A method for increasing humic acid content in compost through stage treatment

Abstract

The present invention provides a method for increasing the humic acid content of compost through staged treatment, which belongs to the technical field of solid organic waste treatment and resource utilization. The present invention pre-hydrolyzes the organic solid waste to be treated to destroy the cellulose crystal connection structure in the organic solid waste to be treated. The present invention adds a high-efficiency cellulose hydrolyzing bacteria agent before composting to promote the hydrolysis of organic components, stops ventilation while adding functional materials during the high-temperature period of composting, promotes the rapid condensation of humic acid precursor compounds to form humic acid, and provides a substrate for the formation of humic acid; after ventilation is restored, the functional materials stimulate enzyme activity, further accelerating the oxidative polymerization of humic acid precursors. During the compost cooling period, minerals and metal ion oxides are added to the pile to protect the formed humic acid molecules from being further hydrolyzed by microorganisms.

Description

Technical Field

[0001] The invention relates to the technical field of solid organic waste treatment and resource utilization, and in particular to a method for increasing the humic acid content of compost through staged treatment. Background Art

[0002] Large amounts of carelessly discarded organic solid waste are damaging soil fertility. Harmful byproducts such as leachate and odor can contribute to water eutrophication, air pollution, and even threaten human health. Composting, as a fast and safe way to recycle organic waste, is gaining increasing attention. Furthermore, humic acid, the most important byproduct of the composting process, has a certain remedial effect on environmental pollution, improving soil fertility, promoting crop growth, and absorbing heavy metals and organic dyes. Therefore, in the face of large amounts of organic waste, increasing humic acid production during the composting process may be the best way to achieve resource recycling.

[0003] Humic acid formation results from the polymerization or condensation of small-molecule humic acid precursor compounds, such as polyphenols, reducing sugars, and amino acids, produced during the decomposition of organic matter and microbial synthesis. However, the composition of current organic solid waste is complex, with a diverse ratio of readily bioavailable and poorly hydrolyzed organic components. This leads to asynchrony in the hydrolysis of organic components during the composting of various types of organic solid waste. This imbalance in microbial component utilization further reduces the efficiency of humic acid precursor formation in the compost. Furthermore, humic acid precursor compounds serve as an energy source for microbial activity and are easily mineralized into carbon dioxide. Therefore, the substrate competition between humus formation and microbial activity inevitably affects the efficiency of humus formation, leading to a decrease in the quality of humic acid production and, consequently, compost quality. Summary of the Invention

[0004] The object of the present invention is to provide a method for increasing the humic acid content of compost through staged treatment. The method of the present invention can effectively increase the humic acid yield of organic solid waste compost.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for increasing the humic acid content of compost by staged treatment, comprising the following steps:

[0007] 1) soaking the organic solid waste to be treated in a hydrolysis solution to perform pre-hydrolysis to obtain a pre-hydrolysis product; the hydrolysis solution includes a Fenton reagent or a nitric acid aqueous solution;

[0008] 2) adjusting the C / N ratio of the pre-hydrolyzed product to (25-30): 1. the water content is 60%-70%, the pH is 7.0-7.5, and inoculating a high-efficiency lignocellulose hydrolyzing agent to obtain a compostable material;

[0009] 3) piling the compost material to perform a first composting process until the temperature at the center of the compost body reaches 50-65° C., thereby obtaining a first compost; wherein the ventilation rate of the first compost is 0.05-0.15 L / min;

[0010] 4) mixing the first pile material and the first functional material, and performing a second composting process until the temperature at the center of the pile body reaches 43-48° C., thereby obtaining a second pile material;

[0011] The second composting procedure includes: from 0 to 24 hours, the ventilation rate is 0; after 24 hours, the ventilation rate is 0.05 to 0.15 L / min;

[0012] The first functional material includes metal oxides and / or organic matter containing humic acid precursors;

[0013] 5) mixing the second pile material and the second functional material, and performing a third composting process until the pile body temperature reaches 33-35° C., thereby obtaining a compost product;

[0014] The second functional material is selected from one of minerals, biochar and metal oxides.

[0015] Preferably, the concentration of the nitric acid aqueous solution in step 1) is 7.5-8.5 mol / L; the volume of the nitric acid aqueous solution and the mass of the organic solid waste to be treated are of the same order of magnitude, and the ratio is 10:(0.5-1.5).

[0016] Preferably, the Fenton reagent in step 1) is prepared by dissolving ferrous chloride in a 30% by volume aqueous hydrogen peroxide solution as a solvent; the volume molar concentration ratio of the ferrous chloride to hydrogen peroxide is (0.01-0.03):1.5; and the mass ratio of the Fenton reagent to the organic solid waste to be treated is (1-3):(0.5-3).

[0017] Preferably, in step 1), when the hydrolysis solution is an aqueous nitric acid solution, the pre-hydrolysis temperature is 20 to 30° C.; and the pre-hydrolysis time is 10 to 14 hours.

[0018] Preferably, in step 1), when the hydrolysis solution is Fenton's reagent, the pre-hydrolysis temperature is 20-30° C.; and the hydrolysis time is 1.5-2.5 h.

[0019] Preferably, the efficient lignocellulose hydrolyzing bacteria agent in step 4) comprises Bacteroides thetaiotaomicron, Lachnospiraceae and Clostridium; the ratio of the effective viable bacteria counts of Bacteroides thetaiotaomicron, Lachnospiraceae and Clostridium is 3:(0.5-1.5):(0.5-1.5); the total effective viable bacteria count of the efficient lignocellulose hydrolyzing bacteria agent is 1×10 7~1×10 9 CFU / mL; the ratio of the volume of the high-efficiency lignocellulose hydrolyzing agent to the mass of the first pile is (500-1000) μL: (1-1.5) kg.

[0020] Preferably, the organic matter containing humic acid precursors in step 4) is selected from one or more of reducing sugars, amino acids, chicken manure and biochar; the added amount of the organic matter containing humic acid precursors is 20‰ to 25‰ of the dry weight of the first pile.

[0021] Preferably, the metal oxide in step 4) is selected from one of iron oxide, manganese dioxide and copper oxide; the added amount of the metal oxide is 2‰ to 8‰ of the dry weight of the first pile.

[0022] Preferably, the amount of the mineral or biochar added in step 5) is independently 7% to 8% of the dry weight of the second pile; the mineral comprises montmorillonite and / or illite.

[0023] Preferably, the metal oxide in step 5) is selected from one of iron oxide, manganese dioxide and copper oxide; the added amount of the metal oxide is 2‰ to 8‰ of the dry weight of the second pile.

[0024] Beneficial effects of the present invention: The present invention provides a method for increasing the humic acid content of compost through staged treatment. The present invention utilizes abiotic-biotic coupling to promote the synchronous hydrolysis of refractory lignocellulose and easily degradable organic components. The present invention first uses Fenton's reagent or aqueous nitric acid solution to pre-hydrolyze the organic solid waste to be treated, thereby destroying the crystalline connection structure of lignocellulose in the organic solid waste to be treated and reducing the subsequent microbial hydrolysis pressure. The present invention adds a high-efficiency lignocellulose hydrolyzing agent before composting to promote the hydrolysis of organic components. During the high-temperature period of composting, functional materials are added and ventilation is stopped to create an anaerobic environment for the compost. The functional materials act as chemical catalysts, promoting the microbial synthesis and metabolism of humic acid precursor compounds under anaerobic conditions, providing substrates for humic acid formation. At the same time, anaerobic conditions enable the functional materials to maximize their chemical catalyst properties, reduce the oxidation of organic components, promote the rapid condensation of humic acid precursor compounds to form humic acid, and provide substrates for humic acid formation. After ventilation is restored, the functional materials stimulate enzyme activity and can continue to function, thus acting as biological enzyme activity activators to stimulate the activity of enzymes related to organic matter conversion, further accelerating the oxidative polymerization of humic acid precursors. During the composting cooling period, i.e., the period when humic acid is formed in large quantities, minerals or metal ion oxides are added to the compost to protect the formed humic acid molecules from further hydrolysis by microorganisms. The method of the present invention can promote the formation of humic acid while reducing the further utilization of humic acid, thereby achieving the directional humification of organic components to the greatest extent and realizing the efficient resource utilization of organic solid waste. The test results show that when the method of the present invention is used to compost organic solid waste, after 60 days of composting experiment, the degradation efficiency of lignocellulose in rice straw is increased by 30%, and the humic acid content is increased by 50%. The microorganisms effectively exert their hydrolysis, transformation and synthesis effects on organic solid waste, driving the organic components to form humic acid in a directional manner. DETAILED DESCRIPTION

[0025] The present invention provides a method for increasing the humic acid content of compost by staged treatment, comprising the following steps:

[0026] 1) soaking the organic solid waste to be treated in a hydrolysis solution to perform pre-hydrolysis to obtain a pre-hydrolysis product; the hydrolysis solution includes a Fenton reagent or a nitric acid aqueous solution;

[0027] 2) adjusting the C / N ratio of the pre-hydrolyzed product to (25-30): 1. the water content is 60%-70%, the pH is 7.0-7.5, and inoculating a high-efficiency lignocellulose hydrolyzing agent to obtain a compostable material;

[0028] 3) piling the compost material to perform a first composting process until the temperature at the center of the compost body reaches 50-65° C., thereby obtaining a first compost; wherein the ventilation rate of the first compost is 0.05-0.15 L / min;

[0029] 4) mixing the first pile material and the first functional material, and performing a second composting process until the temperature at the center of the pile body reaches 43-48° C., thereby obtaining a second pile material;

[0030] The second composting procedure includes: from 0 to 24 hours, the ventilation rate is 0; after 24 hours, the ventilation rate is 0.05 to 0.15 L / min;

[0031] The first functional material includes metal oxides and / or organic matter containing humic acid precursors;

[0032] 5) mixing the second pile material and the second functional material, and performing a third composting process until the pile body temperature reaches 33-35° C., thereby obtaining a compost product;

[0033] The second functional material is selected from one of minerals, biochar and metal oxides.

[0034] The present invention first soaks the organic solid waste to be treated in a hydrolysis solution to perform pre-hydrolysis to obtain a pre-hydrolysis product; the hydrolysis solution includes a Fenton reagent or a nitric acid aqueous solution.

[0035] In the present invention, the organic solid waste preferably includes crop straw and garden organic solid waste; the crop straw preferably includes one or more of corn straw, rice straw and soybean straw.

[0036] In the present invention, the organic solid waste is preferably pulverized, and the length of the pulverized organic waste is preferably 2 to 3 cm.

[0037] In the present invention, the concentration of the nitric acid aqueous solution is preferably 7.5-8.5 M, more preferably 8 M; the ratio of the nitric acid aqueous solution to the organic solid waste to be treated is preferably 10 mL: (0.5-1.5) g, more preferably 10 mL: 1 g.

[0038] In the present invention, the Fenton reagent is preferably prepared by dissolving ferrous chloride in a 30% by volume aqueous hydrogen peroxide solution as a solvent; the volume molar concentration ratio of the ferrous chloride to hydrogen peroxide is preferably (0.01-0.03):1.5, more preferably 0.02:1.5; the mass ratio of the Fenton reagent to the organic solid waste to be treated is (1-3):(0.5-3), more preferably 2:(1-2).

[0039] In the present invention, when the hydrolysis solution is a nitric acid aqueous solution, the pre-hydrolysis temperature is preferably 20-30° C., more preferably 25° C.; the pre-hydrolysis time is preferably 10-14 h, more preferably 12 h.

[0040] In the present invention, when the hydrolysis solution is Fenton's reagent, the pre-hydrolysis temperature is preferably 20-30° C., more preferably 25° C.; the hydrolysis time is preferably 1.5-2.5 h, more preferably 2 h.

[0041] After obtaining the pre-hydrolyzed product, the present invention adjusts the C / N ratio of the pre-hydrolyzed product to (25-30): 1, the water content to 60%-70%, the pH to 7.0-7.5, inoculates a high-efficiency lignocellulose hydrolyzing agent, and obtains the material to be composted.

[0042] In the present invention, the C / N ratio of the composted material is preferably 28:1; the moisture content of the composted material is preferably 65%; and the pH of the composted material is preferably 7.2. In the specific implementation of the present invention, the material used to adjust the C / N ratio of the pre-hydrolyzed product is preferably chicken manure; the reagent used to adjust the moisture content of the pre-hydrolyzed product is preferably distilled water; and the reagent used to adjust the pH of the pre-hydrolyzed product is preferably a 0.02M Ca(OH)2 aqueous solution. The C / N ratio, moisture content, and pH defined in the present invention enable rapid detonation and rapid decomposition of the compost.

[0043] After obtaining the compost material, the present invention composts the compost material into a pile to perform a first composting process until the temperature at the center of the pile reaches 50-65°C, thereby obtaining a first pile. The ventilation rate of the first compost is 0.05-0.15 L / min. In the present invention, the ventilation rate of the first compost is preferably 0.1 L / min. In the present invention, the temperature at the center of the pile is preferably 55-60°C.

[0044] The present invention has no special limitation on the specifications of the pile body, and the pile body setting of conventional composting in the art can be adopted.

[0045] After obtaining the first pile, the present invention mixes the first pile with the first functional material and performs a second composting process until the center temperature of the pile reaches 43-48°C, thereby obtaining the second pile. The second composting process includes: aeration at 0% for 0-24 hours; after 24 hours, aeration at 0.05-0.15 L / min. The first functional material includes metal oxides and / or organic matter containing humic acid precursors. In the present invention, the center temperature of the pile is preferably 45°C.

[0046] In the present invention, the second composting procedure includes: from 0 to 24 hours, the ventilation volume is 0; after 24 hours, the ventilation volume is 0.05 to 0.15 L / min; the ventilation volume is preferably 0.1 L / min; the functional material includes metal oxides or organic matter containing humic acid precursors.

[0047] In the present invention, the highly efficient lignocellulose hydrolyzing bacterial agent is preferably a straw and animal feces mixed fermentation liquid purchased from Heilongjiang Junyi Liangkang Technology Development Co., Ltd.; the straw and animal feces mixed fermentation liquid comprises Bacteroides thetaiotaomicron, Lachnospiraceae and Clostridium; the ratio of the effective viable counts of Bacteroides thetaiotaomicron, Lachnospiraceae and Clostridium is 3:(0.5-1.5):(0.5-1.5), more preferably 3:1:1; the total effective viable count of the highly efficient lignocellulose hydrolyzing bacterial agent is preferably 1×10 7 ~1×10 9 CFU / mL, more preferably 1×10 8 CFU / mL; the ratio of the volume of the high-efficiency lignocellulose hydrolyzing agent to the mass of the first pile is preferably (500-1000) μL: (1-1.5) kg, and more preferably 800 μL: 1.2 kg.

[0048] In the present invention, the first functional material includes metal oxides and / or organic matter containing humic acid precursors. In the present invention, the organic matter containing humic acid precursors is preferably selected from one or more of reducing sugars, amino acids, chicken manure and biochar; the addition amount of the organic matter containing humic acid precursors is preferably 20‰ to 25‰ of the dry weight of the first pile, and more preferably 22‰; the organic matter containing humic acid precursors is used to provide humic acid precursors. In the present invention, the metal oxide is preferably selected from one of iron oxide, manganese dioxide and copper oxide; the addition amount of the metal oxide is preferably 2‰ to 8‰ of the dry weight of the first pile, and more preferably 3‰ to 5‰; during the composting process, the metal oxide can accelerate the polymerization of humic acid by receiving protons released by the humic acid precursor.

[0049] In the present invention, when the central temperature of the pile reaches 50-65°C, the composting enters a high-temperature period. During this period, the addition of a high-efficiency lignocellulose hydrolyzing agent and a functional material to the first material promotes the rapid polymerization of small-molecule organic components obtained by hydrolysis to form humic acid. After entering the high-temperature period of composting, the present invention immediately stops ventilation while adding the functional material and the high-efficiency lignocellulose hydrolyzing agent, creating an anaerobic environment for the pile, promoting the rapid condensation of humic acid precursor compounds synthesized by decomposition or microorganisms. The functional material acts as a chemical catalyst, promoting the anaerobic metabolism of humic acid precursor compounds by microorganisms under anaerobic conditions, providing a substrate for the formation of humic acid. At the same time, the anaerobic conditions enable the functional material to maximize its chemical catalyst properties and reduce the oxidation of organic components. After ventilation is restored, the functional material can continue to function, namely, it can act as a biological enzyme activity activator to stimulate enzyme activity and further accelerate the oxidative polymerization of humic acid precursors.

[0050] After obtaining the second pile, the present invention mixes the second pile with a second functional material and performs a third composting until the pile temperature reaches 33-35° C. to obtain a compost product; the second functional material is selected from one of minerals, biochar and metal oxides.

[0051] In the present invention, the added amount of the mineral or biochar is preferably 7% to 8% of the dry weight of the second pile; the mineral preferably includes montmorillonite and / or illite.

[0052] In the present invention, the metal oxide is preferably selected from one of iron oxide, manganese dioxide and copper oxide; the added amount of the metal oxide is 2‰ to 8‰ of the dry weight of the second pile, more preferably 3‰ to 5‰.

[0053] In the present invention, when the central temperature of the pile reaches 43-48° C., it enters the late stage of composting, and minerals and metal ion oxides are added to the pile to carry out the third composting to protect the formed humic acid molecules from being further hydrolyzed by microorganisms.

[0054] In the present invention, during the first, second, and third composting processes, the moisture content of the compost is preferably maintained at 60% to 70%, more preferably 65%. During the implementation of the present invention, the moisture loss of the compost is checked daily, and the compost is regularly turned and water is replenished. During composting in the composting device, the device is equipped with a moisture detector to provide real-time feedback on the moisture content of the compost.

[0055] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] Example 1

[0057] Experimental materials: Rice straw was from the rice harvest residue of the previous year; chicken manure was from fresh samples from the chicken farm; and the high-efficiency lignocellulose hydrolyzing agent was from the straw composting agent produced by Heilongjiang Junyi Liangkang Technology Development Co., Ltd.

[0058] The method of this embodiment consists of the following steps:

[0059] 1. Before composting, the obtained rice straw is crushed into a length of 2 to 3 cm; the prepared Fenton reagent (Fenton solvent accounts for 80% of the dry weight of the straw) is used to soak at 25° C. for 2 hours to obtain a pre-hydrolyzed product; the Fenton reagent uses a hydrogen peroxide aqueous solution with a volume concentration of 30% as a solvent and dissolves ferrous chloride; the volume molar concentration ratio of the ferrous chloride to hydrogen peroxide is 0.02:1.5.

[0060] 2. Chicken manure was then used to adjust the C / N of the pre-hydrolyzed product to 28:1, and a 0.02M Ca(OH)2 aqueous solution was used for acid-base neutralization to adjust the pH value of the pre-hydrolyzed product to 7. Distilled water was used to adjust the moisture content of the pre-hydrolyzed product to 65% to obtain compost material.

[0061] 3. Pile the compost material to perform the first composting, and after the first compost enters the high temperature period (the temperature at the center of the pile is 50° C.), obtain the first pile;

[0062] 4. Inoculate the first windrow with a high-efficiency lignocellulose hydrolyzing agent and add MnO2. Stop aeration in the windrow and maintain for 24 hours. Then resume aeration at a rate of 0.1 L / min. When the central temperature of the windrow drops and stabilizes at 33-38°C, the compost enters the mature stage, and obtain the second windrow.

[0063] The high-efficiency lignocellulose hydrolyzing bacterial agent is composed of Bacteroides thetaiotaomicron, Lachnospiraceae and Clostridium; the ratio of the effective viable bacteria of Bacteroides thetaiotaomicron, Lachnospiraceae and Clostridium is 3:1:1; the total effective viable bacteria of the high-efficiency lignocellulose hydrolyzing bacterial agent is preferably 1×10 8 CFU / mL; the ratio of the volume of the efficient lignocellulose hydrolyzing agent to the mass of the first pile is 800μL:1.2kg, and the amount of MnO2 added accounts for 2‰ of the dry weight of the first pile;

[0064] 5. Add 7.5% of the dry weight of montmorillonite to the second pile and carry out the third composting until the pile temperature reaches 33-35°C to protect the formed humic acid molecules.

[0065] Example 2

[0066] 1. Before composting, crush the rice straw to 2-3 cm in length; soak it in 8M concentrated nitric acid at 25°C for 12 hours to obtain a pre-hydrolyzed product; the concentrated nitric acid is soaked at a ratio of 10 ml per gram of straw.

[0067] 2. Chicken manure was then used to adjust the C / N of the pre-hydrolyzed product to 28:1, and a 0.02M Ca(OH)2 aqueous solution was used for acid-base neutralization to adjust the pH value of the pre-hydrolyzed product to 7. Distilled water was used to adjust the moisture content of the pre-hydrolyzed product to 65% to obtain compost material.

[0068] 3. Pile the compost material to perform the first composting, and after the first compost enters the high temperature period (the temperature at the center of the pile is 50° C.), obtain the first pile;

[0069] 4. Inoculate the first windrow with a high-efficiency lignocellulose hydrolyzing agent and add MnO2. Stop aeration in the windrow and maintain for 24 hours. Then resume aeration at a rate of 0.1 L / min. When the central temperature of the windrow drops and stabilizes at 33-38°C, the compost enters the mature stage, and obtain the second windrow.

[0070] The high-efficiency lignocellulose hydrolyzing bacterial agent is composed of Bacteroides thetaiotaomicron, Lachnospiraceae and Clostridium; the ratio of the effective viable bacteria of Bacteroides thetaiotaomicron, Lachnospiraceae and Clostridium is 3:1:1; the total effective viable bacteria of the high-efficiency lignocellulose hydrolyzing bacterial agent is preferably 1×10 8 CFU / mL; the ratio of the volume of the efficient lignocellulose hydrolyzing agent to the mass of the first pile is 800μL:1.2kg; the amount of MnO2 added accounts for 2‰ of the dry weight of the first pile;

[0071] 5. Add 7.5% of the dry weight of montmorillonite to the second pile and carry out the third composting until the pile temperature reaches 33-35°C to protect the formed humic acid molecules.

[0072] The rest is the same as Example 1.

[0073] Example 3

[0074] 1. Before composting, crush the corn stalks to 2-3 cm in length; soak them in the prepared Fenton reagent (Fenton solvent accounts for 80% of the dry weight of the stalks) at 25°C for 2 h to obtain a pre-hydrolyzed product;

[0075] 2. Chicken manure was then used to adjust the C / N of the pre-hydrolyzed product to 28:1, and a 0.02M Ca(OH)2 aqueous solution was used for acid-base neutralization to adjust the pH value of the pre-hydrolyzed product to 7. Distilled water was used to adjust the moisture content of the pre-hydrolyzed product to 65% to obtain compost material.

[0076] 3. The compost material is piled to perform the first composting. After the first compost enters the high temperature period (the temperature at the center of the pile is 50° C.), a high-efficiency lignocellulose hydrolyzing bacterial agent is inoculated into the pre-hydrolyzed product to obtain a first pile. The high-efficiency lignocellulose hydrolyzing bacterial agent is composed of Bacteroides thetaiotaomicron, Lachnospiraceae, and Clostridium. The ratio of the effective viable bacteria counts of Bacteroides thetaiotaomicron, Lachnospiraceae, and Clostridium is 3:1:1. The total effective viable bacteria count of the high-efficiency lignocellulose hydrolyzing bacterial agent is preferably 1×10 8CFU / mL; the ratio of the volume of the highly efficient lignocellulose hydrolyzing agent to the mass of the first pile is 800 μL:1.2 kg;

[0077] 4. Mix the first pile with MnO2, with the amount of MnO2 added accounting for 2‰ of the dry weight of the first pile, and stop aerating the pile. After maintaining for 24 hours, resume aeration at a rate of 0.1 L / min. When the central temperature of the pile drops and stabilizes at 33-38°C, the compost enters the mature stage, and obtain the second pile;

[0078] 5. Add 7.5% of the dry weight of the second pile of illite to the second pile for the third composting until the pile temperature reaches 33-35°C to protect the humic acid molecules that have been formed.

[0079] The rest is the same as Example 1.

[0080] Example 4

[0081] 1. Before composting, crush the corn stalks to 2-3 cm in length; soak them in 8M concentrated nitric acid at 25°C for 12 hours to obtain a pre-hydrolyzed product; the concentrated nitric acid is soaked at a ratio of 10 ml per gram of stalk.

[0082] 2. Chicken manure was then used to adjust the C / N of the pre-hydrolyzed product to 28:1, and a 0.02M Ca(OH)2 aqueous solution was used for acid-base neutralization to adjust the pH value of the pre-hydrolyzed product to 7. Distilled water was used to adjust the moisture content of the pre-hydrolyzed product to 65% to obtain compost material.

[0083] 3. The compost material is piled to perform the first composting. After the first compost enters the high temperature period (the temperature at the center of the pile is 50° C.), a high-efficiency lignocellulose hydrolyzing bacterial agent is inoculated into the pre-hydrolyzed product to obtain a first pile. The high-efficiency lignocellulose hydrolyzing bacterial agent is composed of Bacteroides thetaiotaomicron, Lachnospiraceae, and Clostridium. The ratio of the effective viable bacteria counts of Bacteroides thetaiotaomicron, Lachnospiraceae, and Clostridium is 3:1:1. The total effective viable bacteria count of the high-efficiency lignocellulose hydrolyzing bacterial agent is preferably 1×10 8 CFU / mL; the ratio of the volume of the highly efficient lignocellulose hydrolyzing agent to the mass of the first pile is 800 μL:1.2 kg;

[0084] 4. The first pile was mixed with biochar and MnO2, with the amount of biochar and MnO2 added accounting for 2‰ of the dry weight of the first pile, and ventilation to the pile was stopped. After maintaining for 24 hours, ventilation was resumed at a rate of 0.1 L / min. When the central temperature of the pile dropped and stabilized at 43-48°C, the compost entered the mature stage, and the second pile was obtained;

[0085] 5. Add 7.5% of the dry weight of the second pile of iron oxide to the second pile to protect the formed humic acid molecules, and perform the third composting until the pile temperature reaches 33-35° C. to obtain a compost product.

[0086] The rest is the same as Example 1.

[0087] Example 5

[0088] 1. Before composting, crush the soybean straw to 2-3 cm in length; soak it in the prepared Fenton reagent (Fenton solvent accounts for 80% of the dry weight of the straw) at 25°C for 2 hours to obtain a pre-hydrolyzed product;

[0089] 2. Chicken manure was then used to adjust the C / N of the pre-hydrolyzed product to 28:1, and a 0.02M Ca(OH)2 aqueous solution was used for acid-base neutralization to adjust the pH value of the pre-hydrolyzed product to 7. Distilled water was used to adjust the moisture content of the pre-hydrolyzed product to 65% to obtain compost material.

[0090] 3. The compost material is piled to perform the first composting. After the first compost enters the high temperature period (the temperature at the center of the pile is 50° C.), a high-efficiency lignocellulose hydrolyzing bacterial agent is inoculated into the pre-hydrolyzed product to obtain a first pile. The high-efficiency lignocellulose hydrolyzing bacterial agent is composed of Bacteroides thetaiotaomicron, Lachnospiraceae, and Clostridium. The ratio of the effective viable bacteria counts of Bacteroides thetaiotaomicron, Lachnospiraceae, and Clostridium is 3:1:1. The total effective viable bacteria count of the high-efficiency lignocellulose hydrolyzing bacterial agent is preferably 1×10 8 CFU / mL; the ratio of the volume of the highly efficient lignocellulose hydrolyzing agent to the mass of the first pile is 800 μL:1.2 kg;

[0091] 4. Mix the first pile with MnO2, with the amount of MnO2 added accounting for 2‰ of the dry weight of the first pile, and stop aerating the pile. After maintaining for 24 hours, resume aeration at a rate of 0.1 L / min. When the central temperature of the pile drops and stabilizes at 33-38°C, the compost enters the mature stage, and obtain the second pile;

[0092] 5. Add 7.5‰ of the dry weight of the second pile of iron oxide to the second pile and carry out the third composting until the pile temperature reaches 33-35℃ to protect the humic acid molecules that have been formed.

[0093] The rest is the same as Example 1.

[0094] Comparative Example 1

[0095] Before composting, the rice straw was crushed to a length of 2 to 3 cm and subjected to traditional composting, that is, chicken manure was used to adjust the carbon-nitrogen ratio of the material to (25 to 30):1, and distilled water was used to adjust the moisture content of the material to 65%, and then composting began.

[0096] After 60 days of composting, the straw degradation rate in Example 1 was increased by 33.1% and the humic acid content was increased by 48.7%. This indicates that the method of the present invention can effectively promote the microbial cell factory to drive the organic components to form humic acid in a targeted manner.

[0097] Comparative Example 2

[0098] Before composting begins, the obtained rice straw is crushed to a length of 2 to 3 cm and soaked at 25° C. for 2 hours using a prepared Fenton reagent (the Fenton solvent accounts for 80% of the dry weight of the straw) to obtain a pre-hydrolyzed product. The hydrolyzed product is then washed with water to a pH of approximately 7 to 8, the carbon-nitrogen ratio of the material is adjusted to 30 and the moisture content to 65% using urea, and the above-mentioned high-efficiency cellulose hydrolyzing bacterial agent is inoculated to begin composting with the inoculated bacterial agent.

[0099] After 60 days of composting, the inoculated inoculum increased straw hydrolysis efficiency by 27% compared to traditional composting, while humic acid production increased by only 1.5%, a less-than-ideal result. This suggests that the mixed inoculum is effective at hydrolyzing cellulose but less effective at promoting the targeted formation of humic acid from the hydrolysis products.

[0100] Comparative Example 3

[0101] Before composting begins, the obtained rice straw is crushed to a length of 2 to 3 cm, the carbon-nitrogen ratio of the material is adjusted to 30 using chicken manure, the moisture content of the material is adjusted to 65% with distilled water, and MnO2 is added at 2‰ of the dry weight of the material and mixed evenly, and composting begins.

[0102] After 60 days of composting, it was found that compared with traditional composting, the addition of MnO2 to composting did not improve the efficiency of cellulose hydrolysis, but the efficiency of humic acid production increased by 31.1%, and the promoting effect mainly occurred in the early stage of composting, indicating that the addition of MnO2 is effective in increasing humic acid production, and it mainly occurs in the short term after the addition of MnO2.

[0103] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for increasing the humic acid content of compost by staged treatment, comprising the following steps: 1) soaking the organic solid waste to be treated in a hydrolysis solution to perform pre-hydrolysis to obtain a pre-hydrolysis product; the hydrolysis solution includes a Fenton reagent or a nitric acid aqueous solution; 2) adjusting the C / N ratio of the pre-hydrolyzed product to (25-30):

1. the water content is 60%-70%, the pH is 7.0-7.5, and inoculating a high-efficiency lignocellulose hydrolyzing agent to obtain a compostable material; The high-efficiency lignocellulose hydrolyzing bacterial agent comprises Bacteroides thetaiotaomicron, Lachnospiraceae and Clostridium; the ratio of the effective viable bacteria counts of Bacteroides thetaiotaomicron, Lachnospiraceae and Clostridium is 3:(0.5-1.5):(0.5-1.5); the total effective viable bacteria count of the high-efficiency lignocellulose hydrolyzing bacterial agent is 1×10 7 ~1×10 9 CFU / mL; 3) piling the compost material to perform a first composting process until the temperature at the center of the compost body reaches 50-65° C., thereby obtaining a first compost; wherein the ventilation rate of the first compost is 0.05-0.15 L / min; 4) mixing the first pile material and the first functional material, and performing a second composting process until the temperature at the center of the pile body reaches 43-48° C., thereby obtaining a second pile material; The second composting procedure includes: from 0 to 24 hours, the ventilation rate is 0; after 24 hours, the ventilation rate is 0.05 to 0.15 L / min; The first functional material includes metal oxides and / or organic matter containing humic acid precursors; The metal oxide in step 4) is selected from one of iron oxide, manganese dioxide and copper oxide; The organic matter containing humic acid precursors in step 4) is selected from one or more of reducing sugars, amino acids, chicken manure, and biochar; 5) mixing the second pile material and the second functional material, and performing a third composting process until the pile body temperature reaches 33-35° C., thereby obtaining a compost product; The second functional material is selected from one of minerals, biochar and metal oxides; The minerals in step 5) include montmorillonite and / or illite; The metal oxide in step 5) is selected from one of iron oxide, manganese dioxide and copper oxide.

2. The method according to claim 1, characterized in that The concentration of the nitric acid aqueous solution in step 1) is 7.5-8.5 mol / L; the volume of the nitric acid aqueous solution and the mass of the organic solid waste to be treated are of the same order of magnitude, and the ratio is 10:(0.5-1.5).

3. The method according to claim 1, characterized in that In step 1), the Fenton reagent is prepared by dissolving ferrous chloride in a 30% volume concentration aqueous hydrogen peroxide solution as a solvent; the volume molar concentration ratio of the ferrous chloride to hydrogen peroxide is (0.01-0.03):1.5; and the mass ratio of the Fenton reagent to the organic solid waste to be treated is (1-3):(0.5-3).

4. The method according to claim 1 or 2, characterized in that In step 1), when the hydrolysis solution is a nitric acid aqueous solution, the pre-hydrolysis temperature is 20 to 30° C.; and the pre-hydrolysis time is 10 to 14 hours.

5. The method according to claim 1 or 3, characterized in that In step 1), when the hydrolysis solution is Fenton's reagent, the pre-hydrolysis temperature is 20-30° C.; and the hydrolysis time is 1.5-2.5 h.

6. The method according to claim 1, characterized in that The ratio of the volume of the high-efficiency lignocellulose hydrolyzing agent to the mass of the first pile is (500-1000) μL: (1-1.5) kg.

7. The method according to claim 1, characterized in that The amount of organic matter containing humic acid precursors added in step 4) is 20‰ to 25‰ of the dry weight of the first pile.

8. The method according to claim 1, characterized in that The amount of the metal oxide added in step 4) is 2‰ to 8‰ of the dry weight of the first pile.

9. The method according to claim 1, characterized in that In step 5), the amount of the mineral or biochar added is independently 7% to 8% of the dry weight of the second pile.

10. The method according to claim 1, characterized in that The amount of the metal oxide added in step 5) is 2‰ to 8‰ of the dry weight of the second pile.