1. A method for reducing carbon emission by combining hydrothermal carbonization with organic solid waste high-temperature fermentation is characterized by comprising the following steps:

(1) carrying out hydrothermal reaction on the solid waste to obtain biochar;

(2) adding a high-temperature microbial inoculum, a leavening agent and the biochar prepared in the step (1) into solid waste to obtain a mixed fermentation material A, and performing high-temperature fermentation to obtain fermented rotten clinker;

(3) and (3) adding the fermented rotten clinker obtained in the step (2) and the biochar prepared in the step (1) into the solid waste to obtain a mixed fermented material B, and performing high-temperature fermentation to obtain a final fermented product.

2. The method according to claim 1, wherein in the step (1), the water content of the solid waste is 60-90 wt%; the temperature of the hydrothermal reaction is 100-200 ℃, the pressure is 1.5-2.0 MPa, and the time is 3-5 h.

3. The method as claimed in claim 1, wherein in the step (2), the solid waste, the biochar and the leavening agent are respectively 80-85%, 5-8% and 7-15% by volume, and the sum of the three is 100%.

4. The method according to claim 1, wherein in the step (2), the inoculation amount of the high-temperature microbial inoculum is 2-3 vol.% of the solid waste, the high-temperature microbial inoculum is a mixed bacterial liquid consisting of high-temperature bacteria and extreme thermophilic bacteria, the weight of the high-temperature bacteria is 0.2-0.8% of the weight of the biochar, and the concentration of the extreme thermophilic bacteria in the mixed bacterial liquid is more than or equal to 1.0 x 10⁷CFU/mL; the thermophilic bacteria are mixed strains belonging to Camiterricohi, and the extreme thermophilic bacteria are mixed strains belonging to Calditerricola and Thermus thermophilus.

5. The method according to claim 1, wherein in the step (2), the carbon-nitrogen ratio of the mixed fermentation material A is (25-35): 1, the pH is 7.0-7.8, the water content is less than 60 wt%, the fermentation time is 10-15 days, and the fermentation material is turned and thrown once every 3 days.

6. The method according to claim 1, wherein in the step (3), the volume ratio of the fermented rotten clinker to the solid waste to the biochar is (10-12) to (1-2).

7. The method according to claim 1, wherein in the step (3), the carbon-nitrogen ratio of the mixed fermentation material B is (25-35) to 1, the pH value is 7.0-7.8, the water content is less than 60 wt%, and the fermentation time is 10-15 days.

Background

The safe utilization of solid wastes is always the key point of research, and with the continuous improvement of sewage treatment equipment, the rapid development of animal husbandry, the classification and promotion of household wastes of residents and the like, a large amount of solid wastes such as sludge, excrement, kitchen wastes and the like are generated every year. The method for treating the organic solid waste mainly comprises an anaerobic digestion method, an incineration method, an aerobic composting method, biological carbonization, a hydrothermal carbonization technology and the like. Among them, composting is a biological and environment-friendly process, which is regarded as an effective and economical way of treating solid wastes, and aerobic composting is widely used because of its advantages of low treatment cost, simple operation, high resource utilization, etc. The traditional aerobic composting method has the advantages that the temperature is only 50-70 ℃ in a high-temperature stage, the fermentation temperature is low, the fermentation period is long, the treatment efficiency is low, and in order to accelerate the biodegradability, the humification degree and the maturation process can be improved through functional strain inoculation. In addition, the mature compost product is widely used as an expanding agent for improving air permeability and reducing bulk density due to economic advantages, the recovery of the mature compost obviously creates a suitable environment for microbial activities, reduces ammonia emission and shortens the sludge composting period. The sludge hydrothermal carbonization technology is one of the sludge hydrothermal technologies, has the advantages of short treatment period, high energy recovery rate and small occupied area, and the product can be used as auxiliary fuel, fertilizer and soil conditioner, and can stabilize carbon source, heavy metal, nitrogen element and phosphorus element, thereby realizing the recycling of sludge treatment. The biochar has developed pores, large specific surface area and strong adsorption capacity, and can provide a strong space for microbial activities in the composting process, so that the influence of biochar addition on sludge composting becomes a hot point of research.

Thermophilic bacteria or hyperthermophilic bacteria refer to a class of extreme microorganisms that can grow at temperatures above 65 ℃ and even above 100 ℃. By adopting high-temperature composting taking organic solid wastes as organic matters, the composting period can be shortened, and the maturity of the composting is improved, so that the loss of nitrogen is reduced, and the method has advantages in the aspects of composting quality and efficiency. The multifunctional thermophilic microorganism combination bred from the compost improves the biodegradation of organic matters and lignocellulose and obviously improves the stability and aromaticity of dissolved organic matters and humus. However, a method for synchronously inoculating thermophilic bacterial strains to perform high-temperature composting by replacing auxiliary materials with biochar and decomposed materials generated by a hydrothermal carbonization technology and backmixing the decomposed materials in a large proportion has not been researched by systematic application.

Disclosure of Invention

The invention aims to solve the problems of low fermentation temperature, long fermentation period, low treatment efficiency, high auxiliary material adding cost and the like of the traditional aerobic composting, and further provides a novel high-temperature composting method which is efficient, economical and low-carbon, namely a method for reducing carbon emission by hydrothermal carbonization in cooperation with high-temperature fermentation of organic solid wastes, provides a new thought and method for application and development of a novel solid waste biological treatment technology, and finally realizes reduction, harmless and recycling treatment of organic solid wastes such as sludge, livestock and poultry manure, kitchen garbage and the like.

In order to achieve the purpose, the invention provides the following technical scheme:

the invention provides a method for reducing carbon emission by hydrothermal carbonization in cooperation with high-temperature fermentation of organic solid waste, which comprises the following steps:

(1) carrying out hydrothermal reaction on the solid waste to obtain biochar;

(2) adding a high-temperature microbial inoculum, a leavening agent and the biochar prepared in the step (1) into solid waste to obtain a mixed fermentation material A, and performing high-temperature fermentation to obtain fermented rotten clinker;

(3) and (3) adding the fermented rotten clinker obtained in the step (2) into the solid waste to serve as a return material, and the biochar prepared in the step (1) to obtain a mixed fermented material B, and performing high-temperature fermentation to obtain a final fermented product.

In the step (2), as the high-temperature microbial inoculum is added for fermentation, and the fermented rotten clinker in the step (2) is continuously fermented in the step (3), the temperature of the mixed materials in the step (2) and the step (3) reaches 75-120 ℃ in a high-temperature fermentation period, and can be maintained for 3-5 days all the time, so that the real effect of high-temperature fermentation is achieved.

Further, in the step (1), the water content of the solid waste is 60-90 wt%; the temperature of the hydrothermal reaction is 100-200 ℃, the pressure is 1.5-2.0 MPa, and the time is 3-5 h.

The hydrothermal carbonization temperature of the hydrothermal carbonization system is controlled to be 100-200 ℃, the pressure is controlled to be 1.5-2.0 MPa, and the reaction time is controlled to be 3-5 h. Under the action of certain temperature and pressure, the microbial cells in the organic matter are crushed, the macromolecular organic matter is hydrolyzed, the water in the cells is released, and the hydrothermal carbon is directly generated through reactions of devolatilization, polycondensation, dehydrogenation, decarbonation and the like.

Further, in the step (2), the volume percentages of the solid waste, the biochar and the leavening agent are respectively 80-85%, 5-8% and 7-15%, and the sum of the volume percentages of the solid waste, the biochar and the leavening agent is 100%.

Further, in the step (2), the inoculation amount of the high-temperature microbial inoculum is 2-3 vol.% of the solid waste, the high-temperature microbial inoculum is a mixed bacterial liquid composed of high-temperature bacteria and extreme thermophilic bacteria, the weight of the high-temperature bacteria is 0.2-0.8% of the weight of the biochar, and the concentration of the extreme thermophilic bacteria in the mixed bacterial liquid is more than or equal to 1.0 × 10⁷CFU/mL; the thermophilic bacteria are various mixed strains in Camiterricohi, and the extreme thermophilic bacteria are mixed strains belonging to Calditerricola and Thermus thermophilus.

Further, in the step (2), the carbon-nitrogen ratio of the mixed fermentation material A is (25-35): 1, the pH is 7.0-7.8, the water content is less than 60 wt%, the fermentation time is 10-15 days, and the fermentation material is turned and thrown once every 3 days.

Further, in the step (2), the aeration amount is 0.3-0.5 Lmin^-1kg^-1。

Further, in the step (3), the volume ratio of the fermented rotten clinker to the solid waste to the biochar is (10-12) to (1-2).

Further, in the step (3), the carbon-nitrogen ratio of the mixed fermentation material B is (25-35) to 1, the pH value is 7.0-7.8, the water content is less than 60 wt%, and the high-temperature fermentation time is 10-15 days.

Compared with the prior art, the invention has the following beneficial effects:

the invention utilizes hydrothermal carbon in cooperation with a high-temperature fermentation technology, utilizes hydrothermal carbon waste heat to start preheating for high-temperature composting, provides favorable conditions for accelerating the initial temperature rise of sludge composting, has strong impact resistance, and meets the requirement of continuous high temperature of the high-temperature composting.

The invention improves the nitrogen conversion, compost maturity and humification level. By recycling mature compost, thermophilic bacterial strain is inoculated at early stage, the inoculation period is short, the temperature and NO are high₃ ^-both-N and GI show higher efficiency. Meanwhile, the total nitrogen content of the compost product containing the biochar is increased, and the compost quality is better.

The invention gives full play to the advantages of hydrothermal carbonization, is more favorable for improving the activity of extreme thermophilic bacteria, better retains the nutrient substances required by the growth of crops such as N, P in wastes and the like, and increases the carbon sink of the earth.

According to the invention, the decomposed materials are successfully mixed back in a large proportion by utilizing the strong metabolic capability of refractory organic matters of high-temperature bacteria, the inoculation of the high-temperature microbial inoculum is synchronously realized and the leavening agent is replaced, the using amount of the organic leavening agent is reduced, the synergistic effect of hydrothermal carbonization and high-temperature bacteria composting is exerted, the energy consumption is saved, the feasibility is high, the operation is simple and convenient, the production period is short, the product quality is stable, and the carbon emission is greatly reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a process flow diagram of example 1 of the present invention.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

The solid waste and the leavening agent treated by the invention are from Shenyang Su Jiatun farm; the adopted high-temperature bacteria are various mixed strains in Camierricohi; the extreme thermophilic bacteria are mixed strains belonging to Calditerricola, Thermus thermophilus, all purchased from Shenyang east environmental science and technology Limited.

Example 1

As shown in fig. 1, the apparatus for hydrothermal carbonization in cooperation with organic solid waste high temperature fermentation of the present invention includes a hydrothermal carbonization system 1, a high temperature fermentation system 2 and an intelligent control system 3. The hydrothermal carbonization system 1 comprises a hydrothermal carbonization reaction kettle 11, a heating system 12 and leachate treatment equipment 13; the high-temperature fermentation system 2 comprises a material mixing system 21, an auxiliary material adding device 22, a microbial inoculum adding device 23, a high-temperature fermentation bed 24, a fermentation product collecting device 25, a ventilation oxygen supply device 26 and an odor collecting device 27; the intelligent control system 3 is respectively connected with the hydrothermal carbonization system 1 and the high-temperature fermentation system 2. The intelligent control system 3 respectively feeds back and adjusts the heating system 12 according to the temperature parameters of the hydrothermal carbonization system 1, adjusts the ventilation oxygen supply device 26 according to the dissolved oxygen of the high-temperature fermentation system 2, controls the start and stop of the percolate treatment device 13 according to the percolate liquid level, and controls the start and stop of the odor collection device 27 and gives an alarm according to the deodorization air volume; the odor collecting device 27 and the leachate treatment device 13 adopt a matched high-temperature sludge compost leachate and odor synergistic treatment method to complete treatment. And the normal and efficient operation of the system is further ensured, secondary pollution is avoided, land utilization is finally carried out, and the sludge is really subjected to stabilization, harmless and recycling treatment by the method.

The method for reducing carbon emission by adopting the device to carry out hydrothermal carbonization in cooperation with organic solid waste high-temperature fermentation comprises the following specific steps:

(1) firstly, conveying solid waste with the water content of 75 wt% to a hydrothermal carbonization reaction kettle 11 through a high-pressure sludge pump, then starting a heating system 12 through an intelligent control system 3, regulating and controlling the operation parameters of the hydrothermal carbonization system 1 to 200 ℃, controlling the pressure to be 2.0MPa, and controlling the reaction time to be 3 h; the water content of the biochar obtained through the hydrothermal carbonization reaction is 35 wt%, the volume reduction of the sludge is 70%, and according to the requirement, the leachate treatment equipment 13 is started through the intelligent control system 3, and the waste liquid is collected to the leachate treatment equipment 13 for treatment; the hydrothermal carbonization reaction kettle 11 is heated by oil bath, and the heat source adopts electric heating and subsequent high-temperature composting for heat recovery;

(2) the biochar obtained in the step (1) directly enters a mixing system 21 of the high-temperature fermentation system 2, and is mixed with compost raw materials in the mixing system 21 for cooling, so that the preheating starting purpose of high-temperature compost is synchronously realized: adding a leavening agent into a mixing system according to the volume percentage of 85% of solid waste, 5% of the biochar obtained in the step (1) and 10% of the leavening agent, wherein the leavening agent is added through an auxiliary material adding device 22, meanwhile, a high-temperature microbial inoculum is added into the mixing system 21 through a microbial inoculum adding device 23, the high-temperature microbial inoculum is a mixed bacterial liquid consisting of high-temperature bacteria and extreme thermophilic bacteria, the adding amount is 2 vol% of the solid waste, the adding amount of the high-temperature bacteria is 0.5% of the weight of the biochar, and the concentration of the extreme thermophilic bacteria in the mixed bacterial liquid is more than or equal to 1.0 x 10⁷CFU/mL; then the mixed materials in the mixing system are conveyed to a high-temperature fermentation bed 24; the C/N ratio of the mixed material is controlled to be 30:1, the pH value is controlled to be 7.5, the water content of the mixed material is 55 wt%, the DO concentration is 4mg/L, and the aeration quantity is 0.4Lmin^-1kg^-1Fermenting for 15 days, turning and throwing once every 3 days, and feeding and turning and throwing are carried out by adopting a pointer dynamic distribution mode. Measuring, wherein the material temperature is up to 120 ℃ in 5 days before fermentation, the material temperature is maintained at over 75 ℃ in a high-temperature period, and a first batch of high-temperature fermented rotten clinker is obtained through high-temperature fermentation composting;

(3) obtaining high-temperature compost rotten clinker through the step (2), adding the biochar obtained in the step (1), the rotten clinker obtained in the step (2) and solid waste into a mixing system 21 according to the volume ratio of 5: 50: 45 to obtain a mixed material, controlling the C/N ratio of the mixed material to be 30:1, the pH value to be 7.5, controlling the water content of the mixed material to be 55 wt%, controlling the DO concentration to be 3mg/L and controlling the aeration quantity to be 0.3Lmin^-1kg^-1Fermenting for 15 days, and turning and throwing once every 3 days. Through measurement, 5 days before fermentation, the material temperature reaches 120 ℃ at most, the high-temperature material temperature is maintained above 75 ℃, and a final sludge fermentation product, namely the biochar organic fertilizer, is obtained through fermentation.

The process flow diagram of this example is shown in FIG. 1.

Example 2

The device is the same as the embodiment 1, and the method for reducing carbon emission by adopting the device to carry out hydrothermal carbonization in cooperation with organic solid waste high-temperature fermentation comprises the following specific steps:

(1) firstly, conveying solid waste with the water content of 60 wt% to a hydrothermal carbonization reaction kettle 11 through a high-pressure sludge pump, then starting a heating system 12 through an intelligent control system 3, regulating and controlling the operation parameters of the hydrothermal carbonization system 1 to be 100 ℃, controlling the pressure to be 1.5MPa, and controlling the reaction time to be 5 h; the water content of the biochar obtained through the hydrothermal carbonization reaction is 30 wt%, the volume reduction of the sludge is 75%, the leachate treatment equipment 13 is started through the intelligent control system 3 according to the requirement, and the waste liquid is collected to the leachate treatment equipment 13 for treatment; the hydrothermal carbonization reaction kettle 11 is heated by oil bath, and the heat source adopts electric heating and subsequent high-temperature composting for heat recovery;

(2) the biochar obtained in the step (1) directly enters a mixing system 21 of the high-temperature fermentation system 2, and is mixed with compost raw materials in the mixing system 21 for cooling, so that the preheating starting purpose of high-temperature compost is synchronously realized: adding a leavening agent into a mixing system according to the volume percentage of 80% of solid waste, 8% of the biochar obtained in the step (1) and 12% of the leavening agent, wherein the leavening agent is added through an auxiliary material adding device 22, meanwhile, a high-temperature microbial inoculum is added into the mixing system 21 through a microbial inoculum adding device 23, the high-temperature microbial inoculum is a mixed bacterial liquid consisting of high-temperature bacteria and extreme thermophilic bacteria, the adding amount is 3 vol% of the solid waste, the adding amount of the high-temperature bacteria is 0.2% of the weight of the biochar, and the concentration of the extreme thermophilic bacteria in the mixed bacterial liquid is more than or equal to 1.0 x 10⁷CFU/mL; then the mixed materials in the mixing system are conveyed to a high-temperature fermentation bed 24; the C/N ratio of the mixed material is controlled to be 25:1, the pH value is controlled to be 7.0, the water content of the mixed material is 55 wt%, the DO concentration is 3mg/L, and the aeration quantity is 0.3Lmin^-1kg^-1Fermenting for 10 days, turning and throwing once every 3 days, and feeding and turning and throwing are carried out by adopting a pointer dynamic distribution mode. Measuring, wherein the material temperature is up to 120 ℃ in 5 days before fermentation, the material temperature is maintained at more than 75 ℃ in a high-temperature period, and a first batch of high-temperature fermented rotten clinker is obtained through high-temperature fermentation composting;

(3) the high-temperature compost rotten clinker is obtained through the step (2), and is put into a material mixing system 21 according to the volume ratio of 8: 40: 52Adding the biochar obtained in the step (1), the decomposed material obtained in the step (2) and solid waste to obtain a mixed material, wherein the leavening agent is added through auxiliary material adding equipment 22, the C/N ratio of the mixed material is controlled to be 25:1, the pH value is controlled to be 7.0, the water content of the mixed material is 55 wt%, the DO concentration is 3mg/L, and the aeration amount is 0.3Lmin^-1kg^-1Fermenting for 10 days, and turning and throwing once every 3 days. Through measurement, 5 days before fermentation, the material temperature reaches 120 ℃ at most, the material temperature is maintained at more than 75 ℃ in a high-temperature period, and a final sludge fermentation product, namely the biochar organic fertilizer, is obtained through fermentation.

Example 3

The device is the same as the embodiment 1, and the method for reducing carbon emission by adopting the device to carry out hydrothermal carbonization in cooperation with organic solid waste high-temperature fermentation comprises the following specific steps:

(1) firstly, conveying solid waste with the water content of 90 wt% to a hydrothermal carbonization reaction kettle 11 through a high-pressure sludge pump, then starting a heating system 12 through an intelligent control system 3, regulating and controlling the operation parameters of a hydrothermal carbonization system 1 to be 150 ℃, controlling the pressure to be 2.0MPa, and controlling the reaction time to be 4 h; the water content of the biochar obtained through the hydrothermal carbonization reaction is 40 wt%, the volume reduction of the sludge is 83%, the leachate treatment equipment 13 is started through the intelligent control system 3 according to the requirement, and the waste liquid is collected to the leachate treatment equipment 13 for treatment; the hydrothermal carbonization reaction kettle 11 is heated by oil bath, and the heat source adopts electric heating and subsequent high-temperature composting for heat recovery;

(2) the biochar obtained in the step (1) directly enters a mixing system 21 of the high-temperature fermentation system 2, and is mixed with compost raw materials in the mixing system 21 for cooling, so that the preheating starting purpose of high-temperature compost is synchronously realized: adding a leavening agent into a mixing system according to the volume percentage of 85% of solid waste, 8% of the biochar obtained in the step (1) and 7% of the leavening agent, wherein the leavening agent is added through an auxiliary material adding device 22, meanwhile, a high-temperature microbial inoculum is added into the mixing system 21 through a microbial inoculum adding device 23, the high-temperature microbial inoculum is a mixed bacterial liquid consisting of high-temperature bacteria and extreme thermophilic bacteria, the adding amount is 2.5 vol.% of the solid waste, the adding amount of the high-temperature bacteria is 0.8% of the weight of the biochar, and the concentration of the extreme thermophilic bacteria in the mixed bacterial liquid is≥1.0×10⁷CFU/mL; then the mixed materials in the mixing system are conveyed to a high-temperature fermentation bed 24; the C/N ratio of the mixed material is controlled to be 35:1, the pH value is controlled to be 7.8, the water content of the mixed material is 50 wt%, the DO concentration is 5mg/L, and the aeration quantity is 0.5Lmin^-1kg^-1Fermenting for 12 days, turning and throwing once every 3 days, and feeding and turning and throwing are carried out by adopting a pointer dynamic distribution mode. Measuring, wherein the material temperature reaches 120 ℃ at most 5 days before fermentation, the temperature in a high-temperature period can be maintained above 75 ℃, and a first batch of high-temperature fermented rotten clinker is obtained through high-temperature fermentation composting;

(3) obtaining high-temperature compost rotten clinker through the step (2), adding the biochar obtained in the step (1), the rotten clinker obtained in the step (2) and solid waste into a mixing system 21 according to the volume ratio of 10: 60: 30 to obtain a mixed material, controlling the C/N ratio of the mixed material to be 35:1, the pH value to be 7.8, controlling the water content of the mixed material to be 50 wt%, controlling the DO concentration to be 3mg/L and controlling the aeration quantity to be 0.3Lmin^-1kg^-1Fermenting for 12 days, and turning and throwing once every 3 days. Through measurement, 5 days before fermentation, the material temperature reaches 120 ℃ at most, the temperature in the high-temperature period can be maintained above 75 ℃, and a final sludge fermentation product, namely the biochar organic fertilizer, is obtained through fermentation.

Comparative example 1

The difference from example 1 is that step (1) is not included, and biochar is not added in step (2) and step (3).

Comparative example 2

The difference from example 1 is that the high temperature microbial inoculum in step (2) is replaced by the same volume of culture solution without high temperature bacteria, and other parameters are the same as those in example 1, namely, the large-proportion back mixing fermentation is carried out under the condition of not inoculating the high temperature bacteria.

Comparative example 3

The difference from example 1 is that only step (1) and step (2) are carried out, and the fermentation days in step (2) are prolonged to 30 days, i.e. only the traditional high temperature bacteria inoculation composting is carried out without using the rotten clinker as the back mixing material.

The C, N, P content in the organic fertilizer prepared in examples 1 to 3 and comparative examples 1 to 3 was measured, and the results are shown in table 1.

TABLE 1

Item

Example 1

Example 2

Example 3

Comparative example 1

Comparative example 2

Comparative example 3

Content of C

26.11％

27.83％

25.96％

12.15％

17.12％

19.92％

Content of N

1.43％

1.65％

1.42％

0.81％

0.96％

1.07％

P content

0.52％

0.68％

0.53％

0.38％

0.39％

0.32％

As can be seen from table 1, the biochar organic fertilizer obtained by the invention has a high C, P, N content, and the biochar organic fertilizer obtained by the invention is relatively low in C, N, P content without adding biochar, or performing large-proportion back-mixing fermentation without inoculating high-temperature bacteria, or performing traditional high-temperature bacteria inoculation composting without adopting decomposed materials as back-mixing materials. The carbon source is directly increased by adding the biochar, meanwhile, the leaching loss of N, P leachate is reduced by the biochar adsorption effect, and the biochar is beneficial to strengthening the solid N metabolism microorganisms, so that the nitrogen preservation effect is realized. When large-proportion back-mixing fermentation is carried out under the condition of not inoculating high-temperature bacteria, because the microbial community in the traditional compost is difficult to use a large amount of organic matters which are difficult to degrade in the back-mixing material as a carbon source, when the decomposed material obtained by primary fermentation is used for secondary fermentation in a large-proportion back-mixing mode, the inoculation of the strains can not be realized, the secondary fermentation process can not be well started, and therefore, a good fermentation effect can not be achieved. The method does not adopt the rotten clinker as a back-mixed material, and only needs to additionally add a large amount of leavening agents and inoculate again when the traditional high-temperature bacteria inoculation composting is carried out, so that the resource waste is caused, and the starting period is prolonged.

According to the invention, the high-temperature microbial inoculum is adopted for primary fermentation, and when the obtained decomposed material is back-mixed in a large proportion and is continuously subjected to secondary fermentation, the inoculation of the high-temperature microbial inoculum in the secondary fermentation material can be successfully realized, the activity is continuously exerted, and the metabolism of refractory organic matters in solid waste is realized, so that the secondary inoculation is omitted, and a good fermentation effect can be still obtained on the basis of omitting other large quantities of auxiliary materials in the secondary fermentation process.

The concentration, the hygiene indexes and the physicochemical indexes of pollutants in the organic fertilizer prepared in the embodiments 1 to 3 and the comparative examples 1 to 2 are detected, and the organic fertilizer meets the requirements of sludge treatment classification of urban sewage treatment plants (GB/T23484-2009), technical Specification for domestic garbage compost treatment (CJJ52-2014) and technical Specification for livestock and poultry manure compost (NY/T3442-2019), and the specifically met standards are shown in tables 2 to 4.

TABLE 2 concentration of contaminants in organic fertilizers

Serial number	Item	Unit of	Concentration of contaminants
				1	Total cadmium (on a dry basis)	mg/kg	＜3
2	Total mercury (on a dry basis)	mg/kg	＜3
				3	Total lead (on a dry basis)	mg/kg	≤300
4	Total chromium (on a dry basis)	mg/kg	＜500
				5	Total arsenic (on a dry basis)	mg/kg	＜30
6	Total nickel (on a dry basis)	mg/kg	＜100
				7	Total zinc (on a dry basis)	mg/kg	＜1200
8	Total copper (on a dry basis)	mg/kg	＜500
				9	Mineral oil (on a dry basis)	mg/kg	＜500
10	Benzo (a) pyrene (on a dry basis)	mg/kg	＜2
				11	Polycyclic Aromatic Hydrocarbons (PAHs) (on a dry basis)	mg/kg	＜5

TABLE 3 hygiene index of organic fertilizer

Serial number	Item	Unit of	Parameter value
				1	Death rate of ascarid eggs	％	≥95
2	Faecal coliform population value	mg/L	≥0.01

TABLE 4 physicochemical indices of organic fertilizer

Serial number	Item	Unit of	Parameter value
				1	Water content ratio	wt％	≤40
2	pH		5.5～8.5
				3	Particle size	mm	≤10
4	Organic matter (on a dry basis)	wt％	≥20

The leachate discharged in the embodiments 1-3 and the comparative examples 1-2 is detected to meet the water quality standard for sewage discharge into town sewers (GB T31962-2015) and meet the primary standard required by the comprehensive sewage discharge standard (GB-8978-.

TABLE 5 maximum allowable discharge concentration of contaminants in leachate

Serial number	Item	Unit of	Parameter value
				1	Chemical oxygen demand CODcr	mg/L	≤100
2	Biological oxygen demand BOD5	mg/L	≤30
				3	Suspended matter SS	mg/L	≤70
4	Ammonia nitrogen NH3		≤15
				5	pH		6～9

In examples 1 to 3 and comparative examples 1 to 2, the odor was treated and then discharged to meet the secondary standard specified in the emission Standard of malodorous pollutants (GB 14554-93): see table 6 for details; the malodorous pollutants emission standards were performed in organized emission compliance, see table 7.

TABLE 6

TABLE 7

From the above, the final fermentation product and the subsidiary products of the invention meet the requirements of the corresponding national standards.

The above description is only for the preferred embodiment of the present invention, and the protection scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical scope of the present invention, the technical solution and the inventive concept of the present invention equivalent or change within the technical scope of the present invention.