Sludge compost in-situ trapping and mineralization carbon sequestration method

Abstract

The invention relates to the technical field of environmental engineering and resource recycling, and provides a sludge compost in-situ capture and mineralization carbon sequestration method, which comprises the following steps: mixing red mud and serpentine powder, humidifying, dehydrating after humidifying, and optimizing the particle size; then performing high-temperature activation to form a primary pore structure; then carrying out chemical modification and vacuum filtration to obtain a modified porous adsorption material; carbonate sedimentary bacteria are adopted as target strains, the target strains are subjected to propagation expanding treatment, and high-density bacterial liquid is formed; soaking the modified porous adsorption material in a high-density bacterial liquid, and loading microorganisms; allowing the microorganism-loaded modified porous adsorption material to stand to form a negative carbon capture material; the negative carbon capture material and sludge compost are mixed in proportion and then stacked into a pile body, CO2 in the sludge compost is captured and fixed through the negative carbon capture material, and meanwhile the sludge compost is catalyzed to generate carbonate. The composting efficiency and humification level can be remarkably improved, the additional value of compost products is improved, and the recycling application range is expanded.

Description

Technical Field

[0001] The invention relates to the technical field of environmental engineering and resource recycling, and in particular to a method for in-situ capture and mineralization carbon fixation of sludge composting. Background Art

[0002] Aerobic composting of sludge is a commonly used resource processing technology. Through the aerobic metabolism of microorganisms, the organic matter in the sludge is decomposed into humus and carbon dioxide (CO2) to achieve sludge volume reduction and stabilization treatment. However, the existing composting process has a significant carbon emission problem. According to research, during the composting process, the conversion rate of organic carbon (Total Organic Carbon, TOC) in the sludge is high, of which about 60% to 70% of the organic carbon is eventually emitted into the atmosphere in the form of CO2. This carbon loss not only exacerbates greenhouse gas emissions, but also causes a huge waste of resources.

[0003] The emission of CO2 during the composting process is mainly concentrated in the high temperature stage (55-65°C), when the microbial activity is strong and the decomposition rate is fast. The large-scale degradation of organic carbon directly leads to a significant increase in the CO2 concentration in the compost. However, the research and design of existing composting processes mainly focus on composting efficiency and emission control of odorous gases (such as ammonia). Only a few processes attempt to manage CO2 emissions during the composting process, and most of them remain in the terminal treatment stage, usually achieved through tail gas capture. Although tail gas capture can reduce CO2 emissions to a certain extent, it has limitations such as low efficiency, complex process, and insufficient resource utilization, making it difficult to apply to process sites.

[0004] In order to reduce the emission of other polluting gases, some technologies try to add modified adsorbent materials (such as zeolite, bentonite) to adsorb ammonia or inhibit the production of methane (CH4) and nitrous oxide (N2O). However, these materials have limited CO2 capture capacity and mainly play a physical adsorption role, making it difficult to achieve effective fixation of carbon dioxide. At the same time, some composting processes have introduced functional microorganisms (such as methane oxidizing bacteria and nitrifying bacteria) to optimize the composting environment, but these studies have mostly focused on a single goal and have not yet formed a complete technical system for the synergy of CO2 capture and mineralization.

[0005] Although the existing sludge aerobic composting technology has achieved certain application results in resource utilization, it still has the following significant defects in carbon dioxide (CO2) emission control, resource utilization and compost product quality:

[0006] (1) High carbon emissions and serious waste of carbon resources

[0007] During the sludge composting process, microorganisms decompose the organic carbon in the sludge into carbon dioxide (CO2) through metabolism. Studies have shown that about 60% to 70% of the organic carbon in the composting process is eventually released into the atmosphere in the form of CO2, resulting in a serious waste of carbon resources. This high proportion of carbon emissions not only creates greenhouse gas pressure on the environment, but also fails to effectively convert and utilize the released CO2. The existing technology has not yet developed a technical path that can capture CO2 during the composting process and convert it into high-value-added solid carbonates (such as magnesium carbonate and calcium carbonate), and the efficiency of resource utilization needs to be improved urgently.

[0008] (2) Lack of source control, unable to achieve real-time capture and fixation of CO2

[0009] The management of CO2 in existing composting processes is mainly focused on end-of-pipe treatment, where the CO2 released in the later stages of composting is treated by tail gas capture devices. This control method has significant lags and is difficult to cover the high-emission period during the high-temperature stage of composting (55-65°C). In addition, the existing process lacks real-time monitoring and precise control of the gas generation, diffusion, and emission processes inside the pile. CO2 is diffused and emitted into the atmosphere in a disorderly manner after it is generated, and the source control capability is seriously insufficient. The lack of technical means to combine the synergistic effects of adsorption materials and microorganisms makes it impossible for the CO2 in the pile to be converted in situ into stable solid mineral compounds (such as magnesium carbonate or calcium carbonate), further limiting the carbon negative emission targets of the composting process.

[0010] (3) Low tail gas collection efficiency, complex CO2 capture process and high cost

[0011] Tail gas capture technology requires the additional configuration of complex equipment, such as gas adsorption towers, membrane separation systems or chemical absorption devices. This type of technology is highly dependent on equipment, complex to operate and has high energy consumption, resulting in a significant increase in overall operating costs. In addition, although existing adsorption materials (such as bentonite and zeolite) have a certain adsorption effect on ammonia (NH3) and methane (CH4), their adsorption efficiency is low in CO2 capture and cannot meet the needs of industrial applications. Due to the large consumption and limited service life of these materials, the operating costs are further increased. The maintenance and energy consumption of tail gas capture equipment account for a large proportion of the overall composting cost, which limits the economic feasibility and market promotion of existing technologies.

[0012] (4) Low quality of compost, unstable quality, and poor market applicability

[0013] The quality of fertilizer products produced by existing sludge composting technology fluctuates greatly and is difficult to meet market demand. The humification level of compost products is low, the nutrient content (such as total nitrogen, total phosphorus, and total potassium) is unstable, and the fertilizer effect is poor in durability. In addition, heavy metal pollutants are not fully passivated during the composting process, which may pose an ecological risk to long-term soil application. The physical properties of compost products (such as water retention and looseness) are also poor, and the convenience of application is insufficient, which limits its application potential in greening fertilizers and soil conditioners. If the CO2 released by composting can be converted into magnesium carbonate or calcium carbonate, it can significantly improve the physical and chemical properties of the compost products and enhance their market value. For example, magnesium carbonate and calcium carbonate can neutralize acidic soils, fix heavy metals, increase soil nutrient content and promote soil microbial activity in agriculture and ecological restoration, and have a wide range of applicability. However, the existing technology has not yet combined CO2 capture with compost quality improvement, missing the opportunity for product added value development and market application. Summary of the invention

[0014] The object of the present invention is to solve at least one technical problem in the background technology and to provide a method for in-situ capture and mineralization carbon fixation of sludge composting.

[0015] To achieve the above object, the present invention provides a method for in-situ capture and mineralization carbon fixation of sludge composting, comprising:

[0016] The red mud and serpentine powder are mixed in proportion, and then deionized water is added to adjust the humidity, and then dehydrated, and then ball milled and screened to optimize the particle size;

[0017] The mixture after optimizing particle size is activated at high temperature to form a preliminary pore structure;

[0018] The mixture with the preliminary pore structure is chemically modified by an acetic acid solution, and then vacuum filtered. During the filtration process, the mixture is repeatedly washed with deionized water until the filtrate is neutral, and then dried to obtain a modified porous adsorption material.

[0019] Carbonate-depositing bacteria are used as target bacteria, and the target bacteria are propagated and concentrated by centrifugation to form a high-density bacterial solution.

[0020] Soaking the modified porous adsorbent material in the high-density bacterial solution, and then driving the microorganisms in the high-density bacterial solution to penetrate and be loaded inside the modified porous adsorbent material by a vacuum filtration method;

[0021] The modified porous adsorption material loaded with microorganisms forms a negative carbon capture material with a microorganism attachment layer after static cultivation;

[0022] The sludge and auxiliary materials are mixed in proportion to form sludge compost, and the negative carbon capture material is mixed with the sludge compost in proportion and then piled into a pile. The negative carbon capture material captures and fixes CO2 in the sludge compost and catalyzes the sludge compost to generate carbonate.

[0023] According to one aspect of the present invention, the red mud and serpentine powder are mixed in proportion, deionized water is added to adjust the humidity, dehydrated after the humidity adjustment, and ball milled and screened to optimize the particle size after dehydration, including:

[0024] The red mud and serpentine powder were mixed in a mass ratio of 3:1, and then 10% by mass of deionized water was added for wetting and blending to make the red mud and serpentine powder evenly dispersed;

[0025] The humidified mixture is dried in a vacuum drying oven at 105°C until the moisture content is less than 10%;

[0026] The dehydrated mixture was placed in a high-energy ball mill for grinding, with the ball-to-material ratio set at 10:1 and the ball mill speed at 500 r / min. -1 , and continue for 3 hours to control the particle size within the range of 50 μm, and then filter through a sieve with a mesh diameter of 50 μm to obtain a mixture with optimized particle size.

[0027] According to one aspect of the present invention, the mixture after optimizing the particle size is activated at high temperature to form a preliminary pore structure as follows:

[0028] The mixture after optimizing the particle size is subjected to a high temperature heat treatment at 500-700° C. to activate the CaO and MgO components therein and form a preliminary pore structure.

[0029] According to one aspect of the present invention, the mixture having a preliminary pore structure is chemically modified by an acetic acid solution, vacuum filtered after modification, and repeatedly washed with deionized water during the filtration process until the filtrate is neutral and then dried to obtain a modified porous adsorption material, comprising:

[0030] Add 0.2-0.5 mol·L -1 acetic acid solution, mixed at a solid-liquid ratio of 1:5, and stirred at 50°C for 3h to obtain a modified material;

[0031] The modified material was filtered through a vacuum filtration device, and during the filtration process, it was repeatedly washed with deionized water until the filtrate was neutral. The material was then dried at 105° C. to a constant weight to obtain a modified porous adsorption material.

[0032] According to one aspect of the present invention, the carbonate-depositing bacteria are used as target bacteria, the target bacteria are propagated, and after propagation, a high-density bacterial solution is formed by centrifugation and concentration, which includes:

[0033] The target strain was propagated by liquid fermentation in LB medium at 30-35°C and 120 r / min. -1 Shake culture for 48 hours, expand to a bacterial concentration of 10 9 CFU·mL -1 ;

[0034] The culture solution after propagation was concentrated by centrifugation to obtain a culture solution concentration of 10 11 CFU·mL -1 High-density bacterial liquid.

[0035] According to one aspect of the present invention, the modified porous adsorbent material is immersed in the high-density bacterial solution, and then the microorganisms in the high-density bacterial solution are driven to penetrate and be loaded inside the modified porous adsorbent material by a vacuum filtration method, comprising:

[0036] The high-density bacterial solution was mixed with the modified porous adsorption material at a liquid-to-solid ratio of 10:1;

[0037] Vacuum filtration technology was used to drive the microorganisms in the high-density bacterial solution to penetrate and load into the modified porous adsorption material through a vacuum degree of 0.1 MPa. The filtration loading time was 10 minutes.

[0038] According to one aspect of the present invention, the modified porous adsorption material loaded with microorganisms forms a negative carbon capture material having a microorganism attachment layer after static culture:

[0039] The modified porous adsorption material loaded with microorganisms is statically cultured at 30 to 35° C. for 12 to 24 hours to form a negative carbon capture material with a stable microorganism attachment layer.

[0040] According to one aspect of the present invention, the sludge and auxiliary materials are mixed in proportion to form sludge compost, the negative carbon capture material and the sludge compost are mixed in proportion and then piled into a pile, the negative carbon capture material is used to capture and fix CO2 in the sludge compost, and the sludge compost is catalyzed to generate carbonate, including:

[0041] The sludge and auxiliary materials are mixed in a mass ratio of 3:1, the carbon-nitrogen ratio is adjusted to 30:1, and the initial moisture content is controlled at 60% to 65% to form sludge compost;

[0042] The negative carbon capture material is uniformly mixed into the sludge compost at a rate of 2% to 5% of the dry weight of the sludge compost and then piled into a pile;

[0043] The temperature of the pile is maintained at 55-65°C and the humidity is maintained at 40%-50%. The CO2 in the sludge compost is captured and fixed by negative carbon capture materials, while the sludge compost is catalyzed to generate carbonates.

[0044] According to the scheme of the present invention, the present invention aims at the problems of high carbon emission, large waste of resources, low process efficiency, unstable product quality, etc. of the existing sludge composting technology, and proposes a sludge composting in-situ capture and mineralization carbon fixation method based on the synergistic effect of carbon dioxide adsorption and carbonic anhydrase microorganisms. Through the synergistic effect of porous adsorption materials and carbonic anhydrase microorganisms, the carbon fixation capacity, process efficiency and product added value of the composting process are significantly improved. Therefore, compared with the prior art, the method of the present invention has the following significant advantages:

[0045] 1. Achieve carbon negative emissions;

[0046] In traditional composting processes, 60% to 70% of sludge organic carbon is eventually released into the atmosphere in the form of carbon dioxide, which not only causes high carbon emissions, but also wastes carbon resources. The present invention uses the synergistic technology of porous adsorption materials and carbonic anhydrase microorganisms to capture the CO2 released during the composting process at the source, and mineralizes and fixes it into calcium carbonate and magnesium carbonate, with a carbon fixation efficiency of 30% to 50%. This technology achieves negative carbon emissions throughout the entire composting process, providing an effective path for the low-carbon development of sludge treatment technology.

[0047] 2. Significantly improve composting efficiency and humification level;

[0048] The present invention effectively accelerates the decomposition and humification of organic matter by optimizing the use of negative carbon capture materials and composting process parameters. While capturing CO2, the material adjusts the carbon-nitrogen balance of the pile, providing an optimal environment for microbial metabolic activities. The humification rate is increased by 20%-30%, the duration of the high temperature stage (55-65°C) is extended, and the overall composting cycle is shortened by 15%-20%. This improvement not only improves composting efficiency and reduces energy consumption, but also improves the stability and fertilizer value of the product.

[0049] 3. Increase the added value of compost products and expand the scope of resource application;

[0050] The present invention significantly improves the physical and chemical properties and ecological safety of compost products, and increases their application value in the fields of agriculture and ecological restoration: Nutrient optimization: The total nitrogen, total phosphorus, and total potassium nutrient content increases by 10% to 15%, the humus content is significantly improved, and the fertilizer effect of the product is more lasting. Heavy metal safety: Heavy metals are passivated through the mineralization process, and mobility is reduced by 30% to 50%. The product meets the environmental protection standards for long-term application. Physical property optimization: The moisture content of the compost product is controlled below 40%, and the looseness and water holding capacity are increased by 15% to 25%, which is more suitable for landscaping and agricultural application. The compost product is suitable for use as greening fertilizer, soil conditioner and ecological restoration material, with broad market demand, opening up a new growth point for resource utilization.

[0051] 4. The process is simple and efficient, with broad industrial prospects;

[0052] The process path of the present invention is clear, and the key technology is based on mature processes, which has significant practicality and economy. The porous adsorption material uses red mud as the main raw material, which is low-cost and widely available; the microbial load is completed by vacuum filtration technology, which is easy to operate and has low equipment requirements. The overall process has a high degree of modularization and can be directly embedded in existing sludge treatment facilities. It is suitable for large-scale industrial promotion, with significant technical and economic advantages, which can effectively reduce treatment costs and enhance the competitiveness of the sludge treatment industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The flowchart schematically shows a method for in-situ carbon capture and mineralization through sludge composting according to one embodiment of the present invention. DETAILED DESCRIPTION

[0054] The present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only to enable those skilled in the art to better understand and thus implement the present invention, rather than implying any limitation on the scope of the present invention.

[0055] As used herein, the term "including" and variations thereof are to be interpreted as open-ended terms meaning "including, but not limited to." The term "based on" is to be interpreted as "based, at least in part, on." The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment."

[0056] Figure 1 The flowchart schematically shows a method for in-situ capture and mineralization carbon fixation of sludge composting according to an embodiment of the present invention. Figure 1 As shown, in this embodiment, the sludge composting in-situ capture and mineralization carbon fixation method includes:

[0057] The red mud and serpentine powder are mixed in proportion, and then deionized water is added to adjust the humidity, and then dehydrated, and then ball milled and screened to optimize the particle size;

[0058] The mixture after optimizing particle size is activated at high temperature to form a preliminary pore structure;

[0059] The mixture with the preliminary pore structure is chemically modified by an acetic acid solution, and then vacuum filtered. During the filtration process, the mixture is repeatedly washed with deionized water until the filtrate is neutral, and then dried to obtain a modified porous adsorption material.

[0060] Carbonate-depositing bacteria are used as target bacteria, and the target bacteria are propagated and concentrated by centrifugation to form a high-density bacterial solution.

[0061] Soaking the modified porous adsorbent material in the high-density bacterial solution, and then driving the microorganisms in the high-density bacterial solution to penetrate and be loaded inside the modified porous adsorbent material by a vacuum filtration method;

[0062] The modified porous adsorption material loaded with microorganisms forms a negative carbon capture material with a microorganism attachment layer after static cultivation;

[0063] The sludge and auxiliary materials are mixed in proportion to form sludge compost, and the negative carbon capture material is mixed with the sludge compost in proportion and then piled into a pile. The negative carbon capture material captures and fixes CO2 in the sludge compost and catalyzes the sludge compost to generate carbonate.

[0064] Further, according to one embodiment of the present invention, red mud and serpentine powder are mixed in proportion, deionized water is added to adjust the humidity, the mixture is dehydrated after the humidity adjustment, and the particle size is optimized by ball milling and screening after dehydration, including:

[0065] The red mud and serpentine powder were mixed in a mass ratio of 3:1, and then 10% by mass of deionized water was added for wetting and blending to make the red mud and serpentine powder evenly dispersed;

[0066] The humidified mixture is dried in a vacuum drying oven at 105°C until the moisture content is less than 10% to ensure the stability of subsequent processing;

[0067] The dehydrated mixture was placed in a high-energy ball mill for grinding, with the ball-to-material ratio set at 10:1 and the ball mill speed at 500 r / min. -1 , and continue for 3 hours to control the particle size within the range of 50 μm, and then filter through a sieve with a mesh diameter of 50 μm to obtain a mixture with optimized particle size.

[0068] Further, according to one embodiment of the present invention, the mixture after optimizing the particle size is activated at high temperature to form a preliminary pore structure as follows:

[0069] The mixture after optimizing the particle size is subjected to a high temperature heat treatment at 500-700° C. to activate the CaO and MgO components therein and form a preliminary pore structure.

[0070] Further, according to one embodiment of the present invention, the mixture with a preliminary pore structure is chemically modified by an acetic acid solution, vacuum filtered after modification, and repeatedly washed with deionized water during the filtration process until the filtrate is neutral and then dried to obtain a modified porous adsorption material, comprising:

[0071] Add 0.2-0.5 mol·L -1 In acetic acid solution, the solid-liquid ratio is 1:5 (g·mL -1) and stirred at 50°C for 3 hours to obtain a modified material; this process enhances the material surface's ability to adsorb CO2 through chemical modification, that is, the chelation of acetic acid is used to remove surface impurities and generate active sites, thereby significantly improving the material's ability to adsorb carbon dioxide. The specific surface area of ​​the modified material reaches 100-150m 2 ·g -1 , the pore size distribution is ≤10μm, providing an ideal structural and performance basis for microbial loading.

[0072] The modified material was filtered through a vacuum filtration device, and during the filtration process, it was repeatedly washed with deionized water until the filtrate was neutral. The material was then dried at 105° C. to a constant weight to obtain a modified porous adsorption material.

[0073] Further, according to one embodiment of the present invention, carbonate depositing bacteria (Sporosarcina pasteurii) is used as a target bacterial species (functional microorganism), and the target bacterial species is subjected to a propagation treatment, and after propagation, a high-density bacterial solution is formed by centrifugation and concentration, including:

[0074] The target strain was propagated by liquid fermentation in LB medium (10 g L -1 Tryptone, 5 g L -1 Yeast powder, 10g·L -1 Sodium chloride, pH 7.0) at 30-35°C and 120 r / min -1 Shake culture for 48 hours, expand to a bacterial concentration of 10 9 CFU·mL -1 ;

[0075] The culture solution after propagation was concentrated by centrifugation to obtain a culture solution concentration of 10 11 CFU·mL -1 High-density bacterial liquid.

[0076] In this embodiment, the carbonate-depositing bacteria can efficiently produce carbonic anhydrase, catalyze carbon dioxide and water to generate carbonic acid (H2CO3), and generate stable carbonates by reacting with calcium and magnesium ions.

[0077] Further, according to one embodiment of the present invention, the modified porous adsorbent material is immersed in a high-density bacterial solution, and then the microorganisms in the high-density bacterial solution are driven to penetrate and load inside the modified porous adsorbent material by a vacuum filtration method, comprising:

[0078] The high-density bacterial solution and the modified porous adsorption material were mixed at a liquid-to-solid ratio of 10:1 (mL g -1 )mix;

[0079] Vacuum filtration technology is used to drive the microorganisms in the high-density bacterial liquid to penetrate and load into the modified porous adsorption material through a vacuum degree of 0.1 MPa. The filtration loading time is 10 minutes to ensure that the microorganisms are efficiently attached to the material.

[0080] Further, according to one embodiment of the present invention, the modified porous adsorption material loaded with microorganisms is subjected to static culture to form a negative carbon capture material having a microorganism attachment layer:

[0081] The modified porous adsorption material loaded with microorganisms is placed in a static culture environment at 30-35°C for 12-24 hours to avoid high temperature damage to the activity of microorganisms, forming a negative carbon capture material with a stable microbial attachment layer. The negative carbon capture material contains 10 active microorganisms. 8 CFU·g -1 .

[0082] In this embodiment, the functional material (negative carbon capture material) has good catalytic activity and thermal stability in composting high temperature (50-75°C) and weak alkaline environment (pH 6.5-8.5), and can sustainably capture carbon dioxide and mineralize it into calcium carbonate (CaCO3) or magnesium carbonate (MgCO3).

[0083] Further, according to an embodiment of the present invention, sludge and auxiliary materials are mixed in proportion to form sludge compost, negative carbon capture materials are mixed with the sludge compost in proportion and then piled into a pile, CO2 in the sludge compost is captured and fixed by the negative carbon capture materials, and the sludge compost is catalyzed to generate carbonate, including:

[0084] Mix the sludge and auxiliary materials (such as garden waste, straw, sawdust) in a mass ratio of 3:1, adjust the carbon-nitrogen ratio to 30:1, and control the initial moisture content at 60% to 65% to form sludge compost to ensure the optimal activity conditions of microorganisms in the initial stage of composting;

[0085] The negative carbon capture material is uniformly mixed into the sludge compost at 2% to 5% of the dry weight of the sludge compost and then piled into a pile; in this embodiment, the mixed materials are piled into a pile with a height of 1.2m, which is suitable for windrow or trough composting process;

[0086] The temperature of the pile is maintained at 55-65°C and the humidity is maintained at 40%-50%. The CO2 in the sludge compost is captured and fixed by negative carbon capture materials, while the sludge compost is catalyzed to generate carbonates.

[0087] In this embodiment, the high temperature stage of composting (50-65°C) is the main period of CO2 release. The negative carbon capture material fully absorbs CO2 and reacts with magnesium and calcium ions in the material through microbial catalysis to generate stable magnesium carbonate and calcium carbonate. The capture rate can reach more than 80%, and the generated carbonate accounts for 10% to 15% of the mass of the compost product. In the mature stage, the ventilation rate is appropriately reduced to further stabilize the environmental conditions in the pile, optimize the mineralization of carbonates, and ensure that the final moisture content of the compost product is less than 40%. The use of capture materials not only achieves CO2 capture and fixation, but also optimizes the physical and chemical properties of the compost product through the generated carbonates.

[0088] In this embodiment, the composting process uses an intelligent sensor system to monitor the temperature (55-65°C), humidity (40%-50%) and carbon dioxide concentration of the compost in real time, and adjusts the ventilation rate (12m / s in the high temperature stage) in combination with a dynamic control system. 3 ·h -1 ·t -1 ), ensuring efficient oxygen supply and carbon dioxide capture in the compost. The carbon dioxide released during the composting process is captured by negative carbon capture materials and mineralized into carbonates through the following reactions:

[0089] CO2+H2O→H2CO3;

[0090] H2CO3+Ca 2+ →CaCO3↓;

[0091] H2CO3+Mg 2+ →MgCO3↓.

[0092] The carbon fixation efficiency of the mineralization reaction can reach 30% to 50%, and the generated carbonates are stably stored in the compost products, significantly increasing the inorganic carbon content and long-term stability of the compost products.

[0093] The final compost product has excellent performance: the humification rate is increased by 20% to 30%, the nutrient content (total nitrogen, total phosphorus, total potassium) is increased by 10% to 15%, the heavy metal mobility is reduced by 30% to 50%, the moisture content is controlled below 40%, and it has good looseness and water retention. This product is widely used in greening fertilizers, soil conditioners and ecological restoration projects, with both environmental benefits and economic value.

[0094] According to the above scheme of the present invention, the present invention realizes the direct capture and in-situ fixation of CO2 in the composting process by the synergistic application of porous adsorbent material and carbonic anhydrase functional microorganisms, combined with dynamic regulation and in-situ mineralization capture scheme. The technology adsorbs the CO2 released in the composting process by porous adsorbent material, and under the catalytic action of carbonic anhydrase, reacts with the alkaline minerals in the material to generate stable solid carbonates (such as magnesium carbonate and calcium carbonate). This in-situ mineralization process not only effectively reduces the carbon emission of composting technology, but also realizes CO2 resource utilization, and improves the humification level and ecological safety of compost products.

[0095] The present invention achieves carbon negative emissions from composting by capturing CO2 at the source and converting it in situ, optimizes composting efficiency through dynamic regulation, and improves the quality of compost products through the synergistic effect of porous adsorption materials and microorganisms. Specifically, while reducing carbon emissions, this technology significantly improves the nutrient stability of compost products (such as an increase of 10% to 15% in total nitrogen, total phosphorus, and total potassium content), humification level (increased by 20% to 30%), and heavy metal passivation ability (mobility reduced by 30% to 50%). These improvements have greatly increased the market application value of compost products in the fields of agriculture, horticulture, and soil remediation.

[0096] Through the present invention, the core technology of sludge composting process has been fully optimized. It not only realizes the reduction of sludge treatment, but also opens up a new technical path in carbon emission reduction and resource utilization, provides a low-carbon, high-efficiency and high-value-added solution for the sludge treatment industry, and significantly improves the competitiveness of the industry.

[0097] According to the above scheme of the present invention, the present invention realizes the in-situ capture and mineralization fixation of CO2 during the composting process through innovative negative carbon capture materials, breaking through the limitations of traditional tail gas capture. The porous adsorption material directly adsorbs the released CO2 during the composting process, and catalyzes the reaction with minerals (such as magnesium and calcium ions) in the material through the loaded carbonic anhydrase functional microorganisms to generate stable solid magnesium carbonate and calcium carbonate. This in-situ capture and fixation method effectively avoids the high cost and complex process of tail gas treatment, while significantly reducing the carbon emissions of composting. The CO2 capture rate can reach more than 80%, providing an efficient and low-carbon solution for sludge composting process.

[0098] The negative carbon capture material of the present invention has both high adsorption performance and catalytic ability. It mainly uses industrial by-products such as red mud and serpentine powder as raw materials, prepares porous adsorption materials through processes such as ball milling, chemical modification and vacuum filtration, and loads carbonic anhydrase functional microorganisms to achieve the dual functions of adsorption and conversion of the material. This material not only has a high capture efficiency for CO2, and the generated solid carbonate accounts for 10% to 15% of the mass of the compost product, but also has a significant passivation effect on heavy metals in the compost product (mobility is reduced by 30% to 50%). At the same time, the material preparation process is green and low-cost, which greatly improves the economic feasibility of the technology and provides a new way for the high-value utilization of industrial by-products.

[0099] The present invention captures and fixes the CO2 released during the composting process and converts it into magnesium carbonate and calcium carbonate, which not only achieves efficient utilization of carbon resources, but also significantly improves the quality and market value of the compost products. The humification level of the compost product is increased by 20% to 30%, the nutrient content of total nitrogen, total phosphorus, total potassium, etc. is increased by 10% to 15%, the water-soluble organic matter content is increased by 15% to 20%, and the mobility of heavy metals is reduced by 30% to 50%, ensuring the ecological safety of long-term application. The modified compost product is more suitable for scenarios such as agriculture, gardening and soil remediation, providing higher added value for the market expansion of sludge compost products.

[0100] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for in-situ capture and mineralization carbon fixation by sludge composting, characterized in that: include: The red mud and serpentine powder are mixed in proportion, and then deionized water is added to adjust the humidity, and then dehydrated, and then ball milled and screened to optimize the particle size; The mixture after optimizing particle size is activated at high temperature to form a preliminary pore structure; The mixture with the preliminary pore structure is chemically modified by an acetic acid solution, and then vacuum filtered. During the filtration process, the mixture is repeatedly washed with deionized water until the filtrate is neutral, and then dried to obtain a modified porous adsorption material. Carbonate-depositing bacteria are used as target bacteria, and the target bacteria are propagated and concentrated by centrifugation to form a high-density bacterial solution. Soaking the modified porous adsorbent material in the high-density bacterial solution, and then driving the microorganisms in the high-density bacterial solution to penetrate and be loaded inside the modified porous adsorbent material by a vacuum filtration method; The modified porous adsorption material loaded with microorganisms forms a negative carbon capture material with a microorganism attachment layer after static cultivation; The sludge and auxiliary materials are mixed in proportion to form sludge compost, and the negative carbon capture material is mixed with the sludge compost in proportion and then piled into a pile. The negative carbon capture material captures and fixes CO2 in the sludge compost and catalyzes the sludge compost to generate carbonate.

2. The method for in-situ capture and mineralization carbon fixation by sludge composting according to claim 1, characterized in that: The red mud and serpentine powder are mixed in proportion, and then deionized water is added to adjust the humidity, and then dehydrated, and then ball milled and screened to optimize the particle size, including: The red mud and serpentine powder were mixed in a mass ratio of 3:1, and then 10% by mass of deionized water was added for wetting and blending to make the red mud and serpentine powder evenly dispersed; The humidified mixture is dried in a vacuum drying oven at 105°C until the moisture content is less than 10%; The dehydrated mixture was placed in a high-energy ball mill for grinding, with the ball-to-material ratio set at 10:1 and the ball mill speed at 500 r / min. -1 , and continue for 3 hours to control the particle size within the range of 50 μm, and then filter through a sieve with a mesh diameter of 50 μm to obtain a mixture with optimized particle size.

3. The method for in-situ capture and mineralization carbon fixation by sludge composting according to claim 1, characterized in that: The mixture after optimizing the particle size is activated at high temperature to form a preliminary pore structure as follows: The mixture after optimizing the particle size is subjected to a high temperature heat treatment at 500-700° C. to activate the CaO and MgO components therein and form a preliminary pore structure.

4. The method for in-situ capture and mineralization carbon fixation by sludge composting according to claim 1, characterized in that: The mixture with the preliminary pore structure is chemically modified by an acetic acid solution, and then vacuum filtered. During the filtration process, the mixture is repeatedly washed with deionized water until the filtrate is neutral, and then dried to obtain a modified porous adsorption material, including: Add 0.2-0.5 mol·L -1 acetic acid solution, mixed at a solid-liquid ratio of 1:5, and stirred at 50°C for 3h to obtain a modified material; The modified material was filtered through a vacuum filtration device, and during the filtration process, it was repeatedly washed with deionized water until the filtrate was neutral. The material was then dried at 105° C. to a constant weight to obtain a modified porous adsorption material.

5. The method for in-situ capture and mineralization carbon fixation by sludge composting according to claim 1, characterized in that: The method adopts carbonate-depositing bacteria as the target bacteria, performs propagation treatment on the target bacteria, and forms a high-density bacterial solution by centrifugation and concentration after propagation, including: The target strain was propagated by liquid fermentation in LB medium at 30-35°C and 120 r / min. -1 Shake culture for 48 hours, expand to a bacterial concentration of 10 9 CFU·mL -1 ; The culture solution after propagation was concentrated by centrifugation to obtain a culture solution concentration of 10 11 CFU·mL -1 High-density bacterial liquid.

6. The method for in-situ capture and mineralization carbon fixation by sludge composting according to claim 1, characterized in that: The modified porous adsorption material is immersed in the high-density bacterial solution, and then the microorganisms in the high-density bacterial solution are driven to penetrate and be loaded inside the modified porous adsorption material by a vacuum filtration method, comprising: The high-density bacterial solution was mixed with the modified porous adsorption material at a liquid-to-solid ratio of 10:1; Vacuum filtration technology was used to drive the microorganisms in the high-density bacterial solution to penetrate and load into the modified porous adsorption material through a vacuum degree of 0.1 MPa. The filtration loading time was 10 minutes.

7. The method for in-situ capture and mineralization carbon fixation by sludge composting according to claim 1, characterized in that: The modified porous adsorption material loaded with microorganisms forms a negative carbon capture material with a microorganism attachment layer after static cultivation: The modified porous adsorption material loaded with microorganisms is statically cultured at 30 to 35° C. for 12 to 24 hours to form a negative carbon capture material with a stable microorganism attachment layer.

8. The method for in-situ capture and mineralization carbon fixation by sludge composting according to any one of claims 1 to 7, characterized in that: The sludge and auxiliary materials are mixed in proportion to form sludge compost, the negative carbon capture material and the sludge compost are mixed in proportion and then piled into a pile, CO2 in the sludge compost is captured and fixed by the negative carbon capture material, and the sludge compost is catalyzed to generate carbonate, including: The sludge and auxiliary materials are mixed in a mass ratio of 3:1, the carbon-nitrogen ratio is adjusted to 30:1, and the initial moisture content is controlled at 60% to 65% to form sludge compost; The negative carbon capture material is uniformly mixed into the sludge compost at a rate of 2% to 5% of the dry weight of the sludge compost and then piled into a pile; The temperature of the pile is maintained at 55-65°C and the humidity is maintained at 40%-50%. The CO2 in the sludge compost is captured and fixed by negative carbon capture materials, while the sludge compost is catalyzed to generate carbonates.

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