Analysis method and system for preparing biogas and co-producing biogas manure through anaerobic fermentation of mixed raw materials

Abstract

The invention discloses an analysis method and system for preparing biogas and co-producing biogas manure by anaerobic fermentation of mixed raw materials. According to the method disclosed by the invention, the methane cumulative yield fitting and decision-making model is established by utilizing the Modified Gompertz kinetic model, so that fermentation gas production data can be quantified and can be predicted; meanwhile, systematic evaluation is conducted on organic matter, NPK, ammonia nitrogen, heavy metal, resistance genes and the like, a biogas manure evaluation index system is established, and the agricultural potential and environmental safety of biogas manure are analyzed; furthermore, a set of analysis method and system for a mixed anaerobic fermentation mode is formed by combining a methane accumulation yield fitting and decision-making model and a biogas manure evaluation index system, and the optimal proportion of pig manure to cow manure can be screened out, so that the biogas and the biogas manure with agricultural potential and environmental safety are efficiently prepared, and the method is suitable for industrial production. And scientific reference is provided for energy and resource utilization of farm wastes.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of agricultural waste treatment and resource utilization, and relates to an analysis method and system for mixed raw material anaerobic fermentation for biogas and biogas fertilizer co-production. BACKGROUND

[0002] With the rapid development of livestock and poultry breeding industry, a large amount of livestock and poultry manure discharge has caused significant pressure on the environment. Anaerobic fermentation is an efficient and environmentally friendly manure treatment technology that can simultaneously achieve energy recovery and organic fertilizer preparation. Currently, the fermentation efficiency of a single raw material is limited, and the biogas yield and fertilizer efficiency are unstable. Studies have shown that mixing different types of manure can improve substrate degradation efficiency and enhance system stability. Cow manure is rich in cellulose, which helps to release carbon sources slowly; pig manure is rich in nitrogen, which can enhance microbial activity, but the total solid mixing ratio of the two has not been systematically optimized for anaerobic fermentation for biogas and biogas fertilizer co-production.

[0003] Currently, the environmental protection problem of livestock and poultry farms is increasingly prominent. Harmless treatment of manure generated in livestock and poultry breeding, and resource utilization of the treated products (such as returning to the field), is an effective way to reduce pollution from livestock and poultry manure. Biogas fertilizer, as an organic fertilizer rich in nutrients, can promote the growth and reproduction of microorganisms, thereby improving soil structure and increasing soil fertility, providing more adequate nutrients for crop growth.

[0004] However, there is currently no scientific evaluation index and quantitative model for efficiently producing biogas and biogas fertilizer with agricultural potential and environmental safety through anaerobic fermentation. Therefore, there is an urgent need for an analysis method and system for mixed raw material anaerobic fermentation for biogas and biogas fertilizer co-production. SUMMARY

[0005] The present application aims to solve the technical bottlenecks of current anaerobic fermentation process, such as large fluctuations in gas production performance, poor system stability, and uneven utilization of biogas fertilizer efficiency, and provides an analysis method and system for mixed raw material anaerobic fermentation for biogas and biogas fertilizer co-production. The present application uses the Modified Gompertz kinetic model to establish a methane cumulative yield fitting and decision-making model, which enables the fermentation gas production data to be quantified and predictable. At the same time, through systematic evaluation of organic matter, NPK, ammonia nitrogen, heavy metals, and resistance genes, an evaluation index system for biogas fertilizer is established to analyze the agricultural potential and environmental safety of biogas fertilizer. Further, the present application combines the methane cumulative yield fitting and decision-making model and the biogas fertilizer evaluation index system to form a set of analysis method and system for mixed fermentation mode, which can select the optimal ratio of pig manure and cow manure to produce biogas with the maximum final methane production potential, maximum methane production rate, and shortest lag phase, as well as biogas fertilizer with agricultural potential and environmental safety, achieving the synergistic improvement of efficient biogas production and fertilizer resource recovery, and providing scientific reference for energy and resource utilization of waste from farms.

[0006] The object of the present application can be achieved by the following scheme: In a first aspect, the present application provides an analysis method for biogas and biogas slurry produced by anaerobic fermentation of mixed raw materials, comprising the following steps: S1, collecting pig manure and cow manure as fermentation raw materials; S2, after removing impurities from the anaerobic fermentation inoculum, performing activation culture treatment to obtain a methanogenic inoculum; S3, mixing the pig manure and cow manure in the fermentation raw materials of step S1 at different proportions, respectively adding the methanogenic inoculum of step S2 for anaerobic fermentation, and collecting fermentation data; S4, fitting the biogas fermentation data in the fermentation data of step S3 to the Modified Gompertz kinetic model to obtain kinetic parameters; S5, analyzing the biogas slurry fermentation data in the fermentation data of step S3 and the kinetic parameters in step S4, and determining the optimal proportion of pig manure and cow manure after comprehensive evaluation.

[0007] As an embodiment of the present application, in step S1, the pig manure is collected from a farm and impurities are removed; the cow manure is collected from a farm and impurities are removed; the impurities include at least one of stones, metals and feathers.

[0008] As an embodiment of the present application, in step S2, the anaerobic fermentation inoculum includes anaerobic activated sludge.

[0009] As an embodiment of the present application, in step S2, the activation culture treatment includes: adding nutrients to the anaerobic fermentation inoculum, and after the methane content in the produced biogas exceeds 50%, stopping adding nutrients until no biogas is produced (within seven days), and obtaining the product. The main purpose of the activation culture in the present application is to activate the activity of methanogenic bacteria, improve the inoculum start-up efficiency and gas production capacity; the microorganisms in the inoculum without activation treatment may be in a dormant or inhibited state, with weak metabolic capacity and delayed methanogenesis.

[0010] Further, the nutrients include one or more of glucose, acetic acid, sucrose and soluble starch. Preferably, the nutrients are glucose. Glucose is one of the commonly used carbon sources, which serves to provide easily degradable substrates for microorganisms to activate metabolism, and can be used as nutrients for activating the methanogenic inoculum in the present application.

[0011] As an embodiment of the present application, in step S3, the solid content of the fermentation raw material in the mixed system of fermentation raw material and methanogenic inoculum is 4%-8%; the mass ratio of the methanogenic inoculum to the fermentation raw material is 4-6:1.

[0012] As an embodiment of the present application, in step S3, the temperature of the anaerobic fermentation is 35±2℃, and the period is 45 days. The methanogenic inoculum is mixed with the fermentation raw material uniformly, and then loaded into a closed fermentation reactor, and the mesophilic anaerobic fermentation is carried out at 35±2℃, and the period is 45 days, and the daily gas production and the methane content are measured, and the cumulative methane production and the yield are calculated.

[0013] As an embodiment of the present application, in step S3, the fermentation data includes biogas fermentation data and biogas fertilizer fermentation data, wherein the biogas fermentation data includes the cumulative methane production M(t) and the test time t, and the biogas fertilizer fermentation data includes the organic matter index, the NPK index, the ammonia nitrogen index, the heavy metal index and the resistance gene index.

[0014] As an embodiment of the present application, in step S4, the kinetic parameters include the final methanogenic potential M max , the maximum methanogenic rate R max , and the lag phase λ, and the fitting includes a nonlinear regression fitting. The calculation formula of the kinetic parameters in the Modified Gompertz kinetic model is as follows:

[0015] Wherein, M(t) is the cumulative methane production at t time, mL; M max is the final methanogenic potential, mL; R max is the maximum methanogenic rate, mL / d; λ is the lag phase, d; t is the test time, d; and e is a constant 2.7183.

[0016] The present application can describe and predict the law of the change of the cumulative methane production with time (i.e. the gas production kinetic curve) in the anaerobic fermentation process through the Modified Gompertz kinetic model, and a series of time points t and the corresponding cumulative methane production M(t) are actually measured through the anaerobic fermentation experiment. Then, the (t, M(t)) data points measured through the experiment are fitted (Fit) to the Modified Gompertz model formula through a mathematical method (such as a nonlinear regression fitting). Through the fitting, the computer algorithm will automatically adjust the values of the three key unknown parameters (M max , R max , λ) in the formula, so that the fitting effect of the Gompertz curve is the best. After the fitting is completed, the three kinetic parameters (the final methanogenic potential M max , the maximum methanogenic rate R max , and the lag phase λ) that can best reflect the experimental results are obtained.

[0017] The results of the present application show that when the ratio of cow manure and pig manure is mixed according to 20%:80% for fermentation, the cumulative methane production and the maximum methane production rate are optimal, and the pH stability, alkalinity buffering capacity and volatile fatty acid regulation capacity are good.

[0018] In a second aspect, the present application provides an analysis system for mixed raw material anaerobic fermentation to produce biogas and biogas fertilizer, comprising: Module M1, collecting pig manure and cow manure as fermentation raw materials; Module M2, after removing impurities from the anaerobic fermentation inoculum, performing activation culture treatment to obtain a methanogenic inoculum; Module M3, mixing pig manure and cow manure in the fermentation raw materials of module M1 according to different proportions, respectively adding the methanogenic inoculum of module M2 for anaerobic fermentation, and collecting fermentation data; Module M4, fitting the biogas fermentation data in the fermentation data of module M3 to the Modified Gompertz kinetic model to obtain kinetic parameters; Module M5, analyzing the biogas fertilizer fermentation data in the fermentation data of module M3 and the kinetic parameters in module M4, and determining the optimal proportion of pig manure and cow manure after comprehensive evaluation.

[0019] Compared with the prior art, the present application has the following beneficial effects: 1. The present application uses the Modified Gompertz kinetic model to establish a methane cumulative production fitting and decision-making model, so that the fermentation gas production data can be quantified and predictable; at the same time, by systematically evaluating organic matter, NPK, ammonia nitrogen, heavy metals, and resistance genes, an evaluation index system of biogas fertilizer is established to analyze the agricultural potential and environmental safety of biogas fertilizer; further, the present application combines the methane cumulative production fitting and decision-making model and the biogas fertilizer evaluation index system to form an analysis method and system for mixed fermentation mode, which can screen out the optimal proportion of pig manure and cow manure, thereby preparing biogas with the largest final methanogenic potential and maximum methanogenic rate and the shortest lag phase, and biogas fertilizer with agricultural potential and environmental safety, realizing the synergistic improvement of efficient biogas production and fertilizer resource recovery, and providing scientific reference for energy and resource utilization of breeding waste.

[0020] 2, The application based on the formed analysis method and system, the influence mechanism of its to gas production performance and biogas fertilizer efficiency is clear, the substrate is provided quickly by pig manure, the slow release and buffer function are provided by cow manure, the metabolic stability and long-term operation capacity of the fermentation system can be improved by the cooperation of the two, the methane production potential and methane production rate of the mixed raw material anaerobic fermentation are significantly improved, the cumulative methane production is significantly improved, and the lag phase is effectively shortened compared with the mixed raw material anaerobic fermentation under other ratios; Meanwhile, the inoculum activation mechanism is designed to improve the stability of the inoculated bacteria. BRIEF DESCRIPTION OF DRAWINGS

[0021] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the following drawings: Figure 1 The process flow chart of the mixed raw material anaerobic fermentation for preparing biogas and biogas fertilizer and the method of biogas fertilizer of the application; Figure 2 The cumulative methane production and Modified Gompertz model fitting curve graph of the evaluation of the mixed raw material anaerobic fermentation for preparing biogas and biogas fertilizer and the method of biogas fertilizer of the embodiment of the application. DETAILED DESCRIPTION

[0022] The application will be described in detail below with reference to the drawings and specific embodiments. The following examples are implemented on the premise of the technical scheme of the application, and detailed implementation modes and specific operation processes are provided, which will help those skilled in the art to further understand the application. It should be pointed out that the protection scope of the application is not limited to the following examples, and several adjustments and improvements made on the premise of the concept of the application all belong to the protection scope of the application.

[0023] Anaerobic fermentation inoculum: a material rich in biogas microorganisms added to a biogas tank to accelerate the start-up speed of biogas fermentation and improve the biogas production of the biogas tank. The anaerobic fermentation inoculum is an anaerobic active sludge composed of anaerobic digestion microorganisms, suspended substances and colloidal substances.

[0024] The application provides an analysis method for preparing biogas and biogas fertilizer by mixed raw material anaerobic fermentation, comprising the following steps: S1, collecting fermentation raw materials, wherein the fermentation raw materials comprise pig manure and cow manure; Preferably, the fermentation raw materials are pig manure and cow manure which are representative of a wide range of agricultural organic waste, and are mixed as the fermentation raw materials used in the experiment; In order to achieve better fermentation effect, the above-mentioned fermentation raw materials are pretreated and then added; The pig manure is pretreated, i.e., after picking out stones, metals, feathers and other impurities, it is stored in a refrigerator at -20°C; The cow manure is pretreated, i.e., after picking out stones, metals, feathers and other impurities, it is stored in a refrigerator at -20°C; S2, preparing an anaerobic fermentation inoculum; Preferably, after removing impurities from the anaerobic fermentation inoculum (anaerobic activated sludge), an activation culture treatment is performed, and after the methane content in the gas produced by the inoculum exceeds a set value, the addition of nutrients is stopped, and the culture is performed until no biogas is produced, to obtain a methanogenic inoculum; Specifically, after removing impurities from the inoculum, an activation culture treatment is performed, and after the methane content in the gas produced by the inoculum exceeds 50%, the addition of nutrients such as glucose is stopped until no biogas is produced within seven days; S3, mixing the pig manure and the cow manure collected in S1 in different proportions, adding the inoculum in S2 to perform a mixed anaerobic fermentation experiment, the temperature of the anaerobic fermentation is 35±2°C, the period is 45 days, and fermentation data are collected; Preferably, the fixed carbon-nitrogen ratio is in the range of 18-20 suitable for anaerobic fermentation, the fermentation substrate is fixed at 4%-8% in terms of total solid content (TS), and the mass ratio of the methanogenic inoculum to the fermentation raw material is 4~6:1. According to the total solid content of the fermentation raw material, the total solid content inoculation ratio of the cow manure to the pig manure is considered to be 20%:80% (Run 1), 40%:60% (Run 2), 60%:40% (Run 3) and 80%:20% (Run 4) for dosing, to perform a mixed anaerobic fermentation of cow manure and pig manure to produce biogas and co-produce biogas fertilizer; The process of producing biogas and co-producing biogas fertilizer by mixed raw material anaerobic fermentation and the biogas fertilizer is as shown in Figure 1 ; Preferably, the fermentation data include biogas fermentation data and biogas fertilizer fermentation data; wherein the biogas fermentation data include methane cumulative yield M(t) and test time t; the biogas fertilizer fermentation data include organic matter indicators, NPK indicators, ammonia nitrogen indicators, heavy metal indicators and resistance gene indicators.

[0025] S4, fitting the biogas fermentation data in the fermentation data in step S3 to a Modified Gompertz kinetics model to obtain kinetic parameters; Preferably, the kinetic parameters include final methane production potential M max , maximum methane production rate R max , and lag phase λ; the fitting includes nonlinear regression fitting; The calculation formula of the methane cumulative yield indicator in the Modified Gompertz kinetics model is as follows:

[0026] Wherein, M(t) is the cumulative methane production at t time, mL; M max is the ultimate methane potential, mL; R max is the maximum methane production rate, mL / d; λ is the lag phase, d; t is the test time, d; e is a constant 2.7183.

[0027] S5, analyzing the biogas manure fermentation data in the fermentation data of step S3 and the kinetic parameters in step S4, and determining the optimal proportion of pig manure and cow manure after comprehensive evaluation; Preferably, the biogas manure fermentation data includes organic matter indicators, NPK indicators, ammonia nitrogen indicators, heavy metal indicators, and resistance gene indicators.

[0028] The application also provides an analysis system for mixed raw material anaerobic fermentation to produce biogas and biogas manure, comprising: Module M1, collecting pig manure and cow manure as fermentation raw materials; Module M2, after removing impurities from the anaerobic fermentation inoculum, performing activation culture treatment to obtain a methane-producing inoculum; Module M3, mixing the pig manure and cow manure in the fermentation raw materials of module M1 in different proportions, respectively adding the methane-producing inoculum of module M2 for anaerobic fermentation, and collecting fermentation data; Module M4, fitting the biogas fermentation data in the fermentation data of module M3 to a Modified Gompertz kinetic model to obtain kinetic parameters; Module M5, analyzing the biogas manure fermentation data in the fermentation data of module M3 and the kinetic parameters in module M4, and determining the optimal proportion of pig manure and cow manure after comprehensive evaluation.

[0029] Embodiment First step: fermentation raw material collection and pretreatment: 1. The pig manure was collected from a farm in Inner Mongolia Autonomous Region, and after removing impurities such as stones, metals, and feathers, it was stored in a -20℃ refrigerator.

[0030] 2. The cow manure was collected from a farm in Inner Mongolia Autonomous Region, and after removing impurities such as stones, metals, and feathers, it was stored in a -20℃ refrigerator.

[0031] 3. The anaerobic fermentation inoculum was taken from a farm in Shanghai (the anaerobic fermentation inoculum in this embodiment was taken from a biogas engineering project of Shanghai Sennong Environmental Protection Technology Co., Ltd. in Pudong New Area, Shanghai, which used cow manure as raw material), and after removing impurities, it was subjected to activation culture treatment. After the methane content in the gas produced by the inoculum exceeded 50%, the nutrients (glucose) were stopped, and no biogas was produced within seven days. The total solid content and volatile solid content of the inoculum based on the wet sample were both 5.75%. The inoculum after treatment was inoculated into a fermentation bottle. The fermentation substrate was directly inoculated. The physicochemical properties of the fermentation raw materials and the inoculum are shown in Table 1.

[0032] Table 1 Basic characteristics of fermentation raw materials and inoculum

[0033] Second step: batch anaerobic fermentation for hydrogen production: 1. Anaerobic fermentation was carried out in rubber plug-sealed conical flasks with a single flask effective volume of 200 mL. The total solid content (TS) of fermentation substrate was fixed at 6%, and the total solid content inoculation ratio of cow manure and pig manure was 20%:80% (Run 1), 40%:60% (Run 2), 60%:40% (Run 3), and 80%:20% (Run 4), respectively. The C / N ratio of the fermentation substrate was controlled within the range of 18-20, and the total solid mass ratio of methanogenic inoculum to fermentation raw material was 4.8:1.

[0034] 2. After the conical flask was filled with nitrogen for 5 min to expel air, it was sealed and placed in a constant-temperature water bath shaker for cultivation at 35°C.

[0035] Third step: batch anaerobic fermentation for methane production process: 1. Anaerobic fermentation was carried out in rubber plug-sealed conical flasks. After the conical flask was filled with nitrogen for 5 min to expel air, it was sealed and placed in a constant-temperature water bath shaker for cultivation at 35°C.

[0036] At the same time, for comparison of mixed raw material ratio, the total solid content inoculation ratio of cow manure and pig manure was 20%:80% (Run 1), 40%:60% (Run 2), 60%:40% (Run 3), and 80%:20% (Run 4), respectively, for anaerobic fermentation treatment. Each treatment was set up in triplicate. At least 3 consecutive days when the daily gas production was less than 1% of the cumulative gas production, it was considered that the gas production period was over, and the fermentation data was measured.

[0037] The gas production results were fitted to the cumulative methane production process using the modified Gompertz equation:

[0038] M(t) is the cumulative methane production at time t, mL; M max is the final methane production potential, mL; R max is the maximum methane production rate, mL / d; λ is the lag phase, d; t is the test time, d; e is the constant 2.7183.

[0039] Implementation results The mixed anaerobic fermentation of cow manure and pig manure was carried out by the above-mentioned implementation method, and the experimental results are shown in Table 1, wherein: Figure 2 Run 1 represents TS cow manure:TS pig manure = 20%:80%;​ Run 2 represents TS cow manure: TS pig manure = 40%:60%; Run 3 represents TS cow manure: TS pig manure = 60%:40%; Run 4 represents TS cow manure: TS pig manure = 80%:20%; From the results Figure 2 It can be seen that the mixed fermentation method of the embodiment of the application greatly improves the methane production capacity of the mixed raw material anaerobic fermentation. The fitting results of the cumulative methane production of each experimental group using the modified Gompertz equation are shown in Table 2.

[0040] Table 2 Fitting parameters of modified Gompertz model for cumulative methane production

[0041] From the experimental results in Table 2, it can be seen that under different proportions of mixed raw materials, the experimental results are as follows: the lag phase (λ) is prolonged with the increase of the proportion of cow manure (Run 1 to Run 4: 4.06 d→7.20 d), the maximum methane production rate (R m ) decreases from 159.61 mL / d of Run 1 to 104.12 mL / d of Run 4 (decrease of 34.8%), and the final methane production potential (M max ) decreases from 3509.07 mL of Run 1 to 953.89 of Run 4 (decrease of 72.8%). This trend shows that a high proportion of pig manure significantly improves the metabolic rate of methanogens by providing easily directly utilized substrates (such as acetic acid, H2 / CO2); while the slowly released degradation products in cow manure limit the peak of methanogenic rate. In summary, the final methane production potential and the maximum methane production rate of Run 1 are the largest, and the lag phase is the shortest, which is suitable as the parameters for long-term anaerobic fermentation.

[0042] From the VS of pig manure (experimentally measured as 12.46%) and the VS of cow manure (experimentally measured as 39.24%), the volatile solid content in the fermentation substrate of Run 1, Run 2, Run 3 and Run 4 can be calculated, which are 10.34 g VS, 10.35 g VS, 10.37 g VS and 10.38 g VS, respectively. The maximum methane production rate is equal to the maximum cumulative methane production rate divided by the volatile solid content in the fermentation substrate, and the maximum methane production rates of Run 1, Run 2, Run 3 and Run 4 are 344.69 mL / g VS, 299.80 mL / g VS, 172.61 mL / g VS and 102.51 mL / g VS, respectively, so when Run 1, the maximum methane production rate is the largest, which is 344.69 mL / g VS.

[0043] The reason why the present embodiment is screened between 2:8 and 8:2 of cow manure: pig manure is that although a high proportion of pig manure improves the short-term methane production rate, there are the following risks in preparing only pig manure: 1. High risk of organic acid accumulation (especially acetic acid and propionic acid), which can easily lead to a decrease in pH; 2. Lack of fiber slow-release carbon source, which can easily cause metabolic disorders in the system; 3. Easy to cause rapid release of ammonia nitrogen, which can inhibit microorganisms; 4. Poor dewatering and viscous biogas residue. Cow manure contains a high proportion of cellulose / hemicellulose, which is released slowly, helps to buffer the accumulation of acidity in the system, and enhances the slow-release and stability of the fermentation system. At the same time, the removal effect of Cr, Cd and Pb by mixed anaerobic fermentation through microbial synergistic effect or organic matter complexation is better than that by single raw material fermentation, which indicates that the addition of cow manure can effectively enhance the heavy metal removal effect; mixed anaerobic fermentation is more conducive to the overall enrichment of nutrients such as nitrogen, phosphorus and potassium, especially in total nitrogen, alkali-hydrolyzable nitrogen, total phosphorus and total potassium content, which is suitable for long-acting organic fertilizer for basic fertilization. In addition, the anaerobic fermentation system shows good environmental purification potential in reducing and resisting biological pollution factors, and has no significant adverse effects on pathogen control and ARGs stability, which verifies the feasibility and ecological safety of the mixed fermentation process. Therefore, the biogas fertilizer obtained by mixing cow manure and pig manure in the ratio of 2:8 to 8:2 has agricultural potential and environmental safety.

[0044] The above embodiments of the present application determine the mixing ratio suitable for mixed raw material fermentation according to the raw material composition of two-stage mixed anaerobic fermentation of cow manure and pig manure in different fermentation characteristics of fermentation raw materials. The above embodiments of the present application realize the significant improvement of cumulative methane production and maximum methane production rate, and provide a feasible method for solving the problem of low gas production efficiency of single raw material fermentation, which has important reference value for mixed raw material fermentation biogas production technology of anaerobic fermentation biogas production engineering.

[0045] Those skilled in the art know that, in addition to implementing the system and each device, module and unit thereof provided by the present application in the form of pure computer readable program code, the same function can also be realized by logically programming the method steps to make the system and each device, module and unit thereof provided by the present application in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers and embedded microcontrollers. Therefore, the system and each device, module and unit thereof provided by the present application can be considered as a hardware component, and the devices, modules and units included therein for realizing various functions can also be considered as structures within the hardware component; the devices, modules and units for realizing various functions can also be considered as both software modules realizing methods and structures within hardware components.

[0046] The specific embodiments of the present application are described above. It needs to be understood that the present application is not limited to the specific embodiments described above, and various modifications or changes can be made by those skilled in the art within the scope of the claims, which do not affect the essence of the present application.

Claims

1. An analytical method for producing biogas and biogas fertilizer by anaerobic fermentation of mixed raw materials, characterized in that: The following steps are involved: S1, collecting pig manure and cow manure as fermentation raw materials; S2, after removing impurities from the anaerobic fermentation inoculum, performing activation culture treatment to obtain a methanogenic inoculum; S3, mixing the pig manure and cow manure in the fermentation raw materials of step S1 in different proportions, adding the methanogenic inoculum of step S2 respectively for anaerobic fermentation, and collecting fermentation data; S4, fitting the biogas fermentation data in step S3 to the Modified Gompertz kinetic model to obtain kinetic parameters; S5. Analyze the biogas fermentation data in step S3 and the kinetic parameters in step S4, and determine the optimal ratio of pig manure to cow manure after comprehensive evaluation.

2. The analysis method according to claim 1, characterized in that In step S1, the pig manure is collected from a breeding farm and impurities are picked out; the cow manure is collected from a breeding farm and impurities are picked out; the impurities include at least one of stones, metals, and feathers.

3. The analysis method according to claim 1, characterized in that In step S2, the anaerobic fermentation inoculum includes anaerobic activated sludge.

4. The analysis method according to claim 1, characterized in that In step S2, the activation culture treatment includes: adding nutrients to the anaerobic fermentation inoculum, culturing until the methane content in the produced biogas exceeds 50%, and then stopping adding nutrients until no biogas is produced.

5. The analysis method according to claim 4, characterized in that The nutrients include one or more of glucose, acetic acid, sucrose, and soluble starch.

6. The analysis method according to claim 1, characterized in that In step S3, the solid content of the fermentation feedstock in the mixed system of the fermentation feedstock and the methanogenic inoculum is 4%-8%; and the mass ratio of the methanogenic inoculum to the fermentation feedstock is 4-6:

1.

7. The analysis method according to claim 1, characterized in that In step S3, the temperature of the anaerobic fermentation is 35±2° C., and the period is 45 days.

8. The analysis method according to claim 1, characterized in that In step S3, the fermentation data includes biogas fermentation data and biogas fertilizer fermentation data; wherein, the biogas fermentation data includes the cumulative methane production M(t) and the test time t; the biogas fertilizer fermentation data includes the organic matter index, NPK index, ammonia nitrogen index, heavy metal index, and resistance gene index.

9. The analysis method according to claim 1, characterized in that In step S4, the kinetic parameters include the final methanogenic potential M max , maximum methanogenesis rate R max , hysteresis period λ; the fitting includes nonlinear regression fitting; The calculation formula of the kinetic parameters in the Modified Gompertz kinetic model is as follows: Where M(t) is the cumulative methane production at time t, mL; M max is the final methane production potential, mL; R max is the maximum methanogenesis rate, mL / d; λ is the hysteresis period, d; t is the test time, d; and e is a constant of 2.7183.

10. An analysis system for producing biogas and biogas fertilizer by anaerobic fermentation of mixed raw materials, comprising: Module M1, collecting pig manure and cow manure as fermentation raw materials; Module M2: After removing impurities from the anaerobic fermentation inoculum, an activation culture treatment is performed to obtain a methanogenic inoculum; Module M3: Mix the pig manure and cow manure in the fermentation raw materials of module M1 in different proportions, add the methane-producing inoculum of module M2 to perform anaerobic fermentation, and collect fermentation data; Module M4, fitting the biogas fermentation data in module M3 to the Modified Gompertz kinetic model to obtain kinetic parameters; Module M5 analyzes the biogas fermentation data in module M3 and the kinetic parameters in module M4, and determines the optimal ratio of pig manure and cow manure after comprehensive evaluation.

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