Method for fusing anaerobic fermentation compost

Abstract

The invention relates to the technical field of agriculture, in particular to a method for fusing anaerobic fermentation compost, which comprises the following steps: mixing organic waste raw materials, and adding sodium citrate and magnesium sulfate for treatment; feeding the treated raw materials into an anaerobic reactor, adding an iron-based core-shell structure material, controlling the pH value of the system, and carrying out anaerobic fermentation to obtain digestion residues; bicarbonate and sodium citrate are added into the digestion residues to be mixed; and entering an aerobic composting stage, controlling the moisture content of the pile body under an oxygen supply condition, heating the pile body, maintaining the pile body to enter a decomposition stage, and carrying out natural aging to produce a decomposed organic fertilizer. In the invention, by virtue of the porous structure and surface characteristics of the iron-based core-shell structure material, not only is the stability of the fermentation process ensured, but also the microbial electron transfer process is optimized, and the methane production efficiency is improved; the compound microbial agent effectively increases the number of effective microbial communities, improves the temperature and ventilation conditions in the composting process, and ensures uniform decomposition of the organic wastes.

Description

Technical Field

[0001] This invention relates to the field of agricultural technology, and more specifically, to a method for incorporating anaerobic fermentation composting. Background Technology

[0002] With the increasing demand for environmental protection, how to effectively treat organic waste has become an important issue facing society today. Among the existing methods for treating organic waste, the integration of anaerobic fermentation and composting technologies is widely used. This method first performs anaerobic fermentation to convert the waste into biodegradable digestible residue, and then further degrades the organic matter into mature organic fertilizer through aerobic composting. This technical route can synergistically achieve energy recovery and soil conditioner production, improve overall resource utilization efficiency, reduce secondary pollution, and has good application prospects.

[0003] Existing technologies that integrate anaerobic fermentation and composting for treating organic waste still have shortcomings: during the anaerobic fermentation stage, insufficient buffering capacity of raw materials and imbalanced nutrient ratios can easily lead to suppressed microbial activity, resulting in instability in the fermentation process and fluctuations in gas production efficiency. This instability affects the subsequent aerobic composting stage, causing poor aeration, slow temperature rise, and prolonged composting period, ultimately leading to uneven product composting and inconsistent quality. In view of this, we propose a method that integrates anaerobic fermentation and aerobic composting. Summary of the Invention

[0004] The purpose of this invention is to provide a method for anaerobic fermentation composting, in order to solve the problems mentioned in the background art, where insufficient buffering capacity of raw materials and imbalance of nutrient ratios during the anaerobic fermentation stage easily lead to the inhibition of microbial activity, resulting in instability in the fermentation process and fluctuations in gas production efficiency. This instability affects the subsequent aerobic composting stage, leading to poor aeration of the compost pile, slow heating, and prolonged composting period, ultimately resulting in uneven product composting and inconsistent quality.

[0005] This invention provides a method for fusion anaerobic fermentation composting, comprising the following steps: S1.1 After mixing the organic waste raw materials, add sodium citrate (1-5% by dry weight of the organic waste raw materials) and magnesium sulfate (0.5-2.0% by dry weight of the organic waste raw materials), and mix at 15-40℃ for 30-60 minutes to obtain the treated raw materials. S1.2. The treated raw materials are fed into an anaerobic reactor, iron-based core-shell structure material is added, and anaerobic fermentation is carried out at 30-38℃. The pH of the fermentation system is controlled at 6.5-8.0 with a sodium hydroxide solution of 10-30% by mass. The fermentation time is 10-30 days to obtain digestion residue. S1.3 Add 0.5-3.0% of the wet weight of bicarbonate and 0.2-2.0% of sodium citrate to the digestion residue, mix and stir for 10-40 minutes at 20-50℃; then carry out aerobic composting, control the moisture content of the compost to 50-65%, and raise the temperature of the compost to 55-70℃ under oxygen supply conditions and maintain it for 3-7 days to enter the decomposition stage. Then, carry out aging treatment for 20-30 days under natural ventilation conditions. After aging, the decomposed organic fertilizer is obtained.

[0006] Preferably, in S1.1, the organic waste raw material is one or more of kitchen waste, livestock and poultry manure, and sludge.

[0007] Preferably, in step S1.2, the amount of iron-based core-shell structure material added accounts for 0.1-0.5% of the dry weight of the treated raw material; The preparation method of iron-based core-shell structured materials is as follows: Pretreated wood was pyrolyzed at 500-800℃ for 2-6 hours under nitrogen protection to obtain porous carbon material. The porous carbon material was mixed with 0.5 mol / L ferric sulfate solution and stirred at 300-500 rpm for 0.5-1.0 hours, then reacted in a boiling water bath for 1-2 hours. After the reaction was completed, the solid was separated, pre-dried at 105℃ for 2 hours, and then heated in an oven at 150-200℃ for 2-4 hours. After cooling, it was washed and dried to obtain iron oxide-supported porous carbon material. The porous carbon material supported on iron oxide was mixed with a 0.5 mol / L glycine solution, heated to 70-90℃, and stirred at 200-400 rpm for 4-8 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and then dried at 50-70℃ for 10-12 h to obtain the surface-modified porous carbon material. Surface-modified porous carbon material was dispersed in a mixed aqueous solution containing sodium citrate and chitosan at a solid-liquid ratio of 1:8 and stirred at 100-200 rpm for 4-8 h at 40-60℃ and pH 5.0-6.0. Sodium tripolyphosphate was then added and reacted at 50-70℃ for 6-12 h to obtain an iron-based core-shell structured material.

[0008] Preferably, the mass ratio of the porous carbon material to ferric sulfate is 1:0.1-0.3; The mass ratio of iron oxide-supported porous carbon material to glycine is 1:3-5.

[0009] Preferably, the mass ratio of sodium citrate to chitosan is 1:2-4; The mass ratio of sodium tripolyphosphate to chitosan is 0.2-1.0:1.

[0010] Preferably, in step S1.2, the organic loading rate of anaerobic fermentation is 1.0-4.0 kgVS / (m³). 3 ·d).

[0011] Preferably, in S1.3, the bicarbonate is sodium bicarbonate or ammonium bicarbonate.

[0012] Preferably, in step S1.3, 0.1-1.0% of the wet weight of the digested residue is added during the initial stage of aerobic composting; The amphoteric organic salt is a mixture of aspartic acid and betaine in a mass ratio of 1:3.

[0013] Preferably, in step S1.3, a compound microbial agent accounting for 0.5-2.0% of the wet weight of the digested residue is added at the initial stage of aerobic composting; The preparation method of the compound microbial agent is as follows: Thermosensitive amyloliquefaciens and Trichoderma reesei were mixed at a live count ratio of 1:0.5 to obtain a composite functional bacterial group. The complex functional microbial community was mixed with sodium alginate, gelatin and dipotassium hydrogen phosphate in a mass ratio of 1:10:5:2 and dispersed in deionized water at a solid-liquid ratio of 1:15-30 to form a bacterial suspension colloid. The bacterial suspension colloid was then dripped into a 0.2-0.5 mol / L calcium chloride solution to form cross-linked microspheres. Microspheres were immersed in a mixed solution of gelatin and chitosan with a mass concentration of 2-5% (mass ratio of gelatin to chitosan 1:2) and adsorbed at 4-10℃ for 2-4 hours. Then, the temperature was raised to 30-35℃ and maintained for 1-2 hours to dehydrate and shrink the microspheres. Finally, the microspheres were vacuum dried at 30-35℃ and an absolute pressure of 2-8 kPa to obtain the composite microbial agent.

[0014] Preferably, in step S1.3, forced ventilation is used during the aerobic composting process, with a ventilation volume of 0.1-0.5 m³ / s. 3 / (min·t).

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: In the anaerobic fermentation composting method of this invention, by adding iron-based core-shell structured materials during the anaerobic fermentation stage, the unique porous structure and surface properties not only stabilize the fermentation process but also optimize the electron transfer process between microorganisms, thereby improving the efficiency of methanogenesis. Secondly, the added amphoteric organic salts, as osmotic regulators and methyl donors, can regulate the osmotic pressure balance of microbial cells in the early stage of composting and provide methyl groups to promote microbial metabolism, thereby improving the microbial growth environment in the early stage of composting. In addition, the compound microbial agent increases the beneficial bacteria in the composting process, which helps to improve temperature control and aeration conditions in the composting process, thereby ensuring the uniformity and stability of the composting process and achieving efficient decomposition and transformation of organic waste. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] The organic waste raw materials are one or more of kitchen waste, livestock and poultry manure, and sludge, with kitchen waste being the preferred material in this embodiment of the invention.

[0018] Sodium citrate (CAS No.: 68-04-2, purity: 98%, item number: S67462-100g), magnesium sulfate (CAS No.: 7487-88-9, purity: AR, 98%, item number: S24253-500g), ferric sulfate (CAS No.: 10028-22-5, purity: AR, item number: S70004-500g), glycine (CAS No.: 56-40-6, purity: AR, 99%, item number: S20159-25g), chitosan (CAS No.: 9012-76-4, purity: BR, degree of deacetylation 90%, viscosity ≤500cps), sodium tripolyphosphate (CAS No.: 7758-29-4, purity: 85%, item number: S67462-100g), The following products were purchased from Shanghai Yuanye Biotechnology Co., Ltd.: S30235-500g, aspartic acid (CAS No.: 6899-03-2, purity: 98%, item number: S67514-5g), betaine (CAS No.: 107-43-7, purity: 99%, item number: S18046-100g), sodium alginate (CAS No.: 9005-38-3, purity: AR, 98%, item number: S11053-500g), gelatin (CAS No.: 9000-70-8, purity: BR, item number: S30952-100g), and dipotassium hydrogen phosphate (CAS No.: 7758-11-4, purity: AR, 98%, item number: S24280-500g).

[0019] Pre-treated wood is obtained by soaking wood (poplar, pine or fir) in a 0.1 mol / L sodium chloride solution to remove dissolved substances and soluble impurities; then it is dried in a drying oven at 50-80℃, and finally crushed by a crusher.

[0020] The bicarbonate is sodium bicarbonate or ammonium bicarbonate, and sodium bicarbonate is preferred in the embodiments of the present invention.

[0021] The preservation number for *Bacillus thermophilus* is CICC 20849; the preservation number for *Trichoderma reesei* is CICC 40358.

[0022] Example 1: A method for anaerobic fermentation composting, comprising the following steps: S1.1 After mixing the kitchen waste, add sodium citrate (1% by dry weight of the kitchen waste) and magnesium sulfate (0.5% by dry weight of the kitchen waste), mix at 15°C for 60 minutes to obtain the processed raw material; S1.2. The treated raw materials are fed into an anaerobic reactor, and 0.1% (by dry weight of the treated raw materials) of iron-based core-shell structured material is added. Anaerobic fermentation is carried out at 30°C. The pH of the fermentation system is controlled at 6.5 using a 10% sodium hydroxide solution, and the organic loading rate is 1.0 kgVS / (m³). 3 ·d), the fermentation time is 10 days, and digestion residue is obtained; S1.3. Add 0.5% sodium bicarbonate and 0.2% sodium citrate by weight of the digestion residue (wet basis) to the digestion residue and mix at 20°C for 40 minutes. Then proceed with aerobic composting. At the initial stage of aerobic composting, add 0.1% amphoteric organic salt (a mixture of aspartic acid and betaine in a 1:3 mass ratio) and 0.5% compound microbial agent by weight of the digestion residue (wet basis). Control the moisture content of the compost pile to 50%. Provide oxygen and forced ventilation (ventilation volume 0.1 m³ / s). 3 Under the condition of / (min·t)), the temperature of the pile is raised to 55℃ and maintained for 7 days before entering the decomposition stage. After natural aging, decomposed organic fertilizer is obtained.

[0023] The preparation method of iron-based core-shell structured materials is as follows: Pretreated wood was pyrolyzed at 500℃ for 6 hours under nitrogen protection to obtain porous carbon material. The porous carbon material was mixed with 0.5 mol / L ferric sulfate solution (mass ratio 1:0.2) and stirred at 300 rpm for 1 hour, then reacted in a boiling water bath for 1 hour. After the reaction was completed, the solid was separated, pre-dried at 105℃ for 2 hours, and then heated in an oven at 150℃ for 4 hours. After cooling, it was washed and dried to obtain iron oxide-supported porous carbon material. The porous carbon material supported on iron oxide was mixed with a 0.5 mol / L glycine solution (mass ratio 1:4), heated to 70 °C, and stirred at 200 rpm for 8 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and then dried at 50 °C for 12 h to obtain the surface-modified porous carbon material. Surface-modified porous carbon material was dispersed in a mixed aqueous solution containing sodium citrate and chitosan at a solid-liquid ratio of 1:8, wherein the mass ratio of sodium citrate to chitosan was 1:3. The mixture was stirred at 100 rpm for 8 h at 40 °C and pH 5.0. Subsequently, sodium tripolyphosphate (sodium tripolyphosphate to chitosan mass ratio of 0.2:1) was reacted at 50 °C for 12 h to obtain an iron-based core-shell structured material.

[0024] The preparation method of compound microbial inoculant is as follows: Thermosensitive amyloliquefaciens and Trichoderma reesei were mixed at a live count ratio of 1:0.5 to obtain a composite functional bacterial group. The complex functional microbial community was mixed with sodium alginate, gelatin and dipotassium hydrogen phosphate in a mass ratio of 1:10:5:2 and dispersed in deionized water at a solid-liquid ratio of 1:15 to form a bacterial suspension colloid. The bacterial suspension colloid was then dripped into a 0.2 mol / L calcium chloride solution to form cross-linked microspheres. Microspheres were immersed in a 2% (w / w) mixed solution of gelatin and chitosan, with a mass ratio of 1:2, and adsorbed at 4°C for 4 hours. Then, the temperature was raised to 30°C and held for 1 hour to allow the microspheres to dehydrate and shrink. Finally, the microspheres were vacuum dried at 30°C and 2 kPa absolute pressure to obtain the composite microbial agent.

[0025] Example 2: The difference between this example and Example 1 is that the mass ratio of porous carbon material to ferric sulfate is 1:0.1.

[0026] Example 3: The difference between this example and Example 1 is that the mass ratio of porous carbon material to ferric sulfate is 1:0.3.

[0027] Example 4: The difference between this example and Example 1 is that the mass ratio of the porous carbon material supported by iron oxide to glycine is 1:3.

[0028] Example 5: The difference between this example and Example 1 is that the mass ratio of the iron oxide-supported porous carbon material to glycine is 1:5.

[0029] Example 6: The difference between this example and Example 1 is that the mass ratio of sodium citrate to chitosan is 1:2.

[0030] Example 7: The difference between this example and Example 1 is that the mass ratio of sodium citrate to chitosan is 1:4.

[0031] Specific surface area and pore size distribution determination procedure: Weigh approximately 0.1-0.2 g of sample and place it in a sample tube; degas at 120°C for at least 6 hours under vacuum or inert atmosphere to completely remove surface-adsorbed moisture and gas; transfer the sample tube to the analysis station and perform nitrogen adsorption and desorption tests at liquid nitrogen temperature (77 K) to obtain complete adsorption-desorption isotherms; calculate the specific surface area using the BET equation within a relative pressure (P / P0) range of 0.05-0.35; calculate the mesopore size distribution using the desorption branch data and the BJH model.

[0032] Electrochemical performance (charge transfer resistance) determination procedure: Mix 5 mg of sample, 50 μL of Nafion solution, and 450 μL of isopropanol, and sonicate to form a homogeneous slurry; take an appropriate amount and drop it onto the surface of a glassy carbon electrode, and air dry at room temperature; use the above electrode as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl (saturated KCl) as the reference electrode, in an atmosphere containing 5 mM [Fe(CN)6] 3- / 4- The test was conducted in a 1 mol / L potassium chloride solution; a sinusoidal perturbation with an amplitude of 10 mV was applied at an open-circuit potential, with a frequency range from 100 kHz to 0.01 Hz; the graph was fitted using an equivalent circuit (such as R(QR)), where the charge transfer resistance (QR) was used to measure the resistance of the charge transfer resistance. The size of the electron transport capacity of a material reflects its electron transport ability. The smaller the value, the better the conductivity.

[0033] Table 1 Performance data of iron-based core-shell structure materials Specific surface area Average aperture Charge transfer resistance Example 1 <![CDATA[320m 2 / g]]> 4.2nm 85Ω Example 2 <![CDATA[350m 2 / g]]> 4.5nm 120Ω Example 3 <![CDATA[260m 2 / g]]> 3.8nm 180Ω Example 4 <![CDATA[315m 2 / g]]> 4.1nm 90Ω Example 5 <![CDATA[305m 2 / g]]> 4.0nm 110Ω Example 6 <![CDATA[300m 2 / g]]> 4.0nm 75Ω Example 7 <![CDATA[280m 2 / g]]> 3.7nm 150Ω As the mass ratio of ferric sulfate increased from 1:0.1 (Example 2) to 1:0.3 (Example 3), the specific surface area of ​​the material continuously decreased (from 350 to 260 m²). 2 / g), while the charge transfer resistance shows a trend of first decreasing and then increasing.

[0034] Example 2: Insufficient iron oxide loading prevented full utilization of the porous carbon support surface, thus maintaining a high specific surface area and pore size; however, the insufficient number of active iron species prevented the formation of an effective electronic conduction network, resulting in poor conductivity. Up to 120Ω).

[0035] In Example 1, the iron oxide was relatively uniformly dispersed, providing ample catalytic and electron transfer sites without severely clogging the carbon support pores, thus achieving excellent overall performance (high specific surface area of ​​320 m²). 2 / g and low 85Ω).

[0036] Example 3: Excessive iron salt precursors clogged the micropores and mesopores of carbon materials during heat treatment, leading to a significant decrease in specific surface area. Simultaneously, excessively high local concentrations easily triggered the aggregation of iron oxide particles, not only reducing the effective active area but also severely damaging the conductive pathways, resulting in a dramatic increase in electron transfer resistance. Up to 180Ω).

[0037] Comparing Examples 1, 4, and 5 in Table 1, it can be seen that the specific surface area and pore size are slightly reduced. It then rose slightly.

[0038] Glycine modification mainly affects the surface chemical properties of the material (introducing amino functional groups) and has limited impact on the bulk porous structure. The performance of Example 4 is similar to that of Example 1, indicating that surface amination modification can be effectively completed within this range, which is beneficial for subsequent bonding with the shell.

[0039] Example 5: Excess glycine forms an excessively thick organic molecular layer on the surface of the carbon-iron complex. This slightly obscures some pore entrances (leading to a slight decrease in specific surface area) and slightly increases the tunneling resistance of electrons from the core to the outside (resulting in...). (Increase).

[0040] Comparing Examples 1, 6, and 7 in Table 1, it can be seen that the specific surface area and pore size show a trend of first increasing and then decreasing.

[0041] In Example 6, the amount of chitosan used was relatively small, resulting in a thinner shell layer. However, there was localized uneven coverage, with some carbon surfaces directly exposed, leading to a decrease in specific surface area (300m²). 2 / g) failed to fully reflect the complete porous structure of the material; at the same time, the thin shell layer had little resistance to the electron tunneling effect, exhibiting the lowest (75Ω).

[0042] In Example 7 (mass ratio 1:4), the excessive amount of chitosan resulted in an overly thick and dense shell, which severely blocked the pores of the porous carbon core. Furthermore, the excessively thick organic shell itself experienced pore structure collapse or fusion, leading to a decrease in the overall specific surface area to 280 m². 2 / g; The dense insulating barrier greatly hinders electron exchange, leading to a severe deterioration in conductivity ( (Upgraded to 150Ω).

[0043] Example 8: A method for anaerobic fermentation composting, comprising the following steps: S1.1 After mixing the kitchen waste, add sodium citrate (3% by dry weight of the kitchen waste) and magnesium sulfate (1.2% by dry weight of the kitchen waste), mix at 35°C for 45 minutes to obtain the processed raw material; S1.2. The treated raw materials are fed into an anaerobic reactor, and 0.3% (by dry weight of the treated raw materials) of iron-based core-shell structured material is added. Anaerobic fermentation is carried out at 35°C. The pH of the fermentation system is controlled at 7.0 using a 20% sodium hydroxide solution, and the organic loading rate is 3.0 kgVS / (m³). 3 ·d), the fermentation time is 25 days, and digestion residue is obtained; S1.3. Add 2.0% sodium bicarbonate and 1.2% sodium citrate by weight of the digestion residue (wet basis) to the digestion residue, and mix and stir at 35℃ for 30 minutes. Then, carry out aerobic composting. At the initial stage of aerobic composting, add 0.5% amphoteric organic salt (a mixture of aspartic acid and betaine, with a mass ratio of 1:3) and 1.2% compound microbial agent by weight of the digestion residue (wet basis). Control the moisture content of the compost pile to 60%, and provide oxygen and forced ventilation (ventilation volume of 0.3 m³ / h). 3 Under the condition of / (min·t)), the temperature of the pile is raised to 60℃ and maintained for 7 days before entering the decomposition stage. After natural aging, decomposed organic fertilizer is obtained.

[0044] The preparation method of iron-based core-shell structured materials is as follows: Pretreated wood was pyrolyzed at 650℃ for 4 hours under nitrogen protection to obtain porous carbon material. The porous carbon material was mixed with 0.5 mol / L ferric sulfate solution (mass ratio 1:0.2) and stirred at 400 rpm for 1 hour, then reacted in a boiling water bath for 2 hours. After the reaction was completed, the solid was separated, pre-dried at 105℃ for 2 hours, and then heated in an oven at 180℃ for 3 hours. After cooling, it was washed and dried to obtain iron oxide-supported porous carbon material. The porous carbon material supported on iron oxide was mixed with a 0.5 mol / L glycine solution (mass ratio 1:4), heated to 80 °C, and stirred at 300 rpm for 6 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and then dried at 60 °C for 10 h to obtain the surface-modified porous carbon material. Surface-modified porous carbon material was dispersed in a mixed aqueous solution containing sodium citrate and chitosan at a solid-liquid ratio of 1:8, wherein the mass ratio of sodium citrate to chitosan was 1:3. The mixture was stirred at 150 rpm for 6 h at 50 °C and pH 5.5. Subsequently, sodium tripolyphosphate (sodium tripolyphosphate to chitosan mass ratio of 0.6:1) was reacted at 60 °C for 10 h to obtain an iron-based core-shell structured material.

[0045] The preparation method of compound microbial inoculant is as follows: Thermosensitive amyloliquefaciens and Trichoderma reesei were mixed at a live count ratio of 1:0.5 to obtain a composite functional bacterial group. The complex functional microbial community was mixed with sodium alginate, gelatin and dipotassium hydrogen phosphate in a mass ratio of 1:10:5:2 and dispersed in deionized water at a solid-liquid ratio of 1:20 to form a bacterial suspension colloid. The bacterial suspension colloid was then dripped into a 0.4 mol / L calcium chloride solution to form cross-linked microspheres. Microspheres were immersed in a 4% (w / w) mixed solution of gelatin and chitosan, with a mass ratio of 1:2, and adsorbed at 8°C for 3 hours. Then, the temperature was raised to 35°C and held for 2 hours to allow the microspheres to dehydrate and shrink. Finally, the microspheres were vacuum dried at 32°C and 5 kPa absolute pressure to obtain the composite microbial agent.

[0046] Example 9: The difference between this example and Example 8 is that the amount of iron-based core-shell structure material added accounts for 0.1% of the dry basis mass of the treated raw material.

[0047] Example 10: The difference between this example and Example 8 is that the amount of iron-based core-shell structure material added accounts for 0.5% of the dry basis mass of the treated raw material.

[0048] Example 11: The difference between this example and Example 8 is that a compound microbial agent accounting for 0.5% of the wet mass of the digested residue is added at the beginning of aerobic composting.

[0049] Example 12: The difference between this example and Example 8 is that a compound microbial agent accounting for 2.0% of the wet mass of the digested residue is added at the beginning of aerobic composting.

[0050] Example 13: A method for anaerobic fermentation composting, comprising the following steps: S1.1 After mixing the kitchen waste, add 5% sodium citrate and 2.0% magnesium sulfate by dry weight of the kitchen waste, and mix at 40℃ for 30 minutes to obtain the processed raw material; S1.2. The treated raw materials are fed into an anaerobic reactor, and 0.3% (by dry weight of the treated raw materials) of iron-based core-shell structured material is added. Anaerobic fermentation is carried out at 38℃, and the pH of the fermentation system is controlled at 8.0 using a 30% sodium hydroxide solution. The organic loading rate is 4.0 kgVS / (m³). 3 ·d), the fermentation time is 30 days, and digestion residue is obtained; S1.3. Add 3.0% sodium bicarbonate and 2.0% sodium citrate by weight of the digestion residue (wet basis) to the digestion residue and mix at 50°C for 10 minutes. Then proceed with aerobic composting. At the initial stage of aerobic composting, add 1.0% amphoteric organic salt (a mixture of aspartic acid and betaine in a 1:3 mass ratio) and 1.2% compound microbial inoculant by weight of the digestion residue (wet basis). Control the moisture content of the compost pile to 65%. Provide oxygen and forced ventilation (ventilation volume of 0.5 m³ / h).3 Under the condition of / (min·t)), the temperature of the pile is raised to 70℃ and maintained for 7 days before entering the decomposition stage. After natural aging, decomposed organic fertilizer is obtained.

[0051] The preparation method of iron-based core-shell structured materials is as follows: Pretreated wood was pyrolyzed at 800℃ for 2 hours under nitrogen protection to obtain porous carbon material. The porous carbon material was mixed with 0.5 mol / L ferric sulfate solution (mass ratio 1:0.2) and stirred at 500 rpm for 0.5 hours, then reacted in a boiling water bath for 2 hours. After the reaction was completed, the solid was separated, pre-dried at 105℃ for 2 hours, and then heated in an oven at 200℃ for 2 hours. After cooling, it was washed and dried to obtain iron oxide-supported porous carbon material. The porous carbon material supported on iron oxide was mixed with a 0.5 mol / L glycine solution (mass ratio 1:4), heated to 90 °C, and stirred at 400 rpm for 4 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and then dried at 70 °C for 10 h to obtain the surface-modified porous carbon material. Surface-modified porous carbon material was dispersed in a mixed aqueous solution containing sodium citrate and chitosan at a solid-liquid ratio of 1:8, wherein the mass ratio of sodium citrate to chitosan was 1:3. The mixture was stirred at 200 rpm for 4 h at 60 °C and pH 6.0. Subsequently, sodium tripolyphosphate (sodium tripolyphosphate to chitosan mass ratio of 1.0:1) was added at 15% of the mass of chitosan, and the mixture was reacted at 70 °C for 6 h to obtain an iron-based core-shell structured material.

[0052] The preparation method of compound microbial inoculant is as follows: Thermosensitive amyloliquefaciens and Trichoderma reesei were mixed at a live count ratio of 1:0.5 to obtain a composite functional bacterial group. The complex functional microbial community was mixed with sodium alginate, gelatin and dipotassium hydrogen phosphate in a mass ratio of 1:10:5:2 and dispersed in deionized water at a solid-liquid ratio of 1:30 to form a bacterial suspension colloid. The bacterial suspension colloid was then dripped into a 0.5 mol / L calcium chloride solution to form cross-linked microspheres. Microspheres were immersed in a 5% (w / w) mixed solution of gelatin and chitosan, with a mass ratio of 1:2, and adsorbed at 10°C for 2 hours. The temperature was then raised to 35°C and maintained for 2 hours to allow the microspheres to dehydrate and shrink. Finally, the microspheres were vacuum dried at 35°C and 8 kPa absolute pressure to obtain the composite microbial agent.

[0053] Determination of maturity (seed germination index (GI)): Take 10g of mature fertilizer sample and mix it in an Erlenmeyer flask at a solid-liquid ratio of 1:10 (e.g., 10g sample to 100mL deionized water); place the Erlenmeyer flask in a constant temperature shaker and shake and extract for 1 hour at 25℃ and 150rpm; filter the extract with medium-speed qualitative filter paper and collect the filtrate; evenly place 10-20 plump cucumber or cabbage seeds in a petri dish lined with filter paper; add 5mL of the above filtrate to the petri dish (using deionized water as a control); place the petri dish in a dark chamber at 25℃ for 48-72 hours; count the number of germinated seeds and measure the root length with vernier calipers; calculate: GI (%) = (sample germination rate × sample root length) / (control germination rate × control root length) × 100%.

[0054] Total Nitrogen (TN) Determination Procedure (using Kjeldahl method): Weigh 0.5 g (accurate to 0.0001 g) of the air-dried and ground sample, and digest it together with sulfuric acid and catalyst in a Kjeldahl flask at high temperature on a digestion furnace until the solution turns a clear blue-green color; transfer the digestion solution to an automatic Kjeldahl distillation apparatus, add excess sodium hydroxide solution, distill off the ammonia, and absorb it with boric acid solution; titrate the absorbent solution with standard hydrochloric acid solution; calculate the nitrogen content in the sample based on the amount of hydrochloric acid consumed.

[0055] Procedure for determining total phosphorus (TP) and total potassium (TK): Weigh the sample and digest it using a nitric acid-hydrogen peroxide system via microwave. After bringing the digestion solution to a final volume and filtering, directly determine the concentrations of phosphorus and potassium using an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0056] Total organic carbon (TOC) determination procedure: The dry burning method (high-temperature combustion oxidation method) is usually used; the sample is burned under high temperature and oxygen-rich conditions, and the carbon dioxide produced is detected by an infrared detector to calculate the total organic carbon content.

[0057] The seed germination index (GI) and nutrient indicators shown in Table 2 were all measured on samples after the decomposition stage and aging treatment.

[0058] Table 2 Performance data of well-rotted organic fertilizer

[0059] As can be seen from the comparison of Examples 8, 9 and 10 in Table 2, Example 9 has insufficient iron, which leads to insufficient degradation and stabilization of organic matter in the anaerobic stage. This results in poor quality of raw materials (digestion residue) for subsequent composting, stubborn carbon sources, and ultimately low degree of compost humification (GI only 85%) and insufficient nutrient conversion (low total nitrogen, phosphorus and potassium), but high residual organic carbon (TOC).

[0060] Example 8 achieved the optimal balance; the iron-based material effectively promoted the degradation in the anaerobic stage, and its porous structure and iron active sites continued to play a role in the subsequent composting, which promoted the formation and polymerization of humic acid, thereby obtaining the highest degree of composting (GI of 91%) and ideal nutrient and carbon content.

[0061] Example 10: Excessive iron can inhibit the activity of certain microorganisms; its core function is to strongly promote the humification process of composting, that is, the transformation of organic matter into stable humus; this is a process that consumes organic carbon and releases energy, so it is manifested as a decrease in TOC (35%), but at the same time, the degree of humification is high (GI is 88%) and the nutrient concentration effect is obvious (total nitrogen, phosphorus and potassium are the highest).

[0062] As can be seen from the comparison of Examples 8, 11 and 12 in Table 2, Example 11 has an insufficient number of exogenous functional bacteria, and the compost mainly relies on indigenous microorganisms, resulting in low overall decomposition efficiency. This is manifested in slow heating and incomplete degradation of organic matter, thus resulting in the lowest degree of composting (GI of 83%) and nutrient content, while the highest amount of undecomposed organic carbon residue (TOC of 41%).

[0063] In Example 12, the high addition amount (2.0%) of the compound microbial agent affected the composting process pattern: In the early stage of composting, the exogenous functional microbial community became dominant, converting a large amount of easily degradable carbon sources into intracellular energy storage substances (such as PHA) and extracellular polymeric substances (EPS). This process rapidly consumed soluble organic carbon, leading to a reduction in the mineralizable carbon pool in the later stage and a decrease in total organic carbon (TOC) (33%). However, this is different from the process of drastic and singular mineralization into CO2. In order to meet the needs of rapid proliferation and anabolism, the microbial cells converted the nitrogen source in the system into... (Including ammonia produced by mineralization) is efficiently assimilated into substances such as microbial proteins, achieving rapid biological fixation of nitrogen; at the same time, the dominance of exogenous microbial communities temporarily inhibits the active ammonifying and nitrifying bacteria in native microorganisms, reducing the conversion of nitrogen to gaseous form from the pathway; therefore, although carbon loss is significant, nitrogen is largely retained in the form of microbial biomass nitrogen and stable microbial-derived organic nitrogen, showing the highest total nitrogen (TN) (2.5%); however, this model sacrifices the persistence of organic carbon (low TOC) and is less economical.

[0064] Based on the above measurements, and taking into account the degree of decomposition, nutrient retention, organic carbon pool value, and inoculant usage cost, Example 8 has better economic efficiency and resource utilization benefits while ensuring high product quality. Therefore, Example 8 is selected as the optimal example. Comparative Example 1: The difference between this example and Example 8 is that no iron-based core-shell structure material and composite microbial agent were added.

[0065] Comparative Example 2: The difference between this example and Example 8 is that the iron-based core-shell structure material is replaced with ferrous sulfate.

[0066] Comparative Example 3: The difference between this example and Example 8 is that the compound microbial agent is replaced with Bacillus subtilis preparation.

[0067] Comparative Example 4: The difference between this example and Example 8 is that no amphoteric organic salt was added.

[0068] Methanogenic efficiency determination steps: During the anaerobic fermentation process, the biogas production was measured and recorded daily using a wet gas flow meter, and the methane volume fraction in the biogas was analyzed by a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD). The cumulative methane production (L) was calculated from the daily biogas production and the corresponding methane volume fraction. Methanogenic efficiency = (cumulative methane production (L) × average methane content (%) × 1000) / total VS mass of feed (g). The volatile solids (VS) content was determined by gravimetric method: the sample was dried at 105℃ to constant weight to obtain the total solids (TS), and then calcined in a muffle furnace at 550℃ for 4 hours to obtain the ash content. VS = TS - ash content.

[0069] Table 3 Performance data of well-rotted organic fertilizer

[0070] Compared with Example 8, Comparative Example 1 showed a comprehensive deterioration in all indicators; the GI was only 72%, indicating incomplete decomposition and a risk of phytotoxicity; the nutrient content was the lowest; but the TOC was the highest.

[0071] The proportion lacks iron-based materials, resulting in instability during the anaerobic stage, a high risk of acid production, and difficulty in initiating subsequent composting; it also lacks compound microbial agents, leading to slow degradation of cellulose and other materials during the aerobic stage, and a short or insignificant high-temperature period; ultimately resulting in incomplete material decomposition, poor maturity, and low nutrient retention.

[0072] Compared with Example 8, Comparative Example 2 was better than Comparative Example 1 in all aspects but lower than Example 8; GI (80%) did not reach the complete maturity line.

[0073] While ordinary ferrous sulfate can provide iron ions, it lacks the adsorption and buffering effect of porous carbon carriers and the slow-release protection of core-shell structures. Iron ions are easily lost, deactivated, or precipitated as iron sulfide in anaerobic systems, making it difficult to sustain its function of promoting electron transfer and stabilizing pH. It also cannot provide additional microbial habitats during the composting stage.

[0074] Compared with Example 8, Comparative Example 3 had a GI (85%) that just reached the maturity level, and its nutrient and TOC indices were average.

[0075] Common Bacillus subtilis has a single function, mainly degrading easily decomposable substances such as starch and protein, and has limited ability to degrade stubborn components such as cellulose and lignin commonly found in kitchen waste; moreover, common formulations of bacteria are easily inactivated in the high-temperature and highly competitive environment of composting.

[0076] The indicators of Comparative Example 4 (without added amphoteric organic salts) were slightly lower than those of Example 8 but better than those of other comparative examples. Among them, the seed germination index (GI) was 88%, which was lower than that of Example 8 (91%), indicating that amphoteric organic salts helped to further improve the maturity of composting. This is because amphoteric organic salts, through their osmotic regulation function, helped microorganisms maintain their activity in the high-salt or osmotic pressure fluctuation environment at the beginning of composting, thereby initiating the degradation process more quickly. At the same time, as a methyl donor, it promoted some key metabolic pathways. The contents of total nitrogen (2.1%), total phosphorus (1.7%), and total potassium (1.9%) were slightly lower than those of Example 8, indicating that amphoteric organic salts promoted the biological fixation and retention of nutrients during composting by maintaining microbial activity.

[0077] Table 4. Anaerobic fermentation methanogenesis performance data of Comparative Examples 1-4 and Example 8

[0078] As shown in Table 4, Example 8 (with added iron-based core-shell structure material and amphoteric organic salt) had the highest methanogenesis efficiency (510 mL CH4 / g VS); Comparative Example 1 (without added iron-based material and compound bacterial agent) had the lowest efficiency (180 mL CH4 / g VS), indicating that iron-based material promotes electron transfer; Comparative Example 2 (with ferrous sulfate instead of iron-based material) had an efficiency (245 mL CH4 / g VS) higher than Comparative Example 1 but lower than Example 8, confirming the importance of porous core-shell structure carriers.

[0079] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for integrating anaerobic fermentation composting, characterized in that, Includes the following steps: S1.1 After mixing the organic waste raw materials, add sodium citrate (1-5% by dry weight of the organic waste raw materials) and magnesium sulfate (0.5-2.0% by dry weight of the organic waste raw materials), and mix at 15-40℃ for 30-60 minutes to obtain the treated raw materials. S1.

2. The treated raw materials are fed into an anaerobic reactor, iron-based core-shell structure material is added, and anaerobic fermentation is carried out at 30-38℃. The pH of the fermentation system is controlled at 6.5-8.0 with a sodium hydroxide solution of 10-30% by mass. The fermentation time is 10-30 days to obtain digestion residue. S1.3 Add 0.5-3.0% of the wet weight of bicarbonate and 0.2-2.0% of sodium citrate to the digestion residue, mix and stir for 10-40 minutes at 20-50℃; then carry out aerobic composting, control the moisture content of the compost to 50-65%, and raise the temperature of the compost to 55-70℃ under oxygen supply conditions and maintain it for 3-7 days to enter the decomposition stage. After natural aging, decomposed organic fertilizer is obtained.

2. The method for fusion anaerobic fermentation composting according to claim 1, characterized in that, In S1.1, the organic waste raw materials are one or more of the following: kitchen waste, livestock and poultry manure, and sludge.

3. The method for fusion anaerobic fermentation composting according to claim 1, characterized in that, In step S1.2, the amount of iron-based core-shell structure material added accounts for 0.1-0.5% of the dry weight of the treated raw material; The preparation method of iron-based core-shell structured materials is as follows: Pretreated wood was pyrolyzed at 500-800℃ for 2-6 hours under nitrogen protection to obtain porous carbon material. The porous carbon material was mixed with 0.5 mol / L ferric sulfate solution and stirred at 300-500 rpm for 0.5-1.0 hours, then reacted in a boiling water bath for 1-2 hours. After the reaction was completed, the solid was separated, pre-dried at 105℃ for 2 hours, and then heated in an oven at 150-200℃ for 2-4 hours. After cooling, it was washed and dried to obtain iron oxide-supported porous carbon material. The porous carbon material supported on iron oxide was mixed with a 0.5 mol / L glycine solution, heated to 70-90℃, and stirred at 200-400 rpm for 4-8 h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water, and then dried at 50-70℃ for 10-12 h to obtain the surface-modified porous carbon material. Surface-modified porous carbon material was dispersed in a mixed aqueous solution containing sodium citrate and chitosan at a solid-liquid ratio of 1:8 and stirred at 100-200 rpm for 4-8 h at 40-60℃ and pH 5.0-6.

0. Sodium tripolyphosphate was then added and reacted at 50-70℃ for 6-12 h to obtain an iron-based core-shell structured material.

4. The method for fusion anaerobic fermentation composting according to claim 3, characterized in that, The mass ratio of the porous carbon material to ferric sulfate is 1:0.1-0.3; The mass ratio of iron oxide-supported porous carbon material to glycine is 1:3-5.

5. The method for fusion anaerobic fermentation composting according to claim 3, characterized in that, The mass ratio of sodium citrate to chitosan is 1:2-4; The mass ratio of sodium tripolyphosphate to chitosan is 0.2-1.0:

1.

6. The method for fusion anaerobic fermentation composting according to claim 1, characterized in that, In step S1.2, the organic loading rate for anaerobic fermentation is 1.0-4.0 kgVS / (m³). 3 ·d).

7. The method for fusion anaerobic fermentation composting according to claim 1, characterized in that, In S1.3, the bicarbonate is sodium bicarbonate or ammonium bicarbonate.

8. The method for fusion anaerobic fermentation composting according to claim 1, characterized in that, In S1.3, 0.1-1.0% of the wet weight of the digested residue is added during the initial stage of aerobic composting; The amphoteric organic salt is a mixture of aspartic acid and betaine in a mass ratio of 1:

3.

9. The method for fusion anaerobic fermentation composting according to claim 1, characterized in that, In step S1.3, a compound microbial agent accounting for 0.5-2.0% of the wet weight of the digested residue is added at the initial stage of aerobic composting; The preparation method of the compound microbial agent is as follows: Thermosensitive amyloliquefaciens and Trichoderma reesei were mixed at a live count ratio of 1:0.5 to obtain a composite functional bacterial group. The complex functional microbial community was mixed with sodium alginate, gelatin and dipotassium hydrogen phosphate in a mass ratio of 1:10:5:2 and dispersed in deionized water at a solid-liquid ratio of 1:15-30 to form a bacterial suspension colloid. The bacterial suspension colloid was then dripped into a 0.2-0.5 mol / L calcium chloride solution to form cross-linked microspheres. Microspheres were immersed in a mixed solution of gelatin and chitosan with a mass concentration of 2-5% (mass ratio of gelatin to chitosan 1:2) and adsorbed at 4-10℃ for 2-4 hours. Then, the temperature was raised to 30-35℃ and maintained for 1-2 hours to dehydrate and shrink the microspheres. Finally, the microspheres were vacuum dried at 30-35℃ and an absolute pressure of 2-8 kPa to obtain the composite microbial agent.

10. The method for fusion anaerobic fermentation composting according to claim 1, characterized in that, In step S1.3, forced ventilation is used during the aerobic composting process, with a ventilation volume of 0.1-0.5 m³. 3 / (min·t).

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