Method for reinforcing co-compost humification and nitrogen fixation of kitchen waste anaerobic fermentation biogas residues and hermetia illucens fecula by using exogenous biochemical additive

Abstract

A method for reinforcing co-compost humification and nitrogen fixation of kitchen waste anaerobic fermentation biogas residues and hermetia illucens fecula by using an exogenous biochemical additive comprises the following steps: fully and uniformly mixing kitchen waste biogas residues and hermetia illucens fecula according to a mass ratio of 3: 1 to obtain a compost base material, adding a conditioner, uniformly mixing to obtain an initial compost substrate, and carrying out nitrogen fixation on the initial compost substrate; adding a lignocellulose degrading enzyme or a lignocellulose degrading enzyme coupling biochemical additive into the initial compost substrate, and uniformly mixing again to obtain a compost material; and carrying out aerobic composting on the fully and uniformly mixed compost material, ensuring whole aeration in the composting process, and carrying out complete heating period, high-temperature period, cooling period and decomposition period on the compost to obtain a compost product. The humification index of a compost product and the proportion of humus substances are both increased, the accumulated emission amount of ammonia gas in the composting process is remarkably reduced, and the synchronous resource utilization of the kitchen waste anaerobic fermentation biogas residues and the black soldier fly feces is enhanced.

Description

Technical Field

[0001] The invention belongs to the field of organic solid waste treatment, and specifically relates to a method for strengthening the humification and nitrogen fixation of anaerobic fermentation biogas residue of restaurant garbage and co-composting of black soldier fly feces by using exogenous biochemical additives. Background Art

[0002] The digestate produced after anaerobic fermentation of food waste (hereinafter referred to as "food waste digestate") is rich in organic matter and nutrients such as nitrogen, phosphorus, and potassium, and is considered to be an important resource for producing high-quality fertilizers. However, the hygienic indicators of food waste digestate are relatively poor. It not only emits a foul odor, but also breeds mosquitoes and flies and carries pathogenic bacteria. At present, aerobic composting is considered to be one of the most promising methods for achieving harmlessness and resource utilization in the treatment of food waste digestate. However, food waste digestate has problems such as high water content, low carbon-nitrogen ratio, and dense structure. Traditional food waste digestate composting often fails to meet good humification requirements. At present, the bioconversion technology of black soldier flies to organic waste such as food waste is widely used and promoted, but at the same time, a large amount of black soldier fly feces will be produced in this process. The feces contain high organic matter, trace elements, and a variety of amylases, lipases, and proteases, but there are also problems such as high salinity, odor, and high moisture content, which require further resource disposal.

[0003] The co-composting of food waste sludge and black soldier fly excrement can achieve a stable conversion of the two to a certain extent. The patent "A composting method of anaerobic digestion sludge of food waste organic slurry combined with black soldier fly excrement" (CN113105283A) co-composts food waste sludge and black soldier fly excrement, and the compost product meets the organic fertilizer standard (NY / T 525-2021), but the technology does not pay attention to nitrogen loss and enhanced humification. Food waste sludge contains a large amount of macromolecular organic matter, such as lignocellulose. Although the coordinated disposal technology of food waste sludge and black soldier fly excrement can partially convert lignocellulose into a variety of humus precursors, the conversion efficiency is not high, which in turn affects the efficiency of the co-composting process and the quality of the compost product. In addition, during the aerobic composting process, a large amount of nitrogen is lost in the form of gas (such as ammonia and nitrous oxide). This nitrogen loss will also affect the quality of the compost product and cause serious air pollution.

[0004] In theory, lignocellulose degrading enzymes can promote the effective degradation of lignocellulose. The patent "An active additive for promoting the composting of agricultural waste and its application" (CN105585346A) prepares a composite enzyme preparation with multiple organic matter degrading enzymes (including lignocellulose degrading enzymes), and uses it in the composting of agricultural waste (including vegetable leaves, straw, etc.), so that the germination rate of seeds is improved. However, there are no reports on its application in aerobic composting of food waste biogas residue. In response to the problem of nitrogen loss during composting, the commonly used method is to enhance nitrogen fixation by adding physicochemical additives such as biochar. However, it is difficult to further enhance the degradation of lignocellulose, improve composting efficiency and compost product quality by using only physicochemical enhancement methods. The cost of simultaneously enhancing composting humification and nitrogen loss reduction is high and the operation is cumbersome. At present, there are no reports on the addition of lignocellulose degrading enzymes to enhance the co-composting of food waste biogas residue and black soldier fly feces. The present invention aims to achieve simultaneous enhancement of humification and nitrogen fixation of aerobic composting of kitchen waste sludge-black soldier fly feces through a technical solution of biochemically enhanced lignocellulose conversion. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of high cost and complicated operation of strengthening composting humification and nitrogen loss reduction at present, and provide a method for strengthening the humification and nitrogen fixation of anaerobic fermentation sludge of restaurant garbage and co-composting of black soldier fly excrement by using exogenous biochemical additives. The method promotes the production of humus precursor substances in the co-composting process by adding lignocellulose degrading enzymes or lignocellulose degrading enzymes coupled with other biochemical additives to the restaurant garbage sludge-black soldier fly excrement co-composting system, thereby strengthening the humification and nitrogen fixation effects of the co-composting.

[0006] To achieve the above purpose, 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 residues of kitchen waste and co-composting of black soldier fly feces using exogenous biochemical additives, the method comprising:

[0008] Step 1: Fully mix the food waste sludge and the black soldier fly feces in a mass ratio of 3:1 to obtain a compost base material, control the carbon-nitrogen ratio of the compost base material by adding a conditioning agent, and evenly mix the food waste sludge, the black soldier fly feces and the conditioning agent to obtain an initial compost matrix, and control the carbon-nitrogen ratio of the initial compost matrix to be 20-30:1 and the moisture content to be 50%-70%; add lignocellulose degrading enzyme or lignocellulose degrading enzyme coupled biochemical additive to the initial compost matrix, and mix again to obtain a compost material;

[0009] Step 2: aerobic composting of the compost obtained in step 1 to ensure that the compost body has completely passed through the heating period, high temperature period, cooling period and maturity period; combined with three-dimensional fluorescence spectroscopy technology, the humification index of the compost body at the end of composting is detected and analyzed to determine the humification effect of the compost product; ammonia (NH 3 ) and nitrous oxide (N 2 The nitrogen fixation effect of composting was determined based on the cumulative emission of gaseous nitrogen during the composting process.

[0010] Furthermore, in step one, the conditioning agent is one or more of wood chips, straw, sawdust, vegetable stems, and landscaping waste.

[0011] Furthermore, in step 1, the lignocellulose 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 initial compost substrate dry weight.

[0012] Furthermore, in step 1, the biochemical additive is a lignocellulose degrading bacterial agent. There is no requirement for the amount of the biochemical additive added.

[0013] Furthermore, in step 2, the temperature variation range of the aerobic composting heating period is from the temperature of the compost material to 50°C, the high temperature period is the temperature above 50°C, the cooling period is from 50°C to the pile body dropping to room temperature, and the maturity period is after entering room temperature; wherein, the high temperature period requires to be above 55°C for 3 days or above 50°C for 5-7 days, and the maturity period needs to be continued for 7 days or more after entering room temperature. The composting can be terminated only when the above requirements are met.

[0014] Furthermore, in step 2, the aeration rate is maintained at the same level throughout the aerobic composting process, and the aeration rate is 0.1-0.4 L / min.

[0015] Furthermore, in step 2, the compost is turned over once every 2 days during the temperature rise period and the high temperature period, and once every 5-7 days during the temperature drop period and the maturity period.

[0016] The beneficial effects of the present invention over the prior art are as follows: the present invention provides a simple and effective method for enhancing the co-composting effect of food waste sludge and black soldier fly feces, by adding lignocellulose degrading enzymes or coupling lignocellulose degrading enzymes with other biochemical additives, the humification and nitrogen fixation of the co-composting are simultaneously promoted, and the synchronous resource utilization of food waste sludge and black soldier fly feces is enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1The temperature changes in different composting treatments: CK: no exogenous additives, BAC: inoculated with 0.5% lignocellulose degrading bacteria, LAC: added with 2% laccase, BL: added with 0.5% lignocellulose degrading bacteria and 2% laccase at the same time;

[0018] Figure 2 is the humification index of compost products with different treatments. CK, BAC, LAC and BL are Figure 1 ;

[0019] Figure 3 is the biogenic index of compost products treated with different methods. CK, BAC, LAC and BL are the same. Figure 1 ;

[0020] Figure 4 is the fluorescence area integral ratio of the compost products under different treatments, CK, BAC, LAC and BL Figure 1 ;

[0021] Figure 5 NH in different composting processes 3 The cumulative emissions of CK, BAC, LAC and BL are the same Figure 1 ;

[0022] Figure 6 N in different composting processes 2 Cumulative emissions of O, CK, BAC, LAC and BL Figure 1 . DETAILED DESCRIPTION

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

[0024] In the following examples and comparative examples, the food waste sludge used in the aerobic composting test was taken from a food waste treatment plant in Harbin, and 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. The black soldier fly excrement was derived from the excrement discharged by the black soldier fly larvae fed by the food waste solid residue, and 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 conditioning agent used for aerobic composting was sawdust, which was taken from a wood processing plant in Harbin, and its moisture content, total carbon, and total nitrogen were 5.53%, 45.74%, and 0.44%, respectively. The lignocellulose degradation agent was purchased from a biotechnology company in Weihai, Shandong. The agent was a composite agent mainly composed of thermophilic amyloliquefaciens, Bacillus subtilis, Bacillus licheniformis, etc., and its effective viable count was ≥5×10 8CFU / g. Laccase was purchased from a chemical product company in Henan Province, and its enzyme activity was 500U / g. The following examples were carried out in the laboratory, and three-dimensional fluorescence analysis was performed on the compost products with different treatments. The humification index HIX, the biogenic index BIX and the proportion of each fluorescence area were detected and analyzed. At the same time, the NH 3 and N 2 Cumulative emissions of O.

[0025] The sawdust used in the following examples and comparative examples and the laccase used in the examples are representative, specifically: (1) sawdust has a high carbon-nitrogen ratio, a wide range of applications, and is easily available, making it an easily accessible and efficient compost conditioner; (2) lignin in lignocellulose is difficult to degrade, and lignin acts as a supporting skeleton 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 of lignocellulose-degrading enzymes, and laccases have a wide range of substrate adaptability and environmental tolerance. Compared with other lignin-degrading enzymes, laccases in the composting system can more directly reflect the role of lignocellulose-degrading enzymes in the composting process.

[0026] Example 1

[0027] (1) Based on the fresh weight, food waste biogas residue, black soldier fly feces and sawdust were mixed at a ratio of 3:1:1 to obtain an initial compost matrix. Laccase (accounting for 2% of the dry weight of the initial compost matrix) was added to the initial compost matrix, and the mixture was fully mixed again to obtain material 1, which was recorded as LAC.

[0028] (2) aerobic composting of the material 1 obtained in step (1), with an aeration rate of 0.4 L / min during the composting process, turning the pile once every 2 days in the early stage of composting, and turning the pile once every 5-7 days thereafter. The pile body is kept warm by water bathing to reduce the heat loss inside the pile body, ensuring that the pile body completely passes through the heating period, high temperature period, cooling period and decomposition period, and the composting duration is 40 days.

[0029] Example 2

[0030] (1) Based on the fresh weight, food waste sludge, black soldier fly feces and sawdust were mixed at a ratio of 3:1:1 to obtain an initial compost matrix. A lignocellulose-degrading bacterial agent (accounting for 0.5% of the dry weight of the initial compost matrix) and laccase (accounting for 2% of the dry weight of the initial compost matrix) were added to the initial compost matrix, and the mixture was mixed again to obtain material 2, which was recorded as BL.

[0031] (2) The material 2 obtained in step (1) is subjected to aerobic composting, and the aeration rate during the composting process is 0.4 L / min. The compost is turned once every 2 days in the early stage of composting, and once every 5-7 days thereafter. The external part of the compost body is kept warm by water bath to reduce the heat loss inside the compost body, and ensure that the compost body completely passes 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 the fresh weight, kitchen waste sludge, black soldier fly feces and sawdust were mixed evenly in a ratio of 3:1:1 to obtain the initial composting matrix, which was recorded as CK.

[0034] (2) aerobic composting is performed on the initial compost substrate obtained in step (1), and the aeration rate during the composting process is 0.4 L / min. The compost is turned once every 2 days in the early stage of composting, and once every 5-7 days thereafter. The external part of the compost body is kept warm by water bathing to reduce the heat loss inside the compost body, and to ensure that the compost body completely passes through the heating period, high temperature period, cooling period and decomposition period. The composting duration is 40 days.

[0035] Comparative Example 2

[0036] (1) According to the fresh weight, food waste sludge, black soldier fly feces and sawdust were mixed in a ratio of 3:1:1 to obtain an initial compost matrix. A lignocellulose-degrading bacterial agent (accounting for 0.5% of the dry weight of the initial compost matrix) was added to the initial compost matrix, and the mixture was mixed again to obtain material 3, which was recorded as BAC.

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

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

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

[0040] (2) Three-dimensional fluorescence spectrum (humification index HIX, biogenic index BIX and fluorescence area 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 (NH 3) Emissions: Use 0.5 mol / L boric acid solution to absorb ammonia. Take a certain amount of boric acid absorption solution at 9:00 and 21:00 every day, and titrate it with 0.01 mol / L sulfuric acid solution. Calculate the cumulative ammonia emissions during the composting process based on the consumption of sulfuric acid solution;

[0042] (4) Nitrous oxide (N 2 O) Emissions: 100 ml of gas in the reactor was collected using a syringe filled with a desiccant at 9:00 and 21:00 every day, sealed for 12 hours, and then injected into an air bag for determination using gas chromatography.

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

[0044] The temperature of Examples 1 and 2 and Comparative Examples 1 and 2 was monitored throughout the process. Figure 1 After the composting was completed, the humification index HIX and biogenic index BIX of the compost products obtained from each treatment were detected, and the fluorescence area integral analysis was performed. The results are shown in Figure 2-Figure 4 ; At the same time, the NH 3 and N 2 O cumulative emissions, see Figure 5-Figure 6 .

[0045] The high temperature period (temperature ≥ 50℃) of CK, BAC, LAC and BL treatments lasted for 9d, 10d, 12d and 12d, respectively. The number of days with temperature ≥ 55℃ reached 7d, 8d, 8d and 9d, respectively. The highest temperatures reached during the composting process were 60.75℃, 61.55℃, 63.50℃ and 62.55℃, respectively. The maturity period of each treatment reached 8d, which shows that the addition of laccase can prolong the high temperature period, increase the maximum temperature, and improve the safety of composting.

[0046] The humification indexes of the compost products obtained by CK, BAC, LAC, and BL treatments were 4.10, 6.56, 6.64, and 6.47, respectively. Compared with CK, the humification index of LAC treatment increased by 61.95%, indicating that the addition of laccase can enhance the humification degree of the compost products; the biogenic index of the compost products obtained by CK, BAC, LAC, and BL treatments was ( Figure 3) were 0.55, 0.60, 0.56, and 0.54, respectively. Compared with CK, LAC treatment increased the biosource index by 1.82%, indicating that the addition of laccase can enhance the bioavailability of compost products. Through three-dimensional fluorescence-fluorescence regional integration analysis, the dissolved organic matter of the compost product was divided into five parts, of which region I represents protein-based tyrosine, region II represents protein-based tryptophan, region III represents fulvic acid substances, region IV represents soluble microbial metabolites, and region V represents humic acid substances. According to the results of fluorescence regional integration ( Figure 4 ), the components of dissolved organic matter are mainly humic acid substances, and compared with CK and BAC, the addition of laccase can increase the humic substances (area III + area V) by 2.30% and 0.98%, respectively, and the humic acid substances by 2.64% and 1.06%, respectively. According to the three-dimensional fluorescence related indicators, the addition of laccase can enhance the humification degree of food waste biogas residue-black soldier fly feces co-composting.

[0047] In the CK, BAC, LAC, and BL treatments, NH 3 Cumulative emissions ( Figure 5 ) 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 had an effect on the 3 The emission reduction effect was obvious. Compared with CK, in the LAC treatment, NH 3 The cumulative emissions decreased by 11.11% compared with BAC. In the BL treatment, NH 3 The cumulative emission decreased by 10.88%. In the CK, BAC, LAC, and BL treatments, N 2 Cumulative emissions of O Figure 6 ) were 7.45mg / kg DW, 8.15mg / kgDW, 14.22mg / kg DW, and 9.63mg / kg DW, respectively. Compared with CK and BAC, the addition of laccase increased N 2 O emissions increased. However, due to the NH 3 The cumulative emissions are much higher than N 2 Cumulative emissions of O, NH 3 It is still the main lost component of gaseous nitrogen in composting. In summary, the addition of laccase can enhance the fixation of nitrogen during the co-composting of food waste biogas residue and black soldier fly feces.

[0048] The above embodiments are only for illustration of the present invention and are not limited thereto in practical applications. Modifications may be made in form and details without departing from the concept of the present invention, and all of the above shall fall within the protection scope of the present invention.

Claims

1. A method for enhancing the humification and nitrogen fixation of anaerobic fermentation residues of kitchen waste and black soldier fly feces by using exogenous biochemical additives, characterized in that: The method is: Step 1: Fully mix the food waste sludge and the black soldier fly feces in a mass ratio of 3:1 to obtain a compost base material, control the carbon-nitrogen ratio of the compost base material by adding a conditioning agent, and evenly mix the food waste sludge, the black soldier fly feces and the conditioning agent to obtain an initial compost matrix, and control the carbon-nitrogen ratio of the initial compost matrix to be 20-30:1 and the moisture content to be 50%-70%; add lignocellulose degrading enzyme or lignocellulose degrading enzyme coupled biochemical additive to the initial compost matrix, and mix again to obtain a compost material; Step 2: aerobic composting is performed on the compost material obtained in step 1 to ensure that the compost body completely passes through the temperature rise period, high temperature period, temperature drop period and maturity period.

2. The method of enhancing the humification and nitrogen fixation of anaerobic fermentation residues of kitchen waste and black soldier fly feces by using exogenous biochemical additives according to claim 1, characterized in that: In step 1, the conditioning agent is one or more of wood chips, straw, sawdust, vegetable stems, and landscaping waste.

3. The method of enhancing the humification and nitrogen fixation of anaerobic fermentation residues of kitchen waste and black soldier fly feces by using exogenous biochemical additives according to claim 1, characterized in that: In step 1, the lignocellulose 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 composting substrate.

4. The method of enhancing the humification and nitrogen fixation of anaerobic fermentation residues of kitchen waste and black soldier fly feces by using exogenous biochemical additives according to claim 1, characterized in that: In step 1, the biochemical additive is a lignocellulose degrading bacterial agent.

5. The method of enhancing the humification and nitrogen fixation of anaerobic fermentation residues of kitchen waste and black soldier fly feces by using exogenous biochemical additives according to claim 1, characterized in that: In step 2, the temperature variation range of the aerobic composting heating period is from the temperature of the compost material to 50°C, the high temperature period is when the temperature is higher than 50°C, the cooling period is from 50°C to when the pile body drops to room temperature, and the mature period is after entering room temperature; among them, the high temperature period requires to be above 55°C for 3 days or above 50°C for 5-7 days, and the mature period needs to be continued for 7 days or more after entering room temperature. The composting can be terminated only when the above requirements are met.

6. The method of enhancing the humification and nitrogen fixation of anaerobic fermentation residues of kitchen waste and black soldier fly feces by using exogenous biochemical additives according to claim 1, characterized in that: In step 2, the aeration rate is maintained at the same level throughout the aerobic composting process, which is 0.1-0.4 L / min.

7. The method of enhancing the humification and nitrogen fixation of anaerobic fermentation residues of kitchen waste and black soldier fly feces by using exogenous biochemical additives according to claim 1, characterized in that: In step 2, the compost is turned over every 2 days during the temperature rise period and the high temperature period, and every 5-7 days during the temperature drop period and the maturity period.

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