Multifunctional biological organic fertilizer based on agricultural and forestry wastes and preparation method thereof

Abstract

The invention belongs to the technical field of biological organic fertilizers, and provides a multifunctional biological organic fertilizer based on agricultural and forestry wastes and a preparation method thereof. The preparation method comprises the following steps: combining chitosan oligosaccharide molecules with sepiolite, and combining a composite bacterial liquid with a chitosan oligosaccharide-sepiolite composite matrix to obtain a chitosan oligosaccharide-sepiolite-composite probiotic carrier; sodium sulfite and epichlorohydrin are utilized to enable the modified lignin to have higher solubility, and the modified lignin is combined with the nano montmorillonite to form a stable network through glutaraldehyde; converting the carbon-rich biomass into biochar, and combining starch, soybean protein and a mixed trace element solution to obtain a composite synergist; lignocellulose of agricultural and forestry wastes is subjected to structural damage, and cellulose and hemicellulose are degraded and a carbon source is provided for subsequent functional microorganisms under the synergistic effect of a compound enzyme solution; in the composting fermentation process, deep degradation of organic matters is achieved, a sodium alginate solution is sprayed to form a stable nutrient slow-release network, and meanwhile the water retention capacity of the particles is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of biological organic fertilizers, and relates to a multifunctional biological organic fertilizer based on agricultural and forestry waste and a preparation method thereof. Background Art

[0002] With the continuous expansion of the scale of agricultural and forestry production, a large amount of agricultural and forestry waste is generated every year, including crop straws, fruit shells, rice husks, wood chips, branches, orchard pruning residues, etc. The main sources of these wastes are by-products in the planting industry, forestry industry, and primary processing processes, and their compositions are rich in nutrients essential for plants such as carbon, nitrogen, phosphorus, and potassium. However, due to the large amount of lignocellulose contained in agricultural and forestry waste, its structure is complex and stable, resulting in an extremely slow natural degradation rate. Traditional treatment methods for agricultural and forestry waste mainly include incineration, landfill, and simple composting. However, these treatment methods not only fail to fully utilize their inherent biological value but also bring serious environmental problems. The rapid development of modern agriculture has put forward higher requirements for soil fertility and crop growth. Although the excessive use of chemical fertilizers has increased crop yields in the short term, it has also led to a decline in soil quality and deterioration of the ecological environment. Problems such as soil compaction, nutrient imbalance, reduction of microbial diversity, and decline in fertilizer utilization rate are becoming increasingly prominent, forming a bottleneck in agricultural production. Especially in the context of facing climate change, arable land degradation, and limited resources, agricultural production urgently needs to transform towards green sustainability.

[0003] The production of traditional organic fertilizers mostly relies on animal manure or municipal sludge. The acquisition and treatment of these raw materials have limitations and may bring problems of pathogenic microorganism and heavy metal pollution. In contrast, agricultural and forestry waste as a raw material has the advantages of wide sources, low cost, and relatively environmental friendliness. As a rich and cheap renewable resource, agricultural and forestry waste has a high content of organic matter and various mineral nutrient elements essential for plants, and has become an important potential raw material for preparing organic fertilizers. By using modern technical means to treat and transform agricultural and forestry waste, not only can the resource utilization of waste be realized, but also a biological organic fertilizer with environmental friendly characteristics can be prepared. Therefore, the preparation of a multifunctional biological organic fertilizer based on agricultural and forestry waste can not only realize the efficient resource utilization of waste, but also enhance the economic added value of agricultural and forestry waste, meeting the agricultural demand for efficient and environmental friendly fertilizers. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a multifunctional bio-organic fertilizer based on agricultural and forestry waste and its preparation method. Through the efficient resource utilization of agricultural and forestry waste, it is converted into organic fertilizer. By the synergistic effect of chemical modification, microbial fermentation and functional materials, chitosan-sepiolite-composite probiotic carrier, modified lignin-nano-clay slow-release factor and composite synergist are prepared, and combined with multi-stage composting fermentation technology, deep degradation and functional treatment of waste are realized, so as to meet the needs of actual production.

[0005] To achieve this purpose, the present invention adopts the following technical solutions:

[0006] In the first aspect, the present invention provides a preparation method of a multifunctional bio-organic fertilizer based on agricultural and forestry waste, and the preparation method includes:

[0007] A1. Add sepiolite powder to hydrochloric acid solution for soaking, filter and then add it to sodium hydroxide solution for soaking, filter and wash with water to obtain activated sepiolite powder. Add chitosan solution to the activated sepiolite powder, adjust the pH to 8 and stir, and obtain chitosan-sepiolite composite matrix after suction filtration and drying. Then mix the composite bacterial solution with the chitosan-sepiolite composite matrix to obtain chitosan-sepiolite-composite probiotic carrier;

[0008] A2. Disperse lignin powder in deionized water, adjust the pH to 9, adjust the temperature to the first temperature and stir, then add sodium sulfite solution and epichlorohydrin, filter and wash to obtain modified lignin. Disperse nano-montmorillonite in the activation solution, stir and activate and then filter and wash to obtain nano-clay. Mix the modified lignin dispersion with nano-clay, add NPK solution and mix evenly, then add glutaraldehyde and stir to obtain modified lignin-nano-clay slow-release factor;

[0009] A3. Transfer the carbon-rich biomass to a carbonization furnace, introduce a mixed gas and heat up to the second temperature for heat preservation to obtain biochar. Immerse the biochar in hydrochloric acid solution and stir, filter and wash to obtain activated biochar. Mix starch and soy protein and disperse them in deionized water, heat up to the third temperature to obtain a colloid, add glutaraldehyde and stir to obtain a biomass adhesive. Then mix the trace element solution with the biomass adhesive to obtain an adhesive-trace element solution. Mix the activated biochar with the adhesive-trace element solution, dry and crush to obtain a composite synergist;

[0010] S1. Load the crushed agricultural and forestry waste into a high-pressure steam explosion tank and maintain it, instantaneously relieve the pressure to obtain steam explosion material. Transfer the steam explosion material to an alkali solution for soaking, adjust the temperature to the first temperature and keep it to obtain alkali-soaked material. Add the composite enzyme solution to the alkali-soaked material, adjust the temperature to the fourth temperature, adjust the pH to 5, and stir to obtain enzymolysis material;

[0011] S2. Disperse white rot fungi and soft rot fungi in the enzymatically hydrolyzed material and mix evenly. Turn the pile every 2 days during the first-stage cycle to obtain the first-stage material. Mix the first-stage material with sterilized soybean meal, inoculate Bacillus and Actinomycetes, and turn the pile every 2 days during the second-stage cycle. Add chitosan-sepiolite-composite probiotic carrier, modified lignin-nano-clay slow-release factor, and composite synergist on the 2nd day during the second-stage cycle to obtain the second-stage material;

[0012] S3. When the temperature of the second-stage material pile drops below 40 °C, turn the pile once a week during the third-stage cycle. Add chitosan-sepiolite-composite probiotic carrier, modified lignin-nano-clay slow-release factor, and composite synergist and mix evenly in the first week of the third-stage cycle. Spray sodium alginate solution in the last week of the third-stage cycle to obtain the multifunctional bio-organic fertilizer based on agricultural and forestry waste.

[0013] Sepiolite is a naturally occurring layered silicate mineral, and its unique crystal structure enables it to exhibit excellent performance in a variety of environmental applications. Specifically, sepiolite has remarkable physical adsorption, chemical stability, and cation exchange capacity, which are mainly attributed to its layered structure and surface characteristics. The presence of negative charges on its surface and between layers allows it to effectively adsorb positively charged molecules or ions, such as amino acids, cationic organic molecules, and certain metal ions. This property provides great potential for its chemical modification and functionalization. However, in order to further enhance the adsorption capacity, surface activity, and application performance of sepiolite in composite materials, it is usually necessary to carry out acid-base activation treatment to optimize its physicochemical properties and enhance its binding ability with functional molecules. In the present invention, sepiolite is first immersed in hydrochloric acid solution, and its chemical mechanism mainly involves acid dissolution, that is, hydrochloric acid reacts with impurities in the sepiolite surface or pore structure through the action of protons, dissolving and removing weakly bound metal cations and other impurities. This process can not only significantly improve the purity of sepiolite but also expose more active sites by removing impurities. Silanol groups are an important source of sepiolite surface activity, and as hydrophilic groups, they can interact with a variety of chemical molecules or functional materials. Through acid treatment, it may also partially change the layer spacing of sepiolite, making its layered structure more loose, thus providing more effective space for the subsequent embedding of molecules or ions. In addition, the treatment of sepiolite with hydrochloric acid may further improve its specific surface area and porosity by dissolving the surface irregular structure, thereby significantly enhancing its adsorption capacity. The sepiolite after acid treatment is then placed in sodium hydroxide solution for alkaline activation treatment. The main function of the alkali treatment is to further remove the insoluble impurities that may remain after acid treatment, and at the same time introduce more hydroxyl functional groups on the sepiolite surface. This process involves partial hydrolysis of the silicon-oxygen bond to generate new hydroxyl and sodium silicate structures, thereby further enhancing the surface polarity and chemical reactivity of sepiolite. In addition, the alkali treatment may also exert a slight peeling effect on the interlayer structure of sepiolite, making the layered structure more dispersed and open. This change in the microstructure further increases the specific surface area and adsorption capacity of sepiolite, providing more abundant active sites for its binding with chitosan oligosaccharide and composite bacterial solution.

[0014] After acid-base activation, sepiolite was used to load chitosan oligosaccharide to form a functional composite matrix. Chitosan oligosaccharide is an oligosaccharide obtained by partial deacetylation of chitosan. Its molecular structure is rich in amino and hydroxyl groups, which endows it with good antibacterial properties, biocompatibility, and biostimulation effects. Under weakly alkaline conditions, some of the amino groups in the chitosan oligosaccharide molecule will be protonated to form positively charged amino ions. This positive charge enables chitosan oligosaccharide to bind to the negatively charged active sites on the surface of sepiolite through electrostatic adsorption. In addition, the hydroxyl groups in chitosan oligosaccharide can also chemically combine with the silanol groups on the surface of sepiolite by forming hydrogen bonds, thereby further enhancing the binding strength between the two. The molecular chain of chitosan oligosaccharide can also be embedded in the pores or interlayer spaces of sepiolite to achieve physical adsorption through van der Waals forces. These multiple binding mechanisms enable chitosan oligosaccharide to be firmly loaded on the surface of sepiolite, forming a stable composite matrix. The introduction of chitosan oligosaccharide not only enhances the functionality of sepiolite but also endows it with various biological properties. As a biostimulant, chitosan oligosaccharide can effectively promote the growth and metabolism of microorganisms, especially playing a key role in the loading process of the composite bacterial solution. The composite bacterial solution is composed of lactic acid bacteria, yeast, and Bacillus licheniformis. These three strains have different functions and biological activities and can achieve synergistic effects during the composting process. Lactic acid bacteria secrete lactic acid to lower the pH value of the compost, thereby inhibiting the reproduction of pathogenic bacteria and stimulating the growth of plant roots through metabolites such as organic acids and exopolysaccharides. Yeast can decompose complex carbohydrates and produce various organic acids, vitamins, and other secondary metabolites, further increasing the nutrient content of the compost. As a growth-promoting bacterium, Bacillus licheniformis can secrete antibiotic-like substances to fight pathogenic bacteria and release degradation enzymes such as cellulase to accelerate the decomposition of organic matter. The activated sepiolite, due to its significantly increased specific surface area and enhanced surface activity, has a strong adsorption capacity for microbial cells and their metabolites. This adsorption capacity not only improves the attachment efficiency of the composite bacterial solution on the carrier surface but also provides a physical barrier for microorganisms through the chitosan oligosaccharide coating to prevent the influence of external environmental stress on microbial activity. The biostimulation effect of chitosan oligosaccharide further promotes the growth and metabolic capacity of microorganisms, improving the functionality and stability of the composite bacterial solution. Through the acid-base activation of sepiolite, the loading of chitosan oligosaccharide, and the adsorption of the composite bacterial solution, the finally prepared chitosan oligosaccharide-sepiolite-composite probiotic carrier not only has adsorption performance and slow-release ability but also has enhanced microbial activity and biostimulation function, providing an important guarantee for the organic matter transformation and fertilizer efficiency improvement in the composting process.

[0015] Lignin, as a natural polymer widely present in plant cell walls, is the main component of lignocellulosic waste. Its molecular structure is complex, containing abundant functional groups such as phenolic hydroxyl groups, ether bonds, and aromatic rings, endowing lignin with good chemical reactivity, stability, and high thermal stability, making it have great application potential in the field of biomass resource utilization. However, there are strong hydrogen bond interactions between lignin molecules. At the same time, due to its hydrophobic aromatic structure, lignin in its natural state shows the characteristic of being difficult to disperse uniformly in water. This poor dispersibility limits the application of lignin in many fields, especially its functional utilization in composite materials and solution systems. Therefore, in order to improve the dispersibility and reactivity of lignin, alkaline dispersion and chemical modification methods are adopted in this invention. First, lignin powder is dispersed in deionized water, and the pH of the system is adjusted to 9 by adding sodium hydroxide solution. The alkaline environment can effectively break the hydrogen bonds and intramolecular weak chemical bonds between lignin molecules, thereby promoting the swelling and dispersion of lignin. This process can not only reduce the degree of particle aggregation of lignin but also make the active sites inside it more easily exposed, providing a good basis for subsequent chemical modification reactions. At the same time, the increase in temperature further accelerates the swelling and expansion of lignin molecular chains, enhancing its fluidity and chemical reactivity in the water system. Sodium sulfite dissociates into sulfite ions under alkaline conditions, and these sulfite ions can react with phenolic hydroxyl groups in lignin molecules to form sulfonic acid groups. The essence of this sulfonation reaction is to introduce hydrophilic sulfonic acid groups into lignin molecules through electrophilic substitution on the aromatic ring. Sulfonation modification improves the hydrophilicity and chemical reactivity of lignin, enhances its solubility in aqueous solutions, and at the same time endows it with higher surface activity and the ability to combine with other materials.

[0016] In addition to sulfonation modification, in order to further enhance the mechanical stability and structural strength of lignin, epichlorohydrin is introduced as a cross-linking agent for cross-linking modification in the experiment. Under alkaline conditions, the epoxy group of epichlorohydrin can undergo a ring-opening reaction with phenolic hydroxyl groups in lignin molecules to form ether bond connections, thereby realizing the cross-linking between lignin molecules. The result of this cross-linking reaction is the formation of a more stable three-dimensional network structure, improving the mechanical properties and chemical resistance of lignin. This enhanced stability not only enables lignin to maintain its structural integrity in a more severe environment but also provides a stronger binding ability for subsequent composite with nanoclay. Nano-montmorillonite, as a layered silicate mineral, its unique nano-scale interlayer structure endows it with good adsorption properties and ion exchange capabilities. The interlayer of nano-montmorillonite usually contains exchangeable cations, and these cations can undergo exchange reactions with other cations or positively charged molecules, thus enabling montmorillonite to exhibit excellent adsorption characteristics. At the same time, its high specific surface area and abundant surface active sites further enhance its binding ability with organic molecules or nutrient ions.

[0017] When preparing the modified lignin-nanoclay composite material, the sulfonated and cross-linked lignin is mixed with the activated nano-montmorillonite, and the two are fully contacted and undergo various interactions through stirring. First, the sulfonic acid groups in lignin can bind to the cation exchange sites on the surface of nano-montmorillonite through electrostatic attraction to form stable ionic bonds. In addition, the hydroxyl groups in the lignin molecule can bind to the hydroxyl groups or oxygen atoms on the surface of montmorillonite through hydrogen bonds, further enhancing the binding strength of the composite material; at the same time, the molecular chain of lignin may be embedded in the interlayer space of montmorillonite to achieve physical adsorption through van der Waals forces. These multiple binding mechanisms enable lignin and nano-montmorillonite to form a stable composite structure. The sulfonation and cross-linking modification of lignin significantly improves its hydrophilicity and nutrient loading capacity, while nano-montmorillonite provides a stable adsorption base and slow-release environment for lignin. The three-dimensional network structure of the material further delays the nutrient release rate, enabling it to better match the needs of plants, thereby reducing fertilizer loss and improving the nutrient utilization efficiency.

[0018] Biochar is a solid material formed by pyrolyzing carbon-rich biomass at high temperature in an oxygen-deficient or inert atmosphere. Under high-temperature conditions, cellulose, hemicellulose, and lignin undergo thermal decomposition reactions, and the carbon-rich solid part gradually transforms into a structure mainly composed of an aromatic carbon skeleton. At the same time, with the rapid pyrolysis of cellulose and hemicellulose and the slow decomposition of lignin, biochar forms a highly developed porous structure and a high specific surface area, which provides excellent adsorption performance and loading capacity for it. This structural characteristic not only makes biochar a good nutrient carrier but also provides an ideal microenvironment for the attachment and survival of microorganisms. In addition, the formation of the aromatic carbon skeleton during the carbonization process also improves the hydrophobicity of biochar, making it exhibit more stable physicochemical properties in the soil. There are often a certain amount of inorganic mineral impurities in the carbonized biochar that occupy the pores of biochar, reducing its specific surface area and adsorption performance. In order to further enhance the functionality and surface activity of biochar, the biochar is activated by hydrochloric acid solution in the experiment to improve its adsorption performance and loading capacity.

[0019] In the functionalization process of biochar, biomass adhesives play a crucial role as a multifunctional composite material in experiments. The biomass adhesives use starch and soy protein as the main raw materials. Their function is to effectively load trace elements onto the surface of biochar while enhancing the stability of the composite material. Starch and soy protein are two natural polymer materials with wide sources and low costs, and they have good potential for chemical modification. Starch, with its rich linear and branched molecular structures, can exhibit excellent gelatinization characteristics and bonding properties under specific conditions; soy protein is rich in amino acid residues and has multiple functional groups, which can react with other chemical components, providing higher binding ability and chemical activity for the composite material. In the process of preparing biomass adhesives, starch and soy protein are mixed and dispersed in deionized water, and heating causes the starch granules to undergo gelatinization, that is, the starch molecular chains unwind and swell under the action of water, and finally form a stable colloidal solution. At the same time, the soy protein molecules denature under heating conditions, exposing more reactive groups and enhancing their binding ability with other materials. In this invention, glutaraldehyde is introduced as a crosslinking agent. Glutaraldehyde is a chemical reagent with a dialdehyde structure, and the active aldehyde groups in its molecules can undergo aldehyde reactions with the hydroxyl and amino groups in starch and soy protein molecules, thus forming a stable crosslinked network. The result of this crosslinking reaction is to significantly enhance the physical properties of the adhesive, enabling it to more effectively load trace elements and adhere to the surface of biochar during the subsequent composite process. By mixing the trace element solution with the biomass adhesive, and using the functional groups in the adhesive molecules to chemically adsorb or coordinate with trace element ions, the trace elements can be stably bound inside the adhesive. In particular, the amino acid residues in soy protein can form coordination bonds with trace element ions, not only improving the loading efficiency of trace elements, but also significantly enhancing their stability and slow-release performance in the soil. The crosslinked network structure of the adhesive further restricts the diffusion rate of trace elements, enabling them to be slowly released in the soil, meeting the long-term needs of plant growth, and at the same time reducing the risk of trace element loss. In the process of preparing the composite synergist, the activated biochar and the adhesive-trace element solution are fully mixed by stirring. The porous structure and high specific surface area of biochar provide an ideal platform for the adhesion of the adhesive. The molecular chains in the adhesive can be embedded in the pores of biochar and achieve physical adsorption through van der Waals forces. The composite biochar-adhesive-trace element system not only has good mechanical stability, but also can achieve a slow-release function through its porous structure and crosslinked network. This slow-release characteristic enables trace elements to be gradually released in the soil, providing a continuous and stable nutrient source for plants, and avoiding the problems of fertilizer efficiency waste and environmental pollution caused by rapid release in traditional fertilizers.

[0020] As a highly stable aromatic polymer, lignin is distributed on the outer layer of cellulose and hemicellulose, forming a natural "protective barrier". It not only endows the plant cell wall with strength and resistance to degradation, but also effectively prevents cellulose and hemicellulose from being directly affected by external enzymes or microorganisms. The high cross-linking and chemical stability of this structure make lignocellulose difficult to degrade under conventional conditions. In the present invention, lignocellulose is pretreated by steam explosion technology. Under high-pressure conditions, steam can quickly penetrate into the interior of agricultural and forestry waste, and undergo physical and chemical interactions with lignin in the lignocellulose structure, resulting in partial softening and damage of lignin. This softening effect weakens the connection force between lignin and cellulose and hemicellulose, and increases the exposure degree of cellulose and hemicellulose. After the agricultural and forestry waste is treated by steam explosion, it is transferred to a sodium hydroxide solution for alkali treatment. Its main function is to further remove lignin and saponify part of hemicellulose at the same time, so as to improve the purity and enzymatic digestibility of cellulose. During the alkali treatment process, sodium hydroxide can break the aromatic ether bonds of lignin and decompose lignin into low-molecular-weight soluble fragments. In addition, the alkali solution can also act on the acetyl groups and other substituents of hemicellulose, promoting partial hydrolysis and depolymerization of hemicellulose to generate water-soluble oligosaccharides or monosaccharides. The alkali treatment not only further increases the exposure degree of cellulose, but also reduces the non-specific adsorption of lignin during the enzymatic hydrolysis process, thus improving the enzymatic hydrolysis efficiency. The structure of the alkali-soaked material is more loose, and the purity of cellulose is significantly improved, providing a high-quality substrate for the next enzymatic hydrolysis treatment. In the enzymatic hydrolysis step, a complex enzyme solution is added to further degrade cellulose and hemicellulose and release soluble sugars. The solute of the complex enzyme solution consists of three enzymes: cellulase, xylanase and pectinase. These enzymes can efficiently degrade cellulose, hemicellulose and pectin layers in lignocellulose through synergistic action. The action of pectinase is in the first stage of the enzymatic hydrolysis process. Its main function is to degrade the pectin layer in the plant cell wall, and this process destroys the integrity of the plant cell wall.

[0021] Based on the action of pectinase, xylanase mainly degrades the xylan backbone in hemicellulose. Xylan is one of the main components of hemicellulose. It degrades to produce xylooligosaccharides and monomeric xylose, and at the same time releases the hemicellulose covering layer on the surface of cellulose. The action of xylanase further exposes the cellulose molecular chain, enabling cellulase to act more effectively on cellulose. Cellulase is the core of the enzymatic hydrolysis process. Its main function is to decompose the cellulose molecular chain and depolymerize it into soluble cellobiose and glucose. The synergistic action of xylanase and pectinase in the complex enzyme solution provides sufficient action sites for cellulase, thus improving the depolymerization efficiency of cellulose. Through the synergistic action of pectinase, xylanase and cellulase, cellulose, hemicellulose and pectin in lignocellulose are efficiently degraded into soluble sugars, including glucose, xylose and oligosaccharides.

[0022] After steam explosion, alkali treatment, and enzymatic hydrolysis of agricultural and forestry waste, its originally highly complex and stable lignocellulose structure is destroyed, the encapsulation state of cellulose and hemicellulose is released, and a large amount of soluble sugars and oligosaccharides are released. These sugars not only provide a high-quality carbon source for the growth and reproduction of subsequent microorganisms but also improve the biodegradability of the waste. However, there are still residual lignin fragments and complex organic compounds in lignocellulose, and it is difficult to achieve complete degradation relying solely on the action of a single microorganism. Therefore, in the fermentation process, it is necessary to introduce a variety of functional microorganisms to complete the deep degradation of the material through stage-by-stage synergistic metabolism, while significantly enhancing the biological activity of the fermented material, making it have higher agricultural application value. The first-stage fermentation uses white rot fungi and soft rot fungi as the core microorganisms, and these two types of microorganisms play key roles in the degradation of lignin, cellulose, and hemicellulose respectively. As a fungus specialized in degrading lignin, the extremely important characteristic of white rot fungi is that they can secrete a series of non-specific oxidases, which can break the aromatic ring structure in lignin molecules through oxidation reactions, causing the originally stable aromatic ether bonds and phenylpropane side chains in lignin to break, and finally degrading lignin into low-molecular-weight organic acids, phenolic compounds, and other small-molecule products. The degradation of lignin not only releases the cellulose and hemicellulose encapsulated by it but also improves the physical structure of the material, increasing its looseness and enzymatic hydrolysis efficiency. Since the oxidases secreted by white rot fungi are non-specific, they have a certain degradation ability for various components in lignocellulose, thus providing a more accessible substrate for the action of subsequent microorganisms. The role of soft rot fungi is concentrated on the degradation of cellulose and hemicellulose. They can secrete cellulase and hemicellulase, and these enzymes cooperate to convert cellulose and hemicellulose into soluble sugars. At the same time, the hemicellulase secreted by soft rot fungi acts on the main chain and side chain of hemicellulose, degrading polysaccharide structures such as xylan and arabinose, thereby generating xylose, arabinose, and other monosaccharides or oligosaccharides. These enzymatic reactions not only reduce the molecular weight of cellulose and hemicellulose but also release a large amount of fermentable sugars, providing a rich carbon source for subsequent microbial metabolism. During the first-stage fermentation process, the lignin in the material is degraded, the degradation degree of cellulose and hemicellulose is also increased, and a large amount of low-molecular-weight organic acids, sugars, and other small-molecule substances are produced. These metabolites become high-quality substrates for the inoculation of second-stage microorganisms.

[0023] The second-stage fermentation uses Bacillus and Actinomycetes as the main microorganisms. Through their metabolic activities, they further degrade the complex organic matter remaining from the first-stage fermentation and generate a variety of secondary metabolites, thereby enhancing the biological activity of the fermented materials. Bacillus is a type of aerobic bacteria widely present in nature. Its metabolic characteristic is that it can secrete a variety of degrading enzymes (such as protease, amylase, and lipase) to deeply degrade organic matter. During the growth and metabolism of Bacillus, it can also synthesize a variety of bioactive secondary metabolites, such as plant growth hormones like indole-3-acetic acid. This hormone can promote the development of plant roots and enhance the plant's ability to absorb nutrients and water. In addition, Bacillus can also produce antibiotic compounds, which have broad-spectrum antibacterial activity and can inhibit the growth of pathogenic microorganisms, thereby endowing the organic fertilizer with certain biological control functions. Through this dual effect, Bacillus not only further degrades the complex organic matter in the materials but also enhances the plant growth-promoting function and disease resistance of the fermented materials. Actinomycetes, as a type of microorganism with both bacterial and fungal characteristics, have very strong metabolic activity and can degrade lignin derivatives, cellulose residues, and other complex macromolecular organic matters. The metabolic characteristic of Actinomycetes is to synthesize a large number of secondary metabolites, including a variety of compounds with antibacterial activity, which can effectively inhibit the reproduction of pathogenic bacteria in the soil, thereby improving the disease resistance effect of the organic fertilizer.

[0024] On the second day of the second-stage fermentation, chitosan-sepiolite-composite probiotic carrier, modified lignin-nano-clay slow-release factor, and composite synergist are added to the fermentation system. The addition of these functional additives further enhances the biological activity and slow-release performance of the fermented materials. Chitosan is an oligosaccharide compound with a biological stimulation effect, which can significantly enhance the growth and metabolic activity of microorganisms and at the same time improve the disease resistance of plants; sepiolite, as a natural porous mineral material, its porous structure can adsorb nutrients and slow down their release rate, thereby improving the nutrient utilization efficiency; the modified lignin-nano-clay factor further optimizes the nutrient stability during the fermentation process through its slow-release performance; the composite synergist enhances the overall biological activity and nutrient supply capacity of the fermented materials by providing additional functional components. In the later stage of the second-stage fermentation, the remaining cellulose and hemicellulose are further degraded to generate a large amount of polysaccharides, oligosaccharides, and other secondary metabolites, which significantly enhance the biological activity and disease resistance function of the fermented materials. At the same time, the addition of additives effectively improves the slow-release performance of the fermented materials, making the final product more in line with the requirements of high-efficiency biological organic fertilizers.

[0025] The temperature control of the three-stage fermentation is below 40°C, which can not only meet the long-term stable growth of functional microorganisms (such as probiotics, actinomycetes, and bacilli), but also avoid the possible volatile nitrogen loss and excessive decomposition of some organic matter under high-temperature conditions. In the high-temperature composting stage (S2), the fermentation process mainly focuses on the rapid decomposition of complex organic matter, often accompanied by intense metabolism, temperature rise, and rapid changes in the microbial metabolic community. In the low-temperature composting stage (S3), by controlling the temperature below 40°C, the fermentation process is more gentle and stable, and the functionality and maturity of the materials are significantly improved, thus providing a higher-quality substrate for the preparation of the final bio-organic fertilizer. The core goal of the three-stage composting is to further transform organic matter through the metabolic action of functional microorganisms under low-temperature conditions, while promoting the synthesis and accumulation of secondary metabolites. These secondary metabolites include important components such as polysaccharides, antibacterial substances, and plant growth stimulants, which can not only enhance the biological functionality of the materials but also further improve their actual effects during application. In the low-temperature composting stage, residual cellulose, hemicellulose, and lignin derivatives are gradually decomposed by functional microorganisms to generate low-molecular-weight organic substances. These low-molecular-weight compounds, such as organic acids, amino acids, and soluble polysaccharides, are not only the nutrient sources directly absorbable by plants but also have the effects of promoting soil microbial activity, improving soil physical and chemical properties, and enhancing soil fertility. Through the continuous metabolic activities of microorganisms, these chemical products are continuously accumulated and released into the materials, thereby improving the overall functionality and stability of the compost materials.

[0026] Within the first week of the three-stage fermentation, chitosan-sepiolite-composite probiotic carriers, modified lignin-nano-clay slow-release factors, and composite synergists are evenly added to the compost pile. As a natural oligosaccharide biological stimulant, chitosan has a wide range of effects in inducing plant disease resistance, enhancing microbial metabolic activity, and promoting the stability of the microbial community. The amino and hydroxyl groups in its molecular structure can bind to the surface of microbial cells, significantly enhancing the metabolic efficiency of microorganisms and inducing the activation of the plant immune system, thereby improving the plant's resistance to pathogenic microorganisms. The addition of chitosan can also promote the rapid proliferation of probiotics (such as bacilli and actinomycetes) in the compost pile, thus constructing a more stable and active microbial community. In addition, as a natural porous mineral material, sepiolite has a unique porous structure and a large specific surface area, enabling it to adsorb and fix a large number of nutrient molecules and delay the release rate of nutrients. This slow-release mechanism not only improves the utilization efficiency of nutrients but also avoids the premature loss of nutrients or environmental pollution. By combining chitosan with sepiolite to form a composite probiotic carrier, it can not only stabilize the environmental conditions for the survival of probiotics in the compost pile but also enhance the biological activity and functionality of the compost materials.

[0027] The addition of the modified lignin-nano clay slow-release factor further optimizes the nutrient dynamic balance of the compost materials. Modified lignin is a lignin derivative after chemical modification, with significantly enhanced surface activity and hydrophilicity, and can combine with nano clay to form a stable composite network structure. Due to its unique layered structure and extremely high specific surface area, nano clay has excellent nutrient adsorption capacity and can gradually release essential nutrients for plants such as nitrogen, phosphorus, and potassium through a slow-release mechanism. The existence of this slow-release network not only extends the validity period of nutrients in the soil but also ensures that plant roots can continuously obtain nutrient supply for a long time. In addition, the addition of the composite synergist further enhances the overall functionality of the compost materials. The composite synergist usually contains trace element solutions, biomass adhesives, and other active components. Among them, trace elements can promote the metabolic activities of microorganisms in the compost pile and improve the decomposition efficiency of organic matter; the biomass adhesive forms a stable network structure in the compost pile, enhancing the particle strength and anti-crushing performance of the materials, thus providing guarantee for the subsequent granulation and storage of fertilizers.

[0028] In the last week of the three-stage fermentation, sodium alginate solution is sprayed on the surface of the compost pile to further enhance the functionality and physical properties of the fermented materials. Sodium alginate is a natural polysaccharide polymer, and its molecular structure contains a large number of carboxyl and hydroxyl groups. These functional groups can complex with metal ions and nutrient molecules in the compost pile to form a stable gel network. This gel network has multiple functions. First, sodium alginate molecules can adsorb and fix nutrients such as nitrogen, phosphorus, and potassium in the compost pile and gradually release them into the soil through a slow-release mechanism, thus significantly improving the nutrient utilization efficiency. Second, the protective film formed by the sodium alginate solution on the surface of the compost pile can enhance the mechanical strength and water resistance of the particles, effectively preventing particle breakage during storage and transportation. In addition, as a natural biostimulant, the molecular structure of sodium alginate can interact with the cell walls or membranes of functional microorganisms in the compost pile, significantly promoting the metabolic activity of microorganisms and enhancing the stability of the microbial community, thus constructing a more persistent and functionally diverse microbial ecosystem. Finally, the sodium alginate solution has extremely high water absorption capacity, and its spraying treatment can significantly improve the water retention performance of the compost pile, improve the water retention ability of the materials in the soil, and further strengthen its soil improvement effect.

[0029] As a preferred technical solution of the present invention, in step A1, the particle size of the sepiolite powder < 50 μm.

[0030] In some alternative embodiments, the mass-volume ratio of the sepiolite powder to the hydrochloric acid solution is 1 kg: 2 L.

[0031] In some alternative embodiments, the mass fraction of the hydrochloric acid solution is 1 wt.%.

[0032] In some alternative embodiments, the mass-volume ratio of the sepiolite powder to the sodium hydroxide solution is 1 kg: 1 L.

[0033] In some alternative embodiments, the mass fraction of the sodium hydroxide solution is 1 wt.%.

[0034] In some alternative embodiments, the mass ratio of the sepiolite powder to the chitosan oligosaccharide is 10:1.

[0035] In some alternative embodiments, the mass-volume ratio of the chitosan oligosaccharide to water in the chitosan oligosaccharide solution is 1 kg: 10 L.

[0036] In some alternative embodiments, the stirring time is 1 - 2 h, for example, it can be 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2.0 h, but is not limited to the listed times, and other unlisted times within this time range are equally applicable.

[0037] In some alternative embodiments, the composite bacteria are lactic acid bacteria, yeast, and bacillus licheniformis, and the mass ratio is 2:2:1.

[0038] In some alternative embodiments, the volume-mass ratio of the composite bacteria solution to the chitosan-sepiolite composite matrix is 1 L: 5 kg.

[0039] In some alternative embodiments, the mass ratio of the composite bacteria to the chitosan-sepiolite composite matrix is 1:20.

[0040] As a preferred technical solution of the present invention, in step A2, the mass-volume ratio of the lignin powder to the deionized water is 1 kg: 10 L.

[0041] In some alternative embodiments, the first temperature is 50 - 60 °C, for example, it can be 50 °C, 51 °C, 52 °C, 53 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C or 60 °C, but is not limited to the listed temperatures, and other unlisted temperatures within this temperature range are equally applicable.

[0042] In some alternative embodiments, the stirring time at the first temperature is 30 - 50 min, for example, it can be 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, 46 min, 48 min or 50 min, but is not limited to the listed times, and other unlisted times within this time range are equally applicable.

[0043] In some alternative embodiments, the mass fraction of the sodium sulfite solution is 10 wt.%.

[0044] In some alternative embodiments, the mass-to-volume ratio of the modified lignin to deionized water in the modified lignin dispersion is 1 kg: 2 L.

[0045] In some alternative embodiments, the mass ratio of the lignin powder to sodium sulfite is 10:1.

[0046] In some alternative embodiments, the mass ratio of the lignin powder to epichlorohydrin is 100:3.

[0047] In some alternative embodiments, the mass-to-volume ratio of the montmorillonite to the activation solution is 1 kg: 10 L.

[0048] In some alternative embodiments, the activation solution is 1 wt.% hydrochloric acid and 2 wt.% urea, and the volume ratio is 1:1.

[0049] In some alternative embodiments, the time for stirring activation is 2 - 3 h. For example, it can be 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h, or 3.0 h. However, it is not limited to the listed times, and other unlisted times within this time range are equally applicable.

[0050] In some alternative embodiments, the mass ratio of the modified lignin to the nanoclay is 55:28.

[0051] In some alternative embodiments, the mass ratio of the modified lignin to the NPK solution is 55:15.

[0052] In some alternative embodiments, the mass ratio of nitrogen, phosphorus, and potassium in the NPK solution is 10:5:5.

[0053] In some alternative embodiments, the mass ratio of the modified lignin to glutaraldehyde is 55:2.

[0054] As a preferred technical solution of the present invention, in step A3, the carbon-rich biomass is straw, fruit wood chips, and rice husks, and the mass ratio is 5:3:2.

[0055] In some alternative embodiments, the second temperature is 500 - 550 °C. For example, it can be 500 °C, 505 °C, 510 °C, 515 °C, 520 °C, 525 °C, 530 °C, 535 °C, 540 °C, 545 °C, or 550 °C. However, it is not limited to the listed temperatures, and other unlisted temperatures within this temperature range are equally applicable.

[0056] In some alternative embodiments, the second temperature holding time is 2 - 3 h, for example, it can be 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h or 3.0 h, but is not limited to the listed times, and other unlisted times within this time range are equally applicable.

[0057] In some alternative embodiments, the mixed gas is nitrogen and oxygen, and the volume fraction ratio is 95:5.

[0058] In some alternative embodiments, the mass fraction of the hydrochloric acid solution is 1 wt.%.

[0059] In some alternative embodiments, the mass ratio of the starch to the soy protein is 2:1.

[0060] In some alternative embodiments, the mass - volume ratio of the starch to the deionized water is 1 kg:4 L.

[0061] In some alternative embodiments, the third temperature is 70 - 80 °C, for example, it can be 70 °C, 71 °C, 72 °C, 73 °C, 74 °C, 75 °C, 76 °C, 77 °C, 78 °C, 79 °C or 80 °C, but is not limited to the listed temperatures, and other unlisted temperatures within this temperature range are equally applicable.

[0062] In some alternative embodiments, the mass ratio of the starch to the glutaraldehyde is 10:1.

[0063] In some alternative embodiments, the solutes of the trace element solution are ferrous sulfate, boric acid, zinc sulfate and copper sulfate, and the mass ratio is 2:1:1:0.5, the solvent is deionized water, and the mass fraction is 18 wt.%.

[0064] In some alternative embodiments, the mass ratio of the trace element solution to the biomass adhesive is 1:8.

[0065] In some alternative embodiments, the mass ratio of the activated biochar to the adhesive - trace element solution is 1:2.

[0066] As a preferred technical solution of the present invention, in step S1, the time for pressurization and maintenance is 20 - 30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed times, and other unlisted times within this time range are equally applicable.

[0067] In some alternative embodiments, the alkali solution is a 2.5 wt.% sodium hydroxide solution.

[0068] In some alternative embodiments, the mass-volume ratio of the agricultural and forestry waste to the alkali solution is 1 kg: 3 L.

[0069] In some alternative embodiments, the first temperature holding time is 1 - 2 h. For example, it can be 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, or 2.0 h. However, it is not limited to the listed times, and other unlisted times within this time range are equally applicable.

[0070] In some alternative embodiments, the solutes in the composite enzyme solution are cellulase, xylanase, and pectinase, and the mass ratio is 2:1:1. The mass-volume ratio of the solutes to the deionized water solvent is 4 kg: 50 L.

[0071] In some alternative embodiments, the mass-volume ratio of the agricultural and forestry waste to the alkali solution is 14 kg: 1 L.

[0072] In some alternative embodiments, the fourth temperature is 50 - 55 °C. For example, it can be 50 °C, 50.5 °C, 51 °C, 51.5 °C, 52 °C, 52.5 °C, 53 °C, 53.5 °C, 54 °C, 54.5 °C, or 55 °C. However, it is not limited to the listed temperatures, and other unlisted temperatures within this temperature range are equally applicable.

[0073] As a preferred technical solution of the present invention, in step S2, the mass ratio of the white rot fungus, soft rot fungus, and the enzymolysis material is 5:3:900;

[0074] In some alternative embodiments, the one-stage fermentation period is 6 days;

[0075] In some alternative embodiments, the mass ratio of the enzymolysis material to the sterilized soybean meal is 9:1;

[0076] In some alternative embodiments, the mass ratio of the enzymolysis material, Bacillus, and Actinomycetes is 900:5:3;

[0077] In some alternative embodiments, the two-stage fermentation period is 4 days;

[0078] In some alternative embodiments, the mass ratio of the chitosan-sepiolite-composite probiotic carrier, modified lignin-nano clay sustained-release factor, composite synergist, and enzymolysis material is 30:40:25:900.

[0079] As a preferred technical solution of the present invention, in step S3, the three-stage period is 3 weeks.

[0080] In some alternative embodiments, the mass ratio of the chitosan-sepiolite-composite probiotic carrier, the modified lignin-nano clay slow-release factor, the composite synergist to the enzymatically hydrolyzed material in S1 is 5:7:4:90.

[0081] In some alternative embodiments, the mass fraction of the sodium alginate solution is 1 wt.%.

[0082] In some alternative embodiments, the mass ratio of the chitosan-sepiolite-composite probiotic carrier to the sodium alginate solution is 5:3.

[0083] In a second aspect, the present invention provides a multifunctional bio-organic fertilizer based on agricultural and forestry waste prepared by the preparation method described in the first aspect.

[0084] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0085] (1) The preparation of the chitosan-sepiolite-composite probiotic carrier enhances the nutrient adsorption and slow-release performance of sepiolite through acid-base activation and the loading of chitosan. At the same time, chitosan, as a biostimulant, can effectively promote the survival and activity of probiotics, enhancing the functionality of the fertilizer. The modified lignin-nano clay slow-release factor forms a stable nutrient slow-release network through lignin modification and the combination of nano clay, which can slowly release nutrients such as nitrogen, phosphorus, and potassium in the soil, improving the long-term effectiveness and utilization efficiency of the fertilizer;

[0086] (2) In the multi-stage composting fermentation process of the present invention, by inoculating functional microorganisms such as white rot fungi, soft rot fungi, Bacillus, and actinomycetes in stages, and utilizing their characteristics in aspects such as lignocellulose degradation, synthesis of disease-resistant substances, and secretion of plant growth-promoting substances, the biological activity and functionality of the composting materials are improved;

[0087] (3) By adding the chitosan-sepiolite-composite probiotic carrier, the modified lignin-nano clay slow-release factor, and the composite synergist, and combining with the treatment method of spraying the sodium alginate solution, the present invention constructs a stable network for multi-layer slow-release nutrients, which can achieve uniform release of nutrients, extend the nutrient supply cycle, and avoid soil pollution and runoff loss caused by excessive nutrient release. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 It is a flowchart of the preparation method of the multifunctional bio-organic fertilizer based on agricultural and forestry waste provided in Embodiments 1-4 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0089] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are all explanatory and exemplary and should not be construed as limiting the embodiments of the present invention and the protection scope of the present invention. Except for the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of the present application. These technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0090] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products and have not been further purified.

[0091] Example 1

[0092] This example provides a preparation method of a multifunctional bio-organic fertilizer based on agricultural and forestry waste. The preparation method specifically includes the following steps:

[0093] A1. Add 10 kg of sepiolite powder to 20 L of 1 wt.% hydrochloric acid solution and soak it. After filtration, add it to 10 L of 1 wt.% sodium hydroxide solution and soak it. Filter and wash with water to obtain activated sepiolite powder. Add 10 L of chitosan oligosaccharide solution to the activated sepiolite powder, adjust the pH to 8 and stir for 1.2 h. After suction filtration and drying, obtain chitosan oligosaccharide-sepiolite composite matrix. Then mix 2 L of composite bacterial solution with 10 kg of chitosan oligosaccharide-sepiolite composite matrix to obtain chitosan oligosaccharide-sepiolite-composite probiotic carrier;

[0094] A2. Disperse 5 kg of lignin powder in 50 L of deionized water, adjust the pH to 9, adjust the temperature to 55 °C and stir for 32 min. Then add 5 kg of sodium sulfite solution and 15 g of epichlorohydrin, filter and wash to obtain modified lignin. Disperse 1 kg of nano-montmorillonite in 10 L of activation solution, stir and activate for 2.2 h, then filter and wash to obtain nano-clay. Mix 16.5 kg of modified lignin dispersion with 2.8 kg of nano-clay, add 1.5 kg of NPK solution and mix evenly, then add 0.2 kg of glutaraldehyde and stir to obtain modified lignin-nano-clay slow-release factor;

[0095] A3. Transfer the carbon-rich biomass to a carbonization furnace, introduce a mixed gas, and heat it up to 510 °C for heat preservation for 2.6 h to obtain biochar. Immerse the biochar in a 1 wt.% hydrochloric acid solution and stir, then filter and wash to obtain activated biochar. Mix 2 kg of starch and 1 kg of soy protein and disperse them in 8 L of deionized water, heat it up to 77 °C to obtain a colloid, add 0.2 kg of glutaraldehyde and stir to obtain a biomass adhesive. Then mix 1 kg of trace element solution and 8 kg of biomass adhesive to obtain an adhesive-trace element solution. Mix 1 kg of activated biochar and 2 kg of adhesive-trace element solution, dry and crush to obtain a composite synergist;

[0096] S1. Load 90 kg of crushed agricultural and forestry waste into a high-pressure steam explosion tank and maintain it for 22 min, then instantaneously relieve the pressure to obtain steam-exploded material. Transfer the steam-exploded material to a 270 L, 2.5 wt.% sodium hydroxide solution for soaking, adjust the temperature to 55 °C and keep it to obtain alkali-soaked material. Add 5 L of composite enzyme solution to the alkali-soaked material, adjust the temperature to 51 °C, adjust the pH to 5, and stir to obtain enzymatically hydrolyzed material;

[0097] S2. Disperse 0.5 kg of white rot fungus and 0.3 kg of soft rot fungus in 90 kg of enzymatically hydrolyzed material and mix evenly. Turn the pile every 2 days within 6 days to obtain first-stage material. Mix the first-stage material with 10 kg of sterilized soybean meal, inoculate 0.5 kg of Bacillus and 0.3 kg of Actinomycetes, turn the pile every 2 days within 4 days, and add 3 kg of chitosan-sepiolite-composite probiotic carrier, 4 kg of modified lignin-nano clay sustained-release factor, and 2.5 kg of composite synergist on the second day to obtain second-stage material;

[0098] S3. When the temperature of the second-stage material pile drops below 40 °C, turn the pile once a week within 3 weeks. Add 5 kg of chitosan-sepiolite-composite probiotic carrier, 7 kg of modified lignin-nano clay sustained-release factor, and 4 kg of composite synergist and mix evenly in the first week within 3 weeks. Spray 3 kg of 1 wt.% sodium alginate solution in the last week within 3 weeks to obtain a multifunctional bio-organic fertilizer based on agricultural and forestry waste.

[0099] Example 2

[0100] This example provides a preparation method of a multifunctional bio-organic fertilizer based on agricultural and forestry waste. The preparation method specifically includes the following steps:

[0101] A1. Add 10 kg of sepiolite powder to 20 L of 1 wt.% hydrochloric acid solution for soaking. After filtration, add it to 10 L of 1 wt.% sodium hydroxide solution for soaking. Filter and wash with water to obtain activated sepiolite powder. Add 10 L of chitosan oligosaccharide solution to the activated sepiolite powder, adjust the pH to 8 and stir for 1.9 h. After suction filtration and drying, obtain the chitosan oligosaccharide-sepiolite composite matrix. Then mix 2 L of composite bacterial liquid with 10 kg of chitosan oligosaccharide-sepiolite composite matrix to obtain the chitosan oligosaccharide-sepiolite-composite probiotic carrier;

[0102] A2. Disperse 5 kg of lignin powder in 50 L of deionized water, adjust the pH to 9, adjust the temperature to 51 °C and stir for 48 min. Then add 5 kg of sodium sulfite solution and 15 g of epichlorohydrin, filter and wash to obtain modified lignin. Disperse 1 kg of nano-montmorillonite in 10 L of activation solution, stir and activate for 2.7 h, then filter and wash to obtain nano-clay. Mix 16.5 kg of modified lignin dispersion with 2.8 kg of nano-clay, add 1.5 kg of NPK solution and mix evenly. Then add 0.2 kg of glutaraldehyde and stir to obtain the modified lignin-nano-clay slow-release factor;

[0103] A3. Transfer the carbon-rich biomass to a carbonization furnace, introduce a mixed gas and heat up to 550 °C for heat preservation for 2.1 h to obtain biochar. Immerse the biochar in 1 wt.% hydrochloric acid solution and stir, filter and wash to obtain activated biochar. Mix 2 kg of starch and 1 kg of soy protein and disperse them in 8 L of deionized water, heat up to 71 °C to obtain a colloid. Add 0.2 kg of glutaraldehyde and stir to obtain the biomass adhesive. Then mix 1 kg of trace element solution with 8 kg of biomass adhesive to obtain the adhesive-trace element solution. Mix 1 kg of activated biochar with 2 kg of adhesive-trace element solution, dry and crush to obtain the composite synergist;

[0104] S1. Load 90 kg of crushed agricultural and forestry waste into a high-pressure steam explosion tank and maintain for 29 min. Instantly release the pressure to obtain the steam explosion material. Transfer the steam explosion material to 270 L of 2.5 wt.% sodium hydroxide solution for soaking, adjust the temperature to 51 °C and keep it to obtain the alkali-soaked material. Add 5 L of composite enzyme solution to the alkali-soaked material, adjust the temperature to 52 °C, adjust the pH to 5, and stir to obtain the enzymolysis material;

[0105] S2. Disperse 0.5 kg of white rot fungus and 0.3 kg of soft rot fungus in 90 kg of enzymolysis material and mix evenly. Turn the pile every 2 days within 6 days to obtain the first-stage material. Mix the first-stage material with 10 kg of sterilized soybean meal, inoculate 0.5 kg of Bacillus and 0.3 kg of Actinomycetes, turn the pile every 2 days within 4 days, and add 3 kg of chitosan oligosaccharide-sepiolite-composite probiotic carrier, 4 kg of modified lignin-nano-clay slow-release factor and 2.5 kg of composite synergist on the second day to obtain the second-stage material;

[0106] S3. When the temperature of the second-stage material heap drops below 40 °C, turn the heap once a week for 3 weeks. In the first week within 3 weeks, uniformly mix 5 kg of chitosan-sepiolite-composite probiotic carrier, 7 kg of modified lignin-nano-clay slow-release factor, and 4 kg of composite synergist. In the last week within 3 weeks, spray 3 kg of 1 wt.% sodium alginate solution to obtain a multifunctional bio-organic fertilizer based on agricultural and forestry waste.

[0107] Example 3

[0108] This example provides a preparation method for a multifunctional bio-organic fertilizer based on agricultural and forestry waste. The preparation method specifically includes the following steps:

[0109] A1. Add 10 kg of sepiolite powder to 20 L of 1 wt.% hydrochloric acid solution for soaking. After filtration, add it to 10 L of 1 wt.% sodium hydroxide solution for soaking, filter and wash with water to obtain activated sepiolite powder. Add 10 L of chitosan solution to the activated sepiolite powder, adjust the pH to 8 and stir for 1.6 h. After suction filtration and drying, obtain chitosan-sepiolite composite matrix. Then mix 2 L of composite bacterial solution with 10 kg of chitosan-sepiolite composite matrix to obtain chitosan-sepiolite-composite probiotic carrier;

[0110] A2. Disperse 5 kg of lignin powder in 50 L of deionized water, adjust the pH to 9, adjust the temperature to 59 °C and stir for 46 min. Then add 5 kg of sodium sulfite solution and 15 g of epichlorohydrin, filter and wash to obtain modified lignin. Disperse 1 kg of nano-montmorillonite in 10 L of activation solution, stir and activate for 2.1 h, then filter and wash to obtain nano-clay. Mix 16.5 kg of modified lignin dispersion with 2.8 kg of nano-clay, add 1.5 kg of NPK solution and mix evenly, then add 0.2 kg of glutaraldehyde and stir to obtain modified lignin-nano-clay slow-release factor;

[0111] A3. Transfer the carbon-rich biomass to a carbonization furnace, introduce a mixed gas and heat up to 540 °C for heat preservation for 2.4 h to obtain biochar. Immerse the biochar in 1 wt.% hydrochloric acid solution and stir, filter and wash to obtain activated biochar. Mix 2 kg of starch and 1 kg of soy protein and disperse them in 8 L of deionized water, heat up to 75 °C to obtain a colloid, add 0.2 kg of glutaraldehyde and stir to obtain a biomass adhesive. Then mix 1 kg of trace element solution with 8 kg of biomass adhesive to obtain an adhesive-trace element solution. Mix 1 kg of activated biochar with 2 kg of adhesive-trace element solution, dry and crush to obtain a composite synergist;

[0112] S1. Load 90 kg of crushed agricultural and forestry waste into a high-pressure steam explosion tank and maintain for 24 min. Instantly release the pressure to obtain steam-exploded material. Transfer the steam-exploded material to a 270 L, 2.5 wt.% sodium hydroxide solution for soaking. Adjust the temperature to 59 °C and maintain it to obtain alkali-soaked material. Add 5 L of complex enzyme solution to the alkali-soaked material, adjust the temperature to 55 °C, adjust the pH to 5, and stir to obtain enzymatically hydrolyzed material;

[0113] S2. Disperse 0.5 kg of white rot fungi and 0.3 kg of soft rot fungi in 90 kg of enzymatically hydrolyzed material and mix evenly. Turn the pile every 2 days within 6 days to obtain first-stage material. Mix the first-stage material with 10 kg of sterilized soybean meal, inoculate 0.5 kg of Bacillus and 0.3 kg of Actinomycetes, turn the pile every 2 days within 4 days, and add 3 kg of chitosan-sepiolite-compound probiotic carrier, 4 kg of modified lignin-nano clay slow-release factor, and 2.5 kg of compound synergist on the second day to obtain second-stage material;

[0114] S3. When the temperature of the second-stage material pile drops below 40 °C, turn the pile once a week within 3 weeks. Add 5 kg of chitosan-sepiolite-compound probiotic carrier, 7 kg of modified lignin-nano clay slow-release factor, and 4 kg of compound synergist and mix evenly in the first week within 3 weeks. Spray 3 kg of 1 wt.% sodium alginate solution in the last week within 3 weeks to obtain a multifunctional bio-organic fertilizer based on agricultural and forestry waste.

[0115] Example 4

[0116] This example provides a preparation method of a multifunctional bio-organic fertilizer based on agricultural and forestry waste. The preparation method specifically includes the following steps:

[0117] A1. Add 10 kg of sepiolite powder to a 20 L, 1 wt.% hydrochloric acid solution for soaking. After filtration, add it to a 10 L, 1 wt.% sodium hydroxide solution for soaking. Filter and wash with water to obtain activated sepiolite powder. Add 10 L of chitosan solution to the activated sepiolite powder, adjust the pH to 8 and stir for 1.4 h. After suction filtration and drying, obtain chitosan-sepiolite composite matrix. Then mix 2 L of complex bacteria solution with 10 kg of chitosan-sepiolite composite matrix to obtain chitosan-sepiolite-compound probiotic carrier;

[0118] A2. Disperse 5 kg of lignin powder in 50 L of deionized water, adjust the pH to 9, adjust the temperature to 57 °C and stir for 40 min. Then add 5 kg of sodium sulfite solution and 15 g of epichlorohydrin, filter and wash to obtain modified lignin. Disperse 1 kg of nano-montmorillonite in 10 L of activation solution, stir and activate for 2.5 h, then filter and wash to obtain nano-clay. Mix 16.5 kg of modified lignin dispersion with 2.8 kg of nano-clay, add 1.5 kg of NPK solution and mix evenly. Then add 0.2 kg of glutaraldehyde and stir to obtain modified lignin-nano-clay slow-release factor;

[0119] A3. Transfer the carbon-rich biomass to a carbonization furnace, heat it to 530 °C and hold for 2.9 h after introducing the mixed gas to obtain biochar. Immerse the biochar in 1 wt.% hydrochloric acid solution and stir, filter and wash to obtain activated biochar. Mix 2 kg of starch and 1 kg of soy protein and disperse them in 8 L of deionized water, heat to 79 °C to obtain a colloid, add 0.2 kg of glutaraldehyde and stir to obtain a biomass adhesive. Then mix 1 kg of trace element solution with 8 kg of biomass adhesive to obtain an adhesive-trace element solution. Mix 1 kg of activated biochar with 2 kg of adhesive-trace element solution, dry and crush to obtain a composite synergist;

[0120] S1. Load 90 kg of crushed agricultural and forestry waste into a high-pressure steam explosion tank and maintain for 20 min, then instantaneously release the pressure to obtain steam-exploded material. Transfer the steam-exploded material to a 270 L, 2.5 wt.% sodium hydroxide solution for soaking, adjust the temperature to 57 °C and keep it to obtain alkali-soaked material. Add 5 L of composite enzyme solution to the alkali-soaked material, adjust the temperature to 53 °C, adjust the pH to 5, and stir to obtain enzymolysis material;

[0121] S2. Disperse 0.5 kg of white rot fungus and 0.3 kg of soft rot fungus in 90 kg of enzymolysis material and mix evenly. Turn the pile every 2 days within 6 days to obtain first-stage material. Mix the first-stage material with 10 kg of sterilized soybean meal, inoculate 0.5 kg of Bacillus and 0.3 kg of Actinomycetes, turn the pile every 2 days within 4 days. Add 3 kg of chitosan-sepiolite-composite probiotic carrier, 4 kg of modified lignin-nano-clay slow-release factor and 2.5 kg of composite synergist on the second day to obtain second-stage material;

[0122] S3. When the temperature of the second-stage material pile drops below 40 °C, turn the pile once a week within 3 weeks. Add 5 kg of chitosan-sepiolite-composite probiotic carrier, 7 kg of modified lignin-nano-clay slow-release factor and 4 kg of composite synergist and mix evenly in the first week within 3 weeks. Spray 3 kg of 1 wt.% sodium alginate solution in the last week within 3 weeks to obtain a multifunctional bio-organic fertilizer based on agricultural and forestry waste.

[0123] Comparative Example 1

[0124] This comparative example provides a method for preparing a multifunctional bio-organic fertilizer based on agricultural and forestry waste. The difference from Example 1 is that the mass of the modified lignin-nano-clay slow-release factor in S3 is 1 kg, which is 6 kg less than that in Example 1, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0125] Comparative Example 2

[0126] This comparative example provides a method for preparing a multifunctional bio-organic fertilizer based on agricultural and forestry waste. The difference from Example 1 is that the mass of the modified lignin-nano-clay slow-release factor in S3 is 14 kg, which is 7 kg more than that in Example 1, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0127] Comparative Example 3

[0128] This comparative example provides a method for preparing a multifunctional bio-organic fertilizer based on agricultural and forestry waste. The difference from Example 1 is that the mass of the chitosan-sepiolite-composite probiotic carrier in S2 and S3 is 0, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0129] Test plants: Tobacco variety K326. Test soil: No base fertilizer is applied in the early stage, and the soil is neutral or weakly acidic. Fertilization method: (1) Base fertilizer: 7 days before transplanting, apply the prepared organic fertilizer, spread it directly and mix it evenly by shallow tillage; (2) Top dressing: According to the growth stage characteristics of tobacco (such as the rosette stage), apply organic fertilizer once during the rosette stage of tobacco, using furrow application or hole application; (3) Dosage: Uniformly convert the total amounts of nitrogen, phosphorus, and potassium according to the nutrient content of each fertilizer to ensure that the total amounts of nitrogen, phosphorus, and potassium are the same among different treatments. Test area: Each plot has an area of 10 m 2 (width 2 m × length 5 m), with a 1 m wide isolation belt between plots to prevent water and fertilizer interference. Experimental management: (1) Uniformly water the tobacco seedlings thoroughly before transplanting to ensure the consistency of the seedlings; (2) Water uniformly and moderately according to the water requirement law of tobacco growth to avoid being too dry or too wet; (3) Conduct pest and disease control uniformly in the test area to avoid the influence of external factors on the test results; (4) Weed in time to keep the test area clean. When the test tobacco enters the topping stage, measure the data of tobacco plant height, stem girth, effective leaves, maximum leaf length, and maximum leaf width. The test results are shown in Table 1.

[0130] Table 1 Test results of the multifunctional bio-organic fertilizers based on agricultural and forestry waste prepared in Examples 1-4 and Comparative Examples 1-2

[0131] Plant height (cm) Stem girth (cm) Effective leaves (pcs) Maximum leaf length (cm) Maximum leaf width (cm) Example 1 124.8 10.1 15.8 72.5 33.3 Example 2 120.4 10.9 15.3 73.7 31.2 Example 3 123.9 11.3 16.1 75.1 34.9 Example 4 126.1 9.7 15.6 72.4 35.6 Comparative example 1 117.2 8.8 15.1 70.6 30.5 Comparative example 2 111.9 8.5 14.9 68.9 29.7 Comparative example 3 112.5 7.7 14.3 62.1 28.2

[0132] As can be seen from Table 1, the plant height, stem girth, effective leaves, maximum leaf length and maximum leaf width of Comparative Example 1 are all lower than those of Example 1; the plant height, stem girth, effective leaves, maximum leaf length and maximum leaf width of Comparative Example 2 are all lower than those of Example 1; the plant height, stem girth, effective leaves, maximum leaf length and maximum leaf width of Comparative Example 3 are all lower than those of Example 1. This is because the dosage of the modified lignin-nano clay slow-release factor in Comparative Example 1 is insufficient, and the available nitrogen, phosphorus and potassium in the soil cannot be fully fixed, and are easily lost through leaching, volatilization and other ways, resulting in serious nutrient loss. In Comparative Example 2, the modified lignin-nano clay slow-release factor is excessive, and the layered structure of nano clay and the high adsorption performance of modified lignin may over-adsorb soluble nutrients (such as ammonium nitrogen, phosphate radical) in the soil, resulting in a decrease in the effectiveness of nutrients in the soil. The chitosan-sepiolite-composite probiotic carrier has adsorption performance and slow-release ability, and also has the functions of enhancing microbial activity and biostimulation. In Comparative Example 3, the mass of the chitosan-sepiolite-composite probiotic carrier is 0, and the available nitrogen, phosphorus and potassium in the soil cannot be fully fixed, resulting in serious nutrient loss.

[0133] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived within the technical scope disclosed by the present invention by those skilled in the art all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a multifunctional bio-organic fertilizer based on agricultural and forestry waste, characterized in that, The preparation method includes: S1. Loading agricultural and forestry waste into a high-pressure steam explosion tank to obtain steam-exploded materials, transferring the steam-exploded materials to an alkali solution to obtain alkali-soaked materials, and adding a composite enzyme solution to the alkali-soaked materials to obtain enzymatically hydrolyzed materials; S2. Dispersing white rot fungi and soft rot fungi in the enzymatically hydrolyzed materials to obtain first-stage materials, mixing the first-stage materials with sterilized soybean meal, inoculating Bacillus and Actinomycetes, and adding a chitosan-sepiolite-composite probiotic carrier, a modified lignin-nano-clay slow-release factor, and a composite synergist to obtain second-stage materials; S3. When the pile temperature of the second-stage materials drops below 40 °C, adding a chitosan-sepiolite-composite probiotic carrier, a modified lignin-nano-clay slow-release factor, and a composite synergist and mixing them, and spraying a sodium alginate solution to obtain a multifunctional bio-organic fertilizer based on agricultural and forestry waste.

2. The preparation method of the multifunctional biological organic fertilizer based on agricultural and forestry waste according to claim 1, characterized in that The preparation method of the chitosan-sepiolite-composite probiotic carrier and the modified lignin-nano-clay slow-release factor includes: A1. Soaking sepiolite powder in hydrochloric acid solution and sodium hydroxide solution to obtain activated sepiolite powder, adding a chitosan solution to the activated sepiolite powder to obtain a chitosan-sepiolite composite matrix, and then mixing a composite bacterial solution with the chitosan-sepiolite composite matrix to obtain a chitosan-sepiolite-composite probiotic carrier; A2. Dispersing lignin powder in deionized water, adding sodium sulfite solution and epichlorohydrin to obtain modified lignin, dispersing nano-montmorillonite in an activation solution to obtain nano-clay, mixing the modified lignin dispersion with the nano-clay, and adding NPK solution and glutaraldehyde to obtain a modified lignin-nano-clay slow-release factor.

3. The preparation method of the multifunctional bio-organic fertilizer based on agricultural and forestry waste according to claim 1, wherein, The preparation method of the composite synergist includes: A3. Transferring carbon-rich biomass to a carbonization furnace to obtain biochar, immersing the biochar in hydrochloric acid solution to obtain activated biochar, mixing starch and soy protein and adding glutaraldehyde to obtain a biomass adhesive, mixing a trace element solution with the biomass adhesive to obtain an adhesive-trace element solution, and mixing the activated biochar with the adhesive-trace element solution to obtain a composite synergist.

4. The preparation method of the multifunctional biological organic fertilizer based on agricultural and forestry waste according to claim 1, characterized in that, In S1, the alkali solution is a 2.5 wt.% sodium hydroxide solution; the solutes in the composite enzyme solution are cellulase, xylanase, and pectinase, and the mass ratio is 2:1:1, and the mass-volume ratio of the solute to the solvent deionized water is 4 kg:50 L.

5. The preparation method of the multifunctional bio-organic fertilizer based on agricultural and forestry waste according to claim 1, characterized in that, In S2, the mass ratio of the white rot fungi, soft rot fungi, and the enzymatically hydrolyzed materials is 5:3:900; the mass ratio of the enzymatically hydrolyzed materials, Bacillus, and Actinomycetes is 900:5:3; the mass ratio of the chitosan-sepiolite-composite probiotic carrier, the modified lignin-nano-clay slow-release factor, the composite synergist, and the enzymatically hydrolyzed materials is 30:40:25:

900.

6. The preparation method of the multifunctional biological organic fertilizer based on agricultural and forestry waste according to claim 1, wherein, In S3, the mass ratio of the chitosan-sepiolite-composite probiotic carrier, the modified lignin-nano-clay slow-release factor, the composite synergist, and the enzymatically hydrolyzed materials in S1 is 5:7:4:90; the mass fraction of the sodium alginate solution is 1 wt.%.

7. The preparation method of the multifunctional bio-organic fertilizer based on agricultural and forestry waste according to claim 2, characterized in that, In A1, the mass ratio of the sepiolite powder to chitosan is 10:1; the composite bacteria are Lactobacillus, Saccharomyces cerevisiae, and Bacillus licheniformis, and the mass ratio is 2:2:1; The mass ratio of the composite bacteria to the chitosan oligosaccharide-sepiolite composite matrix is 1:

20.

8. The preparation method of the multifunctional bio-organic fertilizer based on agricultural and forestry waste according to claim 2, characterized in that, In A2, The mass ratio of the modified lignin to the nano clay is 55:28; The mass ratio of the modified lignin to the NPK solution is 55:15; The mass ratio of nitrogen, phosphorus and potassium in the NPK solution is 10:5:

5.

9. The preparation method of the multifunctional bio-organic fertilizer based on agricultural and forestry waste according to claim 3, characterized in that, In A3, The solute of the trace element solution is ferrous sulfate, boric acid, zinc sulfate and copper sulfate, and the mass ratio is 2:1:1:0.

5. The solvent is deionized water, and the mass fraction is 18 wt.%; The mass ratio of the trace element solution to the biomass adhesive is 1:8; The mass ratio of the activated biochar to the adhesive-trace element solution is 1:

2.

10. The multifunctional bio-organic fertilizer based on agricultural and forestry waste obtained by the preparation method according to any one of claims 1-9.

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