A method for enhancing the humification and nitrogen fixation of anaerobic fermentation biogas residue and black soldier fly larvae excrement in food waste through exogenous biochemical additives.

Abstract

A method for strengthening the humification and nitrogen fixation of anaerobic fermentation of kitchen waste and black soldier fly feces by exogenous biochemical additives, the method is: the kitchen waste biogas residue and black soldier fly feces are mixed uniformly according to a mass ratio of 3:1 to obtain a compost base material, a conditioner is added, and the initial compost substrate is obtained after uniform mixing, lignocellulose-degrading enzymes or lignocellulose-degrading enzyme-coupled biochemical additives are added to the initial compost substrate, and the compost material is obtained after uniform mixing again; the uniformly mixed compost material is subjected to aerobic composting, and aeration is ensured throughout the composting process, the composting undergoes a complete temperature rising period, a high temperature period, a temperature decreasing period and a maturity period, and the compost product is obtained. The humification index and the proportion of humus substances of the compost product are increased, and the cumulative ammonia emission during the composting process is significantly reduced, and the simultaneous resource utilization of the anaerobic fermentation of kitchen waste and black soldier fly feces is strengthened.

Description

Technical Field

[0001] This invention belongs to the field of organic solid waste treatment, specifically involving a method for enhancing the composting and nitrogen fixation of kitchen waste anaerobic fermentation biogas residue and black soldier fly excrement with exogenous biochemical additives. Background Technology

[0002] The biogas residue produced after anaerobic fermentation of kitchen waste (hereinafter referred to as "kitchen waste biogas residue") is rich in organic matter and nutrients such as nitrogen, phosphorus, and potassium, and is considered an important resource for producing high-quality fertilizer. However, kitchen waste biogas residue has poor hygienic indicators, not only emitting a foul odor but also attracting mosquitoes, flies, and carrying pathogens. Currently, aerobic composting is considered one of the most promising methods for treating kitchen waste biogas residue, aiming to achieve both harmlessness and resource utilization. However, kitchen waste biogas residue has problems such as high water content, low carbon-to-nitrogen ratio, and dense structure, and traditional composting methods often fail to meet the requirements for good humification. Currently, the bioconversion technology of black soldier fly larvae for organic waste such as kitchen waste is widely used and promoted. However, this process also produces a large amount of black soldier fly frass, which contains high levels of organic matter, trace elements, and various amylases, lipases, and proteases, but also suffers from high salinity, foul odor, and high moisture content, requiring further resource utilization treatment.

[0003] Co-composting of food waste biogas residue and black soldier fly larvae excrement can achieve a certain degree of stable transformation between the two. The patent "A method for composting food waste organic slurry anaerobic digestion biogas residue combined with black soldier fly larvae excrement" (CN113105283A) co-composts food waste biogas residue and black soldier fly larvae excrement, and the compost product meets the organic fertilizer standard (NY / T 525-2021). However, this technology does not focus on nitrogen loss reduction and enhanced humification. Food waste biogas residue contains a large amount of macromolecular organic matter, such as lignocellulose. Although the co-processing technology of food waste biogas residue and black soldier fly larvae excrement can partially convert lignocellulose into various humic precursors, the conversion efficiency is low, which in turn affects the efficiency of the co-composting process and the quality of the compost product. Furthermore, during aerobic composting, a large amount of nitrogen is lost in the form of gases (such as ammonia and nitrous oxide). This nitrogen loss also affects the quality of the compost product and causes serious air pollution.

[0004] Theoretically, lignocellulose-degrading enzymes can promote the effective degradation of lignocellulose. The patent "An Active Additive for Promoting the Composting and Maturation of Agricultural Waste and Its Application" (CN105585346A) prepared a composite enzyme preparation containing multiple organic matter-degrading enzymes (including lignocellulose-degrading enzymes) and applied it to agricultural waste (including vegetable leaves, straw, etc.) composting, resulting in improved seed germination rates. However, its application in aerobic composting of kitchen waste sludge has not yet been reported. Regarding the issue of nitrogen loss during composting, the commonly used method is to enhance nitrogen fixation by adding physicochemical additives such as biochar. However, using only physicochemical enhancement methods makes it difficult to further enhance lignocellulose degradation, improve composting efficiency, and enhance the quality of compost products. Simultaneously enhancing composting humification and nitrogen loss reduction is costly and cumbersome. Currently, there are no reports on adding lignocellulose-degrading enzymes to enhance the co-composting of kitchen waste sludge and black soldier fly larvae excrement. This invention aims to achieve simultaneous enhancement of humification and nitrogen fixation in aerobic composting of kitchen waste biogas residue and black soldier fly dung through a biochemically enhanced lignocellulose conversion technology. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of high cost and cumbersome operation in current methods for enhancing composting humification and nitrogen reduction. It provides a method for enhancing the humification and nitrogen fixation of anaerobic fermentation biogas residue and black soldier fly dung co-composting using exogenous biochemical additives. This method involves adding lignocellulose-degrading enzymes or lignocellulose-degrading enzymes coupled with other biochemical additives to the food waste biogas residue-black soldier fly dung co-composting system. This promotes the generation of humic precursors during co-composting, thereby enhancing the humification and nitrogen fixation effects of co-composting.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for enhancing the humification and nitrogen fixation of anaerobic fermentation biogas residue and black soldier fly larvae excrement in food waste through co-composting with exogenous biochemical additives, the method comprising:

[0008] Step 1: Thoroughly mix kitchen waste biogas residue and black soldier fly frass at a mass ratio of 3:1 to obtain compost base material. Control the carbon-nitrogen ratio of the compost base material by adding a conditioner. After mixing the kitchen waste biogas residue, black soldier fly frass, and conditioner evenly, obtain the initial compost substrate. Control the carbon-nitrogen ratio of the initial compost substrate to be 20-30:1 and the moisture content to be 50%-70%. Add lignocellulose degrading enzyme or lignocellulose degrading enzyme coupled with biochemical additives to the initial compost substrate, mix evenly again, and obtain compost material.

[0009] Step 2: Perform aerobic composting on the compost material obtained in Step 1, ensuring that the compost pile completely goes through the heating period, high temperature period, cooling period, and maturation period; use three-dimensional fluorescence spectroscopy to detect and analyze the humification index of the compost pile at the end of composting to determine the humification effect of the compost product; collect and detect the daily emissions of ammonia (NH3) and nitrous oxide (N2O) during the composting process, and determine the nitrogen fixation effect of the compost based on the cumulative emissions of gaseous nitrogen during the composting process.

[0010] Furthermore, in step one, the conditioning agent is one or more of the following: sawdust, straw, vegetable stalks, and garden waste.

[0011] Further, in step one, the lignocellulose degrading enzyme is one or more of laccase, lignin peroxidase, and cellulase, with an enzyme activity of 500 U / g, and the addition amount is 2% of the initial dry weight of the compost substrate.

[0012] Furthermore, in step one, the biochemical additive is a lignocellulose-degrading microbial agent. No requirements are placed on the amount of biochemical additive added.

[0013] Furthermore, in step two, the temperature range during the aerobic composting heating period is from the temperature of the compost material to 50℃, the high-temperature period is when the temperature is above 50℃, the cooling period is from 50℃ to the temperature of the compost pile dropping to room temperature, and the maturation period is after entering room temperature. Among these requirements, the high-temperature period requires a temperature above 55℃ for 3 days or a temperature above 50℃ for 5-7 days, and the maturation period requires a temperature of 7 days or more after entering room temperature. Only when the above requirements are met can the composting be completed.

[0014] Furthermore, in step two, the aerobic composting process maintains the same aeration rate of 0.1-0.4 L / min throughout.

[0015] Furthermore, in step two, the compost pile is turned over once every 2 days during the heating and high-temperature periods, and once every 5-7 days during the cooling and maturation periods.

[0016] The beneficial effects of this invention compared to the prior art are as follows: This invention provides a simple and effective method to enhance the co-composting effect of kitchen waste biogas residue and black soldier fly larvae excrement. By adding lignocellulose degrading enzymes or lignocellulose degrading enzymes coupled with other biochemical additives, the humification and nitrogen fixation of co-composting are promoted simultaneously, thereby enhancing the synchronous resource utilization of kitchen waste biogas residue and black soldier fly larvae excrement. Attached Figure Description

[0017] Figure 1 To account for temperature variations in different composting treatments, CK: no exogenous additives added, BAC: inoculated with 0.5% lignocellulose degrading bacteria, LAC: 2% laccase added, and BL: 0.5% lignocellulose degrading bacteria and 2% laccase added simultaneously.

[0018] Figure 2 To represent the humification index of compost products from different treatments, CK, BAC, LAC, and BL were used. Figure 1 ;

[0019] Figure 3 For the biosource index of compost products from different treatments, CK, BAC, LAC, and BL are used. Figure 1 ;

[0020] Figure 4 The fluorescence region integral ratios of compost products from different treatments are CK, BAC, LAC, and BL. Figure 1 ;

[0021] Figure 5 The cumulative NH3 emissions during different composting processes are CK, BAC, LAC, and BL. Figure 1 ;

[0022] Figure 6 The cumulative N2O emissions during different composting processes are CK, BAC, LAC, and BL. Figure 1 . Detailed Implementation

[0023] The present invention will be further described below with reference to the embodiments.

[0024] In the following examples and comparative examples, the kitchen waste biogas residue used in the aerobic composting experiment was taken from a kitchen waste treatment plant in Harbin City. Its moisture content, pH, conductivity, total carbon, and total nitrogen were 79.79%, 8.74%, 2.49 ms / cm, 31.97%, and 3.81%, respectively. Black soldier fly frass was derived from the excrement of black soldier fly larvae fed with kitchen waste solid residue. Its moisture content, pH, conductivity, total carbon, and total nitrogen were 28.80%, 8.11%, 7.51 ms / cm, 26.82%, and 4.17%, respectively. The conditioner used in the aerobic composting was sawdust, which was taken from a wood processing plant in Harbin City. Its moisture content, total carbon, and total nitrogen were 5.53%, 45.74%, and 0.44%, respectively. The lignocellulose-degrading microbial agent was purchased from a biotechnology company in Weihai, Shandong. The agent is a compound microbial agent mainly composed of Bacillus thermophilus, Bacillus subtilis, and Bacillus licheniformis, with an effective viable count ≥ 5 × 10⁻⁶. 8 CFU / g. Laccase was purchased from a chemical products company in Henan Province, with an enzyme activity of 500 U / g. The following examples were conducted in the laboratory. Three-dimensional fluorescence analysis was performed on compost products with different treatments. The humification index HIX, biogenic index BIX, and the proportion of each fluorescent region were detected and analyzed. The cumulative emissions of NH3 and N2O during the composting process were also detected.

[0025] The sawdust used in the following examples and comparative examples and the laccase used in the examples are all representative, specifically in that (1) sawdust has a high carbon-to-nitrogen ratio, a wide range of applications and is easy to obtain, making it an easily accessible and efficient composting conditioner; (2) lignin in lignocellulose is difficult to degrade, and lignin acts as a supporting framework to protect and reinforce cellulose and hemicellulose, thereby affecting the degradation of cellulose and hemicellulose. Therefore, lignin-degrading enzymes are selected as the representative enzyme system for lignocellulose degrading enzymes. Laccase has a wide range of substrate adaptability and environmental tolerance. Compared with other lignin-degrading enzymes, laccase can more directly reflect the role of lignocellulose degrading enzymes in the composting process in the composting system.

[0026] Example 1

[0027] (1) Based on the fresh weight, the kitchen waste biogas residue, black soldier fly larvae excrement and sawdust are mixed evenly in a ratio of 3:1:1 to obtain the initial composting substrate. Laccase (accounting for 2% of the dry weight of the initial composting substrate) is added to the initial composting substrate and mixed evenly again to obtain material 1, denoted as LAC.

[0028] (2) The material 1 obtained in step (1) is subjected to aerobic composting. The aeration rate during composting is 0.4 L / min. The compost is turned over once every 2 days in the early stage and once every 5-7 days thereafter. The external water bath of the compost is used for heat preservation to reduce the heat loss inside the compost and ensure that the compost completely goes through the heating period, high temperature period, cooling period and decomposition period. The composting duration is 40 days.

[0029] Example 2

[0030] (1) Based on the fresh weight, the kitchen waste biogas residue, black soldier fly larvae excrement and sawdust were mixed evenly in a ratio of 3:1:1 to obtain the initial composting substrate. Lignocellulose degrading bacteria (0.5% of the dry weight of the initial composting substrate) and laccase (2% of the dry weight of the initial composting substrate) were added to the initial composting substrate and mixed evenly again to obtain material 2, denoted as BL.

[0031] (2) The material 2 obtained in step (1) is subjected to aerobic composting. The aeration rate during composting is 0.4 L / min. The compost is turned over once every 2 days in the early stage and once every 5-7 days thereafter. The external water bath of the compost is used for heat preservation to reduce the heat loss inside the compost and ensure that the compost completely goes through the heating period, high temperature period, cooling period and decomposition period. The composting duration is 40 days.

[0032] Comparative Example 1

[0033] (1) Based on fresh weight, mix kitchen waste biogas residue, black soldier fly larvae excrement and sawdust in a ratio of 3:1:1 to obtain the initial composting substrate, denoted as CK.

[0034] (2) The initial composting substrate obtained in step (1) is subjected to aerobic composting. The aeration rate during composting is 0.4 L / min. The compost is turned over once every 2 days in the early stage and once every 5-7 days thereafter. The external water bath of the compost is used for heat preservation to reduce heat loss from the inside of the compost and ensure that the compost completely goes through the heating period, high temperature period, cooling period and decomposition period. The composting duration is 40 days.

[0035] Comparative Example 2

[0036] (1) Based on the fresh weight, the kitchen waste biogas residue, black soldier fly larvae excrement and sawdust are mixed evenly in a ratio of 3:1:1 to obtain the initial composting substrate. Lignocellulose degradation bacteria (accounting for 0.5% of the dry weight of the initial composting substrate) are added to the initial composting substrate and mixed evenly again to obtain material 3, denoted as BAC.

[0037] (2) The material 3 obtained in step (1) is subjected to aerobic composting. The aeration rate during composting is 0.4 L / min. The compost is turned over once every 2 days in the early stage and once every 5-7 days thereafter. The external water bath of the compost is used for heat preservation to reduce the heat loss inside the compost and ensure that the compost completely goes through the heating period, high temperature period, cooling period and decomposition period. The composting duration is 40 days.

[0038] Unless otherwise stated, the present invention uses the following detection method to determine substances in compost:

[0039] (1) Temperature: The temperature of the stack was measured at 9:00 and 21:00 every day, and the average value was taken to obtain the daily temperature measurement value.

[0040] (2) Three-dimensional fluorescence spectroscopy (humification index HIX, biogenic index BIX and fluorescence region integral): A certain mass of fresh compost sample was mixed with ultrapure water at a ratio of 1:10 (mass g: volume ml), shaken at 180 rpm for 24 h, centrifuged at 5000 rpm for 20 min, filtered through a 0.45 μm filter membrane, and measured using a fluorescence spectrometer.

[0041] (3) Ammonia (NH3) emissions: Ammonia was absorbed by 0.5 mol / L boric acid solution. A certain amount of boric acid absorption solution was taken at 9:00 and 21:00 every day and titrated with 0.01 mol / L sulfuric acid solution. The cumulative ammonia emissions during the composting process were calculated based on the amount of sulfuric acid solution consumed.

[0042] (4) Nitrous oxide (N2O) emissions: 100 ml of gas was collected from the reactor at 9:00 and 21:00 every day using a syringe containing a desiccant. After being sealed and left for 12 hours, the gas was injected into a gas bag and measured using gas chromatography.

[0043] It should be noted that the control group for Example 1 was Comparative Example 1, and the control group for Example 2 was Comparative Example 2. Results:

[0044] Temperatures in Examples 1 and 2 and Comparative Examples 1 and 2 were monitored throughout the process, and the results are shown in […]. Figure 1 After composting, the humification index (HIX) and biogenic index (BIX) of the compost products obtained from each treatment were measured, and fluorescence region integral analysis was performed on them. The results are shown in [Figure 1]. Figures 2-4 The cumulative emissions of NH3 and N2O at the end of composting were also measured, and the results are shown in [see attached table]. Figures 5-6 .

[0045] The high-temperature period (temperature ≥50℃) of the CK, BAC, LAC, and BL treatments lasted for 9 days, 10 days, 12 days, and 12 days, respectively. Among them, the number of days with temperature ≥55℃ reached 7 days, 8 days, 8 days, and 9 days, respectively. The highest temperatures reached during composting were 60.75℃, 61.55℃, 63.50℃, and 62.55℃, respectively. The maturation period of each treatment reached 8 days. This indicates that the addition of laccase can prolong the high-temperature period and increase the maximum temperature, thereby improving the safety of composting.

[0046] The humification indices of the compost products obtained from CK, BAC, LAC, and BL treatments were 4.10, 6.56, 6.64, and 6.47, respectively. Compared with CK, the LAC treatment increased the humification index by 61.95%, indicating that the addition of laccase can enhance the humification degree of compost products; the biogenic index of the compost products obtained from CK, BAC, LAC, and BL treatments was (…). Figure 3 The values ​​were 0.55, 0.60, 0.56, and 0.54, respectively. Compared with the control (CK), the LAC treatment increased the bioavailability index by 1.82%, indicating that the addition of laccase can enhance the bioavailability of compost products. Three-dimensional fluorescence-fluorescence region integration analysis divided the soluble organic matter of the compost products into five parts: region I represents tyrosine (a protein), region II represents tryptophan (a protein), region III represents fulvic acid substances, region IV represents soluble microbial metabolites, and region V represents humic acid substances. Based on the results of fluorescence region integration (…),… Figure 4 The dissolved organic matter was mainly composed of humic acids. Compared with CK and BAC, the addition of laccase increased the humic matter (regions III and V) by 2.30% and 0.98%, respectively, and the humic acid by 2.64% and 1.06%, respectively. According to the three-dimensional fluorescence correlation index, the addition of laccase can enhance the humification degree of the co-composting of kitchen waste biogas residue and black soldier fly frass.

[0047] In the CK, BAC, LAC, and BL treatments, the cumulative NH3 emissions ( Figure 5The concentrations of N2O were 2.34 g / kg DW (dry weight), 2.39 g / kg DW, 2.08 g / kg DW, and 2.13 g / kg DW, respectively. The addition of laccase significantly reduced NH3 emissions. Compared to the control (CK), the cumulative NH3 emissions in the LAC treatment decreased by 11.11%, and compared to the BAC treatment, the cumulative NH3 emissions in the BL treatment decreased by 10.88%. The cumulative N2O emissions (N2O) in the CK, BAC, LAC, and BL treatments were... Figure 6 The concentrations of nitrogen (N2O) in the composting groups were 7.45 mg / kg DW, 8.15 mg / kg DW, 14.22 mg / kg DW, and 9.63 mg / kg DW, respectively. Compared with the control (CK) and BAC (Bac), the addition of laccase increased N2O emissions in all groups. However, since the cumulative NH3 emissions were much higher than the cumulative N2O emissions in all composting groups, NH3 remains the main component of gaseous nitrogen loss during composting. In conclusion, the addition of laccase can enhance nitrogen fixation during the co-composting of kitchen waste sludge and black soldier fly frass.

[0048] The above embodiments are merely illustrative of the present invention. In practical applications, there is no need to limit oneself to them. Modifications in form and details can be made without departing from the concept of the present invention, and all of the above should fall within the protection scope of the present invention.

Claims

1. A method for humification and nitrogen fixation of anaerobic fermentation biogas residue of kitchen waste and black soldier fly larvae manure by co-composting with exogenous biochemical additives, characterized in that: The method is: ​ Step one: the kitchen waste biogas residue, black soldier fly feces are mixed uniformly according to the mass ratio of 3:1 to obtain the compost base material, the carbon-nitrogen ratio of the compost base material is controlled by adding a conditioner, the kitchen waste biogas residue, black soldier fly feces and the conditioner are mixed uniformly to obtain the initial compost substrate, the carbon-nitrogen ratio of the initial compost substrate is controlled to be 20-30:1, and the water content is 50%-70%; wood cellulose degrading enzyme or wood cellulose degrading enzyme coupled biochemical additive is added to the initial compost substrate, and the mixture is mixed again to obtain the compost material; the wood cellulose degrading enzyme is one or more of laccase, lignin peroxidase and cellulase, the enzyme activity is 500 U / g, and the dosage is 2% of the dry weight of the initial compost substrate; the biochemical additive is a wood cellulose degrading bacterial agent, which is composed of thermophilic starch bacillus, bacillus subtilis and bacillus licheniformis, and the effective viable bacterial count is greater than or equal to 5*10 8 CFU / g; the dosage of the wood cellulose degrading bacterial agent accounts for 0.5% of the dry weight of the initial compost substrate. Step two: aerobic composting of the compost material obtained in step one to ensure that the pile goes through the temperature rising period, high temperature period, temperature decreasing period and composting period.

2. The method according to claim 1, wherein the method is characterized in that: In step one, the conditioner is one or more of sawdust, straw, sawdust, vegetable stems, and landscaping waste.

3. The method for enhancing the anaerobic fermentation of kitchen waste and the composting and nitrogen fixation of biogas residue and black soldier fly larvae excrement with exogenous biochemical additives according to claim 1, characterized in that: In step two, the temperature change range of the aerobic composting temperature rising period is from the temperature of the compost material to 50 DEG C, the high temperature period is higher than 50 DEG C, the temperature decreasing period is from 50 DEG C to the temperature of the pile decreasing to room temperature, and the composting period is after entering the room temperature; wherein, the high temperature period requires more than 55 DEG C for 3 days or more than 50 DEG C for 5-7 days, the composting period needs to enter the room temperature for more than 7 days, and the above requirements are met to end the composting.

4. The method according to claim 1, wherein the method is characterized in that: In step two, the aerobic composting maintains the same aeration speed throughout the process, and the aeration speed is 0.1-0.4 L / min.

5. The method according to claim 1, wherein the method is characterized in that: In step two, the composting temperature rising period and high temperature period are turned over once every 2 days, and the temperature decreasing period and composting period are turned over once every 5-7 days.

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