Application of a novel composite material in reducing nitrogen loss during composting

Abstract

This invention provides an application of a novel composite material in reducing nitrogen loss during composting. The method includes: a pile-building stage, in which a porous stabilizer is added to the mixed raw materials, and fermentation is carried out by bottom aeration and airflow membrane covering after pile building; a high-temperature control stage, in which biomass carriers pretreated with sodium humate, fulvic acid, and wood vinegar are injected into the pile in a grid pattern after the pile temperature reaches 50°C; and a post-maturation and bio-enhancing stage, in which biochar loaded with iron oxide is added, and a solid inoculant containing Acetobacter xylinum and fructose amino acid oxidase is applied to the surface of the pile, and the pile is turned lightly at regular intervals. This invention constructs a nitrogen preservation system that combines physical barrier control, chemical fixation, and biological assimilation through the sequential synergy of multiple materials such as porous stabilizers, functionalized biomass carriers, biochar, and inoculants, which can significantly reduce nitrogen loss during composting and improve compost quality.

Description

Technical Field

[0001] This invention belongs to the field of composting technology, specifically relating to the application of a novel composite material in reducing nitrogen loss during composting. Background Technology

[0002] Composting, as a key technology for the resource utilization of organic waste, plays an important role in waste treatment and sustainable agricultural development. However, traditional composting processes generally suffer from severe nitrogen loss, typically as high as 30%-60% of the initial total nitrogen. This not only represents a huge waste of resources but also reduces the agricultural value of compost products and may cause environmental pollution.

[0003] Nitrogen loss during composting mainly occurs in three key stages: First, in the initial stage of composting, compaction and uneven porosity of the material lead to localized anaerobic conditions, triggering nitrification-denitrification and causing nitrogen loss. Second, during the high-temperature stage, rapid mineralization of organic matter releases large amounts of ammonium nitrogen, which volatilizes as ammonia under higher pH and temperature conditions. Third, during the post-ripening stage, unfixed nitrogen may still be lost through leaching or secondary volatilization. While existing technologies have attempted to suppress ammonia volatilization through physical covering, adding adsorbents (such as zeolite or clay), or adjusting pH (such as adding superphosphate), these methods are often limited in function, short-lived, and poorly adaptable, making it difficult to achieve synergistic control across multiple stages of the entire process. For example, while ordinary covering materials can reduce ammonia volatilization, they often hinder oxygen transport, exacerbating the anaerobic environment; chemical additives may affect microbial activity or compost quality; and conventional aeration methods often result in uneven oxygen supply, failing to achieve dynamic matching of oxygen supply and demand.

[0004] Furthermore, existing methods often focus on nitrogen retention at a single stage, lacking a systematic intervention strategy covering the entire chain from composting initiation and high-temperature treatment to maturity. This results in limited nitrogen fixation efficiency and fails to convert the retained nitrogen into a stable form easily absorbed by plants. Therefore, developing a composite material system capable of operating throughout the entire composting process and synergistically integrating physical regulation, chemical fixation, and biotransformation has become a critical challenge in current composting nitrogen retention technology. Solving this problem can significantly improve the nitrogen nutrient content and stability of compost products, enhancing their agronomical and economic value as organic fertilizer. It can also reduce greenhouse gas and ammonia emissions, providing significant environmental and economic benefits for promoting the efficient resource utilization of organic solid waste and fostering green and circular agricultural development. Summary of the Invention

[0005] This invention discloses the application of a novel composite material in reducing nitrogen loss during composting, to solve any of the aforementioned and potential problems in the prior art. To address the above-mentioned technical problems, a novel composite material is provided for reducing nitrogen loss during composting, comprising a composting stage, a high-temperature control stage, and a post-maturation stage. The composting stage includes: mixing 60-80 parts by weight of straw, 20-30 parts by weight of kitchen waste, 10-20 parts by weight of livestock and poultry manure, 0.1-0.3 parts by weight of urea, and 0.05-0.1 parts by weight of nano-iron oxide, with an initial C / N ratio of 25:1 to 30:1 and a moisture content of 60% to 65%; then adding a porous stabilizer at a ratio of 3.5-5.5% by weight of the mixed materials, achieving a total viable count ≥1.0 × 10⁻⁶. 8 The EM stock solution, diluted at a volume ratio of 1:100, was evenly sprayed onto the surface of the pile at a ratio of 0.1% of the total mass of the pile. Simultaneously, potassium pyrophosphate was added at a ratio of 0.2-0.5% of the mixed raw materials. The mixture was stirred at 60 rpm for 15 minutes. The mixture was then constructed into windrows 0.5-1.3 meters long, 0.5-1.2 meters wide, and 0.5-0.8 meters high. Aeration pipes were laid at the bottom of the windrows, and the piles were covered with an airflow membrane. A 3.7 kW blower with an aeration rate of 100 L / min was used to supply oxygen for fermentation through the bottom aeration pipes.

[0006] The porous stabilizer comprises: dry mixing steel slag powder and rice husk ash (passed through a 200-mesh sieve) in a mixer at a mass ratio of 1:150 for 15 minutes; then adding 0.5% nano-iron oxide and 2% bentonite (by mass of the dry mixture) and mixing for another 10 minutes; adding water while stirring, with the amount of water controlled to be 12-15% of the total mass of the dry powder; feeding the above wet material into a granulator to prepare uniform raw material balls with a diameter of 3-5 cm; drying the raw material balls at 105℃ for 4 hours, then placing them in a box-type resistance furnace, first heating to 750℃ at 3℃ / min and holding for 1 hour; then continuing to heat to 950℃ at 5℃ / min and holding for 1.5 hours to obtain the porous stabilizer.

[0007] The high-temperature control stage includes: when the temperature of the pile reaches 50°C, the pre-prepared biomass carriers are vertically injected into the middle and upper layers of the pile at a grid pattern with a spacing of 0.8 meters, with a depth not exceeding 30 cm. The total injected mass is 0.5-1.0% of the initial mass of the pile. The surface of the pile is then slightly turned over and covered with a thin airflow film again. This stage lasts for 10-15 days.

[0008] The preparation of the biomass carrier includes: taking straw and crushing it into 1-2cm fragments, mixing it with functional mixed liquid at a mass ratio of 1:0.5 and pre-treating it by heaping for 24 hours. The functional mixed liquid is a mixture of sodium humate, fulvic acid and wood vinegar at a mass ratio of 100:100:1, and the mass fraction of the mixture is 3-5%.

[0009] The post-maturation stage includes: when the temperature of the pile naturally drops below 40℃, self-made biochar is added at a ratio of 0.5-1.0% of the total mass of the pile and the pile is turned over completely; subsequently, in order to prioritize the establishment of dominant microbial communities in areas with sufficient oxygen, solid microbial agents are evenly applied at a ratio of 0.1-0.2% of the total mass of the pile in the 0-50 cm depth area on the surface of the pile, and the pile is covered with breathable non-woven fabric, entering a 20-30 day aging and stabilization period, during which the pile is turned over every 7-10 days.

[0010] The self-made biochar process includes: drying tea leaves at 105℃ to constant weight, pulverizing them through an 80-mesh sieve, and mixing them with hematite powder at a mass ratio of 10:1 in a mixer for 30 minutes until homogeneous; placing the mixture in a tube furnace, introducing nitrogen at a flow rate of 200 mL / min, and heating it to 500℃ at a set program of 10℃ / min, and then pyrolyzing and carbonizing it at this temperature for 2 hours; after pyrolysis, cooling it to room temperature under continuous nitrogen protection to obtain the primary biochar product; subsequently, placing this primary product and goethite at a mass ratio of 1:1 in a ball mill, and ball milling it at a speed of 300 rpm for 4 hours, pausing and reversing the rotation for 10 minutes every 30 minutes to ensure uniform mixing, and finally obtaining the self-made biochar.

[0011] The preparation of solid bacterial agents includes: preparing bacterial strains with a viable count ≥1×10⁻⁶. 9 A compound bacterial enzyme solution is prepared by mixing CFU / mL Acetobacter xylinum bacterial solution with a fructose amino acid oxidase solution at a concentration of 50-100 mg / mL at a volume ratio of 2:1. Then, wheat bran is mixed with the compound bacterial enzyme solution at a solid-liquid ratio of 1:0.3-0.4.

[0012] The advantages and beneficial effects of this invention are as follows:

[0013] This invention provides an application of a novel composite material in reducing nitrogen loss during composting. Its core advantage lies in constructing a synergistic, multi-level, and multifunctional composite material system. This system precisely and efficiently intervenes in the nitrogen loss process throughout composting, significantly reducing nitrogen loss at its source and substantially improving the stability and nutrient value of the final compost product.

[0014] Firstly, during the composting stage, the introduction of a special porous stabilizer and an airflow membrane aeration system creates an ideal basic physical and microenvironment for efficient, low-nitrogen composting. The porous stabilizer is not a simple filler, but a functional material made from steel slag powder, rice husk ash, nano-iron oxide, and bentonite through granulation and high-temperature sintering. It forms a rich and stable multi-level porous structure, which, after being added to the compost pile, significantly improves the porosity and permeability of the material, ensuring uniform oxygen distribution and avoiding nitrification-denitrification nitrogen loss caused by localized anaerobic conditions. Simultaneously, the alkaline minerals and iron provided by the steel slag powder and rice husk ash gently regulate the pH of the compost pile and catalyze certain reactions. Combined with the oxygen supply method of bottom aeration pipes and the airflow membrane covering the pile, a dynamic match between the oxygen supply rate and the needs of the compost pile is achieved. While maintaining heat and moisture, the airflow membrane allows some water vapor and carbon dioxide to escape, but effectively blocks the direct volatilization of large amounts of ammonia, retaining most of it within the membrane circulation system, thus creating conditions for subsequent chemical fixation.

[0015] Secondly, during the high-temperature control phase, deep chemical fixation of nitrogen was achieved through the grid-like injection of biomass carriers pretreated with functional mixed liquid. When the pile temperature rose above 50℃ (the critical period for ammonia volatilization), the "biomass carriers" injected into key areas of the pile played a crucial role. The carriers themselves (straw fragments) can adsorb ammonia. More importantly, the functional mixed liquid they support, composed of sodium humate, fulvic acid, and wood vinegar, can precisely target the high-temperature zone. Sodium humate and fulvic acid are rich in active functional groups such as carboxyl and phenolic hydroxyl groups, which can undergo strong ion exchange and complexation reactions with ammonium ions, converting volatile inorganic nitrogen into stable organic complex nitrogen. The acidity of the wood vinegar can locally fine-tune the pH at the injection point, inhibiting ammonia generation. The combination of these three components forms a synergistic system. This point-to-point intervention fundamentally avoids the rapid release and gaseous loss of nitrogen caused by the intense mineralization during the high-temperature period. A single component cannot simultaneously achieve rapid fixation and microenvironment control.

[0016] Finally, in the post-curing stage, by sequentially adding self-made biochar and solid microbial agents, and employing a "surface inoculation-gradual mixing" method, the ultimate stabilization and bioconversion of nitrogen were achieved. The added self-made biochar (made from tea residue loaded with hematite and goethite through a composite process) has both well-developed pores and active sites for iron oxides, which can strongly adsorb and retain various forms of nitrogen fixed in the early stage, preventing its leaching in the later stage. Subsequently, the solid microbial agent (containing Acetobacter xylinum and fructose amino acid oxidase) was uniformly applied in the 0-50 cm oxygen-enriched zone on the surface of the pile, preferentially and rapidly colonizing and proliferating in this suitable environment. Fructose amino acid oxidase accelerates the degradation of nitrogen-containing organic matter, releasing nitrogen sources, while microorganisms such as Acetobacter xylinum rapidly assimilate these nitrogen sources, converting them into microbial protein (biomass nitrogen). If only enzymes are used, nitrogen release is too rapid and easily lost; if only bacteria are used, the nitrogen source supply is insufficient and the fixation efficiency is low. The combination of the adsorption protection of biochar loaded with iron oxides and the "surface inoculation-gradual mixing" method ensures that the microbial agent preferentially colonizes in the oxygen-enriched zone. Through subsequent periodic light turning, these active microbial communities and biochar carriers are gradually mixed into the deeper layers of the compost pile, achieving biofortification of the entire pile. This process not only ultimately fixes nitrogen within stable microorganisms but also transforms it into a high-quality organic nitrogen form that is easily absorbed by plants, significantly improving the biological fertilizer efficiency and agricultural value of the compost.

[0017] In summary, this invention forms a full-chain nitrogen preservation mechanism for compost by sequentially and synergistically applying functional composite materials in three stages, thereby minimizing nitrogen loss and maximizing the quality of compost products. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the embodiments. The airflow membrane used in the following embodiments is a Gore membrane, purchased from Yangzhou Xingqiao Energy Technology Co., Ltd. The self-made biochar added in the following embodiments is prepared as follows: Tea leaves are dried to constant weight at 105°C and then pulverized and passed through an 80-mesh sieve. 10 kg of the powder is mixed with 1 kg of hematite powder for 30 minutes. The mixture is placed in a tube furnace, and nitrogen gas is introduced at a flow rate of 200 mL / min. The temperature is increased to 500°C at a set program of 10°C / min, and pyrolyzed and carbonized at this temperature for 2 hours. After pyrolysis, the mixture is cooled to room temperature under continuous nitrogen protection to obtain the primary biochar product. Subsequently, this primary product is mixed with goethite at a mass ratio of 1:1 in a ball mill and ball-milled at a speed of 300 rpm for 4 hours. During the process, the mill is paused every 30 minutes and rotated in the opposite direction for 10 minutes to ensure uniform mixing, and the self-made biochar is finally obtained.

[0019] Example 1

[0020] Preparation of porous stabilizer: 0.1 kg of steel slag powder (passed through a 200-mesh sieve) and 15 kg of rice husk ash were placed in a mixer and dry-mixed for 15 minutes. Then, 0.5% nano-iron oxide and 2% bentonite (by mass of the dry mixture) were added, and mixing continued for 10 minutes. Water was added while stirring, with the amount controlled to 14% of the total mass of the dry powder. The wet material was fed into a granulator to form raw material balls with a diameter of 4.0 cm. The raw material balls were dried at 105℃ for 4 hours, then placed in a box-type resistance furnace. The temperature was first increased to 750℃ at 3℃ / min and held for 1 hour, then increased to 950℃ at 5℃ / min and held for 1.5 hours. After cooling, the porous stabilizer was obtained.

[0021] Composting stage: Mix 70kg of straw, 25kg of kitchen waste, 15kg of livestock and poultry manure, 0.20kg of urea, and 0.075kg of nano-iron oxide. The initial C / N ratio of the mixed raw materials was determined to be 27.5:1, and the moisture content was 62.5% (adjusted by adding 68.7kg of water). Then, a porous stabilizer was added at a ratio of 4.5% by mass of the mixed raw materials, and the total viable bacteria count was ≥1.0×10⁻⁶. 8 An EM stock solution of CFU / mL was diluted 1:100 by volume and sprayed evenly onto the surface of the pile at a rate of 0.1% of the total mass of the pile. 0.625 kg of potassium pyrophosphate was added, and the mixture was stirred at 60 rpm for 15 minutes using a mixer. The material was then stacked into windrows measuring 1.0 m (length) × 0.85 m (width) × 0.65 m (height), with aeration pipes laid at the bottom and covered with an airflow membrane. A 3.7 kW blower was used to continuously supply oxygen for fermentation at a rate of 100 L / min through the bottom pipes.

[0022] Preparation of biomass carrier: The straw was crushed into 1.5cm fragments, and 1.00kg of the fragments were mixed with 0.50kg of functional mixture. The functional mixture was prepared by dissolving 200g of sodium humate, 200g of sodium fulvicate and 2.0g of wood vinegar in deionized water to obtain a 4.0% mass fraction mixture. The mixture was then pretreated by mixing and pressing for 24 hours to obtain the biomass carrier.

[0023] High-temperature control stage: When the temperature of the pile reaches 50°C, the pre-prepared biomass carriers are vertically injected into the middle and upper layers of the pile at a grid pattern with a spacing of 0.8 meters and a depth of 20 cm. The total injected mass is 0.8% of the initial mass of the pile. The surface of the pile is then slightly turned over and covered with a thin airflow film again. This stage lasts for 12 days.

[0024] Post-curing stage: When the pile temperature naturally drops below 40℃, add self-made biochar at a ratio of 0.8% of the total pile mass and thoroughly turn the pile; subsequently, apply solid microbial agent evenly at a ratio of 0.15% of the total pile mass within a 30 cm depth area on the surface of the pile. The solid microbial agent has a viable count ≥1×10⁻⁶. 9A compound bacterial enzyme solution was prepared by mixing CFU / mL Acetobacter xylinum bacterial culture with 80 mg / mL fructose amino acid oxidase solution at a volume ratio of 2:1. Wheat bran was then mixed with this compound bacterial enzyme solution at a solid-liquid ratio of 1:0.3. The mixture was then covered with breathable non-woven fabric and allowed to age and stabilize for 25 days, during which it was turned over every 8 days.

[0025] Example 2

[0026] Preparation of porous stabilizer: 0.1 kg of steel slag powder (passed through a 200-mesh sieve) and 15.00 kg of rice husk ash were placed in a mixer and dry-mixed for 15 minutes. Then, 0.5% nano-iron oxide and 2% bentonite (by mass of the dry mixture) were added, and mixing continued for 10 minutes. Water was added while stirring, with the amount of water controlled to 12% of the total mass of the dry powder. The wet material was fed into a granulator to form raw material balls with a diameter of 3.0 cm. The raw material balls were dried at 105℃ for 4 hours, then placed in a box-type resistance furnace. The temperature was first increased to 750℃ at 3℃ / min and held for 1 hour, then increased to 950℃ at 5℃ / min and held for 1.5 hours. After cooling, the porous stabilizer was obtained.

[0027] Composting stage: Mix 80kg of straw, 20kg of kitchen waste, 20kg of livestock and poultry manure, 0.1kg of urea, and 0.1kg of nano-iron oxide. The initial C / N ratio of the mixed raw materials is 25:1, and the moisture content is 65%. Then, add a porous stabilizer at a ratio of 3.5% of the mass of the mixed raw materials, and ensure a total viable count ≥1.0×10⁻⁶. 8 The EM stock solution, diluted at a volume ratio of 1:100, was evenly sprayed onto the surface of the pile at a ratio of 0.1% of the total mass of the pile. At the same time, potassium pyrophosphate was added at a ratio of 0.5% of the mixed raw materials. The mixture was stirred at 60 rpm for 15 minutes using a mixer. The mixture was then constructed into windrows 0.5 meters long, 1.2 meters wide, and 0.5 meters high. Aeration pipes were laid at the bottom of the windrows, and the piles were covered with an airflow membrane. A 3.7 kW blower with an aeration rate of 100 L / min was used to supply oxygen for fermentation through the bottom aeration pipes.

[0028] Preparation of biomass carrier: Take straw and crush it into 1cm fragments, mix it with functional mixture at a mass ratio of 1:0.5. The functional mixture is a mixture of sodium humate, fulvic acid and wood vinegar at a mass ratio of 100:100:1, and prepare a mixture with a mass fraction of 5%. The mixture is then pretreated by heaping for 24 hours.

[0029] High-temperature control stage: When the temperature of the pile reaches 50℃, the pre-prepared biomass carriers are vertically injected into the middle and upper layers of the pile at a grid pattern with a spacing of 0.8 meters and a depth of 10 cm. The total injected mass is 1.0% of the initial mass of the pile. The surface of the pile is then slightly turned over and covered with an airflow film again. This stage lasts for 10 days.

[0030] Post-curing stage: When the pile temperature naturally drops below 40℃, add self-made biochar at a ratio of 0.5% of the total pile mass and thoroughly turn the pile; subsequently, apply solid microbial agent evenly to the surface of the pile at a ratio of 0.1% of the total pile mass. The solid microbial agent has a viable count ≥1×10⁻⁶. 9 A compound bacterial enzyme solution was prepared by mixing CFU / mL Acetobacter xylinum bacterial culture with a 50 mg / mL fructose amino acid oxidase solution at a volume ratio of 2:1. Wheat bran was then mixed with this compound bacterial enzyme solution at a solid-liquid ratio of 1:0.3. The mixture was then covered with breathable non-woven fabric and allowed to age and stabilize for 30 days, during which it was turned over every 7 days.

[0031] Example 3

[0032] Preparation of porous stabilizer: Take 0.1 kg of steel slag powder that has passed through a 200-mesh sieve and 15 kg of rice husk ash, and dry mix them in a mixer for 15 minutes. Then, add 0.5% of the total mass of the dry mixture of nano-iron oxide and 2% of the total mass of the dry mixture of bentonite, and continue mixing for 10 minutes; while stirring, add water, controlling the amount of water to be 15% of the total mass of the mixed dry powder; put the above wet material into a granulator to prepare uniform raw material balls with a diameter of 5 cm; after drying the raw material balls at 105℃ for 4 hours, place them in a box-type resistance furnace, first raise the temperature to 750℃ at 3℃ / min and hold for 1 hour; then continue to raise the temperature to 950℃ at 5℃ / min and hold for 1.5 hours to obtain the porous stabilizer.

[0033] Composting stage: Mix 60kg of straw, 30kg of kitchen waste, 10kg of livestock and poultry manure, 0.3kg of urea, and 0.05kg of nano-iron oxide. The initial C / N ratio of the mixed raw materials is 30:1, and the moisture content is 60%. Then, add a porous stabilizer at a ratio of 5.5% of the mass of the mixed raw materials, and ensure a total viable count ≥1.0×10⁻⁶. 8 The EM stock solution, diluted at a volume ratio of 1:100, was evenly sprayed onto the surface of the pile at a ratio of 0.1% of the total mass of the pile. At the same time, potassium pyrophosphate was added at a ratio of 0.2% of the mixed raw materials. The mixture was stirred at 60 rpm for 15 minutes using a mixer. The mixture was then constructed into windrows measuring 1.3 meters long, 0.5 meters wide, and 0.8 meters high. Aeration pipes were laid at the bottom of the windrows, and the piles were covered with an airflow membrane. A 3.7 kW blower with an aeration rate of 100 L / min was used to supply oxygen for fermentation through the bottom aeration pipes.

[0034] Preparation of biomass carrier: Take straw and crush it into 2cm fragments, mix it with functional mixture at a mass ratio of 1:0.5. The functional mixture is a mixture of sodium humate, fulvic acid and wood vinegar at a mass ratio of 100:100:1, and prepare a 3% mass fraction mixture. Then, pre-treat the mixture by heaping for 24 hours.

[0035] High-temperature control stage: When the temperature of the pile reaches 50°C, the pre-prepared biomass carriers are vertically injected into the middle and upper layers of the pile at a grid pattern with a spacing of 0.8 meters, with a total injection mass of 0.5% of the initial mass of the pile. The surface of the pile is then slightly turned over and covered with an airflow film again. This stage lasts for 15 days.

[0036] Post-curing stage: When the pile temperature naturally drops below 40℃, add self-made biochar at a ratio of 1.0% of the total pile mass and thoroughly turn the pile; subsequently, apply solid microbial agent evenly at a ratio of 0.2% of the total pile mass within a 50 cm depth area on the surface of the pile. The solid microbial agent has a viable count ≥1×10⁻⁶. 9 A compound bacterial enzyme solution was prepared by mixing CFU / mL Acetobacter xylinum bacterial culture with a 100 mg / mL fructose amino acid oxidase solution at a volume ratio of 2:1. Wheat bran was then mixed with this compound bacterial enzyme solution at a solid-liquid ratio of 1:0.4. The mixture was then covered with breathable non-woven fabric and allowed to age and stabilize for 20 days, during which it was turned over every 10 days.

[0037] Comparative Example 1

[0038] Composting stage: Mix 70kg of straw, 25kg of kitchen waste, 15kg of livestock and poultry manure, 0.20kg of urea, and 0.075kg of nano-iron oxide. The initial C / N ratio of the mixed raw materials was determined to be 27.5:1, and the moisture content was 62.5% (adjusted by adding 68.7kg of water). Then, a porous stabilizer was added at a ratio of 4.5% by mass of the mixed raw materials, and the total viable bacteria count was ≥1.0×10⁻⁶. 8 The EM stock solution, diluted at a volume ratio of 1:100, was sprayed evenly onto the surface of the pile at a rate of 0.1% of the total mass of the pile. 0.625 kg of potassium pyrophosphate was added, and the mixture was stirred at 60 rpm for 15 minutes using a mixer. The material was then stacked into windrows measuring 1.0 m (length) × 0.85 m (width) × 0.65 m (height), and covered with ordinary polyethylene plastic film (0.1 mm thick). The pile was manually turned every 3 days to provide oxygen.

[0039] High-temperature control stage: When the temperature of the pile reaches 50°C, the pre-prepared biomass carriers are vertically injected into the middle and upper layers of the pile at a grid pattern with a spacing of 0.8 meters and a depth of 20 cm. The total injected mass is 0.8% of the initial mass of the pile. The surface of the pile is then slightly turned over and covered with polyethylene plastic film again. This stage lasts for 12 days.

[0040] The preparation of the remaining porous stabilizers, the preparation of the biomass carriers, and the post-curing stage are the same as in Example 1.

[0041] Comparative Example 2

[0042] Composting stage: Mix 70kg of straw, 25kg of kitchen waste, 15kg of livestock and poultry manure, 0.20kg of urea, and 0.075kg of nano-iron oxide. The initial C / N ratio of the mixed raw materials was determined to be 27.5:1, and the moisture content was 62.5% (adjusted by adding 68.7kg of water). The total viable count was ≥1.0×10⁻⁶. 8 The EM stock solution, diluted at a volume ratio of 1:100, was sprayed evenly onto the surface of the pile at a rate of 0.1% of the total mass of the pile. 0.625 kg of potassium pyrophosphate was added, and the mixture was stirred at 60 rpm for 15 minutes. The material was then stacked into windrows measuring 1.0 m (length) × 0.85 m (width) × 0.65 m (height), with aeration pipes laid at the bottom and covered with an airflow membrane. A 3.7 kW blower was used to continuously supply oxygen for fermentation at a rate of 100 L / min through the bottom pipes. The preparation of the remaining biomass carriers, the high-temperature control stage, and the post-maturation stage were the same as in Example 1.

[0043] Comparative Example 3

[0044] Preparation of biomass carrier: Crush straw into 1.5cm fragments, take 1.00kg and mix with 0.50kg of functional mixture. Preparation method of functional mixture: Dissolve 200g of sodium humate and 200g of fulvic acid in deionized water to prepare a mixture with a mass fraction of 4.0%. Mix and pre-treat for 24 hours to obtain biomass carrier.

[0045] The preparation, stack-up stage, high-temperature control stage, and post-curing stage of the remaining porous stabilizers are the same as in Example 1.

[0046] Comparative Example 4

[0047] Preparation of porous stabilizer: 0.1 kg of steel slag powder (passed through a 200-mesh sieve) and 15 kg of rice husk ash were placed in a mixer and dry-mixed for 15 minutes. Then, 0.5% nano-iron oxide and 2% bentonite (by mass of the dry mixture) were added, and mixing continued for 10 minutes. Water was added while stirring, with the amount controlled to 14% of the total mass of the dry powder. The wet material was fed into a granulator to form raw material balls with a diameter of 4.0 cm. The raw material balls were dried at 105℃ for 4 hours, then placed in a box-type resistance furnace. The temperature was first increased to 750℃ at 3℃ / min and held for 1 hour, then increased to 950℃ at 5℃ / min and held for 1.5 hours. After cooling, the porous stabilizer was obtained.

[0048] Composting stage: Mix 70kg of straw, 25kg of kitchen waste, 15kg of livestock and poultry manure, 0.20kg of urea, and 0.075kg of nano-iron oxide. The initial C / N ratio of the mixed raw materials was determined to be 27.5:1, and the moisture content was 62.5% (adjusted by adding 68.7kg of water). Then, a porous stabilizer was added at a ratio of 4.5% by mass of the mixed raw materials, and the total viable bacteria count was ≥1.0×10⁻⁶. 8 An EM stock solution of CFU / mL was diluted 1:100 by volume and sprayed evenly onto the surface of the pile at a rate of 0.1% of the total mass of the pile. 0.625 kg of potassium pyrophosphate was added, and the mixture was stirred at 60 rpm for 15 minutes using a mixer. The material was then stacked into windrows measuring 1.0 m (length) × 0.85 m (width) × 0.65 m (height), with aeration pipes laid at the bottom and covered with an airflow membrane. A 3.7 kW blower was used to continuously supply oxygen for fermentation at a rate of 100 L / min through the bottom pipes.

[0049] Biochar: Tea leaves were dried to constant weight at 105℃, pulverized and passed through an 80-mesh sieve, placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 200 mL / min. The temperature was increased to 500℃ at a set program of 10℃ / min, and pyrolyzed and carbonized at this temperature for 2 hours to obtain biochar.

[0050] High-temperature control stage: When the temperature of the pile reaches 50°C, the above-mentioned biochar is vertically injected into the middle and upper layers of the pile at a grid pattern with a spacing of 0.8 meters and a depth of 20 cm. The total injected mass is 0.8% of the initial mass of the pile. The surface of the pile is then slightly turned over and covered with a thin airflow film again. This stage lasts for 12 days.

[0051] Post-curing stage: When the pile temperature naturally drops below 40℃, add self-made biochar at a ratio of 0.8% of the total pile mass and thoroughly turn the pile; subsequently, apply solid microbial agent evenly at a ratio of 0.15% of the total pile mass within a 30 cm depth area on the surface of the pile. The solid microbial agent has a viable count ≥1×10⁻⁶. 9A compound bacterial enzyme solution was prepared by mixing CFU / mL Acetobacter xylinum bacterial culture with 80 mg / mL fructose amino acid oxidase solution at a volume ratio of 2:1. Wheat bran was then mixed with this compound bacterial enzyme solution at a solid-liquid ratio of 1:0.3. The mixture was then covered with breathable non-woven fabric and allowed to age and stabilize for 25 days, during which it was turned over every 8 days.

[0052] Comparative Example 5

[0053] Post-aging stage: When the temperature of the pile naturally drops below 40℃, self-made biochar is added at a ratio of 0.8% of the total mass of the pile and the pile is turned over completely; then, it is covered with breathable non-woven fabric and enters a 25-day aging and stabilization period, during which the pile is turned over once every 8 days.

[0054] Comparative Example 6

[0055] The difference between this comparative example and Example 1 is that in this comparative example, Acetobacter xylinum bacterial solution is used instead of Bacillus subtilis bacterial solution; otherwise, it is the same as Example 1.

[0056] Comparative Example 7

[0057] The difference between this comparative example and Example 1 is that the fructose amino acid oxidase solution is replaced with a neutral protease solution in this comparative example; otherwise, it is the same as in Example 1.

[0058] Experiment 1: Effect Test

[0059] (1) Compost sample collection: Five samples were randomly collected from different locations and heights in the compost, and the samples were mixed evenly. Each group of samples was divided into 3 portions, two of which were stored in refrigerators at 4℃ and -80℃ respectively, and the other portion was air-dried and crushed for later use.

[0060] (2) Determination of EC: Take fresh sample and deionized water at a ratio of 1:10 (W / V), place on a horizontal shaker and shake for 2 hours, let stand for 30 minutes and then measure with a pH meter and conductivity meter. Each sample is repeated 5 times.

[0061] (3) Total nitrogen retention rate: Referring to the "Determination of Total Nitrogen Content in Fertilizers - Distillation Titration Method" (GB / T3595), the Kjeldahl method was used to determine the total nitrogen mass of the initial raw materials and the total nitrogen mass of the finished compost. The total nitrogen retention rate was calculated as: (Total nitrogen mass of finished compost / Total nitrogen mass of initial raw materials) × 100%

[0062] (4) Determination of ammonium nitrogen and nitrate nitrogen content: Fresh samples were thoroughly mixed with deionized water at a ratio of 1:10 (W / V), and then placed in a shaker at 30℃ and 170 rpm for 24 h. After shaking, the samples were centrifuged at 4℃ and 12000 r / min for 10 min, and the supernatant was collected and filtered through a 0.45 μm aqueous filter membrane. The ammonium nitrogen and nitrate nitrogen content of the filtrate were determined using a continuous flow analyzer. Each sample was tested in five replicates.

[0063] (5) Germination index determination: Fresh samples were mixed with deionized water at a ratio of 1:10 (w / v), shaken on a horizontal shaker for 2 hours, and then filtered. 5 ml of the filtrate was added to a petri dish lined with filter paper, with 20 *Ligustrum lucidum* seeds placed in each dish. Deionized water was used as the blank control. The petri dishes were incubated at 25℃ for 2-3 days. Seed root length was measured, and the germination index was calculated using the formula. Five replicates were performed for each sample. Germination index = Sample germination rate (%) × Sample root length × 100% / Control germination rate (%) / Control root length

[0064] The results are shown in Table 1 below:

[0065] Table 1

[0066] Group EC (mS / cm) Total nitrogen retention rate / % <![CDATA[NH4⁺-N(mg / kg)]]> <![CDATA[NO3⁻-N(mg / kg)]]> Germination Index (GI) (%) Example 1 3.1 78.5 170 650 98.2 Example 2 3.2 76.1 185 610 96.5 Example 3 2.9 75.3 182 580 95.1 Comparative Example 1 3.1 70.4 206 550 91.4 Comparative Example 2 3.6 60.2 297 420 84.3 Comparative Example 3 3.5 65.8 240 480 90.8 Comparative Example 4 3.3 68.9 210 530 92.1 Comparative Example 5 3.2 47.2 335 350 80.5 Comparative Example 6 3.3 58.6 280 410 85.9 Comparative Example 7 3.2 52.5 308 380 83.5

[0067] As shown in Table 1, the total nitrogen retention rates of Examples 1-3 were significantly higher than those of all comparative examples, with lower ammonium nitrogen content and higher nitrate nitrogen content. Furthermore, the germination index (GI) was close to or exceeded 95%, indicating that the embodiments of the present invention efficiently retained nitrogen while achieving the conversion of nitrogen into a stable, plant-available form, and ensuring low salinity and high biocompatibility of the compost product. Comparative Example 1 retained the porous stabilizer but used a regular plastic film instead of the airflow membrane; the total nitrogen retention rate was still maintained at 70.4%, significantly higher than that of Comparative Example 2. This fully demonstrates that the porous stabilizer is the core material for improving the microenvironment of the compost pile. Comparative Example 2 did not add a porous stabilizer during the pile-up stage. Although airflow membrane covering and bottom aeration were still used, the total nitrogen retention rate plummeted to 60.2%, with nitrate nitrogen at only 420 mg / kg and ammonium nitrogen accumulation as high as 297 mg / kg. This was because the lack of a porous stabilizer physically optimized the pore structure of the pile, resulting in poor material permeability, the emergence of local anaerobic zones, and the obstruction of aerobic nitrification. Inorganic nitrogen mainly existed in the form of ammonium nitrogen and was easily volatilized and lost. Comparative Example 3 did not add wood vinegar to the biomass carrier, which weakened the ability to regulate local pH and inhibit ammonia volatilization during the high-temperature period. Comparative Example 4 used ordinary biochar without iron oxide loading, which had a weak adsorption and fixation effect on nitrogen. Comparative Example 5 did not add solid inoculants, and the lack of microbial assimilation and fixation of nitrogen led to a significant decrease in nitrogen retention rate. Comparative Examples 6 and 7 replaced functional bacteria and enzymes, respectively, and their synergistic nitrogen fixation and conversion effects were not as good as the combination of Acetobacter xylinum and fructose amino acid oxidase specific to this invention. In summary, this invention achieves the minimization of nitrogen loss and the maximization of the agricultural value of the product through the synergistic intervention of optimizing the physical structure of the compost pile with porous stabilizers, chemical fixation with functionalized biomass carriers, adsorption and protection by iron oxide biochar, and synergistic biotransformation by specific bacterial enzymes.

Claims

1. The application of a novel composite material in reducing nitrogen loss in composting, comprising a composting stage, a high-temperature control stage, and a post-maturation stage, characterized in that... The composting stage comprises: mixing 60-80 parts of straw, 20-30 parts of kitchen garbage, 10-20 parts of livestock and poultry manure, 0.1-0.3 parts of urea and 0.05-0.1 parts of nano iron oxide, the initial C / N ratio of the mixed raw materials is 25:1 to 30:1, and the water content is 60% to 65%; then, a porous stabilizer is added in a proportion of 3.5-5.5% of the mass of the mixed raw materials, an EM bacteria stock solution with a total number of viable bacteria ≥1.0×10 8 CFU / mL is diluted at a volume ratio of 1:100 and uniformly sprayed on the surface of the pile in a proportion of 0.1% of the total mass of the pile, and potassium pyrophosphate is added in a proportion of 0.2-0.5% of the mass of the mixed raw materials, a mixer is used to stir at a speed of 60 rpm for 15 minutes; then the mixed material is built into a strip pile with a length of 0.5-1.3 meters, a width of 0.5-1.2 meters and a height of 0.5-0.8 meters, the bottom of the strip pile is paved with an aeration pipeline, the pile body is covered with an airflow film, and a fan with a power of 3.7kW and an aeration amount of 100L / min is used to supply oxygen fermentation through the bottom aeration pipeline.

2. The application of the novel composite material as described in claim 1 in reducing nitrogen loss during composting, characterized in that: The porous stabilizer comprises: dry mixing steel slag powder and rice husk ash (passed through a 200-mesh sieve) in a mixer at a mass ratio of 1:150 for 15 minutes; then adding 0.5% nano-iron oxide and 2% bentonite (by mass of the dry mixture) and mixing for another 10 minutes; adding water while stirring, with the amount of water controlled to be 12-15% of the total mass of the mixed dry powder; feeding the above wet material into a granulator to prepare uniform raw material balls with a diameter of 3-5 cm; drying the raw material balls at 105°C for 4 hours, then placing them in a box-type resistance furnace, first heating to 750°C at 3°C / min and holding for 1 hour; then continuing to heat to 950°C at 5°C / min and holding for 1.5 hours to obtain the porous stabilizer.

3. The application of the novel composite material as described in claim 1 in reducing nitrogen loss during composting, characterized in that: The high-temperature control stage includes: when the temperature of the pile reaches 50°C, the pre-prepared biomass carriers are vertically injected into the middle and upper layers of the pile at a grid pattern with a spacing of 0.8 meters, with a depth not exceeding 30 cm. The total injected mass is 0.5-1.0% of the initial mass of the pile. The surface of the pile is then slightly turned over and covered with a thin airflow film again. This stage lasts for 10-15 days.

4. The application of the novel composite material as described in claim 3 in reducing nitrogen loss during composting, characterized in that: The preparation of the biomass carrier includes: taking straw, crushing it into 1-2cm fragments, mixing it with a functional mixture at a mass ratio of 1:0.5, and pre-treating it by heaping for 24 hours.

5. The application of the novel composite material as described in claim 4 in reducing nitrogen loss during composting, characterized in that: The functional mixture is a mixture of sodium humate, fulvic acid and wood vinegar in a mass ratio of 100:100:1, with a mass fraction of 3-5%.

6. The application of the novel composite material as described in claim 1 in reducing nitrogen loss during composting, characterized in that: The post-maturation stage includes: when the temperature of the pile naturally drops below 40°C, adding self-made biochar at a ratio of 0.5-1.0% of the total mass of the pile and turning the pile over completely; then, uniformly applying solid microbial agent at a ratio of 0.1-0.2% of the total mass of the pile in the 0-50 cm depth area on the surface of the pile, and covering it with breathable non-woven fabric, entering a 20-30 day aging and stabilization period, during which the pile is turned over every 7-10 days.

7. The application of the novel composite material as described in claim 6 in reducing nitrogen loss during composting, characterized in that: The self-made biochar comprises: drying tea leaves at 105℃ to constant weight, pulverizing them and passing them through an 80-mesh sieve, and mixing them with hematite powder at a mass ratio of 10:1 in a mixer for 30 minutes until homogeneous; placing the mixture in a tube furnace, introducing nitrogen gas at a flow rate of 200 mL / min, and heating it to 500℃ at a set program of 10℃ / min, and pyrolyzing and carbonizing it at this temperature for 2 hours; after pyrolysis, cooling it to room temperature under continuous nitrogen protection to obtain the primary biochar product; subsequently, placing this primary product and goethite at a mass ratio of 1:1 in a ball mill, and ball milling it at a speed of 300 rpm for 4 hours, pausing and reversing the rotation for 10 minutes every 30 minutes to ensure uniform mixing, and finally obtaining the self-made biochar.

8. The application of the novel composite material as described in claim 6 in reducing nitrogen loss during composting, characterized in that: The preparation of the solid microbial agent includes: preparing a live bacteria count ≥1×10⁻⁶. 9 A compound bacterial enzyme solution is prepared by mixing CFU / mL Acetobacter xylinum bacterial solution with a fructose amino acid oxidase solution at a concentration of 50-100 mg / mL at a volume ratio of 2:

1. Then, wheat bran is mixed with the compound bacterial enzyme solution at a solid-liquid ratio of 1:0.3-0.4.