Soil carbon immobilization improver based on agricultural waste compost humification as well as preparation method and application of soil carbon immobilization improver

Abstract

The invention belongs to the technical field of soil amendments, and particularly relates to a soil carbon immobilization amendment based on agricultural waste compost humification and a preparation method and application of the soil carbon immobilization amendment. The preparation method comprises the following steps: mixing the rotten vegetable leaves with straw powder for aerobic composting, and mixing the obtained fermentation product with glutamine for humification to obtain a decomposed material; mixing the decomposed material, modified charcoal and polyglutamic acid to obtain a mixed base material; the modified biochar is obtained by pyrolyzing rotten vegetable leaves in an inert atmosphere, activating with phosphoric acid and then performing secondary pyrolysis; and mixing the mixed base material and the compound functional bacterial liquid, and carrying out micro-aerobic directional after-ripening to obtain the soil carbon immobilization improver. According to the invention, glutamine is added to enhance the synthesis of humic acid, the modified charcoal has a mesoporous structure and can physically isolate microbial extracellular enzyme, so that the biodegradation half-life period of the loaded humic acid is prolonged, carboxyl of polyglutamic acid and phenolic hydroxyl of humic acid form a hydrogen bond network, the stability of an aggregate can be enhanced, and efficient and lasting carbon sequestration is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soil improver, and particularly relates to a soil carbon fixation improver based on agricultural waste compost humification, and a preparation method and application thereof. BACKGROUND

[0002] Vegetable tailings, straw and other agricultural wastes, as by-products of agricultural production, are rich in easily degradable organic matter (organic matter > 60%), but in the traditional composting process, most of the organic carbon will be consumed by microorganisms as "energy" instead of being converted into stable "materials" (such as humus) for storage, resulting in high carbon loss rate (40-50%) and low humification efficiency. On the other hand, the global cultivated soil organic carbon pool is continuously declining (annual loss rate of about 0.5-1.0%), and it is urgent to develop efficient carbon fixation technology.

[0003] Existing biochar carbon fixation costs are high, and ordinary compost improvers have poor carbon stability, making it difficult to achieve long-term carbon fixation. Therefore, it is of great environmental and economic value to develop an efficient carbon fixation improver based on agricultural waste, which has the functions of waste resourceization and soil carbon fixation and sequestration. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a soil carbon fixation improver based on agricultural waste compost humification, and a preparation method and application thereof. The carbon fixation improver prepared by the present application has good stability, can efficiently and durably fix carbon, and realizes the effective utilization of vegetable tailings and straw, with low cost.

[0005] The present application provides a preparation method of a soil carbon fixation improver based on agricultural waste compost humification, comprising the following steps: Mix vegetable tailings and straw powder for aerobic composting, mix the obtained fermentation product and glutamine for humification, and obtain composted material; Mix the composted material, modified biochar and polyglutamic acid to obtain a mixed base; the preparation method of the modified biochar comprises: pyrolyzing vegetable tailings under an inert atmosphere, mixing the obtained biochar and phosphoric acid solution for activation, and then performing secondary pyrolysis to obtain modified biochar; Mix the mixed base and composite functional bacteria liquid for micro-aerobic directional after-ripening to obtain a soil carbon fixation improver; the composite functional bacteria liquid comprises oligotrophic Acinetobacter and slow-growing Rhizobium japonicum.

[0006] Preferably, the glutamine is 1.0-2.0% of the mass of the vegetable tailings, based on dry matter.

[0007] Preferably, the temperature of the fermentation product is 50±2℃ when the fermentation product and glutamine are mixed.

[0008] Preferably, the temperature of the humification is 45±3℃; the humification process is accompanied by pulse oxygen supply, the pulse oxygen supply is: using 24h cycle pulse aeration, the aeration amount is 0.6±0.1m 3 / min·t, every 15min interval 1h.

[0009] Preferably, the mass ratio of the humus material, modified biochar and polyglutamic acid is 8:1.2~1.8:0.3~0.7.

[0010] Preferably, the humus material, modified biochar and polyglutamic acid are mixed by using ultrasonic-vacuum impregnation method, the ultrasonic power of the ultrasonic-vacuum impregnation method is 30~50kHz, and the vacuum gauge pressure is-0.15~-0.05MPa.

[0011] Preferably, the temperature of the pyrolysis and secondary pyrolysis is independently 400~600℃, and the holding time is independently 1~2h.

[0012] Preferably, the mass concentration of the phosphoric acid solution is 5±0.5%.

[0013] The application also provides a soil carbon sequestration modifier based on agricultural waste compost humification prepared by the preparation method.

[0014] The application also provides application of the soil carbon sequestration modifier based on agricultural waste compost humification in improving soil.

[0015] Compared with the prior art, the application has the following beneficial effects: The application provides a preparation method of a soil carbon sequestration modifier based on agricultural waste compost humification, including the following steps: mixing vegetable tail vegetables and straw powder to carry out aerobic composting, mixing the obtained fermentation product and glutamine to carry out humification, and obtaining humus material; mixing the humus material, modified biochar and polyglutamic acid to obtain a mixed base; the preparation method of the modified biochar includes: pyrolyzing vegetable tail vegetables in an inert atmosphere, mixing the obtained biochar and phosphoric acid solution to activate, and then carrying out secondary pyrolysis to obtain modified biochar; mixing the mixed base and a composite functional bacteria liquid to carry out micro-aerobic directional after-ripening to obtain a soil carbon sequestration modifier; the composite functional bacteria liquid includes oligotrophic Acinetobacter and slow-growing Rhizobium japonicum.

[0016] This invention incorporates glutamine into fermentation products to enhance humic acid synthesis. Glutamine (Gln) provides a precursor to α-ketoglutarate, activates the microbial tricarboxylic acid cycle (increasing succinate dehydrogenase activity by 2.3 times), promotes aromatic amino acid synthesis, and results in an accumulation of phenolic substances reaching 7.8 mg / g (a 212% increase compared to the control), providing a core framework for humification. The modified biochar, with its mesoporous structure (2-50 nm), physically isolates extracellular enzymes from microorganisms, extending the biodegradation half-life of humic acid-loaded biodegradation to 3.8 times that of the control group. The carboxyl groups of polyglutamic acid form polyelectrolyte complexes with the phenolic hydroxyl groups of humic acid, creating a hydrogen bond network (the endothermic peak shifts to 217℃ in DSC detection), which enhances aggregate stability. The soil carbon sequestration amendment prepared by this invention exhibits good stability, efficient and long-lasting carbon sequestration, and achieves effective utilization of vegetable waste and straw at a low cost.

[0017] Furthermore, the present invention also has at least the following beneficial effects: (1) Pioneering vegetable waste-oriented carbon sequestration technology: Using vegetable waste as the core raw material, glutamine is added by triggering temperature (50±2℃ critical point) to convert it into a soil carbon sequestration improver with high humic acid content. Traditional vegetable waste composting has the problems of high carbon loss rate (>40%) and low humification efficiency. However, this invention reduces the carbon loss rate by 57% through glutamine metabolism regulation and increases the peak intensity of humic acid by 88% as detected by HPLC, realizing the synergistic effect of high-value resource utilization and carbon sequestration of organic waste.

[0018] (2) Development of a pulsed oxygen supply-glutamine synergistic humification process: Temperature-sensitive glutamine (1.0~2.0% of dry matter) is added in combination with pulsed aeration humification (constant temperature of 45±3℃, pulsed oxygen supply) to activate the microbial tricarboxylic acid cycle (succinate dehydrogenase activity increased by 2.3 times), and to directionally synthesize humic acid precursors (phenolic accumulation of 7.8 mg / g). Compared with conventional composting, this invention increases the peak value of humic acid molecules by 88% (HPLC characteristic peak intensity ratio) and effectively blocks the carbon mineralization pathway, solving the technical bottleneck of low conversion efficiency of easily degradable organic matter into a stable carbon pool.

[0019] (3) Constructing a “three-in-one” carbon-stabilized composite structure: Innovatively combining composting products, homologous modified biochar (activated by phosphoric acid, with a specific surface area ≥380m²) 2 The mixture of humic acid and polyglutamic acid in a ratio of 8:1.2~1.8:0.3~0.7 was subjected to ultrasonic-vacuum impregnation loading (loading rate 91%±3%) and polyelectrolyte crosslinking (glass transition temperature 217℃ as determined by DSC) to form a three-dimensional protective system of "humic acid-modified biochar mesoporous confinement-polyglutamic acid network". This structure extended the biodegradation half-life of humic acid to 3.8 times that of the control group, overcoming the technical barrier of poor carbon stability of traditional modifiers.

[0020] (4) Establish a closed-loop technology system of "waste-carbon sequestration-soil remediation" to integrate the functions of vegetable waste resource utilization, soil carbon pool expansion and heavy metal passivation: homologous biochar realizes the full utilization of vegetable waste components; mineral-bound carbon (MOC) improves carbon sequestration efficiency by 155%; biochar-polyglutamic acid complex simultaneously passivates heavy metals (Cd). 2+ (Adsorption capacity 98 mg / g). Compared with commercial biochar carbon fixation agents, its carbon footprint over the entire life cycle is reduced to -1.2 kg CO2-eq / kg, forming a solution with both economic and environmental benefits. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart illustrating the preparation process of the soil carbon sequestration amendment in this invention. Detailed Implementation

[0023] This invention provides a soil carbon sequestration amendment based on agricultural waste composting and humification, comprising the following steps: Vegetable waste is mixed with straw powder for aerobic composting, and the resulting fermented product is mixed with glutamine for humification to obtain mature material. The composted material, modified biochar, and polyglutamic acid are mixed to obtain a mixed base material; the preparation method of the modified biochar includes: pyrolyzing vegetable waste under an inert atmosphere, activating the obtained biochar by mixing it with a phosphoric acid solution, and then performing a second pyrolysis to obtain the modified biochar; The mixed substrate and the compound functional bacterial solution are mixed and subjected to microaerobic directional ripening to obtain a soil carbon sequestration improver; the compound functional bacterial solution includes oligotrophic oligomonas and slow-growing soybean rhizobia.

[0024] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.

[0025] This invention involves mixing vegetable waste with straw powder for aerobic composting, and then mixing the resulting fermented product with glutamine for humification to obtain matured material.

[0026] In this invention, the vegetable waste preferably includes one or more of the following: onion peels, celery leaves, coriander roots, chili seeds, strawberry vines, and tomato vines. The vegetable waste is preferably sorted and crushed, and the particle size of the vegetable waste is preferably ≤2cm.

[0027] In this invention, the straw powder is preferably corn straw powder or wheat straw powder, and the particle size of the straw powder is preferably 1~5cm.

[0028] In this invention, the preferred mass ratio of vegetable waste to straw powder is 3:1, based on dry weight. The preferred C / N mass ratio of the mixture obtained by mixing the vegetable waste and straw powder is 25-30, specifically 28±1, and the preferred moisture content is 60-70%, specifically 60±3%.

[0029] In this invention, the preferred temperature for aerobic fermentation is 55-60°C, and the preferred time is 7-8 weeks. At the end of aerobic fermentation (i.e., when the fermented material and glutamine are mixed), the preferred temperature of the compost pile (fermented material) is 50±2°C. The addition of glutamine in this invention provides support for mesophilic bacteria, the main force in humic substance synthesis, serving as both a "nutrient source" and a "precursor," directly guiding carbon flow towards humic substance synthesis. The addition of glutamine at the end of fermentation avoids its ineffective consumption during the peak decomposition period, maximizing resource utilization efficiency.

[0030] In this invention, the glutamine is preferably used in the form of a glutamine solution, and the mass concentration of the glutamine solution is preferably 8-12% (w / v), specifically 10%. On a dry weight basis, the glutamine is preferably 1.0-2.0% of the weight of the vegetable waste, specifically 1.5%. The mixing of the fermented product and glutamine is preferably achieved by spraying the glutamine solution onto the fermented product. Glutamine (Gln), as a precursor to α-ketoglutarate, can activate the microbial tricarboxylic acid cycle (increasing succinate dehydrogenase activity by 2.3 times) and promote the humification pathway, where phenolic substances accumulate to 7.5-8.0 mg / g.

[0031] In this invention, the preferred temperature for humification is 45±3℃, and the preferred time is 18~22 days, specifically 20 days; the humification is preferably carried out under constant temperature conditions. The humification process is preferably accompanied by pulsed oxygen supply, which is preferably: 24-hour cycle pulse aeration (air) with an aeration rate of 0.6±0.1 m³ / h. 3 / min·t (t represents tons, based on fermentation product), with a 1h interval for every 15 minutes. Compared to traditional composting, this invention uses pulsed oxygen supply to enhance humic acid synthesis, with HPLC detection showing an 88% increase in humic acid peak intensity and a 57% reduction in carbon loss rate.

[0032] After obtaining the decomposed material, the present invention mixes the decomposed material, modified biochar and polyglutamic acid to obtain a mixed base material; the preparation method of the modified biochar includes: pyrolyzing vegetable waste under an inert atmosphere, activating the obtained biochar by mixing it with a phosphoric acid solution, and then performing a second pyrolysis to obtain the modified biochar.

[0033] In this invention, the process of drying vegetable tails before pyrolysis is preferably further comprising: drying the vegetable tails; the drying temperature is preferably 105°C, and the drying time is preferably until a constant weight is reached.

[0034] In this invention, the pyrolysis temperature is preferably 400~600℃, specifically 500±10℃, and the holding time is preferably 1~2h. The pyrolysis under an inert atmosphere in this invention prevents the biomass from burning (i.e., undergoing an aerobic reaction).

[0035] In this invention, the preferred mass concentration of the phosphoric acid solution is 5 ± 0.5%; the modified biochar activated by the phosphoric acid solution forms a microporous composite structure with a specific surface area ≥ 380 m². 2 / g, with a mesoporous content >60%. The 2-50nm mesopores formed by the modified biochar can physically isolate extracellular enzymes of microorganisms, extending the biodegradation half-life of humic acid-loaded biochar to 3.5-4.0 times that of the control group.

[0036] In this invention, the preferred ratio of biochar to phosphoric acid solution is 1g:5~10mL; the mixing of biochar and phosphoric acid solution is preferably carried out under stirring, with the stirring temperature preferably being 60~80℃ and the stirring time preferably being 2~6h. The stirring temperature and time described in this invention ensure that the phosphoric acid solution fully impregnates the pores of the biochar.

[0037] In this invention, the temperature of the secondary pyrolysis is preferably 400~600℃, specifically 400℃, and the holding time is preferably 1~2 hours. During the secondary pyrolysis, phosphoric acid corrodes the carbon skeleton during heating, creating pores and expanding the original porosity.

[0038] In this invention, the secondary pyrolysis preferably includes washing and drying; the washing process has no special requirements and continues until the washing solution is neutral; the purpose of washing is to remove residual phosphoric acid and other impurities; the drying temperature is preferably 105~110℃.

[0039] In this invention, the preferred mass ratio of the composted material, modified biochar and polyglutamic acid is 8:1.2~1.8:0.3~0.7, and more specifically, it can be 8:1.5:0.5.

[0040] In this invention, the mixture of the composted material, modified biochar, and polyglutamic acid is preferably prepared by ultrasonic-vacuum impregnation. The ultrasonic power of the ultrasonic-vacuum impregnation method is 30~50kHz, specifically 40kHz. The gauge pressure of the vacuum is preferably -0.15~-0.05MPa, specifically -0.08MPa. The processing time is preferably 30min. In this embodiment of the invention, the specific steps are as follows: (1) the composted product, modified biochar, and polyglutamic acid are initially mixed in a container in proportion; (2) the resulting mixture is placed in a sealable ultrasonic-vacuum impregnation tank, the vacuum pump is started, the system pressure is reduced to -0.08 MPa, and maintained for 5~10min; (3) under the condition of maintaining vacuum, the ultrasonic generator is turned on and the mixture is processed at a frequency of 40 kHz for 30min; (4) air is introduced into the impregnation tank to restore normal pressure. Step (2) can extract the air inside the pores of the biochar and the gaps between the mixture. Step (3) Ultrasonic treatment: Ultrasonic waves generate a "cavitation effect" in the liquid, forming a powerful microjet and shock wave, which can violently agitate the mixture. On the one hand, this allows molecules such as humic acid to fully contact the surface of the modified biochar, and on the other hand, it helps drive molecules into the micropores and mesopores of the modified biochar. Step (4) Restoring atmospheric pressure: Under atmospheric pressure, the liquid will be further forced into the depths of the biochar pores.

[0041] This invention utilizes an ultrasonic-assisted negative pressure environment to load humic acid into the pores of modified biochar, achieving a loading rate of 90±3%. Polyglutamic acid acts as a molecular binder, cross-linking through amide bonds to form a three-dimensional network structure of humic substance-modified biochar-polyglutamic acid (FTIR detection at 1650 cm⁻¹). -1 It exhibits new characteristic peaks, with the glass transition temperature increased to 217℃ by DSC detection and thermal decomposition delayed by 40℃ by TGA analysis, resulting in enhanced stability.

[0042] In this invention, the mixture of the composted material, modified biochar, and polyglutamic acid preferably further includes drying, and the drying is preferably freeze-drying. The freeze-drying preferably includes pre-freezing, primary drying, and secondary drying. The pre-freezing specifically involves: rapidly placing the wet material treated by ultrasonic-vacuum impregnation into an ultra-low temperature freezer at -40°C to -80°C to completely freeze it into a solid. The rapid freezing of this invention helps to form small ice crystals and reduces damage to the material structure. The primary drying specifically involves: rapidly transferring the frozen material into a freeze dryer; turning on the vacuum pump to evacuate the vacuum in the drying chamber to a high vacuum state of 10~50 Pa; raising the temperature to -20°C to -10°C, where the ice will directly sublimate; the primary drying time accounts for approximately 80~90% of the total drying time. The secondary drying specifically involves: after all the ice has sublimated, raising the temperature of the partition to 25~30°C and maintaining it under high vacuum for several hours to remove residual moisture bound by physical adsorption in the material.

[0043] After obtaining the mixed substrate, the present invention mixes the mixed substrate and the compound functional bacterial solution for microaerobic directional post-maturation to obtain a soil carbon sequestration improver; the compound functional bacterial solution includes oligotrophic oligomonas and slow-growing soybean rhizobia.

[0044] In this invention, the microaerobic directional ripening is preferably carried out at 15-20℃ and 45-55% RH, and the microaerobic directional ripening time is preferably 48-72 hours, specifically 50 hours; the compound functional bacterial solution is preferably composed of oligotrophic domesticated Stenotrophomonas nitritireducens and slow-growing soybean rhizobium (Bradyrhizobium japonicum) at a ratio of 1×10 8 CFU / mL: 5×10 7 The compound is prepared by mixing CFU / mL; the inoculation amount of the compound functional bacterial solution is preferably 3-5% of the mass of the mixed substrate, specifically 4%.

[0045] In this invention, the process after micro-oxygen directional ripening preferably includes freeze drying, which is preferably vacuum freeze drying at -30°C. The moisture content of the soil carbon fixation amendment obtained after freeze drying is preferably below 8%.

[0046] The present invention also provides a soil carbon sequestration improver based on agricultural waste composting and humification, prepared by the method described in the above technical solution.

[0047] In this invention, the soil carbon retention amendment preferably has a moisture content of <5% and a particle size of 1~5mm; the humic acid loading rate in the modified biochar pores of the soil carbon retention amendment is preferably 91.2±2.8%, the residual carbon rate at 600℃ is preferably 64.3%, and the glass transition temperature is preferably 217℃.

[0048] The present invention also provides the application of the soil carbon sequestration amendment based on agricultural waste composting and humification described in the above technical solution in soil improvement.

[0049] The soil carbon sequestration improver based on agricultural waste composting and humification provided by this invention can be applied to fields such as improving arable land quality and carbon sequestration, and remediation of degraded soil, specifically such as carbon sequestration of degraded arable land, structural restoration of desertified soil, and treatment of farmland contaminated by heavy metals.

[0050] Test data show that after applying the soil carbon sequestration amendment, the carbon components in the soil undergo directional transformation. When the application rate is 3 t / ha, the carbon sequestration efficiency of sandy soil reaches 68% (compared to ≤32% in the control group). Among these improvements, the proportion of active carbon (LOC) decreases to 19%; mineral bound carbon (MOC) increases to 2.8 g / kg (+155%); particulate organic carbon (POC) increases to 1.5 g / kg (+230%); and the annual soil organic matter sequestration rate increases to 4.2‰ (IPCC default value 1‰). The carbon footprint of the amendment throughout its entire life cycle is -1.2 kg CO2-eq / kg (net carbon sink), which reduces carbon emissions by 70-80% compared to commercial biochar carbon sequestration agents.

[0051] To further illustrate the present invention, the soil carbon sequestration amendment based on agricultural waste composting and humification, its preparation method, and its application are described in detail below with reference to the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0052] Figure 1 This is a flowchart of the preparation process of the soil carbon sequestration amendment in this invention. The entire process can be divided into four major stages, achieving a deep integration of waste resource utilization and soil carbon sequestration.

[0053] Phase 1: Raw Material Pretreatment Vegetable waste first enters the pre-processing system for sorting, crushing, and other operations, laying the foundation for subsequent targeted conversion.

[0054] The second stage involves targeted carbon fixation and conversion, with the output being a matured product high in humic acid. Carbon loss is significantly reduced, and humic acid synthesis efficiency is greatly improved. The pretreated material enters the aerobic fermentation chamber; Temperature-triggered precise control: Through real-time temperature monitoring, the system automatically triggers and adds 1.5% glutamine solution when the reactor temperature reaches the critical point of 50±2℃, which marks the end of the high-temperature period. This precisely controls the microbial metabolic pathway, shifting the carbon flow from decomposition to synthesis.

[0055] Pulsed oxygen supply synergistic humification: In conjunction with the addition action, the system initiates a pulse aeration humification process, performing intermittent high-intensity aeration at a constant temperature of 45℃. This not only saves energy but also creates a microbial environment conducive to humic acid synthesis.

[0056] Phase 3: Construction of Carbon-Stabilized Complexes Preparation of homologous materials: Some vegetable waste was pyrolyzed to prepare biochar, which was then activated and modified with phosphoric acid to obtain an adsorption matrix with a large specific surface area.

[0057] Mesoporous confinement and network stabilization: The second-stage composting products, modified biochar, and polyglutamic acid were mixed in precise proportions and loaded and composited using ultrasonic-vacuum impregnation technology. This process formed a three-dimensional stable structure of "humic acid-biochar mesoporous confinement-polyglutamic acid network", achieving a high loading rate of 91% and a high glass transition temperature of 217℃, which greatly extended the stability of carbon.

[0058] Phase 4: Soil Application and System Optimization The prepared carbon-stabilized complex is applied to soil. By monitoring its carbon sequestration effect (such as carbon pool diffusion data), the final effect of the technology system is evaluated, and the data is fed back to the system initiation for closed-loop optimization, continuously improving the efficiency and environmental and economic benefits of the entire process.

[0059] In this embodiment of the invention, the vegetable scraps used mainly include onion peels, celery leaves, coriander roots, chili seeds, strawberry vines, and tomato vines.

[0060] Example 1: Targeted Humicification Regulation of Vegetable Waste Take 200 kg of vegetable waste, sort it to remove impurities (plastic ropes, stones, etc.), and then crush it to a particle size of ≤2 cm. Mix it with corn stalk powder at a dry weight ratio of 3:1, adjust the C / N ratio to 28±1, and the moisture content to 60±3% to obtain the mixture.

[0061] Place the mixture in an aerobic fermentation reactor. After the high-temperature period ends (the temperature sensor monitors it to be 50±0.5℃ in real time), spray atomized glutamine solution (10% w / v) at a glutamine content of 1.5% of the dry matter of the vegetable waste. Start the pulse aeration program: 24-hour circulating aeration (0.6 m³). 3 Fermentation was carried out at a constant temperature of 45±0.3℃ for 20 days (15 min / time, 1 hour interval) to obtain the mature product.

[0062] Compare with Example 1 The only difference from Example 1 is that: no atomized glutamine solution is sprayed, and a conventional continuous aeration mode (aeration rate of 0.1 m³) is used. 3 The mixture is naturally fermented at a rate of 1 / min·t, with a fermentation cycle of 20 days.

[0063] In conventional continuous low-intensity aeration (0.1 m) 3 In the / min·t) mode, the fermentation temperature follows the natural law, going through the stages of heating, high temperature (temperature rises to 60~70℃), cooling and maturation, rather than the constant temperature control in Example 1, until the fermentation ends after 20 days.

[0064] The test results of the fermentation products obtained in Example 1 and Control Example 1 are as follows: (1) Humic acid content: The peak intensity of humic acid detected by HPLC reached 15800 AU, which was 88% higher than that of control example 1 (8400 AU); (2) Carbon loss rate: The cumulative CO2 emissions during the entire fermentation process, as determined by gas chromatography, were 18.3 kg, a 57% reduction compared to Control Example 1 (42.7 kg); (3) Precursor substances (core aromatic precursor substances that can be used to synthesize humic substances, mainly polyphenols): The cumulative amount in the fermentation products detected by the Folin-Ciocalteu method was 7.8 mg / g, which was 212% higher than that of Control Example 1 (2.5 mg / g).

[0065] Example 2: Preparation of carbon-stabilized complex 1. 100 kg of vegetable waste from the same source was pyrolyzed at 500℃ under limited oxygen conditions for 2 hours to obtain biochar. After activation with 5 wt% phosphoric acid solution, the resulting modified biochar had a specific surface area of ​​392 m². 2 / g (determined by BET method). Specific procedures are as follows: Pyrolysis: Vegetable waste is dried to constant weight in an oven at 105℃ and then placed in a sealed pyrolysis furnace (tube furnace). Before heating, during heating, and during cooling, an inert gas (high-purity nitrogen) is continuously introduced into the furnace. The gas flow rate is controlled to ensure that the atmosphere inside the furnace is oxygen-free or slightly oxygen-free, thereby preventing the biomass from burning (aerobic reaction) and instead allowing it to undergo pyrolysis (anaerobic or hypoxic reaction) to obtain biochar.

[0066] Activation: The prepared crude biochar is mixed with 5 wt% phosphoric acid aqueous solution at a solid-liquid ratio (mass ratio 1:5, i.e., 1 g of biochar is added to 5 mL of phosphoric acid solution).

[0067] Stirring: Stir and impregnate at 60℃ for 2 hours to ensure that the phosphoric acid solution fully impregnates the pores of the biochar.

[0068] Secondary pyrolysis: The impregnated mixture is filtered and separated, and then placed back into the pyrolysis furnace for activation pyrolysis at 400℃ for 1 hour under inert gas protection.

[0069] Washing and drying: After pyrolysis, the activated biochar was cooled to room temperature and repeatedly washed with a large amount of deionized water until the pH of the washing solution was close to neutral. Finally, the washed biochar was dried at 105°C to obtain modified biochar.

[0070] 2. Take 80 kg of the composted product from Example 1, 15 kg of modified biochar, and 5 kg of polyglutamic acid (i.e., a mass ratio of 8:1.5:0.5) and mix them. Treat the mixture with an ultrasonic-vacuum impregnation system (40 kHz, 0.08 MPa) for 30 min to obtain the mixed base material. The specific operation is as follows: Mixing: First, the composted product (rich in humic acid), modified biochar and polyglutamic acid from Example 1 are initially mixed in a container in proportion.

[0071] Vacuuming: Place the resulting mixture in a sealable ultrasonic-vacuum impregnation tank. Start the vacuum pump and reduce the system pressure to -0.08 MPa (gauge pressure, equivalent to 0.02 MPa absolute pressure), and maintain this pressure for 5-10 minutes.

[0072] Ultrasonic treatment: While maintaining a vacuum, turn on the ultrasonic generator and treat at a frequency of 40 kHz for 30 minutes.

[0073] Restoring atmospheric pressure: After the treatment is completed, slowly introduce air into the impregnation tank to restore atmospheric pressure.

[0074] Freeze-drying includes pre-freezing, primary drying, and secondary drying. Pre-freezing: The wet material, after ultrasonic-vacuum impregnation, is rapidly placed in an ultra-low temperature freezer at -40℃ to -80℃ to completely freeze it into a solid. Primary drying (sublimation drying): The frozen material is quickly transferred to a freeze dryer; the vacuum pump is turned on, and the vacuum level in the drying chamber is evacuated to a high vacuum of 10~50 Pa. The temperature is appropriately increased (maintaining the material temperature at -20℃ to -10℃), and the ice will sublimate directly. Secondary drying (desorption drying): After all the ice has sublimated, the temperature of the partition is further increased (to 25~30℃) and maintained under high vacuum for 5~10 hours to remove residual moisture bound by physical adsorption. The final product is a loose, porous solid composite with extremely low moisture content (<5%).

[0075] 3. The mixed substrate obtained in step 2 and the compound functional bacterial solution are subjected to microaerobic directional ripening at 15-20℃ and 45-55% RH for 50 hours. The compound functional bacterial solution is composed of oligotrophic domesticated Stenotrophomonas nitritireducens and slow-growing soybean rhizobium (Bradyrhizobium japonicum) at a ratio of 1×10⁻⁶. 8 CFU / mL: 5×10 7 The mixture is formulated with CFU / mL and the inoculation amount is 4% of the mass of the mixed substrate. After micro-aerobic directional ripening, it is then vacuum freeze-dried at -30℃ until the moisture content is <8%.

[0076] Compare with Example 2 The only difference from Example 2 is that it is not combined with modified biochar and polyglutamic acid (no ultrasonic-vacuum impregnation treatment is performed), and the fermented product is directly detected. The specific operation is as follows: Take 80 kg of the composted product prepared in Example 1 and dry it with conventional hot air at 40±2℃ until the moisture content is <10%. Then, perform differential scanning calorimetry (DSC) to determine its glass transition temperature.

[0077] The test results for Example 2 and Control Example 2 (untreated group) are as follows: (1) Loading efficiency test was conducted according to ISO 10694:1995 - Soil quality - dry combustion method (elemental analyzer) for determination of total organic carbon and total carbon content: TOC analysis showed that the humic acid loading rate in biochar pores in Example 2 reached 91.2±2.8%; (2) Structural stability - Glass transition temperature. According to ISO 11357-2:2020 "Differential scanning calorimetry (DSC) for plastics - Part 2: Determination of glass transition temperature": The glass transition temperature of Example 2 was 217℃ by DSC, and 180℃ for the untreated group. This indicates that the skeletal support of biochar and the adhesive and cross-linking effects of polyglutamic acid jointly enhance the three-dimensional network structure of humic molecules, so that chain segment movement (i.e., glass transition) occurs at a higher temperature, thus giving the product higher structural stability. This stability is crucial for its slow-release performance and persistence in soil. (3) TGA analysis - char rate refers to ISO 11358-1:2022 "Thermogravimetric analysis (TGA) of plastic polymers - Part 1: General principles": The char rate of the material in Example 2 at 600°C increased to 64.3% (compared to 41.5% in Control Example 2); (4) Particle characteristics - Particle size distribution refers to ISO 13320:2020 - "Particle size analysis by laser diffraction": laser particle size analyzer was used to determine the particle size distribution of Example 2, 1~5 mm (D 50 =2.8 mm).

[0078] Application Example 1: Verification of Synergistic Carbon Fixation and Heavy Metal Passivation 1. Experimental group: The amendment prepared in Example 2 was applied to sandy degraded soil at a rate of 3 t / ha (initial organic carbon 0.8%). Control group: On the same piece of sandy degraded soil, the amendment prepared in Example 2 was not applied, but only an equal amount of conventional organic fertilizer was applied; Under identical field management practices (tillage twice at a depth of 20cm using the same model rotary tiller to evenly mix straw into the topsoil, and drip irrigation of 20 cubic meters per acre for all experimental plots within two days after straw return to the field), soil carbon composition data were measured after 180 days. 1. Carbon composition transformation (after 180 days) Table 1. Soil carbon composition data 180 days after application of soil amendment

[0079] It can be seen that the soil amendment prepared in Example 2 has excellent soil carbon sequestration capacity and can significantly improve the stability of the soil carbon pool. Specifically, this is reflected in: Mineral-bound carbon (MOC) increased significantly (by 155%): MOC refers to organic carbon tightly bound to minerals such as silt and clay in the soil, and is the most stable carbon pool with the longest turnover period (hundreds to thousands of years). The amendment of this invention greatly promotes the transformation of unstable organic carbon into a long-term stable carbon pool, which is a key indicator of achieving permanent carbon sequestration; Particulate organic carbon (POC) increased significantly (by 230%): POC mainly consists of partially decomposed plant residues and microbial cells, belonging to a moderately stable carbon pool and a core indicator of soil fertility. The soil conditioner of this invention significantly enhances basic soil fertility, providing continuous nutrients and energy for microorganisms; The proportion of activated carbon (LOC) decreased significantly (from 63% to 19%): LOC is a carbon component that is easily decomposed by microorganisms. Its high content means that the carbon pool is unstable and easily lost in the form of CO2.

[0080] After applying the soil amendment of this invention, the quality of the soil carbon pool has been fundamentally improved: it has shifted from being dominated by "easily decomposed and easily lost" active carbon to being dominated by "stable and persistent" MOC and POC. The stability of carbon has been significantly enhanced. The soil amendment of this invention not only increases the amount of total organic carbon in the soil ("enhancing the sink"), but more importantly, it optimizes the structure and quality of the carbon pool, fixing more carbon in a stable form, thus achieving truly efficient and persistent carbon sequestration.

[0081] 2. Heavy metal passivation efficiency (1) Adsorption capacity: Cd was measured in batch experiments 2+ The saturated adsorption capacity was 98.7 mg / g (Langmuir model). The specific steps were as follows: Preparation of solutions: Prepare a series of cadmium nitrate (Cd(NO3)2) solutions with different initial concentrations (0, 10, 20, 50, 100 mg / L).

[0082] Weigh the samples: Accurately weigh several equal amounts of the improver sample (0.1g) and place them in a series of conical flasks.

[0083] Isothermal oscillation adsorption: A certain volume (50 mL) of Cd at different concentrations was added to each container. 2+ Solution. After sealing the container, place it in a constant temperature shaker and shake it at a fixed temperature (25℃) and speed for a period of time (24h) to ensure that the adsorption reaches equilibrium.

[0084] Separation and Detection: After shaking, the solid modifier was separated from the liquid using a centrifuge and filter membrane. The remaining Cd in the solution was measured using atomic absorption spectrometry (AAS). 2+ concentration.

[0085] Calculation and Modeling: Based on Cd before and after adsorption 2+ The concentration difference was used to calculate the adsorption capacity per unit mass of modifier. The adsorption capacity data at different initial concentrations were fitted using the Langmuir adsorption isotherm model, yielding a theoretical maximum saturation adsorption capacity of 98.7 mg / g.

[0086] (2) Bonding strength: XPS analysis of Cd 3d 5 / 2 The binding energy shift of 1.3 eV confirms the carboxyl complexation.

[0087] This positive shift indicates a decrease in the electron cloud density around the Cd atom. This is because the oxygen atom on the carboxyl group (-COOH) in the modifier has a lone pair of electrons, which interact with the positively charged Cd atom. 2+ Coordinate bonds (complexation) are formed. During the formation of coordinate bonds, the electron cloud of the oxygen atom partially shifts towards Cd. 2+ This results in a relative decrease in the electron cloud density of Cd atoms, which in turn makes the core electrons more tightly bound to the atomic nucleus. Ionizing them requires higher energy, i.e., the binding energy increases.

[0088] (3) Field effect: DTPA reduced Cd by 89% (initial value 2.8 mg / kg, reduced to 0.31 mg / kg after 180 days of application).

[0089] DTPA-extractable Cd: This refers to cadmium extracted from soil using diethylenetriaminepentaacetic acid (DTPA), a chemical extractant. This method simulates the absorption capacity of plant roots, and the extracted Cd is considered to represent the portion that plants can absorb and utilize, i.e., bioavailable heavy metals.

[0090] The DTPA-extractable Cd content decreased by 89%, indicating that the amendment can reduce ecological risks: the toxic cadmium in the soil that can be absorbed by plants and enter the food chain is greatly reduced, significantly reducing the potential risks of heavy metals to agricultural product safety and human health; it has a passivation effect: from the perspective of actual field effects, it has been confirmed that the amendment can effectively passivate Cd in the soil, transforming it from an active and effective form into an inert and stable form, thereby achieving the purpose of soil remediation.

[0091] 3. Carbon footprint accounting Table 2 Carbon Footprint Calculation Results

[0092] The entire process is divided into three stages: raw material processing, biochar preparation, and soil carbon sequestration. The first two stages generate some carbon emissions (positive values) due to energy consumption (electricity and heat), but these emissions are partially offset by optimization measures such as biogas power generation recovery and waste heat supply. This proves that the system of this invention is not only not a carbon emission source, but also a significant "carbon sink," achieving negative carbon emissions and demonstrating outstanding environmental benefits.

[0093] Application Example 2: Comparison of Comprehensive Improvement Effects The soil conditioner was applied at a rate of 3 t / ha and mixed evenly with the soil. Three groups were set up, and corn was planted in each group. The soil was watered with 50 mL of water once a day at room temperature. The results were tested after 60 days.

[0094] Experimental group: Modifier prepared in Example 2 (3 t / ha); Control group A: Commercial biochar carbon fixation agent (3 t / ha), i.e. high-temperature straw organic carbon, pyrolyzed at 800℃; Control group B: Traditional vegetable waste compost (3 t / ha), prepared according to control example 1, except that no straw powder was added.

[0095] Table 3. Data on the overall improvement effect

[0096] In Table 3, the carbon stability index = (MOC + OOC) / TOC × 100%; TOC - Total Organic Carbon: Measured using a TOC analyzer, it is calculated by converting all organic carbon in the sample into CO2 through chemical oxidation and then detecting the amount of CO2. MOC - Mineral-bound Carbon: Physically grouped based on particle size. Soil samples are first dispersed in water, then centrifuged to separate particles <53μm. The content of organic carbon bound to these particles is then determined as the MOC. OOC - Light Organic Carbon: Utilizing density flotation. Soil samples were placed in a solution with a density of 1.6–2.0 g / cm³. 3 In a sodium iodide solution, after centrifugation, the light components floating on the surface are OOC, while the sediment is recombined organic carbon bound to minerals. Economic cost (yuan / t) = (raw material cost + production cost + other costs) / total output; Product carbon footprint = Total carbon emissions from production process - Carbon sink compensation - Soil carbon sequestration.

[0097] The data above show that: (1) the soil carbon sequestration efficiency of the experimental group was 125% higher than that of commercial biochar, and the LOC ratio was reduced to less than 20%; (2) the carbon footprint of the whole life cycle was negative (-1.2 kg CO2-eq / kg), which verified the characteristics of the "negative carbon improver"; (3) the unit carbon sequestration cost was reduced by 67% compared with commercial products, which is both environmentally and economically feasible.

[0098] This invention provides a complete technical solution from vegetable waste pretreatment to amendment application, covering vegetable waste crushing, temperature-triggered glutamine (Gln) addition, pulsed oxygenation humification, biochar homologous modification, ultrasonic-vacuum loading, polyelectrolyte crosslinking, and soil carbon sequestration.

[0099] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a soil carbon sequestration amendment based on agricultural waste composting and humification, characterized in that, Includes the following steps: Vegetable waste is mixed with straw powder for aerobic composting, and the resulting fermented product is mixed with glutamine for humification to obtain mature material. The decomposed material, modified biochar, and polyglutamic acid are mixed to obtain a mixed base material; The method for preparing the modified biochar includes: pyrolyzing vegetable waste under an inert atmosphere, activating the resulting biochar by mixing it with a phosphoric acid solution, and then performing a second pyrolysis to obtain the modified biochar. The mixed substrate and the compound functional bacterial solution are mixed and subjected to microaerobic directional ripening to obtain a soil carbon sequestration improver; the compound functional bacterial solution includes oligotrophic oligomonas and slow-growing soybean rhizobia.

2. The preparation method according to claim 1, characterized in that, On a dry matter basis, the glutamine is 1.0 to 2.0% of the weight of vegetable waste.

3. The preparation method according to claim 1 or 2, characterized in that, The temperature of the fermentation product was 50±2℃ when the fermentation product and glutamine were mixed.

4. The preparation method according to claim 1, characterized in that, The temperature for humification is 45±3℃; the humification process is accompanied by pulsed oxygen supply, which is achieved by 24-hour cycle pulse aeration with an aeration rate of 0.6±0.1 m³ / h. 3 / min·t, with a 1h interval for every 15min duration.

5. The preparation method according to claim 1 or 4, characterized in that, The mass ratio of the composted material, modified biochar, and polyglutamic acid is 8:1.2~1.8:0.3~0.

7.

6. The preparation method according to claim 1, characterized in that, The composted material, modified biochar, and polyglutamic acid are mixed and impregnated using an ultrasonic-vacuum impregnation method. The ultrasonic power of the ultrasonic-vacuum impregnation method is 30~50kHz, and the gauge pressure of the vacuum is -0.15~-0.05MPa.

7. The preparation method according to claim 1, characterized in that, The pyrolysis and secondary pyrolysis temperatures are independently set at 400~600℃, and the holding times are independently set at 1~2h.

8. The preparation method according to claim 1 or 7, characterized in that, The mass concentration of the phosphoric acid solution is 5 ± 0.5%.

9. The soil carbon sequestration amendment based on agricultural waste composting and humification obtained by the preparation method according to any one of claims 1 to 8.

10. The application of the soil carbon sequestration amendment based on agricultural waste composting and humification as described in claim 9 in soil improvement.

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