Modified charcoal-based organic fertilizer and preparation method thereof

Abstract

The invention discloses a modified charcoal-based organic fertilizer and a preparation method thereof, and relates to the technical field of livestock and poultry manure compost, the organic fertilizer is composed of livestock and poultry manure, compost auxiliary materials and hydrogen peroxide modified charcoal; the hydrogen peroxide modified biochar is prepared by uniformly mixing straw biochar and a 5% hydrogen peroxide solution in a ratio of 1: 10; the livestock manure is fresh chicken manure; the compost auxiliary material is bagasse. A preparation method; mixing livestock and poultry manure with the compost auxiliary material to obtain an initial compost material; and adding the hydrogen peroxide modified charcoal into the initial compost material, and stirring and mixing to obtain the aerobic compost material. And performing aerobic composting on the aerobic composting material by adopting a fermentation tank with a ventilated bottom, wherein the composting time is 35 days. The hydrogen peroxide modified biochar is used, so that the heavy metal passivation effect is improved, N2O gas emission is reduced, the nutrient content and the organic matter content of a pile body are increased, and the quality of the organic fertilizer is improved.

Description

Technical Field

[0001] The invention relates to the technical field of livestock and poultry manure composting, and in particular to a modified biochar-based organic fertilizer capable of enhancing the passivation of heavy metals in chicken manure and reducing nitrous oxide emissions, and a preparation method thereof. Background Art

[0002] In livestock and poultry farming, additives containing heavy metal elements are added to prevent animal diseases, resulting in a large amount of heavy metal elements such as copper, zinc, lead, and cadmium in the solid manure of livestock and poultry. If applied to the soil, it will lead to the accumulation of heavy metal elements in the soil, causing heavy metal enrichment in agricultural products, and ultimately threatening human health. Aerobic composting is the most economical and effective way to achieve the reduction, harmlessness, and resource utilization of livestock and poultry manure. It can transform the more active heavy metal forms into less active forms and reduce heavy metal pollution. However, a large amount of gas will be generated and released during the composting process, including: CO 2 , CH 4 、N 2 O, H 2 S, etc., where N 2 O emission is not only one of the gaseous loss pathways of nitrogen in composting materials, but also an important source of atmospheric greenhouse gas emissions.

[0003] In recent years, research on the effects of biochar on the physical and chemical parameters and composting process has attracted more and more attention. Biochar itself contains mineral elements such as potassium, calcium, and magnesium, which can be released into the soil as a nutrient source and absorbed and utilized by crops and microorganisms. However, the content of these mineral elements in biochar is not high. The input of single biochar has limitations in improving soil quality. Therefore, using biochar as a carrier to develop biochar-based fertilizers has become a research hotspot.

[0004] At present, the quality of biochar-based organic fertilizers in the prior art varies, and their quality and application effect are affected by factors such as biochar raw material type, pyrolysis temperature, biochar dosage, manufacturing process, nutrient ratio, etc. To this end, the present invention aims to provide a modified biochar-based organic fertilizer and a preparation method thereof. Summary of the invention

[0005] The purpose of the present invention is to solve the above problems and provide a modified biochar-based organic fertilizer and a preparation method thereof.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] The present invention provides a modified biochar-based organic fertilizer, which is composed of the following components, measured in parts by weight:

[0008] 5-10 parts of livestock and poultry manure, 2-4 parts of composting materials and 2-4 parts of hydrogen peroxide modified biochar;

[0009] The hydrogen peroxide modified biochar is prepared by uniformly mixing straw biochar and 5% hydrogen peroxide solution at a ratio of 1:10; the livestock and poultry manure is fresh chicken manure; and the composting auxiliary material is bagasse.

[0010] Furthermore, the organic fertilizer is composed of the following components, in parts by weight:

[0011] 5 parts of livestock and poultry manure, 2 parts of composting auxiliary materials and 2 parts of hydrogen peroxide modified biochar.

[0012] Furthermore, the organic fertilizer is composed of the following components, in parts by weight:

[0013] 10 parts of livestock and poultry manure, 4 parts of composting auxiliary materials and 4 parts of hydrogen peroxide modified biochar.

[0014] Furthermore, the organic fertilizer is composed of the following components, in parts by weight:

[0015] 7 parts of livestock and poultry manure, 3 parts of composting auxiliary materials and 3 parts of hydrogen peroxide modified biochar.

[0016] The present invention also provides a method for preparing modified biochar-based organic fertilizer, comprising the following steps:

[0017] S1. Biochar preparation

[0018] Take wheat straw, crush it with a crusher, spread the crushed wheat straw evenly in a quartz boat, put it into a tube furnace, and heat it in N at a flow rate of 20 mL / min. 2 In the atmosphere, the temperature was raised to the set temperature of 500°C at a rate of 10°C / min, and pyrolysis was performed for 4 hours. After the pyrolysis was completed, the charcoal was cooled to room temperature and taken out to obtain straw biochar.

[0019] S2, H 2 O 2 Preparation of modified biochar

[0020] The sieved straw biochar and 5% hydrogen peroxide solution were uniformly mixed at a ratio of 1:10, placed in a constant temperature shaker at 30°C and shaken at a speed of 180r / min for 6h, taken out, solid-liquid separation was performed, and the mixture was repeatedly rinsed with deionized water until the filtrate was close to neutral, and the solid was placed in an oven at 70°C and dried to constant weight; and stored in a sealed bag for later use;

[0021] S3. Preparation of compost

[0022] A. Material preparation

[0023] Livestock and poultry manure: Use fresh chicken manure no older than 3 days with a moisture content of 80%;

[0024] Bagasse: air-dried and crushed into small pieces of 2-3 cm in length, with a moisture content of 30%;

[0025] B. Preparation of compost

[0026] The livestock and poultry manure was used as the raw material, and bagasse was used as the conditioning agent. The conditioning agent and livestock and poultry manure were mixed, and the moisture content was adjusted to about 65%, and the C / N ratio was between 20:1 and 30:1. After adding modified biochar, the mixture was evenly mixed. The modified biochar addition ratio was 10%. The unmodified biochar was used as the control treatment group, and the mixture was loaded into a 60L composting fermentation tank for aerobic composting experiment. A temperature probe was inserted into the upper part to monitor the temperature change of the pile. The temperature was set to be measured every 10 minutes. Intermittent ventilation was used, and the ventilation rate was set to 0.4N·kg / h. The temperature was ventilated for 30 minutes per hour and paused for 30 minutes. Each group of piles was manually turned on the 3rd, 7th, 14th, 21st, and 28th days, and the composting cycle was 35 days.

[0027] S4. Collection and determination of heavy metal samples

[0028] Compost samples were collected on the 0th and 35th days after the start of composting, mixed evenly, air-dried, crushed and sieved for the determination of the total amount of heavy metals and various metal forms including oxidized state, exchangeable state, reduced state and residual state;

[0029] S5. N in the composting process 2 O gas collection and determination

[0030] Starting from the first day of composting, gas collection began at 9 a.m. every day until the end of composting; 15 minutes before gas collection, the gas outlet of the fermenter was blocked with a wooden plug. When gas collection was performed, the wooden plug was pulled out, and the three-way valve in front of the 25 ml needle was connected to the three-way valve at the gas outlet. Before extracting gas, the needle piston was pushed and pulled to evenly mix the gas in the fermenter before gas collection. The first tube of gas collected from each tank was discarded, and the gas collected in the needle was pumped into the gas collection tube. Three tubes of gas were extracted from each fermenter for processing as a repeat, and a gas chromatograph was used to analyze N 2 O content was measured.

[0031] Furthermore, the compost samples in step S4 are collected from at least 6 points.

[0032] Furthermore, in step S3, the following three processing groups are set in B:

[0033] CK treatment group; chicken manure + bagasse;

[0034] BC treatment group: chicken manure + bagasse + unmodified biochar;

[0035] OBC treatment group: chicken manure + bagasse + H 2 O 2 Modified biochar.

[0036] The difficulty and significance of the technical problem solved by the present invention are:

[0037] At present, the quality of biochar-based organic fertilizers varies, and its quality and application effect are affected by factors such as biochar raw material type, pyrolysis temperature, biochar dosage, manufacturing process, nutrient ratio, etc. Therefore, the invention of this application provides a modified biochar-based organic fertilizer and a preparation method thereof by conducting technical research on the reduction and control of major pollutants in the composting process and the preparation of high-quality biochar-based organic fertilizers, which is of great significance for effectively preventing and controlling heavy metal pollution in organic fertilizer source soils and reducing greenhouse gas emissions.

[0038] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. H prepared in the novel method of the present invention 2 O 2 Adding modified biochar to chicken manure compost can effectively improve the passivation effect of heavy metals and reduce N 2 The emission of O gas promotes the nitrogen retention process.

[0040] 2. The new method of the present invention not only improves the passivation effect of heavy metals and reduces N 2 The gas emission of O can also increase the seed germination index during the composting process, which can better promote seed germination. At the end of composting, the nutrient content and organic matter content of the pile are increased, which improves the quality of organic fertilizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is the biochar (BC) and H in each treatment in the embodiment of the present invention. 2 O 2 SEM image of modified biochar (HPBC) at 20 μm;

[0042] Figure 2 The morphological changes and passivation effects of heavy metal copper (Cu) before and after composting in the embodiment of the present invention;

[0043] Figure 3 The morphological changes and passivation effects of heavy metal zinc (Zn) before and after composting in the embodiment of the present invention;

[0044] Figure 4 The morphological changes and passivation effects of heavy metal cadmium (Cd) before and after composting in the embodiment of the present invention;

[0045] Figure 5 The morphological changes and passivation effects of heavy metal lead (Pb) before and after composting in the embodiment of the present invention;

[0046] Figure 6The morphological changes and passivation effects of heavy metal chromium (Cr) before and after composting in the embodiment of the present invention;

[0047] Figure 7 The emission rate change and cumulative emission of nitrous oxide during aerobic composting in an embodiment of the present invention;

[0048] Figure 8 is the change of organic matter content during aerobic composting in an embodiment of the present invention;

[0049] Fig. 9 is the change of germination index during aerobic composting in an embodiment of the present invention;

[0050] Fig.10 This is the change in the total nutrient content of nitrogen, phosphorus and potassium after aerobic composting in the embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution of the present invention will be further described in detail below in conjunction with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0052] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0053] Example:

[0054] The embodiment of the present invention provides a modified biochar-based organic fertilizer and a preparation method thereof, which is a modified biochar-based organic fertilizer for reducing the heavy metal activity of livestock and poultry manure and reducing nitrous oxide emissions. The organic fertilizer is composed of the following components, measured in parts by weight:

[0055] 5-10 parts of livestock and poultry manure, 2-4 parts of composting materials and 2-4 parts of hydrogen peroxide modified biochar;

[0056] The hydrogen peroxide-modified biochar is prepared by uniformly mixing straw biochar and 5% hydrogen peroxide solution in a ratio of 1:10; the livestock and poultry manure is fresh chicken manure; and the composting auxiliary material is bagasse.

[0057] The following is a method for preparing the modified biochar-based organic fertilizer of this embodiment, comprising the following steps:

[0058] Step 1: Biochar preparation

[0059] Take wheat straw, crush it with a crusher (length 2-3 cm), spread the crushed wheat straw evenly in a quartz boat, put it into a tube furnace, and heat it at a flow rate of 20 mL / min of N 2 Under the atmosphere, the temperature was raised to the set temperature of 500°C at a rate of 10°C / min and pyrolyzed for 4 hours. After the pyrolysis was completed, it was cooled to room temperature and taken out to obtain straw biochar.

[0060] Step 2: H 2 O 2 Preparation of modified biochar

[0061] The straw biochar was sieved (2 mm) and mixed with 5% hydrogen peroxide solution at a ratio of 1:10, placed in a constant temperature shaker at 30°C and shaken at a speed of 180 r / min for 6 hours, taken out, separated from the solid and liquid, and repeatedly rinsed with deionized water until the filtrate was close to neutral, and the solid was placed in a 70°C oven to dry to constant weight. It was stored in a sealed bag for later use.

[0062] Step 3: Preparation of compost

[0063] 1. Material preparation

[0064] Livestock and poultry manure: Choose fresh chicken manure no more than 3 days old with a moisture content of 80%.

[0065] Bagasse: air-dried and crushed into small pieces of 2-3 cm in length, with a moisture content of 30%.

[0066] 2. Preparation of compost

[0067] Using livestock and poultry manure as raw material and bagasse as conditioning agent, the conditioning agent and livestock and poultry manure were mixed, the moisture content was adjusted to about 65%, and the C / N ratio was between 20:1 and 30:1. After adding modified biochar, the mixture was mixed evenly. The modified biochar addition ratio was 10% (dry basis). Unmodified biochar was used as a control. A 60L composting fermentation tank was loaded for aerobic composting experiments. A temperature probe was inserted in the upper part to monitor the temperature change of the pile (set to measure once every 10 minutes). Intermittent ventilation was used, and the ventilation rate was set to 0.4N·kg / h. Ventilation was performed for 30 minutes per hour and paused for 30 minutes. Each group of piles was manually turned on the 3rd, 7th, 14th, 21st, and 28th days, and the composting cycle was 35 days. A total of 3 treatment groups were set up:

[0068] CK treatment; chicken manure + bagasse;

[0069] BC treatment: chicken manure + bagasse + unmodified biochar;

[0070] HPBC treatment: chicken manure + bagasse + H 2 O 2 Modified biochar.

[0071] Step 4: Collection and determination of heavy metal samples

[0072] Compost samples were collected on the 0th day and the 35th day after the start of composting (at least 6 points), mixed evenly, air-dried, crushed and sieved for the determination of the total amount of heavy metals (copper, zinc, chromium, cadmium, lead) and various metal forms including oxidation state (OF), exchangeable state (EXCH), reduced state (RF) and residual state (RESI).

[0073] Step 5: N in the composting process 2 O gas collection and determination

[0074] Starting from the first day of composting, gas collection began at 9 am every day until the end of composting. 15 minutes before gas collection, the gas outlet of the fermenter was blocked with a wooden plug. When gas collection was performed, the wooden plug was pulled out, and the three-way valve in front of the 25ml needle was connected to the three-way valve at the gas outlet. Before extracting gas, the needle piston was pushed and pulled to evenly mix the gas in the fermenter before gas collection. The first tube of gas collected from each tank was discarded, and the gas collected in the needle was pumped into the gas collection tube. Three tubes of gas were extracted from each fermenter for processing. As a repeat, a gas chromatograph was used to analyze N 2 O content was measured.

[0075] In the above embodiments of the present invention, Figure 1 As shown, it is the biochar (BC) and H 2 O 2 SEM image of modified biochar (HPBC) at 20 μm. It can be seen that the surface of BC is relatively smooth, with less pore structure and larger pore size, while the surface of HPBC is relatively rough, with significantly smaller pore size, more microporous structure, and obvious tiny particles and fine powdery substances attached, indicating that the modification has a certain pore-forming effect on biochar.

[0076] like Figure 2 The figure shows the changes in the forms of heavy metal copper (Cu) and the passivation effect before and after composting. The distribution rate is an important indicator for evaluating the environmental risk of heavy metals. From the changes in the distribution rates of various forms of Cu, the heavy metal Cu in the composting process is mainly in the oxidized state (OF). After composting in each treatment, the exchangeable state (EXCH) Cu and the reduced state (RF) Cu decreased to varying degrees, while the oxidized state (OF) and residual state (RESI) Cu increased. The sum of the distribution rates of oxidized and residual states of Cu in the three treatments increased from 85.89%, 89.23%, and 82.90% before composting to 93.42%, 92.02%, and 92.99% after composting, respectively, indicating that composting can effectively reduce the activity and mobility of heavy metals in chicken manure compost, thereby inhibiting its bioavailability. From the perspective of the passivation effect of exchangeable Cu, the passivation effects of the three treatments on Cu are HPBC>BC>CK. The passivation effect of HPBC treatment is significantly higher than that of BC and CK (P<0.05).

[0077] like Figure 3 As shown in the figure, it shows the change of heavy metal zinc (Zn) form and passivation effect before and after composting. From the distribution rate of heavy metal Zn, the form of heavy metal Zn before composting is mainly reduced state (RF). During the composting process, the distribution ratio of exchangeable state (EXCH) and reducible state (RF) gradually decreases. After the end of composting, the exchangeable state Zn decreased by 1.21%, 4.61%, and 7.02%, respectively, and the reducible state Zn decreased by 4.59%, 3.10%, and 4.43%, respectively. The sum of the distribution rate of oxidized state and residual state Zn in the three treatments increased from 48.21%, 40.72%, and 31.30% before composting to 54.00%, 48.44%, and 42.75% after composting, respectively, indicating that composting can reduce the bioavailability of Zn. The decrease in the exchangeable state and the increase in the residual state of HPBC are greater than those of CK and BC, which can promote the conversion of exchangeable state Zn into residual state during composting and reduce the bioavailability of Zn. The Znization effects of the five treatments were 9.65%, 31.15%, and 40.89%, respectively. The passivation effects were HPBC>BC>CK. From the LSD significant variance analysis, it was found that both HPBC and BC were significantly different from CK (P<0.05), and HPBC had the best passivation effect.

[0078] like Figure 4 As shown, it shows the changes in the form of heavy metal cadmium (Cd) and the passivation effect before and after composting. From the distribution rate of heavy metal Cd, the form of heavy metal Cd before and after composting is mainly reduced (RF). After the composting is completed, the exchangeable (EXCH) Cd decreased from 11.52%, 14.69%, and 16.49% before composting to 8.08%, 10.00%, 5.95% after composting. The reducible (RF) Cd decreased from 45.55%, 50.23%, and 53.82% before composting to 43.50%, 49.34%, and 36.32% after composting. The sum of the distribution rates of oxidized and residual Cd in the three treatments increased from 42.92%, 35.08%, and 29.69% before composting to 48.42%, 40.65%, and 57.73% after composting, respectively, indicating that composting can also reduce the bioavailability of Cd. The decrease in the exchangeable state and the increase in the residual state of HPBC were greater than those of CK and BC, which can promote the conversion of exchangeable Cd into residual state during composting and reduce the bioavailability of Cd. The Cdification effects of the three treatments were 29.88%, 33.21%, and 63.86%, respectively, and the passivation effects were HPBC>BC>CK. The LSD significant variance analysis showed that HPBC was significantly different from BC and CK (P<0.05), indicating that modified biochar was helpful for the passivation of Cd.

[0079] like Figure 5As shown in the figure, it shows the change of heavy metal lead (Pb) form and passivation effect before and after composting. From the distribution rate of heavy metal Pb, the form of heavy metal Pb before and after composting is mainly oxidized (OF) and residual (RESI), which increases after composting. After composting, the sum of the distribution rate of oxidized and residual Pb in the three treatments increased from 76.20%, 65.40%, and 61.81% before composting to 79.67%, 74.65%, and 76.18% after composting, respectively. The smallest increase was in CK, and the largest increase was in HPBC. After the end of composting, the distribution ratio of exchangeable (EXCH) and reduced (RF) Pb decreased. The Pbization effects of the five treatments were 11.51%, 17.22%, and 40.54%, respectively. The passivation effects were HPBC>BC>CK, and HPBC had the best passivation effect.

[0080] like Figure 6 As shown in the figure, the morphological changes and passivation effects of heavy metal chromium (Cr) before and after composting. From the distribution rate of heavy metal Cr, the morphology of heavy metal Cr before and after composting is mainly residual state (RESI). The sum of the distribution rates of oxidized and residual Cr in the three treatments increased from 74.44%, 75.68%, and 78.84% before composting to 82.86%, 83.52%, and 86.16% after composting, respectively. After the end of composting, the exchangeable (EXCH) and reducible (RF) Cr both decreased, indicating that composting treatment can inhibit the bioavailability of Cr. The Crification effects of the five treatments were 17.90%, 28.13%, and 29.43%, respectively. The passivation effects were HPBC>BC>CK. From the LSD significant variance analysis, it can be seen that HPBC and BC are significantly different from CK.

[0081] like Figure 7 As shown in the figure, it shows the emission rate change and cumulative emission of nitrous oxide during aerobic composting. 2 O) emissions were mainly concentrated in the middle stage of composting, and BC and CK fluctuated greatly. This may be because the thermotolerant methane oxidizing bacteria were undergoing nitrification and ammonia oxidation, which resulted in more N in the high temperature period of composting. 2 The emission rate of HPBC treatment did not change much compared with BC and CK treatments. As the composting progressed, nitrogen decreased, the conversion efficiency slowed down, the activity of denitrifying bacteria decreased, the rate of nitrous oxide formation slowed down, and finally tended to be flat. The cumulative nitrous oxide emissions of each treatment were CK (84.59) > BC (64.93) > HPOBC (31.62). The cumulative nitrous oxide emissions of CK treatment were significantly higher than those of the other two groups, and the total nitrous oxide emissions of HPBC were significantly lower than those of the other two groups. It had the best effect on reducing nitrous oxide emissions, indicating that the addition of biochar had a significant effect on reducing nitrous oxide released in compost.

[0082] like Figure 8 As shown, it shows the change of organic matter content during aerobic composting. It can be seen that the rate of decrease is faster during the heating and high temperature period of composting, and the rate of decrease is slower during the cooling and maturity period. After the composting stopped, the organic matter content of each treatment was HPBC (64.37) > BC (62.17%) > CK (58.85%), which is in line with the agricultural industry standards of the People's Republic of China. During the heating and high temperature period of composting, microorganisms can quickly utilize more easily degradable small molecular organic matter in the pile, so the organic matter decomposes faster. In the later stage of composting, the temperature drops, the small molecular substances are fully decomposed, and there are relatively more difficult-to-decompose substances in the pile, which slows down the degradation rate of organic matter. According to the significant difference analysis, the HPBC treatment after composting was significantly higher than the CK treatment, indicating that the addition of modified biochar can increase the organic matter content of compost.

[0083] like Fig. 9 As shown, it is the change of germination index during aerobic composting. It can be seen that the germination index shows an overall upward trend as the composting progresses. Before composting, it was less than 50%. At this time, the pile contained more toxic substances, which was not conducive to application as fertilizer. After composting, the germination index of each treatment was HPBC (136.12%)>BC (116.86%)>CK (101.06%). It can be seen that HPBC has the largest increase and CK has the smallest increase. From the 0th day to the 14th day of composting, GI increased rapidly, indicating that in the early and middle stages of composting, organic matter in the pile was continuously decomposed, soluble salts were utilized, and toxic substances slowly disappeared. After the 14th day of composting, the GI growth rate slowed down, which may be due to the slow degradation of toxic substances in the pile or the basic decomposition of toxic substances. According to the germination index, it can also be shown that HPBC treatment is more conducive to crop growth and development than BC and CK, and the obtained organic fertilizer has the best quality.

[0084] like Fig.10 As shown, it shows the change of total nutrient content of nitrogen, phosphorus and potassium after aerobic composting. Total nutrient content of nitrogen, phosphorus and potassium is a very important nutrient indicator in the composting process. After the composting is completed, too low nitrogen, phosphorus and potassium content will affect the quality of the compost. After composting, the total nutrients of nitrogen, phosphorus and potassium in each treatment are HPBC (7.00%)>BC (6.63%)>CK (5.78%). The total nutrients in the HPBC treatment are the highest. According to the organic fertilizer standards of the Ministry of Agriculture and Rural Affairs of the People's Republic of China, the total nutrient content should be greater than 4%, and all treatments meet the standards. However, the nutrient content of the CK treatment is significantly lower than that of the BC and HPBC treatments, indicating that the treatment of adding biochar can effectively retain nutrients in the pile and reduce nutrient loss. Among them, HPBC has the best effect and can provide more nutrients for crops after application as a fertilizer.

[0085] The above specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make modifications to the embodiments without any creative contribution as needed. However, such modifications are protected by the patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A modified biochar-based organic fertilizer, characterized in that: The organic fertilizer is composed of the following components, in parts by weight: 5-10 parts of livestock and poultry manure, 2-4 parts of composting materials and 2-4 parts of hydrogen peroxide modified biochar; The hydrogen peroxide modified biochar is prepared by uniformly mixing straw biochar and 5% hydrogen peroxide solution at a ratio of 1:10; the livestock and poultry manure is fresh chicken manure; and the composting auxiliary material is bagasse.

2. A modified biochar-based organic fertilizer as claimed in claim 1, characterized in that: The organic fertilizer is composed of the following components, in parts by weight: 5 parts of livestock and poultry manure, 2 parts of composting auxiliary materials and 2 parts of hydrogen peroxide modified biochar.

3. A modified biochar-based organic fertilizer as claimed in claim 1, characterized in that: The organic fertilizer is composed of the following components, in parts by weight: 10 parts of livestock and poultry manure, 4 parts of composting auxiliary materials and 4 parts of hydrogen peroxide modified biochar.

4. A modified biochar-based organic fertilizer as claimed in claim 1, characterized in that: The organic fertilizer is composed of the following components, in parts by weight: 7 parts of livestock and poultry manure, 3 parts of composting auxiliary materials and 3 parts of hydrogen peroxide modified biochar.

5. A method for preparing a modified biochar-based organic fertilizer according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Biochar preparation Take wheat straw, crush it with a crusher, evenly spread the crushed wheat straw in a quartz boat, put it into a tube furnace, and heat it to a set temperature of 500°C at a rate of 10°C / min in a N2 atmosphere with a flow rate of 20mL / min. Pyrolyze for 4h. After the pyrolysis is completed, cool it to room temperature and take it out to obtain straw biochar; Preparation of S2 and H2O2 modified biochar The sieved straw biochar and 5% hydrogen peroxide solution were uniformly mixed at a ratio of 1:10, placed in a constant temperature shaker at 30°C and shaken at a speed of 180r / min for 6h, taken out, solid-liquid separation was performed, and the mixture was repeatedly rinsed with deionized water until the filtrate was close to neutral, and the solid was placed in an oven at 70°C and dried to constant weight; and stored in a sealed bag for later use; S3. Preparation of compost A. Material preparation Livestock and poultry manure: Use fresh chicken manure no older than 3 days with a moisture content of 80%; Bagasse: air-dried and crushed into small pieces of 2-3 cm in length, with a moisture content of 30%; B. Preparation of compost The livestock and poultry manure was used as the raw material, and bagasse was used as the conditioning agent. The conditioning agent and livestock and poultry manure were mixed, and the moisture content was adjusted to about 65%, and the C / N ratio was between 20:1 and 30:

1. After adding modified biochar, the mixture was evenly mixed. The modified biochar addition ratio was 10%. The unmodified biochar was used as the control treatment group, and the mixture was loaded into a 60L composting fermentation tank for aerobic composting experiment. A temperature probe was inserted into the upper part to monitor the temperature change of the pile. The temperature was set to be measured every 10 minutes. Intermittent ventilation was used, and the ventilation rate was set to 0.4N·kg / h. The temperature was ventilated for 30 minutes per hour and paused for 30 minutes. Each group of piles was manually turned on the 3rd, 7th, 14th, 21st, and 28th days, and the composting cycle was 35 days. S4. Collection and determination of heavy metal samples Compost samples were collected on the 0th and 35th days after the start of composting, mixed evenly, air-dried, crushed and sieved for the determination of the total amount of heavy metals and various metal forms including oxidized state, exchangeable state, reduced state and residual state; S5. Collection and determination of N2O gas during composting Starting from the first day of composting, gas collection began at 9 a.m. every day until the end of composting; 15 minutes before gas collection, the gas outlet of the fermenter was blocked with a wooden plug, and the wooden plug was pulled out during gas collection. The three-way valve in front of the 25 ml syringe was connected to the three-way valve at the gas outlet, and the syringe piston was pushed and pulled before gas was extracted to evenly mix the gas in the fermenter before gas collection. The first tube of gas collected from each tank was discarded, and the gas collected in the syringe was pumped into the gas collection pipe. Three tubes of gas were extracted from each fermenter for processing as a repeat, and the N2O content was determined using a gas chromatograph.

6. A method for preparing a modified biochar-based organic fertilizer as claimed in claim 5, characterized in that: The compost samples in step S4 are collected from at least 6 points.

7. A method for preparing a modified biochar-based organic fertilizer as claimed in claim 6, characterized in that: In step S3, B, the following three processing groups are set: CK treatment group; chicken manure + bagasse; BC treatment group: chicken manure + bagasse + unmodified biochar; OBC treatment group: chicken manure + bagasse + H2O2 modified biochar.

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