Method and integrated system for reducing carbon dioxide emission by using tenebrio molitor substrate fermentation

Abstract

The application discloses a method and integrated system for reducing carbon dioxide emission by using tenebrio molitor matrix fermentation, and the steps of the method comprise the following steps: putting tenebrio molitor in crop biomass for pretreatment to obtain a pile; stacking the pile and then carrying out fermentation; applying the generated carbon dioxide as gas fertilizer during the fermentation process; and using the fermented pile as a cultivation substrate. The method introduces tenebrio molitor into a crop biomass fermentation system, which can not only effectively degrade straw and realize agricultural waste resource utilization, but also significantly reduce the CO2 emission during the fermentation process. The integrated system based on the method couples crop biomass fermentation with greenhouse planting, recycles the generated CO2 as a carbon source for photosynthesis, and can regulate the CO2 supply according to the crop growth demand, thereby further realizing secondary CO2 emission reduction, effectively promoting crop growth, and constructing a low-carbon, high-efficiency and closed-loop ecological agricultural mode, which has significant environmental benefits, resource utilization benefits and production benefits.

Description

Technical Field

[0001] This invention relates to the agricultural field, and more particularly to a method and integrated system for reducing carbon dioxide emissions using mealworm substrate fermentation. Background Technology

[0002] Agricultural biomass mainly refers to byproducts generated during agricultural production, with straw being the primary component, yielding a massive annual output of nearly 1 billion tons. Currently, straw treatment methods primarily include five utilization pathways: direct return to the field, feed production, fuel production, substrate production, and raw material production. However, open burning and natural decomposition remain problems in some areas, with these two methods generating an average annual greenhouse gas emission of 5.6 × 10⁻⁶ tons. 7 tCO2e brings a heavy carbon emission burden.

[0003] In contrast, straw fermentation technology is becoming an important direction for resource utilization. However, existing research mainly focuses on fermentation efficiency and substrate quality, paying insufficient attention to the control of carbon emissions during the fermentation process, and generally relies on exogenous commercial microbial agents, resulting in problems such as high cost and limited environmental adaptability.

[0004] Yellow mealworms ( Tenebrio molitor Insects are widely used resource insects with significant value in the food, health, pharmaceutical, and feed industries. Their excrement is rich in functional microorganisms and incompletely degraded extracellular enzyme systems, exhibiting outstanding biological activity; however, there are currently no reports on its use for substrate fermentation of agricultural waste. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for the resource utilization of agricultural waste based on mealworm substrate fermentation, thereby achieving the goal of reducing carbon dioxide emissions. The second purpose is to provide an integrated system that couples and coordinates the fermentation system with the planting system for this method.

[0006] Technical solution: The method for reducing carbon dioxide emissions using mealworm substrate fermentation as described in this invention includes the following steps: (1) Pretreatment of crop biomass by adding yellow mealworms to obtain a pile; (2) After stacking the piles in windrows, fermentation is carried out; (3) The carbon dioxide produced during fermentation is used as a gas fertilizer, and the fermented pile is used as a cultivation substrate.

[0007] Preferably, the crop biomass in step 1 is dried straw with a length of 0.1 to 0.5 cm; more preferably, the straw is selected from any one or more of rice straw, wheat straw, and corn straw.

[0008] Preferably, in step 1, the mealworms are 12-18 days old, with a body length of 0.8-1.2 cm, and the release quantity is 20,000-180,000 per ton of crop biomass; more preferably, the release quantity is 100,000 per ton of crop biomass.

[0009] Preferably, the preprocessing time in step 1 is 8 to 12 days.

[0010] Preferably, step 2 includes: adjusting the humidity of the pile to 75-85%, and fermenting after stacking in windrows; more preferably, the fermentation time is 20-30 days; more preferably, when the pile is stacked in windrows, the specifications are: bottom width 1.0-1.4 m, top width 0.4-0.8 m, and height 0.6-1.0 m.

[0011] The integrated system for the aforementioned method described in this invention includes a fermentation shed and a greenhouse, which are connected by a pipe.

[0012] Preferably, the passage pipe is provided with a ventilation adjustment structure, which includes a butterfly valve, the valve stem of which is connected to the output shaft of the motor via a coupling, and the motor is fixed to the base; more preferably, the motor is a stepper motor and the coupling is a flexible coupling, which can ensure the coaxiality of power transmission and realize the precise adjustment of the butterfly valve opening from 0 to 90°.

[0013] Preferably, one or more carbon dioxide sensors are installed in both the fermentation shed and the greenhouse, and one or more light sensors are also installed in the greenhouse. The carbon dioxide sensors and light sensors are both connected to the main controller, and the main controller is connected to the stepper motor control.

[0014] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: 1. The method of the present invention introduces yellow mealworms into the crop biomass fermentation system, which can not only effectively degrade straw and realize the resource utilization of agricultural waste, but also significantly reduce CO2 emissions during the fermentation process under the preferred amount of yellow mealworms; 2. The integrated system of the present invention couples crop biomass fermentation with greenhouse planting, and recovers and reuses the CO2 generated by fermentation as a carbon source for crop photosynthesis. It can also regulate CO2 supply according to the needs of crop growth, effectively promote crop growth on the basis of further achieving secondary CO2 emission reduction, and construct a low-carbon, high-efficiency, closed-loop ecological agricultural model, which has significant environmental benefits, resource utilization benefits and production benefits. Attached Figure Description

[0015] Figure 1 A graph showing the statistical results of CO2 emissions and total emissions for each treatment group at different times; Figure 2 A graph showing the statistical results of the pile temperature and cumulative pile temperature at different times for each treatment group; Figure 3 A graph showing the statistical results of the degree of putrefaction of the pile body at different times for each treatment group; Figure 4 The graph shows the results of various indicators of the substrate after fermentation under different amounts of mealworms. A represents the germination index, B represents the physical properties, C represents the pH value, D represents the EC value, and E represents the cellulose and hemicellulose content. Figure 5 Figure showing the effect of rice straw fermentation emissions on tomato seedling growth. Figure 6 A graph showing the statistical results of the consumption efficiency of CO2 emitted from rice straw fermentation for the growth of tomato seedlings; Figure 7 A schematic diagram of an integrated system for reducing carbon dioxide emissions through substrate fermentation of yellow mealworms; Figure 8 This is a schematic diagram of the connection structure between the butterfly valve and the motor in the integrated system. Detailed Implementation

[0016] The technical solution of the present invention will be further described below.

[0017] Example 1: Screening of the dominant mealworm population in a method of reducing carbon dioxide emissions through mealworm substrate fermentation Dry rice straw was shredded to a length of approximately 0.2 cm using a shredder. A control group (CK) without added mealworms was used. Three treatment groups were established: 100 (T100), 500 (T500), or 900 (T900) mealworms were added to every 5 kg of dry rice straw for pretreatment in breathable plastic bags for 10 days. The mealworms were 15 days old and 1 cm in length. After pretreatment, water was added to the straw pile to adjust the humidity to approximately 80%, and the pile was placed in a small fermentation chamber (length × width × height: 54 × 38 × 36 cm) for fermentation at room temperature.

[0018] The temporal changes in CO2 emissions, pile temperature, and degree of humification were measured. On day 30 of fermentation, the germination index, pH value, electrical conductivity (EC) value, and cellulose and hemicellulose content of each treatment were measured.

[0019] 1. The impact of mealworm release quantity on CO2 emissions A PLT400 pump-suction gas detector (purchased from Shenzhen Pulitong Electronic Technology Co., Ltd.) was used to measure CO2 emissions daily.

[0020] The statistical results of CO2 emissions and total CO2 emissions at different times for each treatment group are as follows: Figure 1 As shown, there was no significant correlation between CO2 emissions from the fermentation pile and the amount of mealworms introduced. However, throughout the entire fermentation process, the T500 treatment exhibited lower CO2 emissions at each stage of fermentation, and also had the lowest total CO2 emissions, which were 17.6% lower than the control (CK).

[0021] 2. The effect of mealworm feeding amount on fermentation pile temperature The temperature at five points (front, back, left, right, and center) inside the fermentation chamber was measured using a mercury thermometer, and the average value was taken as the temperature of the treatment pile.

[0022] Statistical results of reactor core temperature and cumulative reactor core temperature at different times for each treatment group are as follows: Figure 2 As shown, at most measurement time points, except for CK, the pile temperature was negatively correlated with the amount of mealworms released; that is, the more mealworms released, the lower the pile temperature. The cumulative pile temperature from highest to lowest was: T100 > CK > T500 > T900. On day 4 of fermentation, the pile temperature of treatments T100, CK, and T500 reached its peak; while the T900 treatment reached its highest temperature on day 5 of fermentation.

[0023] 3. The effect of mealworm feeding amount on the degree of decomposition of fermentation pile The degree of putrefaction of the pile body was expressed as the E4 / E6 ratio. The determination method was as follows: 1 g of naturally air-dried pile body sample was weighed and placed in a centrifuge tube. 50 mL of 0.5 M NaOH was added and shaken for 2 h. After centrifugation at 6000 rpm for 15 min, the supernatant was taken and the absorbance at wavelengths of 472 nm (E4) and 664 nm (E6) was measured using a Hitachi UV-2000 spectrophotometer, and the E4 / E6 ratio was calculated.

[0024] Statistical results of the degree of putrefaction of the pile body at different times for each treatment group are as follows: Figure 3 As shown, after 30 days of fermentation, there was no significant difference in the E4 / E6 ratio among the treatments, indicating that the degree of putrefaction was comparable.

[0025] 4. Effects of mealworm feeding amount on germination index and physicochemical properties of fermentation pile Germination index of Shanghai bok choy seeds (purchased from Shouhe Horticulture Company) was determined. The method was as follows: 20.0 g of air-dried stock was mixed with 100.0 mL of ultrapure water and placed on a shaker for 2 h. The mixture was then filtered using qualitative filter paper. 6.0 mL of the filtrate was added to 9 cm diameter petri dishes lined with sterile filter paper. 50 Shanghai bok choy seeds were placed in each dish. Ultrapure water was used as a control. Each treatment was repeated in triplicate. The dishes were incubated at 26℃ for 48 h. Root length was measured, germination rate was calculated, and the germination index was calculated using the following formula: Germination index = (germination rate of pile leachate treatment × average root length of pile leachate treatment) / (germination rate of control × average root length of control), where germination rate = number of germinated seeds / total number of seeds.

[0026] pH values ​​were measured using a pH meter (purchased from Shanghai Instrument & Electronics Scientific Instruments Co., Ltd.), EC values ​​were measured using a conductivity meter (purchased from Shanghai Instrument & Electronics Scientific Instruments Co., Ltd.), and cellulose and hemicellulose contents were determined by titration. A brief description of the procedure is as follows: 1. Cellulose Content Determination: Weigh 0.10 g of sample, grind it, and place it in a 15 mL graduated test tube. Add 5 mL of acetic acid-nitric acid mixture (volume ratio 1:1), cap, and heat in a boiling water bath for 30 min. Transfer the entire mixture to a 50 mL plastic graduated centrifuge tube, dilute with distilled water to the 45 mL mark, cool, and centrifuge at 8000 r / min for 15 min. Discard the supernatant. Add distilled water again to the 45 mL mark, centrifuge, discard the supernatant, and repeat the washing process twice. Dry the precipitate in an 80℃ oven. Take the dried sample, add 10 mL of the mixture, shake well, and heat in a boiling water bath for 15 min. Transfer the entire sample to a clean Erlenmeyer flask and cool. Add 5 mL of 20% potassium iodide (KI) solution and titrate with 0.2 mol / L sodium thiosulfate solution until the solution just turns blue and does not fade within half a minute. Perform the same operation with a blank control without straw. The cellulose content is calculated using the following formula: Cellulose content = k × (a − b) / n × 24; Where k is the concentration of sodium thiosulfate, mol / L; a is the volume of sodium thiosulfate consumed in the blank titration, mL; b is the volume of sodium thiosulfate consumed in the sample titration, mL; and n is the sample mass, g.

[0027] 2. Hemicellulose content determination: Weigh 0.10 g of sample into a 100 mL beaker, add 10 mL of 80% calcium nitrate solution, heat to boiling for 5 min, dilute and filter. Wash the precipitate three times with distilled water and dry at 80℃. Transfer the dried precipitate to a 15 mL graduated test tube, add 10 mL of 2 mol / L HCl, heat in a boiling water bath for 45 min, transfer the entire solution to a 150 mL Erlenmeyer flask, add 1 drop of phenolphthalein, neutralize with NaOH until a rose-red color appears, filter, wash the residue with distilled water, combine the filtrate and washings, and dilute to volume. Record the total volume. Take eight 20 mL stoppered graduated test tubes and add 0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, and 1.4 mL of 1.0 mg / mL glucose standard solution, respectively. Add distilled water to each tube to a final volume of 2 mL. Add 1.5 mL of DNS reagent to each tube, shake well, and incubate in a boiling water bath for 5 min. Cool and bring the volume to 15 mL. Measure the absorbance at 540 nm. Plot a standard curve with glucose content (mg) on ​​the x-axis and absorbance on the y-axis. Take 2 mL of the above filtrate, add 1.5 mL of DNS reagent, incubate in a boiling water bath for 5 min, cool and bring the volume to 15 mL. Measure the absorbance at 540 nm. Calculate the reducing sugar content in the sample based on the standard curve. Hemicellulose content (%) = m 还原糖 ×0.9 / m 样品 .

[0028] Measurement of the physicochemical properties of the matrix: Use a container with a known volume (measured volume V) (weighed as W0); fill a beaker or similar container with the naturally air-dried matrix, level the surface, and weigh as W1; seal the mouth of the beaker with two layers of gauze, then soak the beaker or similar container filled with matrix in water for 24 hours, remove it and weigh as W2 (excluding the weight of the gauze); seal it with gauze again, invert the container, and allow the water in the container to flow out freely. After 2 hours, when no water seeps out of the container, weigh as W3 (excluding the weight of the gauze). Calculate the bulk density, total porosity, aeration porosity (macroporosity), water-holding porosity (microporosity), and the ratio of macroporosity to microporosity using the following formulas: Quantity = (W1 - W0) / V; Total porosity (%) = (W2 - W1) / V × 100%; Ventilation porosity (%) = (W2 - W3) / V × 100%; Water-holding porosity (%) = (W3 - W1) / V × 100%; Large-to-small porosity ratio = air porosity / water-holding porosity.

[0029] The measurement results of the above indicators are as follows: Figure 4As shown, the results indicate that the amount of mealworms released has no significant effect on the germination index and the physicochemical properties of the substrate; the measured values ​​of CK, T500, and T900 are all within the suitable range specified in the standard (Vegetable Seedling Substrate: NY / T 2118-2012 [S], 2012.).

[0030] Example 2: Evaluation of CO2 Consumption from Substrate Fermentation of Yellow Mealworms by Planting System Coupling The method described in Example 1 was used to carry out the substrate fermentation of rice straw with yellow mealworms. Three groups were set up: T100, T500 and T900, with the control group (CK) without the addition of yellow mealworms.

[0031] The test material consisted of seeds that had been soaked and germinated before being planted in seedling trays containing vegetable seedling substrate, 300 μmol m -2 s -1 Three-leaf, one-heart tomato seedlings (provided by the Facility Horticulture Laboratory of Nanjing Agricultural University) were cultivated under fluorescent lamps. A simple semi-enclosed seedling room (50 cm long, 25 cm wide, and 25 cm high) was constructed using 60-cell trays with a transparent sealing cover, containing 30 seedlings per tray. A small fermentation chamber was connected to the seedling room via a 20 mm diameter flexible hose. A 6 mm diameter vent was installed at the far end of the seedling room from the air vent, allowing for atmospheric ventilation; the vent opening was adjustable. During fermentation, the relative CO2 consumption rate of the tomato seedlings was measured at different time points. Each fermentation device (small fermentation chamber) corresponded to one tray of seedlings, with three replicates per treatment. Tomato seedlings not connected to the fermentation device served as the control (CK1).

[0032] 1. The impact of rice straw fermentation emissions on tomato seedling growth The results are as follows Figure 5 As shown, CO2 emitted from the fermentation pile and introduced into the seedling room significantly promoted the growth of tomato seedlings. On the 12th, 16th and 21st days of aeration, the average plant height of the aerated group (average values ​​of CK, T100, T500 and T900) increased by 2.5%, 9.9% and 10.3% respectively compared with the plant height of CK1.

[0033] 2. CO2 consumption rate determination Open the hose to allow ventilation, close the outlet and seal for 3 minutes. Use a pump-type gas detector to measure the CO2 concentration at the outlet and record it as C1. Then close the hose, keep the detector and outlet in the same state, let it stand for 3 minutes, and read the CO2 concentration again, recording it as C2. The relative consumption rate (RCR) is calculated using the following formula: RCR = (C1 - C2) / C1.

[0034] On fermentation days 7, 8, 9, 10, 13, 15, and 17, the relative gas consumption rates of tomato seedlings in the aeration groups (including CK, T100, T500, and T900) were as follows: Figure 6 As shown, the average relative CO2 consumption rate (Average-RCR) of tomato seedlings in the aerated group was in the range of 11.1% to 24.3% over 3 minutes. This result indicates that coupling the fermentation device with the planting system can reduce CO2 emissions during fermentation for a second time.

[0035] Example 3: Construction of an integrated system for carbon dioxide emission reduction through substrate fermentation of yellow mealworms Figure 7 , 8 The attached diagrams are labeled as follows: exhaust port-1, fermentation chamber-2, inlet / outlet-3, carbon dioxide sensor-4, through pipe-5, main controller-6, butterfly valve-7, coupling-8, motor-9, base-10, greenhouse-11, light sensor-12, valve stem-13.

[0036] The integrated system consists of a fermentation chamber 2, a ventilation pipe 5, and a greenhouse 11. The ventilation pipe 5 is equipped with a ventilation regulating structure, including a butterfly valve 7, whose valve stem 13 is connected to the output shaft of a motor 9 via a coupling 8. The motor 9 is fixed to a base 10. At the same time, a carbon dioxide sensor 4 is installed in both the fermentation chamber 2 and the greenhouse 11, located in the middle of the greenhouse. A light sensor 12 is also installed in the middle of the greenhouse 11. Both the carbon dioxide sensor 4 and the light sensor 12 are wirelessly connected to the main controller 6, which in turn controls the motor 9.

[0037] In this integrated system, motor 9 is a stepper motor and coupling 8 is a flexible coupling, which can ensure the coaxiality of power transmission and realize the precise adjustment of the butterfly valve opening from 0 to 90°.

[0038] When the integrated system is working, firstly, dry rice straw is taken and crushed to a length of about 0.2 cm using a shredder. Then, 15-day-old yellow mealworms with a body length of 1 cm are introduced at a ratio of 100,000 per ton of rice straw. After 10 days of pretreatment, the pile is obtained. The humidity of the pile is adjusted to 80%, and it is stacked in a windrow with a bottom width of 1.2 m, a top width of 0.6 m, and a height of 0.8 m. Fermentation is carried out at room temperature. CO2 sensors monitor the CO2 concentration in fermentation chamber 2 and greenhouse 11 in real time, and light sensors monitor the light intensity in greenhouse 11 in real time. The signals from each sensor are transmitted wirelessly to the main controller 6. The main controller 6 adjusts the motor 9 according to the real-time signals, thereby controlling the opening of the butterfly valve to realize the secondary utilization of CO2 generated during fermentation. This promotes the growth of plants in greenhouse 11 and reduces CO2 emissions. At the same time, the fermented pile can also be used as a soilless cultivation substrate for planting plants in greenhouse 11.

Claims

1. A method for reducing carbon dioxide emissions using mealworm substrate fermentation, characterized in that the steps include... include: (1) Pretreatment of crop biomass by adding yellow mealworms to obtain a pile; (2) After stacking the piles in windrows, fermentation is carried out; (3) The carbon dioxide produced during fermentation is used as a gas fertilizer, and the fermented pile is used as a cultivation substrate.

2. The method according to claim 1, characterized in that, In step 1, the crop biomass is dry straw with a length of 0.1 to 0.5 cm.

3. The method according to claim 2, characterized in that, The straw is selected from one or more of rice straw, wheat straw, and corn straw.

4. The method according to claim 1, characterized in that, In step 1, the mealworms are 12-18 days old, with a body length of 0.8-1.2 cm, and the release quantity is 20,000-180,000 mealworms per ton of crop biomass.

5. The method according to claim 1, characterized in that, The preprocessing time in step 1 is 8~12 days.

6. The method according to claim 1, characterized in that, Step 2 includes: adjusting the humidity of the pile to 75-85%, and then fermenting it by stacking it in windrows.

7. The method according to claim 6, characterized in that, The fermentation time is 20-30 days.

8. An integrated system for the method according to any one of claims 1 to 7, characterized in that, It includes a fermentation shed (2) and a greenhouse (11), which are connected by a pipe (5).

9. The integrated system according to claim 8, characterized in that, The passage pipe (5) is provided with a ventilation adjustment structure, which includes a butterfly valve (7), whose valve stem (13) is connected to the output shaft of the stepper motor (9) through a coupling (8), and the stepper motor (9) is fixed to the base (10).

10. The integrated system according to claim 9, characterized in that, One or more carbon dioxide sensors (4) are installed in both the fermentation shed (2) and the greenhouse (11). One or more light sensors (12) are also installed in the greenhouse (11). The carbon dioxide sensors (4) and the light sensors (12) are connected to the main controller (6) via signal. The main controller (6) is connected to the stepper motor (9) via control.

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