screen to obtain functional organic fertilizer product; wherein, binder accounts for 1.5% of the total mass of the functionalized modified material, and the binder is made of starch and sodium carboxymethyl cellulose in a mass ratio of 3:1.

[0024] Example 1 Example 2 Example 3 Total conversion rate of agricultural and forestry organic waste ≥76% ≥78% ≥75% Organic matter content ≥40% ≥45% ≥43% As can be seen from the table above, the preparation processes carried out in Examples 1-3 all showed good performance in terms of total conversion rate and organic matter content of agricultural and forestry organic waste. After use, Example 2 showed the best results.

[0025] Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, as long as there is no structural conflict, the features in the disclosed embodiments can be combined with each other in any manner. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology, characterized in that, The specific steps are as follows: S1, Raw material pretreatment: S11 uses agricultural and forestry organic waste as raw material. After being crushed to a particle size of 20-80 mesh, deionized water is added to adjust the moisture content of the material to 50%-60%. S12, add pretreatment additive, stir evenly, and then pretreatment at 30-40℃ for 30-60 minutes, and set aside; S2, Raw material component adaptation and adjustment: S21, detect the carbon-nitrogen ratio, cellulose content, heavy metal content and moisture uniformity of the pretreated mixture; S22, based on the test results, add the adjusting components and let it stand at a constant temperature of 40℃ for 20-30 minutes to allow the adjusting components to fully integrate with the material, so that the carbon-nitrogen ratio of the material is adjusted to 25:1-30:1, the cellulose content is controlled at 20%-30%, the heavy metal content is reduced to below the NY1110-2010 standard limit, and the moisture uniformity deviation is ≤5%; S3, Segmented Subcritical Hydrothermal Degradation: The pretreated material is fed into a subcritical hydrothermal reactor, a composite degradation aid is added, and the reactor is sealed. A segmented temperature and pressure controlled reaction is then carried out, specifically in two stages: First stage: Control the reaction temperature at 140-160℃, the pressure at 5-8MPa, and the reaction time at 40-60min; Second stage: After the first stage reaction is completed, without depressurization, directly raise the reaction temperature to 190-220℃ and the pressure to 9-12MPa, and the reaction time to 30-40min, while simultaneously introducing oxygen. S4, Targeted Regulation of Degradation Products: S41. After the staged hydrothermal degradation is completed, the degradation products are sampled and tested. The test indicators include humic acid content, total amino acid content, pH value and toxic by-product content. S42, based on the test results, add regulators in a targeted manner and stir at a constant temperature of 45-50℃ for 30-40 minutes to ensure uniform product composition, so that the pH value of the degradation product is stabilized at 7.0-8.0, the humic acid content is increased to ≥10%, the total amino acid content is ≥6%, and the content of toxic by-products is reduced to below 0.01%. S43, after completing the regulation, the material is cooled to room temperature and filtered through a 100-mesh sieve to remove undegraded residues, thus obtaining refined degradation products; S5, Synergistic Functional Modification: The refined degradation product is fed into the modification reactor, a functional modifier is added, and the mixture is stirred at a constant temperature of 50-60℃ for 60-90 minutes to achieve functional modification. S6, Post-processing: S61, the functionalized modified material is fed into a vacuum dryer and dried until the moisture content is ≤15%; S62, then crushed to a particle size of 40-60 mesh, and sieved to remove impurities; S63 is then added as a binder, followed by granulation, cooling, and sieving to obtain the finished functional organic fertilizer product.

2. The process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology according to claim 1, characterized in that, In S11, the agricultural and forestry organic waste is a combination of two or more of the following: crop straw, livestock and poultry manure, forestry dead branches and leaves, fruit and vegetable processing residue, and edible fungus residue.

3. The process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology according to claim 1, characterized in that, In S12, the pretreatment aid accounts for 0.5%-1.5% of the total mass of the raw materials, and the pretreatment aid is prepared by mixing wood ash and bentonite in a mass ratio of 2:

1.

4. The process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology according to claim 1, characterized in that, In step S22, the regulating components are prepared by mixing well-rotted livestock and poultry manure, cellulase, and chelating agent in a mass ratio of 5:1:0.2; the cellulase accounts for 0.1%-0.3% of the total mass of the raw materials; the chelating agent is EDTA disodium, which accounts for 0.05%-0.1% of the total mass of the raw materials.

5. The process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology according to claim 1, characterized in that, In S3, the composite degradation aid accounts for 1.0%-2.0% of the total mass of the raw materials, and the composite degradation aid is prepared by nano titanium dioxide and alkaline regulator in a mass ratio of 1:3, wherein the alkaline regulator is sodium carbonate.

6. The process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology according to claim 1, characterized in that, In the second stage of S3, the oxygen flow rate is set to 0.1-0.2 L / min.

7. The process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology according to claim 1, characterized in that, In step S42, the regulator is composed of humic acid synergistic mother liquor, amino acid supplement, and alkaline buffer; the humic acid synergistic mother liquor accounts for 1.0%-1.5% of the total mass of the degradation products; the amino acid supplement accounts for 0.5%-1.0% of the total mass of the degradation products, and the amino acid supplement is prepared by glycine and glutamic acid in a mass ratio of 1:1; the alkaline buffer accounts for 0.3%-0.5% of the total mass of the degradation products, and the alkaline buffer is prepared by sodium bicarbonate and potassium dihydrogen phosphate in a mass ratio of 2:

1.

8. The process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology according to claim 1, characterized in that, In step S5, the functional modifier accounts for 2.0%-3.0% of the total mass of the refined degradation product, and the functional modifier is prepared by microbial agent and humic acid synergist in a mass ratio of 1:2; the microbial agent is one or more of Bacillus subtilis, Bacillus licheniformis, and Trichoderma; the humic acid synergist is natural humic acid prepared by hydrothermal treatment of straw.

9. The process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology according to claim 1, characterized in that, In step S61, the drying temperature is set to 60-70℃ and the vacuum degree is set to 0.06-0.08MPa.

10. The process for degrading agricultural and forestry organic waste and preparing functional organic fertilizer using subcritical hydrothermal technology according to claim 1, characterized in that, In S63, the binder accounts for 1.0%-1.5% of the total mass of the functionalized modified material, and the binder is prepared by mixing starch and sodium carboxymethyl cellulose in a mass ratio of 3:1.