Application of plant tannin extract in promoting carbon and nitrogen utilization and emission reduction of black soldier fly breeding substrate

Abstract

The application discloses application of a plant tannin extract in promoting efficient utilization and emission reduction of carbon and nitrogen nutrients in black soldier fly breeding substrates. The application comprises the following steps: inoculating black soldier fly larvae into a substrate formed by mixing a plant tannin extract, livestock manure and carbon-containing materials, and breeding the black soldier fly under constant temperature, constant humidity, light shielding and open conditions; and collecting the insect bodies and sand after the breeding is completed. The plant tannin extract is one or both of chestnut tannin extract and white oak tannin extract. By adding the plant tannin into the substrate, optimizing the black soldier fly growth conditions and the manure treatment process, the growth of the black soldier fly can be promoted, the carbon and nitrogen gas emission can be reduced, the resource utilization efficiency can be improved, and the sustainable development can be promoted.

Description

Technical Field

[0001] This invention relates to the fields of organic waste resource utilization and black soldier fly larvae farming technology, specifically to the application of plant tannin extracts in promoting the efficient utilization and emission reduction of carbon and nitrogen nutrients in black soldier fly larvae farming substrates. Background Technology

[0002] With the booming development of livestock and poultry farming, the output of livestock and poultry manure has increased dramatically, becoming a pressing agricultural waste problem. This untreated manure not only occupies a large amount of land resources but can also pollute water bodies and soil through runoff and infiltration, releasing harmful gases and posing a serious threat to the environment and human health. Currently, although there are various methods for the resource utilization of livestock and poultry manure, such as composting, anaerobic digestion, and aerobic fermentation, problems such as severe nitrogen loss, high operating costs, and malodorous gas emissions still exist, failing to fundamentally solve the problems of environmental pollution and low resource utilization efficiency. Therefore, developing a new, efficient, environmentally friendly, and economical method for the resource utilization of livestock and poultry manure is particularly important.

[0003] Against this backdrop, black soldier fly larvae have emerged as an ideal choice for treating livestock and poultry manure due to their powerful biotransformation capabilities. They can feed on livestock and poultry manure, converting it into high-quality insect protein and organic fertilizer rich in nutrients such as nitrogen, phosphorus, and potassium through digestion and metabolism. This method not only effectively reduces pollution from livestock farming but also realizes the resource utilization of agricultural waste, offering advantages such as low investment, low operating costs, and good environmental effects, thus having a positive significance for the sustainable development of the livestock and poultry farming industry. However, although significant progress has been made in recent years in the research on the biotransformation of agricultural waste such as chicken manure by black soldier fly larvae, many shortcomings and controversies remain regarding carbon and nitrogen conversion, loss, and bioavailability. How to further improve the utilization efficiency of nitrogen in manure by black soldier fly larvae, reduce nitrogen loss, and optimize their growth conditions to improve biotransformation efficiency have become urgent research problems to be solved.

[0004] Tannins are naturally occurring phenolic compounds widely found in plants such as gallnut, chestnut, tea, grape, caragana, hardwood, birdsfoot, sorghum, and coffee. They can be extracted from the fruits, bark, leaves, and flowers of most plants. Tannins exhibit various potential roles in biology and environmental science. However, the potential role of tannins in influencing biotransformation processes and the research gaps remain to be explored in depth. In particular, it is important to investigate whether tannins can affect the biotransformation of livestock and poultry manure by influencing the digestive enzyme activity and gut microbiota structure of black soldier fly larvae, and whether tannins interact with organic and inorganic matter in manure to affect its physicochemical properties and bioavailability.

[0005] Therefore, there is an urgent need for a plant tannin extract to promote the efficient utilization and emission reduction of carbon and nitrogen nutrients in black soldier fly larvae substrates, thereby improving the biotransformation performance of black soldier flies, reducing ammonia and greenhouse gas emissions, increasing the resource utilization rate of livestock and poultry manure, and providing strong support for the sustainable development of the livestock and poultry farming industry. Summary of the Invention

[0006] The purpose of this invention is to provide an application of plant tannin extracts in promoting the efficient utilization and emission reduction of carbon and nitrogen nutrients in black soldier fly larvae substrates. By efficiently utilizing plant tannins, the growth conditions of black soldier flies and the manure treatment process are optimized to promote black soldier fly growth, reduce carbon and nitrogen emissions from livestock and poultry manure, solve the problems of manure pollution and low resource utilization efficiency, promote the sustainable development of livestock and poultry farming, and develop an efficient, environmentally friendly, and economical method for the resource utilization of livestock and poultry manure.

[0007] In a first aspect, the present invention provides a method for promoting the growth of black soldier fly larvae and / or improving the quality of insect-sand mixtures, comprising the following steps: Black soldier fly larvae are inoculated into a substrate composed of plant tannin extracts, poultry and livestock manure, and carbon-containing materials for black soldier fly breeding. After breeding is completed, the larvae and sand are collected.

[0008] In the above-mentioned methods for promoting the growth of black soldier flies and / or improving the quality of insect sand, the black soldier fly larvae are black soldier fly larvae of several days old, specifically 6 days old. The plant tannin extract is chestnut tannin extract ( Chestnut extracts ), white solid wood ( Quebracho extracts One or two of the plant tannin extracts, wherein the preferred plant tannin extracts are white tannin extract and chestnut tannin extract in a mass ratio of 1:(0.5-1), specifically 1:1, 2:1 or 1:2; On a dry matter basis, the mass of the plant tannin extract is 0.15% to 10% of the total mass of the livestock and poultry manure and the carbon-containing materials, such as 0.15% to 0.5%, 0.5%, 1.5%, 4%, or 10%. The tannin extract contains 70% to 75% tannin by mass, such as 70% or 75%. The plant tannin extract is an aqueous extract; The livestock and poultry manure is chicken manure, cow manure, pig manure or duck manure; The carbon-containing material is crop straw or wood material; optionally, the crop straw is rice straw, wheat straw or corn stalk; optionally, the wood material is wood chips, wood flakes or sawdust. The carbon-to-nitrogen ratio of the substrate is (15-25):1, such as 15:1; The moisture content of the substrate is 60%–75%, such as 70%; The pH of the substrate is 5–10, such as 8.03; The breeding is carried out at an ambient temperature of 25–30°C, such as 30°C.

[0009] In the above-mentioned methods for promoting the growth of black soldier flies and / or improving the quality of insect sand, the promotion of black soldier fly growth is manifested in at least one aspect of the following (A1) to (A4): (A1) Increases the body length of black soldier fly larvae; (A2) Increases the weight of black soldier fly larvae; (A3) Increase the total yield of black soldier fly larvae; (A4) Increases the crude fat content of black soldier fly larvae; The improvement in the quality of insect-infested sand is reflected in at least one of increasing the pH value of the insect-infested sand, reducing the electrical conductivity of the insect-infested sand, and reducing the nitrate nitrogen content of the insect-infested sand.

[0010] Secondly, the present invention provides a method for raising black soldier fly larvae to enhance their biotransformation capacity, comprising the following steps: inoculating black soldier fly larvae into a substrate composed of plant tannin extracts, poultry and livestock manure and carbon-containing materials, raising black soldier fly larvae under constant temperature, constant humidity, light-proof and open conditions, and collecting the larvae and larval sand after the raising is completed.

[0011] In the above-mentioned method for promoting the growth of black soldier flies, the black soldier fly larvae are black soldier fly larvae of several days old, specifically 6 days old. The plant tannin extract is one or two of chestnut wood tannin extract and white tannin wood extract. The preferred plant tannin extract is white tannin wood extract and chestnut wood tannin extract in a mass ratio of 1:(0.5-1), specifically 1:1, 2:1 or 1:2. On a dry matter basis, the mass of the plant tannin extract is 0.15% to 10% of the total mass of the livestock and poultry manure and the carbon-containing materials, such as 0.15% to 0.5%, 0.5%, 1.5%, 4%, or 10%. The tannin extract contains 70% to 75% tannin by mass, such as 70% or 75%. The plant tannin extract is an aqueous extract; The livestock and poultry manure is chicken manure, cow manure, pig manure or duck manure; The carbon-containing material is crop straw or wood material; optionally, the crop straw is rice straw, wheat straw or corn stalk; optionally, the wood material is wood chips, wood flakes or sawdust. The carbon-to-nitrogen ratio of the substrate is (15-25):1, such as 15:1; The relative humidity of the substrate is 60%–75%, such as 70%; The pH of the substrate is 5–10, such as 8.03; The breeding is carried out at an ambient temperature of 25–30°C, such as 30°C.

[0012] In the aforementioned method for enhancing the bioconversion capacity of black soldier flies, the enhancement of the bioconversion capacity is manifested in at least one aspect of the following (B1) to (B2): (B1) Improve the bioconversion rate and / or waste reduction rate of black soldier flies; (B2) Improve the conversion ratio of substrate to black soldier fly prepupae biomass; The improvement of the utilization rate of carbon and nitrogen nutrients in livestock and poultry manure is specifically manifested in reducing the content of organic carbon and / or total nitrogen in the manure after conversion by black soldier flies.

[0013] Thirdly, the present invention provides a method for raising black soldier fly larvae to reduce carbon and nitrogen gas emissions or improve the utilization rate of carbon and nitrogen nutrients in livestock and poultry manure, comprising the following steps: inoculating black soldier fly larvae into a substrate composed of plant tannin extracts, livestock and poultry manure and carbon-containing materials, raising black soldier fly larvae under constant temperature, constant humidity, light-proof and open conditions, and collecting the larvae and larval sand after the raising is completed.

[0014] In the above-mentioned method for promoting the growth of black soldier flies, the black soldier fly larvae are black soldier fly larvae of several days old, specifically 6 days old. The plant tannin extract is one or two of chestnut wood tannin extract and white tannin wood extract. The preferred plant tannin extract is white tannin wood extract and chestnut wood tannin extract in a mass ratio of 1:(0.5-1), specifically 1:1, 2:1 or 1:2. On a dry matter basis, the mass of the plant tannin extract is 0.15% to 10% of the total mass of the livestock and poultry manure and the carbon-containing materials, such as 0.15% to 0.5%, 0.5%, 1.5%, 4%, or 10%. The tannin extract contains 70% to 75% tannin by mass, such as 70% or 75%. The plant tannin extract is an aqueous extract; The livestock and poultry manure is chicken manure, cow manure, pig manure or duck manure; The carbon-containing material is crop straw or wood material; optionally, the crop straw is rice straw, wheat straw or corn stalk; optionally, the wood material is wood chips, wood flakes or sawdust. The carbon-to-nitrogen ratio of the substrate is (15-25):1, such as 15:1; The relative humidity of the substrate is 60%–75%, such as 70%; The pH of the substrate is 5–10, such as 8.03; The breeding is carried out at an ambient temperature of 25–30°C, such as 30°C.

[0015] In the aforementioned black soldier fly farming method for reducing carbon and nitrogen emissions or improving the utilization rate of carbon and nitrogen nutrients in livestock and poultry manure, the reduction of carbon and nitrogen emissions is manifested in at least one aspect of the following (C1) to (C5): (C1) Reduce cumulative NH3 emissions; (C2) Reduce cumulative CO2 emissions; (C3) Reduce cumulative CH4 emissions (C4) Reduce cumulative N2O emissions (C5) Reduce global warming potential.

[0016] In any of the methods described above, the black soldier fly larvae are specifically obtained by rearing black soldier fly eggs in a constant temperature and humidity environment using wheat bran. Further, the rearing temperature is 20°C–32°C, and the humidity is 25%–50%, such as a constant temperature of 30°C and a constant humidity of 30%. The moisture content of the wheat bran can specifically be 70%.

[0017] This invention also protects the use of plant tannin extracts in at least one of the following: 1) Improve the growth performance of black soldier flies; 2) Improve the utilization rate of carbon and nitrogen nutrients in livestock and poultry manure in black soldier fly larvae culture substrate; 3) Reduce carbon and nitrogen emissions from livestock and poultry manure during black soldier fly farming; 4) Improve the biotransformation performance of black soldier flies; 5) Improve the quality of insect-infested sand; The plant tannin extract is one or both of chestnut wood tannin extract and white tannin wood extract, and the preferred plant tannin extract is white tannin wood extract and chestnut wood tannin extract in a mass ratio of 1:(0.5-1).

[0018] In the above applications, the growth performance is reflected in one or more of body length, weight, and yield; The carbon and nitrogen gases are one or more of NH3, CO2, N2O, and CH4; The bioconversion performance is reflected in the bioconversion rate and / or waste reduction rate; The improvement in the quality of insect-infested sand is reflected in increasing the pH value and reducing the electrical conductivity of the sand.

[0019] In this invention, the plant tannin water extract refers to an extract obtained by water extraction, which uses water as a solvent and involves soaking and heating to dissolve the tannins in the plant wood in the water, followed by concentration and drying. As an example, the chestnut wood tannin extract and the white succulent wood tannin extract were provided by Italian company Swarovski-Guangzhou Swarovski Technology Co., Ltd., and their preparation method is as follows: (1) First, find relevant wood from the forest (80% of the wood comes from the Piedmont and Liguria regions); (2) Transport the wood to Swarovski's factory and cut it according to local forestry regulations; (3) Crush the trunk into small pieces to increase the surface area for water extraction of tannin; (4) Impregnate the wood chips with hot water. This process is usually carried out in a closed reactor to ensure precise control of temperature and pressure: add the crushed wood chips to a reactor containing hot water (e.g., 80°C to 100°C) in a certain proportion (e.g., the liquid-to-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 tannin; during this period, it is necessary to stir regularly to ensure that the wood chips are evenly impregnated, and monitor the color change of the impregnation liquid. Dark brown is preferred, indicating that the tannin components are being effectively released; finally, a dark brown liquid is released from it. Tannin; (5) Transfer the impregnation liquid to the evaporator and remove excess water by heating and evaporation; the evaporation process requires strict temperature control (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 the physical properties of the liquid such as density or refractive index; once the predetermined concentration is reached, stop heating immediately and prepare to proceed to 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) airflow; the high-temperature airflow quickly removes the water in the droplets, drying them into powder; during the spray drying process, the airflow temperature and outlet temperature (e.g., generally between 70°C and 90°C) must be precisely controlled to ensure the complete drying of the powder and avoid overheating; the dried powder is collected by a high-efficiency 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 the different raw materials.

[0020] The present invention has the following beneficial effects: (1) Promote the growth of black soldier fly: By optimizing the growth conditions, the growth rate and bioconversion rate of black soldier fly were improved.

[0021] (2) Reduce carbon and nitrogen emissions: Use plant tannins to regulate the microbial community structure in feces to reduce the emission of carbon and nitrogen gases (such as ammonia, carbon dioxide, etc.).

[0022] (3) Improve resource utilization efficiency: Convert livestock and poultry manure into high-quality organic fertilizer and feed additives to improve resource utilization efficiency.

[0023] (4) Promote sustainable development: Provide a resource utilization method that is efficient, environmentally friendly and economical for livestock and poultry farming, and promote the sustainable development of the farming industry. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the black soldier fly cultivation and gas storage device of the present invention.

[0025] Figure 2 These are the average body length and average weight of each black soldier fly larva during the experiment in this embodiment of the invention.

[0026] Figure 3 This invention relates to the effect of adding plant tannins on the physicochemical properties of black soldier fly sand.

[0027] Figure 4 This embodiment of the invention describes the effect of plant tannins on the substrate NH3 emission rate and cumulative emission during the BSF conversion of chicken manure.

[0028] Figure 5 This embodiment of the invention describes the effect of plant tannins on the substrate CO2 emission rate and cumulative emission during the BSF conversion of chicken manure.

[0029] Figure 6 This is a comparison of the effects of plant tannins on the global warming potential of the substrate during the black soldier fly treatment of chicken manure conversion in embodiments of the present invention. Note: * indicates Duncan post-hoc test. P <0.05 indicates a significant difference; ** indicates a statistically significant difference. P <0.01 indicates extremely significant difference; *** indicates significant difference. P <0.001 indicates a highly significant difference. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0031] Unless otherwise specified, the methods used in the following embodiments are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0032] The sources of the raw materials in the following examples are as follows: The livestock and poultry manure used was collected from the experimental site of Chenguang Group Company in Quzhou County, Hebei Province, with fresh chicken manure selected as the main raw material.

[0033] The sawdust was purchased from the timber market in Baizhai Town, Quzhou County, Hebei Province, and used to adjust the carbon-nitrogen ratio of each group to 15:1.

[0034] Black soldier fly eggs: purchased from Zhengzhou Kuocheng Ecological Agriculture Technology Co., Ltd.

[0035] In the examples below, the tannin content in chestnut wood extract and white oak extract is 75wt% and 70wt%, respectively.

[0036] Example 1 This embodiment involves culturing black soldier flies with the addition of plant tannins to the substrate, and observing the effects of plant tannins on black soldier fly growth, carbon and nitrogen emissions, fecal pollution, and resource utilization efficiency.

[0037] 0.5% *Albizia julibrissin* extract (CT) and 0.5% *Caragana korshinskii* extract (HT), as well as a mixed solution (MIX) of 0.25% *Albizia julibrissin* extract and 0.25% *Caragana korshinskii* extract (using distilled water as the solvent), were prepared. During the experiment, each treatment group thoroughly mixed the above solutions with the matrix. All additives were formulated based on dry matter weight ratios. Here, 0.25% and 0.5% represent the percentage of dry weight of the matrix (substrate). During the experiment, the dry matter weight of the matrix for all treatment groups was 0.812 kg. The amount of *Albizia julibrissin* tannin added to the CT group was 4.06 g, the amount of *Caragana korshinskii* tannin added to the HT group was 4.06 g, and the amount of *Caragana korshinskii* tannin added to the MIX group was 2.03 g and 2.03 g of *Caragana korshinskii* tannin added respectively.

[0038] The specific steps are as follows: (1) First, hatch and raise black soldier flies. Black soldier fly eggs were incubated for 2 to 3 days under constant temperature and humidity conditions of 30°C until they exhibited significant mobility. The hatched larvae were then transferred to coarse wheat bran with a moisture content of 70% for further rearing, while the rearing environment was maintained at a constant temperature of 30°C. Six-day-old black soldier fly larvae were selected as the experimental subjects.

[0039] (2) The experiment was conducted in the laboratory, and four different treatment groups were designed: control group (CK, fresh chicken manure), CT group (chicken manure + 0.5% white pine tannin), HT group (chicken manure + 0.5% chestnut tannin), and MIX group (chicken manure + 0.25% white pine tannin + 0.25% chestnut tannin).

[0040] Substrate preparation: Each group of substrates (a mixture of 1.6 kg of fresh chicken manure and 0.4 kg of sawdust) was prepared by adjusting the carbon-to-nitrogen ratio of the substrate to 15:1 and the dry weight to 0.812 kg. The substrate was then evenly spread at the bottom of a self-made culture device (34 cm × 25 cm × 15.5 cm) and the moisture content was adjusted to 70%. The pH value of the substrate was 8.03.

[0041] (3) Inoculation and culture: 1,000 6-day-old black soldier fly larvae were inoculated into each group, and three replicates were set up for each group. After inoculation, the device was placed in an artificial climate chamber and cultured in the dark under constant temperature of 30°C and constant humidity of 70%. Observations were made every 8 hours.

[0042] (4) Gas collection and analysis Greenhouse gas collection device: The top of the cultivation device is equipped with a gas collection port, and a self-made gas collection system is used. Figure 1 ).

[0043] Collection time: Daily from 3:00 PM to 4:00 PM, once daily. At 10, 30, and 50 minutes after sealing, gas was drawn from the chamber using a 60 mL polypropylene gas syringe and transferred to a 100 mL airtight bottle, repeated three times. The collected gas samples were stored in airtight bottles, and the concentration of greenhouse gases was determined using gas chromatography.

[0044] Ammonia determination: NH3 was determined using the static chamber absorption method. A cup containing 2% boric acid solution was placed in the static chamber for absorption for 60 minutes. After collecting the absorbent, bromocresol green and methyl red indicators were added, followed by the determination using 0.01 mol·L⁻¹ water. -1 The sulfuric acid was titrated to calculate the emission rate and cumulative emission of NH3.

[0045] (5) Sample processing and analysis Material samples were collected on days 1, 7, and 17. When 50% of the larvae entered the prepupal stage, frass separation was performed. The harvested prepupae were washed with ultrapure water, dried at 60°C for 48 hours to constant weight, and ground into powder for subsequent nutritional analysis. Frass (insect sand) was also sampled and weighed, and stored separately at -80°C (for microbial community structure analysis), air-dried (for determining basic physicochemical properties), and at 4°C (for testing fresh sample indicators).

[0046] (6) Indicator Explanation: Black soldier fly larvae are rich in crude protein and crude fat, making them a high-quality feed for aquatic animals, poultry, and pigs. Using black soldier fly larvae as protein feed not only improves feed quality but also enhances the health and growth performance of farmed animals. The efficiency and resource utilization potential of BSF larvae in treating organic waste were evaluated by calculating indicators such as Waste Reduction Rate (WR), Substrate-to-BSF Prepupal Biomass Conversion Ratio (SBC), and Bioconversion Rate (BR). Simultaneously, the Waste Reduction Index (WRI) represents the time required for BSSF larvae to reduce a specific amount of waste. A higher WRI value indicates better reduction efficiency.

[0047] The formula is as follows:

[0048] (7) Global Warming Potential (GWP) is an important indicator for measuring the impact of greenhouse gases on global warming.

[0049]

[0050] The results are shown in Table 1 and Figure 2 As shown.

[0051] Figure 2 The performance of BSFL in length and weight gain at each sampling point throughout the experiment was shown. Based on observations, the starting weight of all treatments was approximately 0.77 mg. On day 11, the MIX treatment group showed a rapid increase in both body length and weight compared to the other groups, a trend that continued until the last sampling. The MIX group exhibited better performance compared to the other treatments, while the CK treatment group produced the smallest larvae, and the CT treatment group produced the lightest larvae. At the end of the experiment, the MIX group had the longest larvae, reaching 13.93 mm, followed by the CT, HT, and CK groups. Compared to the CK group, the MIX group showed an increase of 7% in larval length and 17.37% in weight. P >0.05).

[0052]

[0053] The effects of different plant tannins on larval yield, crude fat, crude protein, organic matter, and dry matter are shown in Table 1. At the end of the experiment, the total larval yield harvested from the CT, HT, and MIX treatment groups was higher than that from the CK treatment, increasing by 0.8% ( P >0.05), 2.52% P >0.05) and 12.31% ( P<0.05), and the total yield of the MIX group was 104.21±5.22 g. Regarding the nutritional composition of the harvested BSF larvae, the larvae produced in the MIX treatment had the highest crude fat content, which was significantly increased by 87% compared to the CK group (<0.05). P <0.05). However, there were no significant differences in crude fat and dry matter among the treatments.

[0054]

[0055] According to the data shown in Table 2, compared with the control group (CK), the experimental groups (including CT, HT, and MIX treatments) all showed a certain degree of improvement in biotransformation efficiency (BR). Particularly noteworthy was the MIX treatment group, which exhibited the highest biotransformation efficiency, with a significant increase of 20.91%. P <0.05). Furthermore, in the assessment of substrate-to-black soldier fly prepupa biomass conversion ratio (SBC), the MIX treatment also ranked first, followed by HT, CT, and CK. Specifically, compared with the CK treatment, the SBC of the HT and CT treatments increased by 7.09% and 5.1%, respectively. P >0.05); while the SBC of the MIX treatment was significantly improved by 16.02% ( P <0.05). However, there were no significant differences in waste reduction rate and waste reduction index among the treatments.

[0056] like Figure 3 The pH and EC changes in the insect-sand mixture during the experiment showed that the pH of all treatment groups increased significantly, and stabilized at around pH=8.8 on day 17, with no significant differences between treatments. Meanwhile, the EC of all treatment groups showed a decreasing trend, with the CK group showing the largest decrease. Only the CT group showed a significant difference compared to the CK group. P <0.05). At the end of the experiment, all treatments were within 2-2.20 ms cm. -1 between.

[0057]

[0058] Table 3 shows that the organic carbon and total nitrogen contents of all black soldier fly treatments decreased significantly during the conversion of chicken manure. The CT group showed the largest decrease in organic carbon, reaching 25.38%, while the MIX group showed the largest decrease in total nitrogen, at 20.35%. After conversion, compared with the control group, the OC content in the CT group decreased by 9.27% ​​(…). P >0.05), while the TN content increased by 10.56% ( P<0.05). At the end of the trial, the CN ratios of all treatments decreased sharply, with final ratios ranging from 13.53 to 16.48. The CT group showed a 78.01% decrease from the initial ratio, followed by HT (77.28%), CK (73.13%), and MIX (72.40%). Compared with CK, the CN ratios of CT and HT decreased by 17.90% on day 17. P <0.05) and 13.17% ( P <0.05).

[0059] Daily emissions of NH3 such as Figure 4 As shown in (a), in the early stages of the experiment, the daily emissions of all treatment groups generally showed a downward trend; by the middle of the experiment, the daily emissions of each treatment group slightly rebounded; subsequently, the daily emissions decreased again to a lower level. Figure 4 (b) Analysis of the cumulative NH3 emissions data shows that the cumulative emissions of the CT and HT treatment groups were significantly lower than those of the control group (CK) throughout the entire experimental period. Specifically, at the end of the experiment, compared with the control group (CK), the cumulative NH3 emissions of the CT, HT, and MIX treatment groups in the experimental groups were reduced by 10.68% ( P <0.01), 8.22% P <0.05) and 1.75% ( P >0.05). Furthermore, the cumulative NH3 emissions from the CK treatment reached 2652.45 ± 22.50 mg·kg⁻¹. - ¹.

[0060] Figure 5 (a) and Figure 5 The results in (b) indicate that the CO2 emission rate in the CK group remained relatively high throughout the experiment, while the CO2 emission rate in the CT group was generally lower. Furthermore, all treatment groups showed a consistent trend of first decreasing and then increasing CO2 emission rates with increasing experimental time. The cumulative emissions differed significantly among the treatment groups (P<0.05), with the CK group exhibiting the highest cumulative emissions. Notably, the emissions from the CT, HT, and MIX groups were 13.98% lower than those from the CK group. P <0.05), 5.64% P >0.05) and 6.61% ( P >0.05). Furthermore, the cumulative emissions from the CT group were only 36.52 ± 1.48 g·kg. -1 .

[0061] Depend on Figure 6 The global warming potential (GWP) of the control (CK) group was 8.64 ± 0.07 kg CO2-eq·t. -¹, expressed in carbon dioxide equivalents. The GWP in the CT group was 9.68% lower than that in the CK group ( P <0.01), which is 7.80±0.11 kgCO2 - eq·t - ¹, Meanwhile, the HT and MIX groups decreased by 7.31% respectively ( P <0.05) and 3.63% ( P >0.05). Between experimental groups ( P The difference was statistically significant (<0.05).

[0062] In summary, the results above show that the application of this invention in promoting the efficient utilization of carbon and nitrogen nutrients and reducing emissions in black soldier fly larvae culture substrates is specifically reflected in the following aspects: (1) During the conversion of chicken manure by black soldier flies, the MIX treatment group showed superior growth performance compared to other treatment groups (CT, HT, and CK). Simultaneously, the MIX treatment group significantly increased the total larval yield (by 12.31%). P <0.05), and its larvae have the highest crude fat content.

[0063] (2) Compared with the control group (CK), all experimental groups (CT, HT and MIX treatments) showed improved biotransformation rates, with the MIX treatment group exhibiting the highest biotransformation efficiency, significantly increasing by 20.91% ( P <0.05). Regarding the substrate-to-black soldier fly prepupa biomass conversion ratio (SBC), the MIX treatment also showed the best performance, with a significant increase in SBC of 16.02% ( P <0.05).

[0064] (3) After black soldier fly transformation, the pH value of the insect sand in all treatments significantly increased to around 8.8, while the EC value significantly decreased to around 2.1 ms / cm. The lower EC value indicates a lower salt content in the insect sand, which means that the content of harmful substances (such as heavy metal ions) in the insect sand is reduced, indicating that the quality of the insect sand has been improved. A stable alkaline environment and a lower EC value are conducive to the subsequent utilization of the insect sand, such as as a soil conditioner or fertilizer.

[0065] (4) The CT and HT treatment groups significantly reduced the cumulative emissions of NH3, decreasing by 8.22% compared to the control group (CK). P <0.05) and 10.68% ( P <0.01), while the reduction in the MIX treatment group was not significant (1.75%). P >0.05).

[0066] (5) The CK group had the highest cumulative CO2 emissions. Compared with the CK group, the CT group significantly reduced the cumulative CO2 emissions (by 13.98%). P <0.05), while the reduction in the HT group and MIX group did not reach a statistically significant level (reduced by 5.64% and 6.61% respectively), P Although the emission reduction rate was >0.05%, it still showed a certain emission reduction effect.

[0067] (6) Black soldier fly can effectively reduce the content of organic carbon and total nitrogen during the conversion of chicken manure, and significantly change the carbon-nitrogen ratio. Among them, (compared with the CK group) the CT group showed outstanding performance in terms of reducing organic carbon and increasing total nitrogen after conversion, and its carbon-nitrogen ratio decreased the most.

[0068] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including modifications made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A method for promoting the growth of black soldier fly larvae and / or improving the quality of insect-strewn sand, characterized in that, Includes the following steps: Black soldier fly larvae were inoculated into a substrate composed of plant tannin extracts, poultry and livestock manure and carbon-containing materials. Black soldier fly larvae were cultured under constant temperature, constant humidity, light-proof and open conditions. After the culture was completed, the larvae and larval sand were collected. The plant tannin extract is one or both of chestnut wood tannin extract and white pine wood tannin extract; On a dry matter basis, the mass of the plant tannin extract is 0.5% of the total mass of the livestock and poultry manure and the carbon-containing materials.

2. The method for promoting the growth of black soldier fly larvae and / or improving the quality of insect-sand as described in claim 1, characterized in that: The plant tannin extract is a mixture of white pine tannin extract and chestnut tannin extract in a mass ratio of 1:(0.5-1); and / or, The tannin extract contains 70%–75% tannins by mass; and / or The plant tannin extract is an aqueous extract; and / or, The livestock and poultry manure is chicken manure, cow manure, pig manure, or duck manure; and / or, The carbon-containing material is crop straw or wood material; and / or, The carbon-to-nitrogen ratio of the substrate is (15–25):1; and / or, The substrate has a water content of 60%–75%; and / or, The substrate has a pH of 5–10; and / or, The breeding was carried out at an ambient temperature of 25–30°C.

3. The method for promoting the growth of black soldier flies and / or improving the quality of insect-sand according to any one of claims 1-2, characterized in that: The promotion of black soldier fly growth is manifested in at least one aspect of the following (A1) to (A4): (A1) Increases the body length of black soldier fly larvae; (A2) Increases the weight of black soldier fly larvae; (A3) Increase the total yield of black soldier fly larvae; (A4) Increases the crude fat content of black soldier fly larvae; The improvement in the quality of insect-infested sand is reflected in at least one of increasing the pH value of the insect-infested sand, reducing the electrical conductivity of the insect-infested sand, and reducing the nitrate nitrogen content of the insect-infested sand.

4. A method for cultivating black soldier fly larvae to enhance their biotransformation capacity, characterized in that, Includes the following steps: Black soldier fly larvae were inoculated into a substrate composed of plant tannin extracts, poultry and livestock manure and carbon-containing materials. Black soldier fly larvae were cultured under constant temperature, constant humidity, light-proof and open conditions. After the culture was completed, the larvae and larval sand were collected. The plant tannin extract is one or both of chestnut wood tannin extract and white pine wood tannin extract; On a dry matter basis, the mass of the plant tannin extract is 0.5% of the total mass of the livestock and poultry manure and the carbon-containing materials.

5. The method for cultivating black soldier fly larvae to enhance their biotransformation capacity according to claim 4, characterized in that: The plant tannin extract is a mixture of white pine tannin extract and chestnut tannin extract in a mass ratio of 1:(0.5-1); and / or, The tannin extract contains 70%–75% tannins by mass; and / or The plant tannin extract is an aqueous extract; and / or, The livestock and poultry manure is chicken manure, cow manure, pig manure, or duck manure; and / or, The carbon-containing material is crop straw or wood material; and / or, The carbon-to-nitrogen ratio of the substrate is (15–25):1; and / or, The substrate has a water content of 60%–75%; and / or, The substrate has a pH of 5–10; and / or, The breeding was carried out at an ambient temperature of 25–30°C.

6. The black soldier fly culturing method for enhancing the biotransformation capacity of black soldier flies according to any one of claims 4-5, characterized in that: The enhancement of the black soldier fly's biotransformation capacity is reflected in at least one aspect of the following (B1) to (B2): (B1) Improve the bioconversion rate and / or waste reduction rate of black soldier flies; (B2) Improve the conversion ratio of substrate to black soldier fly prepupae biomass.

7. A method for black soldier fly farming that reduces carbon and nitrogen gas emissions or improves the utilization rate of carbon and nitrogen nutrients in livestock and poultry manure, characterized in that, Includes the following steps: Black soldier fly larvae were inoculated into a substrate composed of plant tannin extracts, poultry and livestock manure and carbon-containing materials. Black soldier fly larvae were cultured under constant temperature, constant humidity, light-proof and open conditions. After the culture was completed, the larvae and larval sand were collected. The plant tannin extract is one or both of chestnut wood tannin extract and white pine wood tannin extract; On a dry matter basis, the mass of the plant tannin extract is 0.5% of the total mass of the livestock and poultry manure and the carbon-containing materials.

8. The black soldier fly farming method according to claim 7, which reduces carbon and nitrogen gas emissions or improves the utilization rate of carbon and nitrogen nutrients in livestock and poultry manure, is characterized in that: The plant tannin extract is a mixture of white pine tannin extract and chestnut tannin extract in a mass ratio of 1:(0.5-1); and / or, The tannin extract contains 70%–75% tannins by mass; and / or The plant tannin extract is an aqueous extract; and / or, The livestock and poultry manure is chicken manure, cow manure, pig manure, or duck manure; and / or, The carbon-containing material is crop straw or wood material; and / or, The carbon-to-nitrogen ratio of the substrate is (15–25):1; and / or, The substrate has a water content of 60%–75%; and / or, The substrate has a pH of 5–10; and / or, The breeding was carried out at an ambient temperature of 25–30°C.

9. A method for raising black soldier fly larvae according to any one of claims 7-8, characterized in that: The reduction of carbon and nitrogen emissions is reflected in at least one aspect of the following (C1) to (C5): (C1) Reduce cumulative NH3 emissions; (C2) Reduce cumulative CO2 emissions; (C3) Reduce cumulative CH4 emissions; (C4) Reduce cumulative N2O emissions; (C5) Reduce global warming potential.

10. The use of plant tannin extracts in at least one of the following: 1) Improve the growth performance of black soldier flies; 2) Improve the utilization rate of carbon and nitrogen nutrients in livestock and poultry manure in black soldier fly larvae culture substrate; 3) Reduce carbon and nitrogen emissions from livestock and poultry manure during black soldier fly farming; 4) Improve the biotransformation performance of black soldier flies; 5) Improve the quality of insect-infested sand; The plant tannin extract is one or both of chestnut wood tannin extract and white pine wood tannin extract; The substrate for raising the black soldier fly is poultry and livestock manure and carbon-containing materials; On a dry matter basis, the mass of the plant tannin extract is 0.5% of the total mass of the livestock and poultry manure and the carbon-containing materials.

11. The application according to claim 10, characterized in that: The plant tannin extract is a mixture of white tannin extract and chestnut tannin extract in a mass ratio of 1:(0.5-1).

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