Rice field straw returning method for carbon sequestration and emission reduction

Abstract

The invention relates to the technical field of agricultural environmental protection, in particular to a carbon sequestration and emission reduction rice field straw returning method, which comprises the following steps: performing multistage crushing pretreatment on straws, mixing with red mud, performing gradient pyrolysis to prepare magnetic biochar, fixing specific strains, returning to the field, constructing a three-layer stubble burying structure to improve soil, and performing sensor monitoring and neural network regulation. And carbon sequestration emission reduction and intelligent management are realized, and the carbon flow direction can be tracked and a carbon sink voucher can be generated. According to the invention, through straw pretreatment, biochar preparation and fungus-carbon coupling returning, efficient carbon sequestration and emission reduction can be realized; the three-layer stubble burying structure is matched with humic acid, so that the soil structure is improved, the air permeability and water and fertilizer retention performance are improved, and crop growth is facilitated; by means of sensor monitoring and neural network regulation and control, precise management is achieved, carbon metering is conducted by combining isotope labeling with the block chain, data are accurate and safe, and powerful support is provided for carbon transactions and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural environmental protection, and specifically to a method for returning rice straw to the field for carbon sequestration and emission reduction. Background Art

[0002] In the context of current agricultural sustainable development and response to climate change, the reasonable treatment of rice straw and carbon sequestration and emission reduction technologies have become research hotspots. Traditional methods of returning rice straw to the field have many drawbacks, seriously restricting the improvement of the agricultural ecological environment and the achievement of carbon emission reduction goals.

[0003] From the perspective of carbon sequestration and emission reduction, common methods such as directly returning straw to the field or simply burning it not only fail to fully utilize the carbon resources in the straw, but also produce a large amount of greenhouse gases due to incomplete decomposition of the straw. Ordinary methods of returning straw to the field lack scientific regulation of straw treatment and microbial utilization, resulting in a large amount of methane emissions and extremely low carbon sequestration efficiency, making it difficult to meet the growing global demand for carbon emission reduction.

[0004] In terms of soil improvement, traditional practices are difficult to effectively improve the soil structure. Simple burying of straw cannot form an ideal pore structure, and the air permeability, water retention, and fertilizer retention of the soil cannot be significantly improved. Moreover, it may even affect the soil nutrient balance due to slow decomposition of the straw, being unfavorable to the growth and development of crop roots, and thus affecting crop yield and quality.

[0005] For farmland management and carbon accounting, traditional methods rely on manual experience and lack real-time and accurate monitoring and regulation means. It is impossible to timely grasp key indicators such as the Eh value, CH4 concentration, and microbial activity of the soil, and it is difficult to adjust irrigation and fertilization strategies according to the actual situation of the soil, resulting in waste of resources and environmental pollution. At the same time, in the field of carbon accounting and carbon trading, there is a lack of scientific, accurate, and traceable accounting methods and data management systems, which cannot provide a reliable basis for carbon asset trading and hinder the healthy development of the agricultural carbon trading market.

[0006] In summary, the existing rice straw returning technologies to the field have obvious deficiencies in carbon sequestration and emission reduction, soil improvement, as well as precise management and carbon accounting. There is an urgent need for an innovative method to solve these problems to achieve green and sustainable development of agriculture. Summary of the Invention

[0007] Technical Problems to be Solved

[0008] In view of the above-mentioned disadvantages of the prior art, the present invention provides a method for returning rice straw to the field for carbon sequestration and emission reduction. Through straw pretreatment, biochar preparation, and coupling of bacteria and biochar for returning to the field, the present invention can efficiently sequester carbon and reduce emissions; the three-layer stubble burying structure is combined with humic acid to improve the soil structure and enhance its air permeability, water retention, and fertilizer retention properties, which is beneficial to crop growth; with the help of sensor monitoring and neural network regulation, precise management is achieved, and carbon metering is carried out by combining isotope labeling with blockchain, and the data is accurate and secure, providing strong support for carbon trading and the like.

[0009] Technical solution

[0010] To achieve the above object, the present invention is realized through the following technical solutions:

[0011] A method for returning rice straw to the field for carbon sequestration and emission reduction, the method comprising the following steps:

[0012] S1. Multi-stage crushing and pretreatment of straw: Use a double-knife roll differential harvesting and crushing integrated machine to complete rice harvesting. The front knife roll longitudinally cuts to form straw segments of 5-8 cm, and the rear knife roll transversely rubs and processes to make the fiber fragmentation degree ≥ 85%, and the coefficient of variation of the crushing uniformity ≤ 10%;

[0013] S2. Gradient activation preparation of biochar: Mix the straw obtained in step S1 with a red mud catalyst at a dosage of 5-8%, and perform three-stage gradient pyrolysis in a mixed atmosphere with a volume ratio of CO2 and N2 of 1:3. Specifically, the three-stage gradient pyrolysis is: 200 °C / 30 min → 400 °C / 1 h → 550 °C / 2 h, to generate magnetic biochar with a specific surface area ≥ 120 m 2 / g and a pore size distribution of a composite structure of micropores and mesopores, where the micropores < 2 nm and the mesopores are 2-50 nm, and the Fe3O4 loading in the magnetic biochar is 3-5%;

[0014] S3. Coupling of bacteria and biochar for returning to the field: Fix halophilic methane-oxidizing bacteria and thermotolerant cellulose-decomposing bacteria in the pores of biochar at a ratio of 1:2, and the survival rate of the bacterial agent ≥ 90% / 30 days, and apply the biochar-bacterial agent complex at 20-30% of the dry weight of the straw;

[0015] S4. Three-dimensional stubble burying and soil improvement: Use a hydraulic reversible plow and a rotary tiller to work together to construct a three-layer stubble burying structure: a surface biochar mixing layer of 0-10 cm, a middle straw-bacterial agent composite layer of 10-25 cm, and a bottom red mud solidification layer of 25-40 cm, and apply a humic acid binder to form a honeycomb-like pore structure;

[0016] S5. Intelligent regulation and carbon metering: Deploy a sensor array with LoRa communication to monitor the soil Eh value, CH4 concentration, and microbial activity in real time, dynamically adjust the irrigation strategy and the activation frequency of the bacterial agent through a convolutional neural network, and simultaneously apply δ13C isotope labeling to track the carbon flow of the straw and generate a blockchain carbon sink certificate.

[0017] Furthermore, in step S2, the red mud catalyst needs to be modified with hydrochloric acid with a concentration of 0.5 mol / L, and the solid-liquid ratio is 1:5 to increase the specific surface area to 150 m 2 / g, and magnetic loading is achieved by co-precipitation with an Fe 2 + / Fe 3 + molar ratio of 1:2 and an external magnetic field intensity of 0.5 T.

[0018] Even further, the immobilization of the microbial agent adopts the sodium alginate-biochar composite gel embedding technology, with the pore size distribution having a matching degree with the cell size of ≥90%, and a micro-aerobic environment is constructed to maintain the activity of methane-oxidizing bacteria, and the dissolved oxygen in the micro-aerobic environment is 0.5 - 1.5 mg / L.

[0019] Even further, the intelligent control system includes:

[0020] The multi-spectral drone collects the NDVI index and thermal infrared images of the paddy field every week to construct a three-dimensional emission model;

[0021] The edge computing gateway runs the LSTM neural network model, where the prediction accuracy R 2 ≥0.92;

[0022] The water valve driven by piezoelectric ceramics and the electronically controlled microbial agent atomizing nozzle, with the response time of the water valve driven by piezoelectric ceramics ≤50 ms and the droplet diameter of the electronically controlled microbial agent atomizing nozzle being 50 - 80 μm.

[0023] Even further, a regional adaptation model is established:

[0024] Humid and hot climate area: The red mud content is increased to 10% and ventilation blind pipes are set, with the spacing of the ventilation blind pipes being 1.5 m;

[0025] Saline-alkali area: The biochar is modified with 1 mol / L NaOH to increase the porosity by 40%.

[0026] Even further, the whole life cycle management includes:

[0027] During the straw collection stage, UHF RFID tags are used to track the moisture content and calorific value;

[0028] During the biochar production stage, a microwave energy monitoring system is deployed, with the standing wave ratio ≤1.5;

[0029] The carbon sink data generates an immutable certificate through the Hyperledger Fabric architecture.

[0030] Even further, in step S3, the composite microbial agent adopts the sodium alginate-biochar composite gel embedding technology, specifically including:

[0031] Mix magnetic biochar with sodium alginate solution at a mass ratio of 1:3 to form a gel precursor;

[0032] Prepare gel microspheres with a particle size of 50 - 200 μm by microfluidic technology, and the matching degree between the pore diameter and the cell size is ≥ 90%;

[0033] Construct a gradient oxygen environment inside the gel microspheres, specifically: the dissolved oxygen on the surface layer is 1.5 - 2.0 mg / L, the dissolved oxygen in the core area is 0.3 - 0.8 mg / L, and simultaneously load 0.5 - 1.0% humic acid as a slow-release nutrient source.

[0034] Furthermore, the biochar preparation process in step S2 is dynamically regulated by a machine learning model, specifically including:

[0035] Construct an LSTM neural network model, and the input parameters include: straw moisture content: 8 - 12%, red mud catalyst dosage: 5 - 8%, heating rate: 10 - 20 °C / min;

[0036] Real-time collect the flow rate of the CO2 and N2 mixed gas during the carbonization process, which is 0.8 - 1.2 m / s, and the specific surface area data of the product, and optimize the model parameters through transfer learning, and the prediction accuracy R 2 ≥ 0.93;

[0037] Dynamically adjust the microwave power density and the injection rate of the activator NH3 according to the model output. The microwave power density is 1.5 - 2.0 W / cm 3 , so that the specific surface area of the biochar is stabilized in the range of 120 - 150 m 2 / g.

[0038] Furthermore, the method for generating blockchain carbon sink certificates includes:

[0039] Determine the δ13C value: -28‰ to -26‰ by laser ablation-isotope mass spectrometry coupling technology, and establish a straw carbon fingerprint database;

[0040] Deploy private chain nodes based on Hyperledger Fabric. Each block contains a timestamp, GPS coordinates, and the hash value of the carbon sequestration amount, where the timestamp error of each block is ≤ 1 s;

[0041] Introduce a zero-knowledge proof algorithm to verify the data authenticity and ensure that the privacy data is not leaked during carbon asset transactions.

[0042] Beneficial effects

[0043] Adopting the technical solution provided by the present invention, compared with the known public technology, it has the following

[0044] Beneficial effects:

[0045] 1. The present invention adopts a three-layer stubble burying structure constructed by the joint operation of a hydraulic reversible plow and a rotary tiller, a surface biochar mixed layer, a middle straw-bacterial agent composite layer, and a bottom red mud solidification layer, and a humic acid binder to form a honeycomb pore structure, which can enhance the air permeability, water retention and fertilizer retention of the soil. The red mud solidification layer can also prevent leakage of the bottom layer, optimize the physical and chemical properties of the soil, and create a good environment for crop growth.

[0046] Second, the present invention pre-processes the straw through multi-stage crushing, so that the straw fiber cracking degree is ≥85% and the coefficient of variation of crushing uniformity is ≤10%, and then the biochar is prepared by gradient activation, and the specific surface area of the generated magnetic biochar is ≥120m 2 / g, this biochar is coupled with a specific proportion of halophilic methanotrophic bacteria and thermostable cellulose decomposing bacteria and returned to the field, which can make full use of the characteristics of microorganisms and biochar, accelerate the fixation and conversion of straw carbon in the soil, inhibit methane production, effectively reduce carbon emissions from rice fields, and enhance carbon fixation capacity.

[0047] 3. The present invention uses the LoRa communication sensor array to monitor key soil indicators in real time, and uses convolutional neural networks to dynamically adjust irrigation strategies and microbial activation frequency to achieve precision agricultural management and improve resource utilization efficiency. At the same time, δ13C isotope labeling is used to track the flow of straw carbon, and blockchain technology is combined to generate tamper-proof carbon sink certificates to ensure scientific and accurate carbon measurement, providing solid data support and security for carbon trading and carbon asset management. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] The present invention will be further described below in conjunction with the embodiments.

[0050] Example 1: Basic technical solution

[0051] S1. Multi-stage crushing and pretreatment of straw

[0052] Use a double-knife roller differential harvesting and crushing integrated machine (model: JQ-3000) to harvest rice and crush straw. The front knife roller makes longitudinal cuts to form straw segments with a length of 6 cm, and the rear knife roller performs transverse silk rubbing treatment, with a fiber fragmentation degree reaching 87% (≥85%), and the coefficient of variation of crushing uniformity being 8% (≤10%). The moisture content of the crushed straw is controlled at 10%, and it is calibrated in real time through an infrared moisture meter (accuracy ±0.5%). The crushed straw needs to enter the next process within 48 hours to prevent fiber oxidation and degradation.

[0053] S2. Preparation of biochar by gradient activation

[0054] Modification of red mud catalyst:

[0055] Mix red mud with 0.5 mol / L hydrochloric acid at a solid-liquid ratio of 1:5, stir for 2 h, then centrifuge at 3000 rpm for 10 min, and obtain the modified red mud catalyst after drying, with the specific surface area increased to 150 m 2 / g (the original red mud is 80 m 2 / g).

[0056] Magnetic loading is achieved by the coprecipitation method: Mix Fe 2+ and Fe 3+ at a molar ratio of 1:2, react under an external magnetic field strength of 0.5 T to form uniform Fe3O4 nanoparticles.

[0057] Mixing and gradient pyrolysis:

[0058] Mix the straw obtained in step S1 with the modified red mud at a dosage of 6%, place it in a mixed atmosphere with a volume ratio of CO2 to N2 of 1:3, and perform three-stage gradient pyrolysis:

[0059] The first stage: 200 °C / 30 min (volatile organic compounds are removed in the initial stage of pyrolysis, heating rate 10 °C / min);

[0060] The second stage: 400 °C / 1 h (promote the formation of carbon skeleton, microwave power density 1.5 W / cm 3 );

[0061] The third stage: 550 °C / 2 h (the Fe3O4 loading reaches 4%, microwave power density is increased to 2.0 W / cm 3 ).

[0062] Finally, magnetic biochar is prepared, with a specific surface area of 135 m 2 / g (≥120 m 2 / g), pore size distribution is a composite structure of micropores (<2 nm) and mesopores (2 - 50 nm), and porosity is 45%.

[0063] S3. Bacteria-biochar coupling for returning to the field

[0064] Embedding of microbial agents:

[0065] Mix the halophilic methanotroph (strain number: Methylococcus sp. HY-01) and the thermotolerant cellulose-decomposing bacterium (strain number: Thermobifida fusca TF-02) in a ratio of 1:2.

[0066] Fix them in the pores of biochar through the sodium alginate-biochar composite gel embedding technology:

[0067] Particle size of gel microspheres: 100 μm;

[0068] Pore matching degree: 92% (≥90%);

[0069] Dissolved oxygen gradient: 1.8 mg / L at the surface layer and 0.5 mg / L in the core area.

[0070] The survival rate of microbial agents remains 93% (≥90%) within 30 days, and the addition amount of humic acid slow-release agent is 1.0%.

[0071] Application ratio: Apply the biochar-microbial agent complex to the field according to 25% of the dry weight of straw, and use a pneumatic broadcaster (spreading uniformity ≥95%).

[0072] S4. Three-dimensional stubble burial and soil improvement

[0073] Adopt the combined operation of a hydraulic reversible plow (model: HF-500) and a rotary tiller (model: XG-2000) to construct a three-layer stubble burial structure:

[0074] Surface layer (0 - 10 cm): Biochar mixed layer, forming a honeycomb-like pore structure (porosity 45%) with humic acid binder (addition amount 2 kg / mu) to improve soil air permeability;

[0075] Middle layer (10 - 25 cm): Straw-microbial agent composite layer, straw density is 300 kg / mu, and the ATP content of microbial activity ≥5 nmol / g;

[0076] Bottom layer (25 - 40 cm): Red mud solidification layer, red mud content is 8%, and the compaction degree reaches 90% to prevent bottom leakage.

[0077] S5. Intelligent regulation and carbon metering

[0078] Sensor deployment:

[0079] Deploy a LoRa sensor array (model: LS-200) in each 10m×10m grid in the field to monitor in real time:

[0080] Soil Eh value (-150 to +200 mV);

[0081] CH4 concentration (accuracy ±0.1 ppm);

[0082] Microbial activity (ATP detector accuracy ±0.2 nmol / g).

[0083] Dynamic regulation:

[0084] Analyze sensor data through a convolutional neural network (CNN) model, and dynamically adjust the irrigation water volume (error ≤5%) and the parameters of the microbial agent atomizing nozzle (droplet diameter 60 μm, claim range 50 - 80 μm).

[0085] The edge computing gateway (model: ECG - 5000) runs the LSTM model (R 2 = 0.94, claim ≥0.92), and the prediction error of the CH4 emission peak time is ≤10 min.

[0086] Carbon tracking and certificate generation:

[0087] Apply the δ13C isotope labeling technology (δ13C value -27‰) to track the carbon flow of straw;

[0088] The blockchain carbon sink certificate is generated through the Hyperledger Fabric architecture. Each block contains a timestamp (error ≤1 s), GPS coordinates, and the hash value of the carbon sequestration amount, and the zero - knowledge proof algorithm (ZKP - 200 protocol) is introduced to ensure data privacy.

[0089] Example 2: Adaptation plan for humid and hot climate areas

[0090] Adjust the following parameters based on Example 1:

[0091] The red mud content is increased to 10%, and ventilation ducts (spacing 1.5 m) are set at the bottom, made of PVC material (diameter 50 mm) to enhance soil air permeability;

[0092] The pyrolysis heating rate is adjusted to 15 °C / min, the pyrolysis cycle is shortened to 2.5 h, and the microwave power density is stabilized at 1.8 W / cm 3 ;

[0093] Intelligent control system upgrade:

[0094] Optimize the response time of the piezoelectric ceramic - driven water valve to 45 ms;

[0095] The multi - spectral drone (model: MSD - 1000) collects the NDVI index (resolution 0.1 m 2 ) and thermal infrared images every week to construct a three - dimensional emission model (error ≤8%).

[0096] Example 3: Adaptation plan for saline - alkali land

[0097] Biochar modification: React biochar with 1 mol / L NaOH solution for 24 h, the porosity increases by 42%, and the specific surface area increases to 145 m 2 / g;

[0098] Bacterial agent formula adjustment: Increase the proportion of halophilic bacteria to 1:1, and adjust the dissolved oxygen gradient to 2.0 mg / L on the surface layer and 0.8 mg / L in the core area;

[0099] Carbon metering optimization: Determine the δ13C value (error ±0.3‰) by laser ablation-isotope mass spectrometry (LA-ICP-MS), and deploy a microwave energy monitoring system (voltage standing wave ratio ≤1.5).

[0100] Control example

[0101] Control example 1: Single-temperature pyrolysis

[0102] Modify step S2 to single-temperature pyrolysis at 550 °C for 3 h, and the rest is the same as in Example 1.

[0103] Result: The specific surface area of the biochar is only 90 m 2 / g, the Fe3O4 loading is uneven (3.2%), and the porosity drops to 30%.

[0104] Control example 2: Without using the bacterial agent embedding technology

[0105] Directly mix the bacterial agent with the biochar in step S3, without using gel embedding.

[0106] Result: The survival rate of the bacterial agent drops to 70% after 30 days, the CH4 emission reduction decreases by 35%, and the microbial activity retention rate is only 75%.

[0107] Control example 3: Traditional irrigation management

[0108] Omit the intelligent regulation system in step S5 and adopt manual irrigation and fertilization.

[0109] Result: The soil Eh value fluctuates by ±50 mV, the microbial activity retention rate is only 82%, and the CH4 emission reduction decreases by 58%.

[0110] Comparison table:

[0111] Table 1: Comparison of biochar performance

[0112]

[0113] Examples 1-3 significantly improve the specific surface area and porosity of biochar through gradient pyrolysis and red mud modification, while the performance of Control Example 1 decreases due to single-temperature pyrolysis. The saline-alkali land adaptation scheme (Example 3) further optimizes the pore structure through NaOH modification and is suitable for high-salt environments.

[0114] Table 2: Activity of Bacterial Agent and Emission Reduction Effect

[0115]

[0116] The bacteria-carbon embedding technology in Example 1 ensures the long-term activity of the bacterial agent, and the CH4 emission reduction increases by 55%. In Comparative Example 2, the lack of embedding led to the death of the bacterial agent, resulting in a significant reduction in the emission reduction efficiency.

[0117] Table 3: Performance of Intelligent Control System

[0118]

[0119]

[0120] The intelligent control system in Examples 1-2 is optimized through real-time data, and the irrigation accuracy and response speed are significantly better than those of traditional management (Comparative Example 3). The carbon tracking error is controlled within 0.5‰, meeting the requirements of carbon trading certification.

[0121] In summary, through gradient pyrolysis, bacteria-carbon coupling, and intelligent control technologies in Example 1, a carbon sequestration efficiency of 2.8 tCO2e / mu, a CH4 emission reduction of 15.2 kg / mu, and a microbial activity retention rate of 95% are achieved; in Example 2, through the optimization of ventilation buried pipes and the LSTM model in a humid and hot climate area, the prediction accuracy of the CH4 peak reaches 94%, and the carbon sink certificate generation efficiency is increased by 20%; in Example 3, the porosity and bacterial agent ratio are optimized for saline-alkali land, the NDVI index error is ≤8%, and the security of carbon asset trading is guaranteed by the zero-knowledge proof algorithm.

[0122] The above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements for some of the technical features; and these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for returning rice straw to the field for carbon sequestration and emission reduction, characterized in that, The method includes the following steps: S1. Multi-stage crushing and pretreatment of straw: Use a double-knife roll differential harvester and crusher to complete rice harvesting. The front knife roll longitudinally cuts to form straw segments of 5 - 8 cm, and the rear knife roll transversely rubs and wires to make the fiber fragmentation degree ≥ 85%, and the coefficient of variation of the crushing uniformity ≤ 10%; S2. Preparation of biochar by gradient activation: Mix the straw obtained in step S1 with the red mud catalyst at a dosage of 5-8%, and perform three-stage gradient pyrolysis under a mixed atmosphere with a volume ratio of CO2 to N2 of 1:

3. The three-stage gradient pyrolysis is specifically as follows: 200 °C / 30 min → 400 °C / 1 h → 550 °C / 2 h, to generate magnetic biochar with a specific surface area ≥ 120 m 2 / g and a pore size distribution of a composite structure of micropores and mesopores, where the micropores are <2 nm and the mesopores are 2-50 nm, and the Fe3O4 loading in the magnetic biochar is 3-5%; S3. Coupled bacteria-biochar returning to the field: Fix halophilic methane-oxidizing bacteria and thermotolerant cellulose-decomposing bacteria in the pores of biochar at a ratio of 1:

2. The survival rate of the bacterial agent ≥ 90% / 30 days, and apply the biochar-bacterial agent complex at 20 - 30% of the dry weight of the straw; S4. Three-dimensional stubble burying and soil improvement: Use a hydraulic reversible plow and a rotary tiller to work together to construct a three-layer stubble burying structure: a surface biochar mixing layer of 0 - 10 cm, a middle straw-bacterial agent composite layer of 10 - 25 cm, and a bottom red mud solidification layer of 25 - 40 cm, and apply a humic acid binder to form a honeycomb-like pore structure; S5. Intelligent Regulation and Carbon Metering: Deploy a sensor array with LoRa communication to monitor soil Eh value, CH4 concentration and microbial activity in real time, dynamically adjust irrigation strategies and the activation frequency of microbial agents through a convolutional neural network, and simultaneously apply δ 13 C isotope labeling to trace the carbon flow of straw and generate blockchain carbon sink certificates.

2. The method for returning rice straw to the field for carbon sequestration and emission reduction according to claim 1, characterized in that, In the step S2, the red mud catalyst needs to be modified with hydrochloric acid with a concentration of 0.5 mol / L, and the solid-liquid ratio is 1:5 to increase the specific surface area to 150 m 2 / g. The magnetic loading is achieved by the coprecipitation method with the molar ratio of Fe 2 + / Fe 3 + being 1:2, and the external magnetic field strength is 0.5 T.

3. The method according to claim 1, wherein The immobilization of the bacterial agent uses the sodium alginate-biochar composite gel embedding technology, with the pore size distribution and the cell size matching degree ≥ 90%, and constructs a micro-oxic environment to maintain the activity of methane-oxidizing bacteria. The dissolved oxygen in the micro-oxic environment is 0.5 - 1.5 mg / L.

4. The method according to claim 1, characterized in that The intelligent control system includes: A multi-spectral drone collects the NDVI index and thermal infrared images of the paddy field every week to construct a three-dimensional emission model; The edge computing gateway runs the LSTM neural network model, where the prediction accuracy R 2 ≥ 0.92; A piezoelectric ceramic-driven water valve and an electronically controlled bacterial agent atomizing nozzle. The response time of the piezoelectric ceramic-driven water valve ≤ 50 ms, and the droplet diameter of the electronically controlled bacterial agent atomizing nozzle is 50 - 80 μm.

5. The method according to claim 1, wherein Establish a regional adaptation model: In the hot and humid climate area: Increase the red mud content to 10% and set ventilation ducts, with the distance between the ventilation ducts being 1.5 m; In the saline-alkali area: Modify the biochar with 1 mol / L NaOH to increase the porosity by 40%.

6. The method according to claim 1, wherein The whole life cycle management includes: Use UHF RFID tags to track the moisture content and calorific value during the straw collection stage; Deploy a microwave energy monitoring system during the biochar production stage, with the standing wave ratio ≤ 1.5; The carbon sink data generates an immutable certificate through the Hyperledger Fabric architecture.

7. The method according to claim 1, characterized in that, In step S3, the composite bacterial agent uses the sodium alginate-biochar composite gel embedding technology, which specifically includes: Mix magnetic biochar and sodium alginate solution at a mass ratio of 1:3 to form a gel precursor; Prepare gel microspheres with a particle size of 50 - 200 μm through microfluidics technology, and the pore diameter and the cell size matching degree ≥ 90%; Construct a gradient oxygen environment in the gel microspheres, specifically: the dissolved oxygen in the surface layer is 1.5 - 2.0 mg / L, the dissolved oxygen in the core area is 0.3 - 0.8 mg / L, and simultaneously load 0.5 - 1.0% of humic acid as a slow-release nutrient source.

8. The method according to claim 2, characterized in that, The biochar preparation process in step S2 is dynamically controlled by a machine learning model, which specifically includes: Construct an LSTM neural network model, and the input parameters include straw moisture content: 8 - 12%, red mud catalyst content: 5 - 8%, heating rate: 10 - 20 °C / min; Real-time collect the flow rate data of the CO2 and N2 mixed gas at 0.8 - 1.2 m / s and the specific surface area data of the product during the carbonization process, optimize the model parameters through transfer learning, and the prediction accuracy R 2 ≥0.93; Dynamically adjust the microwave power density and the injection rate of the activator NH3 according to the model output, and the microwave power density is 1.5 - 2.0 W / cm 3 , so that the specific surface area of the biochar is stabilized in the range of 120 - 150 m 2 / g.

9. The method according to claim 5, characterized in that, The method for generating the blockchain carbon sink certificate includes: Determination of δ 13 C value by laser ablation-isotope mass spectrometry: -28‰ to -26‰, and establish a straw carbon fingerprint database; Deploy private chain nodes based on Hyperledger Fabric, where each block contains a timestamp, GPS coordinates, and a hash value of the carbon sequestration amount, and the timestamp error of each block is ≤ 1 s; Introduce the zero-knowledge proof algorithm to verify data authenticity and ensure that private data is not leaked during carbon asset transactions.

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