A method for preparing fatty acids by biological hydrolysis coupling of soapstock and co-producing biogas

Abstract

The present invention discloses a method for hydrolyzing and coupling soapstock by biological method to jointly produce fatty acids and biogas, which comprises the following steps: Step 1: Mix materials, control the temperature and carry out aerobic fermentation. The materials include soapstock, acetic acid bacteria, methanobacterium and water. During the acidification of soap, the hydrolysis of oil by lipase is coupled to generate crude fatty acids. The water layer rich in organic matter is discharged into fermentation tank B, and the oil layer (crude fatty acids) is discharged into tank C. Step 2: Anaerobic fermentation is carried out in fermentation tank B. After the gas production is completed, the temperature is raised to denature and inactivate the microorganisms. Then, centrifugation is carried out to separate the solid phase, oil phase and water phase. The solid phase and water phase are used for ecological organic fertilizer, and the oil phase is merged into the crude fatty acid tank C. Step 3: After the crude fatty acids are heated, dehydrated and dried, rectification is carried out to obtain the finished fatty acids. The operation of the present invention is simple, the cost is low, it is environmentally friendly, and fatty acids, biogas and ecological organic fertilizer are obtained respectively, further improving the production benefit. The production process is safe and reliable and is convenient for popularization and application.

Description

Technical Field:

[0001] The present application relates to a method for manufacturing fatty acids and biomethane. Specifically, it relates to a method for hydrolyzing soapstock by biological method and coupling to produce fatty acids and co-generate biomethane, belonging to the field of soapstock resource biotechnology. Background Art:

[0002] Facing the major demands of the "dual carbon" goal and industrial transformation, improving the energy utilization efficiency of biological methods, using the three important substances of oils and fats, carbohydrates, and proteins existing in nature to form a biological manufacturing route to achieve industrial greening, through means such as process optimization, control, separation, and purification of biological fermentation, demonstrating the advantages of high-efficiency and low-cost production of biological methods, so as to realize the design and construction of a multi-cellular system for the conversion of biomethane and fatty acids, giving full play to the "empowering" potential of synthetic biology, and promoting the revolution of biological technology replacing traditional industries.

[0003] Oils and fats are one of the indispensable important components in food. Due to factors such as the maturity of oilseed growth, fungal contamination, and mildew during the growth process, the crude vegetable oil prepared has potential safety hazards for direct consumption. Therefore, vegetable oil refining is an essential link in edible oil. The soapstock (GB / T8873 - 2008) produced during refining is the largest by-product in the refining process.

[0004] The annual soapstock production in the country is about 2.6 million tons (data from the Oil and Fat Association). Its main components are a mixture of sodium (potassium) fatty acid salts, neutral oils, carbohydrates, proteins, pigments, vitamins, etc. and water. The traditional treatment process generally adopts the acidification method, that is, acidifying with 10 - 16% dilute sulfuric acid or concentrated hydrochloric acid to obtain a mixed oil layer (light phase) of fatty acids and neutral oils (triglycerides); a mixed water layer (heavy phase) of sodium sulfate or sodium chloride, pigments, carbohydrates, proteins, etc. suspended substances dissolved in water, and separating the mixed oil layer and the water layer using the density difference.

[0005] The above traditional soapstock treatment process, namely the acidification method, has various deficiencies:

[0006] Firstly, the oil layer (light phase) separated by adding inorganic acid is a mixture of fatty acids and neutral oil, with an acid value of 50 - 120 and cannot be directly rectified to obtain fatty acids (acid value around 200).

[0007] Secondly, adding inorganic acid combines with sodium and potassium ions in the soapstock to form salts such as sodium (potassium) sulfate and sodium (potassium) chloride, that is, the mixed water layer (heavy phase). At the same time, there are also problems in treating the wastewater containing excessive acid, sugar, and cake meal (protein) with inorganic salts.

[0008] With the country's increasing emphasis on environmental protection and resource utilization, the method of biochemically hydrolyzing coupled with fatty acid production and biogas production has become particularly important.

[0009] Fatty acids derived from vegetable oil bases are important biochemical intermediates and are widely used in the fields of daily chemicals, rubber, medicine, and bioenergy.

[0010] Biogas (CH4) is the main component of biogas produced by the anaerobic fermentation of food waste, plant straws, livestock manure, and waste plant cakes and meals by microorganisms. The dry reforming of biogas (CH4) and carbon dioxide (CO2) is a new negative-carbon path for syngas (H2+CO) production. It can be used for the production of important raw materials for zero-carbon methanol (CH3OH) and sustainable aviation biofuel (SAF). Biomanufacturing promotes the transformation and synthesis of energy chemicals and materials from biomass, breaking away from the new model of the petrochemical industry route, and has typical characteristics such as low-carbon cycle and green cleanliness. Summary of the Invention:

[0011] The present invention provides a method for preparing fatty acids and biogas by biochemically hydrolyzing coupled with waste soapstock, which solves the deficiencies of the existing process of recovering fatty acids by inorganic acidification of waste soapstock, as well as problems such as low purity of fatty acids and salt in the aqueous phase. The present invention first proposes: preparing fatty acids and biogas by biochemically hydrolyzing coupled with waste soapstock; maximizing the utilization of waste soapstock resources, with a simple, green, clean, and easy-to-promote application process.

[0012] To achieve the above technical effects, the present invention adopts the following technical solutions:

[0013] A method for preparing fatty acids and biogas by biochemically hydrolyzing coupled with waste soapstock, characterized in that the biochemical method is the identification of microbial flora diversity and its influence, and its growth and reproduction provide matrix nutrients including lipids, sugars, proteins, minerals, vitamins, and bioactive compounds in waste soapstock, providing an ideal environment for the growth and proliferation of microorganisms.

[0014] In the process of preparing crude vegetable oil, since the cake and meal have undergone ultra-high temperature sterilization operation, the waste soapstock obtained in the process of refining crude vegetable oil is also sterile.

[0015] A method for preparing fatty acids and biogas by biochemically hydrolyzing coupled with waste soapstock, comprising the following steps:

[0016] (1) Add waste soapstock to a fermentation tank equipped with a temperature control device, add a certain amount of deionized water, add acetic acid bacteria accounting for 0.8-3.0% of the soapstock at a temperature of 20-60°C, and at the same time add methane bacteria strains accounting for 1.0-5.0% of the soapstock. Start stirring, mix evenly, and control a certain viscosity, temperature, and pH value of the soapstock.

[0017] (2) Maintain the fermentation temperature at 20 - 60°C, the pH of the soap base at 6 - 8, introduce sterile air, and the ventilation volume accounts for 25 - 50% of the volume of the mixed materials. This ensures that Acetobacter grows vigorously under aerobic conditions and produces a large amount of acid; at the same time, the Methanobacterium flora produces acid under aerobic conditions. In the fermentation tank, by controlling the fermentation temperature, pH value, gas volume, glycerol concentration, sugar concentration, and nitrogen source in the soap base, cultivate for 24 hours. Since the density of the crude fatty acid is less than that of water, it floats on the upper layer of the fermentation tank. Take a sample, test the acid value. After passing the test, it is discharged to the fatty acid storage tank through the oil separation device of the fermentation tank, and the fatty acid finished product is obtained through rectification.

[0018] (3) Separate the fermented liquid from the oil layer, control the fermentation temperature at 40 - 68°C, stop introducing sterile air, and convert from the aerobic stage of the two-stage fermentation to the anaerobic stage. The aerobic Acetobacter is inhibited in growth under anaerobic conditions; for the Methanobacterium community, under anaerobic conditions, the construction of the strain cell factory and the enhancement of product synthesis, as well as the multi-dimensional coordinated regulation of anaerobic strains by the phosphorylation kinase, enable the fermented liquid rich in carbon source in the separated oil layer (fatty acid) to be converted into biogas methane (CH4). After the gas production ends, the temperature of the fermented liquid is raised to 70 - 100°C, the microorganisms are denatured and inactivated, and a small amount of fatty acid is extracted through three-phase separation to obtain water and residue, which are the traditional biogas slurry and biogas residue and are used for ecological organic fertilizer.

[0019] Furthermore, in step (1), the fermentation tank is a water-soluble temperature-controlled type with an internal cooling coil and has adjustable-speed stirring.

[0020] The Acetobacter belongs to the genus Acetobacter. Young bacteria are Gram-negative bacteria, and old bacteria often become Gram-positive bacteria. They have no spores, can move or cannot move, and are aerobic. Bacteria of this genus have strong oxidation ability and are easy to produce acid through fermentation of rich nutrients. We have found that bacteria of the genus Bacillus, Lactobacillus, or Streptococcus can metabolize the nutrients in soapstock to produce organic acids to decompose soapstock. The source of the strains is the China Center for Microbial Culture Collections. The Methanobacterium strains can be commercially available or selected and bred from municipal sludge. It belongs to a microbial community, and the identified microorganisms include: Methanobacterium, Methanoculleus, Pseudomonas, Lactococcus, Bacillus, Saccharomyces, Yarrowia lipolytica, Escherichia coli, etc. The fermentation temperature of these microorganisms is 20 - 60°C, preferably 40 - 45°C. Under aerobic conditions, organic acids such as acetic acid, propionic acid, butyric acid, lactic acid, glycolic acid, and pyruvic acid will be produced. They can acidify and decompose soapstock. During the acidification process, sodium (potassium) ions in the soapstock buffer the pH value of the acid fermentation and prevent the pH value from being too low, which inhibits the activity of microorganisms and reduces the production of organic acids. Lipase and phospholipase synthesized during the acid production process by microbial cells will couple and enzymatically hydrolyze the separated lipids to increase the acid value.

[0021] Further, in step (2), the aerobic fermentation temperature is 20 - 60°C, sterile air is introduced, and the ventilation volume accounts for 25 - 50% of the volume of the mixed materials. The microbial flora will synthesize organic acids, lipase hydrolysis, and phosphorylation kinases, etc.

[0022] When the mixture of soapstock undergoes aerobic fermentation, the organic acids produced include one or more of acetic acid, propionic acid, butyric acid, glycolic acid, and pyruvic acid, which neutralize or acidify sodium or potassium fatty acids in the soapstock to form fatty acids. At the same time, the lipase produced by microbial metabolism couples with the hydrolysis of triglycerides to produce fatty acids and glycerol, and glycerol can be used as an organic carbon source. After the mixture undergoes aerobic fermentation, the fatty acid oil phase and the mixed aqueous phase containing water-soluble organic carbon sources will stratify due to the density difference.

[0023] Further, the reaction formula in step (2) is as follows (the reactions proceed synchronously and coupled): RCOONa(K) + CH3COOH (or other organic acids) → RCOOH + CH3COONa(K)

[0024]

[0025] The acid value of the fatty acid / (mgKOH / g) GB / T5530, and the hydrolysis (acidification) is qualified when the test reaches 195 - 200 mgKOH / g, and further rectification is carried out to obtain the fatty acid finished product.

[0026] Further, in step (3), the upper oil layer (fatty acid) in the fermentation tank is separated, and the aerobic fermentation is converted to an anaerobic mode, and the temperature is raised to 40 - 60°C for control.

[0027] The water layer rich in organic carbon sources produces biogas methane (CH4) through anaerobic fermentation; the organic carbon sources include organic acids, organic salts, proteins, glycerol, carbohydrates, etc. Under anaerobic conditions, the biological flora will convert organic carbon sources such as organic acids, organic salts, proteins, glycerol, and carbohydrates in the fermentation broth into biogas methane (CH4) until no methane (CH4) is released, which is the end point of the reaction.

[0028] Further, in step (3), after the biogas methane production is completed, the temperature of the fermentation broth is raised to 70 - 100°C, and its purpose is to inactivate the microbial flora and convert it into ecological organic fertilizers such as biogas residues and biogas slurry. Description of the drawings:

[0029] Figure 1 Process flow chart of the method of the present invention Detailed implementation manners:

[0030] The following combines examples to detail the method for hydrolyzing and coupling the preparation of fatty acids and co-producing biogas methane by the biological method of soapstock provided by the present invention.

[0031] Example 1

[0032] In a method for preparing fatty acids and co-producing biogas from soapstock by biological hydrolysis coupling in this example, the soapstock is first detected: no pathogenic bacteria, acid value above 70 mg KOH / g after acidification, saponification value of 195 mg KOH / g, sugar and starch ≥ 8.0%, protein ≥ 3.0%, and containing biomass substrates such as phospholipids, minerals, and vitamins. Then, 1000 kg of the qualified soapstock is weighed and pumped into a 3 m 3 aerobic hydrolysis acidification tank A, and temperature-controlled biological fermentation is carried out. The water bath is heated to control the temperature at 30 - 33 °C and stirring is started. Secondly, 10 kg of acetic acid bacteria accounting for 1.0% of the weight of the soapstock and 20 kg of methanobacterium strains accounting for 2.0% are weighed. 60 kg of deionized water twice their weight is used to mix them into a paste and then added to the fermentation tank 3 m 3 A. After constant temperature, sterile air is introduced, and the ventilation volume accounts for 25% of the volume of the mixed materials, and the air pressure is not less than 1.5 kg / cm 2 . Under the conditions of temperature control, aerobic, and stirring, biological fermentation is carried out for 24 h. The upper oil sample is taken and the acid value is measured as 160 mg KOH / g and the saponification value is 195 mg KOH / g. The biological hydrolysis coupling reaction is continued until 48 h. The oil sample is taken and the acid value is measured as 190 mg KOH / g and the saponification value is 195 mg KOH / g. Stop ventilation and stirring, and let it stand for 90 minutes to separate layers. The lower water layer (heavy phase) containing rich organic carbon sources and microorganisms is discharged into an anaerobic fermentation tank 2 m 3 B tank, and the upper oil phase (crude fatty acids) is discharged into a 1 m 3 C tank. The fermentation tank B is heated to control the temperature at 40 - 45 °C, and stirring is started to promote heat exchange and uniform mass transfer. 30 - 40 m 3 of biogas is produced by anaerobic fermentation. When no gas is produced, the anaerobic fermentation tank is heated to 100 °C and maintained for 10 min, and then cooled to 40 °C. After centrifugal separation, 16.6 kg of oil layer, 300 kg of water, and 30 kg of residue (organic fertilizer) are obtained. The crude fatty acids obtained by combining the C tank and the centrifuged oil layer total 416.6 kg, and 395.8 kg of fatty acid finished products are obtained by rectification, with a yield of more than 95.0%.

[0033] Example 2

[0034] In a method for preparing fatty acids and co-producing biogas from soapstock by biological hydrolysis coupling in this example, soapstock of the same mass as in Example 1 is weighed. 20 kg of acetic acid bacteria accounting for 2.0% of the weight of the soapstock and 40 kg of methanobacterium strains accounting for 4.0% are used. 120 kg of deionized water twice their weight is used to mix them into a paste and then added to the fermentation tank 3 m 3 A together with 1000 kg of the soapstock. After constant temperature (30 - 33 °C), sterile air is introduced, and the ventilation volume accounts for 25% of the volume of the mixed materials, and the air pressure is not less than 1.5 kg / cm 2Under the conditions of temperature control, aerobic, and stirring, conduct biological fermentation for 24 hours. Take the upper oil sample, and test the acid value to be 190 mg KOH / g and the saponification value to be 195 mg KOH / g. The crude fatty acid is qualified. Stop aeration and stirring, and let it stand for 90 minutes to separate layers. Drain the lower water layer (heavy phase) containing rich organic carbon sources and microorganisms into the anaerobic fermentation tank 2 m 3 Tank B, and drain the upper oil phase (crude fatty acid) into 1 m 3 Tank C. Heat and control the temperature of fermentation tank B at 40 - 45 °C, turn on the stirring to promote heat exchange and uniform mass transfer. Anaerobic fermentation produces 30 - 40 m 3 of biogas. When no gas is produced, raise the temperature of the anaerobic fermentation tank to 100 °C and maintain it for 10 minutes, then cool it to 40 °C. After centrifugal separation, 360 kg of water and 80 kg of residue (organic fertilizer) are obtained. Dry the oil layer in tank C to obtain a total of 430 kg of crude fatty acid, and through rectification, 416.3 kg of fatty acid finished product is obtained, with a yield greater than 96.8%.

[0035] Example 3

[0036] For a method of hydrolyzing soapstock by biological method and coupling to produce fatty acids and co-producing biogas in this example, weigh the same mass of soapstock as in Example 1, 20 kg of Acetobacter (accounting for 2.0% of the weight of soapstock) and 40 kg of Methanobacterium strain (accounting for 4.0% of the weight of soapstock). Mix them with 120 kg of deionized water, which is twice their weight, into a paste. Then add 1000 kg of soapstock and add them to fermentation tank 3 m 3 A. After maintaining a constant temperature (30 - 33 °C), do not introduce air. Conduct biological fermentation for 24 hours under the conditions of temperature control, anaerobic, and stirring. Take the upper oil sample, and test the acid value to be 100 mg KOH / g and the saponification value to be 195 mg KOH / g. Then extend the fermentation time to 48 hours, take the upper oil sample, and test the acid value to be 100 mg KOH / g and the saponification value to be 195 mg KOH / g, which proves that no acidification and coupling reaction occur during the extended time. Let it stand for 90 minutes to separate layers. Drain the lower water layer (heavy phase) containing rich organic carbon sources and microorganisms into the anaerobic fermentation tank 2 m 3 Tank B, and drain the upper oil phase (crude fatty acid) into 1 m 3 Tank C. Heat and control the temperature of fermentation tank B at 40 - 45 °C, turn on the stirring to promote heat exchange and uniform mass transfer. Anaerobic fermentation produces 15 - 20 m 3 of biogas. When no gas is produced, raise the temperature of the anaerobic fermentation tank to 100 °C and maintain it for 10 minutes, then cool it to 40 °C. After centrifugal separation, 390 kg of water and 100 kg of residue (organic fertilizer) are obtained. Dry the oil layer in tank C to obtain a total of 400.0 kg of crude fatty acid, and through rectification, 188.8 kg of fatty acid finished product is obtained, with a yield greater than 47.2%.

[0037] Example 4

[0038] A method for hydrolyzing soapstock by biological method and coupling it with the production of fatty acids and biogas, weighing the same mass of soapstock as in Example 1, 30 kg of Acetobacter (accounting for 3.0% of the weight of soapstock) and 50 kg of Methanobacterium strain (accounting for 5.0% of the weight of soapstock), adding 160 kg of deionized water which is twice their weight, mixing into a paste, and then adding 1000 kg of soapstock into the fermentation tank 3m 3 A. After maintaining a constant temperature (30 - 33 °C), sterile air is introduced, and the ventilation volume accounts for 25% of the volume of the mixed materials, with the air pressure not less than 1.5 kg / cm 2 . Under the conditions of temperature control, aerobic, and stirring, biological fermentation is carried out for 24 h. The upper oil sample is taken, and the acid value is tested to be 190 mg KOH / g and the saponification value is 190 mg KOH / g. When the crude fatty acids are qualified, the ventilation and stirring are stopped, and it is allowed to stand and separate for 90 minutes. The lower water layer (heavy phase) containing rich organic carbon sources and microorganisms is discharged into the anaerobic fermentation tank 2m 3 B, and the upper oil phase (crude fatty acids) is discharged into 1m 3 C. The fermentation tank B is heated to maintain a temperature of 40 - 45 °C, and stirring is started to promote heat exchange and uniform mass transfer. Anaerobic fermentation produces 30 - 40m 3 of biogas. When no gas is produced, the anaerobic fermentation tank is heated to 100 °C and maintained for 10 min, and then cooled to 40 °C. After centrifugal separation, 450 kg of water and 130 kg of residue (organic fertilizer) are obtained. The oil layer in tank C is dried (dehydrated) to obtain a total of 415.6 kg of crude fatty acids, and 399.4 kg of fatty acid products are obtained by rectification, with a yield greater than 96.1%.

[0039] Example 5

[0040] A method for hydrolyzing soapstock by biological method and coupling it with the production of fatty acids and biogas, weighing the same mass of soapstock as in Example 1, 20 kg of Acetobacter (accounting for 2.0% of the weight of soapstock) and 40 kg of Methanobacterium strain (accounting for 4.0% of the weight of soapstock), adding 120 kg of deionized water which is twice their weight, mixing into a paste, and then adding 1000 kg of soapstock into the fermentation tank 3m 3 A. After maintaining a constant temperature (25 - 30 °C), sterile air is introduced, and the ventilation volume accounts for 25% of the volume of the mixed materials, with the air pressure not less than 1.5 kg / cm 2 . Under the conditions of temperature control, aerobic, and stirring, biological fermentation is carried out for 24 h. The upper oil sample is taken, and the acid value is tested to be 170 mg KOH / g and the saponification value is 195 mg KOH / g. The biological hydrolysis coupling reaction is continued until 36 h, and then the sample is taken again for testing. The acid value is 190 mg KOH / g and the saponification value is 195 mg KOH / g. When the crude fatty acids are qualified, the ventilation and stirring are stopped, and it is allowed to stand and separate for 90 minutes. The lower water layer (heavy phase) containing rich organic carbon sources and microorganisms is discharged into the anaerobic fermentation tank 2m 3 B, and the upper oil phase (crude fatty acids) is discharged into 1m 3For Tank C, heat Fermentation Tank B to 40 - 45°C and control the temperature, start stirring to promote heat exchange and uniform mass transfer, and anaerobically ferment to produce 30 - 40 m 3 of biogas. When no gas is produced, raise the temperature of the anaerobic fermentation tank to 100°C and maintain for 10 minutes, then cool to 40°C and obtain 400 kg of water and 110 kg of residue (organic fertilizer) by centrifugation. The oil layer in Tank C is dried to obtain a total of 408.1 kg of crude fatty acids, and 380.8 kg of fatty acid products are obtained by rectification, with a yield of more than 93.3%.

[0041] Example 6

[0042] For the method of hydrolyzing soapstock by biological method and coupling to prepare fatty acids and co-producing biogas in this example, first detect the soapstock: no pathogenic bacteria, acid value 70 mg KOH / g after acidification, saponification value 195 mg KOH / g, sugar and starch ≥ 5.0%, protein ≥ 3.0%, and containing biomass matrices such as phospholipids, minerals, and vitamins. Then, weigh 1000 kg of the qualified soapstock detected and pump it into a 3 m 3 aerobic hydrolysis acidification tank A, control the temperature for biological fermentation, heat by water bath to 30 - 33°C and start stirring; do not add any microorganisms, after constant temperature, introduce sterile air, and the ventilation volume accounts for 25% of the volume of the mixed materials, and the air pressure is not less than 1.5 kg / cm 2 . Ferment for 24 h under the conditions of temperature control, oxygen supply, and stirring. It is found that the appearance of the soapstock in Tank A has not changed. Sampling and acidification tests show that the acid and saponification values are the same as those of the raw materials, and no hydrolysis reaction has occurred. At the same time, the water layer cannot be separated, and the next step cannot be carried out.

[0043] The above are only some embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for hydrolytic coupling of soapstock by biological method to produce fatty acids and simultaneously produce biogas, characterized in that Including the following steps: Step 1: Mix the materials. The temperature-controlled and aerobic fermentation is completed in Tank A. The materials include 100 parts by weight of soapstock, acetic acid bacteria, methanogenic bacteria, and water. Stir and control the temperature at 20 - 60°C, and introduce sterile air for aerobic fermentation. The ventilation volume accounts for 25 - 50% of the volume of the mixed materials, and the air pressure is not less than 1.5 kg / cm 2 ; Ferment for 24 - 48 hours to complete the acidification of the soapstock and simultaneously couple the hydrolysis of oil by lipase. The crude fatty acid generated floats on the upper layer due to the density difference with water. Drain the water layer rich in organic matter into Fermentation Tank B and the oil layer into Tank C; Step 2: The water layer rich in organic matter enters fermentation tank B, and the temperature is raised to 40 - 68°C. It is converted from the aerobic section in Step 1 to anaerobic fermentation. Under anaerobic conditions, the methanobacterium community starts to construct and produce synthetic enhancement in the anaerobic strain cell factory, and the phosphorylation kinase produces multi-dimensional cooperative regulation of the anaerobic strain, so that the fermented liquid separated from the oil layer is converted into biogas methane (CH4). After the gas production ends, the temperature of the fermented liquid is raised to 70 - 100°C, and the microorganisms are denatured and inactivated. After centrifugation, the solid phase, oil phase, and water phase are separated. The solid phase and water phase are used for ecological organic fertilizer, and the oil phase is merged into the crude fatty acid tank C; Step 3: The crude fatty acid prepared by the saponification waste biological hydrolysis coupling is dehydrated and dried by heating in tank C, and then refined to obtain the finished fatty acid.

2. The method for hydrolytic coupling preparation of fatty acids and co-production of biogas by using soapstock through biological method according to claim 1, characterized in that The saponification waste should meet the following requirements: no pathogenic bacteria, acid value above 70mgKOH / g after acidification, saponification value 195mgKOH / g, sugar and starch ≥8.0%, protein ≥3.0%, and containing phospholipids, minerals, and vitamin biomass substrates.

3. A method for hydrolytic coupling of soapstock by biological method to co-produce fatty acids and biogas, as claimed in claim 1, wherein Add acetic acid bacteria accounting for 0.8% - 3.0% of the weight of the saponification waste; methanobacterium strains accounting for 1.0% - 5.0% of the weight of the saponification waste.

4. A method for hydrolytic coupling of soapstock by biological method to co-produce fatty acids and biomethane according to claim 1, characterized in that, Before introducing sterile air, control the pH of the soap base to 6 - 8.

5. A method for hydrolytic coupling of soapstock by biological method to jointly produce fatty acids and biogas, as claimed in claim 1, wherein, The addition amount of water is twice the weight of the microorganisms.

6. A method for hydrolytic coupling of soapstock by biological method to produce fatty acids and co - produce biogas, as claimed in claim 1, wherein When the mixture of saponification waste undergoes aerobic fermentation, the organic acids produced include one or more of acetic acid, propionic acid, butyric acid, glycolic acid, and pyruvic acid, which neutralize or acidify the sodium or potassium fatty acid in the saponification waste to generate fatty acids; at the same time, the lipase produced by microbial metabolism couples with the hydrolysis of triglycerides to produce fatty acids and glycerol, and glycerol can be used as an organic carbon source; after the mixture undergoes aerobic fermentation, the fatty acid oil phase and the mixed water phase containing water-soluble organic carbon source will be stratified due to the density difference.

7. A method for hydrolytic coupling of soapstock by biological method to co-produce fatty acids and biogas, as claimed in claim 1, wherein In Step 2, the water layer rich in organic carbon source undergoes anaerobic fermentation to produce biogas methane (CH4); the organic carbon source includes organic acids, organic salts, proteins, glycerol, and carbohydrates.

8. A method for hydrolytic coupling of soapstock by biological method to co-produce fatty acids and biogas, as claimed in claim 1, wherein In Step 3, the crude fatty acid prepared by the saponification waste biological hydrolysis coupling is gathered together, dehydrated and dried by heating, and then refined to obtain the finished fatty acid, and the highest yield reaches 96.8%.

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