A process for processing of vinasse into fertilizer and a compound microbial fertilizer

Abstract

The application provides a tail-cabbage fertilizer treatment process and a compound microbial fertilizer, and belongs to the technical field of biological fertilizer. The tail-cabbage fertilizer treatment process comprises the following steps: S1, performing solid-liquid separation on tail-cabbage to obtain tail-cabbage residue and tail-cabbage wastewater; S2, performing aerobic composting treatment on the tail-cabbage residue to obtain a mature compost product; S3, performing anaerobic fermentation treatment on the tail-cabbage wastewater under anaerobic conditions to obtain a fermentation liquor; S4, spraying and absorbing ammonia-containing tail gas in the aerobic composting treatment process and then introducing the tail gas into the anaerobic fermentation treatment process; and S5, preparing a granular compound microbial fertilizer and a liquid fertilizer. The application effectively solves the problems of high water content, poor aeration, unbalanced nutrition of tail-cabbage compost, difficult tail-cabbage wastewater treatment, easy odor generation and the like, and the prepared compound microbial fertilizer has the long-acting fertilizer supply characteristics of organic fertilizer and the growth promotion function of microbial inoculum, and has significant economic, environmental and ecological benefits.

Description

Technical Field

[0001] This application relates to the field of bio-fertilizer technology, and in particular to a process for treating vegetable waste into fertilizer and a compound microbial fertilizer. Background Technology

[0002] Vegetable waste refers to agricultural waste such as withered leaves, rotten fruit, dead branches, and vines that have no commercial value generated during the harvesting, processing, transportation, and sale of vegetables. Its total amount can even reach more than 30% of vegetable production. As a special agricultural resource, vegetable waste contains a large amount of cellulose and lignin, as well as a certain amount of crude protein, crude fat, phosphorus, potassium, and many trace elements. Effective utilization can reduce environmental pollution and improve carbon sequestration efficiency. Current methods for treating vegetable waste mainly involve composting or further processing after crushing. Vegetable waste has an extremely high water content, making direct composting ineffective and requiring a large area. Its composting effect is greatly affected by the C / N ratio and moisture content, and improper treatment can easily produce foul odors and pollute the environment. After crushing, the vegetable waste residue is generally dried and used as animal feed. Feed quality is often affected by the freshness of the waste, and its taste and cellulose and protein content are unstable. In particular, the wastewater generated after crushing has an extremely low C / N ratio and high pigment content, resulting in high wastewater treatment costs, which is a major headache for large-scale vegetable waste treatment plants.

[0003] The following technical problems are currently faced in the treatment of vegetable waste composting: (1) unbalanced nutrition, low carbon-nitrogen ratio and lack of key trace elements for microbial growth; (2) high water content, poor aeration, slow heating, affecting composting effect; (3) vegetable waste is soft and easily collapses and clumps, making it difficult to aerobic composting, and it is easy to carbonize after the temperature rises, affecting quality. The technical problems faced in the treatment of vegetable wastewater into liquid fertilizer are: (1) severe nutritional imbalance, low carbon-nitrogen ratio and lack of key trace elements for microbial growth; (2) many miscellaneous bacteria, and vegetable wastewater contains original strains of vegetables, making it difficult for target strains to grow, and it is easy to smell bad if not treated properly; (3) liquid fertilizer is easily affected by the environment, the activity of the strains is unstable, it is easy to lose its activity, the physical stability is poor, and the shelf life is short.

[0004] Patent ZL2025210694220.7 discloses a method for processing vegetable waste into compound microbial fertilizer using a compound culture medium and a fermentation process. This method enhances the nutrient supply capacity of the culture medium by optimizing the ratio of carbon sources, nitrogen sources, inorganic minerals, and bioactivators. Simultaneously, it incorporates a multi-stage fermentation strategy to achieve efficient synergistic proliferation of dominant microbial communities. However, this method requires sterilization and enzymatic hydrolysis, making it complex and relatively costly, and only suitable for processing small batches of vegetable waste or fruit and vegetable scraps.

[0005] Patent ZL202311228843.2 discloses a composting method that synergistically promotes the decomposition of agricultural organic waste and reduces greenhouse gas emissions. This method features improved harmlessness during decomposition, shorter composting cycles, and reduced emissions of harmful gases. However, the fermentation cycle is 25-30 days, which is time-consuming and costly.

[0006] Patent ZL201710872363.8 discloses a method for preparing organic fertilizer from vegetable waste, making full use of vegetable waste and other agricultural waste to produce organic fertilizer, thereby achieving the goal of resource utilization, harmlessness, and recycling of agricultural waste. This patent requires mixing vegetable waste with straw, rice husks, and livestock manure for fermentation to prepare fertilizer, which may pose a risk of heavy metal and antibiotic residues. Summary of the Invention

[0007] This application is made in view of the above-mentioned problems, and its purpose is to provide a process for treating vegetable waste as fertilizer and a compound microbial fertilizer.

[0008] Specifically, the first aspect of this application provides a process for treating vegetable waste as fertilizer, including the following steps: S1: Separate the vegetable waste into solid and liquid components to obtain vegetable residue and vegetable wastewater, respectively. S2: Mix the vegetable waste with composite straw powder and modified fly ash-based carrier, inoculate with high-temperature composting microbial agent, and carry out aerobic composting treatment to obtain mature compost products. S3: Mix the wastewater from the vegetable tail with a carbon source and inorganic salts, inoculate with lactic acid bacteria, and carry out anaerobic fermentation under anaerobic conditions to obtain fermentation liquid; S4: The ammonia-containing tail gas generated during the aerobic composting process described in step S2 is sprayed and absorbed, and then introduced into step S3 as a nitrogen source to supplement and adjust the pH of the fermentation liquid. S5: A portion of the fermentation liquid is returned to the aerobic composting treatment step in step S2 to adjust the moisture content of the compost material and supplement the microbial agent; the remaining fermentation liquid is used to prepare liquid fertilizer, and the mature compost product is granulated and dried to obtain granular compound microbial fertilizer.

[0009] Furthermore, the preparation method of the modified fly ash-based carrier in step S2 includes: Fly ash is mixed with an alkaline solution and activated at 80–100°C for 1–3 hours. After washing and drying, activated fly ash is obtained. The activated fly ash is mixed with fermentation broth at a solid-liquid ratio of 1:5–15 and adsorbed for 10–24 hours. After filtration, it is dried until the moisture content is ≤10%, thus obtaining a modified fly ash-based carrier.

[0010] The fermentation broth is the fermentation broth obtained in the wastewater fermentation treatment step, and its viable lactic acid bacteria count is ≥1×10⁻⁶.9 CFU / mL, pH 3.5–4.0.

[0011] Furthermore, the alkaline solution is a sodium hydroxide solution with a mass concentration of 1% to 5%, which increases the cation exchange capacity of the fly ash after activation, and the pH value is 8.0-10.0; the modified fly ash-based carrier contains ≥5×10⁻⁶ viable lactic acid bacteria. 7 CFU / g.

[0012] Further, the material ratio of the aerobic composting treatment in step S2 is as follows by mass: 70-85 parts of vegetable waste, 10-30 parts of composite straw powder, and 3-10 parts of modified fly ash-based carrier. The composite straw powder is made by mixing wheat straw and corn straw in a mass ratio of 1:1 to 3 and then pulverizing the mixture to a particle size of <1cm. The inoculation amount of the high-temperature composting microbial agent is 2-10 kg / ton of material, and the high-temperature composting microbial agent contains one or more selected from Bacillus pumilus, Bacillus thermophilus, Bacillus amyloliquefaciens, and actinomycetes.

[0013] Furthermore, the aerobic composting treatment includes the following three stages: Low-temperature adaptation phase: The pile body is left to stand for 3 to 5 days, and the temperature naturally rises to 55-60℃. During this period, the moisture content is controlled to decrease from the initial 65% to 70% to 50% to 55%. High-temperature degradation stage: Maintain the pile temperature at 60-65℃, and control the temperature to drop when it reaches 68-70℃ by turning and throwing, continuing for 5-8 days to reduce the moisture content to below 30%. Maturation and stabilization stage: The temperature naturally drops to room temperature, and the compost is left to stand for more than 5 days to obtain mature compost products.

[0014] Furthermore, in the high-temperature degradation stage, the ammonia-containing exhaust gas generated from composting is extracted by a blower, absorbed by spraying, and then introduced into step S3, where it is mixed with vegetable wastewater, carbon source, and inorganic salts before inoculation with lactic acid bacteria.

[0015] Furthermore, in the anaerobic fermentation treatment step, the culture medium formula, by weight, is: 80-90 parts of vegetable wastewater, 4-6 parts of molasses, 4-6 parts of brown sugar, 0.1-0.3 parts of dipotassium hydrogen phosphate, and 0.3-1 parts of lactic acid bacteria powder; the initial pH is adjusted to 5.0-6.0 using one or more of lactic acid, glacial acetic acid, phosphoric acid, and citric acid.

[0016] Furthermore, the anaerobic fermentation process includes two stages: First stage: Fermentation at 33-38℃ for 20-28 hours, until the pH drops to 4.0-4.5 and the viable lactic acid bacteria count is ≥5×10⁻⁶. 8 CFU / mL; Second stage: The temperature is lowered to 23-28℃, and fermentation continues for 16-24 hours until the pH drops to 3.5-4.0 and stabilizes, with a live lactic acid bacteria count ≥1×10⁻⁶. 9 CFU / mL.

[0017] Furthermore, in step S5, where a portion of the fermentation broth is returned to aerobic composting, the return flow rate accounts for 10% to 30% of the total fermentation broth, and the pH of the returned fermentation broth is 3.5 to 4.0. This reflux is used to replace part of the conditioning water and to supplement the microbial agent.

[0018] Further, step S5, which describes using the remaining fermentation liquid to prepare liquid fertilizer, includes: combining the fermentation liquid with a compound inorganic nitrogen source, a compound inorganic phosphorus source, a compound inorganic potassium source, chelated trace elements, potassium humate, polyglutamic acid, trehalose, microbial agents, and a suspending agent to prepare liquid fertilizer. The mature compost product is crushed to below 80 mesh to obtain fine compost powder; the fine compost powder is mixed with a portion of fermentation liquid and binder, and then granulated and dried to obtain granular compound microbial fertilizer.

[0019] Furthermore, the liquid fertilizer comprises the following mass fractions: 70-80 parts fermentation broth, 1-2 parts potassium humate, 0.2-0.5 parts polyglutamic acid, 2-4 parts trehalose, 1-3 parts microbial inoculant, 0.2-0.5 parts suspension concentrate, and the remaining 15-20 parts are compound inorganic nitrogen source, compound inorganic phosphorus source, and compound inorganic potassium source. The proportions of the compound inorganic nitrogen source, compound inorganic phosphorus source, and compound inorganic potassium source are adjusted according to the crop growth requirements, and the proportions can be 1:1:1 or 2:1:1, with a total of 100 parts.

[0020] Furthermore, the adhesive is one or more of bentonite, attapulgite, or xanthan gum; the vacuum concentration adopts a multi-effect evaporator with an evaporation temperature of 60-85℃ and a vacuum degree of -0.09 to -0.06MPa.

[0021] Furthermore, the mature compost product can partially replace the compound straw powder in the next batch of aerobic compost, with a replacement ratio of 50% to 90%, and can be recycled 5 to 8 times.

[0022] Furthermore, the waste vegetables are leafy vegetable waste, including one or more of Chinese cabbage, baby bok choy, lettuce, romaine lettuce, and coriander; the solid-liquid separation is performed using a screw extruder or a screw press dewatering machine, and the water content of the waste vegetable residue after separation is 70% to 80%.

[0023] A second aspect of this application provides a compound microbial fertilizer prepared using the process described above.

[0024] The present invention has the following beneficial effects: This invention achieves efficient resource utilization of all components of vegetable waste by separating the solid and liquid phases of wastewater and then subjecting them to aerobic composting and anaerobic fermentation, respectively. It also establishes a technical system for recycling ammonia-containing waste gas, returning fermentation liquid, and reusing mature compost products. Specifically, wastewater residue is mixed with composite straw powder and modified fly ash-based carrier for aerobic composting. The modified fly ash-based carrier not only adjusts the compost structure and improves aeration, but the lactic acid bacteria it carries also synergistically enhance degradation efficiency and shorten the composting cycle with high-temperature composting agents. Simultaneously, the lactic acid bacteria produce lactic acid, which reduces the volatilization of ammonium nitrogen, achieving nitrogen fixation and odor reduction. Wastewater from the wastewater is anaerobically fermented to prepare a highly active fermentation liquid, part of which is returned to aerobic composting to adjust moisture content and replenish effective microbial agents. The remaining fermentation liquid is then granulated with mature compost products, improving the nutritional balance and microbial activity of the fertilizer. The resource utilization of ammonia-containing waste gas replenishes the nitrogen source for anaerobic fermentation while reducing nitrogen loss and odor pollution. Furthermore, the decomposed compost products can partially replace compound straw powder for recycling, reducing material costs. This process effectively solves problems such as high moisture content, poor aeration, and unbalanced nutrition in vegetable waste compost, as well as the difficulty in treating vegetable wastewater and its tendency to emit odors. The prepared compound microbial fertilizer combines the long-lasting fertilization characteristics of organic fertilizer with the growth-promoting function of microbial agents, resulting in significant economic, environmental, and ecological benefits. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this drawing or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this drawing. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0026] Figure 1 This is a process flow diagram of the present invention.

[0027] The purpose, features, and advantages of this accompanying drawing will be further explained in conjunction with the embodiments and with reference to the accompanying drawing. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the following description and illustration are provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0029] Obviously, the following description is merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0030] An embodiment of the first aspect of this application provides a process for treating vegetable waste as fertilizer, including the following steps: S1: Separate the vegetable waste into solid and liquid components to obtain vegetable residue and vegetable wastewater, respectively. S2: Mix the vegetable waste with composite straw powder and modified fly ash-based carrier, inoculate with high-temperature composting microbial agent, and carry out aerobic composting treatment to obtain mature compost products. S3: Mix the wastewater from the vegetable tail with a carbon source and inorganic salts, inoculate with lactic acid bacteria, and carry out anaerobic fermentation under anaerobic conditions to obtain fermentation liquid; S4: The ammonia-containing tail gas generated during the aerobic composting process described in step S2 is sprayed and absorbed, and then introduced into step S3 as a nitrogen source to supplement and adjust the pH of the fermentation liquid. S5: A portion of the fermentation liquid is returned to the aerobic composting treatment step in step S2 to adjust the moisture content of the compost material and replenish the microbial agent; the remaining fermentation liquid is used to prepare liquid fertilizer. The decomposed compost products are granulated and dried to obtain granular compound microbial fertilizer.

[0031] See Figure 1 In step S1, the vegetable waste from the wastewater treatment plant is crushed and compressed using a screw press. The wastewater is mainly leafy vegetables, including one or more of the following: Chinese cabbage, baby bok choy, lettuce, romaine lettuce, and cilantro. The solid-liquid separation is performed using a screw press or a screw press dewatering machine. After separation, the wastewater residue has a moisture content of 70%–80%. The wastewater residue is transported to an aerobic composting site, mixed with other materials, and then composted for fermentation to prepare solid fertilizer. The wastewater from the wastewater is pumped into an anaerobic fermentation tank for anaerobic fermentation treatment.

[0032] The preparation method of the modified fly ash-based carrier in step S2 includes: mixing fly ash (with qualified heavy metal test results) with an alkaline solution, activating it at 80-100℃ for 1-3 hours, washing and drying it to obtain activated fly ash; mixing the activated fly ash with fermentation broth at a solid-liquid ratio of 1:5-15, adsorbing it for 10-24 hours, filtering it and drying it until the moisture content is ≤10% to obtain the modified fly ash-based carrier.

[0033] The fermentation broth is the fermentation broth obtained in the wastewater fermentation treatment step, and its viable lactic acid bacteria count is ≥1×10⁻⁶. 9 CFU / mL, pH 3.5–4.0.

[0034] Furthermore, the alkaline solution is a sodium hydroxide solution with a mass concentration of 1% to 5%, which increases the cation exchange capacity of the fly ash after activation, and the pH value is 8.0-10.0.

[0035] Modified fly ash-based carriers play multiple roles in aerobic composting systems: First, the porous structure formed after alkali activation effectively improves the aeration and water retention capacity of the compost pile, preventing compaction and localized anaerobic problems caused by the high moisture content of vegetable waste, and providing a favorable microenvironment for the growth and reproduction of high-temperature composting microorganisms. Second, the highly active lactic acid bacteria loaded on the carrier surface can initiate the decomposition of easily degradable organic matter at the low-temperature stage of composting, forming a synergistic effect with the subsequently proliferating high-temperature composting microorganisms (such as Bacillus pumilus and Bacillus thermophilus), accelerating the degradation of complex organic matter such as cellulose and hemicellulose, thereby shortening the composting cycle. Simultaneously, the lactic acid bacteria produce lactic acid, which also reduces the volatilization of ammonium nitrogen, achieving nitrogen fixation and deodorization effects. Furthermore, the modified fly ash-based carrier has an increased cation exchange capacity, enabling it to adsorb and fix some of the nitrogen and other nutrients released during composting, reducing nutrient loss. At the same time, the silicon, aluminum, and other mineral elements it contains can also be slowly released, increasing the mineral nutrient content of the compost products. The introduction of this carrier not only improved composting efficiency and product quality, but also enabled the high-value utilization of industrial solid waste fly ash and reduced composting costs.

[0036] Further, the material ratio for the aerobic composting treatment in step S2, by mass, is: 70-85 parts of vegetable waste, 10-30 parts of composite straw powder, and 3-10 parts of modified fly ash-based carrier. If necessary, the fermentation liquid from step S3 can be introduced, and the mixture should be thoroughly mixed using a turner or loader. At this point, the moisture content of the material is approximately 70%. A high-temperature composting agent is then inoculated, with an inoculation amount of 2-10 kg / ton of material. The high-temperature composting agent comprises one or more selected from Bacillus pumilus, Bacillus thermophilus, Bacillus amyloliquefaciens, and actinomycetes.

[0037] The composite straw powder is made by mixing wheat straw and corn straw in a mass ratio of 1:1 to 3 and then pulverizing them to a particle size of <1 cm; the fly ash comes from a chemical plant or power plant and has a particle size of 10 to 100 μm. Suitable particle size facilitates even mixing with vegetable waste and balances the moisture content during fermentation. Wheat straw helps increase the carbon-to-nitrogen ratio and promotes humus formation, while corn straw can significantly reduce moisture content, decrease leachate, and improve pore structure. Fly ash is alkaline, which can neutralize the organic acids produced by the decay of vegetable waste, preventing excessive acidification of the compost pile. Its porous particle structure helps regulate moisture content and porosity, while also adsorbing odors.

[0038] In this embodiment, the aerobic composting treatment in step S2 includes the following three stages: Low temperature adaptation stage: The pile is left to stand for 3 to 5 days, and the temperature naturally rises to 55-60℃. During this period, the moisture content is controlled to decrease from the initial 65% to 70% to 50% to 55%. The pile does not need to be turned over in this stage. The purpose is to reduce the moisture content of the pile and gradually raise the temperature through the respiration of microorganisms to provide a better porosity environment. The moisture content and temperature of the pile are monitored every 8 hours. High-temperature degradation stage: Maintain the pile temperature at 60-65℃, and control the temperature to drop when it reaches 68-70℃ by turning and turning it over in time. Continue for 5-8 days, and the high-temperature composting stage is basically over, reducing the moisture content to below 30%. During this stage, the activity of thermophilic microorganisms in high-temperature composting is enhanced, they multiply in large numbers, decompose easily degradable organic matter, and the temperature rises to 55-70℃, achieving the harmless treatment and rapid degradation of the vegetable waste. Maturation and stabilization stage: After the moisture content of the compost pile decreases to below 30%, it enters the material maturation stage. During this stage, as the temperature gradually drops to room temperature, the material becomes loose, odorless, and dark brown. The temperature naturally drops to room temperature, and the pile is left to stand for more than 5 days to obtain fully decomposed compost products.

[0039] In this embodiment, a gas collection hood is installed above the compost stacks to collect ammonia-containing waste gas (approximately 300-400 ppm NH3) and introduce it into a spray tower. The spray liquid is a dilute sulfuric acid solution. The reaction principle is: 2NH3 + H2SO4 → (NH4)2SO4. The absorbed ammonium-rich liquid (pH 6-7) can be used as a high-quality nitrogen source. 10-50% of the ammonium-rich liquid is recycled back to the fermentation tank in step S3 (mixed with vegetable wastewater, carbon source, and inorganic salts before inoculation with lactic acid bacteria), or recycled. This step, on the one hand, utilizes the ammonia-containing waste gas generated during aerobic composting, supplementing the nitrogen source for anaerobic fermentation and reducing nitrogen loss; on the other hand, the spray absorption reduces the odor pollution of ammonia to the surrounding environment, achieving synergistic treatment of waste gas reduction and resource utilization.

[0040] Correspondingly, since the vegetable waste treated by high temperature and aerobic composting has good dispersibility, low moisture content, and increased organic matter content, it can serve as about 80-90% of the composite straw powder. After being mixed with purchased composite straw and fly ash, it can be fermented with the vegetable waste for 5-8 times, which greatly reduces the cost of compost materials.

[0041] Preferably, the composted product from step S2 can be mixed with agricultural microbial agents, and the mixture can be used to prepare compound microbial fertilizer (solid). The agricultural microbial agents can be one or more of the following: Bacillus subtilis, Bacillus vesicularis, gelatinous Bacillus, megaterium, Bacillus licheniformis, coagulant Bacillus, lateritic Bacillus, polymyxa, Trichoderma harzianum, Trichoderma viride, Azotobacter chrysophagus, and photosynthetic bacteria. The prepared compound microbial fertilizer conforms to the standard of "NY / T 798-2015 Compound Microbial Fertilizer".

[0042] In this embodiment, the nutrient composition and pH value of the vegetable wastewater were adjusted to prepare a culture medium suitable for anaerobic fermentation of lactic acid bacteria or EM bacteria. The medium comprises the following mass percentages: 80-90 parts vegetable wastewater, 4-6 parts molasses, 4-6 parts EM-fermented brown sugar, 0.1-0.3 parts dipotassium hydrogen phosphate, and 0.3-1 parts lactic acid bacteria powder. The initial pH was adjusted to 5.0-6.0 using one or more of lactic acid, glacial acetic acid, phosphoric acid, and citric acid. Because the protein content in the vegetable wastewater is relatively high, a significant amount of carbon source is needed to balance the pH. Molasses and EM-fermented brown sugar are readily absorbed by lactic acid bacteria or EM bacteria during anaerobic fermentation, while dipotassium hydrogen phosphate provides appropriate inorganic salt supplementation. Adjusting the pH to 5.0-6.0 creates a suitable pH environment for the rapid growth of lactic acid bacteria or EM bacteria. Under this pH environment, lactic acid bacteria or EM bacteria can grow rapidly. Lactic acid, a metabolic product of lactic acid bacteria, can inhibit the growth of other bacteria while inducing the growth of lactic acid bacteria.

[0043] The anaerobic fermentation process involves pumping the prepared culture medium into the anaerobic fermenter, or preparing the wastewater into a culture medium within the anaerobic fermenter. After thorough mixing, fermentation begins at a temperature of 35±2℃, which is suitable for the rapid growth of lactic acid bacteria or EM bacteria. The fermenter is sealed, with ventilation holes. After 40-48 hours of fermentation, the pH stabilizes at 3.5-4.0, and the wastewater changes color from fruit green to reddish-brown with a slightly acidic aroma, indicating successful fermentation.

[0044] Specifically, it includes two stages: First stage: Fermentation at 33-38℃ for 20-28 hours, until the pH drops to 4.0-4.5 and the viable lactic acid bacteria count is ≥5×10⁻⁶. 8 CFU / mL; Second stage: The temperature is lowered to 23-28℃, and fermentation continues for 16-24 hours until the pH drops to 3.5-4.0 and stabilizes, with a live lactic acid bacteria count ≥1×10⁻⁶. 9 CFU / mL.

[0045] This anaerobic fermentation process employs a two-stage temperature control method, which ensures the rapid proliferation of lactic acid bacteria at a suitable temperature while simultaneously promoting the accumulation of metabolites through moderate cooling in the later stage, thus ensuring that the activity and quantity of lactic acid bacteria in the fermentation broth reach the optimal state.

[0046] The highly active fermentation broth, after fermentation, is partially returned to the aerobic composting system to regulate moisture content and supplement highly effective functional microbial agents. The remainder is used as a core functional component in the preparation of liquid fertilizer. Another portion is used for compound granulation. During granulation, the fermentation broth not only provides abundant active lactic acid bacteria for the granular fertilizer, but its organic acids, small molecule peptides, and other metabolites also improve the physicochemical properties of the compost granules, enhance intergranular adhesion, and increase granulation efficiency and strength. Simultaneously, the nutrients in the fermentation broth synergistically enhance the organic matter and mineral elements in the mature compost, significantly improving the nutritional comprehensiveness and biological activity of the final compound microbial fertilizer. When applied to the soil, this fertilizer not only slowly releases nutrients for crop absorption but also improves the soil's microecological environment through beneficial microorganisms such as lactic acid bacteria, promoting crop growth.

[0047] In this embodiment, in step S5, where a portion of the fermentation broth is returned to aerobic composting, the return volume accounts for 10% to 30% of the total fermentation broth, and the pH of the returned fermentation broth is 3.5 to 4.0. This returned broth is used to replace part of the conditioning water and to supplement the microbial agent. This step not only precisely adjusts the moisture content of the aerobic compost material to the range of 50% to 55%, avoiding the problems of excessively high local humidity or nutrient dilution that may occur with traditional water conditioning, but also ensures that the returned fermentation broth is rich in highly active lactic acid bacteria. These lactic acid bacteria can rapidly colonize and participate in the decomposition of organic matter in the early stages of composting, forming a synergistic effect with the high-temperature composting microbial agent, further accelerating the composting process.

[0048] In this embodiment, step S5, which involves using a portion of the fermentation broth to prepare liquid fertilizer, includes: compounding the fermentation broth with a compound inorganic nitrogen source, a compound inorganic phosphorus source, a compound inorganic potassium source, chelated trace elements, potassium humate, polyglutamic acid, trehalose, microbial agents, and a suspending agent to prepare liquid fertilizer. Preferably, the liquid fertilizer contains the following proportions by mass: 70-80 parts fermentation broth, 1-2 parts potassium humate, 0.2-0.5 parts polyglutamic acid, 2-4 parts trehalose, 1-3 parts microbial agents, 0.2-0.5 parts suspending agent, and the remaining 15-20 parts are compound inorganic nitrogen source, compound inorganic phosphorus source, and compound inorganic potassium source; the proportions of the compound inorganic nitrogen source, compound inorganic phosphorus source, and compound inorganic potassium source are adjusted according to the crop growth requirements, and the ratio can be 1:1:1 or 2:1:1, with a total of 100 parts. Microbial inoculants can be one or more of the following Bacillus subtilis, Bacillus vesicae, gelatinous Bacillus, megaterium, Bacillus licheniformis, coagulant Bacillus, lateritic Bacillus, and polymyxa, with a concentration of over 10 billion CFU / g. The compound inorganic salts (nitrogen, phosphorus, and potassium) are selected from fully water-soluble fertilizers, and the suspending agent is selected from non-bacterial agents such as xanthan gum and anionic guar gum. The addition of compound inorganic salts in the preparation of liquid fertilizer from fermented vegetable wastewater is to establish a high-salt environment, inhibiting the growth of miscellaneous bacteria and Bacillus activation. Potassium humate provides a good carbon source environment for Bacillus survival, while polyglutamic acid and trehalose act as protectants to stabilize the Bacillus environment. The purpose of the suspending agent is to ensure the uniformity of the liquid fertilizer.

[0049] The mature compost product is crushed to below 80 mesh to obtain fine compost powder; the fine compost powder is mixed with a portion of fermentation liquid and binder, and then granulated and dried to obtain granular compound microbial fertilizer.

[0050] A portion of the fermentation broth, mature compost products, and binder are mixed at a mass ratio of 1:3–5:0.1–0.2. During the mixing process, the active lactic acid bacteria, organic acids, and abundant soluble nutrients in the fermentation broth can penetrate into the interior of the mature compost granules, enhancing the microbial activity and nutrient availability of the final fertilizer. The mixed material is granulated using a twin-screw extruder, with the particle diameter controlled at 3–5 mm. Subsequently, it is dried under hot air at 60–70°C until the moisture content is ≤25%, ultimately obtaining uniform granular compound microbial fertilizer.

[0051] This granular compound microbial fertilizer combines the long-lasting effect of organic fertilizer with the growth-promoting effect of microbial agents. According to the test, its effective live bacteria count is ≥0.2 billion CFU / g, the organic matter mass fraction is ≥30%, and the total nutrient (N+P2O5+K2O) mass fraction is ≥8%. All indicators meet the requirements of the standard "NY / T 798-2015 Compound Microbial Fertilizer".

[0052] The adhesive is one or more of bentonite, attapulgite, or xanthan gum.

[0053] The remaining fermentation broth was concentrated under reduced pressure using a multi-effect evaporator with an evaporation temperature of 60–85°C and a vacuum degree of -0.09–-0.06 MPa.

[0054] Example The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight. Unless otherwise stated, all reagents used in the examples are available commercially or synthesized using conventional methods and are ready for use without further processing. Unless otherwise stated, all instruments used in the examples are available commercially.

[0055] Source of microbial agent: Lactobacillus plantarum preservation number GDMCC NO.1.648; Bacillus pumilus, preservation number GDMCC NO.802798, from Guangdong Institute of Microbiology; The actinomycete has the preservation number GDMCC NO.4.160 and originates from the China Industrial Microbial Culture Collection Center. Pediococcus pentosaceus, purchase number bio-02796, purchased from Beijing BioBio Biotechnology Co., Ltd. Thermophilic denitrifying Bacillus, purchase number bio-18499, was purchased from Beijing BioBio Biotechnology Co., Ltd.

[0056] Preparation Example Preparation of modified fly ash-based carrier: Take 100 kg of fly ash, focusing on testing the content of arsenic, cadmium, lead, chromium, and mercury to avoid using biological carriers containing metal risks. Add qualified fly ash to 300 L of 2% NaOH solution, stir at 90℃ for 2 hours to depolymerize the aluminosilicate framework and increase porosity. Wash with deionized water to pH 9.0, and dry at 105℃ to obtain 95 kg of activated fly ash. Take the activated fly ash and mix it with the fermentation broth (pH 3.8) obtained in step 2 of Example 1 at a solid-liquid ratio of 1:8. Let it stand for adsorption for 12 hours to further fix trace heavy metals in an acidic environment and preload some organic matter. Filter and dry at 30℃ with ventilation to a moisture content of 10% to obtain the modified fly ash-based biological carrier.

[0057] Example 1 Step 1: Add 4.5 tons of vegetable wastewater to the fermentation tank, along with 0.2 tons of molasses, 0.2 tons of EM-fermented brown sugar, and 6 kg of dipotassium hydrogen phosphate. Stir to dissolve, maintain the temperature at 90℃ for 30 minutes for pasteurization to kill bacteria in the wastewater, cool to 35℃, and adjust the pH to 5.5 with lactic acid.

[0058] Inoculate with 12 kg of lactic acid bacteria powder (Lactobacillus plantarum: Pediococcus pentosaceus = 3:1, viable count ≥ 2 × 10⁻⁶). 10 (CFU / g), ferment at 35℃ for 24 hours; then cool to 28℃ and continue fermentation for 24 hours.

[0059] After 48 hours of fermentation, the pH was 3.8 and the viable count of lactic acid bacteria was ≥1.0×10⁻⁶. 9 CFU / mL, with a strong sour aroma. 0.45 tons of fermentation broth A was extracted for refluxing compost and for material conditioning in step 2; the remaining approximately 4.0 tons of fermentation broth B was temporarily stored in a sterile storage tank (of which 0.15 tons were used for subsequent granulation, and 3.85 tons were used to prepare liquid fertilizer or reuse in the next batch).

[0060] Step 2: Mix 1.5 tons of vegetable waste (75% moisture content), 0.35 tons of composite straw powder (wheat:corn = 1:2, particle size <1cm), and 0.075 tons of modified fly ash-based carrier, while simultaneously spraying 0.45 tons of fermentation liquid A (pH 3.8), so that the total mass of the mixture is 2.375 tons and the moisture content is 68%. Inoculate with 5 kg of high-temperature composting microbial agent (Bacillus pumilus: Bacillus thermophilus: Actinomycetes = 2:1:1), pile into windrows (base width 2.5m, height 1.2m), and cover with a semi-permeable membrane to keep warm and moist; Composting process: Days 1-3 are the low-temperature period, with the temperature rising above 50℃; Days 4-12 are the high-temperature period, with daily temperature monitoring. When the temperature reaches 65℃, the compost is turned over, for a total of 6 times; Days 13-20 are the maturation period, with the temperature dropping below 40℃. A gas collection hood is installed above the compost stacks to collect ammonia-containing waste gas. During the high-temperature period, the blower is turned on from 10:00 AM to 4:00 PM daily to introduce the compost exhaust gas (containing approximately 350 ppm NH3) into a spray tower. The spray solution is a dilute sulfuric acid solution, which absorbs the ammonia-rich liquid (pH 6-7). Approximately 50 liters of the ammonia-rich liquid are returned to the fermentation tank from step 1 (added before sterilization as a supplementary nitrogen source), and the remainder is recycled.

[0061] Step 3: Crush the mature compost product (approximately 0.45) to 60-80 mesh. Mix 0.40 tons of fine powder with 0.25 tons of bentonite, add 30 kg of Bacillus subtilis and Bacillus thuringiensis powder (live count ≥10 billion / g), mix thoroughly in a mixer, slowly spray in approximately 0.15 tons of fermentation liquid B, form a soft material, granulate using a disc granulator, and dry to a moisture content of 20% to obtain compound bio-fertilizer; The remaining approximately 3.85 tons of fermentation liquid B was combined with 795 kg of compound inorganic nitrogen, phosphorus, and potassium source, 75 kg of potassium humate, 15 kg of polyglutamic acid, 150 kg of trehalose, 100 kg of Bacillus subtilis inoculant, and 15 kg of suspension concentrate to produce liquid fertilizer.

[0062] The compound bio-fertilizer (solid and liquid) products prepared in Example 1 were tested, and the test results are shown in Tables 1 and 2: Table 1. Test results of main indicators of compound microbial fertilizer (solid)

[0063] Table 2. Test results of main indicators of compound microbial fertilizer (liquid)

[0064] As shown in the table above, the effective viable bacteria count of the compound microbial fertilizer (solid) prepared using this process is 9.8 × 10⁻⁶. 7 CFU / g, organic matter 41%, total nutrients 9.0%, pH 6.8; compound microbial fertilizer (liquid) with 2.5 × 10⁻⁶ effective viable bacteria. 8 The CFU / mL concentration, total nutrients of 8.41%, and pH of 6.4 all meet the standards of "NY / T 798-2015 Compound Microbial Fertilizer".

[0065] In the next batch of composting, the mature compost products were used to replace the fresh straw powder, and the amount of modified fly ash-based carrier was reduced accordingly. The above process was repeated and operated continuously for 6 months with stable results.

[0066] Example 2 This embodiment is basically the same as Embodiment 1, except that the amount of modified fly ash-based biological carrier added is changed to 0.15 tons.

[0067] Results: The compost heated up slightly faster, and the high-temperature period lasted for 8 days, but the residual fly ash in the composted products was slightly higher, with a total nutrient content of 9.2%.

[0068] Example 3 This embodiment is basically the same as embodiment 1, except that in step 1, after inoculating with lactic acid bacteria powder, it is fermented at 38°C for 24 hours, and then cooled to 25°C and fermented for another 24 hours.

[0069] Results: After 24 hours of fermentation, the pH dropped to 4.2, and after 48 hours, the pH reached 3.9. The viable count of lactic acid bacteria was 1.0 × 10⁻⁶. 9 CFU / mL, composting effect is the same.

[0070] Example 4 This embodiment is basically the same as embodiment 1, except that in step 1, glacial acetic acid is used to adjust the initial pH of the wastewater to 5.5.

[0071] Results: The pH dropped to 4.3 after 24 hours of fermentation and reached 4.0 after 48 hours; the viable count of lactic acid bacteria was 8.5 × 10⁻⁶. 8 The CFU / mL concentration was slightly weaker than that in Example 1. The heating rate and duration of the high-temperature period during the subsequent composting process were basically the same as in Example 1. The final solid compound microbial fertilizer had an effective viable count of 8.9 × 10⁻⁶ CFU / mL. 7 CFU / g, organic matter 39%, total nutrients 8.8%; liquid compound microbial fertilizer with 2.2×10⁻⁶ effective viable bacteria. 8 The CFU / mL and total nutrient content of 8.35% still meet the standards of "NY / T 798-2015 Compound Microbial Fertilizer".

[0072] Comparative Example 1 This comparative example is basically the same as Example 1, except that the modified carrier loading step is omitted in step 2, and 0.075 tons of ordinary fly ash (unactivated) are used directly.

[0073] Results: The composting temperature rose more slowly, reaching 55℃ on the 5th day, with a high-temperature period of only 6 days and a total cycle of 18 days. The composting products contained 39% organic matter and 8.5% total nutrients.

[0074] Comparative Example 2 This comparative example is basically the same as Example 1, except that the operation of extracting 0.45 tons of fermentation liquid A for reflux in step 2 is cancelled, and an equal amount of clean water is used to adjust the compost moisture content.

[0075] Results: The compost heated up slightly, with a high-temperature period of 7 days. The organic matter content of the mature product was 40%, and the total nutrient content was 8.8%. After concentration and granulation of the fermentation broth, the viable cell count of the product was 3.0 × 10⁻⁶. 7 CFU / g.

[0076] Comparative Example 3 This comparative example is basically the same as Example 1, except that in step 1, after inoculating with lactic acid bacteria powder, the fermentation was carried out at a constant temperature of 35°C for 48 hours.

[0077] Results: The fermentation broth pH was 4.0, and the viable count of lactic acid bacteria was 8.0 × 10⁻⁶. 8 The concentration of CFU / mL indicates less accumulation of metabolites, resulting in slightly poorer product storage stability.

[0078] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A process for treating vegetable waste as fertilizer, characterized in that, Includes the following steps: S1: Separate the vegetable waste into solid and liquid components to obtain vegetable residue and vegetable wastewater, respectively. S2: Mix the vegetable waste with composite straw powder and modified fly ash-based carrier, inoculate with high-temperature composting microbial agent, and carry out aerobic composting treatment to obtain mature compost products. S3: Mix the wastewater from the vegetable tail with a carbon source and inorganic salts, inoculate with lactic acid bacteria, and carry out anaerobic fermentation under anaerobic conditions to obtain fermentation liquid; S4: The ammonia-containing tail gas generated during the aerobic composting process described in step S2 is sprayed and absorbed, and then introduced into step S3 as a nitrogen source to supplement and adjust the pH of the fermentation liquid. S5: A portion of the fermentation liquid is returned to the aerobic composting treatment step in step S2 to adjust the moisture content of the compost material and replenish the microbial agent; the remaining fermentation liquid is used to prepare liquid fertilizer. The decomposed compost products are granulated and dried to obtain granular compound microbial fertilizer.

2. The process for treating vegetable waste as fertilizer according to claim 1, characterized in that, The preparation method of the modified fly ash-based carrier in step S2 includes: Fly ash is mixed with an alkaline solution and activated at 80–100°C for 1–3 hours. After washing and drying, activated fly ash is obtained. The activated fly ash is mixed with fermentation broth at a solid-liquid ratio of 1:5–15 and adsorbed for 10–24 hours. After filtration, it is dried until the moisture content is ≤10%, thus obtaining a modified fly ash-based carrier.

3. The process for treating vegetable waste as fertilizer according to claim 1, characterized in that, The material ratio for the aerobic composting treatment in step S2 is as follows by mass: 70-85 parts of vegetable waste, 10-30 parts of composite straw powder, and 3-10 parts of modified fly ash-based carrier. The composite straw powder is made by mixing wheat straw and corn straw in a mass ratio of 1:1 to 3 and then pulverizing the mixture to a particle size of <1cm. The inoculation amount of the high-temperature composting microbial agent is 2-10 kg / ton of material, and the high-temperature composting microbial agent contains one or more selected from Bacillus pumilus, Bacillus thermophilus, Bacillus amyloliquefaciens, and actinomycetes.

4. The process for treating vegetable waste as fertilizer according to claim 3, characterized in that, The aerobic composting process includes the following three stages: Low-temperature adaptation phase: The pile body is left to stand for 3-5 days, and the temperature naturally rises to 55-60℃. During this period, the moisture content is controlled to decrease from the initial 65%-70% to 50%-55%. High-temperature degradation stage: Maintain the pile temperature at 60-65℃, and control the temperature to drop when it reaches 68-70℃ by turning and throwing, continuing for 5-8 days to reduce the moisture content to below 30%. Maturation and stabilization stage: The temperature naturally drops to room temperature, and the compost is left to stand for more than 5 days to obtain mature compost products.

5. The process for treating vegetable waste as fertilizer according to claim 4, characterized in that, In the high-temperature degradation stage, the ammonia-containing exhaust gas generated from composting is extracted by a blower, absorbed by spraying, and then introduced into step S3. Before inoculating with lactic acid bacteria, it is mixed with vegetable wastewater, carbon source, and inorganic salts.

6. The process for treating vegetable waste as fertilizer according to claim 1, characterized in that, In the anaerobic fermentation treatment step, the culture medium formula by weight is as follows: 80-90 parts of vegetable wastewater, 4-6 parts of molasses, 4-6 parts of brown sugar, 0.1-0.3 parts of dipotassium hydrogen phosphate, and 0.3-1 parts of lactic acid bacteria powder; the initial pH is adjusted to 5.0-6.0 using one or more of lactic acid, glacial acetic acid, phosphoric acid, and citric acid.

7. The process for treating vegetable waste as fertilizer according to claim 1, characterized in that, The anaerobic fermentation process includes two stages: First stage: Fermentation at 33-38℃ for 20-28 hours, until the pH drops to 4.0-4.5 and the viable lactic acid bacteria count is ≥5×10⁻⁶. 8 CFU / mL; Second stage: The temperature is lowered to 23-28℃, and fermentation continues for 16-24 hours until the pH drops to 3.5-4.0 and stabilizes, with a live lactic acid bacteria count ≥1×10⁻⁶. 9 CFU / mL.

8. The process for treating vegetable waste as fertilizer according to claim 1, characterized in that, In step S5, where a portion of the fermentation broth is returned to aerobic composting, the return flow rate accounts for 10% to 30% of the total fermentation broth, and the pH of the returned fermentation broth is 3.5 to 4.

0. This reflux is used to replace part of the conditioning water and to supplement the microbial agent.

9. The process for treating vegetable waste as fertilizer according to claim 1, characterized in that, Step S5, which describes using the remaining fermentation liquid to prepare liquid fertilizer, includes: combining the fermentation liquid with a compound inorganic nitrogen source, a compound inorganic phosphorus source, a compound inorganic potassium source, chelated trace elements, potassium humate, polyglutamic acid, trehalose, microbial agents, and a suspending agent to prepare liquid fertilizer; The mature compost product is crushed to below 80 mesh to obtain fine compost powder; the fine compost powder is mixed with a portion of fermentation liquid and binder, and then granulated and dried to obtain granular compound microbial fertilizer.

10. A compound microbial fertilizer prepared using the process described in any one of claims 1-9.

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