Preparation method and application of composite biochar

Abstract

The invention provides a preparation method and application of composite biochar, and belongs to the technical field of biochar, the preparation method comprises the following steps: S1, mixing yak dung and highland barley straw, and crushing; s2, sodium hydroxide is added into the mixture for alkaline hydrolysis, then cellulase is added for enzyme hydrolysis, supernate is removed, quick lime is added into sediment, stirring and desulfurization are conducted, and a first mixture is obtained; s3, the pH of the first mixture acid solution is adjusted to be neutral, yak manure incineration ash is added, and a second mixture is obtained through dehydration; and S4, granulating the dehydrated second mixture, and drying to obtain the composite biochar. According to the method, ultrasonic-assisted dilute alkali hydrolysis and cellulase hydrolysis are combined for carbonization, high-temperature carbonization is not needed, yak manure incineration ash is adopted as a binder, on one hand, granulation of yak manure and highland barley straw is facilitated, and meanwhile potassium salt nutrition can be supplemented for soil due to the fact that the main component of the yak manure incineration ash is potassium carbonate; and the added phosphoric acid can also provide phosphorus nutrients for the soil.

Description

Technical Field

[0001] The present invention relates to the technical field of biochar, and in particular to a preparation method of composite biochar and application thereof. Background Art

[0002] Fertilization system is the basis for determining soil quality and sustainable productivity and stability of farmland ecosystems. Over the past half century, with the increasing demand for crop yields, the demand for chemical fertilizers has also increased, and the disadvantages of long-term and large-scale application of chemical fertilizers (such as decreased utilization rate, decreased quality of agricultural products, soil compaction, acidification, imbalance of biodiversity and environmental pollution) have gradually become apparent. China is rich in organic fertilizer resources, mainly livestock and poultry manure, crop straw and green manure, but the resource utilization rate is low. Every year, 2 / 3 of organic waste is abandoned and wasted, seriously endangering the environment. A large number of studies have shown that the application of organic fertilizers or a combination of organic and inorganic fertilizers can not only improve soil fertility and increase crop yields, but also effectively alleviate the environmental pollution caused by the large-scale application of chemical fertilizers.

[0003] Biochar is an economically feasible way to fix carbon dioxide. When applied to the soil, it will not change for thousands of years. While producing renewable energy, it also improves soil fertility and increases crop yields. The application of biochar is also beneficial to improving soil drainage systems and sealing about 80% of greenhouse gases such as nitric oxide and methane in the soil, preventing them from being emitted into the atmosphere. Biochar is made by heating biomass (such as wood, manure or crop residues) in a closed container (under anaerobic conditions). Biochar can improve agriculture and the environment in a variety of ways. Its stability in the soil and excellent nutrient retention capacity make it an ideal soil conditioner. In addition, the sequestration capacity of biochar combined with sustainable biomass production can reduce carbon dioxide emissions in the atmosphere, which has an important impact on mitigating climate change and achieving carbon peak and carbon neutrality as soon as possible.

[0004] Cow dung has the characteristics of stable source and single property. Cow dung biochar is used as a crop planting matrix. Existing cow dung biochar is all produced by high-temperature hydrothermal carbonization. Currently, there is no method for preparing biochar from cow dung without high-temperature carbonization. Therefore, it is very necessary to provide a method for preparing composite biochar for crop planting matrix. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a preparation method and application of composite biochar, which does not require high-temperature carbonization and uses yak dung incineration ash as a binder. On the one hand, it is convenient for yak dung and highland barley straw to be granulated. At the same time, because its main component is potassium carbonate, it can supplement potassium salt nutrition for the soil; the added phosphoric acid can also provide phosphorus nutrients for the soil; and the mixture after granulation is convenient for full mixing with soil particles, and it can be applied alone or in combination with fertilizers such as chemical fertilizers.

[0006] The technical solution adopted by the present invention is:

[0007] A method for preparing composite biochar, comprising the following steps:

[0008] Step S1. Mixing naturally dried yak dung and harvested barley straw, and sending the mixture into a crushing machine to crush it to a particle size of 0.5-1 mm;

[0009] Step S2. adding the crushed mixture to a sodium hydroxide solution and adjusting the pH to 10.5-10.8 for alkaline hydrolysis, then adding cellulase for enzymatic hydrolysis, removing the supernatant, retaining the precipitate, adding quicklime to the precipitate and stirring evenly, and then reacting for 10-30 minutes for desulfurization to obtain a first mixture;

[0010] Step S3. taking out the first mixture after desulfurization, and adding an acid solution to adjust the pH to neutral, then adding yak dung incineration ash to the first mixture, mixing evenly and sending it to a dehydration device for dehydration until the moisture content is less than 50%, to obtain a second mixture;

[0011] Step S4: sending the dehydrated second mixture to a granulation device for granulation, and bagging after drying to obtain composite biochar.

[0012] Preferably, in the method for preparing composite biochar, the weight ratio of yak dung to harvested barley straw in step S1 is 1-10:1-5.

[0013] Preferably, in the method for preparing composite biochar, the concentration of the sodium hydroxide solution in step S2 is 5-10%, and the mass ratio of the mixture to the sodium hydroxide solution is 1:10-20.

[0014] Preferably, in the method for preparing composite biochar, the alkaline hydrolysis temperature of the mixture in step S2 is 55-65° C., and the alkaline hydrolysis is carried out at a constant temperature for 0.5-0.7 h with the assistance of ultrasound.

[0015] Preferably, in the method for preparing composite biochar, the amount of cellulase added in step S2 is 3-5% of the weight of the mixture, the enzyme hydrolysis time is 15-20 hours, and the amount of quicklime added is 1-2% of the weight of the mixture.

[0016] Preferably, in the method for preparing composite biochar, the acid solution in step S3 is a phosphoric acid solution.

[0017] Preferably, in the method for preparing composite biochar, the amount of yak dung incineration ash added in step S3 is 10-15% of the weight of the first mixture.

[0018] Preferably, in the method for preparing the composite biochar, the particle size after granulation in step S4 is 0.3-0.5 cm.

[0019] A composite biochar prepared according to a preparation method.

[0020] The invention discloses an application of composite biochar in preparing a crop planting matrix.

[0021] Advantages of the present invention:

[0022] (1) The preparation method of the composite biochar of the present invention uses ultrasound-assisted alkaline hydrolysis to quickly hydrolyze the lignocellulose in yak dung and highland barley straw. The dilute alkali pretreatment can effectively de-lignify, reduce the non-functional adsorption of lignin and cellulase, and improve the enzymatic hydrolysis efficiency of plant straw.

[0023] (2) The preparation method of the composite biochar of the present invention combines ultrasound-assisted dilute alkali hydrolysis and cellulase hydrolysis for carbonization, does not require high-temperature carbonization, and uses yak dung incineration ash as a binder. On the one hand, it is convenient for yak dung and highland barley straw to be granulated. At the same time, because its main component is potassium carbonate, it can supplement potassium salt nutrition for the soil; the added phosphoric acid can also provide phosphorus nutrients for the soil; and the mixture after granulation is easy to be fully mixed with soil particles. It can be applied alone or in combination with fertilizers such as chemical fertilizers. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific embodiments.

[0025] Example 1

[0026] A method for preparing composite biochar, comprising the following steps:

[0027] Step S1. Mix naturally dried yak dung and harvested barley straw, with the weight ratio of yak dung to harvested barley straw being 1:1; and send the mixture into a crushing machine to crush it to a particle size of 0.5 mm;

[0028] Step S2. adding the crushed mixture to a 10% sodium hydroxide solution, adjusting the pH to 10.5 for alkaline hydrolysis, wherein the mass ratio of the mixture to the sodium hydroxide solution is 1:10, the alkaline hydrolysis temperature is 60°C, and the alkaline hydrolysis is carried out at a constant temperature for 0.5h under the assistance of ultrasound, and then adding cellulase for enzymatic hydrolysis, removing the supernatant, retaining the precipitate, the amount of cellulase added is 3% of the weight of the mixture, the enzymatic hydrolysis time is 20h, adding quicklime to the precipitate and stirring evenly, the amount of quicklime added is 1% of the weight of the mixture, and then reacting for 20min for desulfurization to obtain a first mixture;

[0029] Step S3. Take out the first mixture after desulfurization, add phosphoric acid solution to adjust the pH to neutral, then add yak dung incineration ash to the first mixture, the amount of yak dung incineration ash added is 12% of the weight of the first mixture, mix well and send to dehydration equipment for dehydration, dehydrate to a moisture content of less than 50%, and obtain a second mixture;

[0030] Step S4. The dehydrated second mixture is sent to a granulation device for granulation. The particle size after granulation is 0.3 cm. After drying to a moisture content of less than 15%, the mixture is bagged to obtain composite biochar.

[0031] Example 2

[0032] A method for preparing composite biochar, comprising the following steps:

[0033] Step S1. Mix naturally dried yak dung and harvested barley straw, with the weight ratio of yak dung to harvested barley straw being 1:1; and send the mixture into a crushing machine to crush it to a particle size of 0.5-1 mm;

[0034] Step S2. adding the crushed mixture to a 10% sodium hydroxide solution, adjusting the pH to 10.5 for alkaline hydrolysis, wherein the mass ratio of the mixture to the sodium hydroxide solution is 1:10, the alkaline hydrolysis temperature is 60°C, and the alkaline hydrolysis is carried out at a constant temperature for 0.5h under the assistance of ultrasound, and then adding cellulase for enzymatic hydrolysis, removing the supernatant, retaining the precipitate, the amount of cellulase added is 4% of the weight of the mixture, the enzymatic hydrolysis time is 20h, quicklime is added to the precipitate and stirred evenly, the amount of quicklime added is 2% of the weight of the mixture, and then reacting for 20min for desulfurization to obtain a first mixture;

[0035] Step S3. Take out the first mixture after desulfurization, add phosphoric acid solution to adjust the pH to neutral, then add yak dung incineration ash to the first mixture, the amount of yak dung incineration ash added is 10% of the weight of the first mixture, mix well and send to dehydration equipment for dehydration, dehydrate until the water content is less than 50%, and obtain a second mixture;

[0036] Step S4. The dehydrated second mixture is sent to a granulation device for granulation. The particle size after granulation is 0.3 cm. After drying to a moisture content of less than 15%, the mixture is bagged to obtain composite biochar.

[0037] Example 3

[0038] A method for preparing composite biochar, comprising the following steps:

[0039] Step S1. Mix naturally dried yak dung and harvested barley straw, with the weight ratio of yak dung to harvested barley straw being 1:1; and send the mixture into a crushing machine to crush it to a particle size of 0.5 mm;

[0040] Step S2. adding the crushed mixture to a 10% sodium hydroxide solution, adjusting the pH to 10.5 for alkaline hydrolysis, wherein the mass ratio of the mixture to the sodium hydroxide solution is 1:10, the alkaline hydrolysis temperature is 60°C, and the alkaline hydrolysis is carried out at a constant temperature for 0.5h under the assistance of ultrasound, and then adding cellulase for enzymatic hydrolysis, removing the supernatant, retaining the precipitate, the amount of cellulase added is 5% of the weight of the mixture, the enzymatic hydrolysis time is 20h, quicklime is added to the precipitate and stirred evenly, the amount of quicklime added is 2% of the weight of the mixture, and then reacting for 20min for desulfurization to obtain a first mixture;

[0041] Step S3. Take out the first mixture after desulfurization, add phosphoric acid solution to adjust the pH to neutral, then add yak dung incineration ash to the first mixture, the amount of yak dung incineration ash added is 10% of the weight of the first mixture, mix well and send to dehydration equipment for dehydration, dehydrate until the water content is less than 50%, and obtain a second mixture;

[0042] Step S4. The dehydrated second mixture is sent to a granulation device for granulation. The particle size after granulation is 0.3 cm. After drying to a moisture content of less than 15%, the mixture is bagged to obtain composite biochar.

[0043] Comparative Example 1

[0044] A method for preparing composite biochar, comprising the following steps:

[0045] Step S1. Mix naturally dried yak dung and harvested barley straw, with the weight ratio of yak dung to harvested barley straw being 1:1; and send the mixture into a crushing machine to crush it to a particle size of 0.5 mm;

[0046] Step S2. Add cellulase to the crushed mixture for enzymatic hydrolysis, remove the supernatant, retain the precipitate, the amount of cellulase added is 3% of the weight of the mixture, the enzymatic hydrolysis time is 20 hours, add quicklime to the precipitate and stir evenly, the amount of quicklime added is 1% of the weight of the mixture, and then react for 20 minutes for desulfurization to obtain a first mixture;

[0047] Step S3. Take out the first mixture after desulfurization, add phosphoric acid solution to adjust the pH to neutral, then add yak dung incineration ash to the first mixture, the amount of yak dung incineration ash added is 12% of the weight of the first mixture, mix well and send to dehydration equipment for dehydration, dehydrate to a moisture content of less than 50%, and obtain a second mixture;

[0048] Step S4. The dehydrated second mixture is sent to a granulation device for granulation. The particle size after granulation is 0.3 cm. After drying to a moisture content of less than 15%, the mixture is bagged to obtain composite biochar.

[0049] Comparative Example 2

[0050] A method for preparing composite biochar, comprising the following steps:

[0051] Step S1. Mix naturally dried yak dung and harvested barley straw, with the weight ratio of yak dung to harvested barley straw being 1:1; and send the mixture into a crushing machine to crush it to a particle size of 0.5-1 mm;

[0052] Step S2. adding the crushed mixture to a 10% sodium hydroxide solution, adjusting the pH to 10.5 for alkaline hydrolysis, wherein the mass ratio of the mixture to the sodium hydroxide solution is 1:10, the alkaline hydrolysis temperature is 60°C, and the alkaline hydrolysis is carried out at a constant temperature for 0.5h under the assistance of ultrasound, and then adding cellulase for enzymatic hydrolysis, removing the supernatant, retaining the precipitate, the amount of cellulase added is 4% of the weight of the mixture, the enzymatic hydrolysis time is 20h, quicklime is added to the precipitate and stirred evenly, the amount of quicklime added is 2% of the weight of the mixture, and then reacting for 20min for desulfurization to obtain a first mixture;

[0053] Step S3. taking out the first mixture after desulfurization, adding phosphoric acid solution to adjust the pH to neutral, sending it to a dehydration device for dehydration until the water content is less than 50%, and obtaining a second mixture;

[0054] Step S4. The dehydrated second mixture is sent to a granulation device for granulation. The particle size after granulation is 0.3 cm. After drying to a moisture content of less than 15%, the mixture is bagged to obtain composite biochar.

[0055] Comparative Example 3

[0056] A method for preparing composite biochar, comprising the following steps:

[0057] Step S1. Mix naturally dried yak dung and harvested barley straw, with the weight ratio of yak dung to harvested barley straw being 1:1; and send the mixture into a crushing machine to crush it to a particle size of 0.5 mm;

[0058] Step S2. adding the crushed mixture to a 10% sodium hydroxide solution, adjusting the pH to 10.5 for alkaline hydrolysis, wherein the mass ratio of the mixture to the sodium hydroxide solution is 1:10, the alkaline hydrolysis temperature is 60°C, and the alkaline hydrolysis is carried out at a constant temperature for 0.5h under the assistance of ultrasound, and then adding cellulase for enzymatic hydrolysis, removing the supernatant, retaining the precipitate, the amount of cellulase added is 5% of the weight of the mixture, the enzymatic hydrolysis time is 20h, quicklime is added to the precipitate and stirred evenly, the amount of quicklime added is 2% of the weight of the mixture, and then reacting for 20min for desulfurization to obtain a first mixture;

[0059] Step S3. taking out the first mixture after desulfurization, and then adding yak dung incineration ash to the first mixture, wherein the amount of yak dung incineration ash added is 10% of the weight of the first mixture, mixing well, and then sending it to a dehydration device for dehydration, dehydrating until the moisture content is less than 50%, to obtain a second mixture;

[0060] Step S4. The dehydrated second mixture is sent to a granulation device for granulation. The particle size after granulation is 0.3 cm. After drying to a moisture content of less than 15%, the mixture is bagged to obtain composite biochar.

[0061] The performance test results of Examples 1-3 and Comparative Examples 1-3 are listed below, as shown in Table 1.

[0062] Table 1

[0063]

[0064] As can be seen from Table 1, the use of yak dung incineration ash as a binder, because its main component is potassium carbonate, can supplement potassium salt nutrition for the soil, and the added phosphoric acid can also provide phosphorus nutrients for the soil. The carbon content, nitrogen content, phosphorus content and potassium content of Examples 1-3 are better than those of Comparative Examples 1-3.

[0065] The composite biochar prepared in Example 3 was applied to the wheat seedling medium to compare the effects. Different proportions of biochar were set to replace the conventional wheat seedling medium. The specific treatments were as follows: B: 100% composite biochar; M2B8: 20% conventional wheat medium + 80% composite biochar; M4B6: 40% conventional wheat medium + 60% composite biochar; M6B4: 60% conventional wheat medium + 40% composite biochar; M8B2: 80% conventional wheat medium + 20% composite biochar; M: 100% conventional wheat medium; Three parallel experiments were carried out for each treatment. The seedling container used was a 50-hole plug tray, one seed was sown in each hole, and 50 plants were sown in each plug tray. Clear water was continuously poured from sowing to the end of seedling raising. The germination rate was counted from the second day. The growth indexes, physiological indexes and germination quality were measured 35 days after germination. The final results are shown in Table 2.

[0066] Table 2

[0067]

[0068]

[0069] It can be seen from Table 2 that there is no obvious difference in the growth of wheat seedlings when different proportions of composite biochar are replaced. The wheat seedlings treated with 100% composite biochar can still grow normally. This shows that composite biochar is rich in nutrients and can supply the nutrients needed for the growth of wheat seedlings. Compared with conventional wheat seedling substrates, it can reduce the input of fertilizer nutrients in the substrate.

[0070] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing composite biochar, characterized in that: The following steps are involved: Step S1. Mixing naturally dried yak dung and harvested barley straw, and sending the mixture into a crushing machine to crush it to a particle size of 0.5-1 mm; Step S2. adding the crushed mixture to a sodium hydroxide solution and adjusting the pH to 10.5-10.8 for alkaline hydrolysis, then adding cellulase for enzymatic hydrolysis, removing the supernatant, retaining the precipitate, adding quicklime to the precipitate and stirring evenly, and then reacting for 10-30 minutes for desulfurization to obtain a first mixture; Step S3. taking out the first mixture after desulfurization, and adding an acid solution to adjust the pH to neutral, then adding yak dung incineration ash to the first mixture, mixing evenly and sending it to a dehydration device for dehydration until the moisture content is less than 50%, to obtain a second mixture; Step S4: sending the dehydrated second mixture to a granulation device for granulation, and bagging after drying to obtain composite biochar.

2. The method for preparing composite biochar according to claim 1, characterized in that: In step S1, the weight ratio of yak dung to harvested highland barley straw is 1-10:1-5.

3. The method for preparing composite biochar according to claim 1, characterized in that: The concentration of the sodium hydroxide solution in step S2 is 5-10%, and the mass ratio of the mixture to the sodium hydroxide solution is 1:10-20.

4. The method for preparing composite biochar according to claim 1, characterized in that: The alkaline hydrolysis temperature of the mixture in step S2 is 55-65° C., and the alkaline hydrolysis is carried out at a constant temperature for 0.5-0.7 h under the assistance of ultrasound.

5. The method for preparing composite biochar according to claim 1, characterized in that: The amount of cellulase added in step S2 is 3-5% of the weight of the mixture, the enzyme hydrolysis time is 15-20 hours, and the amount of quicklime added is 1-2% of the weight of the mixture.

6. The method for preparing composite biochar according to claim 1, characterized in that: The acid solution in step S3 is a phosphoric acid solution.

7. The method for preparing composite biochar according to claim 1, characterized in that: In step S3, the amount of yak dung incineration ash added is 10-15% of the weight of the first mixture.

8. The method for preparing composite biochar according to claim 1, characterized in that: The particle size after granulation in step S4 is 0.3-0.5 cm.

9. A composite biochar prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the composite biochar as claimed in claim 9 in preparing a crop planting matrix.

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