Improvement method for improving carbon sequestration capability of biochar

Abstract

The invention relates to an improvement method for improving the carbon sequestration capability of biochar, and the improvement method comprises the following steps: S100: obtaining biochar to be improved, the particle size range of the biochar being 0.15-0.5 mm; s200, the water content of the biochar is adjusted to 100% of the maximum water-holding capacity with water, and water-saturated biochar is obtained; s300, the water-saturated biochar obtained in the step S200 is subjected to the following treatment: treatment A, wherein the water-saturated biochar is subjected to humid culture and then is subjected to drying treatment; or treatment B: freezing the water-saturated biochar, and then carrying out unfreezing treatment; and S400, repeating the step S200 and the step S300 for at least 25 rounds, and then drying and storing the repeatedly treated biochar to obtain the improved biochar with improved carbon sequestration capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of biochar carbon fixation, and in particular to an improved method for improving the carbon fixation capacity of biochar. Background Art

[0002] Climate change has brought severe challenges to countries around the world. The sixth assessment report of the Intergovernmental Panel on Climate Change (IPCC) of the United Nations shows that the volume fractions of the three major greenhouse gases, CO2, CH4 and N2O, in the atmosphere have reached 4.10×10 -4 , 1.87×10 -6 and 3.32×10 -7 In 2020, my country proposed the goals of carbon peak and carbon neutrality. Deploying carbon capture, utilization and storage projects is one of the important ways to achieve "carbon neutrality".

[0003] Different from traditional carbon capture, utilization and storage technologies, biochar has lower requirements in terms of technical threshold, resource consumption, economic cost, etc., and is a more easily implemented carbon sequestration and emission reduction approach. A large number of studies have shown that biochar has great potential in carbon sequestration and emission reduction and climate change mitigation. Biochar is a carbon-rich solid product obtained by pyrolysis of biomass under anaerobic or anoxic conditions. It has the characteristics of high degree of aromatization, developed pore structure, rich surface functional groups, and high content of mineral nutrients. After biochar is applied to the soil, on the one hand, it can fix its own carbon in the soil and increase the soil carbon sink function, and on the other hand, it can improve the physical and chemical properties of the soil and play a role in increasing crop yields. However, in recent years, studies have found that biochar entering the field will inevitably age after being subjected to long-term effects of external environmental factors such as rainfall, ultraviolet light, and seasonal freezing and thawing, resulting in changes in its own structure and affecting its carbon sequestration potential. Therefore, it is very necessary to develop improved methods to improve the carbon sequestration capacity of biochar, optimize its microstructure and components, and provide technical support for the use of biochar for long-term carbon sequestration. Summary of the invention

[0004] In view of the above analysis, an embodiment of the present invention aims to provide an improved method for improving the carbon fixation capacity of biochar, so as to solve at least one of the above problems.

[0005] The present invention provides an improved method for improving the carbon fixation capacity of biochar, comprising the following steps:

[0006] S100: obtaining biochar to be improved, wherein the particle size of the biochar is in the range of 0.15 to 0.5 mm;

[0007] S200: adjusting the water content of the biochar to 100% of the maximum water holding capacity with water to obtain water-saturated biochar;

[0008] S300: The water-saturated biochar obtained in S200 is subjected to the following treatments:

[0009] Treatment A: the water-saturated biochar is wet cultured and then dried;

[0010] or,

[0011] Treatment B: freezing the water-saturated biochar and then thawing it;

[0012] S400: Repeat step S200 and step S300 for at least 25 rounds, and then dry and store the repeatedly treated biochar to obtain improved biochar with improved carbon fixation capacity.

[0013] Further, according to the selection of processing methods of step S300 in different rounds, the following situations can be classified:

[0014] Case 1: Choose treatment A every time;

[0015] Case 2: Choose treatment B every time;

[0016] Case 3: Process A or Process B is selected each time, that is, Process A is selected in some rounds and Process B is selected in the remaining rounds.

[0017] Furthermore, in the treatment A, the time ratio of wet culture to dry treatment is 2:1, the temperature of wet culture is 20-25°C, and the temperature of dry treatment is 55-65°C.

[0018] Furthermore, the duration of moist culture is 14 to 16 h;

[0019] The drying time is 8 to 10 hours.

[0020] Furthermore, in the treatment B, the time ratio of the freezing treatment to the thawing treatment is 2:1, the temperature of the freezing treatment is -12 to -18°C, and the temperature of the thawing treatment is 20 to 25°C.

[0021] Furthermore, the duration of the freezing treatment is 14 to 16 h;

[0022] The thawing process takes 8 to 10 hours.

[0023] Furthermore, in step S100, the method for preparing biochar comprises the following steps:

[0024] S101: Obtain biomass raw materials;

[0025] S102: After air-drying the biomass raw material, heat it in an oxygen-free atmosphere at a temperature below 500° C. for 10 hours, then cool it to room temperature, take out the biochar, crush it, and grind it to make the particle size of the biochar particles 0.15 to 0.5 mm.

[0026] Furthermore, the water content of the biomass raw material after air drying is less than 5%, and the biomass raw material is cut into small segments of 8 to 12 cm after air drying.

[0027] Furthermore, the carbonization process in step S102 is implemented in a carbonization furnace, and the carbonization furnace is raised to the final target temperature at a rate of 7-12° C. / min and then maintained for at least 10 hours.

[0028] Furthermore, in step S200, the water used for adjustment is deionized water.

[0029] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0030] (1) The present invention can improve the thermal stability of biochar, and its stability and carbon sequestration potential level are improved, so that it can play a greater potential in carbon sequestration and climate change mitigation;

[0031] (2) In terms of soil remediation, the biochar improved by the present invention can adsorb a variety of pollutants due to its porous structure. At the same time, it can change the form of pollutants by adjusting the pH of the soil to a certain extent, thereby reducing the harm of pollution. In terms of soil improvement, it can provide many necessary elements for the soil to a certain extent, improve the health of the soil, and have a positive effect on the growth and development of soil crops.

[0032] (3) The present invention increases the number of mesopores in biochar, thereby increasing its specific surface area. The increase in specific surface area can better promote its adsorption of pollutants and can better serve as a soil conditioner, playing a role in improving soil fertility, improving soil structure, and promoting microbial diversity. At the same time, it can play a certain role in reducing greenhouse gas emissions, especially reducing N2O;

[0033] (4) The biochar used in the present invention uses biomass raw materials such as crop straw, which are easily available and have low acquisition costs. The preparation process is mature and easy to operate, and can be used after large-scale production. The overall use cost is low and has a high degree of practical application possibility.

[0034] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0036] Figure 1 The thermogravimetric-differential thermogravimetric curves of biochar before and after improvement in a specific embodiment;

[0037] Figure 2 is the stability coefficient R of the biochar before and after improvement in a specific embodiment 50 Histogram;

[0038] Figure 3 It is the BJH pore size distribution diagram of biochar before and after improvement in a specific implementation method. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0040] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the term "connected" should be understood in a broad sense, for example, it can be a fixed connection, or a detachable connection, or an integral connection, which can be a mechanical connection, or an electrical connection, which can be a direct connection, or can be indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] The terms "top", "bottom", "above", "lower", and "on" used throughout the description are relative to the relative positions of components of a device, such as the relative positions of the top and bottom substrates within a device. It is understood that devices are multifunctional regardless of their orientation in space.

[0042] The common working surface of the present invention can be a plane or a curved surface, can be inclined, or can be horizontal. For the convenience of description, the embodiment of the present invention is placed on a horizontal plane and used on the horizontal plane, and "high and low" and "up and down" are defined in this way.

[0043] A specific embodiment of the present invention discloses an improved method for improving the carbon fixation capacity of biochar, comprising the following steps:

[0044] S100: obtaining biochar to be improved, wherein the particle size of the biochar is in the range of 0.15 to 0.5 mm;

[0045] S200: adjusting the water content of the biochar to 100% of the maximum water holding capacity with water to obtain water-saturated biochar;

[0046] S300: The water-saturated biochar obtained in S200 is subjected to the following treatments:

[0047] Treatment A: the water-saturated biochar is wet cultured and then dried;

[0048] or,

[0049] Treatment B: freezing the water-saturated biochar and then thawing it;

[0050] S400: Repeat step S200 and step S300 for at least 25 rounds, and then dry and store the repeatedly treated biochar to obtain improved biochar with improved carbon fixation capacity.

[0051] The biochar improved by the present invention can not only improve its carbon fixation capacity, but also cooperate with the repair and improvement efficiency of the biochar itself, becoming an effective way to recycle agricultural and forestry wastes.

[0052] It should be noted that the biochar is processed through step S200 and step S300 as a complete round, that is, after the round, the biochar is processed through step S300.

[0053] According to the selection of the processing method of step S300 in different rounds, it can be divided into the following situations:

[0054] Case 1: Choose treatment A every time;

[0055] Case 2: Choose treatment B every time;

[0056] Case 3: Process A or process B is selected each time, that is, process A is selected in some rounds, and process B is selected in the remaining rounds. Preferably, process A or process B appears alternately, and regular or irregular interleaving may be adopted.

[0057] When the improved method is situation 1, it comprises the following steps:

[0058] S100: obtaining biochar to be improved, wherein the particle size of the biochar is in the range of 0.15 to 0.5 mm;

[0059] S200: adjusting the water content of the biochar to 100% of the maximum water holding capacity with water to obtain water-saturated biochar;

[0060] S300: wet culturing the water-saturated biochar, and then drying it;

[0061] S400: Repeat step S200 and step S300 for at least 25 rounds, and then dry and store the repeatedly treated biochar to obtain improved biochar with improved carbon fixation capacity.

[0062] When the improved method is situation 2, it includes the following steps:

[0063] S100: obtaining biochar to be improved, wherein the particle size of the biochar is in the range of 0.15 to 0.5 mm;

[0064] S200: adjusting the water content of the biochar to 100% of the maximum water holding capacity with water to obtain water-saturated biochar;

[0065] S300: freezing the water-saturated biochar and then thawing it;

[0066] S400: Repeat step S200 and step S300 for at least 25 rounds, and then dry and store the repeatedly treated biochar to obtain improved biochar with improved carbon fixation capacity.

[0067] When the improved method is situation three, it includes the following steps:

[0068] S100: obtaining biochar to be improved, wherein the particle size of the biochar is in the range of 0.15 to 0.5 mm;

[0069] S200: adjusting the water content of the biochar to 100% of the maximum water holding capacity with water, and maintaining it for 1 to 2 hours to obtain water-saturated biochar;

[0070] S300: The water-saturated biochar obtained in S200 is subjected to the following treatments:

[0071] Treatment A: the water-saturated biochar is wet cultured and then dried;

[0072] or,

[0073] Treatment B: freezing the water-saturated biochar and then thawing it;

[0074] S400: Repeat step S200 and step S300 for at least 25 rounds, and use treatment A for at least some of the rounds and treatment B for other parts of the rounds, and then dry and store the repeatedly treated biochar to obtain improved biochar with improved carbon fixation capacity.

[0075] According to a preferred embodiment of the present invention, in step S100, the method for preparing biochar comprises the following steps:

[0076] S101: Obtain biomass raw materials;

[0077] S102: After air-drying the biomass raw material, heat it in an oxygen-free atmosphere at a temperature below 500° C. for 10 hours, and then cool it to room temperature. Take out the biochar, crush it, and grind it to make the particle size of the biochar particles 0.15 to 0.5 mm.

[0078] The biomass raw material is preferably agricultural crop raw materials such as wheat straw or corn straw, which are easily available and have low acquisition costs and good effects.

[0079] The air drying can be natural air drying, and the water content after air drying is less than 5%. After air drying, the biomass raw material is cut into small pieces of about 8 to 12 cm.

[0080] The air-dried cut biomass raw materials are placed in a carbonization furnace for carbonization, and nitrogen is flushed into the carbonization furnace to form an oxygen-free environment. The biomass raw materials are placed in a carbonization furnace for carbonization, and the carbonization furnace is an inert atmosphere formed by nitrogen, argon, carbon dioxide, etc. to ensure that the preparation process is in an oxygen-free environment. Preferably, the nitrogen atmosphere flow rate is 0.4-0.5L / min. Preferably, during the pyrolysis carbonization process, the pyrolysis temperature needs to remain stable at the target temperature. The carbonization furnace is initially increased at a rate of 7-12°C / min (preferably 8.5°C / min) to the final target temperature (such as 500°C), and then maintained for at least 10 hours. The heating rate can have a certain influence on the yield, ash content and total carbon content of biochar to a certain extent. Compared with a larger heating rate, the ash content produced is relatively low when the heating rate is around 10°C / min.

[0081] It should be noted that the biochar preparation process requires a high-purity nitrogen atmosphere. The main function of filling with high-purity nitrogen (purity > 99.99%) is to prevent oxygen from reacting with carbonized materials and avoid oxidation reactions during pyrolysis.

[0082] The biomass is pyrolyzed and carbonized in the carbonization furnace. After the pyrolysis and carbonization are completed, the carbonization furnace is first cooled to room temperature (i.e. 25±5°C), and then the carbonization furnace is opened to obtain the pyrolyzed biochar, which is then crushed and ground. The above operations prevent the oxidation of biochar, improve safety, reduce thermal stress, maintain the characteristics of biochar, and improve the efficiency of post-processing. First of all, in terms of preventing oxidation, when the carbonization furnace is opened at high temperature, the biochar is easily exposed to oxygen in the air, resulting in oxidation of the biochar, thereby reducing production and affecting quality. Slow cooling to room temperature can reduce this risk. In terms of improving safety, opening the furnace cover under high temperature may cause the sudden release of hot gas, smoke or carbonized products, increasing safety hazards. It is safer to operate after cooling to room temperature. In terms of reducing thermal stress, the cooling process can reduce the thermal stress caused by the rapid temperature change of the carbonization furnace and its internal materials, which helps to extend the service life of the equipment. In terms of maintaining product characteristics, excessively high temperature may change the structure and properties of biochar, and low-temperature cooling helps to maintain the physical and chemical properties of biochar, such as pore structure and specific surface area. In terms of improving the efficiency of post-processing, when operating under low temperature conditions, subsequent processing (such as crushing, screening, etc.) may be more convenient, reducing the generation of fragments and improving product consistency.

[0083] During the grinding process, it is ensured that larger particles are ground into pieces, so that the particle size of the biochar particles is 0.15-0.5 mm, that is, the obtained biochar particles are smaller, and no larger particles exist.

[0084] The biochar of the present invention is a solid material with high carbon content, high porosity, strong adsorption capacity and multiple uses, which is formed after biomass is pyrolyzed and carbonized under anaerobic conditions for a certain period of time. It is regarded as a new opportunity to mitigate global warming and has great potential in carbon fixation and climate change mitigation; it can also be used as a soil pollution repair agent and improver.

[0085] In step S200, the water used for adjustment is deionized water. After the water content is adjusted to 100% of its maximum water holding capacity (or directly immersed in deionized water), the biochar needs to be stirred to be evenly dispersed in the deionized water.

[0086] In step S300, the time ratio of wet culture to drying treatment in treatment A is 2:1 (preferably 14 to 16 hours for wet culture and 8 to 10 hours for drying treatment), the temperature of wet culture is 20 to 25°C, the temperature of drying treatment is 55 to 65°C, until the water content is less than 5%. The time ratio of freezing treatment to thawing treatment in treatment B is 2:1 (preferably 14 to 16 hours for freezing treatment and 8 to 10 hours for thawing treatment), the temperature of freezing treatment is -12 to -18°C, and the temperature of thawing treatment is 20 to 25°C.

[0087] In step S400, the mixture is repeated for at least 25 times. The mixture is placed in a sealed bag and dried, and the sealed bag is placed in a cool and dry place at room temperature.

[0088] The carbon in biochar is not easily decomposed by soil microorganisms due to its highly aromatic and stable chemical structure, so it can be stored in the soil for a long time. The biochar treated by the present invention further decomposes the organic matter in it and further stabilizes its structure. It can also have an impact on greenhouse gas emissions. On the one hand, it can indirectly reduce greenhouse gas emissions by improving the soil and increasing the content of organic matter in the soil; on the other hand, it can directly reduce the emission of CH4 and N2O in the soil. As a soil pollution remediation agent, it has an adsorption effect on pollutants in the soil. The biochar treated by the present invention has an increased specific surface area, an increased mesoporous volume, and an improved adsorption effect; at the same time, it can change the form of pollutants by adjusting the pH of the soil, thereby reducing the harm of pollution. As a soil conditioner, it can optimize and improve the health of the soil and promote plant growth.

[0089] The improved method of the present invention can increase the specific surface area of ​​biochar and promote the development of the pore structure of biochar. For treatment A, the specific surface area of ​​biochar is increased by repeated strong evaporation; for treatment B, the specific surface area of ​​biochar is increased mainly by promoting the crushing of biochar particles into finer particles. In addition, the improved method of the present invention can enhance the thermal stability of biochar, mainly due to the pyrolysis of aromatic compounds and the transformation and decomposition of inorganic mineral components, which may be specifically due to the promotion of the decomposition of wood fiber components and hemicellulose and the increase of ash content.

[0090] [Example 1] An improved method for improving the carbon fixation capacity of biochar is provided, comprising the following steps:

[0091] S100: Obtain the biochar to be improved. Specifically, the preparation process of the biochar is as follows: the wheat straw is naturally air-dried, then cut into small segments of about 10 cm, and placed in a carbonization furnace for carbonization. The carbonization furnace is an inert atmosphere formed by nitrogen with a flow rate of 0.5 L / min to ensure that the preparation process is in an oxygen-free environment. During the pyrolysis carbonization process, the carbonization furnace is initially increased to 500°C at a rate of 8.5°C / min, and then maintained for 10 hours. After the pyrolysis carbonization is completed, the carbonization furnace is first cooled to room temperature, and then the carbonization furnace is opened to obtain the pyrolyzed biochar, and the biochar is crushed and ground to make the particle size of the biochar 0.15 to 0.5 mm.

[0092] S200: adjusting the water content of the biochar obtained in step S100 to 100% of its maximum water holding capacity with deionized water, stirring the biochar to make it evenly dispersed in the deionized water, and maintaining it for 24 hours to obtain water-saturated biochar;

[0093] S300: Treatment A was used, and the water-saturated biochar was cultured at 25°C for 16 h, and then dried at 65°C for 8 h;

[0094] S400: Step S200 and step S300 are repeated 30 times, and then the repeatedly treated biochar is dried and stored to obtain improved biochar with improved carbon fixation capacity.

[0095] [Example 2] An improved method for improving the carbon fixation capacity of biochar is provided, comprising the following steps:

[0096] S100: Obtain the biochar to be improved. Specifically, the preparation process of the biochar is as follows: the wheat straw is naturally air-dried, then cut into small segments of about 10 cm, and placed in a carbonization furnace for carbonization. The carbonization furnace is an inert atmosphere formed by nitrogen with a flow rate of 0.5 L / min to ensure that the preparation process is in an oxygen-free environment. During the pyrolysis carbonization process, the carbonization furnace is initially increased to 500°C at a rate of 8.5°C / min, and then maintained for 10 hours. After the pyrolysis carbonization is completed, the carbonization furnace is first cooled to room temperature, and then the carbonization furnace is opened to obtain the pyrolyzed biochar, and the biochar is crushed and ground to make the particle size of the biochar 0.15 to 0.5 mm.

[0097] S200: adjusting the water content of the biochar obtained in step S100 to 100% of its maximum water holding capacity with deionized water, stirring the biochar to make it evenly dispersed in the deionized water, and maintaining it for 24 hours to obtain water-saturated biochar;

[0098] S300: Treatment B was used, where the water-saturated biochar was frozen at -18 °C for 16 h and then thawed at 25 °C for 8 h;

[0099] S400: Step S200 and step S300 are repeated 30 times, and then the repeatedly treated biochar is dried and stored to obtain improved biochar with improved carbon fixation capacity.

[0100] [Example 3] is different from [Example 1] in that the raw material for preparing biochar is corn straw, and everything else is the same.

[0101] [Example 4] is different from [Example 2] in that the raw material for preparing biochar is corn straw, and everything else is the same.

[0102] For the above examples, the basic physical and chemical properties, thermal stability, etc. are comprehensively analyzed. The results are shown in Tables 1-2. Figures 1-2 shown.

[0103] Table 1-Comparison of physical and chemical properties of biochar before and after improvement

[0104]

[0105] As shown in Table 1, in terms of pH, both wheat straw biochar and corn straw biochar were alkaline before improvement, and the improvement of the present invention led to a decrease in the pH of wheat straw and corn straw biochar; in terms of ash content, the ash content of wheat straw biochar increased by 19.02% and 22.70% respectively after improvement, while the ash content of corn straw biochar was less affected. In terms of specific surface area, the treatment cycle A increased the specific surface area of ​​wheat straw biochar and corn straw biochar by 102.10% and 353.44% respectively. The treatment cycle B increased the specific surface area of ​​wheat straw biochar and corn straw biochar by 11.21% and 92.13% respectively. This shows that the method of the present invention can increase the specific surface area of ​​biochar, and the increase in specific surface area has a positive effect on carbon fixation and mitigation of greenhouse gas emissions.

[0106] Table 2-Main element composition of biochar before and after improvement

[0107]

[0108] As can be seen from Table 2, the C content of wheat straw biochar is higher than that of corn straw biochar, while the O / C atomic ratio and polarity index (N+O) / C are lower than those of corn straw biochar. The N and S contents of all biochar samples are not high. The improvement methods of the present invention all lead to an increase in the O content of biochar, among which the increase in wheat straw biochar is obvious, resulting in an increase of 6.31% and 4.24% in its content, respectively. In addition, the improvement method of the present invention leads to a slight increase in the O / C atomic ratio and polarity index (N+O) / C of wheat straw biochar, while there is no significant change in corn straw biochar.

[0109] Depend on Figure 1 It can be seen that the pyrolysis process of wheat straw and corn straw biochar before and after improvement is basically the same, mainly including three stages: the room temperature ~ 300 ℃ stage is mainly the evaporation of water. Since the water content of biochar before and after improvement is low, the first weight loss step of all TG curves is relatively gentle, with a weight loss of less than 4%. At the same time, it can be observed that all DTG curves have the first peak near 80-100 ℃, which is also evidence of water evaporation; with the increase of preparation temperature, the peak becomes more gentle, and neither treatment A cycle nor treatment B cycle has a significant effect on the peak.

[0110] The 300-500℃ stage is mainly characterized by the massive decomposition of cellulose and hemicellulose, and some refractory lignin will also decompose. All TG curves show a significant downward zone, with a weight loss of about 65% to 75%. The weight loss of wheat straw biochar is significantly higher than that of corn straw biochar. Both treatment A and treatment B cycles cause the weight loss step of the wheat straw biochar TG curve to move to the high temperature zone, among which the weight loss step after the treatment B cycle improvement shifts to the right most significantly, followed by the treatment A cycle improvement; while the treatment A cycle improvement causes the weight loss step of corn straw biochar to move slightly to the high temperature zone, and the treatment B cycle improvement has no significant effect on the weight loss step temperature of corn straw biochar. At this stage, all DTG curves show a significant main peak between 400 and 500℃, which is mainly formed by the decomposition of cellulose. The treatment A cycle and treatment B cycle improvements cause the peak of the wheat straw biochar DTG curve to move to the high temperature zone, among which the treatment B cycle causes the peak to shift to the right more significantly; the treatment A cycle and treatment B cycle only cause the peak of the corn straw biochar DTG curve to move significantly to the high temperature zone. Since hemicellulose is most susceptible to pyrolysis, no shoulder peak formed by hemicellulose decomposition was observed in the DTG curve of biochar prepared at high temperature.

[0111] Above 500℃, the main process is the decomposition of residual lignin, which is a slow process and the weight loss is not obvious.

[0112] The biochar treated by the present invention showed a phenomenon of moving to the high temperature zone to varying degrees in the second stage of the thermogravimetric curve, indicating that its thermal stability was improved.

[0113] The stability factor R 50 The carbon fixation potential of biochar samples was evaluated by the stability coefficient R of biochar samples (i.e. the temperature ratio of biochar to graphite at 50% oxidation / volatilization). 50 It is obtained from formula (1). In the formula, R 50,x is the temperature at which the biochar sample x is 50% oxidized / volatilized, directly read from the TG curve corrected for the moisture and ash contents of the biochar sample, and then corrected; T 50,石墨 It is the temperature at which 50% of graphite is oxidized / volatilized.

[0114]

[0115] R 50 The carbon sequestration potential of biochar can be divided into strong (R 50 ≥0.70), medium (0.50≤R 50 <0.70) and weak (R 50 <0.50) three levels.

[0116] Depend on Figure 2 It can be seen that for the biochar before improvement, corn straw biochar R 50The improvement of treatment A cycle and treatment B cycle made wheat straw biochar and corn straw biochar R 50 The B cycle effect is more obvious for wheat straw biochar, making its R 50 For corn straw biochar, the effect of treatment A cycle is more obvious, making its R 50 Increased by 2.45%.

[0117] Depend on Figure 3 It can be seen that the pore volume change rate of the modified wheat straw and corn straw biochar treated by the present invention is large, and both change greatly within the pore size range of 2 to 50 nm, and the effect of treatment A cycle is more obvious, indicating that the specific surface area and porosity of the modified biochar sample increase, and the pore size distribution is concentrated in the mesopores. The abundant mesopores can provide a suitable habitat and promote the growth of microorganisms and plant roots. Microorganisms promote the accumulation of organic carbon by decomposing organic matter and interacting with plant roots, and also enhance the carbon fixation capacity of the soil; the increase in mesopores enables biochar to better improve the physical and chemical properties of the soil (for example, increase the cation exchange capacity), which improves the soil to form a healthier soil ecosystem, thereby better retaining and accumulating carbon; in addition, the increase in mesopores and surface area makes the carbon skeleton of biochar more stable, reduces its decomposition rate in the environment, can play a role for a longer time, and helps to adsorb and fix more organic carbon and nutrients, reducing the risk of degradation by microorganisms or other soil organisms.

[0118] In summary, the above examples show that for high-temperature wheat straw biochar and corn straw biochar, after the improvement treatment of the present invention, the thermal stability of the biochar is improved, and the stability and carbon sequestration potential of the improved wheat straw biochar (at a weak level before improvement) and corn straw biochar (at a medium level before improvement) reach a medium level, which makes the biochar have greater potential in carbon sequestration and climate change mitigation, and the long-term application of straw biochar prepared at higher temperatures is beneficial to carbon sequestration.

[0119] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. An improved method for improving the carbon fixation capacity of biochar, characterized in that: The following steps are involved: S100: obtaining biochar to be improved, wherein the particle size of the biochar is in the range of 0.15 to 0.5 mm; S200: adjusting the water content of the biochar to 100% of the maximum water holding capacity with water to obtain water-saturated biochar; S300: The water-saturated biochar obtained in S200 is subjected to the following treatments: Treatment A: the water-saturated biochar is wet cultured and then dried; or, Treatment B: freezing the water-saturated biochar and then thawing it; S400: Repeat step S200 and step S300 for at least 25 rounds, and then dry and store the repeatedly treated biochar to obtain improved biochar with improved carbon fixation capacity.

2. The improved method according to claim 1, characterized in that: According to the selection of the processing method of step S300 in different rounds, it can be divided into the following situations: Case 1: Choose treatment A every time; Case 2: Choose treatment B every time; Case 3: Process A or Process B is selected each time, that is, Process A is selected in some rounds and Process B is selected in the remaining rounds.

3. The improved method according to claim 1, characterized in that: The treatment A: the time ratio of wet culture to dry treatment is 2:1, the temperature of wet culture is 20-25°C, and the temperature of dry treatment is 55-65°C.

4. The improved method according to claim 3, characterized in that: The duration of moist culture is 14 to 16 hours; The drying time is 8 to 10 hours.

5. The improved method according to claim 1, characterized in that: The treatment B: the time ratio of the freezing treatment to the thawing treatment is 2:1, the temperature of the freezing treatment is -12 to -18°C, and the temperature of the thawing treatment is 20 to 25°C.

6. The improved method according to claim 5, characterized in that: The duration of freezing treatment is 14 to 16 hours; The thawing process takes 8 to 10 hours.

7. The improved method according to any one of claims 1 to 6, characterized in that: In step S100, the method for preparing biochar comprises the following steps: S101: Obtain biomass raw materials; S102: After air-drying the biomass raw material, heat it in an oxygen-free atmosphere at a temperature below 500° C. for 10 hours, and then cool it to room temperature. Take out the biochar, crush it, and grind it to make the particle size of the biochar particles 0.15 to 0.5 mm.

8. The improved method according to claim 7, characterized in that: The water content of the biomass raw material after air drying is less than 5%, and the biomass raw material is cut into small segments of 8 to 12 cm after air drying.

9. The improved method according to claim 8, characterized in that: The carbonization process in step S102 is implemented in a carbonization furnace, and the carbonization furnace is raised to the final target temperature at a rate of 7-12° C. / min and then maintained for at least 10 hours.

10. The improved method according to claim 1, characterized in that: In step S200, the water used for adjustment is deionized water.

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