Microbial electrosynthesis reinforced solid waste hydrolysis and anaerobic digestion biogas high value utilization system

Abstract

The present application belongs to the field of microbial electrochemistry and solid organic waste resource, and discloses a microbial electro-synthesis reinforced solid waste hydrolysis and anaerobic digestion biogas high-value utilization system. The system comprises a cathode chamber and an anode chamber separated by an ion exchange membrane, an external electrochemical driving device and an anaerobic digestion unit connected with the anode chamber. The cathode chamber is provided with a cathode electrode and an anaerobic acetic acid-producing microbial system, and is connected with the biogas produced by anaerobic digestion, so that the carbon dioxide in the biogas is reduced to acetic acid at the cathode and the methane-enriched gas is output. The anode chamber is provided with an anode electrode and is added with organic solid waste and a hydrolysis microbial system, so that the electrochemical-biological synergistic hydrolysis oxidation of the organic solid waste and its hydrolysis products serves as the anode reaction, the oxygen evolution is inhibited, and the oxygen transmembrane migration is reduced; the anode chamber hydrolysis products flow into the anaerobic digestion unit to produce biogas, realizing the integrated operation of solid waste hydrolysis and biogas upgrading.

Description

Technical Field

[0001] This invention relates to the fields of bioelectrochemistry, anaerobic digestion, and organic solid waste resource utilization. Specifically, it relates to a system and method that deeply couples microbial electrosynthesis (MES) with the electrochemical-biological synergistic hydrolysis and oxidation and anaerobic digestion process of organic solid waste, in order to improve the hydrolysis efficiency of organic solid waste, decarbonize and purify anaerobic digestion biogas, and convert carbon dioxide into resources. Background Technology

[0002] Microbial electrosynthesis (MES) is a bioelectrochemical technology that uses applied electrical energy to drive microorganisms at the cathode to reduce carbon dioxide (CO2) into organic products such as acetic acid, formic acid, and ethanol. It can be applied to scenarios such as greenhouse gas resource utilization and renewable energy chemical storage. Most existing MES devices employ a membrane-separated two-chamber reactor configuration: the cathode chamber is used for the CO2 reduction reaction, and the anode chamber provides electrons and maintains the circuit closed.

[0003] In the aforementioned dual-chamber MES system, the anodic reaction is typically dominated by the electrochemical oxidation of water, i.e., the oxygen evolution reaction (OER). OER produces oxygen and releases electrons at the anode, but the oxygen migrates to the cathode chamber in dissolved or gaseous form through the ion exchange membrane. Cathode-side microbial electrosynthesis usually relies on a strictly anaerobic, reducing microenvironment. The entry of oxygen into the cathode chamber can easily suppress anaerobic bacteria, reduce electron utilization efficiency, and degrade product selectivity, leading to a decrease in the formation rate of reduction products such as acetic acid, and even causing system fluctuations or instability.

[0004] To address oxygen migration / toxicity issues, existing technologies typically employ operational measures such as reducing current density, shrinking reactor size, improving membrane barrier capacity, increasing displacement / purging, or frequently changing the culture medium. However, under pilot-scale or scale-up operating conditions, larger reactor volumes, longer operating cycles, and increased target flux often require higher electrochemical driving forces, thereby exacerbating the cumulative effect of anodic oxygen and the risk of transmembrane migration. Simply relying on adjusting operating conditions or membrane barrier measures often leads to increased internal resistance, increased energy consumption, and increased maintenance frequency, making it difficult to balance stability and engineering economics.

[0005] On the other hand, anaerobic digestion of organic solid waste (such as sewage sludge, kitchen waste, livestock and poultry manure, and straw) is a common process for reducing the volume of organic solid waste and recovering energy, but this process is generally limited by the low rate of the hydrolysis stage. To improve hydrolysis efficiency, pretreatment methods such as thermal treatment, chemical oxidation, and mechanical crushing have been proposed, but these methods are often accompanied by problems such as high energy or chemical consumption, large equipment investment, increased operating costs, and potential secondary pollution. In solid / high solids content systems, how to achieve hydrolysis enhancement at a lower cost and match it with the subsequent anaerobic digestion process remains an important engineering requirement.

[0006] Biogas produced by anaerobic digestion mainly consists of methane (CH4) and carbon dioxide, with the carbon dioxide volume fraction typically ranging from 30% to 45%. A high carbon dioxide content reduces the calorific value of the biogas and limits its grid connection or comprehensive utilization. Existing biogas purification technologies include physical absorption, chemical absorption, pressure swing adsorption, and membrane separation, although these can achieve CH4 purification... 4 / CO2 separation is generally characterized by high energy consumption, complex processes, high operating costs, and insufficient resource utilization, as CO2 is mostly treated as "separated emissions". Furthermore, biogas purification units are usually operated as independent components, making it difficult to integrate and coordinate with anaerobic digestion or CO2 conversion processes.

[0007] In recent years, some studies have attempted to apply bioelectrochemical technology to the in-situ conversion of CO2 in biogas systems, aiming to achieve biogas decarbonization and purification as well as CO2 resource utilization. However, under biogas conditions, the partial pressure of CO2 decreases, mass transfer is limited, and the requirements for internal system resistance and long-term stability are higher. The CO2 conversion rate and product enrichment still face engineering bottlenecks. At the same time, if the anode is still dominated by OER, the damage to the anaerobic microenvironment of the cathode caused by oxygen migration is more easily amplified in biogas purification applications.

[0008] In summary, current technologies lack an integrated technical solution for engineering operation that can simultaneously achieve the following within the same system: suppressing or significantly reducing anode oxygen evolution and oxygen migration to the cathode under membrane-separated MES conditions, thereby maintaining the anaerobic reduction environment at the cathode and ensuring the stable selectivity of CO2 reduction products; using organic solid waste as the anode-side reaction substrate to achieve efficient electron supply and enhance the hydrolysis and dissolution conversion of solid organic matter, thus alleviating the rate-limiting effect of anaerobic digestion hydrolysis; and forming a closed-loop coupling of materials and gases with the anaerobic digestion and biogas treatment processes, enabling efficient removal / conversion of CO2 in biogas to obtain liquid products such as acetic acid, while simultaneously outputting methane-enriched gas. Therefore, how to construct and operate the above-mentioned synergistic integrated system and method is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] Technical problems to be solved

[0010] In view of the problems existing in the background technology, such as oxygen transmembrane migration caused by anodic oxygen evolution and instability of the cathode anaerobic system, rate limitation of anaerobic digestion and hydrolysis of solid organic waste, and difficulty in realizing resource utilization of carbon dioxide in biogas during purification, this invention aims to provide a system and method that deeply couples microbial electrosynthesis with the electrochemical-biological synergistic hydrolysis and oxidation of organic solid waste and anaerobic digestion process, so as to improve the system stability while realizing biogas decarbonization and purification and CO2 resource conversion.

[0011] Technical solution

[0012] To achieve the above objectives, the present invention provides a biogas decarbonization and purification and CO2 resource utilization system that couples microbial electrosynthesis, organic solid waste hydrolysis and anaerobic digestion, including a microbial electrosynthesis reactor, an external electrochemical drive device, an anaerobic digestion unit and gas delivery pipelines and liquid pipelines connected thereto.

[0013] The microbial electrosynthesis reactor includes a cathode chamber and an anode chamber separated by an ion exchange membrane; the cathode chamber is equipped with a cathode electrode and an anaerobic acetic acid-producing microbial system; the anode chamber is equipped with an anode electrode, organic solid waste, and a hydrolytic microbial system; the cathode electrode and the anode electrode are electrically connected to form a circuit through the external electrochemical drive device.

[0014] The anode chamber is provided with a hydrolysis product outlet and is in fluid communication with the feed inlet of the anaerobic digestion unit, so that the hydrolysis products generated in the anode chamber can be used as anaerobic digestion substrates; the anaerobic digestion unit is provided with a biogas outlet and is connected to the gas inlet of the cathode chamber through the gas delivery pipeline, so that the biogas generated by anaerobic digestion can enter the cathode chamber; the outlet of the cathode chamber discharges decarbonized and purified methane-enriched gas, while acetic acid products are obtained in the cathode liquid.

[0015] In the system of the present invention, the anode chamber uses the electrochemical-biological synergistic hydrolysis and oxidation reaction of organic solid waste as the main anode reaction to replace or inhibit the oxygen evolution reaction of water, thereby reducing oxygen generation from the source; and with the help of the synergistic consumption of dissolved oxygen by the hydrolytic microbial system, a low redox potential environment is maintained on the anode side, thereby reducing the transmembrane migration of oxygen to the cathode chamber, maintaining the stability of the anaerobic microenvironment in the cathode chamber, and providing continuous and stable reaction conditions for the reduction of CO2 to acetic acid at the cathode.

[0016] In one embodiment, the ion exchange membrane is any one of a cation exchange membrane, anion exchange membrane, bipolar membrane, or proton exchange membrane, to achieve ion conduction and isolation between the anode and cathode.

[0017] In one embodiment, the cathode electrode is any one of a gas diffusion electrode, a carbon felt electrode, a carbon paper electrode, or a graphite felt electrode; the anode electrode is any one of a carbon felt electrode, a titanium mesh electrode, a titanium plate electrode, or a titanium-based titanium dioxide electrode.

[0018] In one embodiment, the external electrochemical drive device operates in a constant current or constant voltage mode; the current density in the constant current mode is 1–20 A / m. 2 Preferably 3 to 10 A / m 2 .

[0019] In one embodiment, the organic solid waste is selected from residual sludge, primary sludge, kitchen waste, livestock and poultry manure, straw, garden waste or a combination thereof; the addition load of the organic solid waste is 5 to 30 g VS / L based on volatile solids (VS).

[0020] In one embodiment, the effective volume of the microbial electrosynthesis reactor is 1 to 50 L, preferably 3 to 10 L; or it is a scale-up system composed of multiple microbial electrosynthesis reactor modules connected in parallel and / or in series.

[0021] In one embodiment, the cathode chamber is vented with a carbon dioxide-containing gas, which is one or more of biogas, simulated biogas, carbon dioxide, or industrial exhaust gas; wherein the volume fraction of carbon dioxide is 10% to 100%, preferably 20% to 50%. The gas inlet of the cathode chamber can be connected to the biogas outlet of the anaerobic digestion unit and an external carbon dioxide-containing gas source through a three-way valve or a switching valve, respectively, to achieve selective introduction of different gas sources.

[0022] In one embodiment, the cathode chamber is connected to a gas circulation device, allowing the air phase at the top of the cathode chamber to circulate back, thereby enhancing CO2 mass transfer and increasing the decarbonization rate.

[0023] In one embodiment, the anaerobic acetic acid-producing microbial system includes an anaerobic autotrophic bacterial community with acetic acid as the main product. The bacterial community is selected from the genera *Acetobacterium*, *Clostridium*, *Sporomusa*, and combinations thereof, or is an enriched bacterial community on the cathode side of a long-term stable microbial electrosynthesis reactor.

[0024] In a preferred embodiment, by adjusting the organic solid waste load and / or applying external electrochemical driving conditions, the redox potential of the liquid phase in the anode chamber is maintained below -100 mV (vs. Ag / AgCl), preferably from -100 mV to -400 mV (vs. Ag / AgCl), in order to further suppress the oxygen evolution reaction and reduce oxygen transmembrane migration.

[0025] This invention also provides a method for treating organic solid waste, decarbonizing and purifying biogas, and utilizing CO2 resources using the above-mentioned system, comprising: adding organic solid waste to the anode chamber and inoculating it with a hydrolytic microbial system; inoculating the cathode chamber with an anaerobic acetic acid-producing microbial system and establishing an anaerobic environment; applying electrochemical driving conditions to cause electrochemical-biological synergistic hydrolysis and oxidation in the anode chamber and providing electrons to the cathode; flowing the hydrolysis products from the anode chamber into an anaerobic digestion unit to generate biogas; and transporting the biogas to the cathode chamber, where CO2 is reduced to acetic acid at the cathode and decarbonized and purified methane-enriched gas is output.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] (1) By changing the main reaction at the anode from the oxygen evolution reaction of water to the electrochemical-biological synergistic hydrolysis and oxidation reaction with organic solid waste as the substrate, the generation of oxygen at the source is reduced and the transmembrane migration of oxygen to the cathode is reduced, which is beneficial to reducing the risk of cathode oxygen pollution.

[0028] (2) By maintaining a low redox potential environment on the anode side and synergistically consuming oxygen, the anaerobic microenvironment in the cathode chamber is kept stable, thereby improving the operational stability and electron utilization efficiency of the CO2 reduction to acetic acid process.

[0029] (3) The synergistic effect of anodic electrochemistry and biology enhances the hydrolysis and acidification of organic solid waste, increases the release of intermediate products such as soluble chemical oxygen demand and volatile fatty acids, provides more readily available substrates for subsequent anaerobic digestion and improves gas production performance;

[0030] (4) The cathode can selectively reduce and convert CO2 in biogas to obtain liquid products such as acetic acid and simultaneously increase the volume fraction of methane, thereby realizing the synergistic integration of biogas decarbonization and purification and CO2 resource utilization. Attached Figure Description

[0031] The accompanying drawings are used to further illustrate the technical solutions of the present invention and constitute a part of the specification. The drawings, in conjunction with specific embodiments, are used to explain the technical solutions of the present invention, but do not constitute a limitation on the scope of protection of the present invention.

[0032] In the attached diagram:

[0033] Figure 1 This is a schematic diagram of the overall system construction of the present invention, which couples microbial electrosynthesis, organic solid waste hydrolysis and anaerobic digestion.

[0034] Figure 2 The curves showing the change of redox potential (ORP) of the cathode chamber and the anode chamber over time during the operation of the system in Example 1 are shown, where (a) is the ORP change curve of the anode chamber and (b) is the ORP change curve of the cathode chamber.

[0035] Figure 3 The curve showing the change in acetic acid concentration in the catholyte over operating time in Example 1 is shown.

[0036] Figure 4 The curves showing the effects of biogas decarbonization and purification and CO2 resource utilization in the cathode chamber in Example 2 are shown. (a) is the curve showing the change of CO2 volume fraction in the gas phase of the cathode chamber over time, and (b) is the curve showing the change of acetic acid concentration in the catholyte over time.

[0037] Figure 5 The curves show the comparison of the hydrolysis, dissolution and conversion performance of organic solid waste in the anode chamber in Example 3 and Comparative Example 2, where (a) is the curve of soluble chemical oxygen demand (SCOD) changing over time, and (b) is the curve of volatile fatty acid (VFA) concentration changing over time.

[0038] Figure 6 The curves showing the cumulative methane production over time during the anaerobic digestion process in Example 4 and Comparative Example 3 are shown.

[0039] Figure 7 The curves showing the changes in oxidation-reduction potential (ORP) of the cathode and anode chambers over time during the operation of the microbial electrosynthesis system in Comparative Example 1 are shown, where (a) is the ORP change curve of the anode chamber and (b) is the ORP change curve of the cathode chamber.

[0040] Figure 8 The curve shows the change in acetic acid concentration in the catholyte over operating time in Comparative Example 1.

[0041] Explanation of reference numerals in the attached figures:

[0042] exist Figure 1 The meanings of the labels in the attached figures are as follows: 1—Microbial electrosynthesis reactor; 2—Cathode chamber; 3—Anode chamber; 4—Ion exchange membrane; 5—Cathode electrode; 6—Anode electrode; 7—External electrochemical drive device; 8—Anaerobic digestion unit; 9—Hydrolysis product flow path; 10—Biogas transmission pipeline; 11—Decarbonized and purified biogas outlet (methane enrichment gas outlet); 12—Acetic acid product outlet (cathodic liquid discharge outlet); 13—Organic solid waste inlet. Detailed Implementation

[0043] To make the objectives, technical solutions, and beneficial effects of this invention clearer and more complete, the invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described are for illustrative purposes only and are not intended to limit the invention. Various equivalent substitutions or improvements made by those skilled in the art without departing from the spirit and substance of this invention should fall within the protection scope of this invention.

[0044] Unless otherwise stated, the reagents, materials, equipment and experimental conditions involved in the following examples and comparative examples can be obtained using conventional methods or commercial products known in the art.

[0045] Terminology and Detection / Analysis Methods

[0046] Terminology and abbreviations: ORP stands for Oxidation-Reduction Potential; SCOD stands for Soluble Chemical Oxygen Demand; VFA stands for Volatile Fatty Acids; VS stands for Volatile Solids; MES stands for Microbial Electrosynthesis. Unless otherwise specified, liquid concentration is expressed in g / L, and gas volume fraction is expressed in %.

[0047] ORP: Measured using an online ORP electrode with Ag / AgCl as the reference electrode; ORP results are expressed as potentials relative to Ag / AgCl.

[0048] pH and temperature: pH was measured using an online pH electrode; temperature was maintained by a constant temperature water bath or jacket temperature control.

[0049] Gas flow rate and composition: The inlet / outlet gas flow rate is regulated and recorded by a mass flow controller or flow meter; the gas composition (CH4, CO2, etc.) is determined by gas chromatography or an online gas analyzer.

[0050] Liquid phase products: Acetic acid and other volatile fatty acids can be determined by high performance liquid chromatography, ion chromatography or titration.

[0051] SCOD and VS: SCOD and VS are determined according to current national / industry standard methods.

[0052] Data processing and indicator definition:

[0053] (1) Carbon dioxide removal rate: η CO2 (%) = (C) in,CO2 - C out,CO2 ) / C in,CO2 ×100%. Where, C in,CO2 With C out,CO2 These represent the CO2 volume fractions in the inlet and outlet gases, respectively. When the inlet and outlet gas flow rates are inconsistent, a flow correction form can be used: η CO2 (%) = (F) in ·C in,CO2 -F out ·C out,CO2 ) / (F in ·C in,CO2 )×100%. Where, F in With F out These represent the inlet and outlet gas volume flow rates, respectively.

[0054] (2) Methane enrichment: expressed as the volume fraction of methane in the gas exit gas, C out,CH4(%) indicates the percentage increase; if necessary, the increase ΔC can be used. CH4 =C out,CH4 - C in,CH4 (Unit: percentage points) Characterization.

[0055] (3) Inorganic carbon conversion rate (based on acetic acid): η C,acetate (%) = n C,acetate / n C,CO2(removed) ×100%. Where, n C,acetate =2·n acetate ;n C,CO2(removed) The number of CO2 carbon moles removed from the gas phase within a statistical time interval can be calculated by converting the inlet and outlet gas volumes and their volume fractions.

[0056] (4) Acetic acid Faraday efficiency: FE acetate (%) = (n) acetate ·z·F) / (I·t)×100%. Where, n acetate To determine the net number of moles of acetic acid produced within the statistical time interval, z = 8, F = 96485 C / mol e − I represents the current, and t represents the energizing time. If other reduction products are generated simultaneously, FE can be calculated separately according to their electron equivalents, and the overall Faraday efficiency can be given.

[0057] (5) Energy consumption: Electrical energy input W = U within the statistical time interval avg •I·t. This can be calculated based on unit acetic acid production or unit biogas treatment volume, for example: E acetate =W / m acetate ; or E biogas =W / V biogas,N Among them, U avg V is the average voltage of the entire cell. biogas,N The volume of biogas processed is calculated under standard conditions (0 ℃, 101.325 kPa). If auxiliary energy consumption such as stirring and circulation needs to be included, it can be combined with the electrical energy input and included in the total energy consumption.

[0058] System structure and connection relationships

[0059] like Figure 1 As shown, the coupling system of the present invention includes a microbial electrosynthesis reactor 1, an external electrochemical drive device 7, an anaerobic digestion unit 8, and associated liquid / gas transport pipelines (including a hydrolysis product flow path 9, a biogas transport pipeline 10, etc.). The microbial electrosynthesis reactor 1 is divided into a cathode chamber 2 and an anode chamber 3 by an ion exchange membrane 4.

[0060] The cathode chamber 2 is equipped with a cathode electrode 5 and an anaerobic acetic acid-producing microbial system. The cathode chamber 2 has an inlet for introducing CO2 gas and an outlet for discharging the methane-enriched gas after decarbonization and purification. The catholyte can collect acetic acid products through the acetic acid product outlet 12. The cathode electrode 5 can be a carbon-based electrode such as a gas diffusion electrode, carbon felt electrode, carbon paper electrode, or graphite felt electrode.

[0061] The anode chamber 3 is equipped with an anode electrode 6, organic solid waste, and a hydrolysis microbial system. The anode chamber 3 has an organic solid waste inlet 13 and a hydrolysis product outlet, which is fluidly connected to the inlet of the anaerobic digestion unit 8 via a hydrolysis product flow path 9. The anode electrode 6 can be a carbon felt electrode, a titanium mesh electrode, a titanium plate electrode, or a titanium-based titanium dioxide electrode, etc.

[0062] An external electrochemical drive device 7 is electrically connected to the cathode electrode 5 and the anode electrode 6 to form a circuit, which can operate in constant current or constant voltage mode and is used to record operating data such as voltage and current. The ion exchange membrane 4 is used to realize ion conduction between the anode and cathode and suppress solute convection mixing, and can be any one of cation exchange membrane, anion exchange membrane, bipolar membrane or proton exchange membrane.

[0063] The anaerobic digestion unit 8 can be a batch or continuous anaerobic digestion reactor, used to anaerobic digest the hydrolysis products from the anode chamber 3 to produce biogas; its biogas outlet is connected to the air inlet of the cathode chamber 2 through the biogas delivery pipeline 10, thereby forming a coupled closed loop of "anode hydrolysis products → anaerobic digestion → biogas → cathode chamber decarbonization and purification and CO2 resource conversion".

[0064] To improve mass transfer and operational stability, the system can be equipped with a gas circulation device to circulate the air phase at the top of the cathode chamber to enhance CO2 mass transfer and increase the decarbonization rate; a circulation pump can also be configured to realize the circulation of cathode / anode electrolyte or cross-unit transport.

[0065] System operation method

[0066] (1) Equipment preparation: according to Figure 1 Construct a microbial electrosynthesis reactor 1 and an anaerobic digestion unit 8, and connect the hydrolysis product flow path 9 to the biogas delivery pipeline 10; perform an airtightness check on the system. Add electrolyte / culture medium to the cathode chamber 2 and the anode chamber 3, respectively.

[0067] (2) Inoculation and addition: Inoculate the anaerobic acetic acid-producing microbial system into the cathode chamber 2; add organic solid waste into the anode chamber 3 and inoculate it with the hydrolytic microbial system.

[0068] (3) Establish an anaerobic environment: purge the cathode chamber 2 (and the anode chamber 3 and anaerobic digestion unit 8 if necessary) with N2 or inert gas to remove dissolved oxygen, and then keep the system sealed or maintain inert gas protection.

[0069] (4) Apply electrochemical drive: Start the external electrochemical drive device 7 to make the system run under the set current density or voltage conditions; during operation, the cathode / anode ORP can be monitored online, and by adjusting the organic solid waste load and / or electrochemical drive conditions, the anode chamber ORP can be maintained below -100 mV (vs. Ag / AgCl) (preferably -100 to -400 mV) to suppress the oxygen evolution reaction and reduce oxygen transmembrane migration.

[0070] (5) Closed loop of materials and gas: The hydrolysis products of the anode chamber 3 flow into the anaerobic digestion unit 8 for anaerobic digestion to produce biogas; the biogas produced by anaerobic digestion is introduced into the cathode chamber 2 through the pipeline 10 for decarbonization purification and CO2 conversion; methane-enriched gas is discharged from the outlet of the cathode chamber, and the acetic acid product is collected through the acetic acid product outlet 12 of the cathode liquid.

[0071] (6) Sampling and analysis: Collect gas and liquid phase samples regularly, record operating parameters such as ORP, current, voltage, and pH, and calculate indicators such as CO2 removal rate, acetic acid yield, Faraday efficiency and energy consumption.

[0072] Examples and Comparative Examples

[0073] The reactor configurations and key operating conditions for each embodiment and comparative example are summarized in Table 1. Except for the operating conditions listed in Table 1, the device structures and connections for each embodiment and comparative example are as follows: Figure 1 The construction, ion exchange membrane, electrode materials, electrode spacing, stirring and circulation methods, etc., can all be selected and set within the conventional range in this field according to the reactor scale and operation requirements.

[0074] Table 1. Summary of reactor configurations and key operating conditions for the examples and comparative examples.

[0075]

[0076] Example 1: Performance of acetic acid synthesis at the cathode in the coupling system

[0077] This embodiment is used to verify the promoting effect of the stability of the cathode anaerobic acetic acid electrosynthesis process and the acetic acid accumulation effect under the anodic coupled organic solid waste electrochemical-biological synergistic hydrolysis oxidation conditions.

[0078] (1) System construction: Construction such as Figure 1 The coupling system shown has an effective volume of 5 L for the microbial electrosynthesis reactor. The cathode chamber and anode chamber are separated by an ion exchange membrane. The cathode chamber is equipped with a cathode electrode, and the anode chamber is equipped with an anode electrode. The system is connected to the liquid and gas pipelines of the anaerobic digestion unit.

[0079] (2) Anode side addition and inoculation: Add organic solid waste (taking excess sludge as an example) to the anode chamber, with an addition load of 17.8 g VS / L in terms of VS; inoculate anaerobic granular sludge as a hydrolytic microbial system to synergistically promote the hydrolysis and acidification of solid waste and consume any dissolved oxygen that may be generated under energized conditions.

[0080] (3) Cathode side inoculation and air intake: Inoculate the cathode chamber with an anaerobic acetic acid-producing microbial system (e.g., from a microbial community enriched on the cathode side of a long-term stable microbial electrosynthesis reactor; the inoculation amount can be 10% to 30% of the effective volume of the cathode chamber); before operation, purge the cathode chamber with N2 to establish an anaerobic environment, and then continuously introduce high-purity CO2 into the cathode chamber as a carbon source, with an air intake flow rate of 100 mL / min.

[0081] (4) Electrochemical operation: The external electrochemical drive device operates in constant current mode with a current density of 5 A / m 2 The reaction temperature was 37 ℃; and the system operated continuously for 30 days.

[0082] (5) Sampling and monitoring: During operation, cathodic liquid samples are collected periodically to determine the acetic acid concentration, and the changes in ORP in the cathode and anode chambers, as well as operating parameters such as voltage and current, are recorded simultaneously.

[0083] Experimental results are as follows Figure 2 , Figure 3 As shown in Table 2, under the conditions of anolyl-coupled organic solid waste hydrolysis oxidation, the ORP in the anode chamber remained in the low potential range (maintained as negative or below 0 mV), indicating that the oxygen evolution reaction on the anode side was inhibited and the system maintained a low redox potential environment. The ORP in the cathode chamber steadily decreased and remained below -350 mV (vs. Ag / AgCl) in the later stage of operation, providing a stable reducing microenvironment for the anaerobic acetic acid production reaction at the cathode. The acetic acid concentration at the cathode accumulated continuously with the operating time, reaching approximately 4 g / L on day 20, exhibiting stable and continuous synthesis characteristics. The above results demonstrate that introducing electrochemical-biological synergistic hydrolysis oxidation of organic solid waste into the anode to replace / inhibit the oxygen evolution reaction can effectively reduce the impact of oxygen transmembrane migration on the cathode and improve the stability and cumulative yield of acetic acid synthesis.

[0084] Example 2: Performance of Cathode Biogas Decarbonization and Purification and CO2 Conversion in Coupled Systems

[0085] This embodiment is used to verify the cathode's ability to convert CO2 in simulated biogas and the biogas decarbonization and purification effect under the conditions of anodic coupling organic solid waste hydrolysis and oxidation.

[0086] (1) System construction and anode side conditions: The system structure, reactor volume, anode organic solid waste addition load and anode inoculation method are the same as in Example 1.

[0087] (2) Cathode-side air intake: The anaerobic acetic acid-producing microbial system derived from the cathode side of Example 1 is inoculated into the cathode chamber; simulated biogas is continuously introduced into the headspace of the cathode chamber as a carbon source. The simulated biogas consists of 35% (volume fraction) CO2 and 65% (volume fraction) CH4, and the air intake flow rate is 100 mL / min. The biogas decarbonization and purification and acetic acid production effects are statistically analyzed in a 24-h operating cycle; when enhanced mass transfer is required, a gas circulation device can be used for headspace air phase recirculation.

[0088] (3) Electrochemical operation: The external electrochemical drive device operates in constant current mode with a current density of 5 A / m 2 The reaction temperature was 37 ℃; and the system operated continuously for 12 days.

[0089] (4) Detection: Regularly collect gas samples from the cathode chamber inlet / outlet to analyze the volume fraction of CO2 and CH4, collect catholyte samples to detect the acetic acid concentration, and simultaneously monitor the changes in ORP and voltage of the cathode / anode.

[0090] Experimental results are as follows Figure 4 As shown in Table 2, under the conditions of anodic coupling for organic solid waste hydrolysis and oxidation, the volume fraction of CO2 in the cathode chamber effluent significantly decreased with operating time. Statistical analysis over a 24-hour operating cycle showed that the volume fraction of CO2 in the effluent could drop below 5%, simultaneously producing acetic acid. The acetic acid concentration increased by approximately 3 g / L within a single cycle. According to the inorganic carbon conversion rate calculation method defined in this application (based on the removed CO2 and converted to the number of carbon moles for acetic acid), the inorganic carbon conversion rate was approximately 70%. These results indicate that the coupling system of this invention can simultaneously achieve biogas decarbonization and purification while converting CO2 into acetic acid products.

[0091] Table 2 Summary of the performance of cathode acetic acid synthesis and biogas decarbonization and purification (Examples 1-2 and Comparative Example 1)

[0092]

[0093] Note: "—" indicates not applicable or not measured; "not applicable" means that no corresponding evaluation index was set for this working condition, and "not measured" means that the index was not tested.

[0094] Example 3: Enhanced hydrolysis performance of anodic organic solid waste in a coupled system

[0095] This embodiment is used to verify the enhancing effect of anodic electrochemical-biological synergistic hydrolysis oxidation on the hydrolysis / dissolution conversion of organic solid waste, and to examine its synergistic relationship with low ORP inhibition of oxygen evolution.

[0096] (1) System construction: Construct a coupled system with the same structure as in Example 1. The system structure and connection relationships are as follows: Figure 1 Set up.

[0097] (2) Anode addition and inoculation: Add excess sludge to the anode chamber at a loading rate of 17.8 g VS / L; inoculate anaerobic granular sludge as a hydrolytic microbial system and start operation directly under power conditions.

[0098] (3) Electrochemical operation: The external electrochemical drive device operates in constant current mode with a current density of 5 A / m 2 The reaction temperature was 37 ℃; the pH was controlled at 6–7.5; and the reaction was carried out continuously for 2.5 days.

[0099] (4) ORP control: By adjusting the organic solid waste load and / or electrochemical driving conditions, the anolyte ORP is maintained below -100 mV (vs. Ag / AgCl).

[0100] (5) Testing: Collect anolyte samples regularly (e.g., every 6-12 hours) and analyze parameters such as SCOD, VFA concentration and pH.

[0101] Experimental results are as follows Figure 5 As shown in Table 3, under constant current drive, the hydrolysis and dissolution conversion of excess sludge in the anode chamber were enhanced: the peak SCOD reached 3.98 g / L, and the peak VFA reached 3.14 g / L, both significantly higher than those in Comparative Example 2 under open-circuit conditions (SCOD 1.32 g / L, VFA 0.571 g / L). Simultaneously, the ORP in the anode chamber remained below -100 mV with no significant oxygen evolution observed, which is beneficial for suppressing oxygen transmembrane migration and maintaining anaerobic stability at the cathode. This indicates that coupling the organic solid waste hydrolysis process with the anode reaction of the microbial electrosynthesis system can enhance hydrolysis acidification while suppressing oxygen evolution, providing more readily available substrates for subsequent anaerobic digestion and improving energy recovery efficiency.

[0102] Table 3 Summary of the enhanced effects of electrochemical-biological synergistic hydrolysis of anode organic solid waste (Example 3 and Comparative Example 2)

[0103]

[0104] Example 4: Verification of the gas production performance of anolyte hydrolysis products for subsequent anaerobic digestion

[0105] This embodiment is used to verify the gas production performance improvement effect of organic solid waste treated by anodic co-hydrolysis as an anaerobic digestion substrate.

[0106] (1) Feed preparation: The residual sludge after anodic hydrolysis treatment obtained in Example 3 was used as the anaerobic digestion feed.

[0107] (2) Inoculation and loading: Mix the feed with the anaerobic granular sludge at a mass ratio of 4:1 (based on wet weight) and add it to the anaerobic digestion reactor; the working volume of the reactor is 10 L.

[0108] (3) Anaerobic setup: After feeding, high-purity N2 is introduced into the reactor for 20 min to purge residual oxygen; after sealing, the digestion reaction begins.

[0109] (4) Operating conditions: The anaerobic digester was operated at a constant temperature of 37 ℃ and mixed by mechanical stirring at a speed of 120 r / min. A bicarbonate buffer system was used to maintain the pH of the reaction system at 7.0–7.8; when the pH deviated from the above range, an alkalinity regulator was added to adjust it. The anaerobic digestion reaction continued until the methanogenesis stage ended, or until 25 days of operation were completed.

[0110] (5) Gas production monitoring: A gas collection bag with a capacity of 5 L was connected to the headspace of the digester; gas samples were collected every 24 h, the gas production volume was measured and CH4 was analyzed. 4 / Components such as CO2.

[0111] Experimental results are as follows Figure 6 As shown in Table 4, the residual sludge after anodic coupling hydrolysis treatment exhibited a higher gas production rate and cumulative methane yield in the subsequent anaerobic digestion stage: the cumulative methane yield was 131.08 mL / gVS after 25 days of operation. added It increased by approximately 40% compared to Comparative Example 3 (Comparative Example: 93.63 mL / g VS). added The results showed that anodic coupling hydrolysis treatment can shorten the anaerobic digestion start-up time and improve substrate degradability, thereby improving methane production performance.

[0112] Table 4 Summary of subsequent anaerobic digestion gas production performance (Example 4 and Comparative Example 3)

[0113]

[0114] Note: "—" indicates not applicable or not measured; "not applicable" means that no corresponding evaluation index was set for this working condition, and "not measured" means that the index was not tested.

[0115] Comparative Example 1: Conventional MES system without introducing an anode organic solid waste coupling strategy

[0116] This comparative example is used to verify the cathodic acetic acid synthesis performance and ORP stability under the condition that no electrochemical-biological synergistic hydrolysis and oxidation strategy of organic solid waste is introduced at the anode and the anode reaction is mainly water oxidation and oxygen evolution. This comparative example serves as a control for Example 1, and the conditions are kept as consistent as possible except for the differences on the anode side.

[0117] (1) Constructing a conventional MES system: The reactor structure is the same as in Example 1 (membrane-separated double chamber). The volume of the cathode chamber and the anode chamber, the membrane type, the electrode material and the cathode seeding method are the same as in Example 1; no organic solid waste is added to the anode chamber.

[0118] (2) Establishing an anaerobic environment: Nitrogen gas (N2) is continuously purged into the cathode chamber for 20 min to replace the headspace gas and remove dissolved oxygen from the system; then high-purity carbon dioxide (CO2) is introduced into the cathode chamber as a carbon source. A conductive electrolyte solution is added to the anode chamber to improve the conductivity of the system, preferably a 50 mmol / L phosphate buffer solution (PBS).

[0119] (3) Electrochemical operation: The external electrochemical drive device operates in constant current mode with a current density of 5 A / m 2 The reaction temperature was 37 ℃; it was run continuously for 7 days; and the ORP in the anode and cathode chambers and the acetic acid production at the cathode were monitored regularly.

[0120] The ORP change in Comparative Example 1 is as follows Figure 7 As shown, since water oxidation is the primary process at the anode, the ORP in the anode chamber remains positive and shows an upward trend. Figure 7 (a) indicates that the oxygen evolution reaction continues and leads to an increase in the oxidizing power of the system; correspondingly, the ORP of the cathode chamber increases with operating time ( Figure 7 (b) and rose to about -240 mV (vs. Ag / AgCl) on day 6 of operation, which is a more positive shift than the cathode chamber ORP in Example 1, which remained stable at ≤-350 mV (vs. Ag / AgCl) in the later stage of operation, indicating that the cathodic reducing microenvironment was disrupted.

[0121] Under the above conditions, the cathodic acetic acid synthesis exhibited the following behavior: the acetic acid concentration reached a peak of approximately 1.2 g / L on day 4 of operation and then gradually decreased. Figure 8 The carbon utilization rate is less than 20% (based on acetic acid, Table 2), and the system stability is poor. Therefore, it is evident that traditional MES systems without an anode organic solid waste co-hydrolysis oxidation strategy struggle to suppress anode oxygen evolution and oxygen transmembrane migration, easily leading to cathode oxygen pollution, which in turn limits acetic acid synthesis efficiency and operational stability.

[0122] Comparative Example 2: Hydrolysis of Organic Solid Waste under Open Circuit Conditions

[0123] This comparative example is used to evaluate the dissolution and transformation effect of organic solid waste relying solely on microbial hydrolysis and acidification without the application of external electrochemical drive (system open circuit). This comparative example serves as a control for Example 3.

[0124] (1) Constructing the reaction system: Construct the same coupling system as in Example 3, but the external electrochemical drive device is not turned on, and the system remains open.

[0125] (2) Addition and operation: Add excess sludge to the anode chamber at a loading rate of 17.8 g VS / L; operate for 2.5 days under the same temperature, pH and stirring conditions as in Example 3.

[0126] (3) Detection: Collect anolyte samples regularly, analyze SCOD and VFA concentrations and record pH changes.

[0127] The comparison results are as follows Figure 5 As shown in Table 3, under open-circuit conditions, the sludge hydrolysis process mainly relies on microbial metabolism, resulting in low SCOD and VFA release rates: on day 2 of operation, SCOD and VFA were 1.32 g / L and 0.571 g / L, respectively, significantly lower than the corresponding values ​​(3.98 g / L and 3.14 g / L) under the electrocoupling conditions in Example 3. These results indicate that the externally applied electrochemical driving and anodic oxidation process plays a crucial role in enhancing the hydrolysis of organic solid waste and accelerating the conversion of macromolecular organic matter into soluble intermediates.

[0128] Comparative Example 3: Anaerobic Digestion Performance of Organic Solid Waste Without Anodic Hydrolysis Pretreatment

[0129] This comparative example is used to evaluate the gas production performance of raw organic solid waste that has not undergone anodic co-hydrolysis treatment during anaerobic digestion, serving as a control for Example 4.

[0130] (1) Feed: Organic solid waste that has not undergone any electrochemical hydrolysis treatment was selected as the anaerobic digestion feed, and its type and physicochemical properties were consistent with those of the organic solid waste used in Example 4.

[0131] (2) Inoculation and loading: Mix the original organic solid waste and anaerobic granular sludge at a mass ratio of 4:1 (the baseline is the same as in Example 4) and add it to the anaerobic digestion reactor; the reactor structure, effective volume and loading ratio are the same as in Example 4.

[0132] (3) Operation and monitoring: An anaerobic environment was established under the same conditions as in Example 4 and anaerobic digestion was carried out; gas samples were collected periodically to determine the gas production volume and gas composition.

[0133] The comparison results are as follows Figure 6 As shown in Table 4, compared to Example 4, the untreated organic solid waste exhibited a longer start-up lag period and a lower gas production rate in the early stages of anaerobic digestion, with a cumulative methane production of 93.63 mL / g. addedThis demonstrates that the degree of hydrolysis of macromolecular organic matter in the original organic solid waste has a significant impact on the overall performance of anaerobic digestion. This comparative example further verifies the technical advantages of the anodic coupling hydrolysis treatment described in this invention in improving anaerobic digestion efficiency.

[0134] The above description is merely a preferred embodiment of the present invention, used to illustrate the technical solution and beneficial effects of the present invention, and does not constitute a limitation on the scope of protection of the present invention. Those skilled in the art should understand that, without departing from the concept of the present invention, the system configuration and unit integration method (including but not limited to the parallel / series connection of reactor modules, the connection method of material and gas circuits), the form of key components (including but not limited to the type of ion exchange membrane, the material and geometry of the cathode / anode electrode, and the mass transfer enhancement structure), and the operation control strategy (including but not limited to the electrochemical drive mode, ORP control method, solid waste addition load, temperature and pH control, and gas introduction / circulation method) can be replaced, modified, or equivalently improved; where there is no contradiction, the technical features described in the various embodiments and comparative examples can also be combined with each other, and all should fall within the scope of protection defined by the claims of the present invention.

[0135] Unless otherwise expressly defined, the numerical ranges described in this specification include their endpoint values ​​and are intended to cover any subranges within that range; expressions such as “preferred,” “optional,” and “for example” are used for illustration and example only to facilitate understanding and implementation by those skilled in the art and do not necessarily constitute a limitation on the scope of protection of the claims.

Claims

1. A microbial electrosynthesis-enhanced solid waste hydrolysis and anaerobic digestion biogas high-value utilization system, characterized in that, It includes a microbial electrosynthesis reactor, an external electrochemical drive device, an anaerobic digestion unit, and its supporting hydrolysis product flow path, biogas delivery pipeline, and gas circulation device; The microbial electrosynthesis reactor includes a cathode chamber and an anode chamber separated by an ion exchange membrane; The cathode chamber is equipped with a cathode electrode and an anaerobic acetic acid-producing microbial system, and the cathode chamber is equipped with an air inlet and an air outlet; The anode chamber contains an anode electrode, organic solid waste, and a hydrolytic microbial system capable of synergistic oxygen consumption. The anode chamber also contains an organic solid waste inlet and a hydrolysis product outlet. The cathode electrode and the anode electrode are electrically connected to form a circuit via the external electrochemical drive device, allowing electrons released from the anode reaction to be transmitted to the cathode via the external circuit. The anaerobic digestion unit is equipped with a feed inlet and a biogas outlet; The hydrolysis product flow path connects the hydrolysis product outlet to the feed inlet of the anaerobic digestion unit, so that the hydrolysis products in the anode chamber enter the anaerobic digestion unit for anaerobic digestion to produce biogas. The biogas delivery pipeline connects the biogas outlet of the anaerobic digestion unit to the air inlet of the cathode chamber, so that the biogas enters the cathode chamber and, under anaerobic conditions, the carbon dioxide in it is reduced to acetic acid by the anaerobic acetic acid-producing microbial system. The carbon dioxide-enriched gas after decarbonization and purification is discharged from the air outlet of the cathode chamber. The air inlet of the cathode chamber is connected not only to the biogas outlet of the anaerobic digestion unit, but also to an external carbon dioxide gas source. The external carbon dioxide gas source is one or more of simulated biogas, carbon dioxide gas, or industrial exhaust gas, wherein the volume fraction of carbon dioxide is 10% to 100%. The air inlet of the cathode chamber is connected to the gas circulation device to realize the circulation or recirculation of the air phase at the top of the cathode chamber, thereby enhancing carbon dioxide mass transfer and increasing the decarbonization rate. The anode chamber undergoes an electrochemical-biological synergistic hydrolysis and oxidation reaction of organic solid waste under external electrochemical drive to suppress the oxygen evolution reaction of water and reduce the transmembrane migration of oxygen to the cathode chamber. Furthermore, by controlling at least one of the organic solid waste addition load and external electrochemical drive conditions, the redox potential of the liquid phase in the anode chamber is maintained below -100mV (with Ag / AgCl as a reference) to further suppress the oxygen evolution reaction and reduce oxygen transmembrane migration.

2. The system according to claim 1, characterized in that, The ion exchange membrane is any one of a cation exchange membrane, anion exchange membrane, bipolar membrane, or proton exchange membrane.

3. The system according to claim 1, characterized in that, The anaerobic acetic acid-producing microbial system comprises an anaerobic autotrophic bacterial community with acetic acid as the main product, and the bacterial community is selected from... Acetobacterium genus, Clostridium genus, Sporomusa The genera and their combinations may be microbial communities enriched on the cathode side of a long-term stable microbial electrosynthesis reactor.

4. The system according to claim 1, characterized in that, The organic solid waste is residual sludge, primary sludge, kitchen waste, livestock and poultry manure, straw, garden waste or a combination thereof; the addition load of the organic solid waste is 5 to 30 g VS / L, calculated in terms of volatile solids (VS).

5. The system according to claim 1, characterized in that, The external electrochemical drive device operates in constant current or constant voltage mode; in constant current mode, the current density is 1 to 20 A / m².

6. A method for operating the system according to any one of claims 1 to 5, characterized in that, Includes the following steps: a) Add organic solid waste to the anode chamber and inoculate it with a hydrolytic microbial system; b) Inoculate the cathode chamber with an anaerobic acetic acid-producing microbial system and establish anaerobic operating conditions; c) Apply external electrochemical driving conditions to cause an electrochemical-biological synergistic hydrolysis-oxidation reaction in the anode chamber and provide electrons to the cathode; d) The hydrolysis products from the anode chamber are transported to the anaerobic digestion unit via the hydrolysis product flow path for anaerobic digestion to produce biogas; e) The biogas is introduced into the cathode chamber through the biogas delivery pipeline, so that the carbon dioxide in the cathode is reduced to acetic acid and the decarbonized and purified methane-enriched gas is output.

7. The method according to claim 6, characterized in that, By adjusting at least one of the organic solid waste addition load and the external electrochemical driving conditions, the redox potential of the liquid phase in the anode chamber is maintained between -100 mV and -400 mV (with Ag / AgCl as a reference).

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