A method for preparing biochar by fermenting traditional Chinese medicine residues with cellulose-degrading bacteria

Abstract

The application discloses a method for preparing biochar by fermenting traditional Chinese medicine residues by using cellulose-degrading bacteria, and belongs to the technical field of agricultural waste resource utilization and microbial environmental remediation materials, and comprises the following steps: S1, raw material pretreatment; S2, strain activation and preparation of bacterial suspension; S3, solid-state aerobic gradient fermentation: the bacterial suspension is evenly sprayed to the pretreated traditional Chinese medicine residues at an inoculation amount of 1% of the dry weight of the traditional Chinese medicine residues, aerobic fermentation is carried out at 25 DEG C room temperature, the fermentation cycle is set to be gradient control of 0d, 30d, 50d, 70d and 90d, the pile is turned over once every three days during the fermentation to maintain the aerobic environment, and a blank control group without inoculating bacterial agents is set simultaneously; S4, drying treatment; S5, pyrolysis and carbonization: the dried material is placed in a muffle furnace, and modified traditional Chinese medicine residue biochar is obtained by natural cooling, and the application has the advantages of no chemical residue, low energy consumption, easy-to-obtain raw materials and excellent adsorption effect, and can efficiently realize the technical effect of dual application value of traditional Chinese medicine residue solid waste resource utilization and water body and soil environment remediation.

Description

Technical Field

[0001] This invention belongs to the technical field of agricultural waste resource utilization and microbial environmental remediation materials, and particularly relates to a method for preparing biochar by fermenting traditional Chinese medicine residues with cellulose-degrading bacteria. Background Technology

[0002] Chinese medicine residue is a large amount of solid organic waste generated during the processing of Chinese medicinal herbs and prepared Chinese medicines. If Chinese medicine residue is directly discarded or landfilled without resource utilization treatment, it can easily cause local soil and water eutrophication pollution and waste of organic matter resources.

[0003] Biochar, with its well-developed porous structure and abundant surface-active functional groups, is widely used in soil improvement, and the adsorption and treatment of organic pollutants and phosphorus pollutants in industrial wastewater. Current biochar preparation technologies generally involve the direct high-temperature pyrolysis of biomass raw materials. This results in a dense cross-linked structure formed by lignocellulose, hemicellulose, and lignin within the raw materials. The pyrolysis product has few pores, a low specific surface area, and a limited number of oxygen-containing functional groups, thus limiting its adsorption capacity for phosphorus, benzoquinone, and phenolic pollutants.

[0004] To improve the adsorption performance of biochar, existing modification methods mostly employ chemical pretreatment with dilute acids, dilute alkalis, and strong oxidants. Although this can improve the pore structure, it has drawbacks such as chemical reagent residues, high processing costs, secondary pollution during pyrolysis, and difficulty in treating waste liquid. A small number of microbial modified biochar technologies only use composite indigenous bacterial communities or single fixed-cycle fermentation, resulting in poor targeting of cellulose degradation, uncontrollable degree of fiber disintegration, and easy occurrence of excessive mineralization loss of organic matter and a significant decrease in char yield. It is impossible to simultaneously achieve both fiber breaking effect and char production efficiency.

[0005] Currently, existing technologies lack a complete process solution that uses gradient fermentation of traditional Chinese medicine residues with specific cellulose-degrading bacteria as a green pretreatment method, directionally regulates the pore size and surface functional groups of biochar, and simultaneously achieves integrated application of solid waste harmlessness, wastewater purification, and farmland improvement. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for preparing biochar by fermenting traditional Chinese medicine residues with cellulose-degrading bacteria. This method has the advantages of no chemical residues, low energy consumption, readily available raw materials, and excellent adsorption effect. It also has the advantages of efficiently realizing the dual application value of traditional Chinese medicine residue solid waste resource utilization and water and soil environment remediation. This method solves the problems of fiber decomposition difficulties, large chemical modification pollution, uncontrollable microbial pretreatment process, and poor adsorption performance of biochar in the existing traditional Chinese medicine residue carbonization process.

[0007] This invention is achieved by using cellulose-degrading bacteria to ferment medicinal herb residue to prepare biochar, comprising the following steps: S1. Raw material pretreatment: Take the mixed herbal medicine residue and air dry it at room temperature until the moisture content is ≤10%. Crush it into 2-5mm particles, add water to adjust the initial moisture content of the material to 50%-60% for fermentation, and mix well for later use. S2. Activation of bacterial strains and preparation of bacterial suspension: The strain *Delftia tsuruhatensis* was used. The wet cells were dispersed with sterile water and serially diluted with physiological saline to 10⁻⁶. -7 Single colonies with high cellulase activity were purified and screened by plate plating, and the bacterial suspension was obtained by scale-up culture. S3, Solid-state aerobic gradient fermentation: The bacterial suspension was evenly sprayed onto the pretreated Chinese medicine residue at an inoculation rate of 1% of the dry weight of the residue. Aerobic fermentation was carried out at 25℃. The fermentation cycle was set up with gradient controls of 0d, 30d, 50d, 70d, and 90d. During the fermentation period, the pile was turned over every 3 days to maintain an aerobic environment. A blank control group without bacterial inoculation was set up at the same time. S4. Drying treatment: After sampling the medicinal residues in each fermentation cycle, dry them in an oven at 105℃ until constant weight. S5. Pyrolysis and carbonization: The dried material is placed in a muffle furnace and heated to 500℃ at a rate of 5℃ / min. The temperature is kept constant for 2 hours and then naturally cooled to obtain modified Chinese medicine residue biochar.

[0008] As a preferred embodiment of the present invention, in step S1, the herbal mixed medicinal residue includes at least one of the medicinal plant roots, stems, leaves, and whole herbs.

[0009] As a preferred embodiment of the present invention, in step S3, the solid-state aerobic fermentation is not for the purpose of composting and maturation. Under the premise of preserving the basic carbon skeleton of the material without significant mineralization loss, it specifically destroys the dense cross-linked network of cellulose, hemicellulose, and lignin inside the Chinese herbal medicine residue, generating microcracks on the surface of the material.

[0010] As a preferred embodiment of the present invention, the fermentation time of the solid-state aerobic fermentation is 50 days or 70 days.

[0011] A modified biochar made from Chinese medicinal herb residue is prepared by the method described above for preparing biochar by fermenting Chinese medicinal herb residue with cellulose-degrading bacteria.

[0012] As a preferred embodiment of the present invention, the biochar is used in the purification and treatment of phosphorus, benzoquinone, and phenol pollutants in water.

[0013] As a preferred embodiment of the present invention, the biochar is used in farmland soil improvement and to promote crop growth.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: First, it utilizes existing microbial strains, resulting in highly targeted degradation and a green, pollution-free process: The microbial strain used in this invention is *Delftia tsuruhatensis*, a specialized cellulose-degrading bacterium isolated and purified from the natural environment. This strain differs from commercially available mixed microbial communities and native bacteria found in natural compost. It produces cellulase with high activity, which can specifically destroy the dense cross-linked network of cellulose, hemicellulose, and lignin within the medicinal residue. The entire process relies solely on microbial biodegradation, eliminating the need for chemical pretreatment reagents such as dilute acids, dilute alkalis, and oxidants. There are no chemical residues, and the pyrolysis of the material after fermentation produces no secondary pollution. The resulting biochar can be safely used in agricultural and environmental remediation applications such as soil improvement and water pollutant adsorption.

[0015] Secondly, by setting multiple fermentation durations (30d, 50d, 70d, 90d), the optimal fermentation process can be screened, enabling targeted regulation of biochar performance. Existing microbial pretreatment uses only a single fixed fermentation cycle, which cannot balance the degree of fiber degradation and the retention rate of organic matter. This invention sets up gradient fermentation times for control experiments: insufficient fermentation time results in incomplete fiber disintegration, while excessive fermentation time leads to significant loss of organic carbon and a decrease in char yield. Through comparison of multiple durations, the optimal fermentation cycle that balances the degradation effect of lignocellulose and the retention rate of organic matter in the material can be screened, precisely controlling the material pyrolysis behavior in the subsequent pyrolysis process, and directionally preparing high-performance biochar with well-developed pores and abundant functional groups, thus solving the defect of uncontrollable biochar quality in traditional processes.

[0016] Third, the fermentation pretreatment thoroughly breaks down the fiber structure of the medicinal herb residue, significantly improving the pore structure and adsorption performance of the biochar: After fermentation by cellulose-degrading bacteria, the dense lignocellulose skeleton of the medicinal herb residue is decomposed and destroyed, generating a large number of micropores inside the material; during the pyrolysis and carbonization process, volatiles are more easily released, resulting in a significant increase in the specific surface area and total pore volume of the final biochar, and a significant increase in the number of oxygen-containing active functional groups such as hydroxyl, carboxyl, and phenolic hydroxyl groups on the surface. Compared with biochar from unfermented medicinal herb residue directly carbonized, the product of this invention has a stronger adsorption capacity for heavy metals and organic pollutants, and as a soil conditioner, it can better retain nutrients, water, and fertilizer.

[0017] Fourth, the process is simple, low-cost, and easy to scale up: the raw material is waste residue from the processing of Chinese medicine, which is widely available and inexpensive to obtain; the pretreatment only requires coarse crushing + microbial fermentation at room temperature, without the need for high-temperature steam explosion or high-pressure equipment, resulting in low energy consumption; the self-screened strains can be propagated and reused, the fermentation conditions are mild and easy to control, the whole process is easy to operate, and it is suitable for laboratory small-scale tests and subsequent industrial batch processing of Chinese medicine residue. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the method flow provided in an embodiment of the present invention; Figure 2AThis is a scanning electron microscope (SEM) image of the direct carbonized biochar of the blank control group (unfermented Chinese medicine residue) provided in the embodiments of the present invention; Figure 2B This is a scanning electron microscope (SEM) image of the modified biochar after fermentation pretreatment provided in the embodiments of the present invention; Figure 2C This is a scanning electron microscope (SEM) mapping image of the modified biochar after adsorbing pollutants, provided in the embodiments of the present invention; Figure 3 This is a comparison of the infrared spectra of biochar made from medicinal residue and modified biochar made from medicinal residue provided in the embodiments of the present invention. Detailed Implementation

[0019] To further understand the invention's content, features, and effects, the following embodiments are provided, and detailed descriptions are given in conjunction with the accompanying drawings.

[0020] The structure of the present invention will now be described in detail with reference to the accompanying drawings.

[0021] refer to Figures 1 to 3 As shown in the figure, an embodiment of the present invention provides a method for preparing biochar by fermenting traditional Chinese medicine residue using cellulose-degrading bacteria, comprising the following steps: Raw material pretreatment: The mixed Chinese herbal medicine residue (mainly herbal Chinese herbal medicine residue, including mixed components such as roots, stems, leaves and whole herbs of plants) is naturally air-dried at room temperature to reduce the moisture content of the material to below 10%. Then, it is pulverized to a fixed particle size of 2-5mm using a pulverizer. The moisture content of the pulverized and dried Chinese herbal medicine residue is adjusted to a suitable range of 50-60%, which is the initial moisture content for fermentation, and then mixed evenly. Inoculation and fermentation: The cellulose-degrading bacterium *Delftia tsuruhatensis* (abbreviated as bacterium d) was activated and prepared into a bacterial suspension. The bacterial suspension was evenly sprayed onto the pretreated Chinese medicine residue, thoroughly mixed, and fermented with the uninoculated treatment group (abbreviated as ck) at room temperature (25℃). Fermentation time was set for 0, 30, 50, 70, and 90 days, and samples were taken at the corresponding time points for subsequent biochar preparation. During the fermentation period, the pile was turned over every 3 days to avoid anaerobic fermentation. Fermentation Mechanism and Function: The solid-state aerobic fermentation in this scheme is not a traditional composting process. Its core purpose is to use cellulose-degrading bacteria to specifically disrupt the dense cross-linked network of lignocellulose, hemicellulose, and lignin in the medicinal herb residue while ensuring that the basic carbon skeleton of the material is not over-mineralized. Through this fermentation pretreatment, a large number of microcracks can be generated on the surface of the medicinal herb residue, ultimately achieving the goal of significantly increasing the specific surface area and the number of functional groups of biochar without the need for additional chemical reagents.

[0022] Biochar preparation: After fermentation for a certain number of days, the Chinese herbal medicine residue was taken out, placed in an oven, and dried at 105℃ to constant weight. The dried Chinese herbal medicine residue was placed in a muffle furnace and heated to 500℃ at a heating rate of 5℃ / min, kept at that temperature for 2 hours, and then cooled to obtain modified biochar. Application: The modified biochar prepared in the above steps was applied to wastewater containing phosphorus, benzoquinone, and phenol for adsorption tests.

[0023] Based on the adsorption experiment results, the optimal combination of experimental factors was determined to be: 1% inoculum (dry weight), pyrolysis temperature of 500℃, heat preservation time of 2 hours, and fermentation days of 50 days and 70 days, which resulted in more stable adsorption effects of biochar.

[0024] Table 1: Comparison of removal rates of phosphorus, phenol, and benzoquinone by biochar from medicinal residue and modified biochar from medicinal residue.

[0025] Table 2: Comparison of specific surface area and pore size of biochar made from medicinal herb residue and modified biochar made from medicinal herb residue

[0026] This invention (specific and green strain, no chemical pollution throughout the process) selects environmentally isolated and purified Delftobacterium tsurugi, which has strong targeting for cellulose degradation and high enzyme production activity, unlike mixed bacterial communities; the entire pretreatment process relies solely on microbial biodegradation, without adding dilute acids, alkalis, oxidants or other modifying agents, leaving no chemical residues, and the entire pyrolysis process is free of secondary pollution, and the resulting biochar can be safely used for water remediation and farmland soil improvement.

[0027] (Controllable gradient fermentation cycle, targeted regulation of biochar quality) Existing microbial pretreatment only uses a single fermentation time, which cannot take into account both fiber degradation and organic matter retention. This invention sets up gradient fermentation controls of 30d, 50d, 70d, and 90d: insufficient fermentation time results in incomplete fiber disintegration, while excessive fermentation leads to significant loss of organic matter and a decrease in char yield. Through multi-cycle parallel experiments, the optimal process is screened, and the pyrolysis behavior is precisely controlled to stably prepare biochar with high porosity and high functional groups, solving the problem of uncontrollable product performance defects of traditional processes.

[0028] (Fully broken fibers significantly improve biochar adsorption performance) After pretreatment by bacterial fermentation, the dense lignocellulose skeleton of the medicinal herb residue is directionally decomposed, forming numerous microscopic cracks within the material. During the pyrolysis stage, volatiles are more easily released, resulting in a significant increase in the specific surface area and total pore volume of the final biochar, along with a substantial increase in the number of oxygen-containing active functional groups such as hydroxyl, carboxyl, and phenolic hydroxyl groups on the surface. Compared to the unfermented, directly carbonized control group, the adsorption capacity for phosphorus and aromatic organic pollutants is significantly improved. As a soil conditioner, it can efficiently retain nitrogen and phosphorus nutrients, conserve water and fertilizer, and promote crop root development.

[0029] (The raw materials are cheap and readily available, and the process is simple and easy to scale up.) The raw materials are pharmaceutical waste Chinese medicine residues, which are widely available and have extremely low acquisition costs. Pretreatment only requires coarse crushing + room temperature microbial fermentation, without the need for steam explosion, high pressure and high temperature equipment, resulting in low overall energy consumption. The strains can be mass-produced and reused, and the fermentation conditions are mild and easy to control. It can be prepared in small batches in the laboratory and is also suitable for industrialized centralized Chinese medicine residue treatment production lines.

[0030] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing biochar by fermenting traditional Chinese medicine residue using cellulose-degrading bacteria, characterized in that, Includes the following steps: S1. Raw material pretreatment: Take the mixed herbal medicine residue and air dry it at room temperature until the moisture content is ≤10%. Crush it into 2-5mm particles, add water to adjust the initial moisture content of the material to 50%-60% for fermentation, and mix well for later use. S2. Activation of bacterial strains and preparation of bacterial suspension: The strain *Delftia tsuruhatensis* was used. The wet cells were dispersed with sterile water and serially diluted with physiological saline to 10⁻⁶. -7 Single colonies with high cellulase activity were purified and screened by plate plating, and bacterial suspensions were obtained by large-scale culture. S3, Solid-state aerobic gradient fermentation: The bacterial suspension was evenly sprayed onto the pretreated Chinese medicine residue at an inoculation rate of 1% of the dry weight of the residue. Aerobic fermentation was carried out at 25℃. The fermentation cycle was set up with gradient controls of 0d, 30d, 50d, 70d, and 90d. During the fermentation period, the pile was turned over every 3 days to maintain an aerobic environment. A blank control group without bacterial inoculation was set up at the same time. S4. Drying treatment: After sampling the medicinal residues in each fermentation cycle, dry them in an oven at 105℃ until constant weight. S5. Pyrolysis and carbonization: The dried material is placed in a muffle furnace and heated to 500℃ at a rate of 5℃ / min. The temperature is kept constant for 2 hours and then naturally cooled to obtain modified Chinese medicine residue biochar.

2. The method for preparing biochar by fermenting traditional Chinese medicine residue using cellulose-degrading bacteria as described in claim 1, characterized in that: In step S1, the herbal mixed Chinese medicine residue contains at least one of the following: root, stem, leaf, and whole herb of a medicinal plant.

3. The method for preparing biochar by fermenting traditional Chinese medicine residue using cellulose-degrading bacteria as described in claim 1, characterized in that: In step S3, the solid-state aerobic fermentation is not for composting. Under the premise of preserving the basic carbon skeleton of the material without significant mineralization loss, it specifically destroys the dense cross-linked network of cellulose, hemicellulose, and lignin inside the Chinese herbal medicine residue, generating microcracks on the surface of the material.

4. The method for preparing biochar by fermenting traditional Chinese medicine residue using cellulose-degrading bacteria as described in claim 1, characterized in that: The fermentation time for the solid-state aerobic fermentation is 50 days or 70 days.

5. A modified biochar from Chinese medicinal herb residue, characterized in that, It is prepared by the method described in any one of claims 1-4.

6. The modified biochar from medicinal herb residue as described in claim 5, characterized in that: The application of biochar in the purification and treatment of phosphorus, benzoquinone, and phenol pollutants in water.

7. The modified biochar from medicinal herb residue as described in claim 5, characterized in that: The application of biochar in farmland soil improvement and crop growth promotion.

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