Bio-pretreated straw and livestock manure mixed high-temperature solid two-phase anaerobic fermentation method

Abstract

The invention belongs to the field of resource cyclic utilization of biomass energy and organic matters, and particularly relates to a mixed high-temperature solid two-phase anaerobic fermentation method of biologically pretreated straws and livestock manure. According to the invention, a mixture of biologically pretreated straws and livestock manure is used as a raw material to carry out high-temperature two-phase anaerobic fermentation to prepare the biogas, and the solid mass content of the raw material is 20-25%. According to the method, a high-temperature and high-solid fermentation form is adopted, so that the reaction rate is increased, the emission of biogas slurry can be reduced, and the utilization amount of straws is increased. On the whole, the water consumption can be effectively reduced, and the biogas slurry yield is reduced; the hydrolysis rate of the straw can be increased, and the biogas yield is increased; the anaerobic fermentation period can be shortened.

Description

Technical Field

[0001] The invention belongs to the field of biomass energy and organic matter resource recycling, and particularly relates to a method for high-temperature solid two-phase anaerobic fermentation of mixed biological pretreated straw and livestock manure. Background Art

[0002] Crop straw and livestock manure are the main agricultural wastes with wide sources and high yields. If they are not handled in time, they will cause ecological and environmental problems and pose great hidden dangers to residents' lives. For example, straw burning and arbitrary discharge of livestock and poultry manure will bring serious ecological and social environmental problems, and also cause waste of organic resources. The recycling of straw and livestock and poultry manure is conducive to ecological environmental construction, the recycling of waste resources and the improvement of residents' living environment. Anaerobic fermentation technology can convert organic matter into biogas, which is in line with the country's "dual carbon" goals and the needs of green energy transformation.

[0003] However, crop straw has a complex structure, and the entangled structure composed of cellulose, hemicellulose and lignin is not easy to degrade, which leads to low utilization rate of cellulose in the straw by anaerobic fermentation microorganisms, long anaerobic fermentation cycle, easy acidification, low methane production and other problems. Therefore, improving the degradation rate of straw during anaerobic fermentation and shortening the fermentation cycle have become urgent problems to be solved in anaerobic fermentation technology. Summary of the invention

[0004] In order to improve the degradation rate and degradation speed of organic matter in straw, realize the resource recycling of agricultural organic matter such as straw and livestock manure and increase gas production, the present invention provides a method for biological pretreatment of straw and livestock manure by high-temperature solid two-phase anaerobic fermentation.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for high-temperature solid two-phase anaerobic fermentation of a mixture of biologically pretreated straw and livestock manure, wherein the mixture of biologically pretreated straw and livestock manure is used as a raw material for high-temperature two-phase anaerobic fermentation to produce biogas, and the mass content of solids during fermentation is 20%-25%.

[0007] The crop straw is preferably crushed to 3-10 cm.

[0008] Furthermore, the biological agent is mixed with the straw for pretreatment at room temperature, the amount of dry matter of the biological agent added is 0.1%-0.5% of the mass of the dry matter of the straw, and the pretreatment time is 4-14 days.

[0009] When the moisture content of the straw is 60-70%, ventilation is performed at an air volume of 0.03-0.06 L / h per kg of straw during pretreatment.

[0010] In the pretreatment process of the present invention, the microorganisms in the biological agent can destroy the dense lignocellulose structure of corn stalks, degrade lignin, and make the cellulose in the stalks easily utilized by anaerobic microbial flora. In the pretreatment process, the microbial flora can degrade about 20% of the lignin, and the temperature can reach 45-70°C. The heat in the pretreatment process is used to add livestock manure to the stalks for the next step of anaerobic fermentation.

[0011] The C / N ratio of the mixture of straw and livestock manure is 22-31:1, and the mass ratio is 1-2:1.

[0012] Furthermore, high temperature acid phase anaerobic fermentation is first carried out, the fermentation temperature during the acid phase anaerobic fermentation is 50-55°C, and the fermentation period is 5-9 days.

[0013] The inoculum of the high temperature acid phase anaerobic fermentation is fresh cow dung, and the inoculum amount is 30% to 50% of the dry weight of the fermentation raw material.

[0014] It is recommended that the acid phase anaerobic fermentation inoculum be cultured in an environment of 50-55°C for 2-4 days, and then inoculated as the acid phase inoculum after it has adapted to the high temperature environment.

[0015] After the acid phase anaerobic fermentation is completed, the methane phase anaerobic fermentation is carried out, the fermentation temperature is 50-55°C, and the fermentation period is 7-14 days.

[0016] The methane phase anaerobic fermentation uses dehydrated sludge as inoculum, and the inoculum amount is 30-50% of the mass of the material entering the methane phase anaerobic fermentation. After adding the inoculum, the solid content of the entire fermentation material is adjusted to 20%-25%.

[0017] The dewatered sludge preferably has its solid content increased to about 20%, and then is cultured in a high temperature environment of 50-55° C. for about 2 months to adapt it to the high temperature anaerobic fermentation environment.

[0018] The present invention adds different inoculants respectively, divides the anaerobic fermentation into acid phase and methane phase fermentation, and can accelerate the reaction speed of the anaerobic fermentation and the gas production per unit straw.

[0019] Specifically, the method of the present invention for high-temperature solid two-phase anaerobic fermentation of mixed biological pretreated straw and livestock manure includes the following steps:

[0020] 1) First, the straw is crushed into 3-10 cm, and the biomass straw is pretreated with a biological agent (commercial microorganisms or composite bacteria cultured in the laboratory), the dry matter mass of the biological agent added is 0.1%-0.5% of the dry matter mass of the straw, the moisture content of the straw is 60-70%, the pretreatment ventilation volume is 0.03-0.06L / kg (straw)·h, and the pretreatment time is 4-14d;

[0021] 2) The pretreated straw and livestock manure are mixed in a mass ratio of 1-2:1 and a C / N ratio of 22-31:1, and fresh cow dung accounting for 30% of the dry weight of the fermentation raw material is added as an inoculum, and the solid content of the overall fermentation material is adjusted to 20%-25%, and acid phase anaerobic fermentation is carried out at 50-55° C. for a fermentation period of 7 days;

[0022] 3) The reactants after the acid phase anaerobic fermentation are introduced into the methane phase reactor, 30-50% of the mass of the reactants are added with methane phase inoculum, the solid content of the whole fermentation material is adjusted to 20%-25%, and the methane phase anaerobic fermentation is carried out at 50-55° C. for a fermentation period of 10-14 days.

[0023] After the fermentation of straw and livestock manure is completed, the biogas is purified to obtain high-purity methane, which can be used as biogas, and the biogas liquid and biogas residue can be used as biofertilizer. The average methane content of the method of the present invention is 45%-55%, and the methane output is 100-200mL / g straw.

[0024] The biological bacterial agent of the present invention can be obtained by, but is not limited to, the following method: the bacterial strains are first cultured in a liquid culture medium at 30° C. for 2 to 3 hours; then inoculated and cultured for 2 to 3 days; and then the liquid culture medium is used for further expansion and culture, and then the mixture is mixed in equal proportions to obtain the composite biological bacterial agent.

[0025] The bacterial species are Gloeophyllum trabeum CGMCC 5.98, Bacillus circulans CGMCC 1.2411, Pseudomonas aeruginosa CGMCC1.10712, Streptomyces badius CGMCC 4.1406, Phanerochaete chryosporium, Trichoderma viride, Aspergillus niger and Coriolus versicolor.

[0026] The above-mentioned culture process of a single bacterial strain is a conventional method in the art and has no special requirements.

[0027] In the present invention, the following methods are provided, but are not limited to the following methods:

[0028] The fungi Phanerochaete chrysosporium, Coriolus versicolor, Trichoderma viride, Aspergillus niger and Glehnia littoralis were inoculated and cultured on PDA solid culture medium, respectively; the bacteria Bacillus circulans, Pseudomonas aeruginosa and Streptomyces kiwano were inoculated and cultured on plate count culture medium, respectively.

[0029] Before inoculation and culture, the solid culture medium or plate count medium is sterilized at high temperature, specifically at 121°C for 15-30 minutes; after cooling to room temperature, the activated bacteria are taken with a sampling loop and evenly smeared on the surface of the solid culture medium or plate count medium, and cultured for 2 to 3 days.

[0030] Afterwards, according to the inoculation amount of 10% for fungi and 1-5% for bacteria, use an inoculation loop to take the strain (usually 1-2 loops) into a conical flask, and culture it continuously for 2-3 days in a constant temperature shaking incubator at 30°C and 120r / min for expansion culture.

[0031] The liquid culture medium used in the above-mentioned preliminary culture and expanded culture may be, but is not limited to, the following culture medium:

[0032] The culture medium used for Phanerochaete chrysosporium, Coriolus versicolor, Trichoderma viride, Aspergillus niger, and Glehnia littoralis is PDA culture medium: 1000 mL of potato extract, 20 g of glucose; sterilized at 115°C.

[0033] The culture medium used for Bacillus circulans is nutrient broth medium: 5 g peptone, 30 g beef, 5 g NaCl, 1000 mL distilled water; sterilized at 121°C.

[0034] The culture medium for Pseudomonas aeruginosa is LB medium: 5 g yeast extract, 10 g peptone, 10 g NaCl, 1000 mL distilled water; sterilized at 121°C.

[0035] The culture medium for Streptomyces chestnut brown is yeast powder and starch culture medium: 2 g yeast extract, 10 g soluble starch, 1000 mL distilled water; sterilized at 121°C.

[0036] Compared with the currently mature wet anaerobic fermentation process, the present invention adopts a high-temperature, high-solid fermentation form, which can accelerate the reaction rate while reducing the discharge of biogas slurry, increasing the utilization of straw, and realizing the high-value utilization of biogas residues; different inoculants are added in the acid phase and methane phase fermentation to accelerate the reaction speed of anaerobic fermentation and increase the gas production; during pretreatment, composite bacteria are used to pretreat the straw to increase the degradation rate of its lignin, cellulose and hemicellulose. In general, the present invention can effectively reduce water consumption, reduce biogas slurry discharge and disposal problems; can increase the hydrolysis rate of straw, have a high inactivation rate of pathogens in organic matter, can increase the solubility of organic particles and biogas production; can greatly shorten the anaerobic fermentation cycle and keep it within 20 days. At the same time, the solid anaerobic fermentation device occupies a small area, has a high daily organic load, and has a large gas production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention is a schematic flow chart of a method for high-temperature solid two-phase anaerobic fermentation of biologically pretreated straw mixed with livestock manure. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is described below with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0039] Example 1

[0040] Biological pretreatment of straw and livestock manure mixed with high temperature solid two-phase anaerobic fermentation, the steps are as follows:

[0041] 1) Cultivating a composite bacterial community for straw pretreatment in the laboratory, wherein the composite bacteria are obtained by culturing Phanerochae techrysosporium, Coriolus versicolor, Trichoderma viride, Aspergillus niger, Gloeophyllum trabeum, Bacillus circulans, Pseudomonas aeruginosa, and Streptomyces badius, and the steps are as follows:

[0042] Activation of composite bacteria: adding each of the bacterial species into a liquid culture medium and culturing at 30° C. for 2 to 3 hours;

[0043] Inoculation culture: First sterilize the solid culture medium or plate count culture medium at 121℃ for 15-30min. After cooling to room temperature, use a sampling loop to take the activated bacteria and evenly spread them on the surface of the solid culture medium or plate count culture medium and culture for 2-3 days.

[0044] Among them, Phanerochaete chrysosporium, Coriolus versicolor, Trichoderma viride, Aspergillus niger, and Glehnia littoralis were inoculated and cultured on PDA solid culture medium; Bacillus circulans, Pseudomonas aeruginosa, and Streptomyces kiwi were inoculated and cultured on plate count medium. The ultraviolet light needs to be turned on for half an hour before operating on the sterile operating table. The above process ensures that there is no contamination.

[0045] Expanded culture: Perform the operation on a sterile operating table, use an inoculation loop to take 1-2 loops of the strain into a conical flask containing liquid culture medium, and culture it continuously for 2-3 days in a constant temperature shaking incubator at 30°C and 120r / min for expanded culture.

[0046] The culture solutions of the above-mentioned bacterial species are mixed in equal proportions to obtain a composite biological bacterial agent.

[0047] 2) mixing corn stalks crushed to a particle size of 5-10 cm with the composite biological agent of step 1) at a mass ratio of 1:1, and pretreating for 14 days at 30° C., a ventilation volume of 0.06 L / kg (stalk)·h, and a stalk moisture content of 60% to obtain pretreated stalks;

[0048] During the pretreatment process, when the straw was pretreated with the composite biological agent for 3 days, the degradation rates of cellulose, hemicellulose and lignin could reach 15.5%, 19.4% and 10.8%, respectively; after 14 days of pretreatment, the degradation rates of cellulose, hemicellulose and lignin could reach 27.7%, 30.4% and 18.3%, respectively.

[0049] 3) adding pig manure to the straw after pretreatment for 14 days, with a mass ratio of straw to pig manure of 2:1, and a C / N of the mixture of 31. Adding fresh cow manure at 30% of the dry weight of the fermentation substrate, adjusting the solid content of the fermentation material to 20% by adding water, performing acid phase anaerobic fermentation at 55°C, and adding the feed liquid to the methane phase reactor after 7 days of fermentation;

[0050] 4) In the methane phase reactor, dehydrated sludge was added as inoculum in an amount of 30%, the solid content of the whole fermentation material was adjusted to 20%, and methane phase anaerobic fermentation was carried out at 55° C. for a fermentation period of 10 days.

[0051] Under the above conditions, straw and pig manure were mixed and anaerobically fermented for 17 days, and the average methane content in the obtained biogas was 54%, and the gas production per unit mass of straw reached 150mL / g straw.

[0052] The sources of the strains used are as follows:

[0053] Gloeophyllum trabeum (CGMCC 5.98), Bacillus circulans (CGMCC 1.2411), Pseudomonas aeruginosa (CGMCC 1.10712), and Streptomyces badius (CGMCC 4.1406) were purchased from China General Microbiological Culture Collection Center;

[0054] Phanerochaete chryosporium, No.: BNCC189286;

[0055] Trichoderma viride, number: BNCC336351;

[0056] Aspergillus niger, No. 186380; The above three strains were provided by the Key Laboratory of New Materials and Equipment for Rural Renewable Energy of the Ministry of Agriculture, Henan Agricultural University;

[0057] Coriolus versicolor, number: BNCC123332; provided by the Laboratory of College of Life Sciences, Henan Agricultural University.

[0058] Example 2

[0059] Biological pretreatment of straw and livestock manure mixed with high temperature solid two-phase anaerobic fermentation, the steps are as follows:

[0060] 1) Obtaining a composite biological agent in the manner of Example 1;

[0061] 2) mixing corn stalks with a crushed particle size of 3-5 cm with a composite biological agent at a ratio of 1:1, pre-treating for 14 days at 30° C., a ventilation rate of 0.06 L / kg (stalk)·h, and a stalk moisture content of 60%, to obtain pre-treated stalks;

[0062] 3) adding pig manure to the pretreated straw, the mass ratio of straw to pig manure is 2:1, and the C / N of the mixture is 31. Adding 30% fresh cow manure as the fermentation substrate, and adjusting the solid content of the fermentation material to 20% by adding water, and performing acid phase anaerobic fermentation at 55° C. After 7 days of acid phase anaerobic fermentation, the feed liquid is added to the methane phase reactor;

[0063] 4) In the methane phase reactor, dehydrated sludge was added as inoculum in an amount of 30%, the solid content of the whole fermentation product was adjusted to 20%, and methane phase anaerobic fermentation was carried out at 55° C. for a fermentation period of 10 days.

[0064] Under the above conditions, the straw and pig manure were mixed and anaerobically fermented for 17 days, and the average methane content in the obtained biogas was 55%, and the gas production per unit mass of straw reached 200mL / g straw.

[0065] Comparative Example 1

[0066] The method for biological pretreatment of straw and livestock manure mixed with high-temperature solid two-phase anaerobic fermentation comprises the following steps:

[0067] 1) using commercially available composting agent Yuanjiebao (purchased from Shandong Weilan Biotechnology Co., Ltd., according to the instructions, the main ingredients are Aspergillus oryzae, yeast, lactic acid bacteria and spore bacteria, etc., with an effective viable count of 5 billion cfu / g), adding 0.1% of the mass of the straw to the corn straw with a crushed particle size of 3 to 5 cm, pre-treating for 14 days at 20° C., a ventilation volume of 0.06 L / kg (straw)·h, and a moisture content of 60%, to obtain pre-treated straw;

[0068] 2) adding pig manure to the pretreated straw, the mass ratio of straw to pig manure is 2:1, and the C / N of the mixture is 31. Adding 30% fresh cow manure as the fermentation substrate, and adjusting the solid content of the inoculum and the substrate to 20% by adding water, and performing acid phase anaerobic fermentation at 55° C. After 7 days of acid phase anaerobic fermentation, the feed liquid is added to the methane phase reactor;

[0069] 3) In the methane phase reactor, dehydrated sludge was added as inoculum in an amount of 30%, the solid content of the reactants was adjusted to 20%, and methane phase anaerobic fermentation was carried out at 55° C. The methane phase anaerobic fermentation cycle was 10 days.

[0070] Under the above conditions, the straw and pig manure were mixed and anaerobically fermented for 17 days, and the average methane content in the obtained biogas was 55%, and the gas production per unit mass of straw reached 100mL / g straw.

[0071] Comparative Example 2

[0072] The method for biological pretreatment of straw and livestock manure mixed with high temperature solid anaerobic fermentation, the steps are as follows:

[0073] 1) Obtaining a composite biological agent in the manner of Example 1;

[0074] 2) mixing corn stalks with a crushed particle size of 3 to 5 cm with a composite biological agent at a ratio of 1:1, pretreating for 14 days at 30° C., a ventilation volume of 0.06 L / kg (stalk)·h, and a moisture content of 60%, to obtain pretreated stalks;

[0075] 3) Pig manure was added to the pretreated straw, the mass ratio of straw to pig manure was 2:1, and the C / N of the mixture was 31. Fresh cow manure was added with 30% of the fermentation substrate, and the solid content of the inoculum and the substrate was adjusted to 20% by adding water, and single-phase anaerobic fermentation was carried out at 55°C.

[0076] Under the above conditions, the straw and cow dung were mixed and anaerobically fermented for 17 days, and the average methane content in the obtained biogas was 43%, and the gas production per unit mass of straw was 60mL / g straw.

[0077] Comparative Example 3

[0078] The method for biological pretreatment of straw and livestock manure mixed with high temperature solid anaerobic fermentation, the steps are as follows:

[0079] 1) Obtaining a composite biological agent in the manner of Example 1;

[0080] 2) mixing corn stalks with a crushed particle size of 3 to 5 cm with a composite biological agent at a ratio of 1:1, pretreating for 14 days at 30° C., a ventilation volume of 0.06 L / kg (stalk)·h, and a moisture content of 60%, to obtain pretreated stalks;

[0081] 3) Pig manure was added to the pretreated straw, the mass ratio of straw to pig manure was 2:1, and the C / N of the mixture was 31. Dehydrated sludge with 30% of the fermentation substrate was added, and the solid content of the inoculum and the substrate was adjusted to 20% by adding water, and single-phase anaerobic fermentation was carried out at 55°C.

[0082] Under the above conditions, the straw and pig manure were mixed and anaerobically fermented for 17 days, and the average methane content in the obtained biogas was 50%, and the gas production per unit mass of straw reached 50mL / g straw.

[0083] Comparative Example 4

[0084] The method for biological pretreatment of straw and livestock manure mixed with high temperature solid anaerobic fermentation, the steps are as follows:

[0085] 1) Obtaining a composite biological agent in the manner of Example 1;

[0086] 2) mixing corn stalks with a crushed particle size of 3 to 5 cm with a composite biological agent at a ratio of 1:1, pretreating for 14 days at 30° C., a ventilation volume of 0.06 L / kg (stalk)·h, and a moisture content of 60%, to obtain pretreated stalks;

[0087] 3) Pig manure was added to the pretreated straw, the mass ratio of straw to pig manure was 1:1, and the C / N of the mixture was 22. Dehydrated sludge with 30% of the fermentation substrate was added, and the solid content of the inoculum and the substrate was adjusted to 20% by adding water, and single-phase anaerobic fermentation was carried out at 55°C.

[0088] Under the above conditions, the straw and pig manure were mixed and anaerobically fermented for 17 days, and the average methane content in the obtained biogas was 50%, and the gas production per unit mass of straw reached 60mL / g straw.

[0089] Comparative Example 5

[0090] The method for biological pretreatment of straw and livestock manure mixed with high temperature solid anaerobic fermentation, the steps are as follows:

[0091] 1) Obtaining a composite biological agent in the manner of Example 1;

[0092] 2) mixing corn stalks with a crushed particle size of 3 to 5 cm with a composite biological agent at a ratio of 1:1, pretreating for 14 days at 30° C., a ventilation volume of 0.06 L / kg (stalk)·h, and a moisture content of 60%, to obtain pretreated stalks;

[0093] 3) adding pig manure to the pretreated straw, the mass ratio of straw to pig manure is 2:1, and the C / N of the mixture is 31. Adding a mixture of 30% fresh cow manure and sludge as a fermentation substrate (the mass ratio of fresh cow manure to sludge is 1:1), and adjusting the solid content of the overall reactant to 20% by adding water, and performing anaerobic fermentation at 55°C;

[0094] Under the above conditions, the straw and cow dung were mixed and anaerobically fermented for 17 days, and the average methane content in the obtained biogas was 47%, and the gas production per unit mass of straw was 90mL / g straw.

[0095] The specific embodiments of the present invention are only for illustrative purposes and do not limit the protection scope of the present invention in any way. Those skilled in the art may modify or change them according to the above description, and these improvements and changes should fall within the protection scope of the claims attached to the present invention.

Claims

1. A method for high-temperature solid two-phase anaerobic fermentation of biologically pretreated straw mixed with livestock manure, characterized in that: Biogas is produced by high-temperature two-phase anaerobic fermentation of a mixture of biologically pretreated straw and livestock manure. The solid content during fermentation is 20%-25%.

2. The method for high-temperature solid two-phase anaerobic fermentation of biologically pretreated straw mixed with livestock manure as claimed in claim 1, characterized in that: The C / N ratio of the mixture of straw and livestock manure is 22-31:1, and the mass ratio is 1-2:

1.

3. The method for high-temperature solid two-phase anaerobic fermentation of biologically pretreated straw mixed with livestock manure as claimed in claim 1, characterized in that: First, high-temperature acid phase anaerobic fermentation is carried out. The fermentation temperature during acid phase anaerobic fermentation is 50-55°C and the fermentation period is 5-9 days.

4. The method for high-temperature solid two-phase anaerobic fermentation of biologically pretreated straw mixed with livestock manure as claimed in claim 3, characterized in that: The inoculum for high-temperature acid phase anaerobic fermentation is fresh cow dung, and the inoculum amount is 30%~50% of the dry weight of the fermentation raw material.

5. The method for high-temperature solid two-phase anaerobic fermentation of biologically pretreated straw mixed with livestock manure as claimed in claim 3, characterized in that: After the acid phase anaerobic fermentation is completed, the methane phase anaerobic fermentation is carried out, the fermentation temperature is 50-55°C, and the fermentation period is 7-14 days.

6. The method for high-temperature solid two-phase anaerobic fermentation of biologically pretreated straw mixed with livestock manure as claimed in claim 5, characterized in that: The methane phase anaerobic fermentation uses dehydrated sludge as inoculum, and the inoculum amount is 30-50% of the mass of the material entering the methane phase anaerobic fermentation. After adding the inoculum, the solid content of the overall fermentation material is adjusted to 20%-25%.

7. The method for high temperature solid two-phase anaerobic fermentation of biologically pretreated straw mixed with livestock manure according to any one of claims 1 to 6, characterized in that: The biological agent is mixed with straw for pretreatment at room temperature. The amount of dry matter of the biological agent added is 0.1%-0.5% of the dry matter mass of the straw, and the pretreatment time is 4-14 days.

8. The method for high temperature solid two-phase anaerobic fermentation of biologically pretreated straw mixed with livestock manure as claimed in claim 7, characterized in that: When the moisture content of straw is 60-70%, ventilation is carried out at an air volume of 0.03-0.06 L / h per kg of straw during pretreatment.

9. The method for high-temperature solid two-phase anaerobic fermentation of biologically pretreated straw mixed with livestock manure as claimed in claim 7, characterized in that: Crush crop straw to 3-10cm.

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