A method for modifying balsa wood biochar and its application

Abstract

This application relates to a method for modifying balsa wood biochar and its application. The biochar preparation method provided in this application involves anaerobic carbonization to produce balsa wood biochar, controlling the degree of carbonization to obtain relatively stable biochar. Different phosphates are used to modify balsa wood biochar, and the modification effects and efficacy of different phosphates are compared to identify a suitable modified biochar for balsa wood cultivation. Combining this with hole application of biochar can significantly improve biochar utilization efficiency and save costs.

Description

Technical Field

[0001] This invention relates to the field of biochar preparation technology, and in particular to a method for modifying balsa wood biochar and its application. Background Technology

[0002] Biochar is a solid material produced by pyrolyzing biomass (such as plant residues and wood chips) in a low-oxygen environment. It has a highly porous structure and high carbon content, making it widely used in soil improvement and environmental remediation. It can also be used as a filter material to adsorb heavy metals, pesticides, and other pollutants from water; biochar can also be used as a filler to improve the performance of plastics, rubber, and other composite materials; and biochar can be used to produce environmentally friendly building materials, such as carbon negative concrete and insulation materials.

[0003] Traditional biochar production methods include conventional kiln methods, pyrolysis, gasification, hydrothermal carbonization, and microwave pyrolysis. However, these methods produce biochar with relatively low efficiency, while the demand for biochar in soil improvement is significant. The low efficiency of existing biochar means its effectiveness in soil improvement is limited, requiring large quantities, increasing costs, and resulting in waste. Balsa wood, from logging to processing, generates a large amount of scrap. Its low density makes it an ideal material for biochar production. However, traditional biochar processing methods generally struggle to control the degree of carbonization, leading to unstable carbon structures and limited soil improvement effects after application.

[0004] Therefore, it is urgent to modify its specific properties to maximize its application. Thus, a method for modifying biochar is needed to improve its efficiency. Summary of the Invention

[0005] To address or partially address the problems existing in related technologies, this application provides a method for modifying balsa wood biochar, the modification method comprising the following steps:

[0006] 1) After the balsa wood branches are crushed once and dried, balsa wood fragments are obtained. Then, after anaerobic dry distillation pyrolysis, they are crushed a second time to obtain balsa wood biochar fragments.

[0007] 2) After mixing the balsa wood biochar fragments and phosphate in 1) at a mass ratio of 1-5:1, soak them in deionized water for a certain period of time and then dry them to obtain dried balsa wood biochar fragments.

[0008] The phosphate is ammonium dihydrogen phosphate;

[0009] 3) The dried balsa wood biochar fragments obtained in 2) are subjected to secondary anaerobic distillation to obtain modified balsa wood biochar.

[0010] Furthermore, the drying temperature in 1) is 70°C, and the drying time is 48 hours.

[0011] Furthermore, the specific operation of anaerobic carbonization is as follows: balsa wood fragments are placed in a carbonization furnace; the temperature rise rate of the carbonization furnace is 3-5℃ / min, and the temperature is maintained at 400℃ for 2-3 hours.

[0012] Furthermore, the specific operation of the secondary anaerobic distillation is as follows: the dried balsa wood biochar fragments obtained in step 2) are placed into a carbonization furnace; the temperature rise rate of the carbonization furnace is 3-5℃ / min, and the temperature is raised to 400℃ and maintained for 1-2 hours.

[0013] Furthermore, the duration in 2) is 72 hours.

[0014] On the other hand, this application also provides a method for applying balsa wood biochar to soil, the method comprising the following steps:

[0015] (1) Determine the location according to a certain row spacing and plant spacing, dig a hole at the corresponding location, loosen the soil completely, sprinkle dazomet fungicide, cover for a certain period of time, and then ventilate.

[0016] (2) After the balsa wood is rooted, biochar is applied by hole application; the amount of biochar applied is 60-120g.

[0017] The specific steps for applying the solution in holes are as follows: dig a hole with a diameter of 8-12cm and a depth of 8-12cm at a distance of 15-20cm from the seedling;

[0018] The biochar is the modified balsa wood biochar prepared by the above modification method.

[0019] Furthermore, the row spacing is 4 meters and the plant spacing is 3.5 meters.

[0020] Furthermore, the size of the pit is: 45-55cm in diameter and 48-53cm in depth.

[0021] Furthermore, the covering time in (1) is 10-15 days; the exhaust time is 8-12 days.

[0022] On the other hand, this application also provides an application of balsa wood biochar in soil improvement, wherein the balsa wood biochar is prepared by the above-mentioned modification method of balsa wood biochar.

[0023] Beneficial effects

[0024] 1) Process for preparing balsa wood biochar by anaerobic carbonization;

[0025] Anaerobic carbonization, conducted under anaerobic conditions, reduces carbon oxidation losses, enabling biomass to be more effectively converted into stable carbon forms, thereby improving the carbon retention rate of balsa biochar. Due to the anaerobic environment, anaerobic carbonization reduces the generation of harmful gases (such as carbon monoxide and other volatile organic compounds), resulting in cleaner emissions compared to traditional combustion or pyrolysis methods. Combustible gases and liquid byproducts (such as bio-oil) produced during anaerobic carbonization can be collected for energy production, improving the overall resource utilization efficiency of the process. Compared to high-temperature pyrolysis, anaerobic carbonization is conducted at lower temperatures, resulting in lower energy consumption and greater energy efficiency. This process can process a variety of biomass feedstocks, including agricultural waste and forestry residues, making it widely applicable. The biochar produced by anaerobic carbonization has a more stable structure and can persist in the soil for a long time, providing continuous soil improvement and carbon sequestration effects.

[0026] 2) Phosphate-modified balsa wood biochar method: Balsa wood cultivation significantly increases the exchangeable aluminum content in the soil, which limits the availability of phosphorus. Phosphate-modified balsa wood biochar can significantly increase the availability of phosphorus in the soil while inhibiting further increases in exchangeable aluminum content.

[0027] 3) This application uses soil in-situ sterilization technology to eliminate the residual effects of soil microorganisms, promote the re-recruitment of microbial communities by balsa wood, build new interaction relationships, and increase the accumulation of balsa wood biomass;

[0028] 4) This application uses biochar hole application during soil tillage, which is applied in fixed locations to accurately deliver nutrients, saving on biochar application and reducing costs.

[0029] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0030] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments of this application taken in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of this application.

[0031] Figure 1 This is a scanning electron microscope image of balsa wood biochar.

[0032] Figure 2 This is a scanning electron microscope mapping image of ammonium dihydrogen phosphate modified balsa biochar;

[0033] A: Scanning electron microscope image;

[0034] B: Electron image of elemental distribution;

[0035] C: Spectrum of total element distribution.

[0036] Figure 3 This is a scanning electron microscope mapping image of potassium dihydrogen phosphate modified balsa biochar;

[0037] A: Scanning electron microscope image;

[0038] B: Electron image of elemental distribution;

[0039] C: Spectrum of total element distribution.

[0040] Figure 4 This is a comparison of scanning electron microscope images of biochar prepared from different materials;

[0041] A: Scanning electron microscope image of balsa wood biochar;

[0042] B: Scanning electron microscope image of Ficus biochar;

[0043] C: Scanning electron microscope image of rubber tree biochar;

[0044] D: Scanning electron microscope image of rice straw biochar.

[0045] Figure 5 This figure shows the effects of biochar and soil sterilization on the plant height of balsa wood grown in soils from different sources. In the figure, P (planted balsa wood) and N (no balsa wood planted) represent soil sources; S (sterilized) and L (unsterilized) represent sterilization treatments; BioC (biochar), BioK (potassium dihydrogen phosphate modified biochar), BioN (ammonium dihydrogen phosphate modified biochar), and CK (control) represent biochar addition treatments. In the figure, *, *** indicate significant differences between different experimental treatments at the p<0.05, 0.01, and 0.001 levels; the same applies below.

[0046] The left figure shows the effect of different soil sources on the height of balsa trees;

[0047] The middle figure shows the effect of soil sterilization on the height of balsa wood plants;

[0048] The right figure shows the effect of biochar addition on the height of balsa wood plants;

[0049] Figure 6 The effects of biochar and soil sterilization on balsa wood biomass in soils from different sources;

[0050] The left figure shows the impact of different soil sources on balsa wood biomass;

[0051] The middle figure shows the effect of soil sterilization on balsa wood biomass;

[0052] The right figure shows the effect of biochar addition on balsa wood biomass.

[0053] Figure 7 The effects of biochar and soil sterilization on the structure of fungal communities in soils from different sources;

[0054] A: Diagram showing the differences in soil fungal community structure under different experimental treatments;

[0055] B: Species composition diagram of soil fungi under biochar and soil sterilization

[0056] Figure 8 The effects of biochar and soil sterilization on the functional groups of fungi in soils from different sources;

[0057] Figure 9 This is a flowchart illustrating the present invention. Detailed Implementation

[0058] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0059] Balsa wood (Ochroma lagopus) has specific market demand and is a commonly used composite sandwich panel material for large wind turbine blades. However, the rapid growth of balsa wood inevitably leads to changes in soil carbon composition, microbial imbalance, and soil nutrient limitation. Cultivating the soil carbon pool (e.g., applying biochar, increasing soil biodiversity) can enhance soil carbon sequestration, improve soil fertility, and increase yields and income. As the planting years of balsa wood increase, the intensity and direction of the balsa wood-soil interaction also change, becoming a key factor limiting balsa wood growth.

[0060] Traditional biochar preparation methods have limited effectiveness when applied to soil, while anaerobic distillation can produce biochar with varying degrees of carbonization as needed. Balsa wood cultivation depletes a large amount of nutrients, often requiring the application of chemical fertilizers to increase yield; however, this exacerbates soil acidification and nutrient loss. This invention uses phosphate-modified balsa wood biochar to achieve a slow release of nutrients. However, previous inventions simply described single preparation methods without comparing the modification effects of different phosphates, lacking verification of the modified biochar's efficacy. Biochar application techniques typically involve mixing it into the soil during tillage, a method unsuitable for balsa wood plantations. This invention employs a more efficient hole-application method to improve the efficient utilization of biochar and nutrients. Balsa wood growth alters the soil's microbial community, creating "ecological memory" that is detrimental to seedling growth when balsa wood is replanted. This application utilizes a chemical sterilization method to eliminate the residual effects of soil microorganisms. Applying modified biochar regulates soil ecological function, effectively improves the efficiency of balsa seedlings in recruiting beneficial bacteria, and promotes the establishment and growth of balsa seedlings.

[0061] Balsa wood biochar was prepared using anaerobic carbonization technology, and the degree of carbonization was controlled to obtain relatively stable biochar. Balsa wood biochar was modified with different phosphates, and the modification effects and efficacy of different phosphates were compared to identify the modified biochar suitable for balsa wood cultivation. Soil sterilization technology was incorporated to eliminate the residual effects of accumulated microorganisms in balsa wood plantations, providing a more suitable environment for later balsa wood cultivation. Hole application of biochar significantly improved biochar utilization efficiency and saved costs. This invention aims to obtain a highly efficient biochar through phosphate-modified balsa wood biochar, which can improve soil, especially through soil sterilization to eliminate residual effects of soil microorganisms. The establishment of new microbial communities can significantly promote the establishment and growth of balsa wood seedlings.

[0062] Example 1: Preparation of Balsamic Biochar

[0063] (1) Collect balsa wood branches from the balsa wood plantation in Menglun Town, Xishuangbanna, Yunnan Province, and crush them into thin slices of 5-10cm in size using a pulverizer; dry them in an oven at 70℃ for 48 hours.

[0064] (2) Then it is placed in a carbonization furnace and anaerobic dry distillation pyrolysis is used to prepare balsa wood biochar. The programmed temperature rise rate is set to 3-5℃ / min, and the temperature is maintained at 400℃ for 2-3 hours.

[0065] (3) The prepared biochar is further crushed. The crushed biochar has a larger specific surface area, which facilitates the preparation of modified biochar in the later stage.

[0066] (4) The previously prepared balsa wood biochar fragments were soaked in a phosphate solution for at least 72 hours at a mass ratio of balsa wood biochar fragments to phosphate of 1-5:1, then dried in an oven at 70°C, followed by soaking in deionized water. Afterwards, an anaerobic distillation method was used, with a temperature ramp rate of 3-5°C / min, and the temperature was maintained at 400°C for 1-2 hours. Potassium dihydrogen phosphate and ammonium dihydrogen phosphate were used as the phosphates.

[0067] (5) Scanning electron microscopy structure of modified balsa wood biochar

[0068] Scanning electron microscopy (SEM) images of balsa wood biochar and its modified biochar revealed that the porous structure of balsa wood makes it a preferred material for biochar preparation. Figure 1 Phosphorus in ammonium dihydrogen phosphate-modified balsa wood biochar is uniformly adsorbed on the surface of the charcoal. Figure 2 The phosphorus distribution is better than that in potassium dihydrogen phosphate modified biochar. Figure 3 ).

[0069] Comparative Example 1: Preparation of Biochar from Different Raw Materials

[0070] Biochar was prepared by collecting branches of banyan trees, rubber trees, and rice straw according to the method in Example 1, in order to compare the differences in biochar prepared from the three materials.

[0071] Compared to biochar made from banyan and rubber trees, balsa wood biochar has a larger pore structure and a stronger adsorption capacity. Compared to rice straw biochar, balsa wood biochar has a more solid and stable physical structure due to its lignified structure. Figure 4 This allows for the preservation of a more complete porous structure in the soil, leading to better soil improvement. It also facilitates subsequent biochar modification.

[0072] Comparative Example 2: Screening of phosphates required for phosphate-modified balsa wood biochar

[0073] Two types of phosphates, ammonium dihydrogen phosphate and potassium dihydrogen phosphate, were used to modify balsa wood biochar. An excessively high phosphate ratio led to incomplete binding and precipitation with the biochar, while an excessively low ratio was detrimental to improving biochar efficiency. Based on preliminary experiments, to ensure maximum binding between phosphate and biochar, a balsa wood biochar:phosphate mass ratio of 1:1 was selected, and deionized water was added for soaking for 72 hours. Subsequently, it was dried in an oven at 70℃ for 36 hours. Anaerobic distillation was used, with a temperature ramp-up rate of 3℃ / min, and the temperature was maintained at 400℃ for 1 hour. Compared with biochar modified with potassium dihydrogen phosphate, the elements in the biochar modified with ammonium dihydrogen phosphate were more evenly distributed on the surface of the biochar, resulting in better modification and making it more suitable for phosphate-modified biochar.

[0074] Example 2: Pot Experiment with Modified Biochar

[0075] To investigate the efficacy of modified balsa wood biochar, a pot experiment was conducted.

[0076] 1) Soil source: Soil from a plantation where balsa wood was planted for 4 years; soil from an adjacent plantation where no balsa wood was planted served as a control.

[0077] 2) Soil sterilization treatment: Dazomet sterilization was used, and unsterilized soil was used as a control.

[0078] 3) Biochar addition treatment: unmodified balsa wood biochar, potassium dihydrogen phosphate modified balsa wood biochar, ammonium dihydrogen phosphate modified balsa wood biochar, and control without added biochar.

[0079] The experiment employed a full factorial design (soil source, soil sterilization, and biochar addition) with 5 replicates, totaling 80 samples. The balsa wood growing period lasted 4 months, from June 20, 2024, to October 20, 2024, when balsa wood biomass was harvested. Biochar efficacy was evaluated by measuring balsa wood plant height and biomass.

[0080] Treatment group 1 consisted of soil that had never been planted with balsa wood; no soil sterilization was performed; and no biochar was added.

[0081] Treatment group 2 consisted of soil that had never been planted with balsa wood; no soil sterilization was performed; and unmodified balsa wood biochar was added.

[0082] Treatment group 3 consisted of soil that had never been planted with balsa wood; no soil sterilization was performed; and potassium dihydrogen phosphate was added to modify balsa wood biochar.

[0083] Treatment group 4 consisted of soil that had never been planted with balsa wood; no soil sterilization was performed; and ammonium dihydrogen phosphate-modified balsa wood biochar was added.

[0084] Treatment group 5 consisted of soil that had never been planted with balsa wood; sterilized with dazomet; and without the addition of biochar.

[0085] Treatment group 6 consisted of: soil that had never been planted with balsa wood; sterilized with dazomet; and supplemented with unmodified balsa wood biochar.

[0086] Treatment group 7 consisted of: soil that had never been planted with balsa wood; dazomet sterilization; and balsa wood biochar modified with potassium dihydrogen phosphate.

[0087] Treatment group 8 consisted of soil that had never been planted with balsa wood; sterilized with dazomet; and treated with ammonium dihydrogen phosphate-modified balsa wood biochar.

[0088] Treatment group 9 consisted of soil from a plantation where balsa wood had been grown for 4 years; no soil sterilization was performed; and no biochar was added.

[0089] Treatment group 10 consisted of soil from a plantation where balsa wood had been planted for 4 years; no soil sterilization was performed; and unmodified balsa wood biochar was added.

[0090] Treatment group 11 consisted of soil from a plantation where balsa wood had been planted for 4 years; no soil sterilization was performed; and potassium dihydrogen phosphate was added to modify balsa wood biochar.

[0091] Treatment group 12 consisted of soil from a plantation where balsa wood had been planted for 4 years; no soil sterilization was performed; and balsa wood biochar modified with ammonium dihydrogen phosphate was added.

[0092] Treatment group 13 consisted of soil from a plantation where balsa wood had been grown for 4 years; sterilized with dazomet; and without the addition of biochar.

[0093] Treatment group 14 consisted of: soil from a plantation where balsa wood had been planted for 4 years; sterilized with dazomet; and supplemented with unmodified balsa wood biochar.

[0094] Treatment group 15 consisted of: soil from a plantation where balsa wood had been planted for 4 years; sterilized with dazomet; and treated with potassium dihydrogen phosphate-modified balsa wood biochar.

[0095] Treatment group 16 consisted of: soil from a plantation where balsa wood had been planted for 4 years; sterilized with dazomet; and treated with ammonium dihydrogen phosphate-modified balsa wood biochar.

[0096] The experimental results showed that, compared with soil in which balsa wood had been planted (treatment group 9), the height of balsa wood plants in soil without balsa wood (treatment group 1) was significantly higher by 47%; compared with soil in which balsa wood had been planted but not sterilized (treatment group 9), sterilized soil (treatment group 13) significantly increased the height of balsa wood plants by 52%; compared with soil in which balsa wood had been planted but no biochar was added (treatment group 9), applying biochar (treatment group 10) increased the height of balsa wood plants by 6%; applying ammonium dihydrogen phosphate modified biochar (treatment group 12) significantly increased the height by 133%; and sterilization combined with application of ammonium dihydrogen phosphate modified biochar (treatment group 16) significantly increased the height by 81%. Figure 5 Compared with soils where balsa wood had been planted (treatment group 9), the balsa wood biomass in soils without balsa wood (treatment group 1) was significantly higher by 83%. Compared with soils where balsa wood had been planted but not sterilized (treatment group 9), sterilized soil (treatment group 13) significantly increased balsa wood biomass by 190%. Compared with soils where balsa wood had been planted but no biochar was added (treatment group 9), applying biochar (treatment group 10) significantly increased balsa wood biomass by 35%. Applying ammonium dihydrogen phosphate modified biochar (treatment group 12) significantly increased it by 282%. Sterilization combined with application of ammonium dihydrogen phosphate modified biochar (treatment group 16) significantly increased it by 238%. Figure 6 ).

[0097] Example 3: Application of modified biochar

[0098] Determine the location according to the row spacing * plant spacing (4 meters * 3.5 meters), dig a circular pit about 50 cm in diameter and 50 cm deep at the corresponding site, loosen the soil completely, sprinkle in dazomet sterilizing agent, then cover with black film, seal it well and keep it for 10-15 days to achieve a complete sterilization effect. In addition, uncover the film for about 10 days to release the air and remove the steam generated in the soil, so as to better plant the balsa seedlings.

[0099] After the plant has established roots, apply biochar by hole application. Dig a hole about 10cm in diameter and 10cm deep about 15-20cm away from the seedling and fill it with 60-120g of biochar.

[0100] Soil samples were collected at a depth of 15 cm using a soil drill during balsa wood harvesting. High-throughput sequencing was employed to sequence amplicon samples of soil fungi. Bioinformatics methods were used to analyze the data. The results showed significant differences in the soil fungal community structure between soils previously planted with balsa wood and those not planted with balsa wood. Soil sterilization had the greatest impact on the soil fungal community structure, effectively eliminating the influence of previous balsa wood planting. Biochar addition had a relatively small impact on unsterilized soil. For sterilized soil, there was no significant difference between treatments with and without modified biochar, while treatments with modified biochar showed significant differences between treatments without biochar. Figure 7 Analysis of fungal functional groups revealed that sterilization significantly inhibited soil pathogens, while the application of biochar significantly increased the content of mycorrhizal fungi in the soil and reduced the abundance of soil pathogens. Figure 8 ).

[0101] Traditionally, biochar is applied during soil tillage and buried in the field soil. While this method significantly increases yields for densely planted field crops like rice and wheat, it's unnecessary to apply biochar to the entire field of large trees, whose planting density differs greatly from crops, thus hindering soil structure preservation. This invention employs hole application for precise nutrient delivery. This method significantly reduces biochar application costs.

[0102] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for modifying balsa wood biochar, characterized in that, The modification method includes the following steps: 1) The balsa wood branches are first crushed and then dried to obtain balsa wood fragments, which are then subjected to anaerobic pyrolysis and further crushed to obtain balsa wood biochar fragments; the drying temperature in 1) is 70 ℃ and the drying time is 48 hours; the specific operation of the anaerobic pyrolysis is as follows: the balsa wood fragments are placed in a carbonization furnace; the temperature rise rate of the carbonization furnace is 3-5 ℃ / min, and the temperature is raised to 400 ℃ and maintained for 2-3 hours; 2) The balsa wood biochar fragments from 1) are mixed with phosphate at a mass ratio of 1-5:1, soaked in deionized water for 72 hours and then dried to obtain dried balsa wood biochar fragments. The phosphate is ammonium dihydrogen phosphate; 3) The dried balsa wood biochar fragments obtained in 2) are subjected to secondary anaerobic distillation to obtain modified balsa wood biochar; the specific operation of the secondary anaerobic distillation is as follows: the dried balsa wood biochar fragments obtained in 2) are placed in a carbonization furnace; the temperature rise rate of the carbonization furnace is 3-5 ℃ / min, and the temperature is raised to 400 ℃ and maintained for 1-2 hours.

2. A method for applying balsa wood biochar to soil, characterized in that, The application method includes the following steps: (1) Determine the location according to a certain row spacing and plant spacing, dig a hole at the corresponding location, loosen the soil completely, sprinkle dazomet fungicide, cover for a certain period of time, and then ventilate; (2) After the balsa wood is rooted, biochar is applied by hole application; the amount of biochar applied is 60-120 g. The specific steps of the hole application method are as follows: dig a hole with a diameter of 8-12 cm and a depth of 8-12 cm at a distance of 15-20 cm from the seedling; The biochar is the modified balsa wood biochar prepared by the modification method described in claim 1.

3. The application method according to claim 2, characterized in that, The row spacing is 4 meters and the plant spacing is 3.5 meters.

4. The application method according to claim 2, characterized in that, The pit is 45-55 cm in diameter and 48-53 cm in depth.

5. The application method according to claim 2, characterized in that, The covering time in (1) is 10-15 days; the venting time is 8-12 days.

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