Method for improving anaerobic gas production stability of kitchen waste by combining with addition of carbon and iron materials

Abstract

The invention discloses a method for improving anaerobic gas production stability of kitchen waste by adding carbon and iron materials in a combined mode, and the method comprises the following steps that S1, after the kitchen waste is fully smashed, the kitchen waste is added into an anaerobic reactor to be subjected to anaerobic fermentation methane production treatment; s2, a certain amount of biochar is added into an initial system for producing methane through anaerobic fermentation of the kitchen waste, a mixed solution is formed through mixing and stirring, and the effect of improving the anaerobic fermentation stability is obvious after the reaction; and S3, adding a certain amount of ferroferric oxide into the mixed solution, stirring and carrying out anaerobic digestion reaction so as to improve the enzyme activity of microorganisms and increase the biogas production rate of biogas. The biochar and the ferroferric oxide are added in the initial stage of anaerobic fermentation, so that the inhibition effect of harmful substances on microorganisms can be relieved, growth sites and nutrient elements are provided for the microorganisms, the growth of the microorganisms is accelerated, the activity of the microorganisms is improved, and the generation of methane is promoted; further, the biogas production rate of biogas is improved, and the stability of a reaction system is maintained.

Description

Technical Field

[0001] The present application relates to the technical field of anaerobic gas production from food waste, and in particular to a method for improving the stability of anaerobic gas production from food waste by adding combined carbon and iron materials. Background Art

[0002] At present, with the acceleration of urbanization, food waste, as the main component of urban solid waste, accounts for 50%-70% of the total urban solid waste. The amount of food waste generated is increasing year by year, which poses 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.

[0003] In the related technologies, anaerobic digestion as a way of resource disposal of food waste has gradually gained attention, so that anaerobic digestion has been widely used in the disposal of food waste. Under anaerobic conditions, organic waste is converted into biogas, thereby realizing energy recovery. However, due to the characteristics of easy degradation and complex composition of food waste, in the anaerobic fermentation system of food waste, the accumulation of organic acids inhibits the activity of methanogens, resulting in gas production failure and poor system stability. Summary of the invention

[0004] The purpose of the present application is to provide a method for improving the stability of anaerobic gas production from food waste by adding carbon and iron materials, so as to solve the problem that due to the characteristics of easy degradation and complex composition of food waste, the accumulation of organic acids in the anaerobic fermentation system of food waste inhibits the activity of methanogens, resulting in gas production failure and poor system stability.

[0005] The method provided in the present application for improving the stability of anaerobic gas production from kitchen waste by adding carbon and iron materials adopts the following technical solution: The method for improving the stability of anaerobic gas production by adding carbon and iron materials to kitchen waste comprises the following steps: S1, after the kitchen waste is fully crushed, it is added into the anaerobic reactor for anaerobic fermentation and methane production; S2. Then, a certain amount of biochar is added to the initial system of anaerobic fermentation of kitchen waste to produce methane, and mixed and stirred to form a mixed solution. The anaerobic digestion reaction has a significant effect on improving the stability of anaerobic fermentation. S3. Add a certain amount of ferroferric oxide to the mixed solution, mix and stir, and perform anaerobic digestion to increase the enzyme activity of the microorganisms and the production rate of biogas.

[0006] Furthermore, the biochar should be smaller than 10 mesh, and its dosage is 0.05%-10%.

[0007] Furthermore, the ferrosoferric oxide should be in powder form, with a particle size of 100-425 mesh, and the dosage should be 0.05%-10%.

[0008] Furthermore, in the system of anaerobic fermentation of food waste to produce methane, the total solids (TS) of the fermentation liquid ranges from 0.5% to 4%, and the organic acid concentration is less than 30,000 mg / L.

[0009] Furthermore, the pH of the solution in the anaerobic reactor is adjusted to be between 6 and 9, and the fermentation temperature is adjusted to be between 30° C. and 50° C.

[0010] Compared with the prior art, the beneficial effects of this application are: The present application, by adding biochar and ferroferric oxide in the early stage of anaerobic fermentation, can alleviate the inhibitory effect of harmful substances on microorganisms, provide growth sites and nutrients for microorganisms, accelerate microbial growth and improve microbial activity, and promote methane production, thereby increasing the biogas production rate and maintaining the stability of the reaction system.

[0011] At the same time, by using low-cost biochar as an additive for anaerobic digestion, the stability of anaerobic fermentation can be significantly improved, and the operation process is simple, the cost is low, and there is no secondary pollution. In addition, by using low-cost and large-capacity ferric oxide, the enzyme activity of microorganisms can be increased, the biogas production rate can be increased, and the operation process is simple, the cost is low, and there is no secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the biogas production rate of the control group without adding additives in the examples of the present application.

[0013] Figure 2 This is a schematic diagram of the biogas production rate in a reactor to which biochar and ferrosoferric oxide are added according to an embodiment of the present application. DETAILED DESCRIPTION

[0014] The following is combined with Figure 1-2 This application is described in further detail.

[0015] The present application discloses a method for improving the stability of anaerobic gas production by adding carbon and iron materials to kitchen waste, comprising the following steps: S1. After the food waste is fully crushed, it is added to the anaerobic reactor for anaerobic fermentation and methane production. Specifically, in the system of anaerobic fermentation and methane production of food waste, the following conditions are also required: the total solids (TS) of the fermentation liquid is in the range of 0.5%-4%, and the organic acid concentration is less than 30000 mg / L; at the same time, the pH range of the solution in the anaerobic reactor is adjusted to between 6-9, and the fermentation temperature range is between 30℃-50℃.

[0016] S2, then add a certain amount of biochar to the initial system of anaerobic fermentation of kitchen waste to produce methane, mix and stir to form a mixed solution, and the anaerobic digestion reaction is followed by an obvious effect of improving the stability of anaerobic fermentation. Specifically, the biochar added in step S2 should be less than 10 mesh, and the addition amount is 0.05%-10%.

[0017] More specifically, as a porous material rich in various functional groups, biochar can be added to the anaerobic fermentation system to provide growth sites for microorganisms with hydrolysis, acidification and methanogenesis functions, thereby increasing the number of microorganisms. The functional groups rich in biochar can adsorb substances harmful to anaerobic digestion and improve the buffering capacity of the anaerobic system. Biochar is also conductive and can provide a bridge for electron transfer between microorganisms, accelerate interspecies electron transfer, and promote the production of methane.

[0018] At the same time, in addition to using biochar, the solution of this application can also use activated carbon, carbon coating, carbon nanotubes and other carbon materials as replacements. In this way, due to the good physical and chemical properties of carbon materials, they are often used in anaerobic digestion reactors to improve gas production efficiency and enhance the stability of the fermentation system. In addition, activated carbon and biochar have large specific surface areas, well-developed pores, and a certain alkalinity, which can provide certain growth sites for microorganisms and improve the buffering capacity of the reactor, thereby promoting direct electron transfer (DIET) and thus improving the efficiency of biogas production.

[0019] S3, adding a certain amount of ferroferric oxide to the mixed solution, mixing and stirring, and performing anaerobic digestion reaction to improve the enzyme activity of microorganisms and the production rate of biogas. Specifically, the ferroferric oxide added in step S3 should be in powder form, with a particle size of 100-425 mesh, and the addition amount should be 0.05%-10%.

[0020] More specifically, since the growth of microorganisms is inseparable from the supply of nutrients, adding appropriate trace elements to the fermentation system can enhance the microorganisms' ability to resist adversity and improve the activity of microorganisms, thereby improving the buffering capacity of the reaction system and enhancing the stability of the fermentation system. Among all the nutrients, the concentration of iron required for anaerobic digestion is the highest. Ferrous ions can react with hydrogen sulfide generated by anaerobic digestion to form ferrous sulfide precipitation, reducing the damage of hydrogen sulfide or sulfur ions to microorganisms.

[0021] When metals react with sulfur ions to form sulfides, causing the anaerobic digestion system to lack metals, some microorganisms can release special metal ligands to bind to metals, thereby increasing the availability of metals; adding appropriate ferrous ions to the anaerobic digestion system can increase the methane production rate.

[0022] Thus, the present application contains divalent iron and trivalent iron through ferroferric oxide, which can accelerate the transfer of electrons through redox reactions during anaerobic digestion; the iron material can also serve as a metal ligand for some key enzymes to increase enzyme activity, accelerate the reaction, and thereby improve the stability of the fermentation system and the methane production rate.

[0023] Therefore, due to the different mechanisms of action of porous materials and nutrients in improving the stability and gas production efficiency of anaerobic digestion systems, the simultaneous addition of biochar and ferric oxide to the initial anaerobic fermentation system can have a synergistic effect, which can alleviate the inhibitory effect of harmful substances on microorganisms, provide growth sites and nutrients for microorganisms, accelerate microbial growth and improve microbial activity, and promote the production of methane, thereby increasing the gas production rate of biogas and maintaining the stability of the reaction system.

[0024] Secondly, the present application scheme can significantly improve the stability of anaerobic fermentation by using low-priced biochar as an additive for anaerobic digestion, and the operation process is simple, the cost is low, and there is no secondary pollution. At the same time, by using low-priced and large-capacity ferric oxide, the enzyme activity of microorganisms can be increased, the biogas production rate can be increased, and the operation process is simple, the cost is low, and there is no secondary pollution.

[0025] Specifically, refer to Figure 1 and Figure 2 , which is a comparison between the biogas production rate in the reactor with biochar and ferroferric oxide added and the biogas production rate in the control group without additives.

[0026] Therefore, from Figure 1 and Figure 2 From the comparison, it can be seen that the biogas production rate in the reactor with the addition of biochar and ferroferric oxide is improved, and the gas production state of the reactor is more stable. Since the methane concentration of the two groups is relatively consistent, at 60%±2%, the combined addition of biochar and ferroferric oxide promotes methane production. Overall, the methane production rate in the group with the combined addition of biochar and ferroferric oxide is between 5%-50% higher than that of the control group without additives. At the same time, in this process, in the experimental group containing additives, the consumption of volatile fatty acids should be accelerated by 5%-50%, while maintaining the stability of gas production in the fermentation system.

[0027] In addition, methanogens should be mainly acetic acid methanogens, and the diversity of microorganisms should be increased by 5%-40%. In addition, during the entire anaerobic fermentation process, the activity of microorganisms and enzymes were increased by more than 5%.

[0028] 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 improving the stability of anaerobic gas production by adding carbon and iron materials to kitchen waste, characterized in that: The following steps are involved: S1, after the kitchen waste is fully crushed, it is added into the anaerobic reactor for anaerobic fermentation and methane production; S2. Then, a certain amount of biochar is added to the initial system of anaerobic fermentation of kitchen waste to produce methane, and mixed and stirred to form a mixed solution. The anaerobic digestion reaction has a significant effect on improving the stability of anaerobic fermentation. S3. Add a certain amount of ferroferric oxide to the mixed solution, mix and stir, and perform anaerobic digestion to increase the enzyme activity of the microorganisms and the production rate of biogas.

2. The method for improving the stability of anaerobic gas production by adding carbon and iron materials according to claim 1, characterized in that: The biochar should be smaller than 10 mesh, and the dosage is 0.05%-10%.

3. The method for improving the stability of anaerobic gas production by combining carbon and iron materials according to claim 1, characterized in that: The ferrosoferric oxide should be in powder form with a particle size of 100-425 meshes, and the dosage should be 0.05%-10%.

4. The method for improving the stability of anaerobic gas production by combining carbon and iron materials according to claim 1, characterized in that: In the anaerobic fermentation system of food waste to produce methane, the total solids (TS) of the fermentation liquid ranges from 0.5% to 4%, and the organic acid concentration is less than 30,000 mg / L.

5. The method for improving the stability of anaerobic gas production by combining carbon and iron materials according to claim 4, characterized in that: The pH of the solution in the anaerobic reactor is adjusted to be between 6 and 9, and the fermentation temperature is adjusted to be between 30° C. and 50° C.

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