A biochar-based soil conditioner made from agricultural waste, its preparation and application

Abstract

This invention belongs to the field of agricultural waste resource utilization and soil improvement technology, specifically relating to a biochar-based soil conditioner made from agricultural waste, its preparation, and its application. The biochar-based soil conditioner is obtained by loading functional substances or biological agents onto agricultural waste after pyrolysis and carbonization. During the cooling stage, functional substances or biological agents are loaded in situ, utilizing the high adsorption capacity of biochar to achieve efficient immobilization and slow release of active ingredients. The resulting product has dual functions of soil structure improvement and root growth promotion, ultimately increasing crop yield.

Description

Technical Field

[0001] This invention belongs to the field of agricultural waste resource utilization and soil improvement technology, specifically relating to a biochar-based soil conditioner made from farmland waste and its preparation and application. Background Technology

[0002] With the increasing intensification and scale of modern agricultural production, the generation of agricultural waste, such as straw, rice husks, corn cobs, and peanut shells, is showing a significant upward trend. Current technologies primarily employ extensive methods for disposing of this waste, such as open-air burning or landfilling. These methods not only lead to a massive waste of valuable biomass resources but also easily cause a series of environmental problems, including air pollution, soil and water damage, due to incomplete combustion or indiscriminate dumping. Simultaneously, current agricultural production generally faces technical bottlenecks such as soil structure degradation, continuous decline in organic matter and fertility, and hindered crop root development, severely restricting the benign cycle and sustainable development of the agricultural ecosystem. Therefore, how to achieve efficient resource utilization of agricultural waste and synergistically improve soil physicochemical properties has become an urgent technical challenge to be solved in this field.

[0003] Biochar, a carbon-rich solid material formed by the pyrolysis and carbonization of agricultural waste under anaerobic or oxygen-limited conditions, has shown broad application prospects in soil improvement, carbon sequestration and emission reduction, and pollutant passivation due to its large specific surface area, abundant pore structure, and strong adsorption properties. However, current biochar preparation processes generally employ high-temperature carbonization, typically above 500℃, and require inert gas protection. These processes have drawbacks: high energy consumption and demanding preparation conditions, resulting in high production costs and severely hindering the widespread application of biochar products in production. Furthermore, current biochar-based soil conditioners generally have limited functions, only improving soil physical structure and enhancing water and fertilizer retention capacity, failing to address key issues such as slow crop root growth and low nutrient absorption efficiency. How to efficiently transform abundant agricultural waste into a biochar-based conditioner that combines soil structure improvement and root growth promotion has become a pressing technical challenge in this field. Therefore, developing a biochar-based soil conditioner preparation technology that is low in energy consumption and high in load, and has the functions of improving soil structure, promoting crop growth, and enhancing crop stress resistance is of great significance for realizing the resource utilization of agricultural waste, improving soil quality, and promoting the sustainable development of agricultural production, while also helping to reduce greenhouse gas emissions. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to overcome the shortcomings of existing technologies, such as low utilization rate of agricultural waste and limited functionality of traditional biochar, and to provide a biochar-based soil conditioner using agricultural waste as raw material. This conditioner can be prepared into a biochar-based soil conditioner that combines the dual functions of promoting root growth and improving soil structure. The preparation process is simple and inexpensive, enabling the high-value and resource-based utilization of agricultural waste, and producing a high-performance, multifunctional soil conditioner.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A biochar-based soil conditioner using agricultural waste as raw material, wherein the biochar-based soil conditioner is obtained by loading functional substances or biological agents onto agricultural waste after pyrolysis and carbonization. The functional substances are one or more of the following: indoleacetic acid, indoleacetic acid derivatives, indolebutyric acid, indolebutyric acid derivatives, naphthaleneacetic acid, naphthaleneacetic acid derivatives, gibberellin, brassinolide, and amino acid esters. The bacterial strains in the biological agent are one or more of the following: Bacillus subtilis, Bacillus megaterium, Bacillus mucilaginosus, Azotobacter chrysophyllariae, Pseudomonas fluorescens, Bacillus licheniformis, Bacillus cereus, Clostridium butyricum, Bacillus brevis, and Bacillus vesalivarius.

[0006] The volume of the functional substance aqueous solution is 0.5-2% of the dry weight of the biochar.

[0007] The biological agent is obtained by mixing biological strains with organic liquid, and the volume ratio of organic liquid to biological strains is 10:1-30:1.

[0008] The weight ratio of biological inoculant to biochar is 1:10-1:30.

[0009] The effective viable count of the biological agent is 2×10⁻⁶. 8 -1×10 9 CFU / mL or 2×10 8 -1×10 9 CFU / g.

[0010] The pyrolysis carbonization process involves heating agricultural waste to 160-180℃ and holding it at that temperature for 3-10 minutes. Then, under sealed conditions, the temperature is raised to 200-350℃ for pyrolysis carbonization for 15-30 minutes to obtain biochar.

[0011] The thermal expansion process at 160-180℃ for 3-10 minutes allows the air inside the reactor and the material to fully expand and be expelled, effectively reducing the air content inside the reactor and improving the carbonization quality and yield of organic materials.

[0012] Specifically, it could be: The crushed agricultural waste particles are placed in a reactor equipped with a ventilation valve. With the ventilation valve open, the container is heated to 160–180℃ and held at this temperature for 3–10 minutes. This holding time allows the air inside the reactor to fully absorb heat, expand, and be expelled from the container, making the air inside as rarefied as possible. After the holding time is completed, the ventilation valve is closed, and the temperature is continued to rise under sealed conditions. Once the temperature inside the container reaches the set carbonization temperature of 200–350℃, timing begins, and carbonization is carried out at a constant temperature for 15–30 minutes. Throughout the entire process of heating, carbonization, cooling, and loading, the reactor is continuously rotated at a speed of 3–15 rpm to ensure uniform carbonization of the material inside the container.

[0013] Medium-low temperature pyrolysis conditions of 200–350℃ can promote the moderate decomposition and condensation of organic macromolecules such as cellulose, hemicellulose, and lignin, forming biochar with rich porous structure and active functional groups, while avoiding over-carbonization caused by high temperatures, thus preserving its good adsorption performance and surface activity. Continuous rotation of the container and control of the ventilation valve are key operations to ensure the carbonization effect. Adjusting the holding time can ensure good carbonization of materials from different sources; excessive time can easily lead to over-carbonization, resulting in a decrease in carbon skeleton strength and energy waste.

[0014] When loading functional substances, an aqueous solution of the functional substances is sprayed onto the biochar at 90-130℃. Specifically, the material in the reactor is allowed to cool naturally. When the material temperature drops to 90-130℃, a liquid containing functional substances that promote crop growth is sprayed onto the biochar using a spraying device installed on the reactor. This ensures that the functional substances are evenly distributed on the surface and in the pores of the biochar and are fully adsorbed by the biochar. The process continues until the material temperature in the reactor drops below 80℃, at which point the biochar is transferred out of the reactor. If a powdered biochar-based soil amendment product is required, the transferred biochar can be directly cooled and bagged to obtain the finished product. If a granular soil structure amendment is to be prepared, the material can be directly fed into a granulation device after being discharged from the reactor to obtain a granular functional biochar-based soil amendment product.

[0015] The spray volume of the functional substance aqueous solution is 0.5-2% of the dry weight of the biochar, the spray time is 2-5 minutes, and the rotation speed of the biochar is 5-15 rpm during the spraying process; the reactor rotates continuously throughout the entire loading process.

[0016] Preferably, the spray volume of the functional substance aqueous solution is 1% of the dry weight of the biochar, the spraying time is 3 minutes, and the rotation speed of the biochar is 10 rpm during the spraying.

[0017] When loading bio-initiatives, organic liquid is sprayed onto the biochar at 80-130℃, and the bio-initiative is sprayed after the temperature drops to 35-40℃. Specifically, the material is allowed to cool naturally. When the material temperature inside the reactor drops to 80-130℃, organic liquid is sprayed onto the biochar using a spraying device installed on the reactor. The material continues to cool until the biochar temperature drops to 35-40℃. Then, a mixture of bio-initiatives and organic liquid is sprayed onto the rolling material through a spraying device inside the reactor. After spraying, the material continues to rotate and mix inside the reactor for 3-20 minutes. After mixing, the material is unloaded from the reactor and dried to obtain a bioactive biochar-based soil conditioner.

[0018] The organic liquid is molasses solution, sugar filter mud slurry, or corn slurry; the mass ratio of organic liquid to biochar is 1:10-1:20.

[0019] The biological agent is obtained by mixing biological strains with organic liquid, and the volume ratio of organic liquid to biological strains is 10:1-30:1.

[0020] The weight ratio of biological inoculant to biochar is 1:10-1:30.

[0021] The farmland waste is selected from one or more of the following: straw, rice husks, peanut shells, corn cobs, eggplant vines, chili vines, and farmland weeds.

[0022] A method for preparing a biochar-based soil conditioner using farmland waste as raw material involves carbonizing the crushed farmland waste at 200-350℃ for 15-30 minutes to obtain biochar. When the temperature drops to 90-130℃, an aqueous solution of functional substances is sprayed onto the biochar to obtain the biochar-based soil conditioner. Specifically, the crushed agricultural waste is placed in a reactor, heated to 160-180℃ and preheated at this temperature for 3-10 minutes to allow the air inside the reactor and the material to fully expand thermally. Then, the ventilation valve is closed, and the temperature is raised to 200-350℃ and maintained at this temperature for 15-30 minutes to complete the pyrolysis and carbonization. After carbonization, the material is allowed to cool naturally. When the temperature drops to 90-130℃, an aqueous solution of functional substances is sprayed onto the continuously rotating biochar, allowing the active substances to be fully adsorbed by the biochar and evenly distributed on its surface and in its pore structure. The material is rotated and mixed throughout the process. Once the temperature drops below 80℃, the biochar-based soil conditioner is obtained.

[0023] The spray volume of the functional substance aqueous solution is 0.5-2% of the dry weight of the biochar, and the spraying time is 2-5 minutes; the rotation speed of the biochar during the spraying is 5-15 rpm, and the reactor rotates continuously throughout the entire loading process.

[0024] Preferably, the spray volume of the functional substance aqueous solution is 1% of the dry weight of the biochar, the spraying time is 3 minutes, and the rotation speed of the biochar is 10 rpm during the spraying.

[0025] A method for preparing a biochar-based soil conditioner using agricultural waste as raw material: Crushed agricultural waste is placed in a reaction vessel and carbonized at a constant temperature of 200-350℃ for 15-30 minutes to obtain biochar; when the material temperature drops to 80-130℃, an organic liquid is sprayed onto the biochar; when the temperature drops to 35-40℃, a biological agent is sprayed onto the biochar to obtain the biochar-based soil conditioner. Specifically: the crushed agricultural waste is heated to 160-180℃ and preheated at a constant temperature for 3-10 minutes to allow the air in the reaction vessel to fully expand thermally; then the ventilation valve is closed, and the temperature is further increased to 200-350℃ and maintained at a constant temperature for 15-30 minutes to complete the carbonization. After carbonization, the material is allowed to cool down naturally. When the temperature drops to 80-130℃, organic liquid is sprayed onto the continuously rotating biochar. When the temperature of the biochar drops to 35-40℃, biological agents are sprayed onto the continuously rotating biochar to obtain the biochar-based soil conditioner.

[0026] Agricultural waste crushing pretreatment: Collect agricultural waste, remove impurities such as stones, metals, and plastics mixed in, crush the agricultural waste to 3-10 mm, reduce the particle size of the material, increase the specific surface area of ​​the material, promote the uniformity of the subsequent pyrolysis reaction, shorten the pyrolysis time, and facilitate the full mixing of materials when the material rotates in the reactor.

[0027] The reaction vessel used above is a commercially available product and is considered a conventional technology. The reaction vessel is equipped with a venting valve, which connects to the external atmospheric pressure environment when opened. The reaction vessel is also equipped with a spraying device.

[0028] An application of the biochar-based soil conditioner made from agricultural waste, wherein the biochar-based soil conditioner is used to prepare a biochar-based soil structure conditioner with dual functions of promoting root growth and improving soil structure.

[0029] The beneficial effects of this invention are: Resource-efficient utilization and environmental friendliness: This invention uses agricultural waste as the main raw material to realize the high-value recycling of agricultural by-products, effectively reducing environmental pollution caused by incineration or waste, and conforming to the development concept of green, low-carbon and circular agriculture.

[0030] The biochar produced is of excellent quality: by controlling the particle size of the raw materials and using medium-low temperature (200–350℃) pyrolysis and rotary mixing processes, the biochar has a well-developed pore structure and a large specific surface area (>150m²). 2It contains 100 g of ...

[0031] Multifunctional synergistic effect: During the cooling stage, functional substances or biological agents are loaded in situ, and the high adsorption capacity of biochar is used to achieve efficient immobilization and slow release of active ingredients. The resulting product has the dual functions of soil structure improvement and root growth promotion, which can significantly increase crop root length, root surface area, root volume and lateral root number, improve water and nutrient absorption efficiency, and ultimately promote crop yield.

[0032] The process is simple and controllable, and easy to industrialize: the production process does not require nitrogen protection, the overall preparation process is clear, and it only includes core steps such as crushing, rotary pyrolysis, and cooling spraying. The equipment requirements are not high, the operation is simple, the parameters are easy to adjust, and it has good prospects for industrial promotion.

[0033] Resource recycling: Achieving efficient resource utilization of agricultural waste and reducing environmental pollution.

[0034] Low energy consumption and low cost: No nitrogen or other inert gas protection is required during production. It is a medium-temperature pyrolysis process with low energy consumption and a wide range of inexpensive raw materials.

[0035] Functional Complexity: The product combines the physical structure improvement function of biochar with the function of promoting the biological regulation of crop roots, which can improve soil fertility and improve the micro-ecological environment.

[0036] Process stability: Gradient cooling and drum spraying technology ensure the integrity of the biochar structure and uniform loading of bioactive substances or microbial agents, resulting in stable product quality. Detailed Implementation

[0037] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0038] Unless otherwise specified, the raw materials, strains, and reagents used in the embodiments of this invention are all commercially available. The reaction vessel used in the embodiments of this invention is a commercially available product and is considered conventional technology. The reaction vessel is equipped with a venting valve, which connects to the external atmospheric pressure environment when opened. A spraying device is installed inside the reaction vessel.

[0039] Example 1 Bio-activated biochar-based soil amendment products prepared from corn stalks (1) Raw material pretreatment: Collect dry corn stalks, remove impurities such as stones, metals, and plastics mixed in, and crush them to a particle size of about 5mm using a crusher.

[0040] (2) Pyrolysis and carbonization: The crushed corn stalks are placed in the reactor (10 rpm) and heated with the air exchange valve open. When the material temperature rises to 180℃, heating is stopped and the temperature is kept for 5 minutes. Then the air exchange valve is closed and heating is continued. When the material temperature reaches 320℃, constant temperature carbonization is carried out for 25 minutes. Finally, heating is stopped and the material is allowed to cool down naturally.

[0041] A carbonization temperature of 320℃ promotes the appropriate decomposition and condensation of organic macromolecules such as cellulose, hemicellulose, and lignin, forming biochar with abundant porous structures and active functional groups. It also avoids over-carbonization caused by high temperatures, thus preserving its good adsorption properties and surface activity. The continuous rotation and thermal expansion of the reactor are crucial for ensuring effective carbonization. Adjusting the holding time allows materials from different sources to achieve good carbonization results; however, excessive time can easily lead to over-carbonization, resulting in decreased carbon skeleton strength and energy waste.

[0042] (3) Loading of biological agents: When the temperature drops to 180℃, open the ventilation valve. When the temperature drops to 100℃, use the spray device in the reactor to spray molasses solution onto the rolling material. The ratio of molasses solution to biochar is 1:10. After spraying, wait for the material temperature to drop to 40℃, and then spray biological agents onto the rolling material through the spray device in the reactor. After spraying, the material is continuously rotated and mixed in the reactor for 5 minutes. Then, the material is unloaded, spread out, and naturally dried in a cool and ventilated place (controlling the material moisture content <15%). Finally, a bioactive biochar-based soil amendment product is obtained.

[0043] The preparation method of the biological agent is as follows: Bacillus subtilis (Henan Jiubang Biotechnology Co., Ltd.) and Bacillus vesiculosus (Shandong Lvlong Biotechnology Co., Ltd.) are mixed in a 1:1 ratio, and molasses solution is added (molasses solution to agent volume ratio 15:1). The mixture is stirred evenly to obtain the biological agent. The effective viable count of the biological agent is 9.8 × 10⁻⁶. 8 CFU / mL.

[0044] The continuous rotation of the reactor ensures that the biochar material is mixed evenly. Combined with the microbial agent carrier spraying process, the molasses solution can enhance the adhesion of the microbial agent to the surface of the biochar and provide a carbon source for the microorganisms, effectively improving the survival efficiency of the microbial agent. Compared with the traditional impregnation method, the survival rate can be increased by 25%.

[0045] Example 2 Using a mixture of rice husks and peanut shells as raw materials (1) Raw material pretreatment: Take dried rice husks and peanut shells and mix them in a mass ratio of 1:1. Remove impurities such as stones, metals and plastics, and crush them to a particle size of about 5 mm using a pulverizer.

[0046] (2) Pyrolysis and carbonization: Place the crushed rice husks and peanut shells mixture into the reactor, set the reactor speed to 15 rpm, and heat with the air exchange valve open. When the material temperature rises to 160℃, stop heating and keep it warm for 3 minutes, then close the air exchange valve and continue heating. When the material temperature reaches 210℃, carbonize at a constant temperature for 20 minutes, then stop heating and allow the material to cool down naturally.

[0047] (3) Bio-agent loading: When the temperature drops to 180℃, open the ventilation valve. When the material temperature drops to 110℃, turn on the reactor spraying device and spray sugar filter mud slurry onto the rolling material. The mass ratio of sugar filter mud slurry to biochar is 1:20. After spraying, when the material temperature drops to 40℃, spray the bio-agent onto the rolling material again through the spraying device. After spraying, the material is continuously rotated and mixed in the reactor for 5 minutes before being unloaded. Spread the material in a cool and ventilated place to air dry naturally, controlling the moisture content to <15%, to obtain a biochar-based soil amendment product with biological activity.

[0048] The preparation method of the biological agent is as follows: Bacillus megaterium (Guangxi Nongbao Bioengineering Co., Ltd.), Pseudomonas fluorescens (Shandong Huimin Zhonglian Biotechnology Co., Ltd.), and Bacillus belyssus (Shandong Lvlong Biotechnology Co., Ltd.) are mixed at a volume ratio of 2:1:1, and then added to sugar filter mud slurry (sugar filter mud slurry to agent volume ratio 20:1). The mixture is stirred until homogeneous to obtain the biological agent. The effective viable count of the biological agent is 9.3 × 10⁻⁶. 8 CFU / mL.

[0049] Example 3 Using a mixture of chili pepper vines and eggplant vines as raw materials (1) Raw material pretreatment: Take a mixture of dried chili pepper seedlings and eggplant seedlings (chili pepper seedlings: eggplant seedlings = 1:1), remove impurities such as stones, metals, and plastics from the material, and crush it to a particle size of about 7mm using a crusher for later use.

[0050] (2) Pyrolysis and carbonization: Place the crushed mixture of chili seedlings and eggplant seedlings into the reactor (13 rpm), heat with the air exchange valve open, and stop heating when the temperature reaches 180°C. Keep the temperature for 5 minutes, then close the air exchange valve and continue heating. When the material temperature reaches 330°C, carbonize at a constant temperature for 30 minutes. After carbonization, stop heating and allow the material to cool down naturally.

[0051] (3) Loading of biological agent: When the temperature drops to 180℃, open the ventilation valve. When the material temperature drops to 120℃, spray corn slurry onto the continuously rolling biochar through the spraying device of the reactor. The ratio of corn slurry to biochar is 1:15. After spraying, when the material temperature drops to 40℃, spray biological agent onto the rolling material again. After spraying, the reactor continues to rotate and mix for 5 minutes, and then unloads the material. Spread the unloaded material out and let it air dry naturally in a cool and ventilated place, controlling the moisture content to <15%, to obtain a biologically activated biochar-based soil amendment product.

[0052] The preparation of the biological agent shown is as follows: Bacillus subtilis (Henan Jiubang Biotechnology Co., Ltd.) and Bacillus vesiculosus (Shandong Lvlong Biotechnology Co., Ltd.) were mixed in a 1:1 ratio, and corn slurry was added (the volume ratio of corn slurry to the agent was 28:1). The mixture was stirred evenly to obtain the biological agent. The effective viable count of the biological agent was 5.1 × 10⁻⁶. 8 CFU / mL.

[0053] Example 4 Using a mixture of chili seedlings, corn cobs, and farmland weeds as raw materials (1) Raw material pretreatment: Take a mixture of dried chili seedlings, corn cobs and farmland weeds (chili seedlings: corn cobs: farmland weeds = 1:1:1), remove impurities such as stones, metals and plastics mixed in, and crush them to a particle size of about 7mm with a pulverizer for later use.

[0054] (2) Pyrolysis and carbonization: Place the crushed chili seedlings, corn cobs and farmland weeds into the reactor, heat with the air exchange valve open, and stop heating when the temperature reaches 170°C. Keep the temperature for 5 minutes, then close the air exchange valve and continue heating. When the material temperature reaches 260°C, carbonize at a constant temperature for 30 minutes. After carbonization, stop heating and allow the material to cool down naturally.

[0055] (3) Loading of biological agents: When the temperature drops to 180℃, open the ventilation valve. When the material cools down to 100℃, use the spray device of the reactor to spray a mixture of molasses liquid and corn slurry (molasses liquid: corn slurry = 1:1) onto the rolling material. The ratio of the mixture to biochar is 1:25. After spraying, continue to rotate and cool down. When the material temperature drops to 40℃, spray biological agents again. After spraying, the material continues to rotate and mix in the reactor for 5 minutes. Then unload the material, spread it out, and let it air dry in a cool and ventilated place. Control the moisture content to <15% to obtain a biochar-based soil amendment product with biological activity.

[0056] Biological inoculant: A mixture of *Bacillus megaterium* (Guangxi Nongbao Bioengineering Co., Ltd.) and *Bacillus licheniformis* (Shandong Dehe Mingxing Biotechnology Co., Ltd.) at a 2:1 ratio was prepared. Molasses solution and corn syrup were then uniformly mixed with the inoculant at a ratio of 14:14:1 to obtain the biological inoculant. The effective viable count of the biological inoculant was 6.7 × 10⁻⁶. 8 CFU / mL.

[0057] Example 5 (1) Raw material pretreatment: Collect wheat straw, corn straw and corn cob, remove impurities such as stones, metals and plastics, mix them in a mass ratio of 1:1:1 and then crush them to a particle size of 8mm.

[0058] (2) Pyrolysis and carbonization: Add the crushed material to the reactor (15 rpm), heat with the air valve open, and stop heating when the temperature rises to 170°C. Maintain the temperature for 3 minutes, then close the air valve and continue heating. When the system temperature rises to 350°C, carbonize at a constant temperature for 30 minutes. After carbonization, stop heating and allow the material to cool down naturally.

[0059] (3) Functional material loading: When the temperature drops to 180℃, open the ventilation valve. When the temperature of the material inside the reactor drops to 120℃, spray an aqueous solution containing 0.5% naphthaleneacetic acid, 0.1% indoleacetic acid, and 0.05% gibberellin onto the surface of the material through the spraying device inside the reactor. The spraying volume is 1% of the dry weight of the biochar, and the spraying time is 3 minutes. During the spraying, the reactor is continuously rotated at a speed of 10 rpm. After the spraying is completed, the reactor continues to rotate until the material temperature drops to 80℃, at which point the material is unloaded. Open the reactor and unload the material to obtain the biochar-based soil conditioner.

[0060] Spraying is chosen during the cooling phase, when the biochar still maintains a relatively high temperature. The biochar's pores are open and its surface activity is strong. The groups on the surface of the large organic molecules produced during the carbonization process can generate efficient adsorption and complexation with functional substances, which is beneficial to enhancing the adsorption of functional substances by the biochar. As the biochar cools and shrinks, the functional substances can be more firmly fixed in its internal structure, reducing the loss of functional substances, improving load stability, and allowing the functional substances to be preserved in an effective state in the biochar for a long time, achieving continuous release in the soil.

[0061] If producing powdered soil conditioner, the material can be bagged after cooling. If producing granular biochar-based soil conditioner, the material can be directly fed into granulation equipment after being discharged from the reactor to obtain granulated functional biochar-based soil conditioner. Depending on the application requirements, the product can undergo subsequent processing such as sieving, drying, or packaging. This product has the dual functions of promoting root growth and improving soil, effectively mitigating the adverse effects of soil structure degradation on plant root growth, and simultaneously increasing crop yield.

[0062] Example 6 (1) Raw material pretreatment: Collect rice straw, rice husk and corn straw, remove impurities such as stones, metals and plastics mixed in them, mix them in a mass ratio of 1:2:1 and crush them to 5mm.

[0063] (2) Pyrolysis and carbonization: Add the crushed mixture to the reactor (10 rpm). Heat with the air exchange valve open. When the temperature rises to 170°C, keep it at that temperature for 3 minutes. Then close the air exchange valve and continue heating. When the temperature rises to 300°C, carbonize at that temperature for 20 minutes. After carbonization, stop heating and allow the material to cool down naturally.

[0064] (3) Functional substance loading: When the temperature drops to 180℃, open the ventilation valve. When the temperature of the material inside the reactor drops to 130℃, spray the material surface with a solution containing 0.7% indole glycoside derivatives, 0.1% amino esters, and 0.05% naphthaleneacetic acid through the spraying device inside the reactor. The spraying amount is 1.5% of the dry weight of the biochar, and the spraying time is 5 minutes. During the spraying, the reactor is continuously rotated at a speed of 5 rpm. After the spraying is completed, the reactor continues to rotate until the material temperature drops to 80℃, at which point the material is unloaded. Open the reactor and remove the material to obtain the biochar-based soil conditioner.

[0065] Example 7 (1) Raw material pretreatment: Collect waste materials such as chili seedlings and eggplant seedlings, remove impurities such as stones, metals and plastics mixed in them, mix them at a mass ratio of 1:1 and then crush them to 8mm.

[0066] (2) Pyrolysis carbonization: Add the crushed material to the reactor (5 rpm), heat with the air valve open, stop heating when the temperature rises to 180℃, keep it warm for 5 minutes, then close the air valve and continue heating. When the system temperature rises to 330℃, carbonize at a constant temperature for 30 minutes; stop heating after carbonization and allow the material to cool down naturally.

[0067] (3) Functional material loading: When the temperature drops to 180℃, open the ventilation valve. When the temperature of the material inside the reactor drops to 130℃, spray a mixture containing 0.15% indolebutyric acid, 0.01% brassinolide, 0.05% indoleacetic acid, and 0.1% naphthaleneacetic acid through the nozzles inside the reactor. The spray volume is 0.5% of the dry weight of the biochar, and the spraying time is 3 minutes. During the spraying, the reactor is continuously rotated at a speed of 8 rpm. After the spraying is completed, the reactor continues to rotate until the material temperature drops to 80℃, at which point the material is unloaded. Open the reactor and remove the material to obtain the biochar-based soil conditioner.

[0068] Comparative Example 1 The biochar obtained by pyrolysis carbonization in step (2) of Example 1 was used as the biochar control sample.

[0069] Bio-activated biochar-based soil amendment products prepared from corn stalks (1) Raw material pretreatment: Collect dry corn stalks, remove impurities such as stones, metals, and plastics mixed in, and crush them to a particle size of about 5mm using a crusher.

[0070] (2) Pyrolysis and carbonization: The crushed corn stalks were placed in the reactor (10 rpm). The reactor was heated with the ventilation valve open. When the temperature reached 180°C, the heating was stopped and the temperature was maintained for 5 minutes. Then the ventilation valve was closed and the heating was continued. When the material temperature reached 320°C, the material temperature was maintained at 320°C for about 25 minutes. Then the heating was stopped and the material was allowed to cool down naturally. The sample of Comparative Example 1 was obtained.

[0071] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that after the material temperature in the pyrolysis and carbonization step is raised to 180°C, no heat preservation is performed; the material is directly heated to the carbonization temperature. This is used to observe the effect of thermal expansion on the product effect. Specifically: (1) Raw material pretreatment: Take dry corn stalks and crush them to a particle size of about 5 mm using a crusher.

[0072] (2) Pyrolysis and carbonization: The crushed corn stalks are placed in the reactor (10 rpm). The heat is carried out with the air exchange valve open. When the material temperature rises to 180°C, the air exchange valve is closed. The heating continues. When the material temperature rises to 320°C, the material temperature is maintained at 320°C for about 25 minutes. Then the heating is stopped and the material is allowed to cool down naturally.

[0073] (3) Loading of biological agent: When the temperature drops to 180℃, open the ventilation valve. When the material temperature drops to 100℃, use the spray device in the reactor to spray molasses solution onto the rolling material. The ratio of molasses solution to biochar is 1:10. After spraying, when the material temperature drops to 40℃, spray biological agent onto the rolling material through the spray device in the reactor. After spraying, the material is continuously rotated and mixed in the reactor for 5 minutes. Then, the material is unloaded, spread out, and naturally dried in a cool and ventilated place (controlling the material moisture content <15%). Finally, a bioactive biochar-based soil amendment product is obtained.

[0074] The biological agent is the same as in Example 1.

[0075] Comparative Example 3 The difference between Comparative Example 3 and Example 5 is that after the material temperature in the pyrolysis and carbonization step is raised to 170°C, no heat preservation is performed; the material is directly heated to the carbonization temperature. This is used to observe the effect of thermal expansion on the product effect. Specifically: (1) Raw material pretreatment: Collect wheat straw, corn straw and corn cob, remove impurities such as stones, metals and plastics, mix them in a mass ratio of 1:1:1 and then crush them to a particle size of 8mm.

[0076] (2) Pyrolysis carbonization: Add the crushed material to the reactor (15 rpm), heat with the air exchange valve open, and when the temperature rises to 170℃, close the air exchange valve and continue to heat up. When the system temperature rises to 350℃, carbonize at a constant temperature for 30 minutes. After carbonization, stop heating and allow the material to cool down naturally.

[0077] (3) Functional material loading: When the temperature drops to 180℃, open the ventilation valve. When the temperature inside the reactor drops to 120℃, spray an aqueous solution containing 0.5% naphthaleneacetic acid, 0.1% indoleacetic acid, and 0.05% gibberellin onto the rotating biochar through the spraying device inside the reactor. The spraying volume is 1% of the dry weight of the biochar, and the spraying time is 3 minutes. During the spraying, the reactor continues to rotate at a speed of 10 rpm. After the spraying is completed, continue to rotate until the material temperature drops to 80℃, then unload the material. Open the reactor and unload the material to obtain the biochar-based soil conditioner.

[0078] Application examples The powdered samples obtained from Examples 1, 2, 3, 4, 5, 6, 7 and Comparative Examples 1-3 were used in a field trial in Hulin, Jiamusi City, Heilongjiang Province, with maize as the crop. The application rate was 200 kg / mu, and maize was planted for one season. The experimental protocol is shown in Table 1, and the results are shown in Tables 2-6. The blended fertilizer (26-10-12) with a nutrient content of 48% was produced by Heilongjiang Beifeng Agricultural Production Materials Group Co., Ltd., which increased the number of beneficial bacteria in the soil by 2-3 orders of magnitude.

[0079] Corn was sown on April 28, 2025, with a row spacing of 55 cm, a plant spacing of 25 cm, a sowing depth of 4-5 cm, and single-seed sowing at a rate of 4850 seeds / mu. At sowing, 50 kg / mu of blended fertilizer (NPK: 26-10-12) was applied. Before sowing, corn seeds were coated with 300 ml / 100 kg of 10% chlorantraniliprole seed treatment suspension to control corn smut and stalk rot. On June 26, 2025, 5 ml / mu of 200 g / L chlorantraniliprole suspension was applied as a spray to control corn borers. The corn was harvested and yield measured on October 5, 2025.

[0080] Table 1

[0081] Table 2. Maize yield under different treatments

[0082] Table 3. Soil bulk density under different treatments

[0083] Table 4. Maize plant height at harvest time under different treatments

[0084] Table 5. Maize stalk diameter at harvest time under different treatments

[0085] Table 6. Relationship between maize root system and aboveground parts at harvest.

[0086] As shown in Tables 1-6, compared with the blank control, all different biochar treatments improved maize yield, plant height, stem diameter, and root-to-shoot ratio to some extent, and reduced soil bulk density to a certain degree. Compared with Comparative Example 1, the addition of bioactive substances and microbial agents effectively increased maize yield, plant height, stem diameter, and root-to-shoot ratio, and the improvement effect on soil bulk density was also more significant. Compared with Control Examples 2 and 3, it is shown that adding a thermal expansion process during biochar preparation can effectively enhance the promotion of maize growth and the improvement effect on soil bulk density of biochar products. This invention uses low-temperature thermal expansion and medium-low temperature carbonization processes, which reduces energy consumption and eliminates the need for inert gases, greatly reducing the cost of biochar preparation and possessing high economic and social value.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A biochar-based soil conditioner using agricultural waste as raw material, characterized in that: The biochar-based soil conditioner is obtained by loading functional substances or biological agents onto agricultural waste after pyrolysis and carbonization. The functional substances are one or more of the following: indoleacetic acid, indoleacetic acid derivatives, indolebutyric acid, indolebutyric acid derivatives, naphthaleneacetic acid, naphthaleneacetic acid derivatives, gibberellin, brassinolide, and amino acid esters. The bacterial strains in the biological agent are one or more of the following: Bacillus subtilis, Bacillus megaterium, Bacillus mucilaginosus, Azotobacter chrysophyllariae, Pseudomonas fluorescens, Bacillus licheniformis, Bacillus cereus, Clostridium butyricum, Bacillus brevis, and Bacillus vesalivarius.

2. The biochar-based soil conditioner using agricultural waste as raw material according to claim 1, characterized in that, The pyrolysis carbonization process is as follows: agricultural waste is heated to 160-180℃ and kept at that temperature for 3-10 minutes. Then, under sealed conditions, the temperature is raised to 200-350℃ for pyrolysis carbonization for 15-30 minutes to obtain biochar.

3. The biochar-based soil conditioner using agricultural waste as raw material according to claim 1, characterized in that: When loading functional substances, spray the functional substance aqueous solution onto the biochar at 90-130℃.

4. The biochar-based soil conditioner using agricultural waste as raw material according to claim 1, characterized in that: When loading biological agents, first spray organic liquid onto biochar at 80-130℃, and then spray biological agents after the system temperature drops to 35-40℃.

5. The biochar-based soil conditioner using agricultural waste as raw material according to claim 1, characterized in that: The farmland waste is selected from one or more of the following: straw, rice husks, peanut shells, corn cobs, eggplant vines, chili vines, and farmland weeds.

6. A method for preparing a biochar-based soil conditioner using agricultural waste as raw material as described in claim 3 or 4, characterized in that: The crushed agricultural waste is pyrolyzed and carbonized to obtain biochar. When the temperature drops to 90-130℃, an aqueous solution of functional substances is sprayed onto the biochar to prepare a biochar-based soil conditioner. The crushed farmland waste is pyrolyzed and carbonized to obtain biochar. When the temperature drops to 80-130℃, organic liquid is sprayed onto the biochar. When the temperature drops to 35-40℃, biological agent is sprayed onto the biochar to obtain a biochar-based soil conditioner.

7. The method for preparing a biochar-based soil conditioner using agricultural waste as raw material according to claim 6, characterized in that: The spray volume of the functional substance aqueous solution is 0.5-2% of the dry weight of biochar, and the spraying time is 2-5 minutes; during the spraying process, the stirring speed of the biochar is 5-15 rpm.

8. The method for preparing a biochar-based soil conditioner using agricultural waste as raw material according to claim 6, characterized in that: The organic liquid is molasses solution, sugar filter mud slurry, or corn slurry; the mass ratio of organic liquid to biochar is 1:10-1:

20.

9. The method for preparing a biochar-based soil conditioner using agricultural waste as raw material according to claim 6, characterized in that: The biological agent is obtained by mixing biological strains with organic liquid, and the volume ratio of organic liquid to biological strains is 10:1-30:

1.

10. The application of the biochar-based soil conditioner using agricultural waste as raw material as described in claim 1, characterized in that: The biochar-based soil conditioner is used to prepare a biochar-based soil structure conditioner with dual functions of promoting root growth and improving soil structure.

Images