Catechol-manganese dioxide synergistic directional humification pig manure aerobic composting nitrogen conservation method

Abstract

The invention discloses a catechol-manganese dioxide synergistic directional humification pig manure aerobic composting nitrogen conservation method. Sawdust, straws or rice hulls are used as a carbon-rich bulking agent, and a modified carrier which is mildly oxidized and anchored with gamma-MnO2 is preferably selected; catechol is added in the mixing stage, and the active MnO2 is added in a segmented manner in the initial stage of composting; in an initial reaction window from weak acid to neutrality and moderate ventilation, oxidative condensation of catechol and nitrogen-containing organic matters is promoted, and then curing is carried out until a maturation criterion is reached; according to the method, ammonification and dissipation are inhibited from the source, the fixation and humification degree of nitrogen in an organic combination state is improved, peculiar smell is reduced, the stability and uniformity of a finished product are improved, and the method is suitable for resourceful treatment of livestock and poultry manure.

Description

Technical Field

[0001] This invention relates to the technical field of composting, and in particular to a method for nitrogen retention in aerobic composting of pig manure through synergistic and directional humification of catechol and manganese dioxide. Background Technology

[0002] Aerobic composting of livestock and poultry manure, as a key technology for the resource utilization of agricultural solid waste, has attracted increasing attention due to the nitrogen loss and odor emissions that commonly occur during the composting process, especially during the heating and high-temperature periods. In-depth research reveals that the underlying mechanisms of this problem are mainly reflected in the following aspects: First, under high-temperature conditions, proteins and amino acids undergo rapid ammonification reactions, directly leading to the volatile loss of ammonia. Second, during the nitrification and denitrification processes involving microorganisms, nitrogen is lost through various gaseous forms (such as N2O and NO). Third, the water-soluble organic matter produced in the initial stage of composting is mostly composed of smaller molecular weight components. These substances are difficult to transform into more stable macromolecular humic precursors through complex biochemical processes in a short time, thus preventing nitrogen from being effectively fixed in a non-volatile and non-migrating chemically bound structure.

[0003] To address the aforementioned nitrogen loss problem, current industry solutions primarily focus on the mid-to-late stages of composting. Specific measures include: reducing ammonia volatility through acidification; improving ammonium nitrogen fixation efficiency by utilizing adsorbent materials (such as porous minerals like biochar and zeolite) or by forming mineralization products (such as adding magnesium salts-phosphates to form insoluble magnesium ammonium phosphate precipitates); or inhibiting ammonification reactions by precisely controlling key operating parameters such as aeration rate, moisture content, and pH. However, these traditional methods have several limitations: their mechanisms of action mostly involve passive interception after nitrogen has been converted into volatile or migratory forms. This approach not only has extremely strict requirements on the operating time window but also easily inhibits microbial activity. Furthermore, it exhibits strong sensitivity to raw material characteristics and batch variations. More importantly, these methods contribute little to improving the humification level of the final product.

[0004] In recent years, while research on using redox media to promote humification has made some progress, existing studies have mostly focused on broad-spectrum oxidation or pollutant degradation, with insufficient research specifically targeting the initial stages of composting, particularly under weakly acidic to neutral environments. Against this backdrop, how to guide nitrogen into a stable, non-volatile, and non-decomposable bound state transformation pathway through technological means in the early stages of composting, while effectively controlling odor emissions and ensuring the stable quality of the final product, has become a critical issue that urgently needs to be addressed. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned problems existing in the prior art and to provide a method for nitrogen retention in aerobic composting of pig manure through synergistic and directional humification of catechol-manganese dioxide.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for nitrogen retention in aerobic composting of pig manure through synergistic and directional humification of catechol and manganese dioxide, comprising the following steps: S1 Raw material preparation: Pig manure is mixed with a carbon-rich loosening agent, which is selected from one or more of sawdust, straw or rice husks. The moisture content is adjusted to 60-65%, and the mixture is mixed with water at a mass ratio of 1:10 to form a suspension. The initial pH is measured to be 6.6-7.2. S2 polyphenol precursor addition: Add 0.1-0.3 wt% catechins based on the dry basis of the material, add it all at once during the mixing stage and mix well; S3 Manganese dioxide addition in stages: Add 0.05-0.2 wt% of active manganese dioxide powder based on the dry basis of the material, and add 50-60% and 40-50% of the total amount of manganese dioxide in two time periods: 0-24h and 24-72h, respectively. S4 initial reaction window: 0–72 h using continuous aeration or intermittent aeration with a duty cycle ≥50%, with a ventilation rate of 0.15–0.25 L·min. -1 ·kg -1 (Based on volatile solids), and the pH of the pile is maintained at 6.6–7.2 by an acid conditioner; S5 Subsequent Maturation: After the initial window is completed, continue aerobic composting until at least two of the following conditions are met: germination index GI ≥ 80%, stable compost temperature ≤ 40℃ for 48 hours, or finished product C / N ≤ 20.

[0007] This invention introduces a synergistic and directional humification reaction between catechins and active manganese dioxide within the initial 0-72 hours of composting, enabling the rapid conversion of nitrogen from small molecules to large molecules during pig manure composting, thereby achieving the effect of inhibiting ammonification and ammonia volatilization from the source.

[0008] Catechols, under the mild oxidation of manganese dioxide, form reactive semiquinone structures that can condense with protein and amino acid side chains to form nitrogen-containing aromatic polymers. This allows nitrogen to be fixed in a relatively stable covalent form within the organic matrix, significantly reducing the formation of ammonium nitrogen and the emission of volatile ammonia. Simultaneously, the redox properties of manganese dioxide promote aromatization and condensation reactions, significantly enhancing the aromaticity and molecular weight of water-soluble organic matter in the pile, ultimately generating more humic acid precursors. This is achieved by controlling the initial pH at 6.6–7.2 and the ventilation rate at 0.15–0.25 L / min. -1 ·kg -1(Based on volatile solids) This creates an environment where oxidative condensation reactions are dominant and mineralization reactions are suppressed, making the carbon and nitrogen conversion within the pile body more concentrated on the humification pathway, and significantly improving nitrogen retention.

[0009] Compared to traditional methods that fix ammonium nitrogen through adsorption or acidification in the later stages of composting, this invention regulates the reaction window before the high-temperature stage, enabling the directional humification process to complete earlier and inhibiting ammonification and ammonia emission at the source. This synergistic system converts protein and amino acid nitrogen into more stable organically bound nitrogen in the early stages of composting, effectively preserving nitrogen throughout the entire process. Through the combined action of catechols and manganese dioxide, a reaction pathway dominated by aromatization condensation is formed within the compost pile, promoting the accumulation of humic precursors, resulting in a more complete humification process and a more stable structure. The resulting compost exhibits higher stability and maturity, characterized by a denser organic molecular structure, increased aromatization, significantly reduced odor, uniform overall quality, and good environmental friendliness, achieving a synergistic effect of nutrient retention, odor reduction, and improved compost quality.

[0010] As a further improvement of the present invention, the acid regulator is one of phosphoric acid, citric acid, or a mixture thereof.

[0011] Acid regulators such as phosphoric acid, citric acid, or mixtures thereof can maintain a slightly acidic-neutral environment in the compost pile during the initial stage of composting, preventing ammonia volatilization caused by alkalization. Phosphoric acid has good buffering properties and nutrient compatibility, while citric acid has complexing and mild reducing properties. When used alone or in combination, they can inhibit NH3 generation without suppressing microbial activity, promote the smooth progress of the oxidative condensation reaction between catechols and MnO2, thereby improving nitrogen fixation efficiency and reducing odor emissions.

[0012] As a further improvement of the present invention, the dry weight of the carbon-rich loosening agent accounts for 10-40% of the total dry weight of pig manure and the carbon-rich loosening agent, and the particle size of the carbon-rich loosening agent is 5-30 mm.

[0013] The dry weight of the carbon-rich loosening agent accounts for 10-40% of the total dry weight of pig manure and the loosening agent, with a particle size controlled between 5-30 mm. This balances the aeration, moisture content, and heat conduction of the compost pile. This ratio ensures moderate porosity and maintains a C / N ratio between 25-35, guaranteeing microbial activity and heating rate while preventing excessive aeration that could lead to nitrogen loss. It also provides a stable physical environment for MnO2-promoted condensation and humification, ultimately improving compost uniformity and nitrogen retention.

[0014] As a further improvement of the present invention, the carbon-rich loosening agent is first subjected to a pre-activation treatment, which includes the following steps: One or more of sawdust, straw, or rice husks are oxidized at 40–60°C with a 0.5–2.0 wt% hydrogen peroxide aqueous solution for 30–120 min. After washing and drying, the total phenol content on the surface, calculated as catechol equivalent, is ≥0.50 mmol·g. -1 Then, γ-MnO2 is anchored on the fiber pore wall by in-situ impregnation deposition, with a loading of 0.10 to 0.50 wt%.

[0015] After undergoing mild oxidation and γ-MnO2 site-fixation deposition treatment, the carbon-rich porosilicate agent develops more active hydroxyl groups and quinone functional groups on its surface, and immobilizes trace amounts of manganese oxide sites, giving the material slight catalytic and adsorption functions. This modification transforms the porosilicate agent from a simple support filler into a reaction carrier capable of participating in humification reactions.

[0016] In the early stages of composting, it can more effectively adsorb catechols and their reaction intermediates, and continuously provide a mild oxidizing effect on the surface, promoting the rapid condensation of these small molecules into more stable nitrogen-containing aromatic compounds. This not only accelerates the formation of humic precursors but also reduces ammonification and ammonia volatilization, thereby significantly improving nitrogen fixation efficiency and humification depth, resulting in higher nitrogen retention, milder odor, and better stability in the final compost.

[0017] As a further improvement of the present invention, the active manganese dioxide d 50 The wavelength range is 50–200 nm.

[0018] Defined particle size distribution d 50 A particle size of 50–200 nm ensures uniform dispersion of active manganese dioxide in the liquid film of the pile, forming a reaction interface that matches the organic matter. Particles smaller than 50 nm have excessively high surface energy, making them prone to aggregation or deactivation due to encapsulation by organic colloids; particles larger than 200 nm exhibit a sharp decrease in specific surface area, reducing electron transfer and oxidative condensation rates. Particles within the 50–200 nm range can fully penetrate the pile pores, forming a multiphase composite reaction layer with catechols and organic nitrogen in the microenvironment, promoting uniform humification.

[0019] As a further improvement of the present invention, the BET relative specific surface area of ​​the active manganese dioxide is 80-150 m². 2 ·g -1 .

[0020] The limitation on specific surface area ensures that activated manganese dioxide possesses a sufficient reaction interface while avoiding agglomeration and deactivation due to excessively high surface energy. Specific surface area below 80 m² / g is considered optimal. 2 ·g -1 At this time, the surface reaction sites per unit mass are insufficient, the electron acceptor density decreases, the oxidation rate of catechols slows down, and the humification reaction is delayed; the specific surface area is higher than 150m². 2 ·g-1 When the surface energy of the particles is too large, they tend to agglomerate and form inert blocky structures, leading to a decrease in catalytic activity. The specific surface area should be controlled between 80 and 150 m². 2 ·g -1 Within a certain range, the nanorods maintain good dispersion and surface accessibility in the stack, ensuring the continuous stability of the reaction process.

[0021] As a further improvement of the present invention, the area ratio of oxygen vacancy peak in the O1s fraction of the active manganese dioxide measured by XPS is 20-30%.

[0022] The oxygen vacancy peak area ratio is limited to 20-30% to ensure that MnO2 has an appropriate surface oxygen defect density. Oxygen vacancies are key channels for electron migration and adsorption reactions on the MnO2 surface, and their density directly determines the material's electron accepting capacity and free radical generation rate. When the oxygen vacancy ratio is below 20%, the electron transfer efficiency is insufficient, and catechols are difficult to be effectively oxidized to form semiquinone intermediates, resulting in insufficient kinetics for the condensation reaction; when the oxygen vacancy ratio exceeds 30%, the surface is easily over-reduced to Mn. 3 ⁺In the enriched state, oxidation activity decreases and the structure becomes unstable. Limiting this range can achieve a balance between oxidation and stability, allowing manganese dioxide to rapidly capture electrons and promote condensation in the early stages of composting, while also being less prone to excessive reduction and deactivation.

[0023] As a further improvement of the present invention, the active manganese dioxide Mn 3+ / Mn 4+ The atomic ratio is 0.35 to 0.70.

[0024] Furthermore, limiting Mn 3+ / Mn 4+ An atomic ratio of 0.35–0.70 is used to match the electron transfer rate and reaction selectivity required for the catechol oxidation reaction. Mn 3+ / Mn 4+ When the ratio is below 0.35, the material is mainly composed of Mn. 4+ Primarily, its oxidizing properties are too strong, easily leading to the complete mineralization of catechols and amino acids, releasing large amounts of NH4. + This leads to nitrogen loss; Mn 3+ / Mn 4+ When the ratio is higher than 0.70, the oxidizing capacity is insufficient, making it difficult to form semiquinone intermediates, and the humification reaction rate decreases. Maintaining a ratio of 0.35–0.70 allows the MnO3 surface to be under mild oxidizing conditions, promoting the directional condensation of catechols with nitrogen-containing organic matter to form nitrogen-containing aromatic polymers rather than simple oxidation products.

[0025] As a further improvement of the present invention, the active manganese dioxide is a Bi-Co-Cu ternary doped material with a total doping amount of 0.2 to 1.5 at.%.

[0026] By controlling the morphology and oxygen vacancy density, the electronic structure and reaction pathway of MnO2 can be further optimized by adjusting the proportion of heterovalent ions introduced into the lattice, thereby generating higher electron transfer efficiency and reaction selectivity in the catechol-MnO2 synergistic system.

[0027] First, ternary doping introduces Bi 3+ Co 2+ and Cu 2+ Heterovalent ions replace part of the Mn in the MnO2 lattice. 4+ This allows for the compensation of local charge imbalances and induces more stable oxygen vacancies. 3+ A larger radius can expand the lattice spacing and lower the electron migration barrier; Co 2+ and Cu 2+ Exhibiting reversible multivalent states, it can act as a reversible electron mediator in the oxidation of catechols, thereby improving the electron transfer rate and surface redox activity of MnO2. Through the synergistic effect of these three ions, a higher density of oxygen vacancy-metal hybrid energy levels is formed, enabling MnO2 to have both strong electron acceptance capacity and mild oxidation characteristics in the early stage of composting.

[0028] Secondly, controlling the doping concentration within the range of 0.2–1.5 at.% balances lattice stability and enhanced activity. When the doping concentration is below 0.2 at.%, the dopant ion distribution is sparse, resulting in insufficient regulation of the electronic structure of MnO2 and failing to significantly improve oxygen vacancy density and conductivity. When the doping concentration is above 1.5 at.%, severe lattice distortion occurs, easily leading to the formation of independent oxide phases of Bi, Co, or Cu, reducing overall structural stability and causing non-uniform distribution of active sites. Limiting the concentration to the range of 0.2–1.5 at.% ensures that the dopant ions are uniformly distributed in the near-surface region, stably forming a Mn-OM (metallic) bridging structure, thus achieving a balance between enhanced activity and structural stability.

[0029] Furthermore, the synergistic effect of this doping system with the aforementioned morphology and electronic parameter constraints makes the electron channels in the catechol oxidation-condensation process smoother. The Fermi level of Bi-Co-Cu co-doped MnO2 shifts upward, increasing the electron density. Under weakly acidic and neutral conditions (pH 6.6–7.2), it can rapidly capture electrons provided by catechol without excessive oxidation, thereby promoting the generation and stable existence of semiquinone radicals and providing a sustained electron transfer drive for the condensation of nitrogen-containing small molecules.

[0030] In the initial stage of aerobic composting of pig manure, the use of this ternary doped MnO2 resulted in earlier and more complete humification reactions in the compost pile. The increased electron migration channels on the material surface allowed for the continuous capture and condensation of reactive intermediates generated from catechol oxidation with organic nitrogen substances, forming stable nitrogen-containing aromatic polymers. Consequently, the oxidation-condensation rate in the initial stage of composting was significantly accelerated, the volatilization trend of ammonia nitrogen was significantly suppressed, and the overall compost pile exhibited a more uniform humification process. The resulting compost had a higher proportion of humic components, a denser structure, stronger aroma, and nitrogen existed in a stable bound state.

[0031] The present invention, by adopting the above technical solution, has the following beneficial effects: 1. In the early stages, a combination of a weakly acidic neutral environment (pH 6.0-7.0) and moderate ventilation (0.05-0.15 L / min·kg) was used to promote the oxidation condensation reaction, stabilize nitrogen, and inhibit the production of nitrogen-containing odor substances; 2. Precisely control the morphology, surface defect density, and manganese valence state distribution of manganese dioxide catalyst, confining it to a mild single-electron transfer reaction range, thereby improving the selectivity of condensation reaction and humification efficiency. 3. Adopt a staged addition strategy, adding reagents in 2-3 stages according to the reaction process, matching the initial operating parameters, reducing the risk of reaction system imbalance, and making the composting process more stable and replicable; 4. Use a carbon-rich loosening agent that has been mildly oxidized and has a small number of manganese oxide active sites fixed to transform it into a catalytic reaction carrier, promote the early accumulation of humic precursor substances, and lay the foundation for subsequent humification. Detailed Implementation

[0032] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0033] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0034] 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.

[0035] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0036] The present invention will now be described in detail with reference to specific embodiments, which are intended to understand rather than limit the invention.

[0037] Example 1 This embodiment provides a method for nitrogen retention in aerobic composting of pig manure through synergistic and targeted humification of catechol and manganese dioxide. The specific steps are as follows: S1 Raw Material Preparation: Fresh pig manure (collected on the same day, unfermented) was selected, with an initial moisture content of 75-78 wt%, and the actual value in this example was 77 wt%; the total solids (TS) was 23 wt%, and the volatile solids (VS) accounted for 80% of the total solids.

[0038] The carbon-rich loosening agent is a mixture of sawdust and straw (mass ratio 1:1) with a particle size range of 15 mm.

[0039] The carbon-rich loosening agent undergoes the following pretreatment: A mixture of sawdust and straw (1:1) was oxidized at 40°C with 1wt% H2O2 for 60 min. After washing and drying, the total phenol content on the surface was 0.52 mmol·g. -1 Then, γ-MnO2 was anchored onto the borehole wall using an impregnation method, with a loading of 0.2 wt%.

[0040] The active γ-MnO2 powder used in this embodiment was purchased from Nanjing Chunqiu Nanotechnology Co., Ltd., model CQ-γMnO2-N120. The specific surface area of ​​this powder is approximately 120 m². 2 ·g -1 The oxygen vacancy peak area accounts for approximately 25% of the O1s fraction, and Mn 3 + / Mn 4+ Atomic ratio approximately 0.50, volume distribution d 50 Approximately 120nm.

[0041] Pig manure was mixed with a pretreated carbon-rich loosening agent on a dry basis, with the loosening agent accounting for 25% of the dry weight of the mixture. The C / N ratio of the mixture was determined by elemental analysis, with a total carbon content of 43.5 wt% and a total nitrogen content of 1.50 wt%, resulting in a calculated C / N ratio of 29. Water was added to adjust the moisture content to 60-65%, with an actual value of 62 wt% in this embodiment. A suspension was prepared by mixing the mixture with water at a ratio of 1:10, and the initial pH was measured to be 6.8.

[0042] After being manually stirred for 5 minutes, the mixture is piled into an insulated composting device equipped with a temperature control and ventilation system. The pile dimensions are 0.5m × 0.5m × 0.4m, with an air distribution plate at the bottom. The container is equipped with temperature, pH, dissolved oxygen, and exhaust gas sampling ports.

[0043] S2 polyphenol precursor addition: Add 0.2 wt% catechins based on the dry basis of the material. Dissolve catechins (analytical grade, purity ≥99%) in deionized water to prepare a 10 wt% solution, spray it evenly in one go during the mixing stage, and mechanically stir for 10 min.

[0044] S3 manganese dioxide is added in stages: The activated manganese dioxide uses the same activated γ-MnO2 powder as in step S1, with a specific surface area of ​​approximately 120 m². 2 ·g -1 The oxygen vacancy peak area accounts for approximately 25% of the O1s fraction, and Mn 3+ / Mn 4+ Atomic ratio approximately 0.50, volume distribution d 50 Approximately 120nm.

[0045] Add 0.1 wt% based on the dry basis of the material.

[0046] First application (0-24 hours): 60% of the total dosage; Second time (24-72 hours): 40% of the total dosage.

[0047] Each time, a small amount of deionized water (0.2wt% of the wet weight of the pile) is added to make slurry and sprayed, and the pile is manually turned over for 5 minutes.

[0048] S4 Initial Reaction Window Control: Intermittent aeration was used from 0 to 72 hours, with a single cycle of 20 minutes and a duty cycle of 70%. The ventilation volume was controlled at 0.2 L / min. -1 ·kg -1 .

[0049] A mixed acid solution of phosphoric acid and citric acid (mass ratio 1:1) (concentration 2wt%) was used as an acidity regulator to maintain the pH at 6.8±0.1.

[0050] During the reaction, the pile temperature rose to 55°C within 24 hours and stabilized at around 60°C after 72 hours. The pile was turned over every 12 hours.

[0051] S5 further maturation: After 72 hours, the curing stage begins, and the ventilation rate is adjusted to 0.10 L / min. -1 ·kg -1 The moisture content was maintained at 58±1wt%. The pile was turned over every 48 hours and matured for 21 days. The germination index (GI) was measured to be 85%, the pile temperature was stable at 38±1℃ for 48 hours, and the C / N ratio was measured to be 18.

[0052] Example 2 The difference between this embodiment and Embodiment 1 is that the amount of catechin added in step S2 is 0.5% of the dry basis of the material.

[0053] Example 3 The difference between this embodiment and embodiment 1 is that in step S2, the amount of catechin added is 0.3% of the dry basis of the material, and the amount of active manganese dioxide added is 0.15% of the dry basis of the material, and the two additions are each 50% of the total amount.

[0054] Example 4 The difference between this embodiment and Embodiment 1 is that the carbon-rich loosening agent was not pretreated.

[0055] Example 5 The difference between this embodiment and Example 1 is that the activated manganese dioxide used is Bi-Co-Cu ternary co-doped γ-MnO2 powder purchased from Nanjing Chunqiu Nanotechnology Co., Ltd., model number CQ-γMnO2-BCu-05. The total doping amount is 0.5 at.%, with the molar ratio of Bi, Co, and Cu is 1:1:1. The average particle size of this powder is approximately 120 nm, and the specific surface area, measured by BET, is approximately 125 m². 2 ·g -1 The oxygen vacancy peak area accounts for approximately 27%, Mn 3+ / Mn 4+ The atomic ratio is approximately 0.55.

[0056] Comparative Example 1 The difference between this comparative example and Example 1 is that no catechins were added.

[0057] Comparative Example 2 The difference between this comparative example and Example 1 is that the carbon-rich loosening agent was not pretreated and no manganese dioxide was added.

[0058] Performance testing 1. Nitrogen fixation efficiency test: First, the total nitrogen (TN) of the sample on a dry basis was determined using the Kjeldahl method. Then, 0.01 mol·L⁻¹ nitrogen was used. -1 Inorganic nitrogen was extracted from the sample using KCl solution, and NH4 was determined separately. + -N and NO3 - -N (colorimetric or ion chromatography).

[0059] To obtain the distribution of organically bound nitrogen, the sample was fractionated by alkali dissolution and acid precipitation to separate humic acid (HA) and fulvic acid (FA) fractions, and the Kjeldahl method was used to determine HA-N and FA-N respectively. The remaining solid residue was then subjected to acid hydrolysis to determine the insoluble organic nitrogen (RN).

[0060] In the calculation, the fixed nitrogen is calculated as HA-N+FA-N+RN, and then the nitrogen fixation efficiency (%) is calculated as fixed nitrogen / TN×100.

[0061] 2. Nitrogen retention rate detection: The total nitrogen content (TN) of the finished product on a dry basis was measured respectively. 成品 With the dry basis mass of the finished product m 成品干基 Simultaneously record the initial dry basis total nitrogen content (TN). 初始 With initial dry basis mass m 初始干基 Based on this, the nitrogen retention rate (%) is calculated as follows: (TN) 成品 ×m 成品干基 )÷(TN 初始 ×m 初始干基 )×100.

[0062] 3. Odor reduction assessment and testing: Ammonia (NH3) was absorbed using a double-tower acid absorption method, with 3% boric acid as the absorbent. The absorbent was replaced every 12 hours, and the nitrogen content was calculated by titration with sulfuric acid, which was then converted into the cumulative emission per unit of volatile solids (mgN·kg). -1 VS).

[0063] Table 1 Group Nitrogen fixation efficiency (%) Nitrogen retention rate (%) <![CDATA[NH3 cumulative emissions (mgN·kg -1 VS)]]> Example 1 73 86.5 1682 Example 2 64 80 2053 Example 3 75.6 85.8 1586 Example 4 67.2 82.5 1861 Example 5 79.8 88.8 1427 Comparative Example 1 53.2 72.3 2683 Comparative Example 2 48.1 68.5 3482 The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for nitrogen retention in aerobic composting of pig manure through synergistic and targeted humification of catechol and manganese dioxide, characterized in that, Includes the following steps: S1 Raw material preparation: Pig manure is mixed with a carbon-rich loosening agent, which is selected from one or more of sawdust, straw or rice husks. The moisture content is adjusted to 60-65%, and the mixture is mixed with water at a mass ratio of 1:10 to form a suspension. The initial pH is measured to be 6.6-7.

2. S2 polyphenol precursor addition: Add 0.1-0.3 wt% catechins based on the dry basis of the material, add it all at once during the mixing stage and mix well; S3 Manganese dioxide addition in stages: Add 0.05-0.2 wt% of active manganese dioxide powder based on the dry basis of the material, and add 50-60% and 40-50% of the total amount of manganese dioxide in two time periods: 0-24h and 24-72h, respectively. S4 initial reaction window: 0–72 h using continuous aeration or intermittent aeration with a duty cycle ≥50%, with a ventilation rate of 0.15–0.25 L·min. -1 ·kg -1 (Based on volatile solids), and the pH of the pile is maintained at 6.6–7.2 by an acid conditioner; S5 Subsequent Maturation: After the initial window is completed, continue aerobic composting until at least two of the following conditions are met: germination index GI ≥ 80%, stable compost temperature ≤ 40℃ for 48 hours, or finished product C / N ≤ 20.

2. The method for nitrogen retention in aerobic composting of pig manure with synergistic directional humification of catechol and manganese dioxide according to claim 1, characterized in that, The acid regulator is one of phosphoric acid, citric acid, or a mixture thereof.

3. The method for nitrogen retention in aerobic composting of pig manure with synergistic directional humification of catechol and manganese dioxide according to claim 1, characterized in that, The dry weight of the carbon-rich loosening agent accounts for 10-40% of the total dry weight of pig manure and the carbon-rich loosening agent, and the particle size of the carbon-rich loosening agent is 5-30 mm.

4. The method for nitrogen retention in aerobic composting of pig manure with synergistic directional humification of catechol and manganese dioxide according to claim 3, characterized in that, One or more of sawdust, straw, or rice husks are oxidized at 40–60°C with a 0.5–2.0 wt% hydrogen peroxide aqueous solution for 30–120 min. After washing and drying, the total phenol content on the surface, calculated as catechol equivalent, is ≥0.50 mmol·g. -1 Then, γ-MnO2 is anchored on the fiber pore wall by in-situ impregnation deposition, with a loading of 0.10 to 0.50 wt%.

5. The method for nitrogen retention in aerobic composting of pig manure with synergistic directional humification of catechol and manganese dioxide according to claim 1, characterized in that: The duty cycle of the intermittent aeration is 60-80%, and the single cycle is 10-30 minutes.

6. The method for nitrogen retention in aerobic composting of pig manure with synergistic directional humification of catechol and manganese dioxide according to claim 1, characterized in that, The particle volume distribution of the active manganese dioxide d 50 The wavelength range is 50–200 nm.

7. The method for nitrogen retention in aerobic composting of pig manure with synergistic directional humification of catechol and manganese dioxide according to claim 6, characterized in that, The BET relative specific surface area of ​​the active manganese dioxide is 80-150 m². 2 ·g -1 .

8. The method for nitrogen retention in aerobic composting of pig manure with synergistic directional humification of catechol and manganese dioxide according to claim 7, characterized in that, XPS analysis of the active manganese dioxide showed that the oxygen vacancy peak area accounted for 20-30% of the O1s peak.

9. The method for nitrogen retention in aerobic composting of pig manure with synergistic directional humification of catechol and manganese dioxide according to claim 8, characterized in that, Mn in activated manganese dioxide 3+ / Mn 4+ The atomic ratio is 0.35 to 0.

70.

10. The method for nitrogen retention in aerobic composting of pig manure with synergistic directional humification of catechol and manganese dioxide according to claim 1, characterized in that, The active manganese dioxide is a Bi-Co-Cu ternary doped material with a total doping amount of 0.2–1.5 at.%.