A process for stabilizing an anaerobic fermentation system

Abstract

The present application relates to the environmental protection treatment of poultry manure, in particular to a process for stabilizing an anaerobic fermentation system, the present application collects the manure with a total concentration of 6% concentration, carries out anaerobic fermentation, improves the types of antibiotics, promotes the activity of hydrogenophilic methanogen flora, and improves the electrode material of microbial electrolysis cell, so that the obtained anaerobic fermentation system is not only high in stability, but also rich in methane production.

Description

Technical Field

[0001] This invention belongs to the field of anaerobic fermentation technology, specifically relating to a process for a stable anaerobic fermentation system. Background Technology

[0002] Anaerobic fermentation is an organic matter decomposition and metabolism process involving the combined action of various specific microorganisms. In this process, organic matter (such as human and animal excrement, straw, weeds, etc.) is decomposed and metabolized by various microorganisms under certain moisture, temperature and anaerobic conditions, ultimately forming a combustible gas mixture mainly composed of methane and carbon dioxide (containing small amounts of hydrogen sulfide and ammonia, etc.), while simultaneously producing a certain amount of biogas slurry and biogas residue.

[0003] Anaerobic fermentation does not require oxygen, reducing power consumption and operating costs; the biogas produced after anaerobic fermentation is a clean energy source; fermented organic solids can yield high-quality organic fertilizers and soil conditioners, offering good economic benefits; and waste volume is reduced during the conversion of organic matter into methane. Anaerobic fermentation technology can effectively achieve the "harmlessness, reduction, and resource recovery" of solid waste treatment, thus possessing broad application prospects.

[0004] Sulfonamides, as common antibiotics, are frequently used in livestock and poultry farming, and are discharged into manure as parent compounds and metabolites, affecting anaerobic fermentation. During microbial anaerobic fermentation, acesulfame potassium, a metabolite of sulfonamides, undergoes a certain degree of reverse transformation, often resulting in negative migration. This leads to an increase in the concentration of sulfonamides released into the environment. Increased sulfonamide levels may threaten microbial growth and affect the structure and function of the microbial community. Therefore, selecting a suitable sulfonamide to maximize the promotion of anaerobic fermentation is the focus of this invention.

[0005] Biosurfactants possess advantages such as being environmentally friendly and highly efficient, and have been widely used in pollutant treatment. Surfactants can effectively reduce the reactive energy of reactions, thereby accelerating the reaction process. They can also effectively enhance the hydrolysis of saline sludge treated by thermophilic bacteria and promote enzyme release, further enhancing the metabolism of organic matter. The addition of surfactants to promote microbial activity is the focus of this invention.

[0006] Microbial electrolysis cells are driven by electroactive microorganisms. Under the application of a relatively small voltage, they can convert organic waste into valuable products. The basic principle of microbial electrolysis cells is as follows: electroactive microorganisms attached to the surface of the anode of the microbial electrolysis cell oxidize organic matter into electrons, protons and carbon dioxide. Electroactive microorganisms transfer electrons to the anode through the extracellular electron transfer mechanism. Under the drive of an external electric field, electrons are transferred from the anode to the cathode through the external circuit, where they combine with hydrogen ions to produce hydrogen gas.

[0007] While microbial electrolysis-anaerobic fermentation significantly improves methanogenesis compared to traditional anaerobic fermentation, its conversion efficiency remains relatively low. To further enhance the performance of microbial electrolysis-anaerobic fermentation, improvements to the microbial electrolysis cell are necessary. Many factors influence the performance of microbial electrolysis cells, such as reactor configuration, input voltage, bioactivity, and electrode materials. Among these, the electrode material not only serves as a carrier for functional microorganisms but also determines the electron transfer efficiency, which has a crucial impact on the performance of the microbial electrolysis cell. Therefore, selecting a material with superior electrochemical performance is one of the key directions of this invention. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the specific preparation process of the present invention is as follows:

[0009] Livestock and poultry breeding waste with a total TS concentration of 6% was collected as fermentation raw material and added to a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used to apply a voltage of 40-60V to both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive terminal of the power supply, and the cathode was connected to the negative terminal. A 10Ω resistor was connected in series in the circuit. After connection, 100 portions of livestock and poultry breeding waste were taken, and 8-10% of hydrogen-producing methanogens were added. 0.03-0.12% of sulfonamide antibiotics were added, and triacetic acid was added to adjust the pH to 6-6.5. Then, 4-8% of surfactant was added to promote anaerobic fermentation. Nitrogen gas with a purity of 99% was first introduced for 5 minutes. When gas production stopped, the biofilm formation stage was completed. After electrolysis for 12 hours, intermittent power supply was used, and the operation was repeated for 5 cycles.

[0010] The hydrogen-producing methanogens include a mixture of Methanobacter brunelli and Methanobacter borgos;

[0011] The intermittent power supply is characterized by a 12-hour power-on state and a 12-hour power-off state, which constitutes one cycle.

[0012] The sulfonamide antibiotic in question is sulfadiazine.

[0013] The surfactant is dialkylethanolamine methyl sulfate ammonium.

[0014] The cathode of the microbial electrolysis cell is a 316L stainless steel mesh, which is soaked in 1 mol / L H2SO4 for 4 hours before use and then washed with deionized water; the anode is a modified carbon cloth coated with a special material.

[0015] Anodic modification raw material: Mix 60-70 parts of 25% ferric chloride hexahydrate solution and an equal amount of 10-18% modification liquid and 25 parts of water, and sonicate for 30 minutes. After mixing evenly, add the mixture to a stainless steel high-pressure reactor lined with polytetrafluoroethylene. React at 130℃ for 72 hours. After natural cooling, collect the product by centrifugation. Wash the obtained product three times with deionized water at 70℃ for 2 hours at a material-to-liquid ratio of 1:350. Then wash it once with anhydrous ethanol at 70℃ for 12 hours at a material-to-liquid ratio of 1:350. Finally, dry the product under vacuum at 150℃ for 12 hours and grind it to obtain the modified raw material. Store it in a dry environment for later use.

[0016] Anodic modified carbon cloth coating: Take 0.5-0.8 parts of the modified raw material prepared above, 1 part of ethanol, 0.6-0.8 parts of water, and 0.1 parts of polytetrafluoroethylene, mix and shake until uniform, spread out a 2cm x 4cm carbon cloth, apply the mixture onto the carbon cloth, and dry in a vacuum oven at 60℃ for 12h to obtain the final product.

[0017] The modified liquid is 5-sulfo-o-aminobenzoic acid.

[0018] The beneficial effects of this invention are as follows:

[0019] 1. This invention relates to the environmentally friendly treatment of poultry manure, particularly a process for a stable anaerobic fermentation system. This invention involves the complete collection of manure with a TS concentration of 6%, followed by anaerobic fermentation. By improving the types of antibiotics, promoting the activity of hydrogen-producing methanogens, and improving the electrode materials of the microbial electrolysis cell, the resulting anaerobic fermentation system is not only highly stable but also produces abundant methane.

[0020] 2. Sulfamide can significantly increase the yield of short-chain fatty acids during anaerobic fermentation, which helps improve the conversion efficiency of organic matter during fermentation. Furthermore, various microbial strains capable of degrading sulfonamides exist in activated sludge, long-term treated soil, and excrement. These strains can utilize sulfamide as their sole carbon source for growth and reproduction, thereby degrading sulfamide. During anaerobic fermentation, sulfamide is not only degraded, but the antibacterial activity of its metabolites is also significantly reduced, thus decreasing the risk of resistance gene transmission. Simultaneously, the degradation process also enhances the growth of anaerobic bacteria.

[0021] 3. The presence of sulfanilamide promotes the growth of hydrogen-producing methanogens, which can effectively convert organic matter into methane in anaerobic environments, thus improving energy recovery efficiency. Sulfanilamide competitively inhibits the growth of specific bacteria, effectively reducing the prevalence of most harmful microorganisms, including Gram-positive and Gram-negative bacteria, thereby promoting the reproduction and metabolism of beneficial microorganisms in the anaerobic fermentation system.

[0022] 4. The methoxy structure contained in sulfanilamide enhances the reactivity of compounds linked to the methoxy group through a conjugation effect, enabling microorganisms to more effectively convert sulfonamide antibiotics and their metabolites into other harmless or more easily degradable substances, reducing negative migration and ensuring the stability of the anaerobic fermentation system.

[0023] 5. Dialkylethanolamine methyl methyl sulfate ammonium is a cationic surfactant. The ethanolamine ester and methyl methyl sulfate ammonium moieties in its molecular structure endow it with good biocompatibility and mild properties, making it perform well in a variety of applications.

[0024] 6. Utilizing the hydrophobic and hydrophilic properties of dialkylethanolamine methyl methyl sulfate ammonium, the surface tension of non-aqueous organic matter is reduced to improve its water solubility; its charged nature is used to disperse sludge flocs, alter the cell structure of microorganisms, and separate other bacterial aggregates attached to the surface of microorganisms, thereby promoting anaerobic fermentation and acid production; by disrupting the cell membrane of methanogens in the anaerobic system, their activity is inhibited, acetic acid consumption is reduced, and volatile fatty acids accumulate.

[0025] 7. Dialkylethanolamine methyl methyl sulfate ammonium, through two different ethanolamine esters and methyl methyl sulfate ammonium, changes the surface charge of the substrate to weaken the repulsive force, thereby promoting the interaction between hydrolytic enzymes and substrates, significantly improving solubilization and hydrolysis efficiency, promoting the acidification process, providing better substrate conditions for subsequent methane fermentation, and thus optimizing the efficiency and stability of the entire anaerobic fermentation process.

[0026] 8. By self-assembling 5-sulfo-o-aminobenzoic acid with iron ions to form highly ordered porous crystals, the resulting anodic electrolytic material not only possesses a large specific surface area and high porosity but also exhibits strong redox activity. 5-sulfo-o-aminobenzoic acid contains multiple functional groups that can form coordination bonds with iron ions, promoting intermolecular bonding and forming stable complexes. Therefore, the modified electrolytic material not only facilitates microbial attachment and enzyme immobilization but also increases electron transfer rates, thereby accelerating hydrogen production, promoting the growth of hydrogen-producing and methanogenic bacteria, and ultimately improving methane production and system stability.

[0027] 9. The modified electrolytic cell not only accelerates the decomposition and utilization of volatile acids and reduces the overall concentration of volatile acids throughout the cycle, thereby mitigating acid inhibition and increasing methane production; it also generates more ammonia nitrogen at low concentrations, promoting the growth of methanogenic bacteria, which plays a crucial role in increasing methane production. Furthermore, combined with an intermittent power supply operation mode, it achieves high methane production with low energy consumption. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the embodiments.

[0029] All raw materials used in this invention embodiment are from nearby livestock and poultry farms and farmland waste. The DC stabilizing power supply was purchased from Shanghai Xishun Electric Co., Ltd., and the carbon cloth, 2cm x 4cm in size and WLS1011, was purchased from Taiwan Carbon Energy Co., Ltd. Unless otherwise specified, all other raw materials or chemical reagents were obtained through conventional commercial channels.

[0030] The TS concentration refers to livestock and poultry breeding waste. According to section 3.4 of Jiangxi Provincial Standard DB36 / T1546-2021, full-scale collection, storage, and transportation refers to the complete collection, temporary storage, and transportation of livestock and poultry breeding waste generated by farms through appropriate measures. Third-party organizations should sign agreements with livestock and poultry breeding enterprises (households) to establish a sound system for the collection, storage, and transportation of livestock and poultry breeding waste, ensuring that the total solids content of livestock and poultry manure is not less than 6% and that diseased and dead livestock and poultry are collected.

[0031] Example 1

[0032] The cathode of the microbial electrolysis cell is a 316L stainless steel mesh, which is soaked in 1 mol / L H2SO4 for 4 hours before use, and then washed with deionized water; the anode is made by coating modified carbon cloth, specifically:

[0033] Anodic modification raw material: 65 parts of 25% ferric chloride hexahydrate solution and an equal amount of 14% 5-sulfo-o-aminobenzoic acid and 25 parts of water were mixed and ultrasonicated for 30 minutes. After mixing evenly, the mixture was added to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted at 130℃ for 72 hours. After natural cooling, the product was collected by centrifugation. The obtained product was washed three times with deionized water at 70℃ for 2 hours according to a material-to-liquid ratio of 1:350. Then it was washed once with anhydrous ethanol at 70℃ for 12 hours according to a material-to-liquid ratio of 1:350. After drying under vacuum at 150℃ for 12 hours, it was ground to obtain the modified raw material, which was stored in a dry environment for later use.

[0034] Anodic modified carbon cloth coating: Take 0.6 parts of the modified raw material prepared above, 1 part of ethanol, 0.7 parts of water, and 0.1 parts of polytetrafluoroethylene, mix them and shake until uniform. Spread out a 2cm x 4cm carbon cloth and apply the mixture onto the carbon cloth. Dry it in a vacuum oven at 60℃ for 12 hours to obtain the final product.

[0035] Livestock and poultry waste with a total TS concentration of 6% was collected as fermentation raw material and added to a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used to apply a 50V voltage to both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive terminal of the power supply, and the cathode was connected to the negative terminal. A 10Ω resistor was connected in series in the circuit. After connection, 100 portions of livestock and poultry waste were taken, 9% of hydrogen-producing methanogens were added, 0.07% of sulfadiazine was added, and after adjusting the pH to 6.2 with nitric acid, 6% of dialkylethanolamine methyl sulfate ammonium was added to promote anaerobic fermentation. Nitrogen gas with a purity of 99% was first introduced for 5 minutes. When gas production stopped, the biofilm formation stage was completed. After electrolysis for 12 hours, intermittent power supply was used. The power was turned on for 12 hours and turned off for 12 hours. The operation was repeated for 5 cycles.

[0036] Example 2

[0037] The cathode of the microbial electrolysis cell is a 316L stainless steel mesh, which is soaked in 1 mol / L H2SO4 for 4 hours before use, and then washed with deionized water; the anode is made by coating modified carbon cloth, specifically:

[0038] Anodic modification raw material: 60 parts of 25% ferric chloride hexahydrate solution and an equal amount of 18% 5-sulfo-o-aminobenzoic acid and 25 parts of water were mixed and ultrasonicated for 30 minutes. After mixing evenly, the mixture was added to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted at 130℃ for 72 hours. After natural cooling, the product was collected by centrifugation. The obtained product was washed three times with deionized water at 70℃ for 2 hours according to a material-to-liquid ratio of 1:350. Then it was washed once with anhydrous ethanol at 70℃ for 12 hours according to a material-to-liquid ratio of 1:350. After drying under vacuum at 150℃ for 12 hours, the modified raw material was obtained and stored in a dry environment for later use.

[0039] Anodic modified carbon cloth coating: Take 0.8 parts of the modified raw material prepared above, 1 part of ethanol, 0.6 parts of water, and 0.1 parts of polytetrafluoroethylene, mix them and shake until uniform. Spread out a 2cm x 4cm piece of carbon cloth and apply the mixture onto the carbon cloth. Dry it in a vacuum oven at 60℃ for 12 hours to obtain the final product.

[0040] Livestock and poultry waste with a total TS concentration of 6% was collected as fermentation raw material and added to a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used to apply a 60V voltage to both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive terminal of the power supply, and the cathode was connected to the negative terminal. A 10Ω resistor was connected in series in the circuit. After connection, 100 portions of livestock and poultry waste were taken, 8% of hydrogen-producing methanogens were added, 0.12% of sulfadiazine was added, and the pH was adjusted to 6 by adding nitric acid. Then, 8% of dialkylethanolamine methyl sulfate ammonium was added to promote anaerobic fermentation. Nitrogen gas with a purity of 99% was first introduced for 5 minutes. When gas production stopped, the biofilm formation stage was completed. After electrolysis for 12 hours, intermittent power supply was used. The power was turned on for 12 hours and turned off for 12 hours. The operation was repeated for 5 cycles.

[0041] Example 3

[0042] The cathode of the microbial electrolysis cell is a 316L stainless steel mesh, which is soaked in 1 mol / L H2SO4 for 4 hours before use, and then washed with deionized water; the anode is made by coating modified carbon cloth, specifically:

[0043] Anodic modification raw material: 70 parts of 25% ferric chloride hexahydrate solution, an equal amount of 10% 5-sulfo-o-aminobenzoic acid and 25 parts of water were mixed and ultrasonicated for 30 minutes. After mixing evenly, the mixture was added to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted at 130℃ for 72 hours. After natural cooling, the product was collected by centrifugation. The obtained product was washed three times with deionized water at 70℃ for 2 hours according to a material-to-liquid ratio of 1:350. Then it was washed once with anhydrous ethanol at 70℃ for 12 hours according to a material-to-liquid ratio of 1:350. After drying under vacuum at 150℃ for 12 hours, it was ground to obtain the modified raw material, which was stored in a dry environment for later use.

[0044] Anodic modified carbon cloth coating: Take 0.5 parts of the modified raw material prepared above, 1 part of ethanol, 0.8 parts of water, and 0.1 parts of polytetrafluoroethylene, mix them and shake until uniform. Spread out a 2cm x 4cm piece of carbon cloth and apply the mixture onto the carbon cloth. Dry it in a vacuum oven at 60℃ for 12 hours to obtain the final product.

[0045] Livestock and poultry waste with a total TS concentration of 6% was collected as fermentation raw material and added to a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used to apply a voltage of 40-60V to both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive terminal of the power supply, and the cathode was connected to the negative terminal. A 10Ω resistor was connected in series in the circuit. After connection, 100 portions of livestock and poultry waste were taken, 10% of hydrogen-producing methanogens were added, 0.03% of sulfadiazine was added, and after adjusting the pH to 6.5 with nitric acid, 4% of dialkylethanolamine methyl sulfate ammonium was added to promote anaerobic fermentation. Nitrogen gas with a purity of 99% was first introduced for 5 minutes. When gas production stopped, the biofilm formation stage was completed. After electrolysis for 12 hours, intermittent power supply was used. The power was turned on for 12 hours and turned off for 12 hours. The operation was repeated for 5 cycles.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 1 is that this comparative example does not use an electrolytic cell device. The specific steps are as follows:

[0048] Livestock and poultry breeding waste with a total TS concentration of 6% was collected as fermentation raw material. 100 portions of livestock and poultry breeding waste were taken, 10% of hydrogen-producing methanogens were added, 0.03% of sulfadiazine was added, and after adjusting the pH to 6.5 with nitric acid, 4% of dialkylethanolamine methyl sulfate ammonium was added to promote anaerobic fermentation of microorganisms. Nitrogen gas with a purity of 99% was first introduced for 5 minutes, and then fermentation was continued for 5.5 days.

[0049] Comparative Example 2

[0050] The difference between this comparative example and Example 1 is that the anode in the electrolyte is not modified, the anode is a 2cm x 4cm carbon cloth, and the cathode is a 316L stainless steel mesh. Before use, it is soaked in 1mol / LH2SO4 for 4h and then washed with deionized water.

[0051] Livestock and poultry waste with a total TS concentration of 6% was collected as fermentation raw material and added to a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used to apply a 50V voltage to both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive terminal of the power supply, and the cathode was connected to the negative terminal. A 10Ω resistor was connected in series in the circuit. After connection, 100 portions of livestock and poultry waste were taken, 9% of hydrogen-producing methanogens were added, 0.07% of sulfadiazine was added, and after adjusting the pH to 6.2 with nitric acid, 6% of dialkylethanolamine methyl sulfate ammonium was added to promote anaerobic fermentation. Nitrogen gas with a purity of 99% was first introduced for 5 minutes. When gas production stopped, the biofilm formation stage was completed. After electrolysis for 12 hours, intermittent power supply was used. The power was turned on for 12 hours and turned off for 12 hours. The operation was repeated for 5 cycles.

[0052] Comparative Example 3

[0053] The difference between this comparative example and Example 1 is that 5-sulfo-o-aminobenzoic acid is replaced with benzoic acid in the steps; the rest is the same as in Example 1.

[0054] Comparative Example 4

[0055] The difference between this comparative example and Example 1 lies in the amount of 5-sulfo-o-aminobenzoic acid added. Specifically, the anode modification raw material is as follows: 65 parts by mass of 25% ferric chloride hexahydrate solution, an equal amount of 28% 5-sulfo-o-aminobenzoic acid, and 25 parts by mass of water are mixed and ultrasonicated for 30 minutes. After mixing evenly, the mixture is added to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted at 130°C for 72 hours. After natural cooling, the product is collected by centrifugation. The obtained product is washed three times with deionized water at 70°C for 2 hours at a material-to-liquid ratio of 1:350, and then washed once with anhydrous ethanol at 70°C for 12 hours at a material-to-liquid ratio of 1:350. After that, it is dried under vacuum at 150°C for 12 hours and then ground to obtain the modified raw material, which is stored in a dry environment for later use. The rest is the same as in Example 1.

[0056] Comparative Example 5

[0057] The difference between this comparative example and Example 1 lies in the amount of 5-sulfo-o-aminobenzoic acid added. Specifically, the anode modification raw material is as follows: 65 parts by mass of 25% ferric chloride hexahydrate solution, an equal amount of 6% 5-sulfo-o-aminobenzoic acid, and 25 parts by mass of water are mixed and ultrasonicated for 30 minutes. After mixing evenly, the mixture is added to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted at 130°C for 72 hours. After natural cooling, the product is collected by centrifugation. The obtained product is washed three times with deionized water at 70°C for 2 hours at a material-to-liquid ratio of 1:350, and then washed once with anhydrous ethanol at 70°C for 12 hours at a material-to-liquid ratio of 1:350. After that, it is dried under vacuum at 150°C for 12 hours and then ground to obtain the modified raw material, which is stored in a dry environment for later use. The rest is the same as in Example 1.

[0058] Comparative Example 6

[0059] The difference between this comparative example and Example 1 is that sulfadiazine is not added; otherwise, it is the same as Example 1.

[0060] Comparative Example 7

[0061] The difference between this comparative example and Example 1 is that sulfadiazine is used instead of sulfadiazine; otherwise, it is the same as Example 1.

[0062] Comparative Example 8

[0063] The difference between this comparative example and Example 1 is that the amount of sulfadiazine added is different. Specifically, livestock and poultry breeding waste with a total TS concentration of 6% was collected as fermentation raw material and added to a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used to apply a 50V voltage to both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive terminal of the power supply, and the cathode was connected to the negative terminal. A 10Ω resistor was connected in series in the circuit. After connection, 100 portions of livestock and poultry breeding waste were taken, 9% of hydrogen-producing methanogens were added, 0.16% of sulfadiazine was added, and after adjusting the pH to 6.2 with nitric acid, 6% of dialkylethanolamine methyl sulfate ammonium was added to promote anaerobic fermentation. Nitrogen gas with a purity of 99% was first introduced for 5 minutes. When gas production ceased, the biofilm formation stage was completed. After electrolysis for 12 hours, intermittent power supply was used. The power was turned on for 12 hours and turned off for 12 hours, and the operation was repeated for 5 cycles. The rest was the same as in Example 1.

[0064] Comparative Example 9

[0065] The difference between this comparative example and Example 1 is that the amount of sulfadiazine added is different. Specifically, livestock and poultry breeding waste with a total TS concentration of 6% was collected as fermentation raw material and added to a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used to apply a 50V voltage to both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive terminal of the power supply, and the cathode was connected to the negative terminal. A 10Ω resistor was connected in series in the circuit. After connection, 100 portions of livestock and poultry breeding waste were taken, 9% of hydrogen-producing methanogens were added, 0.01% of sulfadiazine was added, and after adjusting the pH to 6.2 with nitric acid, 6% of dialkylethanolamine methyl sulfate ammonium was added to promote anaerobic fermentation. Nitrogen gas with a purity of 99% was first introduced for 5 minutes. When gas production ceased, the biofilm formation stage was completed. After electrolysis for 12 hours, intermittent power supply was used. The power was turned on for 12 hours and turned off for 12 hours, and the operation was repeated for 5 cycles. The rest was the same as in Example 1.

[0066] Comparative Example 10

[0067] The difference between this comparative example and Example 1 is that dialkylethanolamine methyl sulfate ammonium is not added in this comparative example; otherwise, it is the same as in Example 1.

[0068] Comparative Example 11

[0069] The difference between this comparative example and Example 1 is that in this comparative example, dialkylethanolamine methyl sulfate ammonium is replaced with alkylpropylenediamine; otherwise, it is the same as in Example 1.

[0070] Comparative Example 12

[0071] The difference between this comparative example and Example 1 is that the amount of dialkylethanolamine methyl methyl sulfate ammonium added is different. Specifically, livestock and poultry breeding waste with a total TS concentration of 6% was collected as fermentation raw material and added to a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used to apply a 50V voltage to both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive terminal of the power supply, and the cathode was connected to the negative terminal. A 10Ω resistor was connected in series in the circuit. After connection, 100 portions of livestock and poultry breeding waste were taken, 9% of hydrogen-producing methanogens were added, 0.07% of sulfadiazine was added, and after adjusting the pH to 6.2 with nitric acid, 12% of dialkylethanolamine methyl methyl sulfate ammonium was added to promote microbial anaerobic fermentation. Nitrogen gas with a purity of 99% was first introduced for 5 minutes. When gas production ceased, the biofilm formation stage was completed. After electrolysis for 12 hours, intermittent power supply was used. The power was turned on for 12 hours and turned off for 12 hours, and the operation was repeated for 5 cycles. The rest was the same as in Example 1.

[0072] Comparative Example 13

[0073] The difference between this comparative example and Example 1 is that the amount of dialkylethanolamine methyl methyl sulfate ammonium added is different. Specifically, livestock and poultry breeding waste with a total TS concentration of 6% was collected as fermentation raw material and added to a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used to apply a 50V voltage to both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive terminal of the power supply, and the cathode was connected to the negative terminal. A 10Ω resistor was connected in series in the circuit. After connection, 100 portions of livestock and poultry breeding waste were taken, 9% of hydrogen-producing methanogens were added, 0.07% of sulfadiazine was added, and after adjusting the pH to 6.2 with nitric acid, 2% of dialkylethanolamine methyl methyl sulfate ammonium was added to promote anaerobic fermentation. Nitrogen gas with a purity of 99% was first introduced for 5 minutes. When gas production ceased, the biofilm formation stage was completed. After electrolysis for 12 hours, intermittent power supply was used. The power was turned on for 12 hours and turned off for 12 hours, and the operation was repeated for 5 cycles. The rest was the same as in Example 1.

[0074] Experiment 1: Determination of volatile fatty acid content

[0075] Volatile fatty acids were determined using an Agilent 7890B gas chromatograph. 5g of anaerobic fermentation products from Examples 1-3 and Comparative Examples 1-13 were filtered through a 60-mesh (approximately 0.25mm pore size) sieve, and the liquid phase was collected as the research sample. The results are shown in Table 1.

[0076] Table 1. Volatile fatty acid concentrations

[0077] Group Acetic acid content (%) Propionic acid content (%) Isobutyric acid content (%) Example 1 89.75 7.05 1.84 Example 2 88.76 7.21 1.86 Example 3 88.64 7.77 1.87 Comparative Example 1 58.16 15.89 3.80 Comparative Example 2 66.87 13.20 3.24 Comparative Example 3 68.59 11.54 2.57 Comparative Example 4 84.76 9.84 2.10 Comparative Example 5 79.41 10.36 2.39 Comparative Example 6 68.74 14.78 3.69 Comparative Example 7 72.85 14.23 3.31 Comparative Example 8 85.42 9.28 1.98 Comparative Example 9 80.23 11.47 2.18 Comparative Example 10 70.64 13.69 3.54 Comparative Example 11 74.58 11.87 2.83 Comparative Example 12 84.72 8.91 2.07 Comparative Example 13 81.62 9.64 2.26

[0078] Experiment 2: Methanogenesis and stability of the anaerobic fermentation process of this invention

[0079] The anaerobic fermentation process was carried out according to the methods of Examples 1-3 and Comparative Examples 1-13. The amount of CH4 produced per unit of material and the amount of CO2 produced per unit of material were tested, and the CH4 / CO2 ratio was calculated. During the fermentation process, CO2 is both an intermediate product of the liquefaction stage and a raw material for the generation of acetic acid and CH4 in the acid production and methanogenesis stages. Therefore, the larger the CH4 / CO2 ratio, the stronger the activity of methanogens and the better the stability of the anaerobic system. The results are shown in Table 2 below.

[0080] Table 2. Methane production and stability

[0081]

[0082]

Claims

1. A process for a stable anaerobic fermentation system, characterized in that: Livestock and poultry breeding waste with a total TS concentration of 6% was collected as fermentation raw material and added to a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used to apply a voltage of 40-60V to both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive terminal of the power supply, and the cathode was connected to the negative terminal. A 10Ω resistor was connected in series in the circuit. After connection, 100 portions of livestock and poultry breeding waste were taken, and 8-10% of hydrogen-producing methanogens were added. 0.03-0.12% of sulfonamide antibiotics were added, and triacetic acid was added to adjust the pH to 6-6.

5. Then, 4-8% of surfactant was added to promote anaerobic fermentation. Nitrogen gas with a purity of 99% was first introduced for 5 minutes. When gas production stopped, the biofilm formation stage was completed. After electrolysis for 12 hours, intermittent power supply was used, and the operation was repeated for 5 cycles. The hydrogen-producing methanogens include a mixture of Methanobacter brunelli and Methanobacter borgos; The intermittent power supply is characterized by a 12-hour power-on state and a 12-hour power-off state, which constitutes one cycle. The sulfonamide antibiotic is sulfadiazine; The surfactant is dialkylethanolamine methyl methyl sulfate ammonium; The cathode of the microbial electrolysis cell is a 316L stainless steel mesh, which is soaked in 1 mol / L H2SO4 for 4 hours before use and then washed with deionized water; the anode is a modified carbon cloth coated with a special material. Anodic modification raw material: Mix 60-70 parts of 25% ferric chloride hexahydrate solution and an equal amount of 10-18% modification solution and 25 parts of water, and sonicate for 30 minutes. After mixing evenly, add the mixture to a stainless steel high-pressure reactor lined with polytetrafluoroethylene. React at 130℃ for 72 hours. After natural cooling, collect the product by centrifugation. Wash the obtained product three times with deionized water at 70℃ for 2 hours at a material-to-liquid ratio of 1:

350. Then wash it once with anhydrous ethanol at 70℃ for 12 hours at a material-to-liquid ratio of 1:

350. Dry it under vacuum at 150℃ for 12 hours. Grind the product to obtain the modified raw material and store it in a dry environment for later use. Anodic modified carbon cloth coating: Take 0.5-0.8 parts of the modified raw material, 1 part of ethanol, 0.6-0.8 parts of water, and 0.1 parts of polytetrafluoroethylene, mix and shake until uniform, spread out a 2cm x 4cm carbon cloth, apply the mixture onto the carbon cloth, and dry in a vacuum oven at 60℃ for 12h to obtain the product. The modified liquid is 5-sulfo-o-aminobenzoic acid.

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