Preparation and application method of straw wet biochar for carbon sequestration and emission reduction in rice-wheat rotation

Abstract

The invention discloses a preparation method and an application method of straw wet biochar for carbon sequestration and emission reduction in rice and wheat rotation. The preparation method comprises the specific steps of preparation and application of the straw wet biochar. The preparation method of the straw wet biochar comprises the steps of raw material preparation, low-temperature combustion, normal-temperature slow oxidation, electromagnetic radiation treatment, microwave heating and light wave sterilization, filtration and freezing and cold storage treatment. The method is mainly used for improving straw resource utilization of a rice and wheat system. The preparation process is low in energy consumption and little in smoke dust, carbon volatilization in the straw is reduced, and the content of fixed carbon in the straw is greatly increased. According to the specific application, the compound fertilizer is mixed with fertilizer according to a certain weight ratio of the compound fertilizer to plough layer rice soil and then applied at a time during rice planting. Wherein the nitrogen fertilizer is a mixture of quick-acting urea nitrogen and slow-release urea nitrogen, and the phosphate fertilizer and the potash fertilizer are conventional fertilizers. The fertilizer can promote the increase of gaps in rice soil and the water retention of wheat soil, reduces the emission of N2O, CO2 and CH4 in the rice and wheat planting process after being applied, improves the organic carbon content of soil, reduces the emission of greenhouse gas carbon (CO2), and promotes the increase of the crop rotation yield of rice and wheat.

Description

Technical Field

[0001] The patent of this invention belongs to the fields of agricultural waste utilization technology, farmland soil carbon sequestration and emission reduction, and specifically involves the preparation and application method of straw wet biochar for carbon sequestration and emission reduction in rice-wheat rotation. Background Art

[0002] Farmland soils, as important carbon reservoirs, play a key role in the global carbon cycle. my country's farmland soil organic carbon reserves are approximately 50-60 picograms (Pg) of soil, accounting for 8-10% of the nation's total terrestrial ecosystem carbon storage. However, long-term intensive agricultural production has led to significant losses of soil organic carbon. This degradation trend not only weakens soil productivity but also exacerbates climate change through the release of CO2. Major emissions include nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4). CH4 emissions from rice paddies account for over 60% of agricultural CH4 emissions, while N2O emissions from farmland soils account for approximately 70% of agricultural N2O emissions. Farmland management practices, such as tillage systems, fertilization, and straw incorporation, significantly influence farmland greenhouse gas emissions and soil carbon dynamics. Straw incorporation is currently one of the primary methods for carbon sequestration in farmland soils in my country. Approximately 65% ​​of crop straw is returned to the fields in various forms each year. Long-term straw incorporation can increase soil organic carbon by an annual rate of 0.1-0.3 g / kg. However, direct straw incorporation into paddy fields suffers from rapid decomposition and short-lived effects, and is less effective in cold and cool regions. Whether direct straw incorporation can effectively enhance soil carbon sequestration and reduce carbon and nitrogen footprints remains uncertain. If straw incorporation is not accompanied by effective water and fertilizer regulation, it can easily lead to reduced crop yields and increased greenhouse gas emissions. Conversely, straw biochar, when applied as organic matter to rice paddies, not only significantly improves soil fertility and crop yields but also enhances soil carbon sequestration. Changes in the quantity and quality of the substrate directly influence SOM mineralization, SOC composition, and the composition and function of soil microbial and animal communities, effectively increasing soil carbon sequestration and significantly reducing the net greenhouse effect. This is because biochar itself contains 50-80% fixed carbon in a highly aromatic structure, with an average retention time in the soil of over a century. Field trials have shown that applying one ton of straw biochar per mu (approximately 1 acre) is equivalent to sequestering 0.5-0.7 tons of CO2. Long-term field experiments have shown that biochar addition increases soil organic carbon content by 20%-50%, with this increase persisting for decades.

[0003] my country produces a massive amount of crop straw annually. In 2021, the theoretical resource volume of major crop straw nationwide was approximately 860 million tons, of which corn, rice, and wheat straw accounted for over 80%. This straw is rich in organic matter and nutrients and, if properly utilized, can become a valuable renewable agricultural resource. Improper straw disposal can lead to serious environmental problems. Open-air burning not only wastes resources but also emits significant amounts of greenhouse gases and air pollutants. For example, burning each ton of straw releases approximately 1.5 tons of CO2 equivalent greenhouse gases, while also producing significant amounts of PM2.5 and other harmful gases. Anaerobic decomposition of randomly stacked straw produces methane, which has a global warming potential 28 times that of CO2. These improper disposal methods exacerbate climate change and environmental pollution, contradicting the principles of promoting an ecological civilization. Therefore, converting straw into biochar is a highly promising resource utilization method that can both address straw disposal challenges and contribute to carbon sequestration and emission reduction in farmland, achieving the dual goals of "turning waste into treasure" and "using waste to combat pollution."

[0004] Rice (Oryza sativa L.) and wheat (Triticum aestivum L.) are one of the most important cereal crops in the world, which constitute the staple food of more than 50% of the world's population. Rice-wheat rotation system has been widely adopted in East and South Asia, ensuring food security for about 20% of the world's population. The large amount of straw produced by rice-wheat planting is generally applied directly to the field. With the increase of years, soil fertility decreases, greenhouse gas emissions increase, and eventually leads to yield decline and certain damage to the ecological environment. Studies have shown that straw biochar can increase the SOC content of rice-wheat rotation soil by about 37.8%, reduce carbon emissions by 18.6%, and improve soil fertility and crop yield. Therefore, straw biochar has great application value in rice-wheat systems. At present, the main methods for preparing straw biochar are pyrolysis and hydrothermal carbonization. Pyrolysis carbonization is a technology that converts biomass or other carbon-containing raw materials into carbon-rich solids (biochar), liquids (bio-oil), and gas products in an oxygen-free or inert atmosphere at high temperatures. The principle is based on the thermal chemical decomposition and recombination of organic matter at high temperatures. The temperature is usually 300℃-800℃, and the target product is adjusted (low-temperature carbon production is the main, high-temperature gas production is the main). Due to the lack of oxygen or inert gas (such as N2, Ar), the raw material is prevented from burning. It is usually carried out under normal pressure or slightly negative pressure (some processes use vacuum pyrolysis), for several minutes to several hours (slow pyrolysis takes several hours, fast pyrolysis only takes several seconds to several minutes). But the raw material needs to be dried (moisture <15%), and solid organic matter (such as wood, straw, plastic, etc.) can be directly processed. Generally, low-temperature (300℃-400℃) biochar retains more raw material structure and functional groups, suitable for applications that require high surface activity; medium-temperature (400℃-600℃) biochar has a balanced pore structure and surface chemical properties; high-temperature (>600℃) biochar has a highly graphitized structure and electrical conductivity, suitable for energy-related applications. However, there are still some main defects in the preparation of straw biochar by pyrolysis: 1) technical defects in the preparation process, mainly high energy consumption of 800kWh / ton-1200kWh / ton, cost of 600 yuan / ton-1000 yuan / ton, high carbon emissions and tar and waste gas pollution, and raw material adaptability limitation. The ash content of straw biomass (rice straw ash content >15%) is high, and high-temperature pyrolysis easily leads to sintering of the pore structure, reducing the specific surface area by 30%-50% (such as wheat straw specific surface area from 450m 2 / g to 280m 21) Product performance. The physicochemical properties fluctuate greatly, the nutrient supply capacity is weak, the carbon stability is controversial, the product quality fluctuates greatly, the carbon content difference is ± 15%, the long-term carbon sequestration efficiency is not clear and may be overestimated; 2) Ecological risks of field application. Soil ecological disturbance, heavy metal activation risk, and water regulation contradiction; 3) Economic and popularization bottleneck. High production cost, difficult realization of carbon sink value, and large dosage span of 1-50 t / ha; 4) Environmental and health risks. Nanoparticle release through food chain enrichment, induction of oxidative stress, and cytotoxicity risk. Polycyclic aromatic hydrocarbon residues exist in food safety hidden dangers.

[0005] In addition, hydrothermal carbonization (HTC) is a technology for converting biomass into carbon-rich solid products (hydrochar) in a high-temperature and high-pressure hydrothermal environment. Its principle is based on the thermal chemical decomposition and reorganization process of biomass in water, usually in the range of 180-250℃, which is higher than the boiling point of water but lower than the traditional pyrolysis temperature. Autogenous pressure (2-10 MPa) is maintained by the vapor pressure of water in a closed reactor. Several minutes to several hours, depending on the raw material and target product. Water acts as a reaction solvent and catalyst, without the need for chemical additives. The existing hydrothermal biochar has the following disadvantages: 1) Insufficient carbon stability and carbon sequestration efficiency, mainly manifested in low degree of aromaticity and easy biodegradation; 2) Technical bottlenecks in the process, mainly manifested in high energy consumption, difficulty in handling liquid byproducts, equipment corrosion and blockage; 3) Limitations of product performance, mainly poor pore structure development, weak nutrient retention ability and poor pH adjustment effect; 4) Economic and scale obstacles, mainly high production cost, imbalance between yield and value, and lack of standard system; 5) Environmental risk uncertainty. Mainly for the risk of loss of dissolved carbon, activation of heavy metals, and disturbance of microbial community.

[0006] In addition to the above pyrolysis and hydrothermal carbonization technologies, emerging technologies such as microwave pyrolysis are also gradually applied to the preparation of straw biochar. These methods usually have the advantages of low energy consumption and unique product characteristics, but still face challenges in large-scale production. To solve the problems of the above technologies, the present invention combines pyrolysis and wet process to develop a straw wet biochar. The preparation technology includes low-temperature pyrolysis technology, normal-temperature oxidation technology, and uses electromagnetic radiation, microwave heating, and light wave sterilization, freezing, etc. Finally, it is stored by refrigeration. The present invention is applied in rice-wheat rotation system in China, which can greatly reduce energy consumption and greenhouse gas emission flux, promote soil carbon sequestration, and promote rice and wheat yield. The straw biochar technology of the present invention provides an innovative solution to the dual challenges of food security and climate change through the transformation path of "waste-resource-ecological and economic benefits". SUMMARY

[0007] The technical problem to be solved by the present application is to provide a rice-wheat rotation straw wet biochar preparation method and application method for carbon sequestration and emission reduction, in order to realize rice-wheat straw resource utilization, and achieve ecological and economic benefits such as farmland carbon sequestration and emission reduction and crop yield increase.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0009] The present application is a rice-wheat rotation straw wet biochar for carbon sequestration and emission reduction, characterized in that the preparation method comprises the following steps: Figure 1 ):

[0010] Step 1: Preparation of straw wet biochar

[0011] Step 1. Preparation of raw materials

[0012] The rice is cut into 3-5 cm long, and the wheat straw is cut into 5-8 cm long, and the water content of the two kinds of straw is less than 10%. 84 disinfectant solution and pure water are mixed according to a volume ratio of 1:5 to prepare a dilute liquid oxidant A.

[0013] Step 2. Low temperature combustion

[0014] The cut straw in claim 1 is wrapped with tin paper (thickness not less than 20 microns) for at least 2 layers to prevent the tin paper from being damaged and insufficiently combusted. Then the wrapped tin paper is placed in a lithium long stone pot (wall thickness not less than 1 cm), and the entire stone pot is filled as much as possible to make the tin paper fully contact with the stone pot wall to prevent the straw inside the tin paper from receiving uneven heat source. Cover the pot lid. Place the stone pot containing straw on the fire, keep the flame temperature at about 400±10℃, and keep the stone pot wall temperature at 320-360℃ for 5 minutes. Reduce the flame temperature to keep the stone pot wall temperature at 280-290℃, and turn off the fire after 10 minutes. During this process, there is little smoke, if there is more smoke, it is because the tin paper is wrapped with more gaps. About 15 minutes later, take out the tin paper and place it in an empty iron pot on the water surface (wall thickness 0.2-0.5 cm), and place a layer of ice bag on the tin paper for rapid cooling. After about 10-15 minutes of cooling, the biochar is loaded into a self-sealing bag for use. There is no autogenous pressure during the entire process.

[0015] Step 3. Normal temperature slow oxidation

[0016] A certain amount of the above biochar loaded into the self-sealing bag is placed in a plastic bucket after one day, 5L of dilute liquid oxidant A is added according to 500g, and stirred thoroughly. Cover and stand for 24 hours. Then add 100mL of freshly squeezed lemon juice and stir evenly, cover and stand for 24 hours.

[0017] Step 4. Electromagnetic radiation treatment

[0018] Remove the lid from the rested biochar and irradiate with electromagnetic radiation for 1 hour, stirring every 20 minutes. If adding more than 500g of biochar at a time, avoid irradiating the biochar layer deeper than 20cm to allow the lower layer to be exposed to the electron radiation.

[0019] Step 5. Microwave heating and light wave sterilization

[0020] The electron-irradiated biochar was capped and microwaved for 3 minutes, then sterilized using light waves for 1 minute. The mixture was then cooled for 3.5 hours.

[0021] Step 6. Filter

[0022] Filter the biochar from step 5 through gauze (to remove excess water and some ash), and bucket the filtrate. Place the filter residue in a sealed ziplock bag.

[0023] Step 7. Freezing and Refrigeration (Preparation Completed)

[0024] The ziplock bag containing the wet biochar in step 6 is placed in -18°C and frozen for 12 hours. The frozen biochar is taken out and refrigerated at 4°C for use. The thawed wet biochar is the present invention ( Figure 2 ).

[0025] Furthermore, the straw wet biochar prepared from rice or wheat for carbon sequestration and emission reduction in the rice-wheat rotation has a total carbon content of approximately 445 g / kg to 460 g / kg, a total nitrogen content of 10.0 g / kg to 17.0 g / kg, a pH of approximately 7.5 to 9.0, a diameter of approximately 0.15 cm-0.35 cm and 0.35 cm-0.60 cm, a specific surface area increase range of approximately 10.0% to 16.0%, and a water content of approximately 75%-85%.

[0026] Furthermore, the effective chlorine content in the 84 disinfectant is in the range of 3.5%-5.0% (W / V). When the content of the diluent A oxidant is above this range, the ratio is adjusted to 1:8-1:10, and when the content of the diluent A oxidant is below this range, the ratio is adjusted to 1:2-1:4.

[0027] Furthermore, the pH of the pure water is approximately between 5.5 and 5.6, the EC value is 12.0±0.5μs / cm, the salinity and hydrogen content are both 0, the ORP negative potential is 270mv-275mv, the resistivity is 1.1kΩ-1.2kΩ, the total solid content is 6ppm, the specific gravity of seawater is 1, and the liquid fertilizer strength is 1 (fertilizer deficiency state).

[0028] Further, the dilution liquid oxidant A is characterized in that the pH of the dilution liquid oxidant A is about 10.0-10.2, the EC value is 17600us / cm-17610us / cm, the salinity is 0.98%, the hydrogen content is all 0, the ORP negative potential is 590mv-600mv, the resistivity is 1.4kΩ-1.5kΩ, the total solid content is about 8.7ppm-8.8ppm, the seawater specific gravity is 1.006, and the liquid fertility degree is 3 (over-fertilization state).

[0029] The second step is the application and effect of the straw wet biochar.

[0030] The straw wet biochar for carbon sequestration and emission reduction in rice-wheat rotation is applied according to the weight ratio of 6.3g / kg-6.5g / kg of the cultivated layer paddy soil, and is applied in the paddy planting by mixing with the fertilizer at one time. The nitrogen fertilizer (2.45gN / 15kg paddy soil) is the ratio of quick-acting urea nitrogen to slow-release urea nitrogen of 4:6, and the phosphorus fertilizer and potassium fertilizer are conventional fertilizers and the application method.

[0031] The diameter size of the present application can promote the increase of the void of the paddy soil and promote the water retention of the wheat soil. Therefore, after application, the N2O, CO2 and CH4 emission amounts in the rice-wheat planting process are reduced by about 10.0%-14.0%, 27.0%-30.0% and 32.0%-36.5% respectively. Meanwhile, the present application can improve the soil organic carbon content of the rice-wheat rotation system by about 13.0%-15.0% respectively, can finally reduce the greenhouse gas carbon (CO2) emission by 12.0%-16.0%, and can promote the yield of the rice-wheat rotation to increase by about 5.0%-10.0%.

[0032] Beneficial effects;

[0033] The present application is mainly used for rice-wheat system production, improves the straw resource utilization of rice and wheat, and turns waste into treasure. In the preparation process, the energy consumption can be reduced, the waste smoke generation can be reduced, the carbon volatilization in the straw can be reduced, and finally the fixed carbon content in the straw can be greatly improved. The present application is applied in the paddy soil according to a certain weight ratio, can promote the void of the water and dry farmland soil, can conserve water and promote the growth of microorganisms, can increase the organic matter decomposition and the total carbon content, thereby reducing the N2O, CO2 and CH4 emission amounts in the rice-wheat planting process. In addition, the present application can further improve the soil organic carbon content of the rice-wheat rotation system in cooperation with the nitrogen fertilizer reduction treatment, finally reduces the gas carbon emission of the whole rotation system, and promotes the yield of the rice-wheat rotation to increase. BRIEF DESCRIPTION OF DRAWINGS

[0034] The above and / or other aspects of the present application will become apparent from the following detailed description of the application taken in conjunction with the accompanying drawings.

[0035] Figure 1 The present application is prepared according to the flow chart.

[0036] Figure 2 The invention prepares straw raw materials and straw wet biochar for carbon sequestration and emission reduction. DETAILED DESCRIPTION

[0037] The present invention can be better understood with reference to the following examples.

[0038] The structures, proportions, sizes, etc. illustrated in the drawings of the specification are only used to match the contents disclosed in the specification for understanding and reading by those familiar with this technology. They are not used to limit the conditions for implementation of the present invention and therefore have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose of the present invention. At the same time, terms such as "upper", "lower", "front", "back", and "middle" quoted in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships should also be considered as the scope of implementation of the present invention without substantially changing the technical content. DETAILED DESCRIPTION

[0040] The present invention can be better understood with reference to the following examples.

[0041] The present invention provides a method for preparing wet straw biochar for carbon sequestration and emission reduction in rice-wheat rotation and its application. While there are numerous methods and approaches for implementing this technical solution, the above-described embodiments are merely preferred embodiments of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of the present invention. Any components not specified in this embodiment may be implemented using existing technologies.

[0042] This embodiment was carried out in a plastic multi-span greenhouse at the Horticulture Station of the Mufu Campus of Jinling Institute of Technology, and provided a method for preparing wet straw biochar for carbon sequestration and emission reduction in rice-wheat rotation and its application. The specific steps include preparing wet straw biochar and its application. The preparation of wet straw biochar of the present invention includes raw material preparation, low-temperature combustion, slow oxidation at room temperature, electromagnetic radiation treatment, microwave heating and light wave sterilization, filtration, freezing and refrigeration treatment (preparation completed). The embodiment of the present invention is derived from the Jiangsu Provincial Natural Science Foundation Youth Fund "Study on the Key Mechanism of Exogenous Carbon, Nitrogen and Water Coupling on Soil Carbon Sequestration in Rice and Wheat Systems (BK20230112)". The specific steps of this embodiment ( Figure 1 )as follows:

[0043] Step 1: Preparation of wet straw biochar

[0044] 1. Raw material preparation

[0045] Rice straw with a moisture content of less than 10% was chopped into 3-5 cm pieces, and wheat straw was chopped into 5-8 cm pieces. 84 disinfectant was mixed with purified water in a volume ratio of 1:5 to prepare dilute oxidant A. The available chlorine content of the 84 disinfectant used ranged from 3.5% to 5.0% (W / V). Above this range, the ratio of diluted oxidant A was adjusted to 1:8-1:10, and below this range, the ratio was adjusted to 1:2-1:4. The purified water used had a pH of approximately 5.55, an EC value of 12.0 μs / cm, a salinity and hydrogen content of 0, an ORP negative potential of 273 mv, a resistivity of 1.17 kΩ, a total solids content of 6 ppm, a seawater specific gravity of 1.000, and a liquid fertilizer strength of 1 (fertilizer deficiency). The pH of the obtained diluted oxidant A is about 10.1, the EC value is 1720μs / cm, the salinity is 0.98%, the hydrogen content is 0, the ORP negative potential is 598mv, the resistivity is 1.45kΩ, the total solid content is about 8.72ppm, the seawater specific gravity is 1.006, and the liquid fertilizer strength is 3 (over-fertilization state).

[0046] 2. Low temperature combustion

[0047] Wrap the chopped straw from claim 1 in at least two layers of tin foil (thickness no less than 20 microns) to prevent damage and incomplete combustion. Then, place the wrapped tin foil into a lithium feldspar pot (wall thickness no less than 1 cm), filling the pot as completely as possible so that the foil is in full contact with the pot wall. This prevents uneven heat distribution to the straw within the tin foil. Cover the pot. Heat the pot containing the straw over a fire, maintaining a flame temperature of approximately 400°C ± 10°C and a pot wall temperature of 320°C-360°C for 5 minutes. Lower the flame temperature to maintain a wall temperature of 280°C-290°C, and turn off the heat after 10 minutes. This process should produce minimal smoke and dust. Excessive smoke and dust indicates that the tin foil is not tightly wrapped and has numerous gaps. After approximately 15 minutes, remove the tin foil and place it in an empty iron pot (wall thickness 0.2-0.5 cm) placed on water. Place an ice pack on top of the tin foil for rapid cooling. After cooling for about 10-15 minutes, the biochar is placed in a ziplock bag for later use. There is no self-generated pressure during the entire process.

[0048] 3. Slow oxidation at room temperature

[0049] After 500g of the biochar in the ziplock bag has been left for one day, place it in a plastic bucket. Add 5L of diluted oxidant A and stir thoroughly. Cover and let stand for 24 hours. Then, add 100mL of freshly squeezed lemon juice, stir thoroughly, and cover and let stand for 24 hours.

[0050] 4. Electromagnetic radiation treatment

[0051] The biochar was opened and irradiated with electromagnetic radiation for 1 hour, with stirring every 20 minutes.

[0052] 5. Microwave heating and light wave sterilization

[0053] The above electronic radiation covered biochar is placed in a microwave for 3 minutes, and then sterilized by light wave for 1 minute. It is cooled for 3.5 hours.

[0054] 6. Filtration

[0055] The biochar in step 5 is filtered with gauze, and the filtrate is placed in a barrel. The filter residue is placed in a self-sealing bag and sealed.

[0056] 7. Freezing and refrigeration treatment (preparation is completed)

[0057] The self-sealing bag containing the wet biochar in step 6 is placed in a freezer at -18°C for 12 hours. The frozen biochar is taken out and placed in a refrigerator at 4°C for use. At this time, the thawed wet biochar is the biochar of the present application. Figure 2 ).

[0058] The relevant performance indicators of the present application are shown in Table 1. As can be seen from Table 1, the total carbon content of the straw wet biochar prepared from rice or wheat in the rice-wheat rotation carbon sequestration and emission reduction is about 459.0 g / kg and 449.3 g / kg, respectively, the total nitrogen content is 16.5 g / kg and 10.9 g / kg, respectively, the pH is about 7.8 and 8.6, respectively, the average particle diameter is about 0.25 cm and 0.45 cm, respectively, the specific surface area is increased by about 10.6% and 15.5%, respectively, and the water content is about 75.5% and 84.5%, respectively.

[0059] Second step: application of straw wet biochar

[0060] Rice is planted on July 4, 2024 (pot culture), and the amount of nitrogen applied is 15 kg of rice soil, 2.45 g of N (quick-acting urea N: slow-release urea N = 4:6), phosphorus fertilizer is diamine (18% N 46% P2O5), potassium fertilizer is potassium chloride (60% K2O), and the amount of application is 12.5 kg of rice soil, 1.02 g / kg and 0.78 g / kg, respectively. All fertilizers are applied at one time. The present application is in accordance with the wet biochar of rice and wheat straw, and the weight ratio of rice soil is 6.4 g / kg, which is applied to the soil at one time when rice is planted. The rice is harvested on November 23, 2024, and the wheat is planted on the soil after the rice is harvested on December 23 of the same year, and the fertilization management is consistent with that of rice. The rice irrigation management is dry and wet alternation, and the wheat irrigation is according to the local rice-wheat rotation guide. The wheat is harvested on May 24, 2025. The greenhouse gas (N2O, CO2, CH4) emission is determined at the tillering stage, baking field, heading and flowering stage, after all flowering, and harvesting stage.

[0061] Table 1 Biochar characteristics

[0062]

[0063] The results in Table 2 show that the rice-wheat planting process reduces about 13.50% N2O, 29.78% CO2, 36.12% CH4 emissions (using rice straw wet biochar), and 10.20% N2O, 27.37% CO2, 32.75% CH4 emissions (using wheat straw wet biochar). At the same time, the application of the present application increases the soil organic carbon content of the rice-wheat rotation system by about 14.2% (using rice straw wet biochar) and 13.6% (using wheat straw wet biochar), respectively, which can ultimately reduce 12.14% (wheat straw wet biochar) and 15.45% (rice straw wet biochar) greenhouse gas carbon (CO2) emissions, and promote the yield of wheat by about 5.4% (wheat straw wet biochar) and 8.6% (rice straw wet biochar), and the yield of rice by 6.3% (wheat straw wet biochar) and 9.6% (rice straw wet biochar).

[0064] Table 2 Carbon sequestration and emission reduction of the present application

[0065]

[0066] The present application provides a method for preparing and applying straw wet biochar for carbon sequestration and emission reduction in rice-wheat rotation. There are many methods and approaches to achieve this technical solution. The above description is only the preferred embodiment of the present application. It should be noted that for ordinary skilled persons in the technical field, several improvements and refinements can be made without departing from the principles of the present application. These improvements and refinements should also be considered within the scope of protection of the present application. The components not explicitly described in the embodiments can be implemented using existing technology.

Claims

1. A method for preparing wet straw biochar for carbon sequestration and emission reduction in rice-wheat rotation and its application, characterized in that: include: Preparation and application of wet straw biochar. Preparation of wet straw biochar involves raw material preparation, low-temperature combustion, slow oxidation at room temperature, electromagnetic radiation treatment, microwave heating and light wave sterilization, filtration, and freezing and refrigeration. The raw materials are 3cm-5cm rice straw and 5cm-8cm wheat straw segments (moisture content less than 10%), and a diluted oxidant A made by mixing 84 disinfectant and purified water in a 1:5 volume ratio. The low-temperature combustion process includes wrapping the straw segments with tinfoil. The wrapped tinfoil is then placed in a lithium feldspar stone pot and fully heated (the wall thickness is not less than 1 cm), maintaining the flame temperature at about 390°C-410°C and the stone pot wall temperature at 320°C-360°C for 5 minutes. The flame temperature is lowered to maintain the stone pot wall temperature at 280°C-290°C, and the fire is turned off after 10 minutes. After about 15 minutes, the tinfoil is taken out and placed in an empty iron pot (wall thickness 0.2cm-0.5cm) placed on the water surface, and a layer of ice pack is placed on the tinfoil for rapid cooling for 10-15 minutes. After cooling, the biochar is put into a ziplock bag for standby use. There is no self-generated pressure during the entire process. The room-temperature slow oxidation process involves placing a certain amount of the biochar in the ziplock bag for one day into a plastic bucket. Add 5L of diluted oxidant A (500g) and stir thoroughly. Cover the container and let it sit for 24 hours. Then, add 100mL of freshly squeezed lemon juice, stir evenly, and cover the container and let it sit for 24 hours. The electromagnetic radiation treatment process includes removing the sealed container from the rested biochar and subjecting it to electromagnetic radiation for one hour, stirring it every 20 minutes. If more than 500g of biochar is added at a time, the biochar layer in the barrel should be no thicker than 20cm during electromagnetic radiation treatment to ensure that the lower layer is exposed to the electrons. The microwave heating and light wave sterilization process includes sealing the electron-irradiated biochar, heating it in a microwave for 3 minutes, sterilizing it with light waves for 1 minute, and cooling it for 3.5 hours. The filtering process is performed using gauze, and the filter residue is placed in a ziplock bag and sealed. In the freezing and refrigeration treatment, the ziplock bag containing the wet biochar is placed in a -20°C ± 5°C environment and frozen for 12 hours, and then thawed to obtain the straw wet biochar. The straw wet biochar is stored under refrigeration at 2°C-4°C.

2. The straw wet biochar for carbon sequestration and emission reduction in rice-wheat rotation according to claim 1, characterized in that: The rice and wheat straw wet biochar of the present invention has a total carbon content of about 445g / kg-460g / kg, a total nitrogen content of about 10.0g / kg-17.0g / kg, a pH of about 7.5-9.0, a diameter of about 0.15cm-0.35cm and 0.35cm-0.60cm, a specific surface area increase range of about 10.0%-16.0%, and a water content of about 75%-85%.

3. The 84 disinfectant according to claim 1, characterized in that: The effective chlorine content in 84 disinfectant ranges from 3.5% to 5.0% (W / V). When preparing diluent A oxidant above this range, the ratio is adjusted to 1:8-1:10; when preparing diluent A oxidant below this range, the ratio is adjusted to 1:2-1:

4.

4. The purified water according to claim 1, characterized in that The pH of pure water is approximately between 5.5-5.6, the EC value is 11.5μs / cm-12.5μs / cm, the salinity and hydrogen content are both 0, the ORP negative potential is 270mv-275mv, the resistivity is 1.1kΩ-1.2kΩ, the total solid content is 6ppm, the specific gravity of seawater is 1, and the liquid fertilizer strength is 1 (fertilizer deficiency state).

5. The diluent oxidant A according to claim 1, characterized in that: The pH of the diluted oxidant A is approximately between 10.0 and 10.2, the EC value is 17600μs / cm-17610μs / cm, the salinity is 0.98%, the hydrogen content is 0, the ORP negative potential is 590mv-600mv, the resistivity is 1.4kΩ-1.5kΩ, the total solid content is approximately 8.7ppm-8.8ppm, the specific gravity of seawater is 1.006, and the liquid fertilizer strength is 3 (over-fertilization state).

6. The application of wet straw biochar for carbon sequestration and emission reduction in rice-wheat rotation according to claim 1, characterized in that: The nitrogen fertilizer (2.45g N / 15kg of paddy soil) is a 4:6 ratio of fast-acting urea nitrogen to slow-release urea nitrogen. Phosphate and potash fertilizers are conventional fertilizers and applied using the same method.

7. The application of wet straw biochar for carbon sequestration and emission reduction in rice-wheat rotation according to claim 1, characterized in that: The diameter of the wet straw biochar of the present invention can promote the increase of voids in paddy soil and promote water retention in wheat soil. Application of the present invention reduces N2O emissions by approximately 10.0%-14.0%, CO2 emissions by 27.0%-30.0%, and CH4 emissions by 32.0%-36.5% during rice and wheat cultivation. Furthermore, application of the present invention increases the soil organic carbon content in rice-wheat rotation systems by approximately 13.0%-15.0%, ultimately reducing greenhouse gas carbon (CO2) emissions by 12.0%-16.0%, and increasing rice-wheat rotation yields by approximately 5.0%-10.0%.

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