A method for promoting the fermentation of high-fat kitchen waste to produce volatile fatty acids by deoiling and electrofermentation

Abstract

The present invention discloses a method for promoting the fermentation of high-fat food waste to produce volatile fatty acids by combining deoiling with electrofermentation. The method first deoils the high-fat food waste until the mass percentage of fat is reduced to 1% to 3%. The deoiled food waste, anaerobic activated sludge, and a buffer solution are then mixed to form a fermentation mixture. The mixture is placed in an electrofermentation reactor and continuously energized. Anaerobic fermentation of the fermentation mixture occurs under continuous electrical stimulation, completing the treatment of the high-fat food waste. The method of the present invention, through the combined deoiling and electrofermentation process, shortens the anaerobic fermentation cycle, increases the yield of volatile fatty acids, and eliminates the production of byproducts such as carbon dioxide and methane. The method has the advantages of simple operation, low cost, fast reaction speed, short fermentation cycle, high yield, and environmental friendliness, and has excellent application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental protection, and in particular relates to a method for promoting the fermentation of high-oil-content kitchen waste to produce volatile fatty acids by combining deoiling with electric fermentation. Background Art

[0002] With the development of social production, people's demand for energy and chemicals continues to increase. Volatile fatty acids, as a sustainable and practical product, are often used as the preferred carbon source for microorganisms and can also be used to produce biodegradable plastics. However, the production of traditional volatile fatty acids usually relies on the consumption of fossil resources, which will aggravate environmental pollution and resource shortages. As a solid waste with high organic matter content, high water content and easy to corrupt, food waste needs to be treated in a reasonable way to avoid damage to the environment. Among them, the production of volatile fatty acids by anaerobic fermentation can achieve the reduction of food waste and resource utilization.

[0003] In traditional anaerobic fermentation, on the one hand, microorganisms spontaneously transfer electrons, resulting in a slow reaction rate. On the other hand, methane and carbon dioxide are produced as byproducts during anaerobic fermentation, which consumes carbon from food waste, thereby reducing fatty acid yields. Furthermore, the oil in high-fat food waste inhibits the hydrolysis process during anaerobic fermentation, leading to the inhibition of acid production. In addition to slowing the reaction rate, the prolonged fermentation cycle allows more volatile fatty acids to be metabolized and utilized by microorganisms as a high-quality carbon source, resulting in reduced volatile fatty acid accumulation. Studies have shown that the inhibitory effect of oil on fermentation can be eliminated by adding chemicals. However, since oil is a highly economically valuable component of high-fat food waste, the addition of chemicals not only increases costs but also reduces the economic value of oil recovery. Therefore, new technologies are needed to accelerate the reaction process and increase volatile fatty acid yields while ensuring oil recovery. This is of great significance for the resource utilization of high-fat food waste. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a method for promoting the fermentation of high-oil-content kitchen waste to produce volatile fatty acids by combining deoiling and electric fermentation, which is simple to operate, low in cost, fast in reaction speed, short in fermentation cycle, high in yield, and environmentally friendly.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0006] A method for promoting the fermentation of high-fat kitchen waste to produce volatile fatty acids by combining deoiling with electrofermentation comprises the following steps:

[0007] S1, deoiling the high-fat food waste until the mass percentage of fat is reduced to 1% to 3%, thereby obtaining deoiled food waste;

[0008] S2. Mixing the de-oiled food waste obtained in S1, the anaerobic activated sludge, and a buffer solution to obtain a fermentation mixture; the buffer solution is a phosphate buffer solution or a PBS buffer solution;

[0009] S3. Place the fermentation mixture obtained in S2 in an electric fermentation reactor, keep the power on, and perform anaerobic fermentation on the fermentation mixture under continuous electric stimulation conditions to complete the treatment of high-fat food waste.

[0010] After the high-fat food waste is deoiled, the mass percentage of fat is 1% to 3%, that is, the fat content is 1g fat / 100g food waste to 3g fat / 100g food waste.

[0011] The above method is further improved, wherein in S1, the specific process of the deoiling treatment is: cooking the high-fat food waste at 80°C to 95°C for 10min to 40min, then centrifuging at a speed of 2700r / min to 3000r / min for 5min to 15min to separate and obtain deoiled food waste; the mass percentage of fat in the high-fat food waste is 10% to 20%.

[0012] The mass percentage of fat in high-fat food waste is 10% to 20%, that is, the fat content is 10g fat / 100g food waste to 20g fat / 100g food waste.

[0013] The above method is further improved, in said S1, the high-fat food waste further includes the following treatment before use: screening the high-fat food waste to remove hard components, and crushing it into a mud-like state; the hard components include bones, paper towels, corn cobs and bamboo sticks.

[0014] The above method is further improved, wherein in S2, the volume ratio of the deoiled food waste to the anaerobic activated sludge is 3-6:1, and the ratio of the total volume of the deoiled food waste and the anaerobic activated sludge to the volume of the buffer solution is 1:3-4.

[0015] The above method is further improved, wherein in S2, the phosphate buffer solution includes at least one of a dipotassium hydrogen phosphate solution and a potassium dihydrogen phosphate solution, the concentration of the dipotassium hydrogen phosphate solution is 3.48 g / L to 5.22 g / L, and the concentration of the potassium dihydrogen phosphate solution is 4.08 g / L to 5.44 g / L;

[0016] The preparation method of the anaerobic activated sludge comprises the following steps: acclimating the activated sludge in an anaerobic environment until the gas production is stable to obtain the anaerobic activated sludge; the acclimation temperature is 30° C. to 35° C., and the acclimation time is ≥5 days.

[0017] The above method is further improved, wherein in S3, the time of the anaerobic fermentation is 11 to 18 days.

[0018] The above method is further improved, wherein in S3, the time of the anaerobic fermentation is 13 to 17 days.

[0019] The above method is further improved, wherein in S3, the voltage during the anaerobic fermentation is controlled to be 0.8V-1.0V, and the temperature of the anaerobic fermentation is 30°C-35°C.

[0020] The above method is further improved, in said S3, said electric fermentation reactor comprises a cathode and an anode; and the materials of said cathode and anode are both carbon felt.

[0021] The above method is further improved, in said S3, the anaerobic fermentation process further comprises: introducing nitrogen to keep the fermentation system in an anaerobic state.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] (1) The present invention provides a method for promoting the fermentation of high-fat food waste to produce volatile fatty acids by combining deoiling with electric fermentation. First, the high-fat food waste is deoiled until the mass percentage of fat is reduced to 1% to 3%. Then, the deoiled food waste, anaerobic activated sludge and buffer solution are mixed to form a fermentation mixture, which is placed in an electric fermentation reactor. The power is continuously supplied and the fermentation mixture is anaerobic fermented under continuous electric stimulation conditions to complete the treatment of the high-fat food waste. The method of the present invention, on the one hand, can reduce the grease in high-fat content kitchen waste by de-oiling treatment, thereby not having an inhibitory effect on the acid production process in anaerobic fermentation, and realizing the recycling of grease; on the other hand, on the basis of anaerobic fermentation, continuous power is applied to increase microvoltage (0.8V~1.0V), and this continuous electrical stimulation can not only promote the electron transfer of microorganisms, improve microbial activity, accelerate the reaction, but also shorten the fermentation time, further promote the production of volatile fatty acids, and at the same time, due to the acceleration of the reaction speed, the whole fermentation system accumulates volatile fatty acids more quickly, its pH value is reduced, and methanogens are inhibited, which will lead to the collapse of the methanogenic system, so that byproducts such as carbon dioxide and methane will not be produced during the fermentation process, which can reduce the loss of carbon source in the fermentation system, thereby further increasing the yield of volatile fatty acids. In addition, the voltage used in the present invention is relatively low and the resistance of the reaction system is extremely large, the power consumption is very small, and its cost is much lower than the cost of reducing the inhibitory effect of grease on the fermentation reaction by adding chemicals. The method of the present invention shortens the fermentation cycle of anaerobic fermentation, increases the yield of volatile fatty acids, and produces no by-products such as carbon dioxide and methane through deoiling combined with electric fermentation treatment. It has the advantages of simple operation, low cost, fast reaction speed, short fermentation cycle, high yield, and environmental protection, and has good application prospects.

[0024] (2) Compared with other common buffer solutions, the phosphate buffer solution used in the present invention not only does not affect the growth of microorganisms in the fermentation system, but also does not affect the production of volatile fatty acids. In other words, the phosphate buffer solution can retain biologically active substances to a large extent while providing pH buffering. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0026] Figure 1 This is a graph showing changes in the accumulation of volatile fatty acids during anaerobic fermentation of high-fat kitchen waste in Example 1 of the present invention.

[0027] Figure 2This is a diagram of the gas composition at the top of the reactor during the anaerobic fermentation of high-fat kitchen waste in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby. The materials and instruments used in the following examples are all commercially available.

[0029] Example 1:

[0030] The method of the present invention for promoting the fermentation of high-fat kitchen waste to produce volatile fatty acids by deoiling and electrofermentation comprises the following steps:

[0031] (1) The high-fat food waste is screened, and after removing hard components such as bones, paper towels, corn cobs, and bamboo sticks, it is crushed into a muddy state to obtain pre-treated food waste. Then, the pre-treated food waste is de-oiled, that is, after being steamed at 95°C for 30 minutes, it is centrifuged at a speed of 2950r / min for 10 minutes to separate the fat and de-oiled food waste. The fat can be recycled to produce various chemical raw materials. Among them, the mass percentage of fat in the high-fat food waste is 14%, the total solid content is 250.0±1.6g / L, and the volatile solid content is 200.4±0.8g / L; the mass percentage of fat in the de-oiled food waste is 2%, the total solid content is 343.9±1.1g / L, and the volatile solid content is 300.0±1.0g / L.

[0032] (2) Insert a cathode electrode and an anode electrode into a conventional anaerobic fermentation device (with an available volume of 500 mL). Both electrodes are made of 2×2 cm carbon felt. Connect the cathode electrode and the anode electrode to the negative and positive poles of the power supply, respectively, to complete the construction of the electric fermentation reactor. Connect the electric fermentation reactor in series with a resistor, which is connected in parallel with a signal collector. The signal collector is used to record the real-time current data changes. The electric fermentation reactor and the resistor are connected in series as a whole, and an external power supply is connected to provide a micro voltage.

[0033] (3) Adding 10 mL of anaerobic activated sludge and 180 mL of phosphate buffer solution to 50 mL of the de-oiled food waste to obtain a fermentation mixture. The phosphate buffer solution is a mixed solution of K2HPO4 and KH2PO4, wherein the concentration of K2HPO4 in the mixed solution is 4.0 g / L and the concentration of KH2PO4 is 4.4 g / L.

[0034] The preparation method of anaerobic activated sludge is as follows: acclimate the activated sludge at 35° C. under an anaerobic environment for 7 days until the activated sludge stably produces gas every day (ie, the gas production is stable), thereby obtaining anaerobic activated sludge.

[0035] (4) The fermentation mixture obtained in step (3) was added to the electric fermentation reactor in step (2), nitrogen was passed into the reactor for 2 minutes to ensure an anaerobic environment and the reactor was sealed, and at the same time, a power supply was turned on and a voltage of 0.9 V was continuously applied to the electric fermentation reactor.

[0036] (5) The electric fermentation reactor in step (4) is placed in a constant temperature incubator and subjected to anaerobic fermentation treatment at 35° C. for 27 days to complete the treatment of high-fat content food waste.

[0037] Control group 1: High-fat kitchen waste was not de-oiled and directly subjected to anaerobically fermented in an electric fermentation reactor, with other conditions being the same.

[0038] Control group 2: No electric fermentation reactor was used, and anaerobic fermentation was carried out directly using a traditional anaerobic fermentation device, with other conditions being the same.

[0039] Control group three: The high-fat kitchen waste was not de-oiled, and no electric fermentation reactor was used. Instead, anaerobic fermentation was carried out directly using a traditional anaerobic fermentation device, with other conditions being the same.

[0040] The test showed that the accumulation of volatile fatty acids in high-fat food waste before and after de-oiling was as follows: Figure 1 and as shown in Table 1.

[0041] Table 1 The time and concentration of volatile fatty acid accumulation reaching peak value during anaerobic fermentation of high-fat kitchen waste under different treatment conditions

[0042]

[0043]

[0044] Combine Figure 1 As shown in Table 1, compared with before deoiling, the fermentation and acid production cycle of high-fat food waste is shortened and the concentration of volatile fatty acids is increased after deoiling, which shows that the deoiling process can reduce the inhibition of the hydrolysis and acid production process by the oil while recovering the oil. Compared with traditional anaerobic fermentation, the present invention can effectively increase the production of volatile fatty acids and shorten the reaction time by adding electrical stimulation to the traditional anaerobic fermentation system, which shows that the addition of microcurrent can effectively promote the activity of microorganisms, thereby increasing the production of volatile fatty acids in food waste during the anaerobic fermentation process. It can be seen that when the deoiling process is combined with electrical fermentation, the acid production cycle of high-fat food waste is the shortest, only 16 days; and the accumulation of volatile fatty acids is the largest, which can reach 16.860g COD / L.

[0045] This example also tests the anaerobic fermentation of high-fat kitchen waste under traditional anaerobic fermentation and electro-fermentation conditions. When the fatty acid accumulation in each reactor reaches the maximum, the gas composition at the top of each reactor is as follows: Figure 2 shown.

[0046] Figure 2 This is a gas composition diagram at the top of the reactor during the anaerobic fermentation of high-fat kitchen waste in Example 1 of the present invention. Figure 2 As can be seen, the method of the present invention eliminates carbon dioxide, methane, and other carbon-containing byproducts in the gas from the electric fermentation reactor. This reduces the loss of carbon sources caused by these byproducts, thereby increasing the yield of volatile fatty acids. Furthermore, carbon dioxide and methane are the main gases that contribute to the greenhouse effect. Their reduction and elimination can reduce the environmental burden and contribute to the goal of "carbon neutrality and carbon emission reduction."

[0047] From the above results, it can be seen that the traditional anaerobic fermentation takes 24 days to reach the maximum accumulation of volatile fatty acids, while the method of the present invention (de-oiling combined with electro-fermentation) only takes 16 days, and the reaction process is advanced by 9 days. In addition, the method of this embodiment, according to the average current of 2.3×10 -6 A. The voltage is 0.9V, which is equivalent to 1.8×10 -5 kW·h of electrical energy (excluding internal circuit resistance), the added electrical stimulation cost is far lower than the cost of adding exogenous chemicals or simply separating the oil to eliminate its inhibitory effect on anaerobic fermentation. The present method, combining oil removal with electro-fermentation to treat high-oil food waste, produces 2.834 times more volatile fatty acids than traditional anaerobic fermentation, reducing production costs while increasing volatile fatty acid yields.

[0048] The above description is only a preferred embodiment of the present invention and does not constitute any formal limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the spirit and technical solution of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for promoting the fermentation of high-fat kitchen waste to produce volatile fatty acids by combining deoiling with electrofermentation, characterized in that: The following steps are involved: S1, deoiling the high-fat food waste until the mass percentage of fat is reduced to 1% to 2%, thereby obtaining deoiled food waste; S2. Mixing the de-oiled food waste obtained in S1, the anaerobic activated sludge, and a buffer solution to obtain a fermentation mixture; the buffer solution is a phosphate buffer solution; the volume ratio of the de-oiled food waste to the anaerobic activated sludge is 3 to 6:1, and the ratio of the total volume of the de-oiled food waste and the anaerobic activated sludge to the volume of the buffer solution is 1:3 to 4; S3. Placing the fermentation mixture obtained in S2 in an electric fermentation reactor, continuously supplying power, and performing anaerobic fermentation on the fermentation mixture under continuous electrical stimulation conditions to complete the treatment of high-fat food waste; during the anaerobic fermentation process, the voltage is controlled at 0.8V to 0.9V, and the anaerobic fermentation time is 11 days to 18 days.

2. The method of promoting the fermentation of high-fat kitchen waste to produce volatile fatty acids by combining deoiling with electrofermentation according to claim 1, characterized in that: In S1, the specific process of the deoiling treatment is: cooking the high-fat food waste at 80°C to 95°C for 10min to 40min, and then centrifuging it at a speed of 2700r / min to 3000r / min for 5min to 15min to separate the deoiled food waste; the mass percentage of fat in the high-fat food waste is 10% to 20%.

3. The method of promoting the fermentation of high-fat kitchen waste to produce volatile fatty acids by combining deoiling with electrofermentation according to claim 2, characterized in that: In S1, the high-fat food waste further includes the following processing before use: screening the high-fat food waste to remove hard components and crushing it into a mud-like state; the hard components include bones, paper towels, corn cobs and bamboo sticks.

4. The method of promoting the fermentation of high-fat kitchen waste to produce volatile fatty acids by combining deoiling with electrofermentation according to claim 3, characterized in that: In S2, the phosphate buffer solution includes at least one of a dipotassium hydrogen phosphate solution and a potassium dihydrogen phosphate solution, the concentration of the dipotassium hydrogen phosphate solution is 3.48 g / L to 5.22 g / L, and the concentration of the potassium dihydrogen phosphate solution is 4.08 g / L to 5.44 g / L; The preparation method of the anaerobic activated sludge comprises the following steps: acclimating the activated sludge in an anaerobic environment until the gas production is stable to obtain the anaerobic activated sludge; the acclimation temperature is 30° C. to 35° C., and the acclimation time is ≥5 days.

5. The method for promoting the fermentation of high-fat kitchen waste to produce volatile fatty acids by combining deoiling with electrofermentation according to any one of claims 1 to 4, characterized in that: In S3, the anaerobic fermentation time is 13 to 17 days.

6. The method for promoting the fermentation of high-fat kitchen waste to produce volatile fatty acids by combining deoiling with electrofermentation according to any one of claims 1 to 4, characterized in that: In S3, the temperature of the anaerobic fermentation is 30°C to 35°C.

7. The method for promoting the fermentation of high-fat kitchen waste to produce volatile fatty acids by combining deoiling with electrofermentation according to any one of claims 1 to 4, characterized in that: In S3, the electric fermentation reactor includes a cathode and an anode; the cathode and the anode are both made of carbon felt.

8. The method for promoting the fermentation of high-fat kitchen waste to produce volatile fatty acids by combining deoiling with electrofermentation according to any one of claims 1 to 4, characterized in that: In S3, the anaerobic fermentation process further includes: introducing nitrogen to keep the fermentation system in an anaerobic state.

9. The method of promoting the fermentation of high-fat kitchen waste to produce volatile fatty acids by combining deoiling with electrofermentation according to claim 1, characterized in that: In S2, the buffer solution is PBS buffer.

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