CN112795597B

CN112795597B - Method for promoting straw rapid hydrolysis by domesticating paddy soil

Info

Publication number: CN112795597B
Application number: CN202110147205.2A
Authority: CN
Inventors: 刘玉环; 王晶晶; 罗璇; 王允圃; 晏琛; 向书玉; 刘童莹; 张琦; 曹雷鹏; 巫小丹; 彭红; 郑洪立
Original assignee: Nanchang University
Current assignee: Nanchang University
Priority date: 2021-02-03
Filing date: 2021-02-03
Publication date: 2023-05-30
Anticipated expiration: 2041-02-03
Also published as: CN112795597A

Abstract

The invention discloses a method for domesticating paddy soil to promote straw rapid hydrolysis, which is characterized in that straw and fecal sewage are used for domesticating paddy soil microorganisms, inducing the formation of various straw decomposition complex bacteria, and effectively enhancing the enzymatic activity of soil, wherein the paddy soil plays the dual roles of bacterial nests and extracellular enzyme immobilization carriers secreted by the microorganisms. Then taking domesticated rice soil as an inexpensive inoculant, inoculating the straw, immersing the straw in liquid manure, keeping a micro-oxygen state, and further hydrolyzing into smaller fragments or cellulose oligomer, hemicellulose oligomer and reducing sugar; and (3) after stirring and preliminary sedimentation, separating out liquid substances and fine organic substance particles in the straw manure mixture, transferring the liquid substances and the fine organic substance particles into an acidification tank containing rich acetobacter and butyric acid bacillus, maintaining low dissolved oxygen and high reaction temperature, and promoting the comprehensive and high-efficiency conversion of the organic substances into acetic acid or butyric acid. Provides rich organic acid raw materials for producing methane by continuous, stable and efficient anaerobic fermentation of a methane tank.

Description

Method for promoting straw rapid hydrolysis by domesticating paddy soil

Technical Field

The invention relates to a method for domesticating paddy field soil to promote straw rapid hydrolysis, belongs to the field of agricultural resources and environmental science, and is a key applicable technical innovation for efficiently producing biogas, high-quality biogas residues, biogas slurry and organic fertilizer by straw-manure combined fermentation.

Background

With the rapid development of intensive breeding industry, the environmental pollution problem caused by the rapid development of livestock and poultry breeding industry is increasingly serious, and according to the statistics of the department of agriculture in 2016, the livestock and poultry breeding waste produced in China per year reaches 38 hundred million tons, and the most effective method for recycling the feces is anaerobic fermentation at present. However, the problems of low carbon nitrogen ratio, low gas production efficiency, serious ammonia inhibition and the like exist in the anaerobic fermentation process of the excrement, and the co-fermentation of the straw and the excrement is the best solution.

China is the country where the straw is the largest, the annual yield reaches more than 8 hundred million tons, but a large amount of straw is not reasonably utilized or disposed. The straw is burned unordered, so that not only is energy and nutrient wasted, but also serious environmental pollution is caused. The fermentation of straw to produce biogas is the most effective way to date to obtain biomass energy. However, most of the straws are lignocellulose with a highly complex supermolecular structure and are formed by compounding three components of cellulose, hemicellulose and lignin (see table 1). A large number of siliceous protective cells are also present in part of the grass crop stalks, and therefore are difficult to be rapidly decomposed by microorganisms in a short time. To solve this problem, various methods of pretreatment of straw have been employed, including physical pretreatment, chemical pretreatment and microbial pretreatment. The chemical pretreatment method has the problems of high cost and easy environmental pollution.

Table 1: lignocellulose content of wheat straw, corn straw and rice straw

Published chinese invention patent: the method for improving the yield of the anaerobic digestion biogas of the straw by the solid normal-temperature treatment of sodium hydroxide (CN 1814762A) comprises the steps of fully and uniformly mixing a sodium hydroxide solution with a certain concentration with crushed straw, mixing the mixture into a wet state, and then placing the wet state in a container for sealing and preserving, wherein the method promotes the decomposition of lignin in the straw, but still generates great impact on the normal long term in an anaerobic fermentation tank after the direct input into the anaerobic fermentation tank, so that the efficiency of converting the straw into the biogas is improved only to a limited extent;

published chinese invention patent: the method for improving the methane yield of the straw by pure ammonia wet soaking pretreatment at normal temperature (publication number: CN 102827879A) comprises the steps of firstly placing chopped straw into a sealed bag, evacuating air in the bag, uniformly mixing ammonia water and water, and pouring the mixture into the sealed bag; the addition amount of ammonia water is 2% -6% of the dry weight of straw measured by pure ammonia; the total mass of water in the ammonia water and water contained in the straw is 30% -90% of the dry weight of the straw, the straw is preserved in an environment of 25 ℃ -35 ℃ for 90-110 hours, and then the straw is added into an anaerobic fermentation reactor, and the method is not suitable for the condition of co-fermentation of straw manure, and a large amount of ammonia gas can exacerbate the ammonia inhibition problem.

Published chinese invention patent: a method for improving anaerobic digestion gas production performance of straw stalk by combining pretreatment of calcium oxide and biogas slurry (publication number: CN 108384813A) comprises dissolving calcium oxide accounting for 6% -12% of dry weight of stalk in a mixture of stalk and biogas slurry, standing for 1-4 days, and adding pig manure anaerobic fermentation tank inoculum for medium-temperature anaerobic digestion for 40-60d. The method is not beneficial to the efficient utilization of lime, and simultaneously ignores the difference between microorganisms in an anaerobic stage and microorganisms in a straw hydrolysis acidification stage.

Compared with physical and chemical methods, the microbial pretreatment has the characteristics of mild condition, low cost, no environmental pollution and the like. In the initial stage of the pretreatment study of microorganisms, most researchers have isolated and screened lignocellulose degrading bacteria in a pure culture method. However, complete degradation of lignocellulose is the result of the combined action of fungi, bacteria, actinomycetes and corresponding microbial communities, so that a single strain has problems in maintaining cellulolytic capacity. In recent years, many studies have been attempted on the use of complex bacteria for the treatment of lignocellulose in order to achieve rapid degradation, but so far, there are few truly rapid and effective biological methods applied to anaerobic biogas pretreatment.

Disclosure of Invention

The technical problems solved by the invention are as follows: aiming at the defects of the prior art, the method for promoting the rapid hydrolysis of the straw by domesticating the rice field soil is provided, the microbial cells of the rice field soil are domesticated, the formation of various straw decomposition complex bacterial groups is induced, the activity of soil enzyme is effectively enhanced, meanwhile, the rice soil plays the roles of bacterial nests and microbial extracellular enzyme immobilized carriers, the activity of polyphenol oxidase is further enhanced by abundant low-price manganese elements in the reductive rice soil, the decomposition of lignin is accelerated, the decomposition conversion and the recycling utilization of the straw are effectively improved, and the method is low in cost, simple to operate, low in running cost, clean and pollution-free.

In order to solve the technical problems, the invention adopts the following technical scheme:

step 1, mixing 100-500 parts by weight of straw and manure (prepared according to the requirement of a carbon-nitrogen ratio of 25:1) with 1000-5000 parts by weight of rice field soil, maintaining a 1-2cm flooded layer, naturally drying after 1-2 days, and carrying out secondary rehydration after the water content of the soil surface layer is reduced to 50% -60%, repeating for 3-4 times, domesticating rice field soil microorganisms, inducing the formation of various straw decomposition complex bacterial groups and effectively enhancing the activity of soil enzymes, wherein the rice soil plays a role of a bacterial nest and a microorganism extracellular enzyme immobilization carrier. In order to stabilize the activity of soil flora and the activity of soil enzymes, straw and fecal substrate are repeatedly added every two months, the quantity of which is one tenth of the first addition quantity.

Taking 100 parts of air-dried straw, taking the rice soil domesticated in the step 1 as an inexpensive inoculant, wherein the inoculum size is 1% -100% (in a water saturation state), inoculating the straw for 12-96 hours, keeping the dissolved oxygen content in a water layer of 1-2cm for 6-8mg/L during the inoculation treatment, taking out and draining, transferring the straw into a plastic tank, controlling the water evaporation rate, providing sufficient air, keeping the temperature of 20-40 ℃ and fermenting for 24-96 hours under a light-shielding condition, and after the surface of the straw is completely colonised by microorganisms with rich diversity, disintegrating the complex structure of lignocellulose. If the conditions allow, spraying 80-120 parts of lime water to 100 parts of air-dried straw, wherein the lime water comprises quicklime (kg): water (L) =1: 8, uniformly mixing, compacting and diffusing for 6-24 hours, and then inoculating the domesticated paddy soil.

And 3, immersing 50-100 parts by weight of the straw with loose structure obtained in the step 2 into a reaction container filled with 100-200 parts by weight of liquid manure, continuously maintaining micro-oxygen (dissolved oxygen amount is 3-9 mg/L) and a light-shielding state, and promoting the straw to be further hydrolyzed into fragments with the thickness of less than 0.1mm or into cellulose oligomer, hemicellulose oligomer, amino acid and reducing sugar.

And 4, stirring and preliminary settling the container in the step 3, separating out liquid substances in the straw manure mixture and fine organic substance particles dispersed in the liquid substances, transferring the liquid substances into an acidification tank containing rich acetobacter and butyric acid bacillus, and maintaining low dissolved oxygen (1-6 mg/L) and a reaction temperature of 40-60 ℃ to promote the comprehensive and high-efficiency conversion of the organic substances into acetic acid or butyric acid. And the settled substances are returned to the paddy field soil domestication pond to maintain the diversity of paddy field soil microorganisms and strong soil enzyme activity.

And 5, filtering the liquid organic acid obtained in the step 4 in an anaerobic mode, continuously and slowly inputting the liquid organic acid into a methane tank with a large volume (the hydraulic retention time is based on 20-30 days) according to a dilution multiple of more than 1/16-20 under an anaerobic condition, and carrying out efficient and stable anaerobic fermentation to produce methane. The filter residue is retained in the acidification tank as a source of acidifying species.

The invention is based on long-term natural selection, a large number of microorganisms which can decompose lignocellulose, including bacteria, fungi and actinomycetes exist in paddy field soil, straw can be rapidly degraded in paddy field soil with proper C/N ratio, and bacterial strains rich in hydrolytic straw are obtained by directionally inducing and domesticating the paddy field soil with the straw-manure as a substrate and the carbon nitrogen ratio of 25:1, wherein the bacterial strains comprise 25.7% of bacterioides (bacteroides, firmicutes (armigera), 20.9% of Proteobacteria (Proteobacteria), 12.4% of chloroflexyi (Lloydig) and the like, and the bacterial nest effect of the paddy field soil serving as microorganisms is utilized, so that the action of multi-bacterial synergism in straw degradation is enhanced; the solid components of the soil are utilized to play the role of a microorganism extracellular enzyme immobilization carrier, and the activities of cellulase, catalase and laccase in the domesticated rice soil are obviously improved through measurement; meanwhile, the existence of manganese and copper ions in the strong reducing environment of the paddy soil plays a positive role in improving the activity of the catalase and laccase, and promotes the degradation of straw lignin.

The invention improves the hydrolysis rate of the straw is a key technology for producing methane by co-fermenting straw and livestock pollution, utilizes straw and manure as substrates to domesticate rice field soil microorganisms as cheap inoculums to hydrolyze the straw, and then the microorganisms quickly colonize the surface of the straw (the straw with serious siliceous as lime water pretreatment can be carried out when the condition allows), secrete extracellular enzymes to promote the disintegration of the straw to produce smaller fragments or cellulose oligomers, hemicellulose oligomers, reducing sugar and the like, thereby providing cheap organic acid raw materials for subsequent acidification and continuous and stable three-stage anaerobic fermentation methane production system with continuous high buffering.

Compared with the prior art, the invention has the advantages that:

1. the method has simplicity, innovation, is a tight combination of practicality and scientificity, and uses the domesticated rice field soil as an inoculant for straw hydrolysis to be directly effective, so that the method has the advantages of low production cost, simplicity in operation, low running cost and no pollution;

2. according to the invention, straw and manure are used as substrates to perform substrate induction domestication on paddy soil, and straw decomposition compound flora inducing diversity is enriched by taking soil substances as bacterial nests; the rice soil also plays a role of a microorganism extracellular enzyme immobilization carrier, so that the soil enzyme activity is effectively enhanced; the rich manganese element and trace copper element brought by the excrement in the rice soil with strong reducibility further strengthen the activities of catalase and laccase for decomposing lignin;

3. when the technology is adopted, the straw can be not pretreated, but a small amount of lime water can be adopted to treat the straw with developed siliconized cells, such as straw, if the condition allows, so that the siliconized cells are destroyed, and the physical barrier is further reduced.

Drawings

FIG. 1 is a schematic diagram showing the microbial community structure of paddy soil before and after acclimatization in example 1.

FIG. 2 is a schematic representation of cellulase activity in paddy soil before and after acclimatization in example 1.

FIG. 3 is a schematic diagram showing the increase of Total Organic Carbon (TOC) produced by the acclimatized rice field soil inoculation treatment.

Fig. 4 is a schematic diagram showing the improvement of lignocellulose degradation effect of the domesticated rice field soil inoculated with the straw.

Fig. 5 is a schematic diagram showing the increase of the total organic acid amount generated by the acidification reaction of the liquid product and the fine organic particles generated by the domestication of three straws and the inoculation treatment of the paddy soil.

Fig. 6 is a schematic diagram showing that the total amount of methane produced by the methanogenesis reaction of liquid organic acid produced by the domesticated rice field soil inoculation treatment is improved compared with the conventional one-step direct investment.

Detailed Description

The invention will be further described with reference to specific examples and figures.

Example 1: rice soil which is induced and domesticated by straw and pig manure is used as an inexpensive inoculant for promoting straw hydrolysis.

Step 1, preparing a mixture according to the requirement of a carbon-nitrogen ratio of 25:1 by air-drying straw (cut into about 5cm long) +pig manure (water content of 80 percent);

and 2, mixing 100 parts by weight of the mixture of the rice straw and the pig manure in the step 1 with 1000 parts by weight of rice field soil, maintaining a 2cm flooded layer, naturally falling to dryness after 2 days, repeating the process for 4 times after the water content of the soil surface layer is reduced to 60%, domesticating rice field soil microorganisms, and maintaining the 2cm flooded layer after the domestication is finished and maintaining the dissolved oxygen content of a water layer to be 6-8mg/L. Inducing the formation of various straw decomposition complex bacterial groups and effectively enhancing the activity of soil enzymes, wherein rice soil plays roles of bacterial nests and microbial extracellular enzyme immobilized carriers, and the reduction property formed by organic decomposition increases low-valence manganese elements in the rice soil and causes manure to bring into trace copper ions in the soil;

step 3, the time for carrying out the induction and domestication of the rice field soil substrate is generally selected in summer and autumn, and straw and pig manure waste are repeatedly added once every two months for stabilizing the activity of soil flora and soil enzyme, wherein the quantity of the straw and pig manure waste is one tenth of the first addition quantity;

and 4, collecting the domesticated paddy field soil to determine the soil cellulase activity, extracting DNA for high-throughput sequencing, and changing the soil cellulase activity and the microbial community structure, wherein the results are shown in figures 1 and 2.

As can be seen from FIG. 1, firmics, chloroflex, proteobacteria and Bactoides are distributed more uniformly in the microorganisms of paddy soil acclimatized by straw and manure than in the comparative example. Firmics, chloroflex, proteobacteria and Bactoides are considered to be the main mycorrhizas responsible for hydrolysis, and can produce extracellular enzymes to metabolize substrates, break down cellulose and polysaccharide in the substrates, and effectively participate in the hydrolysis stage. Oceanihabdus and terrisporobacteria in Firmics play an important role in the biodegradation of organic substances in the hydrolysis stage. Metagenome in Chloroflexi plays an effective role in the degradation of butyrate and refractory organics in the substrate. Simplicispira and Aquamicrobium in Proteibacteria are facultative and obligate heterotrophic bacteria that reduce sulfate and degrade propionate, butyrate and monosaccharides; and utilizes long chain fatty acids and amino acids. Lentimibe in Bactoidetes is an important organic heterotrophic bacterium involved in the recovery of organic carbon and protein materials. In Firmics, chloroflexi, proteobacteria and Bactoidetes can effectively destroy the straw and degrade lignin thereof under the synergistic effect, and the accessibility of the straw to the enzymolysis of microbial extracellular enzymes is improved.

As can be seen from FIG. 2, the cellulase activity of the domesticated paddy soil was improved by 3.6 times as compared with that of the control example. The rice soil plays a role of a microbial extracellular enzyme immobilized carrier, and lays a foundation for the subsequent hydrolysis of cellulose in the straw.

Example 2: the rice field soil domesticated in the example 1 is used as an inoculant to promote the rapid hydrolysis of the rice straw after lime water pretreatment.

Step 1, spraying 80-120 parts of lime water (quicklime (kg): water (L) =1:8) on 100 parts of straw, uniformly mixing, compacting and diffusing for 6-24 hours for later use;

step 2, taking domesticated rice soil in the embodiment 1 as an inexpensive inoculant, wherein the inoculum size is 60% (the water is in a saturated state), inoculating the rice straw obtained after lime water treatment in the embodiment 1 for 96 hours, keeping the dissolved oxygen content in a 2cm water layer at 6mg/L during the period, and fishing out and draining for later use;

step 3, draining off the rice straw obtained in the step 2 for standby, transferring the rice straw into a plastic tank, controlling the water evaporation speed, providing sufficient oxygen, keeping the temperature at 35 ℃ and fermenting for 72 hours in a dark condition, and after the surface of the rice straw is completely colonised by various rich microorganisms, disintegrating the complex structure of lignocellulose;

and 4, immersing 50 parts by weight of the straw with loose structure obtained in the step 3 into a reaction vessel filled with 200 parts by weight of liquid manure, continuously maintaining a micro-oxygen (dissolved oxygen amount of 4 mg/L) and a light-shielding state, and promoting the straw to be further hydrolyzed into fragments with the thickness of less than 0.1mm or into cellulose oligomer, hemicellulose oligomer, amino acid and reducing sugar.

And 5, stirring and preliminary settling the container in the step 4, separating out liquid substances in the straw manure mixture and fine organic substance particles dispersed in the liquid substances, transferring the liquid substances into an acidification tank containing rich acetobacter and butyric acid bacillus, and maintaining the low dissolved oxygen (4 mg/L) and the reaction temperature of 50 ℃ to promote the comprehensive and high-efficiency conversion of the organic substances into acetic acid or butyric acid. The settled substances are returned to the paddy field soil domestication pond to maintain the diversity and strong soil enzyme activity of the domesticated paddy field soil microorganisms;

and 6, filtering the liquid organic acid obtained in the step 5 in an anaerobic mode, continuously and slowly inputting the liquid organic acid into a large-volume (the hydraulic retention time is based on 25 days) biogas tank according to a dilution multiple of 1/20 under an anaerobic condition (the dissolved oxygen amount is close to zero), and carrying out efficient and stable anaerobic fermentation to produce methane. The filter residue corresponding to one tenth of the volume of the acidification tank is reserved in the acidification tank as a source of acidifying bacteria.

Example 3: the domesticated rice field soil in the example 1 is used as an inoculant to promote the rapid hydrolysis of sorghum stalks.

Step 1, taking 100 parts by weight of air-dried sorghum straw, taking domesticated rice soil as an inexpensive inoculant in the embodiment 1, wherein the inoculum size is 100% (the water is in a saturated state), inoculating the sorghum straw for 96 hours, keeping the dissolved oxygen in a water layer of 1.5cm at 8mg/L during the period, and fishing out and draining for later use;

step 2, draining the sorghum straw obtained in the step 1 for standby, transferring the sorghum straw into a plastic tank, controlling the water evaporation speed, providing sufficient oxygen, keeping the temperature at 36 ℃ and fermenting for 96 hours in a dark condition, and after the surface of the sorghum straw is completely colonised by various rich microorganisms, disintegrating the complex structure of lignocellulose;

and 3, immersing 100 parts by weight of the sorghum straw with loose structure obtained in the step 2 into a reaction vessel filled with 200 parts by weight of liquid manure, continuously maintaining a micro-oxygen (dissolved oxygen amount of 5 mg/L) and a light-shielding state, and promoting the sorghum straw to be further hydrolyzed into fragments with the thickness of less than 0.1mm or into cellulose oligomer, hemicellulose oligomer, amino acid and reducing sugar.

And 4, stirring and preliminary settling the container in the step 3, separating out liquid substances and dispersed fine organic substance particles in the sorghum straw fecal sewage mixture, transferring the mixture into an acidification tank containing rich acetobacter and butyric acid bacillus, and maintaining low dissolved oxygen (2.5 mg/L) and a reaction temperature of 55 ℃ to promote the comprehensive and high-efficiency conversion of organic substances into acetic acid or butyric acid. And the settled substances are returned to the paddy field to maintain the diversity and strong soil enzyme activity of the domesticated paddy field soil microorganisms;

and 5, filtering the liquid organic acid obtained in the step 4 in an anaerobic mode, continuously and slowly inputting the liquid organic acid into a large-volume (the hydraulic retention time is based on 25 days) biogas tank according to a dilution multiple of 1/18 under an anaerobic condition (the dissolved oxygen amount is close to zero), and carrying out efficient and stable anaerobic fermentation to produce methane. The filter residue corresponding to one tenth of the volume of the acidification tank is reserved in the acidification tank as a source of acidifying bacteria.

Example 4: the rice soil is used as an inexpensive inoculant for promoting the hydrolysis of wheat straw by inducing and domesticating the wheat straw and chicken manure.

Step 1, preparing a mixture according to the requirement of a carbon-nitrogen ratio of 25:1 by air-drying wheat straw (cutting into about 5cm long) +chicken manure (water content of 100 percent);

and 2, mixing 100 parts by weight of the mixture of the wheat straw and the chicken manure in the step 1 with 2000 parts by weight of rice field soil, keeping a 1.8cm flooded layer, naturally falling to dryness after 2 days, carrying out secondary rehydration after the water content of the soil surface layer is reduced to 70%, repeating for 4 times, domesticating rice field soil microorganisms, keeping a 1.5cm flooded layer after the domestication is finished, and keeping the dissolved oxygen of the water layer at 6.5mg/L. Inducing the formation of various wheat straw decomposition complex flora and effectively enhancing the activity of soil enzymes, wherein rice soil plays roles of a bacterial nest and a microbial extracellular enzyme immobilized carrier, and the reducing property formed by organic matter decomposition increases low-valence manganese elements in the rice field soil and causes manure to bring into trace copper ions in the soil;

step 3, the induction and domestication time of the rice field soil substrate is generally selected in summer and autumn, and in order to stabilize the activity of soil flora and soil enzyme activity, wheat straw and chicken manure substrate are repeatedly added once every two months, wherein the quantity of the wheat straw and chicken manure substrate is one tenth of the first adding quantity;

example 5: the domesticated rice field soil of example 4 is used as an inoculant to promote the rapid hydrolysis of wheat straw.

Step 1, taking 100 parts by weight of air-dried wheat straw, taking domesticated rice soil as an inexpensive inoculant in the embodiment 4, wherein the inoculation amount is 100% (the water is in a saturated state), inoculating the wheat straw for 72 hours, keeping the dissolved oxygen amount in a water layer of 1.2cm at 7.5mg/L during the period, and fishing out and draining for later use;

step 2, draining the wheat straw obtained in the step 1 for standby, transferring the wheat straw into a plastic tank, controlling the water evaporation speed, providing sufficient oxygen, keeping the temperature at 32 ℃ and fermenting for 72 hours in a dark condition, and after the surface of the wheat straw is completely colonised by various rich microorganisms, disintegrating the complex structure of lignocellulose;

and 3, immersing 100 parts by weight of the wheat straw with loose structure obtained in the step 2 into a reaction container filled with 200 parts by weight of liquid chicken manure, continuously maintaining micro-oxygen (dissolved oxygen amount is 3.8 mg/L) and a light-shielding state, and promoting the wheat straw to be further hydrolyzed into fragments with the thickness of less than 0.1mm or hydrolyzed into cellulose oligomer, hemicellulose oligomer, amino acid and reducing sugar.

And 4, stirring and preliminary settling the container in the step 3, separating out liquid substances and dispersed fine organic substance particles in the wheat straw manure mixture, transferring the liquid substances and the dispersed fine organic substance particles into an acidification tank containing rich acetobacter and butyric acid bacillus, and maintaining low dissolved oxygen (3 mg/L) and 52 ℃ reaction temperature to promote the comprehensive and high-efficiency conversion of organic substances into acetic acid or butyric acid. The settled substances are returned to the paddy field soil domestication pond to maintain the diversity and strong soil enzyme activity of the domesticated paddy field soil microorganisms;

and 5, filtering the liquid organic acid obtained in the step 4 in an anaerobic mode, continuously and slowly inputting the liquid organic acid into a large-volume (the hydraulic retention time is based on 25 days) biogas tank according to a dilution multiple of 1/19 under an anaerobic condition (the dissolved oxygen amount is close to zero), and carrying out efficient and stable anaerobic fermentation to produce methane. The filter residue corresponding to one tenth of the volume of the acidification tank is reserved in the acidification tank as a source of acidifying bacteria.

Example 6: the corn stalk and cow dung-induced domesticated rice soil is used as cheap inoculant for promoting corn stalk hydrolysis.

Step 1, preparing a mixture according to the requirement of a carbon-nitrogen ratio of 25:1 by air-drying corn straw (cutting into about 5cm long) +dairy cow manure (the water content is 100 percent);

and 2, mixing 100 parts by weight of the mixture of the corn straw and the dairy cow manure in the step 1 with 3000 parts by weight of rice field soil, keeping a 2cm flooded layer, naturally falling to dryness after 2 days, repeating the process for 4 times after the water content of the soil surface layer is reduced to 65%, domesticating rice field soil microorganisms, and keeping the 2cm flooded layer after the domestication is finished and keeping the dissolved oxygen content of a water layer to be 8mg/L. Inducing the formation of various corn straw decomposition complex bacterial groups and effectively enhancing the activity of soil enzymes, wherein rice soil plays roles of bacterial nests and microbial extracellular enzyme immobilized carriers, and the reducing property formed by organic matter decomposition increases low-valence manganese elements in the rice soil and causes manure to bring into trace copper ions in the soil;

step 3, the time for carrying out the induction and domestication of the rice field soil substrate is generally selected in summer and autumn, and corn straw and dairy cow manure substrate are repeatedly added every two months for stabilizing the activity of soil flora and soil enzyme, wherein the quantity of the corn straw and dairy cow manure substrate is one tenth of the first adding quantity;

example 7: the domesticated paddy field soil in the example 6 is used as an inoculant to promote the rapid hydrolysis of corn stalks.

Step 1, taking 100 parts by weight of air-dried corn stalks, taking domesticated rice soil as an inexpensive inoculant in the embodiment 5, wherein the inoculation amount is 100% (the water is in a saturated state), inoculating the corn stalks for 72 hours, keeping the dissolved oxygen amount in a water layer of 1.2cm at 7.5mg/L during the inoculation treatment, and fishing out and draining for later use;

step 2, draining the corn straw obtained in the step 1 for standby, transferring the corn straw into a plastic tank, controlling the water evaporation speed, providing sufficient oxygen, keeping the temperature of 34 ℃ and fermenting for 96 hours under a light-shielding condition, and after the surface of the corn straw is completely colonised by various rich microorganisms, disintegrating the complex structure of lignocellulose;

and 3, immersing 100 parts by weight of the maize straw with loose structure obtained in the step 2 into a reaction container filled with 200 parts by weight of liquid dairy manure, continuously maintaining micro-oxygen (dissolved oxygen amount is 3.8 mg/L) and a light-shielding state, and promoting the maize straw to be further hydrolyzed into fragments with the thickness of less than 0.1mm or into cellulose oligomer, hemicellulose oligomer, amino acid and reducing sugar.

And 4, stirring and preliminary settling the container in the step 3, separating out liquid substances and dispersed fine organic substance particles in the corn straw milk cow dung mixture, transferring the mixture into an acidification tank containing rich acetobacter and butyric acid bacillus, and maintaining low dissolved oxygen (3 mg/L) and 52 ℃ reaction temperature to promote the comprehensive and high-efficiency conversion of the organic substances into acetic acid or butyric acid. The settled substances are returned to the paddy field soil domestication pond to maintain the diversity and strong soil enzyme activity of the domesticated paddy field soil microorganisms;

The foregoing description of the preferred embodiments of the present invention has been presented only in terms of those specific and detailed descriptions, and is not, therefore, to be construed as limiting the scope of the invention. It should be noted that modifications, improvements and substitutions can be made by those skilled in the art without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims

1. The method for promoting the rapid hydrolysis of the straw by domesticating the paddy soil is characterized by comprising the following steps:

step 1, mixing 100-500 parts by weight of straw and manure with 1000-5000 parts by weight of rice field soil, keeping a 1-2cm flooded layer, naturally falling to dryness after 1-2 days, repeating the steps for 3-4 times when the water content of the soil surface layer is reduced to 50% -60%, and domesticating rice field soil microorganisms, wherein the number of straw and manure substrates is one tenth of the number of the first addition;

step 2, taking 100 parts of air-dried straw, taking the rice soil domesticated in the step 1 as an inoculum, wherein the inoculum size is 1% -100%, inoculating the straw for 12-96 hours, keeping the dissolved oxygen in a water layer of 1-2cm for 6-8mg/L, fishing out and draining, transferring the straw into a plastic tank, controlling the water evaporation rate, providing sufficient air, keeping the temperature of 20-40 ℃ and fermenting for 24-96 hours in a light-shielding condition;

step 3, immersing 50-100 parts by weight of the straw with loose structure obtained in the step 2 into a reaction container filled with 100-200 parts by weight of liquid manure, and continuously keeping a micro-oxygen and light-shielding state, wherein the dissolved oxygen amount of the micro-oxygen is 3-9mg/L; hydrolyzing the straw into fragments with the diameter of less than 0.1mm or into cellulose oligomer, hemicellulose oligomer, amino acid and reducing sugar;

step 4, stirring and preliminary settling the container in the step 3, separating out liquid substances in the straw manure mixture and fine organic substance particles dispersed in the liquid substances, transferring the liquid substances into an acidification tank containing rich acetobacter and butyric acid bacillus, and keeping the low dissolved oxygen and the reaction temperature of 40-60 ℃, wherein the low dissolved oxygen is 1-6mg/L; converting the organic matters into acetic acid or butyric acid, and returning the settled matters to a paddy field soil domestication pond;

step 5, filtering the liquid organic acid obtained in the step 4 in an anaerobic mode, continuously and slowly inputting the liquid organic acid into a large-volume methane tank according to a dilution multiple of more than 1/16-20 under an anaerobic condition, and carrying out efficient and stable anaerobic fermentation to produce methane, wherein filter residues are reserved in an acidification tank and serve as sources of acidification strains; the hydraulic retention time is 20-30 days.