阅读说明：本技术 厌氧干发酵好氧发酵-厌氧发酵处理干秸秆产沼气的方法 (Method for producing biogas by treating dry straws through anaerobic dry fermentation and aerobic fermentation-anaerobic fermentation ) 是由 赵玉晓 李希越 华栋梁 陈雷 许海朋 李岩 梁晓辉 谢新苹 于 2020-12-24 设计创作，主要内容包括：一种厌氧干发酵-好氧发酵厌氧发酵处理干秸秆产沼气的方法,包括步骤如下：(1)将粉碎后干秸秆与厌氧污泥混合进行厌氧干发酵预处理3-5天,将秸秆中易利用可溶性糖、纤维素等物质转化为沼气,收集沼气；(2)将厌氧干发酵后秸秆加入好氧混合微生物,调节含水率40-50%,好氧环境下进行好氧发酵预处理1-3天,降解或转化秸秆中木质素释放纤维素、半纤维素,同时将秸秆中难利用纤维素、半纤维素转化为易利用物质,减少纤维素、半纤维素向二氧化碳转化带来的原料损失；(3)将好氧发酵后秸秆加入厌氧污泥进行厌氧发酵,将纤维素、半纤维素和其转化产物转化为沼气,收集沼气。(A method for producing biogas by treating dry straws through anaerobic dry fermentation-aerobic fermentation anaerobic fermentation comprises the following steps: (1) mixing the crushed dry straws with anaerobic sludge for anaerobic dry fermentation pretreatment for 3-5 days, converting substances such as soluble sugar and cellulose which are easy to utilize in the straws into biogas, and collecting the biogas; (2) adding aerobic mixed microorganisms into the straws subjected to anaerobic dry fermentation, adjusting the water content to 40-50%, performing aerobic fermentation pretreatment for 1-3 days in an aerobic environment, degrading or converting lignin in the straws to release cellulose and hemicellulose, and simultaneously converting the cellulose and the hemicellulose which are difficult to utilize in the straws into substances which are easy to utilize, so that the raw material loss caused by the conversion of the cellulose and the hemicellulose into carbon dioxide is reduced; (3) and adding the aerobic fermented straws into anaerobic sludge for anaerobic fermentation, converting cellulose, hemicellulose and conversion products thereof into biogas, and collecting the biogas.)

1. A method for producing biogas by treating dry straws through anaerobic dry fermentation, aerobic fermentation and anaerobic fermentation is characterized by comprising the following steps: (1) dry straw anaerobic dry fermentation pretreatment: crushing dry straws by a straw crusher, inoculating anaerobic sludge into the crushed dry straws in a straw dry anaerobic fermentor for anaerobic dry fermentation, controlling the fermentation time to convert substances such as soluble sugar and cellulose which are easy to utilize in the straws into biogas, and enabling the biogas to enter a biogas collection tank; anaerobic sludge used for anaerobic dry fermentation is anaerobic sludge domesticated by straw anaerobic fermentation, and the inoculation amount is 10-30% of the dry weight of the straw; the anaerobic dry fermentation temperature is 30-40 ℃, the fermentation time is 3-5 days, and the solid content is 60% -85%;

(2) aerobic fermentation pretreatment: dry straws after anaerobic dry fermentation are loaded into an aerobic fermentor with the functions of water content regulation and pile turning through a belt conveyor, aerobic mixed microorganisms are inoculated, the water content is regulated to be 40-50%, the oxygen concentration of a pile is controlled to be 10-20% through regular pile turning, aerobic fermentation pretreatment is carried out in the aerobic compost device, lignin in the converted straws is degraded to release cellulose and hemicellulose, meanwhile, the cellulose and the hemicellulose which are difficult to utilize in the straws are converted into substances which are easy to utilize, the raw material loss brought by conversion to carbon dioxide is reduced, and the fermentation time is 1-3 days; aerobic mixed microorganisms used in the aerobic fermentation pretreatment contain bacillus, actinomycetes and trichoderma to prepare bacterial liquid for use, the effective viable count of the bacterial liquid per milliliter is more than 100 hundred million units, and the inoculation amount of the aerobic microorganisms is 0.1 to 0.25 percent of the bacterial liquid per kilogram of dry straws;

(3) anaerobic fermentation to produce methane: the straws after aerobic fermentation are loaded into an anaerobic fermentation tank through a screw conveyor to be inoculated with anaerobic sludge for anaerobic fermentation, cellulose, hemicellulose and conversion products thereof in the straws are converted into biogas, and the biogas enters a biogas collection tank; the anaerobic sludge used for anaerobic fermentation is anaerobic sludge domesticated by straw anaerobic fermentation, the inoculation amount is 10-30% of the dry weight of the straw, the anaerobic fermentation temperature is 30-40 ℃, and the fermentation time is 15-20 days.

2. The method for producing biogas by treating dry straws through anaerobic dry fermentation, aerobic fermentation and anaerobic fermentation according to claim 1, wherein the dry straws comprise corn straws, wheat straws and rice straws, and are naturally air-dried, and the water content is lower than 10%.

3. The method for producing biogas by treating dry straws through anaerobic dry fermentation, aerobic fermentation and anaerobic fermentation according to claim 1, wherein the dry straws are crushed by a straw crusher and the length of the crushed pieces is 1-4 cm.

Technical Field

The invention belongs to the technical field of organic waste treatment and resource utilization, and particularly relates to a method for producing biogas by treating dry straws through anaerobic dry fermentation, aerobic fermentation and anaerobic fermentation.

Background

The straw mainly comprises lignin, cellulose and hemicellulose. A three-dimensional cross-linking structure formed by cross-linking lignin, cellulose and hemicellulose together through covalent bonds and hydrogen bonds has a shielding effect on cellulose degradation, and the direct anaerobic fermentation of straws to produce biogas has low efficiency due to the crystalline structure of the cellulose and the wrapping effect of the hemicellulose on the cellulose. The key technical problem of producing the methane by the anaerobic fermentation of the straws is to remove the degradation barrier of the lignocellulose and improve the energy conversion efficiency of the lignocellulose.

The aerobic fermentation is one of the important methods for the pretreatment of producing the biogas by the anaerobic fermentation of the straws, and has the advantages of low energy consumption, low investment cost, high resource utilization efficiency and the like. However, the aerobic fermentation still has the problems of difficult control, large raw material loss caused by conversion to carbon dioxide, unobvious effect of promoting methane production and the like in the practical application, and even the phenomenon of reducing the methane yield. Most of the existing solutions are to screen lignin-degrading bacteria with high selectivity.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method for producing biogas by treating dry straws through anaerobic dry fermentation and aerobic fermentation and anaerobic fermentation in a combined manner.

In order to solve the technical problems, the invention adopts the following technical scheme: a method for producing biogas by treating dry straws through anaerobic dry fermentation, aerobic fermentation and anaerobic fermentation comprises the following steps: (1) dry straw anaerobic dry fermentation pretreatment: crushing dry straws by a straw crusher, inoculating anaerobic sludge into the crushed dry straws in a straw dry anaerobic fermentor to perform anaerobic dry fermentation pretreatment, controlling the fermentation time to convert substances such as soluble sugar and cellulose which are easy to utilize in the straws into biogas, and enabling the biogas to enter a biogas collection tank; the anaerobic sludge used for the anaerobic dry fermentation is anaerobic sludge domesticated by straw anaerobic fermentation, and the inoculation amount is 10-30% of the dry weight of the straw. The anaerobic dry fermentation temperature is 30-40 ℃, the fermentation time is 3-5 days, and the solid content is 60-85%.

(2) Aerobic fermentation pretreatment: loading the dry straws subjected to anaerobic dry fermentation pretreatment into an aerobic fermentor with the functions of water content regulation and pile turning through a belt conveyor, inoculating aerobic mixed microorganisms, regulating the water content to 40-50%, controlling the oxygen concentration of a pile body to 10% -20% through regular pile turning, performing aerobic fermentation pretreatment in the aerobic compost device, degrading and converting lignin in the straws to release cellulose and hemicellulose, simultaneously converting the cellulose and the hemicellulose which are difficult to be utilized into substances which are easy to be utilized, and reducing the raw material loss brought by conversion to carbon dioxide; the aerobic mixed microorganism used in the aerobic fermentation pretreatment contains bacillus, actinomycetes and trichoderma to prepare bacterial liquid for use, the effective viable count of the bacterial liquid per milliliter is more than 100 hundred million units, and the inoculation amount of the aerobic microorganism is 0.1 to 0.25 percent of the bacterial liquid per kilogram of dry straws.

In some embodiments of the invention, the oxygen concentration in the aerobic fermentation pretreatment pile is controlled to be 10-20%, the water content of the pile is controlled to be 40-50%, and the treatment time is 1-3 days.

(3) Anaerobic fermentation to produce methane: and (3) filling the straws subjected to aerobic fermentation pretreatment into an anaerobic fermentation tank through a screw conveyor to inoculate anaerobic sludge for anaerobic fermentation, converting cellulose, hemicellulose and conversion products thereof in the straws into biogas, and feeding the biogas into a biogas collection tank. The anaerobic sludge used for anaerobic fermentation is anaerobic sludge domesticated by straw anaerobic fermentation, the inoculation amount is 10-30% of the dry weight of the straw, the anaerobic fermentation temperature is 30-40 ℃, and the fermentation time is 15-20 days.

The scheme is characterized in that the dry straws comprise corn straws, wheat straws and rice straw straws, and are naturally air-dried, and the water content is lower than 10%. The length of the fragments of the dry straws is 1-4 cm after the dry straws are crushed by a straw crusher.

The invention has the following beneficial effects: the characteristics of the straw raw material cause that the selective degradation of lignin is difficult to realize in the aerobic fermentation pretreatment process, mainly comprising the fermentation of mixed microorganisms, wherein the mixed microorganisms remove lignocellulose degradation barriers and simultaneously convert micromolecular organic matters such as saccharides, fat, protein and the like and easily-contacted cellulose into carbon dioxide, so that the raw material loss is caused, and the efficiency of producing methane by subsequent anaerobic fermentation is influenced. The invention adopts anaerobic dry fermentation and aerobic fermentation to combine the pretreatment of dry straws, and carries out anaerobic fermentation on the treated dry straws to produce the biogas. Soluble sugar, cellulose and other substances which are easy to utilize are converted into methane by controlling the anaerobic dry fermentation time, so that the raw material loss caused by subsequent aerobic fermentation is reduced, and the total yield of the dry straw anaerobic fermentation methane is improved. By controlling the water content and time of aerobic fermentation, the conversion of lignin degrading bacteria to carbon dioxide from cellulose, hemicellulose and the like is reduced, the destructive effect on lignocellulose degradation-resistant barriers is improved, the raw material loss during aerobic fermentation pretreatment is further reduced, and the total yield of dry straw anaerobic fermentation biogas is improved.

The method for producing the biogas by treating the dry straws through the combination of the anaerobic dry fermentation, the aerobic fermentation and the anaerobic fermentation reduces the loss of raw materials of the aerobic fermentation pretreatment, improves the destructive effect of a lignocellulose degradation-resistant barrier, improves the methane yield accumulated in unit solid by more than 20 percent compared with the biogas produced by treating the dry straws through the combination of the aerobic fermentation pretreatment and the anaerobic fermentation, and improves the methane yield accumulated in unit solid by more than 50 percent compared with the biogas produced by directly treating the dry straws through the anaerobic fermentation.

Aerobic fermentation pretreatment adopts aerobic mixed microorganisms containing common compost bacteria, namely bacillus, actinomycetes and trichoderma, so that the applicability of the technology is improved, and the treatment cost is reduced compared with aerobic pretreatment by using lignin-degrading bacteria selectively.

The water content is controlled to be 40-50% by aerobic fermentation pretreatment, the conversion of lignin degrading bacteria to carbon dioxide of cellulose, hemicellulose and the like in the straws is reduced, the damage effect on a lignocellulose degradation-resistant barrier is improved, the loss of raw materials is reduced from more than 10% to less than 6%, and therefore the total yield of dry straw anaerobic fermentation biogas is improved.

Drawings

FIG. 1 is a flow chart of the process of producing biogas by treating dry straws through anaerobic dry fermentation and aerobic fermentation in a combined manner.

In the figure: 1-a straw crusher; 2-straw dry anaerobic fermentor; 3-an aerobic fermenter; 4-anaerobic fermentation tank; and 5, a biogas collection tank.

Detailed Description

Example 1: a method for producing biogas by treating dry straws through anaerobic dry fermentation and aerobic fermentation and anaerobic fermentation comprises the following steps: (1) dry straw anaerobic dry fermentation: 100g of dry corn straws are crushed into pieces with the length of 2cm, and anaerobic dry fermentation is carried out in a straw dry anaerobic fermentor. Inoculating 30% of straw dry weight of anaerobic sludge domesticated by straw anaerobic fermentation, fermenting at 35 deg.C for 4 days, adding water, spraying to adjust solid content to 75%, and collecting biogas.

The anaerobic sludge is taken from a stably-operated straw biogas engineering anaerobic fermentation tank, dry straws are taken as a sole substrate at the temperature of 35 ℃, and semi-continuous operation domestication is carried out. The length of the fragments of the dry straws crushed by the straw crusher is 1-4 cm, the initial mass ratio of the sludge to the straws is 50%, the dry straws are added once every 5 days according to the concentration of volatile acid and the yield of methane, the adding amount of the dry straws is 20% of the initial dry straw amount each time, and the domestication is considered to be successful when the concentration of the volatile fatty acid and the daily yield of the methane are stable.

(2) Aerobic fermentation: and (3) loading the anaerobic dry fermented raw materials into an aerobic fermentor with the functions of adjusting the water content and turning the stack through a belt conveyor for aerobic fermentation. Adding bacterial liquid containing bacillus, actinomycetes and trichoderma in a mass ratio of 1:1:1 into 0.2% of bacterial liquid per kilogram of dry straw, adding water to spray and adjust the water content to 45% when the effective viable count of the bacterial liquid per milliliter is more than 100 hundred million units, and regularly turning the stack to keep the oxygen concentration to be more than 15%. The initial temperature of the aerobic fermentation pretreatment is 35 ℃, and the fermentation time is 2 days.

The bacillus, the actinomycetes and the trichoderma are commercially common compost bacteria, wherein the bacillus is derived from Abelia bulbophyllata/bacillus licheniformis of Shandong Bei Jia biological technology limited company, the actinomycetes is derived from Espoir actinomycetes of Luoyangxinhope biological technology limited company, the trichoderma is derived from composite trichoderma of Shandong Lvgan biological technology limited company, a bacterial solution is prepared before use, and the effective viable count of each milliliter of the bacterial solution is more than 100 hundred million units.

(3) Anaerobic fermentation to produce methane: and (3) charging the aerobically fermented raw materials into an anaerobic fermentation tank through a screw conveyor for wet anaerobic fermentation. Inoculating 30% of straw dry weight anaerobic sludge domesticated by straw anaerobic fermentation, adding water to adjust the solid content of the dry corn straw to 8%, fermenting at 35 ℃ for 18 days, and collecting biogas.

Example 2: a method for producing biogas by treating dry straws through anaerobic fermentation comprises the following steps: 100g of dry corn straws are crushed into pieces with the length of 2cm, and the pieces are loaded into an anaerobic fermentation tank through a screw conveyor for wet anaerobic fermentation. Inoculating anaerobic sludge domesticated by straw anaerobic fermentation with 60% of dry weight of the straw, adding bacterial liquid containing bacillus, actinomycetes and trichoderma (mass ratio is 1:1: 1) into 0.2% of bacterial liquid per kilogram of dry straw, adding water to adjust the solid content of the dry corn straw to be 8%, fermenting at 35 ℃ for 24 days, and collecting methane, wherein the effective viable count of the bacterial liquid per milliliter is more than 100 hundred million units.

The anaerobic sludge source and acclimation method are the same as example 1.

The sources of Bacillus, Actinomycetes and Trichoderma are the same as in example 1

Example 3: a method for producing biogas by treating dry straws through anaerobic fermentation comprises the following steps: 100g of dry corn straws are crushed into pieces with the length of 2cm, and the pieces are loaded into a straw dry anaerobic fermentation device through a screw conveyor for dry anaerobic fermentation. Inoculating anaerobic sludge domesticated by straw anaerobic fermentation with 60% of dry weight of straws, adding bacterial liquid containing bacillus, actinomycetes and trichoderma (the mass ratio is 1:1: 1) into 0.2% of bacterial liquid per kilogram of dry straws, adding water to adjust the solid content of the dry corn straws to be 75%, fermenting at the temperature of 35 ℃, fermenting for 24 days, and collecting methane, wherein the effective viable count of the bacterial liquid per milliliter is more than 100 hundred million units.

The anaerobic sludge source and acclimation method are the same as example 1.

The sources of Bacillus, Actinomycetes and Trichoderma are the same as in example 1

Example 4: a method for producing biogas by treating dry straws through aerobic fermentation-anaerobic fermentation comprises the following steps:

100g of dry corn straws are crushed into pieces with the length of 2cm, and the pieces are put into an aerobic fermentor with the functions of water content regulation and pile turning through a belt conveyor for aerobic fermentation. Adding bacterial liquid containing bacillus, actinomycetes and trichoderma in a mass ratio of 1:1:1 into 0.2% of bacterial liquid per kilogram of dry straw, adding water to spray and adjust the water content to 45% when the effective viable count of the bacterial liquid per milliliter is more than 100 hundred million units, and regularly turning the stack to keep the oxygen concentration to be more than 15%. The initial temperature of the aerobic fermentation pretreatment is 35 ℃, and the fermentation time is 2 days.

And (3) charging the aerobically fermented raw materials into an anaerobic fermentation tank through a screw conveyor for wet anaerobic fermentation. Inoculating 30% of straw dry weight of anaerobic sludge domesticated by straw anaerobic fermentation, adding water to adjust the solid content of the dry corn straw to 8%, fermenting at 35 ℃ for 22 days, and collecting biogas.

The anaerobic sludge source and acclimation method are the same as example 1.

The sources of Bacillus, Actinomycetes and Trichoderma are the same as in example 1

Example 5: a method for producing biogas by treating dry straws through aerobic fermentation-anaerobic fermentation comprises the following steps:

100g of dry corn straws are crushed into pieces with the length of 2cm, and the pieces are put into an aerobic fermentor with the functions of water content regulation and pile turning through a belt conveyor for aerobic fermentation. Adding bacterial liquid containing bacillus, actinomycetes and trichoderma in a mass ratio of 1:1:1 into 0.2% of bacterial liquid per kilogram of dry straw, adding water to spray and adjust the water content to 45% when the effective viable count of the bacterial liquid per milliliter is more than 100 hundred million units, and regularly turning the stack to keep the oxygen concentration to be more than 15%. The initial temperature of the aerobic fermentation pretreatment is 35 ℃, and the fermentation time is 2 days.

And (3) loading the aerobically fermented raw materials into a straw dry anaerobic fermentor through a screw conveyor for dry anaerobic fermentation. Inoculating 30% of straw dry weight of anaerobic sludge domesticated by straw anaerobic fermentation, adding water to adjust the solid content of the dry corn straw to 8%, fermenting at 35 ℃ for 22 days, and collecting biogas.

The anaerobic sludge source and acclimation method are the same as example 1.

The sources of Bacillus, Actinomycetes and Trichoderma are the same as in example 1

The effect of the above embodiment is:

under the condition of the same total treatment time, compared with the direct wet anaerobic fermentation treatment of the dry corn straws to produce the biogas (example 2), the anaerobic dry fermentation-aerobic fermentation-anaerobic fermentation combined treatment of the dry straws to produce the biogas (example 1) has the advantages that the unit accumulated methane yield is improved from 113ml/g-TS to 189ml/g-TS, the 67 percent is improved, and the total reduction degree of the dry straws is improved from 33 percent to 58 percent.

Under the condition of the same total treatment time, compared with the direct dry anaerobic fermentation treatment of the dry corn straws to produce the biogas (example 3), the anaerobic dry fermentation-aerobic fermentation-anaerobic fermentation combined treatment of the dry straws to produce the biogas (example 1) has the advantages that the unit accumulated methane yield is increased from 121ml/g-TS to 189ml/g-TS, the unit accumulated methane yield is increased by 56 percent, and the total reduction degree of the dry straws is increased from 37 percent to 58 percent.

Under the condition of the same total treatment time, compared with the biogas produced by treating dry corn straws through aerobic fermentation pretreatment and wet anaerobic fermentation (example 4), the biogas produced by treating dry straws through anaerobic dry fermentation, aerobic fermentation and anaerobic fermentation (example 1) is improved to 189ml/g-TS from 137ml/g-TS, which is improved by 30%, the loss of dry straw raw materials through aerobic fermentation is reduced to 4% from 13%, and the total reduction degree of the dry straws is improved to 58% from 45%.

Under the same total treatment time, compared with the aerobic fermentation pretreatment-dry anaerobic fermentation treatment of the dry corn straws to produce the biogas (example 5), the anaerobic dry fermentation-aerobic fermentation-anaerobic fermentation combined treatment of the dry straws to produce the biogas (example 1) has the advantages that the unit accumulated methane yield is increased from 152ml/g-TS to 189ml/g-TS, the yield is increased by 24 percent, the loss of aerobic fermentation raw materials is reduced from 13 percent to 4.2 percent, and the total reduction degree of the dry straws is increased from 49 percent to 58 percent.

Example 6: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the anaerobic dry fermentation time is 3 days.

Example 7: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the anaerobic dry fermentation time is 1 day, and the wet anaerobic fermentation time is 20 days.

The effect of the above embodiment is: under the condition of the same total treatment time, compared with the anaerobic dry fermentation-aerobic fermentation-anaerobic fermentation combined treatment of dry straws to produce biogas (example 7) with the anaerobic dry fermentation time of 1 day, the anaerobic dry fermentation-aerobic fermentation-anaerobic fermentation combined treatment of dry straws with the anaerobic dry fermentation time of 3 days to produce biogas (example 6) has the advantages that the unit accumulated methane yield is increased from 165ml/g-TS to 182ml/g-TS and is increased by 10%, the raw material loss after aerobic fermentation is reduced from 11% to 5.1%, and the total reduction degree of the dry straws is increased from 51% to 56%.

Example 8: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the anaerobic dry fermentation time is 5 days.

Example 9: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the anaerobic dry fermentation time is 6 days, and the wet anaerobic fermentation time is 17 days.

Example 10: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the anaerobic dry fermentation time is 8 days.

The effect of the above embodiment is: under the condition of the same total treatment time, compared with the biogas produced by the anaerobic dry fermentation-aerobic fermentation-anaerobic fermentation combined treatment of dry straws (example 9) with the anaerobic dry fermentation time of 6 days, the biogas produced by the anaerobic dry fermentation-aerobic fermentation-anaerobic fermentation combined treatment of dry straws (example 8) with the anaerobic dry fermentation time of 5 days has the advantages that the unit accumulated methane yield is increased from 171ml/g-TS to 187ml/g-TS, the unit accumulated methane yield is increased by 9 percent, and the raw material loss after the aerobic fermentation is reduced from 9 percent to 5.3 percent.

Compared with the anaerobic dry fermentation, aerobic fermentation and anaerobic fermentation combined treatment of dry straws for 8 days to produce methane (example 10), the anaerobic dry fermentation, aerobic fermentation and anaerobic fermentation combined treatment of dry straws for 5 days to produce methane (example 8) has the advantages that the unit accumulated methane yield is increased from 161ml/g-TS to 187ml/g-TS, is increased by 16%, the loss of aerobic fermentation raw materials is reduced from 16% to 5.3%, and the total treatment time is reduced from 27 days to 25 days.

Example 11: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the water content of the aerobic fermentation pretreatment is 40 percent.

Example 12: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the water content of the aerobic fermentation pretreatment is 30 percent.

The effect of the above embodiment is: compared with the method for producing the methane by the combined treatment of the anaerobic dry fermentation, the aerobic fermentation and the anaerobic fermentation with the water content of 30 percent (example 12), the method for producing the methane by the combined treatment of the anaerobic dry fermentation, the aerobic fermentation and the anaerobic fermentation with the water content of 40 percent by the aerobic fermentation (example 11) has the advantages that the unit accumulated methane yield is increased from 152ml/g-TS to 186ml/g-TS and is increased by 22 percent, the loss of aerobic fermentation raw materials is not changed greatly, and the total reduction degree of the dry straws is increased from 37 percent to 55 percent.

Example 13: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the water content of the aerobic fermentation pretreatment is 50 percent.

Example 14: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the water content of the aerobic fermentation pretreatment is 60 percent.

The effect of the above embodiment is: compared with the method for producing the methane by the anaerobic dry fermentation, the aerobic fermentation and the anaerobic fermentation combined treatment of the dry straws with the water content of 60% (example 14), the yield of the methane accumulated per unit (example 13) produced by the anaerobic dry fermentation, the aerobic fermentation and the anaerobic fermentation combined treatment of the dry straws with the water content of 50% (example 13) is improved from 162ml/g-TS to 184ml/g-TS, 13% is improved, the loss of aerobic fermentation raw materials is reduced from 10% to 4.1%, and the total reduction degree of the dry straws is reduced from 56% to 54%.

Example 15: this example is the same as example 1 and will not be described again except that the aerobic fermentation time is 1 day.

Example 16: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the aerobic fermentation time is 12 h.

The effect of the above embodiment is: compared with the method for producing the methane by the anaerobic dry fermentation, the aerobic fermentation and the anaerobic fermentation combined treatment of the dry straws (example 16) with the aerobic fermentation pretreatment time of 12 hours, the method for producing the methane by the anaerobic dry fermentation, the aerobic fermentation and the anaerobic fermentation combined treatment of the dry straws (example 15) with the aerobic fermentation pretreatment time of 1 day has the advantages that the unit accumulated methane yield is increased from 131ml/g-TS to 166ml/g-TS, the yield is increased by 26 percent, the loss of the aerobic fermentation raw materials is not changed greatly, and the total reduction degree of the dry straws is increased from 39 percent to 53 percent.

Example 17: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the aerobic fermentation time is 3 days.

Example 18: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the aerobic fermentation time is 4 days.

The effect of the above embodiment is: compared with the method for producing the biogas by the anaerobic dry fermentation, the aerobic fermentation and the anaerobic fermentation combined treatment of the dry straws (example 18) with the aerobic fermentation pretreatment time of 4 days, the method for producing the biogas by the anaerobic dry fermentation, the aerobic fermentation and the anaerobic fermentation combined treatment of the dry straws (example 17) with the aerobic fermentation pretreatment time of 3 days has the advantages that the unit accumulated methane yield is improved from 165ml/g-TS to 179ml/g-TS and is improved by 8 percent, the loss of aerobic fermentation raw materials is reduced from 12 percent to 5.7 percent, and the total reduction degree of the dry straws is reduced from 57 percent to 53 percent.

Example 19: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the anaerobic dry fermentation time is 3 days, the water content of the aerobic fermentation pretreatment is 60 percent, and the aerobic fermentation is 1 day.

The effect of this embodiment is: the unit accumulated methane yield is 179ml/g-TS, the aerobic fermentation raw material loss is 4.8 percent, and the total reduction degree of dry straws is 55 percent.

Example 20: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the anaerobic dry fermentation time is 5 days, the aerobic fermentation pretreatment water content is 40 percent, and the aerobic fermentation time is 4 days.

The effect of this embodiment is: the unit accumulated methane yield is 152ml/g-TS, the aerobic fermentation raw material loss is 12.8 percent, and the total reduction degree of dry straws is 48 percent. Compared with the embodiment 19, the anaerobic dry fermentation time is prolonged, the water content of aerobic fermentation pretreatment is reduced, the aerobic fermentation time is prolonged, the unit accumulated methane yield and the total reduction degree of dry straws cannot be improved, and the unit accumulated methane yield and the total reduction degree of dry straws are respectively reduced by 15% and 12.7%.

Example 21: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: the anaerobic dry fermentation time is 5 days, the aerobic fermentation pretreatment water content is 60 percent, and the aerobic fermentation time is 3 days.

The effect of this embodiment is: the unit accumulated methane yield is 167ml/g-TS, the loss of aerobic fermentation raw materials is 5.8 percent, and the total reduction degree of dry straws is 57 percent.

Example 22: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: crushing straws into fragments with the length of 4cm, inoculating anaerobic sludge which is 10 percent of the dry weight of the straws and is acclimated by anaerobic fermentation of the straws through anaerobic dry fermentation, and adding bacterial liquid containing bacillus and actinomycetes (the mass ratio is 6: 4) into the bacterial liquid according to 0.1 percent ml of the dry straws per kilogram through aerobic fermentation.

The effect of this embodiment is: the unit accumulated methane yield is 172ml/g-TS, the aerobic fermentation raw material loss is 5.2 percent, and the total reduction degree of dry straws is 56 percent.

Example 23: the same parts of this embodiment as embodiment 1 will not be described again, but the differences are: crushing the straws into pieces with the length of 1cm, inoculating anaerobic sludge which is 20 percent of the dry weight of the straws and is acclimated by anaerobic fermentation of the straws through anaerobic dry fermentation, and adding bacterial liquid containing bacillus and trichoderma (the mass ratio is 2: 5) into the aerobic fermentation according to 0.25 percent ml of bacterial liquid per kg of dry straws under the same conditions as in example 1, thereby not being repeated.

The effect of this embodiment is: the unit accumulated methane yield is 182ml/g-TS, the aerobic fermentation raw material loss is 5.9 percent, and the total reduction degree of dry straws is 58 percent.