CN114934077A - Two-phase anaerobic digestion method for producing methane by enhancing directional conversion of lactic acid - Google Patents

Abstract

The invention discloses a two-phase anaerobic digestion methane production method for strengthening the directional conversion of lactic acid. The method includes hydrolytic acidification reaction and methanation reaction, by inoculating Megasphaera elsdenii ATCC 12561 in the hydrolytic acidification phase and adding acetate to promote the orientation of lactic acid during the hydrolysis and acidification of organic solid wastes such as kitchen waste. It is converted into hydrogen to produce butyric acid, and the acidified liquid and acid-producing phase gas are both used as substrates, which are transferred to the methane-producing phase for anaerobic digestion to produce methane. The method utilizes exogenous biochemicals to regulate the directional transformation of the hydrolyzed acid-producing phase, overcomes the inhibitory effect of lactic acid accumulation in anaerobic fermentation, improves the hydrolysis-acidification efficiency, and at the same time promotes the enrichment of butyric acid in the acidified liquid and increases the concentration of the acid-producing phase in the gas. The hydrogen content can enhance the anaerobic methane production efficiency. The invention has the advantages of high efficiency, easy operation and the like, can improve the conversion efficiency and methane production of anaerobic digestion, and reduce carbon emission.

Description

A kind of two-phase anaerobic digestion methane production method that strengthens lactic acid directional conversion

technical field

The invention belongs to the technical field of waste recycling, and relates to a method for producing methane by two-phase anaerobic digestion, in particular to a method for producing methane by two-phase anaerobic digestion using exogenous biochemical additives to strengthen the directional conversion of lactic acid.

Background technique

Kitchen waste is a typical biomass solid waste with high organic content, easy biodegradation, and high resource properties. If the kitchen waste is landfilled, it will not only occupy valuable land resources, but also generate a large amount of greenhouse gases such as NH ₃ , CH ₄ , N ₂ O and CO ₂ during the natural degradation process of the waste biomass, which will further aggravate the carbon reduction pressure. Compared with landfill and incineration, biological treatment technology is an important technical means to achieve rapid reduction and targeted resource utilization of organic solid waste such as kitchen waste. Among them, anaerobic digestion technology is a well-developed and popular technology in organic waste treatment, but most of the research focuses on the use of single-phase anaerobic reactors to process food waste to generate biogas, and the inhibition of the potential accumulation of soluble organic matter The effect promoted the development of two-phase anaerobic reactors.

The two-phase anaerobic reactor separates the hydrolysis-acidification phase and the methanogenic phase, thereby providing optimal conditions for acid-producing bacteria and methanogenic archaea, promoting the efficiency and system stability of anaerobic digestion of food waste. Among them, the degradation of kitchen waste in the hydrolysis and acidification phase is accompanied by the generation of hydrogen and carbon dioxide, and the carbon conversion rate of this gas accounts for 20-30% of the total carbon conversion efficiency. The release of acid-generating phase gas greatly reduces the energy recovery efficiency of the anaerobic system. In order to improve the methane production within the range of the total carbon conversion efficiency and realize the efficient reuse of the acid-producing phase gas in the two-phase anaerobic digestion process, CN106282243A discloses "an improved method for producing methane by two-phase anaerobic digestion and System", which regulates the hydrogen partial pressure and hydrogen-carbon ratio of the acid-producing phase gas by hydrolyzing the pressure in the headspace of the acidification reactor, and transfers the acid-producing phase gas to the methanation reactor for reuse, which greatly improves the methane production. For this process, promoting the production of hydrogen and acid in the acidified phase is the key to further upgrading the carbon conversion efficiency and methane production of the system.

Previous studies have shown that the hydrolytic acidification of kitchen waste first undergoes lactic acid metabolism and then butyric acid metabolism. Among them, lactic acid metabolism during the hydrolysis and acidification of solid organic waste is one of the limiting factors of hydrogen production and fermentation and cannot be avoided. Reducing lactate production is a common approach to overcome inhibition of lactate metabolism. Among them, thermal pretreatment can not only kill lactic acid bacteria and hydrogen-consuming bacteria, but also retain the spores of hydrogen-producing bacteria, so it is often used to inhibit the production of lactic acid to increase the production of hydrogen and acid from organic wastes. Patent CN104998886A discloses a method for phase-separated energy production of kitchen waste, which adopts moist heat pretreatment to improve the hydrogen production and methane production of kitchen waste in a phase-separated system, but the process is based on a phase-separation reaction. Energy is recovered from waste, and the products of anaerobic hydrogen production, such as hydrogen and carbon dioxide, are not used in the methanogenesis phase to increase methane production and reduce carbon dioxide emissions. Patent CN104561222A is to solve the inhibition caused by acidification liquid, by pre-processing the mixture of kitchen waste and sludge at 135 °C high temperature, and then inoculating hydrogen-producing bacteria to carry out hydrogen-producing deep acidification pretreatment, and the pretreatment liquid is then subjected to methanation reaction. To a certain extent, the methane production rate of organic waste is improved; however, in addition to the increased energy consumption of thermal pretreatment, yeast powder, hydrogen-producing bacteria and methanogenic bacteria need to be added at different stages, which increases the complexity of the operation. Gas-phase products that are not acidified by hydrolysis, especially carbon dioxide, are efficiently reused in the methanogenic phase. Thermal pretreatment inevitably has problems such as high energy consumption, high organic matter loss and so on.

In order to overcome the inhibition of lactic acid in the hydrolysis and acidification of high-solid food waste, in addition to reducing the production of lactic acid by means of pretreatment, promoting the conversion of lactic acid in the acidified phase is another idea to optimize the hydrogen production and fermentation of food waste, and it is also an urgent problem to be solved. . Among them, adding microbial inoculants is a common way to improve the transformation of organic matter. Patent CN104087622A realizes co-production of butanol and hydrogen from lignocellulose by inoculating anaerobic hydrogen-producing bacteria of different species of Clostridium to regulate acetone-butanol-ethanol fermentation process and hydrogen-producing fermentation products. Patent CN110484570A improves the hydrolysis efficiency of kitchen waste by inoculating Bacillus microorganisms, such as Bacillus subtilis, Bacillus licheniformis, etc., thereby increasing the hydrogen production. However, although the above-mentioned technology promotes the conversion of substrates, its hydrolytic acidification mainly aims to produce a large amount of hydrogen to improve the utilization rate of organic matter. The technical concept and method of improving carbon conversion and methane production efficiency by promoting the directional conversion of lactic acid in the process of hydrolysis and acidification. At present, there is no report on strengthening the directional conversion of lactic acid in the hydrolysis and acidification reaction of kitchen waste, and there is no report on strengthening the directional conversion of lactic acid in the hydrolysis and acidification phase in two-phase anaerobic digestion to promote the production of methane in the methane-producing phase.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a two-phase anaerobic digestion and methane production method for strengthening the directional conversion of lactic acid, wherein the hydrolysis and acidification phase utilizes exogenous functional bacteria to directionally strengthen the conversion of lactic acid, and simultaneously solves the problem of anaerobic fermentation of organic wastes such as kitchen waste. Inhibition of hydrogen production and acid production by accumulation of lactic acid in the medium, the method can promote the directional conversion of lactic acid in the hydrolysis and acidification reaction, and further enhance its directional hydrogen production and acid production through acetate, and the acidification liquid and acid production phase gas are directly subjected to methane production reaction , thereby increasing the carbon conversion rate and methane yield, and improving the efficiency of two-phase anaerobic digestion to produce methane.

The method of the invention is a two-phase anaerobic digestion method, including hydrolytic acidification reaction and methanation reaction, and is characterized in that, Megasphaera elsdenii ATCC 12561 is inoculated into the hydrolytic acidification phase, and the pH is adjusted and then hydrolyzed. For acidification, both the acidified liquid and the acid-producing phase gas produced by the hydrolysis-acidification reaction are transferred to the methane-producing phase as substrates, and the methane-producing phase is digested anaerobic to produce methane. The method of the present invention is used for degradable organic solid waste, including but not limited to kitchen waste, poultry manure, agricultural waste, etc., preferably kitchen waste.

The Megasphaera elsdenii is a typical lactic acid-decomposing bacteria, which uses lactic acid as a carbon source to increase the value of organic acids such as propionic acid and butyric acid. The invention inoculates Megacoccus escheriensis in the hydrolysis and acidification phase of the two-phase anaerobic digestion to strengthen the directional transformation of lactic acid, so as to overcome the inhibitory effect of lactic acid accumulation in the anaerobic fermentation, improve the hydrolysis efficiency, and at the same time guide the transformation of the substitution pathway to a favorable direction , directional hydrogen production and acid production make the acidification liquid contain more butyric acid, and the acid-producing phase gas has a higher hydrogen-to-carbon ratio, which can be converted into the target product methane more efficiently as a substrate in the methanation reaction.

As one of the preferred embodiments, the inoculum amount of Megasphaera elsdenii ATCC12561 is 2-5% (vol/vol), and the inoculation concentration is 2-4×10 ⁸ CFU/mL.

CN106282243A has realized the reuse of acid-generating phase gas in methanation reaction in two-phase anaerobic digestion method. Different from the method of adjusting the headspace pressure of the hydrolysis-acidification reactor adopted in this method, one of the results of strengthening the directional hydrogen production of lactic acid in the method of the present invention is that the acid-producing phase gas contains more hydrogen, which can be directly transferred to the methanation reactor. The enhanced reduction of carbon dioxide in turn facilitates the recovery of energy (methane) and reduces carbon dioxide emissions.

In order to better realize the technical effect of the present invention, as one of the preferred embodiments, the method of the present invention further comprises adding acetate, such as acetic acid or sodium acetate, to the hydrolyzed and acidified phase to further strengthen the directional transformation of lactic acid, Promote the directional enrichment of butyric acid in the acidification solution and increase the hydrogen content in the acid-producing phase gas.

As one of the preferred embodiments, the volume ratio of hydrogen to carbon dioxide of the acid-generating phase gas transferred to the methanation phase is greater than or equal to 4. In addition to adding acetate in the hydrolysis and acidification phase, those skilled in the art can also use other methods to increase the hydrogen ratio of the acid-producing phase gas, including but not limited to hydrolysis and acidification reactor headspace pressurization, lye absorption, etc.

As one of the preferred embodiments, the pH of the hydrolysis and acidification phase is 6.0±1.0. The pH is adjusted by adding an alkali solution to the hydrolysis and acidification phase, which can be selected from common alkalis such as sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate, etc., preferably a mixed alkali solution containing sodium acetate.

As one of the preferred embodiments, the temperature of the hydrolysis-acidification phase and the methanogenic phase is maintained at 37°C.

As one of the preferred embodiments, part of the acidified liquid of the hydrolysis and acidification phase is transferred to the methane-producing phase, and the rest is added with water to make up the volume, and the pH is adjusted and then refluxed to the hydrolysis and acidification phase.

Specifically and optimally, the technical solution of the present invention is: a method for strengthening the directional conversion of lactic acid by two-phase anaerobic digestion for methane production, comprising the following steps:

1) Add the broken or diced organic solid waste into the hydrolysis acidification reactor, add filler material, seed sludge and water, and mix evenly;

2) Inoculate Megasphaera elsdenii ATCC 12561 in the hydrolysis acidification reactor, the inoculation amount is 2-5% (vol/vol) of the total organic solid waste, and the inoculation concentration is 2-4×10 ⁸ CFU/mL;

3) Adjust the pH to 6.0±1.0, and carry out hydrolysis and acidification in the hydrolysis acidification reactor; transfer the generated acidification liquid and acid-producing phase gas to the methanation reactor, and transfer part of the acidification liquid to the methanation reactor when transferring the acidification liquid , the rest of the acidification solution is added with water to make up the volume and adjust the pH to 6.0±1.0, then return to the hydrolysis acidification reactor;

4) The acidification liquid and the acid producing phase gas are anaerobic digested in the methanation reactor to produce methane.

Preferably, 25-50%, most preferably 50% (v/v) of the acidified solution is refluxed to the hydrolysis acidification reactor, and the remainder is transferred to the methanation reactor for further utilization by methanogens.

Preferably, after adding water to the acidified solution to make up the volume, a mixed alkali solution containing sodium acetate is added to adjust the pH, so as to promote the directional fermentation of the hydrolyzed acidified phase and increase the hydrogen content in the acidified gas.

Beneficial effects: the method for enhancing the directional transformation of lactic acid by two-phase anaerobic digestion and methane production of the present invention utilizes the property of Megasococcus escherienii to decompose lactic acid to regulate the lactic acid metabolism pathway of hydrolysis and acid production, so as to solve the limitation of hydrogen production by lactic acid accumulation. It promotes the conversion of directional hydrogen production and acid production, more butyric acid is enriched in the acidification liquid, and the acid production phase gas has a higher hydrogen-to-carbon ratio, so as to achieve the improvement of the hydrolysis acidification efficiency and the efficient utilization of the hydrolysis acidification phase products. By adding acetate into the acidified phase (using a mixed alkaline solution containing sodium acetate to adjust the pH), the directional fermentation path can be further promoted, the hydrogen production and concentration can be increased, and the reduction of carbon dioxide to methane can be promoted, and the overall methane recovery rate can be improved. The invention is simple to operate, does not need thermal pretreatment of organic solid wastes such as kitchen waste, etc., has low overall energy consumption, mild reaction conditions, obvious directional fermentation effect, and is suitable for engineering applications.

Description of drawings

Fig. 1 is the process flow diagram of the inventive method;

Fig. 2 is the daily hydrogen production in the hydrolysis acidification reactor in the method of the present invention;

Fig. 3 is the daily methane production in the methanation reactor in the method of the present invention;

Figure 4. Carbon balance analysis diagram of a two-phase anaerobic digestion methanogenesis system.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments. The following examples are only used to illustrate the present invention, and the protection scope of the present invention is not limited by the specific embodiments, but by the claims.

In the following examples, the specific implementation process of the method of the present invention and its technical effects are described by taking the two-phase anaerobic digestion of kitchen waste for methane production as an example.

Taking kitchen waste as a substrate, the method for enhancing the directional conversion of lactic acid for producing methane by two-phase anaerobic digestion specifically includes the following steps:

1) Cut the kitchen waste into 10-30 mm squares, add it to the hydrolysis acidification reactor, add filler material and seed sludge, add water and mix evenly; which includes the kitchen waste, 10% (wt%) of the filler material and 20 % (wt%) of the inoculated sludge, the solid content of the solid anaerobic fermentation of the whole kitchen waste is 15%;

2) Inoculate Megasphaera elsdenii ATCC 12561 in the hydrolysis and acidification reactor, the inoculation amount is 2-5% of the total amount of food waste in the system, and the concentration of microbial bacteria liquid is 2-4×10 ⁸ CFU/ mL;

3) The pH of the alkaline solution is adjusted to 6.0±1.0, and the kitchen waste is hydrolyzed and acidified in the hydrolysis and acidification reactor, and the acidified liquid and acid-producing phase gas produced are transferred to the methanation reactor every day; when transferring the acidified liquid, half of each time The acidified liquid is transferred to the methane-producing reactor, the other half of the acidified liquid is added with water to make up the volume, and the pH is adjusted to 6.0±1.0 with an alkaline solution, and then returned to the hydrolysis-acidification reactor to further strengthen the reaction of lactic acid for directional hydrogen production and butyric acid production; The mixed alkaline solution containing sodium acetate can further promote the directional fermentation of the hydrolyzed acidified phase and increase the hydrogen content;

4) In the methanation reactor, anaerobic digestion of acidification liquid and acid-producing phase gas produces methane.

The operating temperature of both the hydrolysis acidification reactor and the methanation reactor was maintained at 37°C.

Figure 1 shows the process flow diagram of the method of the present invention. For the specific implementation of the present invention, reference may be made to CN106282243A for the system and operation of the two-phase anaerobic digestion method. The system for producing methane by the two-phase anaerobic digestion method according to the present invention mainly includes a hydrolysis acidification reactor and a methanation reactor, and a device for transferring materials between them. Likewise, to practice the present invention, the methanation reactors include, but are not limited to, an Upflow Anaerobic Sludge Bed Reactor (UASB), a Complete Mixing Reactor (CSTR), an Internal Circulation Anaerobic Reactor (IC) or Expanded Granular Sludge Bed Reactor (EGSB); the hydrolysis acidification reactor includes but is not limited to percolation bed reactor, and those skilled in the art can also select other suitable hydrolysis acidification reactors according to common knowledge in the art. The material conveying device between the two-phase reactors transfers the gas and liquid of the hydrolyzed acidification phase to the methanogenic phase, respectively. Different from CN106282243A, the method of the present invention does not need to regulate and control the pressure of the headspace of the acidification reactor, so the sensors, controllers and other equipment related to the regulation of hydrogen partial pressure and fine regulation and control operations are omitted. No internal or external pressure is applied to the headspace of the hydrolysis-acidification reactor, and the gas transfer only needs to install a pipeline at the top to connect the bottom of the methanation reactor to transfer the acid-producing phase gas to the methanation reactor.

In the following examples, the hydrolysis-acidification reactor adopts a percolation bed reactor, and the methanogenic reactor adopts an up-flow anaerobic sludge bed reactor.

According to the method of the present invention, using kitchen waste as a substrate, by strengthening the directional conversion of lactic acid to produce hydrogen and acid, the output of directional conversion of lactic acid to butyric acid is as high as 200.5-279.7 grams of COD per kilogram of volatile solids, and the output of hydrogen is as high as 80 -86 liters per kilogram of volatile solids. The directional conversion of lactic acid not only overcomes the limitation of lactic acid accumulation on hydrogen production and acid production, and improves the efficiency of hydrolysis and acidification, but also the acidification liquid and acidification gas are used as substrates for the methanation reaction directly. Converted to target products with higher methane recovery. Compared with the existing two-phase anaerobic digestion method, the method of the invention increases the methane recovery amount of kitchen waste by 11%-25% and the maximum daily methane production rate by 19.8%-41.8%.

The method of the present invention can be operated in batch, semi-continuous or continuous mode.

Example 1

A method for enhancing the directional conversion of lactic acid for methane production by two-phase anaerobic digestion, comprising the following steps:

(1) Take 2.0 kg of kitchen waste, cut it into 10-30 mm squares, evenly mix 10% filler and 20% inoculated anaerobic sludge to the hydrolysis and acidification reactor, and add tap water to make the solid content of the system 15%.

(2) Inoculate 2% of Megacoccus escheriensis bacterial liquid according to the processing amount of kitchen waste, wherein the bacterial concentration in the bacterial liquid is 2-4×10 ⁸ CFU/mL;

(3) adjusting the pH to be 6.0±1.0, after the fermentation of the substrate in the hydrolysis acidification reactor, the acidification liquid and acid-producing phase gas produced are transferred to the methanation reactor;

The hydrolysis and acidification phase leachate is collected once a day, half of the leachate is fed into the methanation reactor for decomposition and utilization by methanogens, and the other half of the leachate is filled with tap water, adjusted to pH 6.0±1.0 with caustic soda, and refluxed to hydrolysis and acidification. reactor.

(4) The acidification liquid and the acid-producing phase gas are anaerobic digested in the methanation reactor to produce methane.

Example 2

A method for enhancing the directional conversion of lactic acid for methane production by two-phase anaerobic digestion, comprising the following steps:

(1) Take 2.0 kg of kitchen waste, cut it into 10-30 mm squares, evenly mix 10% filler and 20% inoculated anaerobic sludge to the hydrolysis and acidification reactor, and add tap water to make the solid content of the system 15%.

(2) Inoculate 2% of Megacoccus escheriensis bacterial liquid according to the processing amount of kitchen waste, wherein the bacterial concentration in the bacterial liquid is 2-4×10 ⁸ CFU/mL;

(3) adjusting the pH to be 6.0±1.0, after the fermentation of the substrate in the hydrolysis acidification reactor, the acidification liquid and acid-producing phase gas produced are transferred to the methanation reactor;

The hydrolysis and acidification phase leachate is collected once a day, half of the leachate is fed into the methanation reactor for decomposition and utilization by methanogens, and the other half of the leachate is filled with tap water, and the pH is adjusted to 6.0 with an alkaline regulator containing sodium acetate. ±1.0, reflux to hydrolysis acidification reactor.

(4) The acidification liquid and the acid-producing phase gas are anaerobic digested in the methanation reactor to produce methane.

Comparative Example 1

As a control group, the same two-phase anaerobic digestion system with a gas transfer device as in Example 1 was used for anaerobic digestion of kitchen waste, and the steps and conditions were basically the same as those in Example 1. The difference is that the hydrolyzed and acidified phase of Comparative Example 1 was not inoculated with M. eischei.

Comparative Example 2

As a control group, the same two-phase anaerobic digestion system with a gas transfer device as in Example 2 was used to perform anaerobic digestion of kitchen waste, and the steps and conditions were basically the same as those in Example 2. The difference is that the hydrolyzed and acidified phase of Comparative Example 2 was not inoculated with M. eischei.

In each of the above examples or comparative examples, during the anaerobic digestion of food waste, the yields of lactic acid-directed metabolites butyric acid and hydrogen in the hydrolysis acidification reactor, and the methane gas produced in the methanation reactor were measured every day. The specific test results are shown in Table 1, Figure 2 and Figure 3.

The daily hydrogen production in the hydrolysis-acidification reactor is shown in Figure 2, and the daily methane production in the methanation reactor is shown in Figure 3. It can be seen from FIG. 2 that the inoculation of M. escheriensis significantly improved the hydrogen yield of the hydrolyzed acidified phase, and the daily peak of hydrogen production in Example 1 was 1.7 times that of Comparative Example 1. Combined with the application of the alkaline regulator containing sodium acetate, the peak value of daily hydrogen production in Example 2 can be further increased to 2.2 times that of Comparative Example 1. However, the hydrogen production of Comparative Example 2 was extremely low, and the introduction of an alkaline regulator containing sodium acetate without inoculation with M. escheriensis would change the metabolic pathway of acid production, which is not conducive to hydrogen production. It can be seen from FIG. 3 that the daily methane production of Example 1 and Example 2 is higher than that of Comparative Example 1 and Comparative Example 2. The peak daily methane production of Example 1 was 14.1 L. After the introduction of an alkaline regulator containing sodium acetate, the peak methane production in Example 2 was further increased to 16.7 L. This production is about 1.5 times the peak daily methane production of Comparative Examples 1 and 2. In addition, from the trend point of view, the daily methane production increased significantly after 9 days of reaction, which corresponds to the rapid increase in the daily hydrogen production, indicating that in the two-phase anaerobic digestion, promoting the hydrogen production metabolism of the hydrolysis-acidification reactor did increase the methane production. methane production from the reactor.

The results show that the inoculation of Megacoccus escheriensis bacterial solution in the hydrolysis and acidification reactor can promote the hydrolysis and acidification phase to metabolize hydrogen to produce butyric acid. Yield. Compared with the control group (Comparative Example 1), the production of butyric acid in the hydrolyzed and acidified solution increased by 18% after inoculation with Megacoccus escheriensis. increased to 65%. However, only adding an alkaline regulator containing sodium acetate without inoculating M. escheriensis would change the metabolic pathway of acid production, and most of butyric acid and hydrogen would be reused through the β-oxidation pathway to form caproic acid. Therefore, Comparative Example 2 The yield of midcaproic acid was as high as 116.2 gCOD/kg volatile solids. In terms of gas production, compared with the control group (Comparative Example 1), the hydrogen production of the embodiment is increased by 35.3%-57.6%, and the maximum daily methane production rate is increased by 19.8%-41.8%. The results show that the directional transformation of lactic acid can be effectively enhanced by inoculation with M. escheriensis, the methane recovery rate of kitchen waste is improved, and the hydrolysis and acidification efficiency is also improved. Compared with the published patent CN106282243A, the method of the present invention uses biochemical additives to further improve the overall conversion efficiency of the kitchen waste of the two-phase anaerobic digestion system without pressure regulation, wherein the soluble COD (chemical oxygen demand) The yield and methane production increased from 564.9 gCOD/kg volatile solids and 250 L/kg volatile solids to 780.3 gCOD/kg volatile solids and 348.6 L/kg volatile solids, respectively.

Figure 4 is a carbon balance analysis of a two-phase anaerobic system under the conditions of Comparative Example 1 and Example 2, including carbon distribution in soluble, insoluble and gas phase. First, the intensified directional transformation of lactic acid (inoculation with M. escheriensis and introduction of an alkaline regulator containing sodium acetate) can greatly reduce the carbon residue in the digestate. Correspondingly, the carbon biochemical conversion efficiency of kitchen waste was increased from 68% in Comparative Example 1 to 78% in Example 2. Among them, the carbon content of the soluble metabolites produced by the hydrolysis acidification reactor increased from 58% in Comparative Example 1 to 72% in Example 2. Notably, the carbon content of the acid-generating gas was significantly reduced by a factor of about 2. Therefore, by strengthening the directional transformation of lactic acid, the acid-producing metabolic pathway of food waste is changed, and processes such as the directional transformation of lactic acid-butyric acid can promote the biosynthesis of organic matter, so as to maintain more available carbon and reduce the carbon loss of acid-producing gas. .

For the total carbon conversion efficiency of the two-phase anaerobic digestion system, Comparative Example 1 and Example 2 were 32% and 43%, respectively. In the methanation reactor, its methane recovery is positively correlated with the amount of carbon converted by the hydrolysis-acidification reactor. For Example 2, it can be seen from the carbon flow in the acid production stage that the enhanced directional conversion of lactic acid effectively accelerates the degradation of the kitchen and reduces the carbon content in the digestate, thereby providing more organic matter for methane production. In Example 2, butyrate, the optimal precursor for methane production, was greatly increased to stimulate an enhanced acetophilic methanogenesis pathway. In addition, the hydrogen production of Example 2 is increased, so that more hydrogen can be transferred to the methanogenesis stage, thereby promoting the reduction of CO ₂ and the production of methane by intensifying the hydrogenophilic methanogenesis.

Table 1 Two-phase anaerobic digestion performance of food waste

Claims (10)

1. a method for strengthening the two-phase anaerobic digestion methane production of lactic acid directional conversion, comprising hydrolysis acidification reaction and methanation reaction, it is characterized in that, Megasphaera elsdenii ATCC 12561 is inoculated in hydrolysis acidification phase , hydrolyzed and acidified after adjusting the pH, and the acidified liquid and acid-producing phase gas were transferred to the methane-producing phase as a substrate, and the methane-producing phase was converted into methane by anaerobic digestion. 2. the method for the two-phase anaerobic digestion methanogenesis of strengthening lactic acid directional conversion according to claim 1, is characterized in that, the inoculum of described Megasphaera elsdenii (Megasphaera elsdenii) ATCC 12561 is 2-5 % (vol/vol), the inoculum concentration was 2-4×10 ⁸ CFU/mL. 3. The method for strengthening the two-phase anaerobic digestion and methane production of lactic acid directional conversion according to claim 1 is characterized in that, acetate is added in the described hydrolysis and acidification phase. 4. the method for strengthening the two-phase anaerobic digestion methane production of lactic acid directional conversion according to claim 1 is characterized in that, the volume ratio of hydrogen and carbon dioxide of the described acid-producing phase gas transferred to the methanation phase is greater than or equal to 4. The method for two-phase anaerobic digestion and methane production by strengthening the directional conversion of lactic acid according to claim 1, wherein the pH of the hydrolysis and acidification phase is 6.0±1.0. 6 . The method for two-phase anaerobic digestion and methane production by strengthening the directional conversion of lactic acid according to claim 1 , wherein the temperature of the hydrolysis-acidification phase and the methane-producing phase is maintained at 37° C. 7 . 7. the method for two-phase anaerobic digestion methanogenesis of strengthening lactic acid directional conversion according to claim 1 is characterized in that, the acidified liquid part of described hydrolysis acidification phase is transferred to the methane-producing phase, and all the other add water to make up the volume, and adjust After pH reflux to the hydrolyzed acidified phase. 8. the method for strengthening the two-phase anaerobic digestion methane production of lactic acid directional conversion according to claim 1, is characterized in that, comprises the following steps: 1) Add the broken or diced organic solid waste into the hydrolysis acidification reactor, add filler material, seed sludge and water, and mix evenly; 2) Inoculate Megasphaera elsdenii ATCC 12561 in the hydrolysis acidification reactor, the inoculation amount is 2-5% (vol/vol) of the total organic solid waste, and the inoculation concentration is 2-4×10 ⁸ CFU/mL; 3) Adjust the pH to 6.0±1.0, and carry out hydrolysis and acidification in the hydrolysis acidification reactor; transfer the generated acidification liquid and acid-producing phase gas to the methanation reactor, and transfer part of the acidification liquid to the methanation reactor when transferring the acidification liquid , the rest of the acidification solution is added with water to make up the volume and adjust the pH to 6.0±1.0, then return to the hydrolysis acidification reactor; 4) The acidification liquid and the acid producing phase gas are anaerobic digested in the methanation reactor to produce methane. 9. the method for strengthening the two-phase anaerobic digestion methane production of lactic acid directional conversion according to claim 8, is characterized in that, described acidification liquid is refluxed to hydrolysis acidification reactor by volume 25-50%, and the remainder is transferred to the methanation reactor. 10 . The method for enhancing the directional conversion of lactic acid by two-phase anaerobic digestion for methane production according to claim 8 , wherein the acidified solution is added with water to make up the volume, and a mixed alkali solution containing sodium acetate is added to adjust the pH. 11 .

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