A method for synchronously producing yeast protein and ethanol by fungal proliferation fermentation of kitchen waste

Abstract

The application discloses a kind of kitchen garbage fungus proliferation fermentation synchronous production yeast protein and ethanol method, comprising the following steps: S1, kitchen garbage is screened and slurried, and kitchen garbage slurry is obtained;S2, after adjusting solid-liquid ratio, kitchen garbage slurry is carried out warm pre-treatment;S3, after warm pre-treatment, kitchen garbage is centrifuged, and three-phase separation recovers grease, supernatant and solid residue;S4, the supernatant is carried out fungus fermentation synchronous co-production yeast protein and ethanol, and after fungus fermentation, yeast protein and ethanol are recovered respectively;The grease is prepared biomass-based liquid fuel, and the solid residue is prepared dispersed porous carbon material, and the fermentation temperature in the fungus fermentation process is 20~35 ℃, and fermentation time is 3~7 days.By controlling fungus fermentation process, kitchen garbage supernatant fungus fermentation synchronous production yeast protein and ethanol can be realized, and the additional value of kitchen garbage resource is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment and resource utilization, specifically relating to a method for the simultaneous production of yeast protein and ethanol through fungal proliferation and fermentation of kitchen waste. Background Technology

[0002] With the orderly implementation of household waste sorting policies, the amount of effectively recycled kitchen waste is constantly increasing. Kitchen waste in my country is characterized by high moisture content, complex composition, and susceptibility to decomposition, making it a heavy burden on urban environmental management. Therefore, effective disposal of kitchen waste is urgently needed, and its resource utilization is the fundamental solution.

[0003] Food waste is mainly composed of polysaccharides, proteins, lipids, and fibrous substances, with extremely rich organic matter content, containing huge potential and abundant resources. Currently, the main resource utilization path for food waste is to extract oil through heat conditioning and then perform anaerobic fermentation to produce biogas. However, anaerobic fermentation of food waste has the following disadvantages: (1) Heat conditioning of food waste does not completely extract oil, and oil easily inhibits the fermentation system during anaerobic fermentation; (2) Food waste is easily putrefied and acidified, resulting in a low pH of the fermentation system, which inhibits the activity of methanogenic bacteria in anaerobic fermentation; (3) The solid-liquid co-fermentation time after heat conditioning of food waste is relatively long, resulting in low fermentation efficiency; (4) During the fermentation of food waste, protein degradation easily leads to excessive ammonia nitrogen, which inhibits the fermentation activity of bacteria; (5) In the long run, the market price of biogas is low and it is a greenhouse gas that requires additional attention. Therefore, how to overcome the drawbacks of anaerobic fermentation of food waste and develop new and efficient treatment and resource utilization technologies for food waste is still a problem worthy of attention. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a method for the simultaneous production of yeast protein and ethanol through fungal proliferation and fermentation of kitchen waste, which enables the effective resource utilization of kitchen waste.

[0005] This invention provides a method for simultaneously producing yeast protein and ethanol through fungal fermentation of kitchen waste, comprising the following steps: S1. Screen and pulp the kitchen waste to obtain kitchen waste slurry; S2. After adjusting the solid-liquid ratio of the kitchen waste slurry, it is subjected to heat pretreatment. S3. After the pre-treatment of the kitchen waste is heated, centrifuge it to separate and recover the grease, supernatant and solid residue in three phases. S4. The supernatant is subjected to fungal fermentation to simultaneously produce yeast protein and ethanol. After the fungal fermentation is completed, the yeast protein and ethanol are recovered respectively. The oil is used to prepare biomass-based liquid fuel, and the solid residue is used to prepare dispersed porous carbon material. In step S2, the solid-liquid ratio is 1:10 to 2:10, the temperature of the thermal pretreatment is 100 to 160 ºC, and the treatment time is 1.0 to 2.0 h; the thermal pretreatment is carried out under stirring at a speed of 200 to 400 rpm. The fungi include yeasts capable of fermenting to produce ethanol; In step S4, the temperature during the fungal fermentation of the supernatant from the kitchen waste is 20–35 ºC, and the time is 3–7 days.

[0006] According to a preferred embodiment of the present invention, at least the following beneficial effects are achieved: The present invention provides a method for the simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste. After screening and pulping the kitchen waste, a warm pretreatment can promote the depolymerization of macromolecular organic matter and improve its bioavailability. Simultaneously, using a higher warm pretreatment temperature than heat conditioning further improves the separation effect of oils. The warm pretreated kitchen waste undergoes three-phase separation to obtain oils, supernatant, and solid residue, achieving the phased and fractional resource utilization of kitchen waste. Using the kitchen waste supernatant for fungal fermentation (rather than solid-liquid mixed fermentation) can improve bioconversion efficiency. Simultaneously, using fungal fermentation to co-produce yeast protein and ethanol can overcome the adverse effects of low pH and high ammonia nitrogen concentration on bioconversion. By controlling the fungal fermentation process, the simultaneous production of yeast protein and ethanol from the kitchen waste supernatant through fungal fermentation can be achieved, significantly increasing the added value of kitchen waste resource utilization. Using the present invention, the oil recovery rate can reach over 75%, and the COD concentration of the supernatant is typically between 85 and 95 g / L.

[0007] According to some embodiments of the present invention, fermentation includes an early fermentation phase and a late fermentation phase. In the early fermentation phase, shaking culture is used to promote yeast proliferation at a rotation speed of 100–180 rpm. In the late fermentation phase, the yeast is shaken to metabolize and produce ethanol at a rotation speed of 20–100 rpm. The early fermentation phase is the logarithmic growth phase of the yeast, and the late fermentation phase refers to the stable growth phase of the yeast. Alternatively, only the early fermentation phase may be performed.

[0008] According to some embodiments of the present invention, the fermentation is carried out under aerobic conditions in the early stage and under facultative aerobic conditions in the later stage.

[0009] According to some embodiments of the present invention, the yeast capable of fermenting to produce ethanol includes at least one of *Candida tropicalis*, *Saccharomyces cerevisiae*, *Pichia pastoris*, *Candida ludwigii*, and *Candida rhodesii*. The present invention overcomes the inhibition of biological fermentation by the easy acidification and high ammonia nitrogen content of kitchen waste, achieving rapid organic matter conversion and yeast proliferation through fungal fermentation and the selection of suitable strains.

[0010] According to some embodiments of the present invention, in step S1, the screening and pulping includes the following steps: food waste is screened to remove impurities, and then subjected to high-speed mechanical pulping for 10 to 30 minutes, wherein the high speed refers to a rotation speed of 20,000 to 30,000 rpm, to obtain food waste pulp; wherein the impurities include at least one of plastic, metal or bone.

[0011] According to some embodiments of the present invention, the particle size of the kitchen waste slurry is less than 200 μm.

[0012] According to some embodiments of the present invention, the temperature of the thermal pretreatment is 100~120 ºC.

[0013] According to some embodiments of the present invention, in step S2, the solid-liquid ratio is adjusted by adding water for dilution.

[0014] According to some embodiments of the present invention, in step S3, the pretreated kitchen waste is subjected to three-phase separation by mechanical centrifugation without the addition of any reagents. The centrifugation speed is 8000-12000 rpm and the centrifugation time is 10-15 min. After centrifugation, the grease, supernatant and remaining solid residue are recovered respectively.

[0015] According to some embodiments of the present invention, in step S4, the supernatant of the pretreated kitchen waste is sterilized and then subjected to fungal fermentation.

[0016] According to some embodiments of the present invention, in step S4, yeast particles are recovered by centrifugation (preferably at a speed of 8000-12000 rpm for 5-15 min) or vacuum filtration (preferably with a filter membrane pore size of less than 0.5 μm), and ethanol is recovered by distillation.

[0017] According to some embodiments of the present invention, in step S4, while recovering yeast particles and ethanol, a secondary recovery is also performed on the primary fermentation filtrate of kitchen waste after fungal fermentation. Kitchen waste that has undergone heat pretreatment produces a higher content of yeast protein during secondary fermentation, significantly increasing the total yeast protein yield. Furthermore, this secondary recycling allows for greater utilization of the organic matter in the kitchen waste, increasing the economic benefits of recycling and further reducing its environmental pollution.

[0018] According to some embodiments of the present invention, the remaining primary fermentation filtrate of kitchen waste can be sterilized and then subjected to fungal fermentation for 3-5 days. After fungal fermentation, yeast protein and ethanol are recovered again until the utilization rate of organic matter in the supernatant of kitchen waste exceeds 80%. The remaining secondary fermentation filtrate is used for anaerobic fermentation to produce methane or as a carbon source for denitrification in sewage treatment plants.

[0019] According to some embodiments of the present invention, the yeast particles recovered in step S4 are subjected to ultrasonic extraction to extract their proteins. This method can simultaneously produce yeast protein and fuel ethanol, and can easily and quickly recover yeast protein with high purity.

[0020] According to some embodiments of the present invention, step S4 further includes processing the recovered yeast protein into edible nutritional protein powder or using it directly as an animal feed additive.

[0021] According to some embodiments of the present invention, the recovered oil is used to prepare biodiesel by esterification with alcohols, or to prepare biomass-based liquid fuel by catalytic upgrading and deoxygenation hydrorefining.

[0022] According to some embodiments of the present invention, the solid residue is dried and then subjected to pyrolysis and activation treatment to prepare a dispersed porous carbon material.

[0023] According to some embodiments of the present invention, the pyrolysis is pyrolysis carbonization at 600~1000 ºC under a protective atmosphere.

[0024] According to some preferred embodiments of the present invention, the pyrolysis is pyrolysis carbonization at 800 °C under a protective atmosphere.

[0025] According to some embodiments of the present invention, the protective atmosphere is nitrogen or an inert atmosphere.

[0026] According to some embodiments of the present invention, the activation is performed by ultrasonic treatment in potassium hydroxide solution followed by activation at 800~1000 ºC.

[0027] According to some preferred embodiments of the present invention, the activation is performed by ultrasonic treatment in a potassium hydroxide solution with a mass fraction of 5%-20% for 1-2 hours, followed by drying and activation, and then washing with hydrochloric acid and water until the pH is neutral before drying to obtain porous carbon material.

[0028] According to some preferred embodiments of the present invention, the drying temperature is 100~110ºC; more preferably, the drying temperature is 105ºC.

[0029] This invention enables the recovery of yeast protein for use as feed in the livestock and poultry farming industry, where there is a strong demand for yeast protein. The invention also allows for the simultaneous recovery of ethanol for use as an industrial raw material or fuel, and the recovery of three-phase separated oils for upgrading and production of diesel and other fuels. This invention has promising industrial application prospects, and its recycling process can increase the added value of food waste treatment. This invention replaces traditional anaerobic fermentation technology for food waste, achieving a next-generation upgrade in the resource utilization of food waste. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of the operation process of Embodiment 1 of the present invention; Figure 2 The graph shows the analysis results of peak molecular weight in Examples 1-2 (corresponding to 105 ºC and 120 ºC respectively), Comparative Example 1 (90 ºC), and kitchen waste (original kitchen waste) before fermentation. Detailed Implementation

[0031] The following will describe the concept and technical effects of the present invention clearly and completely with reference to the embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available.

[0032] Example 1 This embodiment describes a method for the simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste. Figure 1 The specific process is as shown: S1. The kitchen waste taken from the campus restaurant is screened and pulped (the kitchen waste is screened to remove impurities such as plastic, metal, and bone, and mechanically pulped at 20,000 rpm for 10 minutes) to obtain kitchen waste slurry (particle size less than 200 μm). S2. Dilute with water to a solid-liquid ratio of approximately 1.5:10, and then perform a warm pretreatment at a temperature of 105 ºC for 1 h with a stirring speed of 200 rpm.

[0033] S3. After heat pretreatment, the kitchen waste is centrifuged to separate the three phases at a speed of 12,000 rpm for 10 min. The grease and supernatant (COD 86 g / L) are recovered by suction, and the remaining solid residue is collected.

[0034] S4. After aseptic treatment of the supernatant, inoculate with a 5 wt% suspension of activated Candida tropicalis (commercially available) (the yeast concentration in the suspension is approximately 0.2 g dry weight / L) for fungal fermentation. Fermentation is carried out at 28 ºC with shaking at 150 rpm for 5 days. Yeast particles are recovered by centrifugation (8000 rpm, 10 min), and ethanol is recovered by distillation. The recovered yeast particles are then sonicated (450 W, 15 min) to extract protein.

[0035] The oil is catalytically upgraded and then hydrodeoxygenated using molecular sieve catalysts to produce olefin-rich liquid fuels.

[0036] The collected solid residue was dried at 105 ºC and then pyrolyzed and carbonized at 800 ºC for 2 h under a nitrogen atmosphere at a rate of 5 ºC / min to obtain carbon material derived from food waste. Tar was removed by rinsing with ethanol, followed by ultrasonic treatment (350 W) with 5% KOH solution for 1 h, and then activation at 800 ºC for 0.5 h (heating rate 20 ºC / min). The material was then washed with 1 wt% dilute hydrochloric acid and deionized water until neutral to obtain porous carbon material.

[0037] Example 2 This embodiment describes a method for the simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste. The difference between this method and Example 1 is that the pretreatment temperature is 120 ºC, and the COD concentration of the supernatant is 92 g / L.

[0038] Example 3 This embodiment describes a method for simultaneously producing yeast protein and ethanol through fungal fermentation of kitchen waste. The remaining kitchen waste fermentation liquid (COD 56 g / L, containing undistilled ethanol) after the first recovery of yeast protein and ethanol in Example 1 is sterilized again, and then inoculated with tropical filamentous yeast suspension for fungal fermentation. The yeast protein and ethanol are recovered according to the same steps as in Example 1.

[0039] Example 4 This embodiment describes a method for simultaneously producing yeast protein and ethanol through fungal fermentation of kitchen waste. The remaining kitchen waste fermentation liquid (COD 53 g / L, containing undistilled ethanol) after the first recovery of yeast protein and ethanol in Example 2 is sterilized again, and then inoculated with tropical filamentous yeast suspension for fungal fermentation. The yeast protein and ethanol are recovered according to the same steps as in Example 1.

[0040] Example 5 This embodiment is a method for simultaneously producing yeast protein and ethanol through fungal fermentation of kitchen waste. The difference between this method and Embodiment 1 is that the fermentation time is 3 days.

[0041] Comparative Example 1 This comparative example is a method for the simultaneous production of yeast protein and ethanol through fungal proliferation and fermentation of kitchen waste. The difference between this method and Example 1 is that the pretreatment temperature is 90 ºC and the COD of the supernatant is 86 g / L.

[0042] Comparative Example 2 This comparative example is a method for the simultaneous production of yeast protein and ethanol through fungal proliferation and fermentation of kitchen waste. The difference between this method and Example 3 is that the fermentation raw material is the fermentation liquid obtained after fermentation of Comparative Example 1 and recovery using the same operation as in Example 3.

[0043] Comparative Example 3 This comparative example is a method for the simultaneous production of yeast protein and ethanol through fungal proliferation and fermentation of kitchen waste. The difference from Example 1 is that no heat pretreatment is performed.

[0044] Comparative Example 4 This comparative example is a method for the simultaneous production of yeast protein and ethanol through fungal proliferation and fermentation of kitchen waste. The difference between this method and Example 3 is that the fermentation raw material is the fermentation liquid obtained after fermentation in Comparative Example 3 and recovery using the same operation as in Example 3.

[0045] Comparative Example 5 This comparative example is a method for the simultaneous production of yeast protein and ethanol through fungal proliferation and fermentation of kitchen waste. The difference between this method and Example 1 is that the fermentation time is 1.5 days.

[0046] Test case 1) Oil recovery rate and COD concentration of supernatant The oil recovery rate in Example 1 was 76.5%, and the COD concentration of the supernatant was 86 g / L; the oil recovery rate in Example 2 was 81.8%, and the COD concentration of the supernatant was 92 g / L; the recovery rate in Comparative Example 1 was 72.4%, and the COD concentration of the supernatant was 86 g / L. The oil recovery rate further increased with increasing pretreatment temperature.

[0047] 2) Yeast protein biomass and ethanol concentration The amounts of recovered yeast protein and ethanol were measured, and the yeast protein biomass and ethanol concentration recovered per liter of kitchen waste were calculated, as shown in Table 1 below: Table 1

[0048] As shown in the table above, extending the fermentation time to more than 3 days significantly increases the yield of yeast protein. In a single fermentation, the yeast protein content after pretreatment at 105ºC is comparable to that after pretreatment at 90ºC. However, considering Examples 3 and 2, the total amount of yeast protein produced in two fermentations at 105ºC is far higher than that after pretreatment at 90ºC. Pretreatment has a significant impact on the total amount of fermented yeast protein recovered.

[0049] 3) Determine the specific surface area and particle size of porous carbon materials. The specific surface area (BET nitrogen adsorption-desorption method) of the carbon materials prepared in Examples 1-5 all exceeded 800 m². 2 / g, indicating that the porous material recovered by the present invention can be used as an adsorbent or electrode material. Furthermore, the porous carbon material prepared by pyrolysis of kitchen waste solid residue after hot water pretreatment has an average particle size that is more than 10% smaller than that prepared from slurry-like kitchen waste solid residue without hot water pretreatment, exhibiting better dispersibility.

[0050] 4) Determine the molecular weight of the supernatant The molecular weight of the supernatant before fermentation was analyzed by GPC. The peak molecular weight analysis results of Examples 1-2, Comparative Example 1, and the kitchen waste before fermentation are as follows: Figure 2 As shown (the results of Comparative Example 3 are basically consistent with those of Comparative Example 1, and are not shown in the figure). From Figure 2 It can be seen that the peak molecular weights of Examples 1 and 2 are about 100 Da lower than those of Comparative Examples 1 and 3, respectively. This indicates that the pretreatment conditions of the present invention improve the biodegradability of the supernatant of kitchen waste and have an important impact on the depolymerization of macromolecular organic matter in kitchen waste. 5) COD removal rate of supernatant After two fermentations, the cumulative COD removal rates in Examples 3 and 4 reached 54% and 62%, respectively. As can be seen from Table 1, the warm pretreatment conditions of the present invention not only resulted in higher yeast protein production but also higher organic matter removal efficiency, indicating that the supernatant has better biodegradability.

[0051] This scheme, when fermenting to co-produce yeast protein and ethanol, mainly uses hot hydrolysis to pre-treat kitchen waste to improve its biochemical properties. After hot hydrolysis pre-treatment, the products are separated into three phases. Only the supernatant of the liquid product is inoculated with pure bacteria (such as yeast) for fungal fermentation to simultaneously produce yeast protein and ethanol. After fermentation, fuel ethanol and high-quality, high-purity single-cell yeast protein can be recovered separately, which has high product added value and can bring high returns to the implementing company.

[0052] In addition to using fungal fermentation to recover yeast protein, this invention also recovers ethanol simultaneously during fungal fermentation by selecting superior strains and regulating the fermentation process. Furthermore, the use of thermal pretreatment and three-phase separation to pretreat kitchen waste can significantly improve the quality of the liquid matrix, which is beneficial for subsequent fungal fermentation. It eliminates the need for anaerobic digestion to produce acid before inoculating fungi for fermentation, and also eliminates the need to actively control the pH and ammonia nitrogen concentration of the fermentation liquid to achieve high yeast protein value-added, thus providing greater operational flexibility.

[0053] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

Claims

1. A method for simultaneously producing yeast protein and ethanol through fungal fermentation of kitchen waste, characterized in that: Includes the following steps: S1. Screen and pulp the kitchen waste to obtain kitchen waste slurry; S2. After adjusting the solid-liquid ratio of the kitchen waste slurry, it is subjected to heat pretreatment. S3. After the pre-treatment of the kitchen waste is heated, centrifuge it to separate and recover the grease, supernatant and solid residue in three phases. S4. The supernatant is subjected to fungal fermentation to simultaneously produce yeast protein and ethanol. After the fungal fermentation is completed, the yeast protein and ethanol are recovered respectively. The oil is used to prepare biomass-based liquid fuel. The solid residue is dried and then subjected to pyrolysis and activation treatment to prepare dispersed porous carbon material. In step S2, the solid-liquid ratio is 1:10 to 2:10, the temperature of the thermal pretreatment is 100 to 160 ºC, and the treatment time is 1.0 to 2.0 h; the thermal pretreatment is carried out under stirring at a speed of 200 to 400 rpm. The fungi include yeasts capable of fermenting to produce ethanol; In step S4, the temperature during the fungal fermentation of the supernatant from the kitchen waste is 20–35 ºC, and the time is 3–7 days. The fungal fermentation includes an early fermentation stage and a late fermentation stage. In the early fermentation stage, shaking culture is used to promote yeast proliferation at a speed of 100-180 rpm. In the late fermentation stage, the yeast is fermented and metabolized to produce ethanol at a speed of 20-100 rpm. The yeast strains capable of fermenting to produce ethanol include at least one of Candida tropicalis, Saccharomyces cerevisiae, Pichia pastoris, Candida ludwigii, and Candida russius. The pyrolysis is performed by carbonization at 600-1000 ºC under a protective atmosphere; the activation is performed by ultrasonic treatment in potassium hydroxide solution followed by activation at 800-1000 ºC.

2. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 1, characterized in that: In step S1, the screening and pulping includes the following steps: food waste is screened to remove impurities, and then subjected to high-speed mechanical pulping for 10 to 30 minutes, where high speed refers to a rotation speed of 20,000 to 30,000 rpm, to obtain food waste pulp; wherein, the impurities include at least one of plastic, metal or bone.

3. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 2, characterized in that: The particle size of the food waste slurry is less than 200 μm.

4. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 1, characterized in that: The temperature of the thermal pretreatment is 100~120 ºC.

5. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 1, characterized in that: In step S2, the solid-liquid ratio is adjusted by adding water to dilute the liquid.

6. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 1, characterized in that: In step S3, the pretreated kitchen waste is subjected to three-phase separation by mechanical centrifugation without the addition of any chemicals. The centrifugation speed is 8000-12000 rpm and the centrifugation time is 10-15 min. After centrifugation, the grease, supernatant and remaining solid residue are recovered respectively.

7. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 1, characterized in that: In step S4, the supernatant of the pretreated kitchen waste is sterilized and then subjected to fungal fermentation.

8. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 1, characterized in that: In step S4, yeast particles are recovered by centrifugation or vacuum filtration, and ethanol is recovered by distillation.

9. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 8, characterized in that: The centrifugation speed is 8000-12000 rpm, and the time is 5-15 min.

10. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 8, characterized in that: The filter membrane used in the vacuum filtration has a pore size of less than 0.5 μm.

11. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 8, characterized in that: In step S4, while recovering yeast particles and ethanol, the primary fermentation filtrate of kitchen waste after fungal fermentation is also recycled a second time. The remaining primary fermentation filtrate of kitchen waste can be sterilized and then fermented again for 3-5 days. After fungal fermentation, yeast protein and ethanol are recovered again until the utilization rate of organic matter in the supernatant of kitchen waste exceeds 80%. The remaining secondary fermentation filtrate is used for anaerobic fermentation to produce methane or as a carbon source for denitrification in sewage treatment plants.

12. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 8, characterized in that: In step S4, the protein in the recovered yeast particles is extracted using ultrasound.

13. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 1, characterized in that: Step S4 also includes the step of using the recovered yeast protein directly as an animal feed additive.

14. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 1, characterized in that: The recovered oils are used to produce biodiesel through esterification with alcohols, or to produce biomass-based liquid fuels through catalytic upgrading and refining.

15. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 1, characterized in that: The pyrolysis is performed by carbonization at 800 ºC under a protective atmosphere.

16. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 1, characterized in that: The protective atmosphere is an inert atmosphere.

17. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 1, characterized in that: The activation process involves ultrasonic treatment in a 5%-20% potassium hydroxide solution for 1-2 hours, followed by drying and activation. The material is then washed with hydrochloric acid and water until the pH is neutral before drying to obtain porous carbon material.

18. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 1, characterized in that: The drying temperature is 100~110ºC.

19. The method for simultaneous production of yeast protein and ethanol through fungal fermentation of kitchen waste according to claim 18, characterized in that: The drying temperature is 105 ºC.

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