Composting method based on compound microbial agent and photo-biological synergistic effect

Abstract

The invention discloses a composting method based on a compound microbial agent and a light-biological synergistic effect, and belongs to the technical field of recycling of agricultural and forestry wastes and livestock manure. The compound microbial agent consists of the following strains: white-rot fungi accounting for 25-35% of the total viable count; the high-temperature actinomycetes account for 15-20% of the total viable count; nitrogen-fixing bacteria accounting for 25-30% of the total viable count; the auxiliary flora accounts for 10-20% of the total viable count; the total concentration of the microbial inoculum is (50-80) * 10 < 8 > CFU / g, and the microbial inoculum is embedded by using a sodium alginate-charcoal-montmorillonite composite microcapsule. 0.3-0.5% of riboflavin and 0.1-0.3% of ferrous sulfate heptahydrate are added according to the dry weight of the compost to serve as a photocatalytic system, and meanwhile 5-8% of phosphoric acid modified charcoal is added to fix nitrogen and preserve fertilizer. The light degradation reaction of the lignin can be initiated under a natural illumination condition. By adjusting the pile height and the pile turning frequency, uniform distribution of illumination is ensured, the lignin degradation rate is increased by 40-50%, and the nitrogen retention effect is outstanding.

Description

Technical Field

[0001] This invention belongs to the field of agricultural and forestry waste and livestock manure resource utilization technology, specifically involving a composting method based on compound microbial agents and photo-biological synergy, which is particularly suitable for the resource utilization of recalcitrant agricultural and forestry waste. Background Technology

[0002] Existing technologies for composting agricultural and forestry waste and livestock manure face the following technical bottlenecks: 1) Incomplete lignin degradation: Current technologies have limited ability to disrupt the lignin structure, making it difficult to fully release the encapsulated cellulose and hemicellulose. In traditional composting methods, lignin, as the most stubborn component, typically degrades at a rate of less than 30%, leading to a composting cycle of 60-90 days. Research from Beijing Forestry University shows that even with the addition of conventional microbial agents, the lignin content decreases by only 16% within 30 days, far from meeting the requirements for efficient composting. While existing technologies attempt to improve degradation efficiency by adding coumarin and bone char as composite photocatalysts, these methods rely on specific UV-A band filters, making operation complex and costly, and difficult to promote and apply under natural conditions.

[0003] 2) Severe nitrogen loss: In traditional composting, ammonia volatilization leads to a nitrogen loss rate as high as 25%-40%, which not only reduces the fertilizer efficiency of compost products, but also causes environmental pollution.

[0004] 3) Inefficient process control: Existing technologies rely heavily on experience or single parameters (such as temperature) for control such as turning and watering, making it difficult to achieve synergistic optimization of multiple parameters such as temperature, oxygen, humidity, and C / N ratio during composting, resulting in unstable compost quality. Poor adaptability to natural conditions limits the promotion and application of existing technologies.

[0005] 4) High process complexity: Most patented technologies require the construction of special reactors or rely on precision equipment, making them difficult to implement in rural areas lacking infrastructure. Although microporous membrane devices are designed for individual farmers, they still require a certain amount of equipment investment. Furthermore, low-cost, high-efficiency technical solutions suitable for natural composting conditions are clearly insufficient. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a composting method based on the synergistic effect of composite microbial agents and photo-biological processes, which significantly improves the degradation efficiency of lignocellulose, enhances nitrogen retention, provides precise and intelligent process control, exhibits strong environmental adaptability, and is cost-effective.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A composting method based on the synergistic effect of compound microbial agents and photo-biological processes includes the following steps: a) Raw material pretreatment: Crush agricultural and forestry waste and mix it with poultry and livestock manure at a dry weight ratio of (6.5 - 7.5):(2.5 - 3.5), adjust the initial carbon-nitrogen ratio of the mixture to 28-32:1, and the moisture content to 55-60%; b) Adding a photocatalytic system: Add 0.3-0.5% of riboflavin, 0.1-0.3% of ferrous sulfate heptahydrate, and 5-8% of phosphoric acid-modified biochar by dry weight of the mixture obtained in step a), and mix thoroughly. c) Inoculation with microbial agent: When the temperature of the pile naturally rises to 50-55℃, inoculate 1.0-1.5% of microcapsules containing compound microbial agent by dry weight of the mixture; then stack the material into a windrow pile. d) Covering and Process Control: The surface of the pile is covered with a three-layer structure, from the inside out: a breathable non-woven fabric layer, a biodegradable heat-insulating film layer, and a shading net layer; the timing of turning the pile is dynamically controlled based on three indicators: laccase activity, redox potential, and volatile fatty acid concentration, and the moisture content and C / N ratio are dynamically adjusted; the pH value of the pile is maintained between 6.5 and 7.5, and the moisture content is controlled between 55% and 65%; e) When laccase activity > 200 U / g, ORP < -100 mV and VFA concentration > 800 mg / kg, perform the turning operation.

[0008] Optionally, the compound microbial agent comprises the following strains: white-rot fungi, accounting for 25-35% of the total viable bacteria; thermophilic actinomycetes, accounting for 15-20% of the total viable bacteria; nitrogen-fixing bacteria, accounting for 25-30% of the total viable bacteria; and auxiliary bacteria, accounting for 10-20% of the total viable bacteria; the total concentration of the agent is 50–80 × 10⁻⁶. 8 CFU / g, and encapsulated using sodium alginate-biochar-montmorillonite composite microcapsules.

[0009] Optionally, the nitrogen-fixing bacteria are Japanese slow-growing rhizobium SEMIA 5079 or SEMIA 5080; the auxiliary bacteria are phosphate-solubilizing bacteria and extracellular polysaccharide-producing bacteria, and the ratio of viable phosphate-solubilizing bacteria to extracellular polysaccharide-producing bacteria is 1.2:1-1.5:1.

[0010] Optionally, the preparation steps of the sodium alginate-biochar-montmorillonite composite microcapsules encapsulating the aforementioned composite microbial agent include: (1) Weigh a certain amount of sodium alginate, slowly add it to boiling sterile deionized water, stir magnetically to dissolve it completely, prepare a 2.5% clear solution, autoclave at 121℃ for 20 minutes, and cool to room temperature for later use. (2) Grind the phosphoric acid-modified biochar and pass it through a 150-mesh sieve to obtain ultrafine powder. Place it in a drying oven and sterilize it at 160°C for 2 hours. In a sterile operating table, mix the sterilized montmorillonite powder and biochar powder in a mass ratio of 1:3. (3) The above mixture is slowly added to a cooled 2.5% sodium alginate solution, wherein the total mass of the mixture and the mass ratio of sodium alginate solids is 1:1-1.5:1; it is dispersed under ice bath conditions to form sodium alginate-biochar-montmorillonite composite carrier colloid. (4) Take a high-concentration compound bacterial suspension and slowly add it to the compound carrier gel while stirring to ensure that the bacteria are evenly dispersed. The total bacterial concentration of the final mixture should reach 50–80 × 10⁻⁶. 8 CFU / g; the gel is dropped into a sterile 0.1 mol / L calcium chloride solution at a constant rate to form spherical or ellipsoidal microcapsules.

[0011] Optionally, the agricultural and forestry waste is one or more of branches, straw, and rice husks mixed in any proportion; the poultry and livestock manure is one or more of pig manure or chicken manure mixed in any proportion.

[0012] Optionally, in step c), the base width of the windrow stack is 2.0-2.5 m and the height is 1.0-1.3 m.

[0013] Optionally, in step d), a shading net layer with a shading rate of 40-50% is used.

[0014] Optionally, the method for preparing the phosphoric acid modified biochar includes the following steps: (1) Use a phosphoric acid solution with a mass fraction of 30%-60%, mix the biomass raw material with the phosphoric acid solution at a 1:1 impregnation ratio, and impregnate at room temperature for 12-24 hours; (2) Transfer the impregnated mixture to a muffle furnace or tube furnace and pyrolyze it under an inert atmosphere at a temperature of 500°C for 1-2 hours. (3) After pyrolysis, wait for the furnace to cool naturally to room temperature, and wash the carbon particles repeatedly with deionized water or distilled water until the pH of the washing solution is close to neutral. (4) Place the washed biochar in an oven at 105°C and dry it to constant weight. Grind it and pass it through a 100-mesh sieve for later use.

[0015] Furthermore, the biomass raw material is one or two of the following: reeds, straw, and stalks, mixed in any proportion.

[0016] A compost product prepared by the aforementioned composting method has a lignin degradation rate of ≥50%, a total nitrogen retention rate of ≥80%, and a germination index of ≥95%.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) Significantly improved lignocellulose degradation efficiency: The innovative ternary compound microbial agent (white-rot fungi + thermophilic actinomycetes + nitrogen-fixing bacteria) of this invention constructs a functionally complementary degradation network. White-rot fungi preferentially degrade lignin, exposing cellulose and hemicellulose; thermophilic actinomycetes efficiently degrade exposed cellulose during the high-temperature period; nitrogen-fixing bacteria not only reduce nitrogen loss, but their metabolites also stimulate the activity of other strains. Combined with riboflavin / Fe 2+ The visible light catalytic system of hematite continuously generates reactive oxygen free radicals under natural light to attack lignin macromolecules, increasing the lignin degradation rate from <35% in traditional methods to ≥50%, and shortening the composting cycle from 60-90 days to less than 40 days.

[0018] (2) Excellent nitrogen retention: The biological nitrogen fixation of Azotobacter chrysoprase directly fixes nitrogen in the air, while phosphoric acid modified biochar effectively retains ammonium ions (NH4+). 4+ The powerful adsorption of nitrogen, along with intelligent regulation to avoid excessive high temperatures and frequent turning, and multiple measures working together, have reduced the nitrogen loss rate from 40-50% to below 20%, significantly improving the fertilizer value of compost products.

[0019] (3) Precise and intelligent process control: Based on the linkage control model of three biological / chemical indicators such as laccase activity, ORP and VFA concentration, it replaces the traditional experience or single temperature control mode, realizes the optimal judgment of the turning time, ensures that the pile is always in the best biological reaction state, and improves the stability of compost quality and product maturity (germination index GI≥95%).

[0020] (4) Strong environmental adaptability and low cost: The entire system design fully considers the application scenarios in rural areas. No special reactor, external UV light source or expensive additives are required; the microbial agent adopts microencapsulation technology, which has a long shelf life and strong resistance; the three-layer covering structure of the stack provides heat preservation and moisture retention and regulates light, adapting to various climatic conditions. This invention has the advantages of low investment, low operating cost and simple operation and management, and is very suitable for promotion and application in the vast rural areas of my country. Attached Figure Description

[0021] Figure 1 The graph shows the change in lignin degradation rate over time during the composting process, comparing Example 1 with the control example.

[0022] Figure 2 The graph shows the change in cellulose degradation rate over time during the composting process, comparing Example 1 with the control example. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] A compound microbial inoculant for composting agricultural and forestry waste and livestock manure comprises the following strains: white-rot fungi, *Trametes versicolor* (standard strain ATCC 20869), accounting for 25-35% of the total viable count; thermophilic actinomycetes, *Thermobifida fusca* (standard strain ATCC 20869), accounting for 15-20% of the total viable count; nitrogen-fixing bacteria, *SEMIA 5079* or *SEMIA 5080*, accounting for 25-30% of the total viable count; and auxiliary bacteria, including phosphate-solubilizing bacteria (*Bacillus megaterium*) and exopolysaccharide-producing bacteria (*Xanthomonas campestris*), with a viable count ratio of phosphate-solubilizing bacteria to exopolysaccharide-producing bacteria of 1.2:1-1.5:1, accounting for 10-20% of the total viable count; the total concentration of the inoculant is 50–80 × 10⁻⁶. 8 CFU / g, and encapsulated using sodium alginate-biochar-montmorillonite composite microcapsules.

[0025] In this invention, slightly increasing the proportion of phosphate-solubilizing bacteria ensures the rapid and effective release of phosphorus sources, providing a fundamental nutritional guarantee for the "explosive" growth of the entire microbial community (especially the main bacteria that degrade lignocellulose). The proportion of extracellular polysaccharide-producing bacteria should not be too low. If EPS (extracellular polymeric substances secreted by microorganisms such as bacteria, fungi, and algae during their growth and metabolism) production is insufficient, the pile structure cannot be effectively improved. If the proportion of extracellular polysaccharide-producing bacteria is too high, it may excessively consume carbon sources for EPS synthesis instead of generating energy and enzymes for degradation reactions. Simultaneously, an overly sticky pile may also affect turning efficiency. Therefore, controlling its proportion slightly lower than that of phosphate-solubilizing bacteria maximizes functionality without side effects.

[0026] In the aforementioned sodium alginate-biochar-montmorillonite composite microcapsules, the sodium alginate concentration is 2.5%, the biochar particle size is 150 mesh, and the mass ratio of montmorillonite to sodium alginate is 1:3. The specific preparation steps of these sodium alginate-biochar-montmorillonite composite microcapsules are as follows: Weigh a certain amount of sodium alginate and slowly add it to boiling sterile deionized water. Stir magnetically to dissolve it completely, preparing a 2.5% (w / v) clear solution. Autoclave at 121℃ for 20 minutes and cool to room temperature (below approximately 40℃) for later use.

[0027] The phosphoric acid-modified biochar was ground and passed through a 150-mesh sieve to obtain an ultrafine powder. It was then placed in a drying oven for dry heat sterilization at 160°C for 2 hours. In a sterile operating table (clean bench), the sterilized montmorillonite powder and biochar powder were pre-mixed evenly at a mass ratio of 1:3.

[0028] The above-mentioned mixed inorganic materials were slowly added to a cooled 2.5% sodium alginate solution. The total mass ratio of the inorganic materials to the sodium alginate solids was 1:1-1.5:1. The mixture was dispersed in an ice bath using a high-speed homogenizer or an ultrasonic cell disruptor to form a uniform and stable sodium alginate-biochar-montmorillonite composite carrier solution.

[0029] Take a high-concentration compound bacterial suspension and slowly add it to the compound carrier gel while stirring, ensuring uniform dispersion of the bacteria. The final total bacterial concentration of the mixture should reach 50–80 × 10⁻⁶. 8 CFU / g. The gel solution was dropped into a sterile 0.1 mol / L calcium chloride (CaCl2) solution at a constant rate. Upon contact with the CaCl2 solution, sodium ions in the sodium alginate exchanged with calcium ions, forming a water-insoluble calcium alginate gel network that firmly encapsulates the bacterial cells and biochar / montmorillonite, forming spherical or ellipsoidal microcapsules.

[0030] A composting method based on the aforementioned compound microbial inoculant includes the following steps: a) Raw material pretreatment: Crush agricultural and forestry waste (such as branches, straw, rice husks, or one or more of these mixed in any proportion) into 1-2 cm particles, and mix it with poultry and livestock manure (such as pig manure, chicken manure, or one or two of these mixed in any proportion) at a dry weight ratio of (6.5-7.5):(2.5-3.5). Adjust the initial carbon-nitrogen ratio (C / N) of the mixture to 28-32:1 and the moisture content to 55-60%. b) Adding a photocatalytic system: Add 0.3-0.5% of riboflavin (vitamin B2), 0.1-0.3% of ferrous sulfate heptahydrate (FeSO4·7H2O), and 5-8% of phosphoric acid modified biochar to the mixture obtained in step a), and mix evenly; c) Inoculation with microbial agent: When the pile temperature naturally rises to 50-55℃, inoculate 1.0-1.5% of microcapsules containing a compound microbial agent by dry weight of the mixture; then pile the material into a windrow pile with a base width of 2.0-2.5 m and a height of 1.0-1.3 m; d) Covering and process control: Cover the pile surface with a three-layer structure, from the inside out: a breathable non-woven fabric layer, a biodegradable heat-insulating film layer, and a shade net layer with a shading rate of 40-50%; dynamically control the turning time based on three indicators: laccase activity, oxidation-reduction potential (ORP), and volatile fatty acid (VFA) concentration, and dynamically adjust the moisture content and C / N ratio. The pH value of the pile should be maintained between 6.5 and 7.5 (which can be adjusted by adding lime or phosphate rock powder), and the moisture content should be controlled at 55%-65%; e) When laccase activity > 200 U / g, ORP < -100 mV and VFA concentration > 800 mg / kg, turn the compost.

[0031] The preparation method of phosphoric acid modified biochar in this invention includes: pulverizing biomass raw materials (such as one or two of reed straw, mixed in any proportion) to 20-60 mesh. Using a 30%-60% phosphoric acid solution, mix the biomass raw materials at a 1:1 (mL:g) impregnation ratio, impregnate at room temperature for 12-24 hours, transfer the impregnated mixture to a muffle furnace or tube furnace, and pyrolyze under an inert atmosphere (high-purity nitrogen), heating to 500℃ at a rate of 5-10℃ / min, maintaining the target temperature for 1-2 hours. After pyrolysis, allow the furnace to cool naturally to room temperature, repeatedly wash the carbonized product with deionized water or distilled water until the pH of the washing liquid is close to neutral (pH test paper detects 6.5-7.5); dry the washed biochar in an oven at 105℃ to constant weight, grind, and pass through a 100-mesh sieve for later use.

[0032] A compost product prepared by the aforementioned method has a lignin degradation rate of ≥50%, a total nitrogen retention rate of ≥80%, and a germination index (GI) of ≥95%.

[0033] The key point of this invention is: First, the design of the compound microbial agent formulation: This invention creatively determines specific functional microbial species (white-rot fungi, thermophilic actinomycetes, and nitrogen-fixing bacteria) and precise proportions. This formulation is carefully designed to ensure functional complementarity and niche separation, avoiding antagonistic effects between species, forming a functionally complementary microbial degradation network, and constructing a highly efficient microbial community for degrading lignocellulose. Compared with existing single-species or simple compound microbial agents, this formulation has broader substrate adaptability and higher degradation efficiency.

[0034] The core bacterial strain composition includes: white-rot fungus *Trametes versicolor* (25-35%), thermophilic actinomycete *Thermobifida fusca* (15-20%), and nitrogen-fixing bacteria (25-30%), supplemented with a balanced combination of phosphate-solubilizing bacteria *Bacillus megaterium* and exopolysaccharide-producing bacteria *Xanthomonas campestris* (10-20%), with a total concentration of 50–80 × 10⁻⁶. 8 CFU / g, encapsulated in sodium alginate-biochar-montmorillonite composite microcapsules. Among them, white-rot fungi secrete lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase, synergistically attacking the phenolic and non-phenolic structures in lignin, achieving initial depolymerization; thermophilic actinomycetes are active at 50–65℃, secreting heat-stable cellulase and hemicellulase, efficiently degrading exposed cellulose and hemicellulose; nitrogen-fixing bacteria not only reduce nitrogen loss, but their secreted organic acids also promote mineral dissolution, provide trace elements, and enhance the metabolic activity of the microbial community. This combination not only covers the needs of full-component degradation of lignocellulose but also forms a metabolically complementary microbial symbiotic system.

[0035] White-rot fungi degrade lignin into low-molecular-weight phenolic compounds, which serve as carbon and energy sources for actinomycetes. Actinomycetes further degrade cellulose and hemicellulose into soluble sugars, providing growth substrates for all strains. Nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia through biological nitrogen fixation, providing nitrogen nutrition for the entire system. This is particularly important because lignocellulose materials typically have a high carbon-to-nitrogen ratio (C / N ratio), and nitrogen deficiency severely limits microbial growth and enzyme activity. The nitrogen source provided by nitrogen-fixing bacteria directly supports the growth of white-rot fungi and actinomycetes, as well as their enzyme synthesis. Growth factors such as vitamins and amino acids produced by actinomycete metabolism promote the growth of white-rot fungi, while aromatic compounds produced by the decomposition of lignin by white-rot fungi induce actinomycetes to produce more cellulase-degrading enzymes.

[0036] The three types of microorganisms together create a microenvironment suitable for their respective growth: nitrogen-fixing bacteria consume oxygen, creating suitable conditions for the anaerobic metabolic enzyme system of white-rot fungi; the growth of actinomycetes increases the temperature of the pile, creating an optimal environment for thermophilic actinomycetes; and the formation of white-rot fungal mycelium improves the porosity of the pile, promoting the uniform distribution of oxygen and heat.

[0037] Encapsulation with sodium alginate-biochar-montmorillonite composite microcapsules not only improved the survival rate of the microbial agent under high-temperature composting conditions (biochar and montmorillonite provide protection and a hollow structure), but also achieved slow-release and targeted colonization of the agent (due to the gel properties of sodium alginate). After treatment at 65°C for 2 hours, the survival rate of the encapsulated agent was more than 3.5 times higher than that of the unencapsulated agent.

[0038] Second, the photo-biological synergistic degradation system: This invention innovatively combines controllable photocatalysis with biodegradation to construct a highly efficient synergistic degradation system, breaking through the limitations of low efficiency in traditional single degradation modes.

[0039] The natural spectrum optimization method abandons the complex UV-A filter membrane device of existing technologies and instead adds 0.3-0.5% riboflavin (vitamin B2) and 0.1-0.3% ferrous sulfate heptahydrate (FeSO4·7H2O) by weight of the compost as a photocatalytic system, while adding 5-8% phosphoric acid-modified biochar for nitrogen fixation and fertilizer retention. This allows for the photodegradation of lignin under natural light conditions. By adjusting the compost height and turning frequency (once every 3 days), uniform light distribution is ensured, increasing the lignin degradation rate by 40-50%.

[0040] The role of phosphoric acid-modified biochar: ① Phosphoric acid modification introduces a large number of oxygen-containing functional groups (such as carboxyl-COOH and phenolic hydroxyl-OH) and phosphorus-containing functional groups onto the surface of biochar. These functional groups carry a negative charge, which helps to control the ammonium ions (NH4+) generated during composting. + It possesses extremely strong electrostatic adsorption capabilities, effectively reducing nitrogen loss through volatilization as ammonia (NH3) and "fixing" nitrogen within the compost pile. This not only avoids environmental pollution (ammonia is a precursor to foul odors and smog), but more importantly, it retains nitrogen nutrients, improving the fertilizer efficiency of the final compost product. ② The huge specific surface area and well-developed pore structure of biochar provide countless "microreactors" for the photo-Fenton reaction. Riboflavin and Fe 2+ It can be adsorbed onto the surface of biochar, resulting in a localized increase in reactant concentration and improving reaction efficiency; Fe 2+ It is easily oxidized to Fe in the neutral or slightly alkaline environment of composting. 3 + It forms a precipitate and becomes inactive. The functional groups on the surface of phosphoric acid-modified biochar can fix Fe through complexation. 2+ / Fe 3+To prevent precipitation, extend the lifespan of the iron catalyst, and ensure the continuous photocatalytic reaction; ③ The Fenton reaction requires strongly acidic conditions (pH≈3), which is impractical in composting. Phosphoric acid-modified biochar itself is weakly acidic, and its surface phosphate groups and phosphates have a certain buffering capacity. It can neutralize some alkaline substances (such as ammonia) produced during composting, stabilizing the pH of the compost microenvironment within a range relatively suitable for Fenton-like reactions (weakly acidic to neutral), thus avoiding reaction stagnation due to excessively high pH.

[0041] The in-situ photocatalytic system utilizes a composite catalyst formed by adding 0.3-0.5% riboflavin (vitamin B2) and 0.1-0.3% ferrous sulfate heptahydrate (FeSO4·7H2O) to the lignin stockpile. This invention does not rely on an external UV light source; instead, it leverages the absorption characteristics of riboflavin in the visible light region to generate reactive oxygen species under natural light. These reactive oxygen species attack the ether and carbon-carbon bonds in lignin molecules, causing them to break down into smaller molecular fragments that are more easily degraded by microorganisms. This system increases the lignin degradation rate by 1.8-2.5 times.

[0042] Third, dynamic process control strategy: In response to the challenge of multi-parameter coordinated control in composting, this invention proposes a dynamic control strategy based on biomarkers, which achieves precise optimization of the composting process.

[0043] Stack construction: The mixed material is stacked into a windrow stack with a base width of 2.0-2.5m and a height of 1.0-1.3m, and covered with a three-layer structure: the bottom layer is a breathable non-woven fabric, the middle layer is a biodegradable heat insulation film, and the top layer is a shade net with a shading rate of 40-50%.

[0044] Turning control: Laccase activity, oxidation-reduction potential (ORP), and volatile fatty acid (VFA) concentration in the heap are monitored in real time using embedded sensors. Turning is performed when laccase activity > 200 U / g, ORP < -100 mV, and VFA concentration > 800 mg / kg.

[0045] Moisture and C / N ratio control: During the high temperature period (>50℃), the C / N ratio is adjusted to 10-15:1 by adding straw powder, and the moisture content is reduced to 50-55%; during the cooling period, poultry and livestock manure is added to restore the C / N ratio to 15-20:1, and the moisture content is maintained at 45-50%.

[0046] A combined control model based on laccase activity, ORP, and VFA concentration—three biological / chemical indicators—replaces traditional experience-based or single-temperature control methods, enabling optimal judgment of when to turn the compost pile. This not only reduces the number of times the pile needs to be turned by 30%, lowering energy consumption and labor costs, but also ensures that the pile is always in an optimal state of biological reaction, improving the stability of compost quality and the maturity of the product (germination index GI ≥ 95%).

[0047] Example 1 The composting method provided by the present invention includes: 1) Raw materials: Straw and pig manure are mixed in a ratio of 7.5:2.5, with an initial C / N ratio of 30:1 and a moisture content of 60%.

[0048] Microbial agent: A compound microbial agent was prepared according to the present invention (T. versicolor: 30%, T. fusca: 18%, Japanese slow-growing rhizobium SEMIA 5079: 30%, auxiliary bacteria: the ratio of viable counts of phosphate-solubilizing bacteria and extracellular polysaccharide-producing bacteria was 1.5:1, 20%), with a total concentration of 65 × 10⁻⁶. 8 CFU / g was encapsulated using sodium alginate-biochar-montmorillonite composite microcapsules.

[0049] Additives: 0.4% riboflavin, 0.2% FeSO4·7H2O, and 6% phosphoric acid modified biochar are added according to the dry weight of the stockpile.

[0050] Process control: 1) Mix the above raw materials and additives evenly. When the temperature of the stockpile naturally rises to 55℃ (on the 3rd day), inoculate microcapsules containing compound microbial agents at a ratio of 1.2% of the dry weight of the stockpile. 2) Construct the stack under environmental conditions. The stack is a windrow type, with a base width of 2.2 m, a height of 1.2 m, and a length of 2 m (total volume approximately 5.28 m³). 3 ).

[0051] 3) The three-layer structure of the pile body: the inner layer is breathable non-woven fabric, the middle layer is biodegradable PLA insulation film, and the outer layer is a shade net with a shading rate of 50%.

[0052] 4) Embedded sensors were used to monitor the core layer temperature, laccase activity, oxidation-reduction potential (ORP), and volatile fatty acid (VFA) concentration in real time. The pile was turned over when all of the following conditions were met simultaneously: laccase activity >200 U / g, ORP <-100 mV, and VFA concentration >800 mg / kg. The pile was turned over a total of 8 times during the entire 40-day cycle.

[0053] 5) Moisture control: The moisture content of the heap is maintained between 50% and 60% by spraying sterile water. The pH value is maintained at around 7.0 by adding a small amount of phosphate rock powder.

[0054] Compare with Example 1 Using traditional microbial agents Except for the use of commercially available lignin-degrading microbial agents (mainly Phanerochaete chrysosporium), the other conditions were exactly the same as in Example 1. The turning operation adopted the traditional temperature control method (turning the pile when the temperature is >65°C).

[0055] Compare with Example 2 Using microencapsulated bacterial agents Microbial agent: A compound microbial agent (T. versicolor: 30%, T. fusca: 18%, Japanese slow-growing rhizobium SEMIA 5079: 30%, auxiliary bacteria: the ratio of viable counts of phosphate-solubilizing bacteria and extracellular polysaccharide-producing bacteria is 1.5:1, 20%) was prepared according to Example 1 of this invention, with a total concentration of 65 × 10⁻⁶. 8 CFU / g, without microencapsulation. All other conditions were exactly the same as in Example 1.

[0056] Compare with Example 3 No photocatalytic system Except for the absence of riboflavin and FeSO4·7H2O, the other conditions were exactly the same as in Example 1.

[0057] Compare with Example 4 Experience-based regulation Except for the turning operation, which is based solely on the experience of experienced workers (approximately once every 5-7 days, depending on temperature changes), the other conditions are exactly the same as in Example 1.

[0058] The experimental results are shown in Table 1. Figure 1 , Figure 2 As shown.

[0059] Table 1 As shown in Table 1, the lignin degradation rate (56.4%) and cellulose degradation rate (76.2%) of Example 1 (using the compound microbial agent of the present invention) were significantly higher than those of Control Example 1 (using the traditional microbial agent, 31.5% and 55.8%, respectively). This fully demonstrates the functional complementarity and synergistic effect among the strains in the microbial agent formulation of the present invention. White-rot fungi dominate the initial depolymerization of lignin, thermophilic actinomycetes efficiently degrade exposed cellulose, and nitrogen-fixing bacteria provide stable nitrogen nutrition for the entire microbial community through biological nitrogen fixation, overcoming the limitations imposed on microbial activity by high carbon-to-nitrogen ratio raw materials.

[0060] Compared with Example 2 (without microencapsulation), all indicators, especially the lignin degradation rate (48.7%) and total nitrogen retention rate (75.3%), were significantly lower than those of Example 1. This confirms that microencapsulation technology is crucial for protecting functional strains from the high temperature (50-65°C) stress of the compost pile and extending their active lifespan. The data supports the description in the specification: "After treatment at 65°C for 2 hours, the survival rate of the encapsulated inoculum was more than 3.5 times higher than that of the unencapsulated inoculum," ensuring efficient colonization and functional expression of the inoculum throughout the entire composting cycle.

[0061] Independent contribution of photocatalysis: The experimental results of Control Example 3 (without photocatalytic system) provide crucial evidence. While its lignin degradation rate (45.2%) was superior to that of the conventional inoculant (Control Example 1), it was significantly lower than that of Example 1 with the complete technical solution (56.4%). This clearly demonstrates the direct and irreplaceable contribution of the photocatalytic system to lignin degradation. Riboflavin is excited under visible light and reacts with Fe... 2+ It forms a Fenton-like system, generating reactive oxygen free radicals that attack lignin macromolecules, achieving a non-biological "pretreatment" that makes them easier for microorganisms to utilize later.

[0062] Example 1 demonstrates an excellent total nitrogen retention rate (83.7%), which is attributed not only to nitrogen-fixing bacteria but also to the crucial role played by phosphoric acid-modified biochar. Its large specific surface area and surface functional groups effectively adsorb and fix ammonium nitrogen, reducing ammonia volatilization losses. Simultaneously, as described in the specification, it acts as a "microreactor" to stabilize Fe. 2+ / Fe 3+ This ensured the continuous and efficient execution of the photocatalytic reaction.

[0063] Compared to Example 4 (empirical control), its total nitrogen retention rate (71.9%) and seed germination index (GI) (90.3%) were significantly lower than those of Example 1 (83.7% and 98.5%, respectively). This difference directly demonstrates the significant advantages of the intelligent dynamic control strategy of this invention in reducing nitrogen loss and improving product decomposition. Based on the accurate judgment of ORP and VFA, nitrogen volatilization and heat loss caused by excessive turning are avoided, as are localized anaerobic digestion and organic acid accumulation caused by insufficient turning.

[0064] Example 1 achieved complete composting (GI>95%) within a 40-day period, while Control Example 1 was "incompletely composted" within the same period. This demonstrates that the control strategy of the present invention not only optimizes individual operations but also accelerates and optimizes the composting process as a whole, ensuring the high quality and stability of the final product.

[0065] Figure 1The data clearly demonstrate the dynamic process of lignin degradation under different treatment conditions, highlighting the crucial role of photo-biological synergy in lignin degradation. The lignin degradation rate of Example 1 (the complete technical solution of this invention) ultimately reached 56.4%, significantly higher than all control examples. The lignin degradation curve of Control Example 3 in the first 15 days showed a significant difference from that of Example 1. This indicates that riboflavin / Fe 2+ The photocatalytic system plays a pioneering role in the early stages of composting. Under natural light, the system generates reactive oxygen species (ROS), which non-biologically attack and break the stubborn ether and C-C bonds in lignin molecules, depolymerizing them into smaller, bioavailable phenolic fragments. This "pretreatment" clears the way for subsequent microbial degradation, allowing white-rot fungi and other microorganisms to act on lignin earlier and more efficiently, thus significantly accelerating the degradation rate and increasing the final degradation degree. Control Example 1 showed the lowest lignin degradation rate (only 31.5%), and its flat degradation curve indicates that single or simple composite microbial agents struggle to overcome the structural barrier of lignin. This highlights the functional complementarity and synergy of the ternary composite microbial agent (white-rot fungi-actinomycetes-nitrogen-fixing bacteria) of this invention.

[0066] Figure 2 The degradation of cellulose is shown. In Example 1, the cellulose degradation rate exhibited a significant acceleration during the middle stage of composting (approximately 10-20 days), while the degradation of lignin (…) Figure 1 This stage has progressed steadily, precisely confirming the relay mechanism of the "microbial degradation network" described in the instructions. Photocatalysis and white-rot fungi synergistically initiate lignin degradation, destroying the "protective shell" surrounding cellulose. As lignin depolymerizes, cellulose and hemicellulose are fully exposed. At this point, thermophilic actinomycetes (Thermobifida fusca) become dominant, and their secreted thermostable cellulases are induced in large quantities, resulting in an explosive degradation of the exposed cellulose. Therefore, the final cellulose degradation rate in Example 1 reached 76.2%. Nitrogen-fixing bacteria, through biological nitrogen fixation, provide a stable nitrogen source for the two main "decomposers," white-rot fungi and actinomycetes, overcoming the nitrogen nutrient limitations commonly found in high C / N ratio raw materials, and ensuring that the entire microbial community can maintain high metabolic activity continuously.

[0067] The technological advantage of this invention is not simply the sum of microorganisms, photocatalysis, and intelligent regulation, but rather the deep synergistic effect they produce. Photocatalysis paves the way for biodegradation, biodegradation clears obstacles for photocatalysis and utilizes its products, while intelligent regulation provides a stable operating environment for the former two. By combining "photocatalytic pretreatment" with "microbial relay degradation," the core problem of incomplete lignin degradation in traditional composting has been successfully solved, increasing the degradation rate from less than 35% to over 50%. This system not only degrades lignin but also achieves efficient and simultaneous degradation of cellulose and hemicellulose through orderly microbial community succession, thereby significantly shortening the composting cycle and improving the maturity of the final product (GI index as high as 98.5%).

[0068] The above description is merely a specific embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any transformations or substitutions that can be conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A composting method based on the synergistic effect of composite microbial inoculant and light-biology, characterized in that, The method comprises the following steps: a) raw material pretreatment: crushing the agricultural and forestry waste, mixing it with livestock manure at a dry weight ratio of (6.5-7.5):(2.5-3.5), adjusting the initial carbon-nitrogen ratio of the mixture to 28-32:1, and the moisture content to 55-60%; b) adding a photocatalytic system: adding 0.3-0.5% of riboflavin, 0.1-0.3% of ferrous sulfate heptahydrate, and 5-8% of phosphoric acid modified biochar to the mixture obtained in step a) by dry weight, and mixing uniformly; c) inoculating the bacterial agent: when the temperature of the pile naturally rises to 50-55℃, inoculate 1.0-1.5% of the microcapsules embedded with the composite microbial agent in the mixture by dry weight; then build the material pile into a strip pile; d) covering and process control: cover the surface of the pile with a three-layer structure from the inside to the outside, which is a breathable non-woven fabric layer, a degradable insulation film layer, and a sunshade net layer; dynamically control the turning-over time based on the three indicators of laccase activity, oxidation-reduction potential, and volatile fatty acid concentration, and dynamically adjust the moisture content and C / N ratio; the pH value of the pile is maintained at 6.5-7.5, and the moisture content is controlled at 55%-65%; e) when the laccase activity is >200 U / g, the ORP is <-100 mV, and the VFA concentration is >800 mg / kg, perform the turning-over operation.

2. The composting method of claim 1, wherein, The complex microbial agent is composed of the following strains: white rot fungi, accounting for 25-35% of the total number of viable bacteria; high-temperature actinomycetes, accounting for 15-20% of the total number of viable bacteria; nitrogen-fixing bacteria, accounting for 25-30% of the total number of viable bacteria; and auxiliary flora, accounting for 10-20% of the total number of viable bacteria; the total concentration of the agent is 50-80 x 10 8 CFU / g, and is embedded using sodium alginate-biochar-montmorillonite composite microcapsules.

3. The composting method of claim 1, wherein, The nitrogen-fixing bacteria are Bradyrhizobium japonicum SEMIA 5079 or SEMIA 5080; the auxiliary bacterial community is phosphorus-solubilizing bacteria and exopolysaccharide-producing bacteria, and the ratio of the number of viable bacteria of the phosphorus-solubilizing bacteria to the number of viable bacteria of the exopolysaccharide-producing bacteria is 1.2:1-1.5:

1.

4. The composting method according to claim 1 or 2, characterized in that, The preparation steps of the sodium alginate-biochar-montmorillonite composite microcapsule embedded with the composite microbial agent include: (1) weigh a certain amount of sodium alginate, slowly add it to boiling sterile deionized water, and magnetically stir to fully dissolve it to prepare a 2.5% clear solution, 121℃ high-pressure sterilization for 20 minutes, and cool to room temperature for standby; (2) grind the biochar modified by phosphoric acid, pass it through a 150-mesh sieve to obtain ultra-fine powder, and place it in a drying oven for 160℃ dry heat sterilization for 2 hours; in a sterile operation table, pre-mix the sterilized montmorillonite powder and biochar powder at a mass ratio of 1:3; (3) slowly add the above mixture to the cooled 2.5% sodium alginate solution, wherein the mass ratio of the total mass of the mixture to the mass of the sodium alginate solid is 1:1-1.5:1; perform dispersion treatment under ice bath conditions to form a sodium alginate-biochar-montmorillonite composite carrier glue solution; (4) Take high concentration of compound bacteria suspension, slowly add compound carrier glue liquid under stirring, ensure uniform dispersion of bacteria, the total bacteria concentration of final mixture should reach 50-80x10 8 CFU / g; drop the glue liquid into sterile 0.1mol / L calcium chloride solution at constant speed, form spherical or ellipsoidal microcapsules.

5. The composting method of claim 1, wherein, The agricultural and forestry waste is one or two or more of tree branches, straw, and rice husk in any proportion; the livestock manure is one or a mixture of two kinds of pig manure or chicken manure in any proportion.

6. The composting method of claim 1, wherein, In step c), the strip pile has a bottom width of 2.0-2.5 m and a height of 1.0-1.3 m.

7. The composting method of claim 1, wherein, In step d), a sunshade net layer with a shading rate of 40-50% is used.

8. The composting method of claim 1, wherein, The preparation method of the phosphoric acid modified biochar comprises the following steps: (1) Using phosphoric acid solution with mass fraction of 30%-60%, the biomass raw material is mixed with the phosphoric acid solution at impregnation ratio of 1:1, and impregnated at room temperature for 12-24 hours; (2) The mixture after impregnation is transferred to a muffle furnace or a tube furnace, and pyrolysis is carried out under inert atmosphere, the pyrolysis temperature is 500℃, and the temperature is kept at the target temperature for 1-2 hours; (3) After the pyrolysis is completed, the furnace body is naturally cooled to room temperature, and the carbon particles are repeatedly washed with deionized water or distilled water until the pH value of the washing liquid approaches neutral; (4) The washed biochar is dried in an oven at 105℃ to constant weight, ground and sieved through a 100 mesh sieve for use.

9. The composting method of claim 8, wherein, The biomass raw material is one or two of southern di, reed and straw mixed in any ratio.

10. A compost product prepared according to the composting method of any one of claims 1-9, characterized in that, The lignin degradation rate is ≥50%, the total nitrogen retention rate is ≥80%, and the germination index is ≥95%.

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