Compost and preparation method and application thereof

Abstract

The present invention belongs to the technical field of organic fertilizers, and relates to a compost and a preparation method and application thereof. The technical problem that the pH value of the biogas slurry biocoagulation filter cake in the prior art is relatively high, which affects the composting efficiency. The present application provides a composting preparation method, comprising the following steps: crushing the biogas slurry biocoagulation filter cake into particles, mixing them evenly with the screw-pressed biogas residue, wherein the dry matter weight ratio of the biogas slurry biocoagulation filter cake to the screw-pressed biogas residue is 1.5-2.5:1, and the water content is adjusted to 55%-65%; obtaining a reactant; and aerobic fermentation of the reactant to obtain the compost. The method mixes the biogas slurry biocoagulation filter cake with the screw-pressed biogas residue for composting, thereby reducing the pH value of the cake and increasing the composting efficiency. The present application also provides the compost obtained by the method, which enables the seed germination index to reach more than 100%. At the same time, the present application also provides the application of the compost in promoting plant growth and the application of the composting preparation method in treating organic waste.

Description

Technical Field

[0001] The invention belongs to the technical field of organic fertilizer preparation, and in particular relates to compost and a preparation method and application thereof. Background Art

[0002] Using mud cake for composting has significant benefits in terms of the environment, agriculture, economy and society: (1) Reducing greenhouse gas emissions: Traditional landfill or incineration will produce a large amount of greenhouse gases (such as methane and carbon dioxide), while during the composting process, organic matter decomposes under aerobic conditions, producing less greenhouse gases, which helps to mitigate climate change; (2) Providing organic fertilizer: Mud cake compost is a high-quality organic fertilizer that can provide crops with the necessary nutrients, such as nitrogen, phosphorus, potassium, etc., promote crop growth, and increase crop yield and quality; (3) Reducing processing costs: Compared with traditional landfill or incineration, the processing cost of mud cake composting is relatively low, which can save a lot of processing costs for enterprises or cities; (4) Improving resource utilization efficiency: Converting mud cake into organic fertilizer realizes the resource utilization of waste, improves resource utilization efficiency, and conforms to the concept of sustainable development.

[0003] The mud cake in the existing mud cake composting technology is mostly sourced from sewage sludge cake. For example, the Chinese invention patent publication number is CN103373797A, the invention name is "A method for efficient aerobic composting of sewage sludge", and the application date is April 19, 2012. The following operating steps are disclosed: sludge is dehydrated by using a diaphragm sludge filter press, the moisture content of the mud cake is less than 60%, the mud cake is crushed and heated, and then fully mixed with the fermentation composite strain, and directly composted and fermented without adding any organic dry materials and remixed materials. This scheme is direct composting, and the fermentation composite strain needs to be added, which has high requirements on the properties of the initial mud cake.

[0004] Another example is the Chinese invention patent publication number CN109053272A, the invention name is "a kind of papermaking sludge compost", the application date is June 13, 2017, and the raw materials used in the disclosure include, by weight ratio: 75% to 77% of dry papermaking sludge, 15% to 17% of plant straw, 6% of cottonseed cake, 1% of organic fertilizer fermentation agent, and 1% of fungicide. The following operating steps are disclosed: (1) feeding the formulated amount of dry papermaking sludge, plant straw, and cottonseed cake into a crusher, and feeding them into a fermentation tank after crushing; (2) feeding the formulated amount of organic fertilizer fermentation agent into the fermentation tank, adding an appropriate amount of water to mix evenly, and then sealing and fermenting, fermenting for 18 to 20 days in summer and 25 to 30 days in winter, the fermentation temperature can reach 45°C to 55°C, and after the fermentation is completed, the tank is opened and the fermented material is fed into a post-processing tank; (3) adding the formulated amount of fungicide into the post-processing tank, mixing evenly, and then drying the material in the open air to obtain the finished papermaking sludge compost. In this scheme, the mud cake comes from papermaking sludge. The high water content of papermaking sludge leads to poor rheological properties and poor fermentation effect, and the plant straw in the raw material is not easily fermented and degraded.

[0005] Biogas slurry bioflocculation filter cake is a product of biogas slurry purification. Specifically, it is the biogas produced by anaerobic fermentation of food waste to produce biogas. It is conditioned by the method of bioflocculation and then passed through a filter press to separate the solid and liquid to produce a cake-like solid substance. As a product of emerging and practical biogas slurry purification technology, the treatment and disposal method of the cake needs to be solved urgently. The above composting scheme is not suitable for biogas slurry bioflocculation filter cake: adding fermentation composite bacteria increases the cost; and plant straw or cottonseed cake as raw materials is not easy to degrade, and the resulting compost is not suitable for promoting plant growth. Traditional landfilling greatly reduces the recycling rate of effective resources. Now, given its considerable organic matter and nitrogen content, and its water content is much lower than that of sludge cake treated by physical and chemical treatment, aerobic composting of biogas slurry bioleaching cake is an ideal disposal method, but its high pH value affects the composting efficiency. Therefore, a new composting method is needed to improve the efficiency and quality of aerobic composting. Summary of the invention

[0006] 1. Problems to be solved

[0007] Aiming at the technical problem that the pH value of biogas slurry biocoagulation filter cake is high in the prior art, which is not suitable for the growth of aerobic microorganisms and affects the composting effect, the present application provides a method for preparing compost, wherein biogas slurry biocoagulation filter cake is mixed with screw-pressed biogas residue for composting, thereby providing an environment suitable for the growth of aerobic microorganisms. The present application also provides a compost and its application.

[0008] 2. Technical solution

[0009] In order to achieve the above purpose, the technical solution provided is:

[0010] A method for preparing compost comprises the following steps:

[0011] The biogas slurry bio-coagulation filter cake is crushed into particles, and mixed evenly with the screw-pressed biogas residue, wherein the dry matter weight ratio of the biogas slurry bio-coagulation filter cake to the screw-pressed biogas residue is 1.5-2.5:1, and the water content is adjusted to 55%-65%, to obtain a reactant;

[0012] The reactants are subjected to aerobic fermentation to obtain the compost.

[0013] Preferably, the pH of the reactant is 9.0-10.0.

[0014] If the moisture content is too low, it is not conducive to the growth of microorganisms and is not enough for microorganisms to use. If the moisture content is too high, the voids in the pile will be reduced, which will easily lead to anaerobic growth and be unfavorable for the growth of aerobic bacteria. Adjusting the moisture content to 55% to 65% is more suitable for microbial growth.

[0015] The pH of biological flocculation filter cake is 10.0-11.5. It is difficult to compost it alone because the high pH is not suitable for microbial growth. It needs to be adjusted by adding screw-pressed sludge. Screw-pressed sludge is a raw material that is easy to compost with a pH of 8.0-9.5. However, in actual project operation, the amount of screw-pressed sludge produced is not as much as that of biological flocculation filter cake. Therefore, when the dry matter weight ratio of mud cake to sludge is 1.5-2.5:1, the pH of the reactant is 9.0-10.0, which meets the composting conditions. That is, adding less sludge can increase the composting efficiency.

[0016] Furthermore, the particle size of the biogas slurry biocoagulation filter cake is ≤10 mm, and the water content is 50% to 60%.

[0017] Furthermore, the particle size of the screw-pressed biogas residue is ≤10 mm, and the moisture content is 45% to 55%.

[0018] Furthermore, during the aerobic composting process, a heat insulating material is used to cover the reactants.

[0019] Furthermore, the heat insulating material is a thermal insulation film or straw.

[0020] Furthermore, the aerobic composting fermentation process undergoes natural heating and / or cooling; the temperature reached by the natural heating is 60°C to 80°C.

[0021] Furthermore, during the aerobic composting fermentation process, the pile is turned every 2 to 4 days in the first 3 weeks and once a week in the next 3 to 7 weeks.

[0022] Temperature rise is a natural process, because the microbial activity intensifies, the pile environment and nutrients can promote the metabolism of microorganisms, and this process generates heat. In order to better allow the pile to contact with air, it is necessary to turn the pile regularly. Turning the pile will release the heat inside the pile, and the temperature will drop. Finally, the microbial metabolism ends and the temperature drops to room temperature.

[0023] Preferably, the moisture content is added to 55% to 65% during the compost turning.

[0024] Preferably, the aerobic fermentation time is 6 to 10 weeks.

[0025] Preferably, during the composting process, samples are taken regularly to determine the seed germination index.

[0026] The Germination Index (GI) is an authoritative indicator for evaluating the maturity of compost. By measuring the GI, it can be determined whether the compost has reached a maturity suitable for plant growth. At the same time, the Germination Index is widely used to evaluate the phytotoxicity of compost products. Unripe compost products will inhibit plant growth and deteriorate soil conditions, and the Germination Index provides a reliable method to evaluate the phytotoxicity of compost. Therefore, regular sampling and determination of the Germination Index during the composting process can better evaluate the maturity of the compost and ensure the safety of the compost products.

[0027] A compost is prepared by the method.

[0028] The organic matter and nutrient (N / P / K) contents of the obtained compost products were determined.

[0029] An application of compost, and the application of the compost in promoting plant growth.

[0030] The invention discloses an application of a compost preparation method, and an application of the method in treating organic waste.

[0031] 3. Beneficial effects

[0032] Compared with the existing known technology, the technical solution provided by the present invention has the following beneficial effects:

[0033] (1) A compost preparation method of the present invention comprises crushing the biogas slurry biocoagulation filter cake into particles, uniformly mixing the particles with screw-pressed biogas residue, wherein the dry matter weight ratio of the biogas slurry biocoagulation filter cake to the screw-pressed biogas residue is 1.5-2.5:1, and adjusting the water content to 55%-65% to obtain a reactant. Since the pH value of the biogas slurry biocoagulation filter cake is relatively high and affects the composting efficiency, the pH value is reduced to 9.0-10.0 (the initial pH value during the composting process) after mixing with the screw-pressed biogas residue, and the water content is 55%-65%, which is more suitable for microbial growth; aerobic composting fermentation is performed on the reactant to obtain the compost, wherein the reactant starts to heat up on the second day, the composting starts quickly, the microbial activity is active, and the composting efficiency is high. The biogas slurry biocoagulation filter cake is a product of biogas slurry purification technology. The composting method can efficiently recover available resources and realize the reduction, harmlessness and resource utilization of solid waste. The preparation method has a simple process flow and is easy to operate.

[0034] (2) A compost of the present invention, the compost product formed after the composting is completed, the seed germination index reaches more than 100%, the compost product is completely decomposed and harmless, the organic matter in the compost product is 30.6%, and the nutrients (N / P / K) account for 4.2% of the dry matter, reaching the minimum limit of the technical index of organic fertilizer 4% (NY / T 525-2021).

[0035] (3) The application of a compost of the present invention, the application of compost products in promoting plant growth, the compost product is a high-quality organic fertilizer, which can provide the necessary nutrients for crops, such as nitrogen, phosphorus, potassium, etc., to promote crop growth; the organic matter in the compost can increase the porosity of the soil, improve the aeration and drainage of the soil, and contribute to the healthy development of the root system. At the same time, it can serve as a food source for soil microorganisms, increase the number and activity of microorganisms, and promote the health of the soil ecosystem. Plants using compost tend to grow more vigorously, have higher yields, and better quality because they can obtain more comprehensive and balanced nutrition.

[0036] (4) Application of a compost preparation method of the present invention, application of the compost preparation method in treating organic waste, the method can convert solid organic waste (such as bioflocculation filter cake, screw-pressed biogas residue, livestock and poultry manure, edible fungus production waste and crop straw, etc.) into stable organic matter and carbon-rich resources. These resources can be used as soil remediation agents or fertilizers, and can also be made into cultivation substrates or soil covers, thereby realizing the resource utilization of waste, improving resource utilization efficiency, and complying with the concept of sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a process flow chart of the present invention;

[0038] Figure 2This is the curve of the temperature of the compost with different moisture contents over time during the composting process;

[0039] Figure 3 The pictures are of bioflocculation filter cake (a) and screw-pressed digestate (b);

[0040] Figure 4 This is the relationship between the pH value of the compost and time during the composting process.

[0041] Figure 5 It is the change of seed germination index during composting process;

[0042] Figure 6 The changes in plant height of ryegrass under different amounts of compost application and pictures of ryegrass after planting;

[0043] Figure 7 This is the curve of temperature change over time during the composting process of Comparative Example 1;

[0044] Figure 8 This is the temperature change curve over time during the composting process of Comparative Example 2. DETAILED DESCRIPTION

[0045] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with embodiments.

[0046] The screw-pressed biogas residue of the present application is derived from the solid residue (such as Figure 3 b), mainly composed of suspended particles in anaerobic digestion liquid, the separated liquid part is the food waste biogas slurry that needs further treatment, and the solid formed after biological coagulation conditioning and solid-liquid separation by filter press is the biological coagulation filter cake (such as Figure 3 a).

[0047] The basic physical and chemical properties of bioflocculation filter cake and screw press residue are shown in Table 1:

[0048] Table 1 Basic physical and chemical properties of bioflocculation filter cake and screw press residue

[0049]

[0050] Example 1

[0051] A method for preparing compost in this embodiment comprises the following steps:

[0052] S1. 831 kg of biogas slurry biocoagulation filter cake is crushed into small particles with a particle size of ≤10 mm and a moisture content of 55% to 60%, and mixed with 532 kg of screw-pressed biogas residue with a particle size of ≤10 mm and a moisture content of 50% to 55%, and the water content is adjusted to 65% to obtain a reactant;

[0053] S2. The reactants are piled into a pile-like body, covered with a heat-insulating film for aerobic fermentation reaction. The pile is turned over every 2 to 4 days in the first three weeks, and an appropriate amount of water is added. The pile is turned over once a week in the next seven weeks. After 70 days of reaction, mature organic fertilizer, i.e., compost product, is obtained.

[0054] Determine the temperature change over time during the composting reaction. The results are as follows Figure 2 shown.

[0055] Example 2

[0056] A method for preparing compost in this embodiment comprises the following steps:

[0057] S1. 831 kg of biogas slurry biocoagulation filter cake is crushed into small particles with a particle size of ≤10 mm and a moisture content of 50% to 55%, and mixed with 532 kg of screw-pressed biogas residue with a particle size of ≤10 mm and a moisture content of 45% to 50%, and the water content is adjusted to 55% to obtain a product to be reacted;

[0058] S2. The reactants are piled into a pile-like body, covered with a heat-insulating film for aerobic fermentation reaction. The pile is turned over every 2 to 4 days in the first three weeks, and an appropriate amount of water is added. The pile is turned over once a week in the next seven weeks. After 70 days of reaction, mature organic fertilizer, i.e., compost product, is obtained.

[0059] Determine the temperature change over time during the composting reaction. The results are as follows Figure 2 shown.

[0060] Example 3

[0061] A method for preparing compost in this embodiment comprises the following steps:

[0062] S1. 831 kg of biogas slurry biocoagulation filter cake was crushed into small particles with a particle size of ≤10 mm and a moisture content of 52.11%, and 532 kg of screw-pressed biogas residue with a particle size of ≤10 mm and a moisture content of 49.33% were fully mixed, and the water content was adjusted to 60% to obtain a product to be reacted;

[0063] S2. The reactants are piled into a pile-like body, covered with a heat-insulating film for aerobic fermentation reaction. The pile is turned over every 2 to 4 days in the first three weeks, and an appropriate amount of water is added. The pile is turned over once a week in the next seven weeks. After 70 days of reaction, mature organic fertilizer, i.e., compost product, is obtained.

[0064] The process flow chart of this application is as follows Figure 1 shown.

[0065] The pH of the compost pile changes with time during the composting process. Figure 4 shown.

[0066] pH value is one of the important factors that affect the life activities and metabolism of microorganisms. An inappropriate pH value will inhibit the activity of microorganisms in the pile, thus affecting the composting process. The addition of screw-pressed biogas residue can adjust the initial pH of the pile, because the pH value of screw-pressed biogas residue is 9.26, which is lower than the pH value of biogas slurry bioflocculant filter cake 10.95. The pH of the reactant after the two are mixed is 9.61, that is, the initial pH during the composting process is 9.61, which drops to about 8.0 after one week and is basically stable. The pH at the end of composting is 7.52. This pH is suitable for microbial activity and metabolism.

[0067] The temperature changes over time during the composting process were measured. Figure 2 shown.

[0068] In Example 1-3, when the moisture content of the compost was 65%, 55% and 60% respectively, the temperature of the compost (i.e., the compost temperature) and the ambient temperature changed with time. Since temperature is the best parameter for judging the strength of microbial activity, the compost temperature will increase as the microbial activity intensifies. Figure 2 It can be seen that when the ambient temperature is between 10℃ and 35℃, the pile will naturally heat up to 60℃ to 80℃, indicating that the microbial activity is intensified, and the pile environment and nutrients can promote the metabolism of microorganisms, which generates heat in this process. In order to better allow the pile to contact the air, it is necessary to turn the pile regularly. Turning the pile will release heat and reduce the temperature. After 50 days of aerobic composting, the microbial activity weakens and the temperature drops to about 50 degrees Celsius. Finally, the microbial reaction is complete and the pile temperature naturally drops to room temperature.

[0069] In this embodiment, the organic matter content of the biocoagulation filter cake and the screw-pressed sludge were 18.44% and 75.71% respectively, the TN content was 1.36% and 1.71% respectively, and the TP content was 0.12% and 0.15% respectively. After the composting was completed, the organic matter of the compost product was measured to be 30.6%, and the nutrients (N / P / K) accounted for 4.2% of the dry matter, reaching the minimum limit of the technical indicator of organic fertilizer 4% (NY / T 525-2021).

[0070] Example 4

[0071] A method for preparing compost in this embodiment, in which the seed germination index is determined during the composting process of Example 3, comprises the following steps:

[0072] The compost sample was mixed with pure water at a mass ratio of 1:10 for extraction, shaken at 180 rpm for 1 h, and the supernatant after centrifugation was filtered through a 0.45 μm filter membrane to obtain the fertilizer filtrate.

[0073] 5 mL of fertilizer filtrate was taken into a culture dish covered with filter paper, and 20 cabbage seeds were evenly placed. The seeds were cultured in the dark at 25 °C for 48 h, and the seed germination rate and root length were measured. Pure water was used as the control group.

[0074] Seed germination index (GI) = (germination rate of seeds treated with compost filtrate × average root length of treated seeds) / (germination rate of seeds treated with pure water × average root length of seeds treated with pure water) × 100%.

[0075] Regular sampling and determination of seed germination index during the composting process can better assess the maturity of the compost and ensure the safety of the compost product. Figure 5 It can be seen that the seed germination index shows a trend of first decreasing and then increasing. In the early stage of composting, organic matter is decomposed, and short-chain organic acids with biological toxicity accumulate in the compost, which is harmful to seed growth. In the subsequent process, short-chain organic acids are successively decomposed, and the toxicity gradually decreases, causing the seed germination index to begin to rise. After the composting is completed, the fertilizer seed germination index reaches more than 100%, indicating that it is completely decomposed and harmless.

[0076] Example 5

[0077] A composting method of this embodiment, in which the composting product obtained in Example 3 is subjected to a potting experiment, comprises the following steps:

[0078] The potting medium is 5 kg of garden soil, to which 1%, 3%, 5% and 10% of compost products (obtained by the composting method in Example 1) are added respectively by mass ratio and mixed evenly. 5 kg of garden soil alone is used as a control, and the planted crop is ryegrass.

[0079] The plant height of ryegrass at 0d, 10d, 20d, 30d, 80d and 110d was measured under different compost application rates.

[0080] Use pot experiments to verify the fertilization effect of compost products, such as Figure 6 As shown in the figure, the plant height of ryegrass planted after applying 1% to 10% compost is higher than that of ryegrass planted without compost, but the plant height of ryegrass planted after applying 5% and 10% compost is lower than 1% and 3%, indicating that the more compost is applied, the better. For normal soil, the optimal application amount is 3%.

[0081] The compost of this embodiment can increase the organic matter in the soil, improve the soil structure, increase the aeration and water retention of the soil, and promote the development of healthy and strong roots of plants, which is very important for plant growth.

[0082] Comparative Example 1

[0083] This comparative example provides a method for preparing compost, and the specific steps are as follows:

[0084] 100 kg of biogas slurry biocoagulation filter cake is crushed into blocks with a particle size of 50 mm to 100 mm, mixed with 70 kg of screw-pressed biogas residue with a particle size of ≤10 mm, and the water content is adjusted to 60% to obtain a reactant;

[0085] The reactants are piled into a pile-like body, covered with a heat-insulating film for aerobic fermentation reaction, and the daily temperature changes are recorded.

[0086] like Figure 7 As shown, the temperature slowly increased to 43.6℃ in the first three days, and then gradually dropped to the ambient temperature with no sign of further increase, indicating that mud cake with larger particle size is difficult to be utilized by microorganisms, because mud cake with larger particle size is difficult to fully mix with sludge with smaller particle size, thus making it difficult to improve the overall physical and chemical properties of the pile.

[0087] Comparative Example 2

[0088] This comparative example provides a method for composting biogas slurry biocoagulation filter press mud cake separately, and the specific steps are as follows:

[0089] 500 kg of biogas slurry biocoagulation filter cake was crushed into small particles with a particle size of ≤ 10 mm, and the water content was adjusted to 60% to obtain a product to be reacted;

[0090] The reactants are piled into a pile-like body, covered with a heat-insulating film for aerobic fermentation reaction, and the daily temperature changes are recorded.

[0091] like Figure 8 As shown, the temperature of the pile could not rise spontaneously within 10 days and was the same as the ambient temperature, indicating that the biogas slurry bioflocculant filter cake alone could not be composted because the pH of the cake was high and could not provide an environment conducive to microbial metabolism.

[0092] In summary, the present application provides a method for preparing compost, which mixes the biogas slurry bioflocculant filter cake with the screw-pressed biogas residue to improve the overall physical and chemical properties of the compost and increase the composting efficiency. The nutrient (N / P / K) and organic matter content of the obtained compost product meet the requirements and can be used to promote crop growth. The compost preparation method can be applied to the treatment of organic waste.

[0093] The above-mentioned embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person skilled in the art, several modifications, improvements and substitutions can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the attached claims.

Claims

1. A method for preparing compost, characterized in that: The following steps are involved: The biogas slurry bio-coagulation filter cake is crushed into particles, and mixed evenly with the screw-pressed biogas residue, wherein the dry matter weight ratio of the biogas slurry bio-coagulation filter cake to the screw-pressed biogas residue is 1.5-2.5:1, and the water content is adjusted to 55%-65% to obtain a reactant; The reactants are subjected to aerobic composting fermentation to obtain the compost.

2. The method for preparing compost according to claim 1, characterized in that: The particle size of the biogas slurry bio-coagulation filter cake is ≤10mm, and the water content is 50% to 60%.

3. The method for preparing compost according to claim 1, characterized in that: The particle size of the screw-pressed biogas residue is ≤10 mm, and the moisture content is 45% to 55%.

4. A method for preparing compost according to any one of claims 1 to 3, characterized in that: During the aerobic composting process, a heat insulating material is used to cover the reactants.

5. The method for preparing compost according to claim 4, characterized in that: The heat insulating material is a heat insulating film or straw.

6. The method for preparing compost according to claim 5, characterized in that: The aerobic composting fermentation process undergoes natural heating and / or cooling; the temperature reached by the natural heating is 60°C to 80°C.

7. The method for preparing compost according to claim 6, characterized in that: During the aerobic composting fermentation process, the pile is turned every 2 to 4 days in the first 3 weeks and once a week in the next 3 to 7 weeks.

8. A compost, characterized in that: The method is prepared by any one of claims 1 to 7.

9. An application of composting, characterized in that: Use of the compost as claimed in claim 8 in promoting plant growth.

10. Application of a compost preparation method, characterized in that: Use of the method according to any one of claims 1 to 7 in treating organic waste.

Images