Straw decomposition agent for promoting decomposition and fixing carbon and preparation method of straw decomposition agent

Abstract

The invention discloses a straw decomposition agent capable of promoting decomposition and sequestration and a preparation method thereof, and belongs to the technical field of straw decomposition, the decomposition agent comprises a compound enzyme, attapulgite, calcium oxide, calcium peroxide, citric acid, sodium citrate, sodium alginate and other components, the enzyme is loaded by the attapulgite and then is coated by sodium alginate gel, and the carbon-sequestration-promoting straw decomposition agent is obtained. And calcium oxide and calcium peroxide capable of increasing temperature and releasing oxygen as well as a citric acid-sodium citrate buffer solution capable of maintaining the pH stable are added, and all the components in the decomposition agent act together to provide more suitable temperature, pH and aerobic environment for enzyme decomposition of the straws, so that the straws are decomposed under higher activity, the straw returning decomposition rate is further accelerated, and the straw yield is increased. Accumulation of soil organic matters is promoted, the soil fertility is improved, and the decomposition agent prepared by the invention has a good application prospect in the field of straw returning to the field.

Description

A straw composting agent that promotes decomposition and carbon fixation and its preparation method Technical Field

[0001] This invention relates to the field of straw composting technology, and in particular to a straw composting agent that promotes composting and carbon sequestration and its preparation method. Background Technology

[0002] my country is a traditional agricultural country with an annual crop straw production of up to 10 tons. Crop straw contains abundant nutrients such as nitrogen, phosphorus, and potassium. Returning straw to the field is of great significance for increasing soil carbon storage, improving soil fertility, improving soil quality, and reducing environmental pollution.

[0003] Returning straw to the field can be divided into two categories: direct return and indirect return. Direct return includes plowing and mulching; indirect return includes composting and feeding straw to livestock. Direct return is the most widely promoted and applied method due to its advantages of simplicity, convenience, speed, labor saving, and the ability to return large quantities of straw. However, direct return also has limitations. A key limitation is the slow decomposition rate and long cycle of straw in the soil, especially under conditions of low temperatures and drought in winter. Uncomposted straw, under the continued decomposition of soil microorganisms, will compete for and consume a large amount of available nitrogen in the soil, thus affecting the growth of subsequent crops. Furthermore, uncomposted straw is prone to carrying crop pathogens and insect eggs, leading to an increase in field diseases and pests. Adding straw composting agents is an effective way to accelerate the straw composting rate. Traditional methods typically use enzyme-producing microbial agents or enzymes as composting agents to accelerate the field composting rate of straw. Direct enzyme addition has the advantages of rapid onset, precision, and high efficiency, and has good application prospects in straw return to the field. However, conventional methods usually involve directly applying enzyme preparations, but enzymes are easily affected by environmental factors such as temperature and pH, which can lead to a decrease in activity and reduce the effectiveness of enzyme action.

[0004] Therefore, there is a need to find a method for preparing straw composting agents to solve the problem that enzymes are easily affected by environmental factors, leading to a decrease in enzyme activity and a reduction in the effectiveness of enzymes in straw composting. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a straw composting agent that promotes decomposition and carbon fixation, and its preparation method, to solve the problem that enzymes are easily affected by environmental factors, leading to a decrease in enzyme activity and a reduction in the effectiveness of enzymes in straw composting.

[0006] The present invention solves the above-mentioned technical problems through the following technical means:

[0007] A straw composting agent that promotes decomposition and carbon sequestration, the composting agent comprising the following raw materials:

[0008] Attapulgite, amidothiourea, compound enzyme, calcium oxide, calcium peroxide, polyethylene glycol, shellac, sodium alginate, calcium chloride, crystalline glycerol, citric acid, sodium citrate, sodium carboxymethyl cellulose, ergothioneine, aspartic acid.

[0009] Furthermore, the composite enzyme is obtained by mixing cellulase, xylanase, and laccase; the mass ratio of cellulase, xylanase, and laccase is 25:25:8.

[0010] Furthermore, the cellulase activity is ≥50u / mg, the xylanase activity is ≥100u / mg, and the laccase activity is ≥10u / mg.

[0011] The present invention also discloses a method for preparing the composting agent, the specific method of which is as follows:

[0012] (1) Wash the attapulgite twice with clean water and dry it at 60℃ for 8-12 hours. Then grind it through a 200-mesh sieve to obtain pretreated attapulgite. Add the pretreated attapulgite to water and stir to disperse it. Then add amidothiourea and adjust the pH to 5.5-6.5. Then heat it to 45-55℃ and stir to react for 4-6 hours. After the reaction is completed, filter to collect the precipitate, wash it 2-3 times with clean water and dry it at 60℃ for 8-12 hours to obtain modified attapulgite.

[0013] (2) After adding the compound enzyme to water and stirring to disperse it, add the modified attapulgite and stir continuously at 150-200 r / min for 2-4 h. Then filter to remove the filtrate and dry at 45℃ for 4-8 h to obtain enzyme-loaded attapulgite.

[0014] (3) Mix shellac and polyethylene glycol and add 10 times the mass of anhydrous ethanol and stir to dissolve. Then add calcium oxide and calcium peroxide, mix evenly and let stand for 10-20 minutes. After filtering to remove the filtrate, dry at 45°C for 40-60 minutes to obtain calcium oxide-calcium peroxide coated microparticles.

[0015] (4) Dissolve sodium alginate in water to prepare a 2-4 wt% sodium alginate solution. Add crystalline glycerol, calcium oxide-calcium peroxide coated microparticles and enzyme-loaded attapulgite to the sodium alginate solution at 4°C and mix evenly. Then drop it into a 2 wt% calcium chloride solution to gel and form composite gel particles with a particle size of 1-2 mm. Dry at 45°C for 3-6 h for later use.

[0016] (5) Prepare a citrate-sodium citrate buffer solution with pH 5, add sodium carboxymethyl cellulose, ergothioneine and aspartic acid and mix evenly to obtain a mixture. Immerse the dried composite gel particles in the mixture and let them stand for 5-8 minutes before taking them out to obtain the composting agent.

[0017] Furthermore, in step (1), the mass ratio of pretreated attapulgite to amidothiourea is (1-2):(0.3-0.6).

[0018] Furthermore, in step (2), the mass ratio of the compound enzyme to the modified attapulgite soil is (0.2-0.4):(1-2).

[0019] Furthermore, in step (3), the mass ratio of shellac, polyethylene glycol, calcium oxide, and calcium peroxide is (0.25-0.5):(0.05-0.1):(0.5-1):(0.5-1).

[0020] Furthermore, in step (4), the mass ratio of sodium alginate solution, crystalline glycerol, calcium oxide-calcium peroxide coated microparticles, and enzyme-loaded attapulgite is (4-8):(0.1-0.2):(1-2):(1-2).

[0021] Furthermore, in step (5), the mass ratio of citrate-sodium citrate buffer, sodium carboxymethyl cellulose, ergothioneine, and aspartic acid is 10:(0.1-0.2):(0.05-0.1):(0.2-0.3).

[0022] This invention uses a composite enzyme consisting of cellulase, xylanase, and laccase as an effective raw material to prepare a decomposing agent that promotes straw decomposition. The cellulase, xylanase, and laccase in the composite enzyme work together to efficiently decompose cellulose, hemicellulose, and lignin in straw, accelerating straw decomposition. However, the composite enzyme requires a higher temperature and a weakly acidic environment to maintain higher activity and achieve better results. Furthermore, laccase is an aerobic enzyme and requires an aerobic environment to function effectively. Therefore, this invention adds calcium peroxide (which releases oxygen through hydrolysis), calcium oxide (which releases heat through hydrolysis), and a citrate-sodium citrate pH buffer to the composite enzyme to prepare the decomposing agent. Sodium alginate gel is used to load the components, utilizing the water-absorbing and water-retaining properties of the sodium alginate gel to ensure the supply of water required for the hydrolysis of calcium peroxide and calcium oxide. The release of oxygen and heat through the hydrolysis of calcium peroxide and calcium oxide increases the temperature and oxygen content during straw decomposition. The citrate-sodium citrate pH buffer ensures a suitable environment for the composite enzyme, thereby enhancing its activity and promoting efficient straw decomposition.

[0023] To ensure the activity of the complex enzyme in the composting agent, this invention uses amidothiourea to treat attapulgite soil, loads the complex enzyme, and then prepares the composting agent together with other components. By coordinating the active sites of amidothiourea with the attapulgite soil, the surface properties and charge density of the soil are adjusted to enhance the hydrogen bonding and electrostatic binding capacity between the soil and the enzyme. This increases the loading rate of the complex enzyme while ensuring that the enzyme loaded in the composting agent can be effectively released and contact the substrate for decomposition after entering the soil, thus guaranteeing the enzyme's effectiveness. Furthermore, the use of electrostatic and hydrogen bonding methods for enzyme loading minimizes enzyme damage. In addition, amidothiourea, once in the soil, can inhibit the conversion of ammonium nitrogen into easily leached nitrate nitrogen, which helps ensure the supply of nitrogen to microorganisms and improves the decomposition efficiency of straw.

[0024] Furthermore, since the waxy layer on the surface of straw can hinder the contact of released enzymes with substrates such as cellulose, this invention adds solid crystalline glycerol during the preparation of the composting agent, embedding it within the sodium alginate gel layer. During the drying process of the composite gel particles, the solid crystalline glycerol melts and flows uniformly dispersed in the composting agent, leaving a porous structure at the original embedding sites. This better ensures that the complex enzymes released from the attapulgite soil can better pass through the sodium alginate gel layer and exert their effects. Simultaneously, the flowing and dispersed glycerol helps maintain the activity of the complex enzymes, further ensuring their effectiveness. When the composting agent is applied to the soil, the glycerol in the composting agent can be released to dissolve the waxy layer on the straw surface, thereby reducing the restriction of the waxy layer on enzyme contact with the substrate.

[0025] However, once the decomposing agent particles enter the soil, they are easily adsorbed by soil particles, inhibiting their contact with the straw substrate. Therefore, this invention further adds aspartic acid to treat the decomposing agent. In a weakly acidic environment with a pH of 5, the decomposing agent particles acquire the same charge as the soil particles, thereby introducing electrostatic repulsion to inhibit the adsorption of the decomposing agent particles by the soil particles. However, since metal ions in the soil particles can combine with aspartic acid to eliminate its electrostatic repulsion effect on the soil particles, this invention further adds ergothioneine. Ergothioneine complexes with metal ions in the soil to eliminate the influence of metal ions on aspartic acid. At the same time, ergothioneine can effectively bind with phenolic free radicals generated by laccase oxidation of lignin, eliminating their adverse effects on cellulase activity. Through the combined action of the components in the decomposing agent, the straw is efficiently decomposed, promoting the transformation of straw into organic matter stored in the soil. This enhances soil carbon sequestration, improves soil fertility, and improves soil properties, thereby promoting the healthy growth of subsequent crops.

[0026] Beneficial effects:

[0027] 1. This invention uses a mixture of cellulase, xylanase, and laccase, which have good decomposition effects on cellulose, hemicellulose, and lignin, to prepare a composting agent as an effective component. The combined action of these enzymes can efficiently compost straw and accelerate the composting efficiency after straw is returned to the field.

[0028] 2. This invention also adds calcium peroxide, which can hydrolyze oxygen, calcium oxide, which releases heat upon hydrolysis, and a citric acid-sodium citrate buffer solution to maintain pH stability to the composting agent, providing a more suitable environment to ensure enzyme activity. This solves the problem that enzymes are easily affected by environmental factors such as environment and pH when entering the soil, leading to reduced activity and affecting their composting effect on straw. The composting agent prepared by this invention has good application prospects. Attached Figure Description

[0029] Figure 1: A picture of the corn stalks before they are fully decomposed;

[0030] Figure 2: A picture showing the condition of corn stalks after composting with the composting agent prepared by the method of the present invention. Detailed Implementation

[0031] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings:

[0032] Example 1: Preparation of composting agent

[0033] (1) Wash the attapulgite twice with clean water and dry it at 60℃ for 10h. Then grind it through a 200-mesh sieve to obtain pretreated attapulgite. Add 1.5kg of pretreated attapulgite to 7.5kg of water and stir to disperse. Then add 0.45kg of amidothiourea and adjust the pH to 6. Then heat the temperature to 50℃ and stir to react for 5h. After the reaction is completed, filter to collect the precipitate, wash it three times with clean water and dry it at 60℃ for 10h to obtain modified attapulgite.

[0034] (2) Add 0.3 kg of compound enzyme to 3 kg of water and stir to disperse. Then add 1.5 kg of modified attapulgite and stir continuously at 180 r / min for 3 h. After filtering to remove the filtrate, dry at 45 °C for 6 h to obtain enzyme-loaded attapulgite.

[0035] (3) Mix 0.4 kg shellac and 0.08 kg polyethylene glycol and add 10 times the mass of anhydrous ethanol and stir to dissolve. Then add 0.8 kg calcium oxide and 0.8 kg calcium peroxide and mix evenly. Let stand for 15 min, filter to remove the filtrate and dry at 45°C for 50 min to obtain calcium oxide-calcium peroxide coated microparticles.

[0036] (4) Dissolve sodium alginate in water to prepare 6 kg of 3wt% sodium alginate solution. Add 0.15 kg of crystalline glycerol, 1.6 kg of calcium oxide-calcium peroxide coated microparticles and 1.5 kg of enzyme-loaded attapulgite to the sodium alginate solution at 4℃ and mix evenly. Then drop it into 2wt% calcium chloride solution to gel and form composite gel particles with a particle size of 1 mm. Dry at 45℃ for 4 h for later use.

[0037] (5) Prepare 10 kg of citrate-sodium citrate buffer solution with pH 5, add 0.15 kg of sodium carboxymethyl cellulose, 0.07 kg of ergothioneine and 0.25 kg of aspartic acid and mix evenly to obtain a mixture. Immerse the dried composite gel particles in the mixture and let them stand for 7 minutes before taking them out to obtain the composting agent.

[0038] Example 2: Preparation of composting agent

[0039] (1) Wash the attapulgite twice with clean water and dry it at 60℃ for 8 hours. Then grind it through a 200-mesh sieve to obtain pretreated attapulgite. Add 1 kg of pretreated attapulgite to 5 kg of water and stir to disperse. Then add 0.3 kg of amidothiourea and adjust the pH to 5.5. Then heat the temperature to 45℃ and stir to react for 6 hours. After the reaction is completed, filter to collect the precipitate, wash it twice with clean water and dry it at 60℃ for 8 hours to obtain modified attapulgite.

[0040] (2) Add 0.2 kg of compound enzyme to 2 kg of water and stir to disperse. Then add 1 kg of modified attapulgite and stir continuously at 150 r / min for 4 h. After filtering to remove the filtrate, dry at 45 °C for 4 h to obtain enzyme-loaded attapulgite.

[0041] (3) Mix 0.25 kg shellac and 0.05 kg polyethylene glycol and add 10 times the mass of anhydrous ethanol and stir to dissolve. Then add 0.5 kg calcium oxide and 0.5 kg calcium peroxide and mix evenly. Let stand for 10 min, filter to remove the filtrate and dry at 45°C for 40 min to obtain calcium oxide-calcium peroxide coated microparticles.

[0042] (4) Dissolve sodium alginate in water to prepare 4 kg of 2wt% sodium alginate solution. Add 0.1 kg of crystalline glycerol, 1 kg of calcium oxide-calcium peroxide coated microparticles and 1 kg of enzyme-loaded attapulgite to the sodium alginate solution at 4℃ and mix evenly. Then drop it into 2wt% calcium chloride solution to gel and form composite gel particles with a particle size of 1 mm. Dry at 45℃ for 3 h for later use.

[0043] (5) Prepare 10 kg of citrate-sodium citrate buffer solution with pH 5, add 0.1 kg of sodium carboxymethyl cellulose, 0.05 kg of ergothioneine and 0.2 kg of aspartic acid and mix evenly to obtain a mixture. Immerse the dried composite gel particles in the mixture and let them stand for 5 min before taking them out to obtain the composting agent.

[0044] Example 3: Preparation of composting agent

[0045] (1) Wash the attapulgite twice with clean water and dry it at 60℃ for 12h. Then grind it through a 200-mesh sieve to obtain pretreated attapulgite. Add 2kg of pretreated attapulgite to 10kg of water and stir to disperse. Then add 0.6kg of amidothiourea and adjust the pH to 6.5. Then heat the temperature to 55℃ and stir to react for 4h. After the reaction is completed, filter to collect the precipitate, wash it three times with clean water and dry it at 60℃ for 12h to obtain modified attapulgite.

[0046] (2) Add 0.4 kg of compound enzyme to 4 kg of water and stir to disperse. Then add 2 kg of modified attapulgite and stir continuously at 200 r / min for 4 h. After filtering to remove the filtrate, dry at 45 °C for 8 h to obtain enzyme-loaded attapulgite.

[0047] (3) Mix 0.5 kg shellac and 0.1 kg polyethylene glycol and add 10 times the mass of anhydrous ethanol and stir to dissolve. Then add 1 kg calcium oxide and 1 kg calcium peroxide and mix evenly. Let stand for 20 min, filter to remove the filtrate and dry at 45°C for 60 min to obtain calcium oxide-calcium peroxide coated microparticles.

[0048] (4) Dissolve sodium alginate in water to prepare 8 kg of 4 wt% sodium alginate solution. Add 0.2 kg of crystalline glycerol, 2 kg of calcium oxide-calcium peroxide coated microparticles and 2 kg of enzyme-loaded attapulgite to the sodium alginate solution at 4 °C and mix evenly. Then drop it into 2 wt% calcium chloride solution to gel and form composite gel particles with a particle size of 2 mm. Dry at 45 °C for 6 h for later use.

[0049] (5) Prepare 10 kg of citrate-sodium citrate buffer solution with pH 5, add 0.2 kg of sodium carboxymethyl cellulose, 0.1 kg of ergothioneine and 0.3 kg of aspartic acid and mix evenly to obtain a mixture. Immerse the dried composite gel particles in the mixture and let them stand for 8 minutes before taking them out to obtain the composting agent.

[0050] Comparative Example 1: Preparation of composting agent

[0051] Compared with Example 1, the only difference is that in Comparative Example 1, the pretreated attapulgite soil was not modified in step (1) during the preparation of the composting agent, as shown below:

[0052] (1) Wash the attapulgite with clean water twice, dry it at 60°C for 10 hours, and then grind it through a 200-mesh sieve to obtain pretreated attapulgite.

[0053] (2) Add 0.3 kg of compound enzyme to 3 kg of water and stir to disperse. Then add 1.5 kg of pretreated attapulgite and stir continuously at 180 r / min for 3 h. After filtering to remove the filtrate, dry at 45 °C for 6 h to obtain enzyme-loaded attapulgite.

[0054] (3) to (5) are the same as in Example 1.

[0055] Comparative Example 2: Preparation of composting agent

[0056] Compared with Example 1, the only difference is that polyethylene glycol is not added in step (3) of the preparation of the composting agent in Comparative Example 2, while the other steps are the same as in Example 1.

[0057] Comparative Example 3: Preparation of composting agent

[0058] Compared with Example 1, the only difference is that crystallized glycerol is not added in step (4) of the preparation of the composting agent in Comparative Example 3, while the other steps are the same as in Example 1.

[0059] Comparative Example 4: Preparation of composting agent

[0060] Compared with Example 1, the only difference is that in the preparation of the composting agent in Comparative Example 4, the original step (3), namely step (4), does not add calcium oxide-calcium peroxide coated particles. All other steps are the same as in Example 1.

[0061] Comparative Example 5: Preparation of composting agent

[0062] Compared with Example 1, the only difference is that ergothioneine was not added in step (5) of the preparation of the composting agent in Comparative Example 5, and the other steps are the same as in Example 1.

[0063] Comparative Example 6: Preparation of composting agent

[0064] Compared with Example 1, the only difference is that aspartic acid was not added in step (5) of the preparation of the composting agent in Comparative Example 6, while the other steps are the same as in Example 1.

[0065] Experiment: Test on the effect of composting agents

[0066] A straw decomposition experiment was conducted in Changwu County, Shaanxi Province in April 2025. The experiment consisted of 8 groups: Example 1, Comparative Examples 1-6, and a blank control. The selected experimental site had previously been planted with corn and had already been harvested. An area was designated as the experimental zone, and within the experimental zone, 8 equal small areas were divided, each with an area of ​​1×1m. Corn straw was then crushed to a particle size of 5cm and evenly spread on the soil surface of each small area at a rate of 250g. Then, 100g of the corresponding decomposition agent was evenly spread on each small area. After the operation was completed, the straw with the decomposition agent was turned into the soil at a depth of 5cm. The blank control group was not treated with decomposition agent but was treated with an equal amount of water. After 60 days, the straw decomposition rate in the soil of each area was measured (decomposition rate = (initial straw mass - straw residue after 60 days) / initial straw mass × 100%). The organic matter content in the soil was measured before and after the experiment, and the increase rate of soil organic matter content was calculated. The average data from three repeated experiments are shown in Table 1.

[0067] Table 1

[0068]

[0069] Based on the data analysis in Table 1, we can conclude that:

[0070] (1) In Example 1, the straw with the decomposition agent of the present invention decomposed at a rate of 87.6% after 60 days, while the straw in the blank control group without the decomposition agent decomposed at a rate of only 62.2%. The decomposition rate of Example 1 increased by 25.4% compared with the blank control. The soil organic matter content increased by 31.8% in Example 1, while the soil organic matter content increased by only 23.8% in the blank control group. This shows that the method of the present invention can effectively accelerate the decomposition efficiency of straw after returning it to the field, improve the soil carbon sequestration capacity, and increase the soil organic matter content.

[0071] (2) In Comparative Example 1, the attapulgite soil was not modified during the preparation of the straw decomposing agent. The poor loading effect of the attapulgite soil on the enzyme affected the effect of the decomposing agent. In Comparative Example 2, polyethylene glycol was not added to coat calcium oxide and calcium peroxide during the preparation of the straw decomposing agent. Instead, shellac was used for coating. The poor water permeability of the membrane layer resulted in poor heating and oxygen release effects of calcium oxide and calcium peroxide, which limited the effect on improving enzyme activity and resulted in poor straw decomposition. In Comparative Example 3, crystalline glycerol was not added during the preparation of the straw decomposing agent. On the one hand, it failed to enhance the accessibility of the enzyme to the substrate, and on the other hand, it reduced the enzyme activity, thereby reducing the effect of the enzyme and causing decomposition. The decomposition rate decreased. In Comparative Example 4, no calcium oxide-calcium peroxide coated microparticles were added during the preparation of the straw decomposition agent. The lack of the warming and oxygenating effects of calcium oxide and calcium peroxide greatly reduced enzyme activity, resulting in a significant decrease in the decomposition rate. In Comparative Example 5, no ergothioneine was added during the preparation of the straw decomposition agent. On the one hand, it failed to reduce the influence of phenolic free radicals generated by laccase oxidation of lignin on the activity of cellulase. On the other hand, it failed to complex metal ions in the soil, affecting the contact between the enzyme and the substrate, thus reducing the decomposition rate. In Comparative Example 6, no aspartic acid was added during the preparation of the straw decomposition agent. The adsorption of the decomposition agent by soil particles limited the contact between the enzyme and the substrate, thus leading to a decrease in the decomposition rate.

[0072] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.

Claims

1. A straw composting agent that promotes decomposition and carbon sequestration, characterized in that, The composting agent comprises the following raw materials: Attapulgite, amidothiourea, compound enzyme, calcium oxide, calcium peroxide, polyethylene glycol, shellac, sodium alginate, calcium chloride, crystalline glycerol, citric acid, sodium citrate, sodium carboxymethyl cellulose, ergothioneine, aspartic acid.

2. The straw composting agent for promoting decomposition and carbon fixation according to claim 1, characterized in that, The complex enzyme is obtained by mixing cellulase, xylanase, and laccase; the mass ratio of cellulase, xylanase, and laccase is 25:25:

8.

3. The straw composting agent for promoting decomposition and carbon fixation according to claim 2, characterized in that, The cellulase activity is ≥50u / mg, the xylanase activity is ≥100u / mg, and the laccase activity is ≥10u / mg.

4. A method for preparing a straw composting agent that promotes decomposition and carbon fixation, characterized in that, The preparation method of the composting agent is as follows: (1) Wash the attapulgite with clean water twice and dry it at 60℃ for 8-12 hours. Then grind it through a 200-mesh sieve to obtain pretreated attapulgite. Add the pretreated attapulgite to water and stir to disperse it. Then add amidothiourea and adjust the pH to 5.5-6.

5. Then heat it to 45-55℃ and stir to react for 4-6 hours. After the reaction is completed, filter to collect the precipitate, wash it with clean water 2-3 times, and dry it at 60℃ for 8-12 hours to obtain modified attapulgite; (2) Add the compound enzyme to water and stir to disperse it. Then add the modified attapulgite and stir continuously at 150-200 r / min for 2-4 hours. Then filter to remove the filtrate and dry it at 45℃ for 4-8 hours to obtain enzyme-loaded attapulgite; (3) Mix shellac and polyethylene glycol and add it to 10 times the mass of anhydrous ethanol and stir to dissolve it. After adding calcium oxide and calcium peroxide and mixing evenly, let stand for 10-20 minutes, filter to remove the filtrate and dry at 45°C for 40-60 minutes to obtain calcium oxide-calcium peroxide coated microparticles; (4) Dissolve sodium alginate in water to prepare a 2-4 wt% sodium alginate solution, add crystalline glycerol, calcium oxide-calcium peroxide coated microparticles and enzyme-loaded attapulgite to the sodium alginate solution at 4°C and mix evenly, then drop it into a 2 wt% calcium chloride solution to gel and form composite gel particles with a particle size of 1-2 mm, and dry at 45°C for 3-6 hours for later use; (5) Prepare a citrate-sodium citrate buffer solution with pH 5, add sodium carboxymethyl cellulose, ergothioneine and aspartic acid and mix evenly to obtain a mixed solution, immerse the dried composite gel particles in the mixed solution and let stand for 5-8 minutes, then take them out to obtain a composting agent.

5. The method for preparing a straw composting agent for promoting decomposition and carbon fixation according to claim 4, characterized in that, In step (1), the mass ratio of pretreated attapulgite soil to amidothiourea is (1-2):(0.3-0.6).

6. The method for preparing a straw composting agent for promoting decomposition and carbon fixation according to claim 5, characterized in that, In step (2), the mass ratio of the compound enzyme to the modified attapulgite soil is (0.2-0.4):(1-2).

7. The method for preparing a straw composting agent for promoting decomposition and carbon fixation according to claim 6, characterized in that, In step (3), the mass ratio of shellac, polyethylene glycol, calcium oxide, and calcium peroxide is (0.25-0.5):(0.05-0.1):(0.5-1):(0.5-1).

8. The method for preparing a straw composting agent for promoting decomposition and carbon fixation according to claim 7, characterized in that, In step (4), the mass ratio of sodium alginate solution, crystalline glycerol, calcium oxide-calcium peroxide coated microparticles, and enzyme-loaded attapulgite clay is (4-8):(0.1-0.2):(1-2):(1-2).

9. The method for preparing a straw composting agent for promoting decomposition and carbon fixation according to claim 8, characterized in that, In step (5), the mass ratio of citrate-sodium citrate buffer, sodium carboxymethyl cellulose, ergothioneine, and aspartic acid is 10:(0.1-0.2):(0.05-0.1):(0.2-0.3).

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