Application of vegetable tannin extract in promoting carbon and nitrogen emission reduction in secondary composting process of hermetia illucens sand

Abstract

The invention discloses an application of a vegetable tannin extract in promoting carbon and nitrogen emission reduction in a secondary composting process of hermetia illucens sand. The hermetia illucens sand composting method for promoting carbon and nitrogen emission reduction comprises the following steps: mixing a vegetable tannin extract, hermetia illucens sand and a carbon-containing material into an initial material, and carrying out aerobic composting fermentation to obtain compost. The vegetable tannin extract is one or two of chestnut tree tannin extract and quebracho tannin extract. According to the invention, the loss of greenhouse gas and nitrogen can be reduced, the requirement of insect sand decomposition can be improved, the emission of NH3, N2O, CH4, CO2 and other carbon and nitrogen gases in the secondary treatment process can be obviously controlled and reduced, the secondary pollution and potential environmental risk caused by the carbon and nitrogen gas emission and nitrogen loss in the aerobic composting process can be effectively reduced, the quality of the compost product can be improved, and the cost can be reduced. The requirement of returning the manure to the field for utilization is better met, and good social, economic and ecological benefits are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of resource utilization of livestock and poultry manure and secondary composting of black soldier fly sand, and in particular to application of plant tannin extract in promoting carbon and nitrogen emission reduction in the secondary composting process of black soldier fly sand. Background Art

[0002] With the continuous exploration of green and environmentally friendly livestock and poultry manure composting methods, it is found that the use of insects to treat livestock and poultry manure has achieved good results. Some insects can efficiently transform organic waste, such as necrophagous insects such as burying beetles and skin beetles, and saprophagous insects such as dung beetles, black soldier flies and maggots. These insects like to eat animal carcasses, livestock and poultry manure and decayed plant tissues in nature. Compared with other biological species, insects grow and reproduce quickly and have a high conversion rate for waste, so they are suitable for treating livestock and poultry manure.

[0003] In particular, the use of black soldier flies to biotransform livestock and poultry manure has many advantages. First, it has a short life cycle, strong resistance to stress, a wide diet, a large appetite, and high conversion efficiency for livestock and poultry manure; second, it can effectively reduce volatile organic compounds in the process of transforming livestock and poultry manure, and can also produce high-value value-added products; third, its insect body can be made into protein powder to replace animal feed, and the insect sand has been detected to contain a variety of beneficial substances, which can not only regulate the metabolism of microorganisms in the soil, but also promote the growth of crops. This shows that black soldier fly sand has the potential to be used as an organic fertilizer. However, through the analysis of existing studies, it can be found that the sand produced by the rapid biotransformation of livestock and poultry manure by black soldier flies has problems such as phytotoxicity and low maturity. It is an unstable product. If it is used as an organic fertilizer, it is necessary to carry out a secondary treatment for stabilization. In previous studies, scholars have explored the physical and chemical properties and applications of black soldier fly larvae biotransformed livestock and poultry manure and sand. However, the optimal treatment method for improving the quality of sand and coordinating environmental emission reduction needs further study.

[0004] Tannins are natural phenolic compounds widely found in nature. Plant tannins are widely distributed in nature and can be extracted from fruits, barks, leaves, flowers and other parts of most plants. In recent years, plant tannins have been used more and more frequently as feed additives to improve animal production, but there are few studies on the effects of adding plant tannins on composting.

[0005] Therefore, there is an urgent need to develop the application of plant tannin extracts in promoting carbon and nitrogen emission reduction in the secondary composting process of black soldier fly insect sand, thereby reducing the carbon and nitrogen emissions of insect sand during the secondary treatment process, thereby achieving the effect of improving the quality of insect sand organic fertilizer. This will help to provide some theoretical basis for further analysis of the impact of secondary treatment on insect sand and the resource utilization of insect sand. Summary of the invention

[0006] To solve the above problems, the present invention provides an application of plant tannin extract in promoting carbon and nitrogen emission reduction during the secondary composting process of black soldier fly frass. By adding plant tannin extract, the emissions of greenhouse gases such as NH3, N2O, CH4, and CO2 during the composting process are effectively controlled, thereby achieving the purpose of coordinating green environmental protection and quality improvement, and realizing the reduction of greenhouse gas emissions during the secondary composting process of black soldier fly frass.

[0007] The purpose of the present invention is to provide a method for composting black soldier fly frass to promote carbon and nitrogen emission reduction, which includes the following steps: Mix plant tannin extract, black soldier fly frass, and carbon-containing materials into initial materials for aerobic composting fermentation to obtain compost.

[0008] In the above method for composting black soldier fly frass to promote carbon and nitrogen emission reduction, the plant tannin extract is quebracho tannin extract ( Chestnut extracts ), quebracho blanco tannin extract ( Quebracho extracts ) or one or both of them. Experiments have found that quebracho tannin has a better effect on carbon and nitrogen emission reduction.

[0009] In the above method for composting black soldier fly frass to promote carbon and nitrogen emission reduction, calculated by dry matter, the mass of the plant tannin extract is 0.5-1% of the total mass of the black soldier fly frass and the carbon-containing materials, such as 1%; and / or, The mass percentage content of tannin in the plant tannin extract is 70%-75%, such as 70% or 75%; and / or, The plant tannin extract is an aqueous extract (an extract obtained by the aqueous extraction method), which uses water as a solvent. Through soaking and heating, the tannins in plant wood are dissolved in water, and the extract is obtained through concentration and drying. As an example, the chestnut tannin extract and the white oak tannin extract are provided by SAVA - Guangzhou SAVA Technology Co., Ltd. in Italy, and their preparation methods are as follows: (1) First, search for relevant wood in the forest (e.g., 80% of the wood comes from the Piedmont and Liguria regions); (2) Transport it to the SAVA factory and cut the wood according to local forestry regulations; (3) Break the tree trunk into small pieces to increase the surface area for tannin extraction by water; (4) Immerse the wood chips in hot water. This process is usually carried out in a closed reactor to ensure precise control of temperature and pressure: Add the broken wood chips to the reactor containing high - temperature hot water (e.g., 80°C to 100°C) at a certain ratio (e.g., the liquid - solid ratio is usually between 5:1 and 10:1); Maintain this temperature for several hours to more than ten hours to promote the effective dissolution of tannins; During this period, regular stirring is required to ensure uniform wetting of the wood chips, and at the same time, monitor the color change of the impregnation liquid. A dark brown color is preferred, indicating that the tannin component is being effectively released; Finally, a dark brown liquid: tannin is released; (5) Transfer the impregnation liquid to an evaporator and remove the excess water by heating evaporation; The evaporation process needs to strictly control the temperature (e.g., not exceeding 60°C to 80°C) to avoid damage to the tannin structure by high temperature; At the same time, determine the required tannin concentration by monitoring physical properties such as the density or refractive index of the liquid; Once the predetermined concentration is reached, immediately stop heating and prepare for the next step; (6) Atomize the concentrated liquid into tiny droplets through a high - pressure nozzle and then spray it into a high - temperature (e.g., 150°C to 200°C) air stream; The high - temperature air stream quickly removes the water in the droplets and dries them into powder; During the spray - drying process, the air - stream temperature and the outlet temperature need to be precisely controlled (e.g., generally between 70°C and 90°C) to ensure complete drying of the powder and avoid overheating; The dried powder is collected through an efficient collection system such as a cyclone separator or a bag filter to ensure the purity and yield of the product; (7) Finally, a tannin extract with a wide range of applications in different fields is formed, and the corresponding tannin is extracted according to different raw materials.

[0010] In the above - mentioned black soldier fly larva manure composting method for promoting carbon and nitrogen emission reduction, as an example, the black soldier fly larva manure is obtained through the following steps: Incubate the black soldier fly eggs for 2 to 3 days at a constant temperature of 30°C and a constant humidity of 30% until they show significant fluidity characteristics; Transfer the hatched larvae to coarse wheat bran with a water content of 70% for further feeding, and maintain the feeding environment at a constant temperature of 20°C; Select 6 - day - old black soldier fly larvae and put them into fresh chicken manure for biotransformation. After 16 days, when the black soldier fly larvae become pupae, separate the larva manure.

[0011] In the above black soldier fly larva manure composting method for promoting carbon and nitrogen reduction, the carbon-containing material is crop straw or wood material; optionally, the crop straw is rice straw, wheat straw or corn straw; optionally, the wood material is wood chips or sawdust; preferably, the wood chips are poplar wood chips. Compared with the larva manure, the wood chips have a high carbon-nitrogen ratio and a low moisture content, which can well adjust the carbon-nitrogen ratio and moisture content of the initial mixed material to meet the growth requirements of microorganisms, and at the same time is conducive to maintaining the fluffy and porous structure of the compost pile.

[0012] In the above black soldier fly larva manure composting method for promoting carbon and nitrogen reduction, the carbon-nitrogen ratio of the initial material is (20-30):1, such as 25:1.

[0013] In the above black soldier fly larva manure composting method for promoting carbon and nitrogen reduction, the moisture content of the initial material is 55%-65%, such as 60%.

[0014] In the above black soldier fly larva manure composting method for promoting carbon and nitrogen reduction, the aeration conditions for aerobic composting fermentation are as follows: continuous aeration for 7.5-8.5 h during the heating period, continuous aeration for 3.5-4.5 h during the high-temperature period, continuous aeration for 1.5-2.5 h during the cooling period, and continuous aeration for 0.5-1.5 h during the stable period, and the ventilation rate is uniformly set to 360 L / h. As an example, the aeration conditions are as follows: continuous aeration for 8 h during the heating period, continuous aeration for 4 h during the high-temperature period, continuous aeration for 2 h during the cooling period, and continuous aeration for 1 h during the stable period, and the ventilation rate is uniformly set to 360 L / h. Preferably, the aerobic composting can be subjected to turning treatment, such as turning the material once every 2 days, and the turning frequency can be appropriately increased as needed during the high-temperature period (the compost pile temperature ≥ 50°C). When the compost pile temperature tends to the ambient temperature, after turning treatment, if the compost pile temperature still does not rise significantly, ventilation can be stopped, and the main fermentation period of the compost ends. After fermentation, compost is obtained.

[0015] In the above black soldier fly larva manure composting method for promoting carbon and nitrogen reduction, the promotion of carbon and nitrogen reduction is reflected in reducing the emission of one or more of ammonia, nitrous oxide, methane, and carbon dioxide.

[0016] The present invention further protects the application of plant tannin extract in at least one of the following (A1)-(A3): (A1)Promote carbon and nitrogen reduction during the secondary composting of black soldier fly larva manure; (A2)Reduce the electrical conductivity of the compost; (A3)Increase the total potassium content of the compost.

[0017] In the above application, the plant tannin extract is one or two of chestnut wood tannin extract and quebracho tannin extract; experiments have found that chestnut wood tannin has a better effect on carbon and nitrogen reduction; quebracho tannin has a better effect on reducing electrical conductivity and increasing the total potassium content of the compost; The promotion of carbon and nitrogen reduction is reflected in the reduction of the emissions of one or more of ammonia, nitrous oxide, methane, and carbon dioxide.

[0018] The present invention has the following beneficial effects: The method for aerobic composting of black soldier fly larvae frass provided by the present invention can reduce greenhouse gas and nitrogen losses, improve the requirements for frass composting, significantly control and reduce the emissions of greenhouse gases such as NH3, N2O, CH4, and CO2 during the secondary treatment process, effectively reduce the secondary pollution and potential environmental risks caused by greenhouse gas emissions and nitrogen losses during the aerobic composting process, improve the quality of the compost product, better meet the requirements for manure returning to the field, and has good social, economic, and ecological benefits. Description of the Drawings

[0019] Figure 1 It is a photo of the self-made gas collection system in the embodiment of the present invention.

[0020] Figure 2 It is the dynamic change of the temperature of each composting treatment in the embodiment of the present invention.

[0021] Figure 3 It is the change of pH and EC of each composting treatment in the embodiment of the present invention.

[0022] Figure 4 It is the influence of adding plant tannin extract on the NH3 emission rate and cumulative emission amount of compost in the embodiment of the present invention.

[0023] Figure 5 It is the influence of adding plant tannin extract on the N2O emission rate and cumulative emission amount of compost in the embodiment of the present invention.

[0024] Figure 6 It is the influence of adding plant tannin extract on the CH4 emission rate and cumulative emission amount of compost in the embodiment of the present invention.

[0025] Figure 7 It is the influence of adding plant tannin extract on the CO2 emission rate and cumulative emission amount of compost in the embodiment of the present invention. Detailed Embodiments

[0026] The present invention will be further described in detail below in conjunction with the specific embodiments. The provided embodiments are only for clarifying the present invention and not for limiting the scope of the present invention. The following provided embodiments can be used as a guide for those of ordinary skill in the art to make further improvements and do not constitute any limitation to the present invention in any way.

[0027] The methods used in the following examples are conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

[0028] The tannin contents in chestnut extract and quebracho extract in the following examples are 75 wt% and 70 wt% respectively.

[0029] The aerobic composting test in the following examples uses sun-dried chicken manure purchased from a local chicken manure drying factory in Quzhou County and black soldier fly frass obtained by self-culturing black soldier flies for biotransformation in Youyuan Bio-organic Fertilizer Company in Handan City as the main raw materials. Among them, the preparation of black soldier fly frass is carried out under the conditions of a constant temperature of 30°C and a constant humidity of 30% for incubating black soldier fly eggs for 2 to 3 days until they show significant fluidity characteristics. The hatched larvae are transferred to coarse wheat bran with a water content of 70% for further feeding, and the feeding environment is maintained at a constant temperature of 20°C. Six-day-old black soldier fly larvae are selected and put into fresh chicken manure for biotransformation. After 16 days, when the black soldier fly larvae turn into pupae, frass separation is carried out, and the frass is used for the composting test. Wood chips purchased from a wood factory in Baizhai Town, Quzhou County are used as the compost filling material.

[0030] The basic physical and chemical properties of the compost raw materials are listed in Table 1.

[0031]

[0032] Example 1 In this example, an aerobic composting experiment is carried out by adding plant tannin extract to chicken manure, black soldier fly frass and wood chips to observe the effect of tannin on greenhouse gas emissions during the secondary composting process of black soldier fly frass.

[0033] Four sets of laboratory aerobic composting reactors with the same performance are used to carry out the combined aerobic composting test of sun-dried chicken manure, black soldier fly frass and wood chips.

[0034] Four different treatment groups are set up, including a control group (CK, sun-dried chicken manure + wood chips), a T1 group (black soldier fly frass + wood chips), a T2 group (black soldier fly frass + wood chips + 1% chestnut tannin extract), and a T3 group (black soldier fly frass + wood chips + 1% quebracho tannin extract).

[0035] The mixing steps of the initial materials in different treatment groups are as follows: Control group (CK, sun-dried chicken manure + wood chips): The addition amount of sun-dried chicken manure is 12 kg. The sun-dried chicken manure and wood chips are mixed at a carbon-nitrogen ratio of 25:1, and then the moisture is adjusted to 60% to obtain the initial composting material.

[0036] Group T1 (Hermetia illucens frass + wood chips): The addition amount of Hermetia illucens frass is 12 kg. The Hermetia illucens frass and wood chips are mixed at a carbon-nitrogen ratio of 25:1, and then the moisture is adjusted to 60% to obtain the initial composting material.

[0037] Group T2 (Hermetia illucens frass + wood chips + 1% quebracho tannin): The addition amount of Hermetia illucens frass is 12 kg. The Hermetia illucens frass and wood chips are mixed at a carbon-nitrogen ratio of 25:1, and then the moisture is adjusted to 60% to obtain the initial composting material. Among them, the tannin is completely dissolved with distilled water and then completely mixed evenly with the substrate. 1% quebracho tannin extract means that, based on dry matter, the mass of quebracho tannin extract is 1% of the total mass of Hermetia illucens frass and wood chips.

[0038] Group T3 (Hermetia illucens frass + wood chips + 1% quebracho schinopsis tannin): The addition amount of Hermetia illucens frass is 12 kg. The Hermetia illucens frass and wood chips are mixed at a carbon-nitrogen ratio of 25:1, and then the moisture is adjusted to 60% to obtain the initial composting material. Among them, the tannin is completely dissolved with distilled water and then completely mixed evenly with the substrate. 1% quebracho schinopsis tannin means that, based on dry matter, the mass of quebracho schinopsis tannin extract is 1% of the total mass of Hermetia illucens frass and wood chips.

[0039] After mixing, a 70 L cylindrical compost fermentation barrel is used for aerobic composting fermentation. During the fermentation process, a ventilation method combining aeration and turning is adopted. The aeration conditions are as follows according to different fermentation stages: continuous aeration for 8 h during the heating-up period, continuous aeration for 4 h during the high-temperature period, continuous aeration for 2 h during the cooling-down period, and continuous aeration for 1 h during the stable period. The ventilation rate is uniformly set to 360 L / h. During composting, the materials are turned over every 2 days to ensure air circulation. When turning over, a shovel is used to turn the materials in the fermentation barrel up and down to make them fully turned and mixed evenly.

[0040] Greenhouse gas collection and ammonia determination are carried out on the 0th, 3rd, 6th, 9th, 12th, 15th, 18th, 21st, 24th, 27th, 30th, 33rd, 36th, 39th, 42nd, and 45th days.

[0041] Greenhouse gas collection device: There is a gas sampling hole at the top of the compost reactor, and a self-made gas collection system is adopted ( Figure 1 )

[0042] Collection time: It is carried out between 3:00 pm and 4:00 pm every day, once every 3 days. One hour after sealing, a 60 mL gas syringe made of polypropylene is used to extract the gas in the box and transfer it to a 100 mL airtight bottle, repeating three times. The collected gas samples are stored in the airtight bottle, and a gas chromatograph is used to measure the concentration of greenhouse gases.

[0043] Ammonia determination: NH3 was determined by the dynamic chamber absorption method. After collecting the absorption solution, bromocresol green-methyl red indicator was added dropwise, and then titrated with 0.01 mol·L -1 sulfuric acid to calculate the emission rate and cumulative emissions of NH3.

[0044] Determination of nutrient indicators: On the 45th day, the compost materials were sampled for the determination of total nitrogen, total phosphorus, and total potassium. First, the samples were digested using the H2SO4-H2O2 digestion method, and the contents of nitrogen, phosphorus, and potassium could be determined separately in the same digestion solution. Among them, semi-micro distillation method was used for total nitrogen, vanadium molybdenum yellow spectrophotometry was used for total phosphorus, and flame photometry was used for total potassium.

[0045] The results of each test index are as follows: 1. Temperature The internal temperature of the compost pile is the main index to characterize the microbial activity and the decomposition process of organic materials during aerobic composting, and it is also one of the key factors in the entire composting process. During the experiment, at 9 am every day, a thermometer was used to measure the temperatures at the upper, middle, and lower positions of the compost pile respectively. After the values were stable, readings were taken, and the ambient temperature was measured at the same time. The materials in the 4 groups of aerobic composting reactors all experienced the three classic stages of heating period, high-temperature period, and cooling period. Each treatment rapidly heated up, and the temperature increased significantly on the second day, and remained at a relatively high temperature for the first 6 days, meeting the requirements for harmless composting. The measurement results are shown in Figure 2 , Figure 2 which is the dynamic change diagram of the aerobic composting temperature in the embodiment of the present invention.

[0046] As Figure 2 shown, in the initial stage, each treatment rapidly heated up, and the compost reached above 45°C on the second day. This may be because the optimized initial ratio of raw materials and the ventilation rate are relatively appropriate, which can ensure the rapid start of composting. Due to factors such as heat generation from compost degradation and the heat preservation effect of the reactor, there is no obvious difference in the temperature of each treatment in the middle and late stages of composting, and the overall compost quality and decomposition effect are good.

[0047] 2. pH and EC During the experiment, the changes in pH and EC of the compost are shown in Figure 3 As shown, the pH of each treatment group showed a trend of first rising and then decreasing, and reached the maximum value on the 18th day. There was no significant difference among the treatments at the end of composting. At the same time, the EC of each treatment group showed an upward trend. At the end of the experiment, the T2 and T3 treatments had lower EC values.

[0048] 3. Main emission gases (1) Ammonia The release of ammonia during composting is the main factor causing nitrogen loss. From Figure 4It can be seen that the ammonia emission rates of all treatments first increased and then decreased. The NH3 emission rate of sun-dried chicken manure was higher than that of other treatments, and the emission rate reached the highest value on the 6th day, while the NH3 emission rate of vermicompost reached the highest value on the 3rd day; after the 15th day, the difference in NH3 emission rates among the vermicompost treatments was not obvious; at the end of composting, compared with the CK treatment, the cumulative ammonia emissions of the T1 treatment decreased by 83.1% ( p <0.05), the T2 treatment decreased by 90.3% ( p <0.05), and the T3 treatment decreased by 89.7% ( p <0.05); compared with the T1 treatment, the cumulative ammonia emissions of the T2 treatment decreased by 42.9% ( p >0.05), and the T3 treatment decreased by 39.3% ( p >0.05).

[0049] (2) Nitrous oxide During composting, the emission rate and cumulative emissions of nitrous oxide are as Figure 5 shown. The N2O emission rate gradually increased with time. The N2O emission rate was relatively low in the early stage, probably because high temperature, NH4 + -N concentration and pH value would inhibit the activity of nitrifying bacteria. From 15 to 39 days, the emission rate of CK was higher than that of other treatments. From 9 to 36 days, the emission rate of the T1 treatment was higher than that of the T3 treatment. At the end of composting, compared with CK, the cumulative nitrous oxide emissions of T1 decreased by 14.49% ( p >0.05), the T2 decreased significantly by 26.34% ( p <0.05), and the T3 decreased significantly by 20.97% ( p <0.05). Compared with T1, the cumulative nitrous oxide emissions of T2 decreased significantly by 13.89% ( p <0.05), and the T3 decreased by 7.78% ( p >0.05). From the perspective of cumulative emissions, the addition of two tannin extracts had an inhibitory effect on N2O emissions.

[0050] (3) Methane The emission rate and cumulative emissions of methane are as Figure 6 shown. From the overall trend, the CH4 emission trends of all treatments were roughly the same, showing a trend of increasing - decreasing - rising - decreasing. From 0 to 6 days, the emission rate of CK was lower than that of other treatments. From 9 to 30 days, the emission rate of CK was higher than that of other treatments. At the end of composting, compared with CK, the cumulative methane emissions of T1 decreased significantly by 36.1% ( p <0.05), and the T2 decreased significantly by 56.8% ( p<0.05), T3 decreased significantly by 38.6% ( p <0.05). Compared with T1, the cumulative methane emissions of T2 decreased significantly by 32.49% ( p <0.05), and T3 decreased by 3.96% ( p >0.05). This also indicates that chestnut tannin extract has a good effect on reducing methane emissions.

[0051] (4) Carbon dioxide The emission rate and cumulative emissions of carbon dioxide are as Figure 7 shown. From 0 to 6 days, the emission rates of each treatment showed an increasing trend, decreased on the 9th day, then continued to increase until the 15th day, and then showed a decreasing trend from 15 to 45 days. At the initial stage of composting, due to the decomposition of microorganisms, macromolecular organic matter was degraded into small-molecular organic matter, resulting in an increase in CO2 emissions. At the end of composting, compared with CK, the cumulative carbon dioxide emissions of T1 decreased significantly by 18.0% ( p <0.05), T2 decreased significantly by 20.5% ( p <0.05), and T3 decreased significantly by 14.31% ( p <0.05). There was no significant difference among the wormcast treatment groups at the end of composting. Compared with T1, the cumulative carbon dioxide emissions of T2 decreased by 3.1%.

[0052] 4. Nutrient indicators The nutrient contents of each treatment at the end of composting are shown in Table 2. Among them, the total nitrogen content of the sun-dried chicken manure treatment (CK) was the highest, reaching 1.49% at the end, while the total nitrogen contents of the wormcast treatments (T1, T2, T3) were 1.43%, 1.45%, and 1.40% respectively, and there was no significant difference among the treatments. However, the total phosphorus and total potassium contents of the wormcast treatments (T1, T2, T3) were significantly higher than those of the sun-dried chicken manure treatment (CK).

[0053]

[0054] In summary, from the above results, it can be seen that during the secondary composting process of black soldier fly wormcast, adding two kinds of tannin extracts has a good effect on carbon and nitrogen emission reduction. Especially when adding chestnut tannin, compared with the wormcast treatment group without adding tannin, the cumulative emissions of ammonia, nitrous oxide, methane, and nitrogen dioxide decreased by 42.9%, 13.89%, 32.49%, and 3.1% respectively.

[0055] The present invention has been described in detail above. For those skilled in the art, the present invention can be implemented within a relatively wide range under equivalent parameters, concentrations, and conditions without departing from the gist and scope of the present invention. Although specific embodiments of the present invention are given, it should be understood that the present invention can be further improved. In short, according to the principle of the present invention, this application intends to cover any modifications, uses, or improvements to the present invention, including those that depart from the scope disclosed in this application and are made by using conventional techniques known in the art.

Claims

1. A black soldier fly sand composting method for promoting carbon and nitrogen emission reduction, characterized in that: The steps include: The plant tannin extract, black soldier fly sand and carbon-containing materials are mixed into initial materials for aerobic composting and fermentation to obtain compost.

2. The black soldier fly sand composting method for promoting carbon and nitrogen emission reduction according to claim 1, characterized in that: The plant tannin extract is one or both of chestnut tannin extract and white quebracho tannin extract.

3. The method for composting black soldier fly sand to promote carbon and nitrogen emission reduction according to any one of claims 1-2, characterized in that: The mass of the plant tannin extract is 0.5-1% of the total mass of the black soldier fly sand and the carbonaceous material, calculated on a dry matter basis; and / or, The mass percentage of tannin in the plant tannin extract is 70% to 75%; and / or, The plant tannin extract is a water extract.

4. The method for composting black soldier fly sand for promoting carbon and nitrogen emission reduction according to any one of claims 1 to 3, characterized in that: The carbon-containing material is crop straw or wood material.

5. The black soldier fly sand composting method for promoting carbon and nitrogen emission reduction according to any one of claims 1 to 4, characterized in that: The carbon-nitrogen ratio of the initial material is (20-30):

1.

6. The method for composting black soldier fly sand for promoting carbon and nitrogen emission reduction according to any one of claims 1 to 5, characterized in that: The water content of the initial material is 55% to 65%.

7. The black soldier fly sand composting method for promoting carbon and nitrogen emission reduction according to any one of claims 1 to 6, characterized in that: The aeration conditions of the aerobic composting fermentation are as follows: continuous aeration for 7.5 to 8.5 h during the temperature rise period, continuous aeration for 3.5 to 4.5 h during the high temperature period, continuous aeration for 1.5 to 2.5 h during the temperature drop period, continuous aeration for 0.5 to 1.5 h during the stable period, and the ventilation rate is uniformly set to 360 L / h.

8. The black soldier fly sand composting method for promoting carbon and nitrogen emission reduction according to any one of claims 1 to 7, characterized in that: The promotion of carbon and nitrogen emission reduction is embodied in reducing the emission of one or more gases among ammonia, nitrous oxide, methane and carbon dioxide.

9. Use of plant tannin extract in at least one of the following (A1)-(A3): (A1) Promote carbon and nitrogen emission reduction during the secondary composting of black soldier fly sand; (A2) Reduce the electrical conductivity of compost; (A3)Increase the total potassium content of compost.

10. The use according to claim 9, characterized in that: The plant tannin extract is one or both of chestnut tannin extract and white quebracho tannin extract; The promotion of carbon and nitrogen emission reduction is embodied in reducing the emission of one or more gases among ammonia, nitrous oxide, methane and carbon dioxide.

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