Composting method for efficiently degrading lignin

Abstract

The invention provides a composting method capable of efficiently degrading lignin, and belongs to the field of organic waste resource utilization, the composting method comprises the following steps: adding a lignin degrading bacterial agent into a mixed material of organic waste, turning, standing, putting earthworms, adding vanillin, composting, controlling the environment temperature to be 20-30 DEG C, and controlling the temperature to be 20-30 DEG C; controlling the water content to be 55-65%, turning the pile at regular intervals until the pile is completely decomposed, and screening out earthworms and impurities to obtain the organic fertilizer. According to the method, a three-dimensional synergistic system of the earthworms, the lignin degrading bacteria and the inducer is constructed, the biological activity of the earthworms and the metabolism effect of microorganisms are fully utilized, decomposition and conversion of complex organic matter in organic waste are promoted, stable humus is formed, vanillin is added to serve as the inducer, the activity of the lignin degrading bacteria is further stimulated, and the activity of the lignin degrading bacteria is improved. The degradation efficiency of lignin is remarkably improved, the composting period is shortened, and meanwhile, the quality of organic fertilizer is improved.

Description

Technical Field

[0001] This invention relates to the field of organic waste resource utilization technology, specifically to a composting method for efficiently degrading lignin. Background Technology

[0002] With the rapid development of agriculture and livestock farming, the harmless treatment and resource utilization of large quantities of organic waste such as crop straw and livestock manure have become important issues for environmental protection and circular agriculture. Composting technology, as a core means of realizing the resource transformation of organic waste, has been widely used and continuously optimized in recent years.

[0003] Currently, composting technology mainly includes the following categories: (1) Conventional composting technology: Organic waste such as livestock and poultry manure and crop straw are piled together and fermented by microorganisms. During this process, microorganisms decompose organic matter and produce heat, carbon dioxide and water. Intermittent ventilation and moisture regulation promote microbial metabolism. This process has a low cost but the composting cycle is long, lasting from several weeks to several months, and the degradation efficiency for complex organic matter such as lignin is insufficient. (2) Vermicomposting technology: Vermicomposting technology utilizes earthworms to ingest and digest organic materials, and the process of digesting and excreting vermicompost in their bodies to achieve composting. Fertilizer, earthworm activity can improve the physical structure of compost materials, increase aeration and water retention, and the microorganisms in the earthworm intestines also help decompose organic matter. However, earthworm activity is strictly limited to the temperature threshold of 15-30℃, and the ability to decompose stubborn organic matter is limited, making it difficult to achieve efficient and stable treatment; (3) Lignin degrading bacteria composting technology: by adding specific lignin degrading bacteria from the outside to enhance the lignin enzymatic hydrolysis process, but functional strains are easily inhibited by competition from native microorganisms, the degradation effect is unstable, and a single bio-enhancing mode cannot comprehensively improve the physical structure and nutrient conversion efficiency of the compost.

[0004] In summary, existing composting methods have the following drawbacks: First, low lignin degradation efficiency leads to excessively long composting cycles and unstable product quality; second, the lack of a multi-dimensional synergistic degradation system makes it difficult to overcome the limitations of single technologies; and third, the lack of a precise control mechanism for the compost micro-ecological environment results in poor system resistance to interference and poor process repeatability. Therefore, there is an urgent need to develop a new composting method that can shorten the composting cycle, achieve efficient and stable lignin degradation, and has strong adaptability to process conditions. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a composting method for efficiently degrading lignin, aiming to solve the technical problems existing in the current composting technology, such as long decomposition cycle, insufficient degradation of complex organic matter such as lignin, low composting efficiency, and great influence from environmental factors.

[0006] In a first aspect, the present invention provides a composting method for efficiently degrading lignin, comprising the following steps: Add lignin-degrading bacteria to the mixture of organic waste, turn the pile over and let it stand, then add earthworms, add vanillin and compost. Control the ambient temperature at 20~30℃ and the moisture content at 55%~65%. Turn the pile over regularly until it is fully decomposed. Remove earthworms and impurities to obtain organic fertilizer.

[0007] Preferably, the mixture of organic waste is obtained by mixing organic waste and then adding water to adjust the moisture content; the moisture content of the mixture of organic waste is 50% to 60%.

[0008] Preferably, organic waste includes livestock and poultry manure, crushed crop straw, and / or crushed garden waste.

[0009] Preferably, the size of the crushed crop straw is 1-5cm; the size of the crushed garden waste is 1-5cm.

[0010] Preferably, the inoculum amount of lignin-degrading microbial agent is 0.5% to 2% of the mass of the mixture.

[0011] Preferably, the lignin-degrading microbial agent includes at least one of white-rot fungi and brown-rot fungi.

[0012] Preferably, the effective viable count of the lignin-degrading microbial agent is 1.0 × 10⁻⁶. 8 ~1.0×10 10 cfu·g -1 .

[0013] Preferably, the earthworm release density is 500-2000 earthworms per cubic meter.

[0014] Preferably, the amount of vanillin added is 0.1% to 0.5% of the mass of the mixture.

[0015] Preferably, regular turning of the pile is carried out every 5 to 7 days.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a highly efficient lignin-degrading composting method that combines the physical turning of earthworms, the intestinal microbiome, and the enzymatic hydrolysis of specific lignin-degrading bacteria to construct a multi-dimensional synergistic degradation system. This significantly improves the lignin degradation efficiency during composting, shortens the maturation period, effectively reduces lignin residue in compost products, and enhances fertilizer efficiency and product quality. Simultaneously, by precisely controlling parameters such as temperature, moisture, and turning during the composting process, an optimal environment is provided for the interaction of earthworms and lignin-degrading bacteria. This refined management, combined with their deep synergy, not only promotes nutrient conversion and accumulation but also enhances the stability and anti-interference ability of the composting process, making it more stable and reliable and improving the quality of the final fertilizer product. Detailed Implementation

[0017] The embodiments of the technical solution of the present invention will be described in detail below. These embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore merely examples and should not be used to limit the scope of protection of the present invention.

[0018] To address the technical problems of long composting cycles, insufficient degradation of complex organic matter such as lignin, low composting efficiency, and significant susceptibility to environmental factors in existing composting technologies, this invention provides a highly efficient composting method for degrading lignin. This method utilizes the synergistic effect of earthworms, lignin-degrading bacteria, and an inducer to shorten composting time, increase the degradation rate of lignin, improve the quality and fertilizer efficiency of compost products, and simultaneously reduce the stringent environmental requirements of the composting process, thereby achieving efficient and stable compost production.

[0019] In a first aspect, embodiments of the present invention provide a composting method for efficiently degrading lignin, comprising the following steps: Add lignin-degrading bacteria to the mixture of organic waste, turn the pile over and let it stand, then add earthworms, add vanillin and compost. Control the ambient temperature at 20~30℃ and the moisture content at 55%~65%. Turn the pile over regularly until it is fully decomposed. Remove earthworms and impurities to obtain organic fertilizer.

[0020] In the technical solution of this invention, the earthworm's activity improves the aeration and structure of compost material, while its intestinal microorganisms promote the decomposition of organic matter. Lignin-degrading bacteria secrete specific enzyme systems to specifically degrade complex organic matter such as lignin. Vanillin, as an inducer, activates the metabolic activity of the lignin-degrading bacteria, further enhancing degradation efficiency. These three elements work synergistically to form a multidimensional degradation system, significantly shortening the composting cycle and improving the quality of the compost product. This invention also optimizes the refined management of the composting process by real-time monitoring of pile temperature and moisture changes, and by regularly turning and replenishing the pile, ensuring that the compost micro-ecological environment is always in optimal condition.

[0021] Furthermore, in some embodiments, the mixture of organic waste is obtained by mixing organic waste and then adjusting it with water; the moisture content of the mixture of organic waste is 50% to 60%.

[0022] Furthermore, in some embodiments, the organic waste includes livestock and poultry manure, crop straw shreds, and / or garden waste shreds.

[0023] Furthermore, in some embodiments, the size of the crop straw shredded material is 1-5 cm; the size of the garden waste shredded material is 1-5 cm.

[0024] In the technical solution of this invention, crop straw and garden waste are crushed to 1-5 cm to facilitate ingestion by earthworms and attachment by microorganisms, thereby improving the decomposition efficiency of organic matter during composting. The crushed material has a larger specific surface area, which is conducive to the rapid colonization of microbial communities and the enzymatic reaction. At the same time, it can also improve the aeration and humidity distribution of the compost pile, creating a more suitable micro-ecological environment for earthworms and lignin-degrading bacteria.

[0025] Furthermore, in some embodiments, the inoculum amount of lignin-degrading microbial agent is 0.5% to 2% of the mass of the mixture.

[0026] In the technical solution of this invention embodiment, by optimizing the dosage of lignin-degrading microbial agent, it is possible to ensure efficient lignin degradation while avoiding resource waste or disruption of the composting system balance caused by excessive addition. Furthermore, inoculating the microbial agent at the initial stage of composting ensures early colonization and activation of enzyme activity.

[0027] Furthermore, in some embodiments, the settling time is 6 to 12 hours.

[0028] In the technical solution of this invention embodiment, after adding the lignin-degrading microbial agent, the microbial solution is evenly distributed in the material by turning the pile, and then left to stand for 6-12 hours to allow the mycelium to initially colonize the material surface. Furthermore, in some embodiments, the lignin-degrading microbial agent includes at least one of white-rot fungi and brown-rot fungi.

[0029] Furthermore, in some embodiments, the effective viable count of the lignin-degrading microbial agent is 1.0 × 10⁻⁶. 8 ~1.0×10 10 cfu·g -1 .

[0030] Furthermore, in some embodiments, the earthworm release density is 500-2000 earthworms per cubic meter.

[0031] Furthermore, in some embodiments, the amount of vanillin added is 0.1% to 0.5% of the mass of the mixture.

[0032] In the technical solution of this invention embodiment, vanillin, as a natural phenolic compound, can stimulate the metabolic activity of lignin-degrading bacteria and enhance their ability to secrete key enzymes such as lignin peroxidase and laccase, thereby accelerating the lignin decomposition process. Simultaneously, vanillin has no significant inhibitory effect on the physiological activities of earthworms, ensuring that the synergistic effect between earthworms and lignin-degrading bacteria is fully realized.

[0033] Furthermore, in some embodiments, periodic turning specifically refers to turning the pile once every 5 to 7 days.

[0034] In the technical solution of this invention embodiment, during the composting process, the regular turning operation can not only evenly mix the materials in the pile, but also enhance ventilation, effectively regulate the oxygen content and temperature distribution of the pile, and prevent the occurrence of local anaerobic or overheating phenomena.

[0035] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0036] In the following embodiments of the present invention, the white-rot fungus (Phanerochaete chrysosporium) was purchased from BNCC (No.: BNCC336258); the viable count of the white-rot fungus in the experiment was 5.0 × 10⁻⁶. 8 cfu·g -1 .

[0037] Brown rot fungus (Fomitopsis palustris) was purchased from NBRC (No.: NBRC30339); the viable count of the brown rot fungus in the experimental culture was 8.0 × 10⁻⁶. 9 cfu·g -1 .

[0038] Example 1 A highly efficient composting method for degrading lignin, comprising the following steps: (1) Raw material pretreatment and mixing: The corn stalks are pre-crushed to a size of 2-3 cm. The cow manure and the crushed corn stalks are mixed evenly at a mass ratio of 4:1. The initial moisture content of the mixture is adjusted to 55% by spraying water. (2) Microbial inoculant inoculation: The white rot fungus (Phanerochaete chrysosporium) liquid is evenly sprayed on the surface of the mixture, and the inoculation amount is 1% of the total material mass; after inoculation, the liquid is evenly distributed in the material by turning the pile, and then left to stand for 6 hours to allow the mycelium to initially colonize on the surface of the material. (3) Earthworm release: After inoculation with fungal agent, introduce adult Eisenia fetida earthworms at a release density of 800 earthworms / cubic meter; (4) Addition of inducing agent: After releasing earthworms, evenly sprinkle vanillin powder into the pile, with an addition amount of 0.2% of the total material mass. (5) Composting process management: The ambient temperature is controlled at 25±2℃, the moisture content is controlled at 60%±5%, the pile is turned over every 6 days, the composting process lasts for 35 days, and the compost is fully decomposed. Earthworms and impurities are removed to obtain high-quality organic fertilizer.

[0039] Example 2 A highly efficient composting method for degrading lignin, comprising the following steps: (1) Raw material pretreatment and mixing: Wheat straw is pre-crushed to a size of 1-2cm, and chicken manure is mixed with crushed wheat straw at a mass ratio of 3:1. The initial moisture content of the mixture is adjusted to 58% by spraying water. (2) Microbial inoculant inoculation: The brown rot fungus (Fomitopsis palustris) inoculant solution is evenly sprayed on the surface of the mixture, and the inoculation amount is 1.5% of the total material mass; after inoculation, the fungal solution is evenly distributed in the material by turning the pile, and then left to stand for 6 hours to allow the mycelium to initially colonize on the surface of the material. (3) Earthworm release: After inoculation with fungal agent, introduce adult Eisenia fetidae earthworms at a release density of 1500 earthworms / cubic meter; (4) Addition of inducing agent: After releasing earthworms, evenly sprinkle vanillin powder into the pile, with an addition amount of 0.3% of the total material mass. (5) Composting process management: The ambient temperature is controlled at 28±2℃, the moisture content is controlled at 62%±3%, the pile is turned over every 5 days, the composting process lasts for 30 days, and the compost is fully decomposed. Earthworms and impurities are removed to obtain high-quality organic fertilizer.

[0040] Example 3 A highly efficient composting method for degrading lignin, comprising the following steps: (1) Raw material pretreatment and mixing: Garden waste (leaves, branches) is pre-crushed to a size of 3-5cm, and pig manure is mixed with the crushed garden waste at a mass ratio of 5:1. The initial moisture content of the mixture is adjusted to 52% by spraying water. (2) Microbial inoculant inoculation: The mixed bacterial solution of white rot fungus and brown rot fungus (1:1) is evenly sprayed on the surface of the mixed material, and the inoculation amount is 0.8% of the total material mass; after inoculation, the bacterial solution is evenly distributed in the material by turning the pile, and then left to stand for 6 hours to allow the mycelium to initially colonize on the surface of the material. (3) Earthworm release: After inoculation with fungal agent, introduce adult Eisenia fetidae earthworms at a release density of 1200 earthworms / cubic meter; (4) Addition of inducing agent: After releasing earthworms, evenly sprinkle vanillin powder into the pile, with an addition amount of 0.1% of the total material mass. (5) Composting process management: The ambient temperature is controlled at 22±2℃, the moisture content is controlled at 58%±4%, the pile is turned over every 7 days, the composting process lasts for 40 days, and the compost is fully decomposed. Earthworms and impurities are removed to obtain high-quality organic fertilizer.

[0041] Comparative Example 1 The difference between this comparative example and Example 1 is that steps (3) and (4) are omitted, earthworms are not added and inducers are not added, and only inoculum is inoculated; the other conditions are the same as in Example 1.

[0042] Comparative Example 2 The difference between this comparative example and Example 1 is that step (4) is omitted, no inducing agent is added, and the other conditions are the same as in Example 1.

[0043] Comparative Example 3 The difference between this comparative example and Example 1 is that step (3) is omitted and earthworms are not introduced, while the other conditions are the same as in Example 1.

[0044] Comparative Example 4 The difference between this comparative example and Example 1 is that the timing of inoculation with the microbial agent is changed. The microbial agent is inoculated during the high-temperature period of composting (day 10), while the other conditions are the same as in Example 1.

[0045] Comparative Example 5 The difference between this comparative example and Example 1 is that the composting temperature is controlled at 35~40℃, while the other conditions are the same as in Example 1.

[0046] The compost final products obtained from each embodiment and comparative example were tested for various indicators. The test methods and test results are as follows.

[0047] Test metrics: 1. Determination of lignin degradation rate: The acid-washed lignin (ADL) method was used, with reference to the Van Soest fiber analysis method. The steps are as follows: (1) Take an air-dried compost sample, crush it, and sieve it (0.5 mm). (2) Treat the sample with an acidic detergent to remove proteins, minerals, etc.; (3) The remaining residue was hydrolyzed with 72% sulfuric acid, filtered, dried and weighed; (4) Calculate the lignin content and compare it with the initial content to obtain the degradation rate. Formula: Lignin degradation rate (%) = (initial lignin content - lignin content after decomposition) / initial lignin content × 100%.

[0048] 2. Lignosulfonamide (LiP) activity assay: Ultraviolet spectrophotometry was used. Substrate: resveratrol. The steps are as follows: (1) Use compost extract as enzyme solution; (2) Reaction system: enzyme solution + resveratrol + H2O2 in pH 3.0 buffer solution; (3) The generation rate of veratral was determined at a wavelength of 310 nm; 1 μmol of veratral generated per minute was defined as 1 enzyme activity unit (U).

[0049] 3. Manganese peroxidase (MnP) activity assay: Ultraviolet spectrophotometry was used. Substrate: MnSO4; the steps are as follows: (1) Use compost extract as enzyme solution; (2) Reaction system: enzyme solution + MnSO4 + H2O2 in pH 4.5 buffer solution; (3) Mn was measured at a wavelength of 238 nm. 3+ The formation rate of the complex; at a rate of 1 μmol Mn per minute. 3+ It is defined as 1 unit of enzyme activity (U).

[0050] 4. Humic acid content determination: The alkaline extraction-acid precipitation method was used, and the steps are as follows: (1) The compost samples were extracted with 0.1M NaOH solution; (2) Centrifuge and collect the supernatant, then adjust the pH to 1.0-2.0 to precipitate humic acid; (3) The precipitate was washed, dried and weighed; the result was expressed as the number of grams of humic acid contained in each kilogram of dry compost (g / kg).

[0051] 5. Determination of total nitrogen, phosphorus and potassium content: Total nitrogen: Kjeldahl method (GB / T 17767.1); Total phosphorus: Ammonium vanadate colorimetric method (GB / T 17767.3); Total potassium: Flame photometric method (GB / T 17767.4).

[0052] The test results of various indicators of the compost final products obtained from each embodiment and comparative example are shown in Table 1 below.

[0053] Table 1

[0054] Table 1 shows that the composting method provided by this invention significantly improves the degradation efficiency of lignin, enzyme activity, and degree of humification during composting through the synergistic effect of earthworms, lignin-degrading bacteria, and inducers, while also improving the nutrient content of the compost product. Experimental results indicate that key process parameters such as earthworm density, inoculation timing of the microbial agent, addition of the inducer, and temperature control have a significant impact on the composting effect.

[0055] In Comparative Example 1, since no earthworms or inducers were added, and composting was carried out solely using microbial agents, the results showed a significant decrease in lignin degradation rate, and enzyme activity and humic acid content were also significantly lower than in the Example group. This indicates that the physical turning action of earthworms and their gut microbiota played a crucial role in promoting the decomposition of organic matter during composting, while the presence of inducers further enhanced the activity of lignin-degrading bacteria. Comparative Example 2 showed that although the role of earthworms was retained, the lack of inducers reduced the lignin degradation rate to 52.6%. This result demonstrates that inducers have an irreplaceable function in activating and maintaining the activity of lignin-degrading bacteria, and their absence directly affects the decomposition efficiency of complex organic matter during composting. Data from Comparative Example 3 highlights the importance of earthworms; even with the addition of inducers, the lignin degradation rate was only 48.7% without earthworms. This further verifies that earthworms significantly improve composting efficiency by improving the compost structure, increasing aeration and water retention, and providing a more suitable environment for microbial activity. Comparative Example 4 investigated the effect of inoculation timing. Delaying inoculation to the high-temperature period of composting (day 10) resulted in a significant decrease in lignin degradation rate to 38.9%. This result indicates that early inoculation with lignin-degrading bacteria can fully utilize the suitable conditions in the early stages of composting, rapidly establish microbial dominance, and thus improve overall degradation efficiency. Comparative Example 5 increased the composting temperature to 35–40°C. The results showed that high temperatures significantly inhibited earthworm activity and the enzymatic hydrolysis of lignin-degrading bacteria. This suggests that temperature control during composting needs to comprehensively consider the optimal activity range of earthworms and microorganisms; excessively high or low temperatures are detrimental to improving composting efficiency.

[0056] In summary, the composting method provided by this invention achieves efficient and stable lignin degradation and high-quality organic fertilizer production through the synergistic optimization of multiple factors, and has significant practical application value.

[0057] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. 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 the present invention, are also included within the scope of the present invention.

Claims

1. A composting method for efficiently degrading lignin, characterized by, The method comprises the following steps: The lignin-degrading bacterial agent is added to the mixture of organic waste, and after turning over, the mixture is left to stand, then earthworms are put in, and after adding vanillin, composting is carried out, the environmental temperature is controlled to be 20-30 DEG C, the moisture content is controlled to be 55%-65%, the mixture is turned over regularly until complete composting, the earthworms and impurities are screened out, and the organic fertilizer is obtained.

2. The method of claim 1, wherein the lignin-degrading composting method is characterized by, The mixture of organic waste is obtained by mixing organic waste and adjusting the moisture content; the moisture content of the mixture of organic waste is 50%-60%.

3. The method of claim 1, wherein the lignin-degrading composting method is characterized by, The organic waste comprises livestock and poultry manure, crushed crop straw and / or crushed garden waste.

4. The method of claim 3, wherein the lignin-degrading composting method is characterized by, The size of the crushed crop straw is 1-5 cm; the size of the crushed garden waste is 1-5 cm.

5. The method of claim 1, wherein the lignin-degrading composting method is characterized by, The inoculation amount of the lignin-degrading bacterial agent is 0.5%-2% of the mass of the mixture.

6. The method of claim 5, wherein the lignin-degrading composting method is characterized by, The lignin-degrading bacterial agent comprises at least one of white rot fungus and brown rot fungus.

7. The method of claim 5, wherein the lignin-degrading composting method is characterized by, The effective viable cell number of the lignin-degrading microbial agent is 1.0×10 8 ~1.0×10 10 cfu·g -1 .

8. The method of claim 1, wherein the lignin-degrading composting method is characterized by, The density of the earthworms is 500-2000 per cubic meter.

9. The method of claim 1, wherein the lignin-degrading composting method is characterized by, The addition amount of vanillin is 0.1%-0.5% of the mass of the mixture.

10. The method of claim 1, wherein the lignin-degrading composting method is characterized by, The regular turning over is specifically carried out once every 5-7 days.

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