Method for promoting anaerobic acid production of kitchen waste by using iron material

Abstract

The invention discloses a method for promoting anaerobic acid production of kitchen waste by using an iron material. The method comprises the following steps: S1, adding the kitchen waste into an anaerobic fermentation tank, and carrying out natural closed anaerobic fermentation; s2, inoculating an inoculum with the volume ratio of 10%-50% in a natural fermentation system of the kitchen waste, and adjusting the pH value in the anaerobic fermentation tank to be 3-5, so that the inoculum normally grows and generates organic acid or alcohol under the condition that the pH value is 3-5; s3, 0.1%-10% of ferric oxide is added into the anaerobic fermentation tank, natural fermentation is conducted for 7-14 days, the number of inoculums can be increased, the relative abundance of the inoculums is made to be larger than 70%, and the metabolic activity of the inoculums can be improved to be 5% or above. According to the invention, ferric oxide is taken as a catalyst, and growth of acid-producing functional microorganisms can be promoted, so that degradation of organic matters and generation of volatile fatty acid are accelerated, the overall acid-producing fermentation performance of the kitchen waste is improved, and the yield of volatile fatty acid in fermentation of the kitchen waste can be increased.

Description

Technical Field

[0001] The present application relates to the technical field of food waste treatment, and in particular to a method for promoting anaerobic acid production of food waste using iron materials. Background Art

[0002] At present, with the acceleration of urbanization, the amount of food waste generated is increasing year by year, posing new challenges to environmental management and resource recycling. Traditional food waste treatment methods such as landfill or incineration will cause potential secondary environmental pollution problems. In recent years, anaerobic digestion has gradually gained attention as a way to dispose of food waste resources. Organic waste is converted into biogas under anaerobic conditions to achieve energy recovery. The target products of traditional anaerobic digestion of food waste are mainly energy substances such as methane, but its fermentation cycle is long and the added value of the product is low. Studies have shown that volatile fatty acids (VFAs), as intermediate products of anaerobic fermentation of food waste, can be used as an organic carbon source for biological methods to remove pollutants in sewage treatment plants, and have the potential to replace fossil-based carbon sources.

[0003] However, in the anaerobic acid production process, the degradation rate of organic matter is often limited by the conditions of microbial activity, especially in the hydrolysis and acidification stages. The hydrolysis and acidification process is the key rate-limiting step in anaerobic acid production, and therefore determines the efficiency of the entire anaerobic acid production process of food waste. Studies have shown that adjusting pH, temperature control, and adding nutrients can effectively enhance the metabolic activity of functional microorganisms in the hydrolysis and acidification process, thereby improving the efficiency of anaerobic fermentation of food waste.

[0004] In the existing technology, the technology of adding additives to enhance anaerobic fermentation and acid production mainly focuses on three aspects: ① Adding chemical surfactants to increase the hydrolysis rate, reduce the activity of methanogens, and allow volatile fatty acids to accumulate; for example, in the patent document with publication number CN108504699A, a method of promoting the anaerobic fermentation of residual sludge to produce volatile acids by adding green surfactant alkyl polyglycoside APG60 is introduced. This method can effectively shorten the fermentation acid production time and obtain a higher volatile fatty acid yield.

[0005] ② Add exogenous substances to strengthen fermentation and block the methane production pathway; such as adding exogenous substances such as egg shells. In order to solve the problems that the pH decreases during the anaerobic fermentation of food waste to produce acid, inhibiting the activity of microorganisms, resulting in low volatile fatty acid yields and consuming volatile fatty acids during the methane production process, exogenous substances such as egg shells are added to strengthen the anaerobic fermentation of food waste to produce volatile fatty acids (CN111440831A), or bicarbonate is added to the initial stage of the fermentation system to produce acid through anaerobic fermentation and inhibit methane production (CN118460632A).

[0006] ③ Add biochar as a carrier or catalyst to increase the rate of acid production and fermentation and increase the content of volatile fatty acids. Add biochar. In order to improve the metabolic activity of functional microorganisms and the activity of related enzymes, existing studies have adopted the method of adding biochar to achieve the improvement of the volatile fatty acid production in the anaerobic fermentation process (CN118272458A, CN115725666A and CN118497292A). For example, CN118272458A introduces a method of using biochar loaded with zero-valent iron to immobilize microorganisms to promote anaerobic fermentation of sludge to produce medium-chain fatty acids. The invention uses biochar loaded with zero-valent iron as a microbial attachment carrier, electron mediator, microbial nutrient, and pH buffer and inhibitor mitigator in the fermentation process, and mixes it with the fermentation substrate sludge. Under the synergistic effect of biochar loaded with zero-valent iron, the anaerobic microorganisms in the sludge convert the remaining sludge into medium-chain fatty acids. Adding biochar loaded with zero-valent iron as a carrier can immobilize microorganisms and promote microbial colonization, thereby effectively increasing the yield of medium-chain fatty acids; achieving efficient resource utilization of the remaining sludge, and providing an economical, effective, simple and easy microbial immobilization method for the biological production of medium-chain fatty acids.

[0007] Among the many methods for enhancing acid production, adding additives to accelerate the hydrolysis and acidification process has become one of the research hotspots. Therefore, the present application provides a method for promoting anaerobic acid production of food waste by adding iron materials, so as to increase the yield of volatile fatty acids in food waste fermentation. Summary of the invention

[0008] The purpose of the present application is to provide a method for promoting anaerobic acid production of food waste by using iron materials. Ferric oxide is used as a catalyst and added to the anaerobic fermentation of food waste, which can promote the growth of acid-producing functional microorganisms, thereby accelerating the degradation of organic matter and the generation of volatile fatty acids, improving the overall acid production fermentation performance of food waste, and further increasing the yield of volatile fatty acids in the fermentation of food waste.

[0009] The present application provides a method for promoting anaerobic acid production from kitchen waste using iron materials, which adopts the following technical solution: A method for promoting anaerobic acid production of kitchen waste using an iron material, comprising the following steps: S1: Adding food waste into the anaerobic fermentation tank for natural closed anaerobic fermentation; S2: Then, in the natural fermentation system of food waste, the inoculum is inoculated with a volume ratio of 10%-50%, and the pH in the anaerobic fermentation tank is adjusted between 3-5, so that the inoculum can grow normally and produce organic acids or alcohols under the condition of pH 3-5; S3: Adding 0.1%-10% ferric oxide into the anaerobic fermentation tank and fermenting naturally for 7-14 days can increase the amount of inoculum, making the relative abundance of the inoculum greater than 70%, and can increase the metabolic activity of the inoculum by more than 5%.

[0010] Further, in step S2, the inoculum is rich in microorganisms of the phylum Firmicutes and Actinobacteria.

[0011] Furthermore, the TS of the inoculum should be between 3-10%, and the relative abundance of Firmicutes and Actinobacteria should be greater than 50%.

[0012] Furthermore, in step S3, the added ferric oxide should be in powder form with a particle size greater than 20 meshes.

[0013] Furthermore, during the entire fermentation process, the total solid TS of the fermentation liquid in the anaerobic fermentation tank is in the range of 5%-15%, and the VS / TS is in the range of 60%-95%.

[0014] Furthermore, the conductivity inside the anaerobic fermentation tank ranges from 10 mS / cm to 30 mS / cm.

[0015] Furthermore, the fermentation temperature inside the anaerobic fermentation tank ranges from 20°C to 40°C.

[0016] Furthermore, during the fermentation process, the gas produced by fermentation is mainly CO2, accounting for more than 70% of the total gas production.

[0017] Furthermore, during the fermentation process, the internal materials of the anaerobic fermentation tank need to be continuously stirred, and the stirring rate should be maintained at 10-40 revolutions per minute to ensure sufficient contact between the microorganisms and the fermentation substrate.

[0018] Further, in step S3, after 7-14 days of natural fermentation, the organic acid concentration inside the anaerobic fermentation tank reaches 10000-30000 mg / L, COD Cr The concentration should be greater than 30000mg / L.

[0019] Compared with the prior art, the beneficial effects of this application are: The scheme of the present application provides a method for anaerobic fermentation of food waste by adding ferric oxide to increase the yield of volatile fatty acids. Ferric oxide is used as a catalyst to be added to the anaerobic fermentation of food waste, which can promote the growth of acid-producing functional microorganisms, thereby accelerating the degradation of organic matter and the generation of volatile fatty acids, improving the overall acid-producing fermentation performance of food waste, and further increasing the yield of volatile fatty acids in the fermentation of food waste.

[0020] At the same time, by selecting ferric oxide, which is easily available and has good biocompatibility and catalytic activity, as the added material, the effect is obvious, the fermentation process is easy to control, the cost is low, and there is no secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the method of promoting anaerobic acid production of food waste by using iron materials in an embodiment of the present application. DETAILED DESCRIPTION

[0022] The following is combined with Figure 1 This application is described in further detail.

[0023] The present application discloses a method for promoting anaerobic acid production of kitchen waste using iron materials, referring to Figure 1 In this embodiment, the method includes the following steps: S1: Add food waste into the anaerobic fermentation tank for natural closed anaerobic fermentation.

[0024] S2: Then, in the natural fermentation system of food waste, an inoculum with a volume ratio of 10%-50% is inoculated; in step S2, the inoculum is microorganisms rich in Firmicutes and Actinobacteria, and the TS of the inoculum should be between 3-10%; wherein the relative abundance of the Firmicutes and Actinobacteria should be greater than 50%.

[0025] At the same time, the pH range in the anaerobic fermentation tank should be adjusted to between pH 3-5, so that the two microorganisms, Firmicutes and Actinobacteria, can grow normally and produce organic acids or alcohols under pH conditions of 3-5.

[0026] S3: Add 0.1%-10% of ferric oxide into the anaerobic fermentation tank; specifically, in step S3, the added ferric oxide should be in powder form, and the particle size should be larger than 20 meshes, so that the ferric oxide reacts more fully, which can further increase the concentration and yield of volatile fatty acids in the food waste during the anaerobic fermentation process.

[0027] Then let the fermentation in the anaerobic fermentation tank ferment naturally for 7-14 days; after 7-14 days of natural fermentation, the organic acid concentration in the anaerobic fermentation tank with added ferric oxide is 5%-40% higher than that in the control group without added ferric oxide, among which the organic acids are mainly acetic acid and propionic acid, accounting for more than 50%. Specifically, in step S3, after 7-14 days of natural fermentation, the fermentation environment inside the anaerobic fermentation tank is acidic, the pH range is between pH3-5, and the organic acid concentration inside the anaerobic fermentation tank is relatively high, reaching 10000-30000 mg / L; and the organic carbon source COD produced Cr The concentration should be greater than 30000mg / L.

[0028] In addition, during this process, adding 0.1%-10% ferric oxide at the beginning of fermentation can increase the number of two microorganisms, Firmicutes and Actinobacteria, so that the relative abundance of Firmicutes and Actinobacteria is greater than 70%.

[0029] At the same time, since ferric oxide is a trace element required by some key enzymes, it can increase the metabolic activity of these two microorganisms by more than 5%, thereby strengthening the metabolic activity of anaerobic acid-producing microorganisms. Specifically, ferric oxide (Fe2O3), as a common iron metal oxide material in nature, plays multiple roles in the anaerobic fermentation process. On the one hand, it dissolves in the ferric oxide anaerobic acid-producing fermentation system to form iron ions (Fe 3+ ), providing essential nutrients for the growth and reproduction of microorganisms. Iron ions are an important component of many enzymes, such as iron-sulfur proteins (Fe-S proteins). These proteins participate in redox reactions in cells and are essential for the energy metabolism of microorganisms. Therefore, adding ferric oxide is beneficial to enhancing enzyme activity, thereby promoting the growth and metabolism of functional microorganisms and enhancing their ability to decompose organic matter.

[0030] On the other hand, ferric oxide can act as an electron acceptor or donor and participate in the electron transfer process during anaerobic fermentation. Under anaerobic conditions, microorganisms can use ferric oxide as an electron acceptor to promote the degradation of organic matter. At the same time, ferric oxide can also indirectly affect the electron flow in the anaerobic fermentation system by promoting the activities of microorganisms such as sulfate-reducing bacteria, further increasing the production of VFA.

[0031] In addition, ferric oxide can also create a more stable anaerobic environment by regulating the redox potential (Eh) and pH value of the fermentation system. Appropriate Eh and pH values ​​help maintain the balance of the microbial community, promote the proliferation of hydrolytic acid-producing bacteria, and thus promote VFA accumulation. Therefore, ferric oxide was selected as an additive to increase the yield of volatile fatty acids in the fermentation of food waste.

[0032] Secondly, during the entire fermentation process, the fermentation conditions of the food waste in the anaerobic fermentation tank are as follows: During the entire fermentation process, the total solid TS range of the fermentation liquid in the anaerobic fermentation tank needs to be between 5%-15%, and the VS / TS range needs to be between 60%-95%; and the conductivity range inside the anaerobic fermentation tank needs to be between 10mS / cm-30mS / cm; such indicators are conducive to the growth of microorganisms.

[0033] At the same time, the fermentation temperature inside the anaerobic fermentation tank ranges from 20℃ to 40℃, which can provide a good growth temperature for the enriched microorganisms, thereby improving the activity of the microorganisms. In addition, during the fermentation process, the gas produced by the fermentation is mainly CO2, accounting for more than 70% of the total gas production; therefore, CO2 needs to be discharged and collected for treatment.

[0034] In addition, during the fermentation process, the internal materials of the anaerobic fermentation tank need to be continuously stirred, and the stirring rate should be maintained at 10-40 rpm to ensure sufficient contact between the microorganisms and the fermentation substrate.

[0035] Therefore, the scheme of the present application provides a method for anaerobic fermentation of food waste by adding ferric oxide to increase the production of volatile fatty acids. Ferric oxide is used as a catalyst and added to the anaerobic fermentation of food waste, which can promote the growth of acid-producing functional microorganisms, thereby accelerating the degradation of organic matter and the production of volatile fatty acids, improving the overall acid-producing fermentation performance of food waste, and thus increasing the production of volatile fatty acids in the fermentation of food waste.

[0036] At the same time, by selecting ferric oxide, which is easily available and has good biocompatibility and catalytic activity, as the added material, the effect is obvious, the fermentation process is easy to control, the cost is low, and there is no secondary pollution.

[0037] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for promoting anaerobic acid production from kitchen waste using iron materials, characterized in that: The following steps are involved: S1: Adding food waste into the anaerobic fermentation tank for natural closed anaerobic fermentation; S2: Then, in the natural fermentation system of food waste, the inoculum is inoculated with a volume ratio of 10%-50%, and the pH in the anaerobic fermentation tank is adjusted between 3-5, so that the inoculum can grow normally and produce organic acids or alcohols under the condition of pH 3-5; S3: Adding 0.1%-10% ferric oxide into the anaerobic fermentation tank and fermenting naturally for 7-14 days can increase the amount of inoculum, making the relative abundance of the inoculum greater than 70%, and can increase the metabolic activity of the inoculum by more than 5%.

2. The method for promoting anaerobic acid production from kitchen waste using iron materials according to claim 1, characterized in that: In step S2, the inoculum is rich in microorganisms of the phylum Firmicutes and Actinobacteria.

3. The method for promoting anaerobic acid production from kitchen waste using iron materials according to claim 2, characterized in that: The TS of the inoculum should be between 3-10%, and the relative abundance of Firmicutes and Actinobacteria should be greater than 50%.

4. The method for promoting anaerobic acid production from kitchen waste using iron materials according to claim 1, characterized in that: In step S3, the added ferric oxide should be in powder form with a particle size greater than 20 meshes.

5. The method for promoting anaerobic acid production from kitchen waste using iron materials according to claim 1, characterized in that: During the entire fermentation process, the total solid TS of the fermentation liquid in the anaerobic fermentation tank ranges from 5% to 15%, and the VS / TS ranges from 60% to 95%.

6. The method for promoting anaerobic acid production from kitchen waste using iron materials according to claim 5, characterized in that: The conductivity inside the anaerobic fermentation tank ranges from 10 mS / cm to 30 mS / cm.

7. The method for promoting anaerobic acid production from kitchen waste using iron materials according to claim 6, characterized in that: At the same time, the fermentation temperature inside the anaerobic fermentation tank ranges from 20°C to 40°C.

8. The method for promoting anaerobic acid production from kitchen waste using iron materials according to claim 7, characterized in that: During the fermentation process, the gas produced is mainly CO2, accounting for more than 70% of the total gas production.

9. The method for promoting anaerobic acid production from kitchen waste using iron materials according to claim 2, characterized in that: During the fermentation process, the internal materials of the anaerobic fermentation tank need to be continuously stirred, and the stirring rate should be maintained at 10-40 revolutions per minute to ensure sufficient contact between the microorganisms and the fermentation substrate.

10. The method for promoting anaerobic acid production from kitchen waste using iron materials according to claim 1, characterized in that: In step S3, after 7-14 days of natural fermentation, the organic acid concentration in the anaerobic fermentation tank reaches 10000-30000 mg / L, and COD Cr The concentration should be greater than 30000mg / L.

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