阅读说明：本技术 一种利用秸秆冻融循环预处理提高秸秆厌氧发酵沼气产率的方法 (Method for improving biogas yield of straw anaerobic fermentation by using straw freeze-thaw cycle pretreatment ) 是由 裴占江 刘杰 李鹏飞 史风梅 王粟 于秋月 张文静 于 2021-05-18 设计创作，主要内容包括：本发明涉及秸秆发酵技术领域,公开了利用秸秆冻融循环预处理提高秸秆厌氧发酵沼气产率的方法,包括以下步骤：1)将秸秆粉碎至1-3cm长度；2)用水浸泡秸秆；3)将浸泡后的秸秆密封,防止风化；4)在平均温度-20至-35℃及以下环境中,将秸秆静置冻胀8-15天；5)将完成冻胀处理的秸秆解冻；以及6)将冻融循环预处理后的秸秆混合均匀,以发酵料液总体积计,加入活性厌氧菌种,并以发酵料液总重量计,加水将秸秆干物质(TS)含量调整为不高于8％后,并将发酵料液pH值调节至6-8,进行中温联合厌氧发酵。与未经冻融循环预处理的秸秆厌氧发酵产沼气相比,本发明的方法能够显著缩短厌氧消化的发酵周期,产气效率明显提高。(The invention relates to the technical field of straw fermentation, and discloses a method for improving the yield of straw anaerobic fermentation biogas by using straw freeze-thaw cycle pretreatment, which comprises the following steps: 1) crushing the straws to 1-3cm in length; 2) soaking the straws in water; 3) sealing the soaked straws to prevent weathering; 4) standing and frost-swelling the straws for 8-15 days in an environment with the average temperature of-20 to-35 ℃ and below; 5) unfreezing the frozen and swelled straws; and 6) uniformly mixing the straws subjected to freeze-thaw cycle pretreatment, adding an active anaerobic strain according to the total volume of the fermentation liquid, adding water according to the total weight of the fermentation liquid to adjust the content of dry matters (TS) of the straws to be not higher than 8%, adjusting the pH value of the fermentation liquid to 6-8, and performing medium-temperature combined anaerobic fermentation. Compared with the method for producing the biogas by the anaerobic fermentation of the straws which are not subjected to freeze-thaw cycle pretreatment, the method provided by the invention can obviously shorten the fermentation period of anaerobic digestion and obviously improve the biogas production efficiency.)

1. A method for improving the yield of straw anaerobic fermentation biogas by using straw freeze-thaw cycle pretreatment is characterized by comprising the following steps:

1) crushing the straws to 1-3cm in length;

2) soaking the straws in water;

3) sealing the soaked straws to prevent weathering;

4) standing and frost-swelling the straws for 8-15 days in an environment with the average temperature of-20 to-35 ℃ and below;

5) unfreezing the frozen and swelled straws; and

6) uniformly mixing straws subjected to freeze-thaw cycle pretreatment, adding active anaerobic bacteria according to the total volume of a fermentation liquid, adding water according to the total weight of the fermentation liquid to adjust the dry matter (TS) content of the straws to be not higher than 8%, adjusting the pH value of the fermentation liquid to 6-8, and performing medium-temperature combined anaerobic fermentation.

2. The method for improving the biogas yield of straw anaerobic fermentation by using freeze-thaw cycle pretreatment of straw according to claim 1, wherein in step 2), the mass ratio of water to dry matter (TS) of straw is 1:5-30, preferably 1:10, more preferably 1:15, and most preferably 1: 20.

3. The method for improving the yield of the straw anaerobic fermentation biogas by utilizing the freeze-thaw cycle pretreatment of the straw as claimed in claim 1, wherein in the step 4), the straw is kept still and frozen for 15 days in an environment with an average temperature of-20 ℃ and below; preferably, standing and frost-swelling the straws for 10 days in an environment with the average temperature of-30 ℃ and below; more preferably, the straw is kept still and is frozen for 8 days in an environment with the average temperature of-35 ℃ and below.

4. The method for improving the yield of the straw anaerobic fermentation biogas by utilizing freeze-thaw cycle pretreatment of the straw as claimed in claim 1, wherein in the step 6), the amount of the active anaerobic bacteria is 30-50% based on the total volume of the fermentation liquid.

5. The method for improving the yield of the straw anaerobic fermentation biogas by using freeze-thaw cycle pretreatment of the straw as claimed in claim 1, wherein the temperature during the fermentation in step 6) is 30-35 ℃.

6. The method for improving the yield of the biogas generated by the anaerobic fermentation of the straws by utilizing the freeze-thaw cycle pretreatment of the straws as claimed in claim 6, wherein in the step 6), 40% of the active anaerobic bacteria is added based on the total volume of the fermentation liquid, and after the dry matter (TS) content of the straws is adjusted to 8% by adding water based on the total weight of the fermentation liquid, the pH value of the fermentation liquid is adjusted to 7.0, so as to perform the combined anaerobic fermentation.

7. The method for improving the yield of the straw anaerobic fermentation biogas by utilizing freeze-thaw cycle pretreatment of the straw as claimed in claim 1, wherein the concentration of the dry matter (TS) of the corn straw is 8% under the condition of 35 ℃, and the biogas slurry containing abundant anaerobic microbial flora with high activity is obtained after anaerobic fermentation normally produces the biogas for 30 days.

8. The method for improving the yield of the biogas generated by the anaerobic fermentation of the straws by using the freeze-thaw cycle pretreatment of the straws as claimed in any one of claims 1 to 7, wherein the method can shorten the fermentation period by at least 30 days compared with the straws which are not pretreated by the freeze-thaw cycle.

9. The method for improving the biogas yield of straw anaerobic fermentation by using freeze-thaw cycle pretreatment of straw according to any one of claims 1-7, wherein the method can improve the biogas yield by at least 48% compared to straw not pretreated by freeze-thaw cycle.

10. The method for improving the yield of the straw anaerobic fermentation biogas by using freeze-thaw cycling pretreatment of the straw according to claim 1, wherein the straw is corn straw, wheat straw, rice straw or a combination thereof.

Technical Field

The invention relates to the technical field of straw anaerobic fermentation, in particular to a method for improving the yield of biogas generated by straw anaerobic fermentation.

Background

Lignocellulosic biomass, represented by crop straw, can exhibit lignin inhibition during anaerobic fermentation. The main mechanisms of lignin inhibition include two points: form a physical shield to prevent access of the hydrolytic enzyme and make use of its own hydrophobicity to cause ineffective adsorption with the hydrolytic enzyme. The two inhibition approaches of lignin have synergistic effect in the anaerobic fermentation process, which jointly causes the problem of low anaerobic conversion efficiency of the lignocellulose biomass.

Pretreatment of the substrate prior to anaerobic fermentation is considered an effective means of breaking lignin inhibition. The current common substrate pretreatment methods include physical pretreatment (steam explosion, mechanical grinding and crushing, etc.), chemical pretreatment (acid and alkali pretreatment), and biological pretreatment (white rot fungi pretreatment). The pretreatment methods can destroy the physical barrier of lignin to a certain extent, and the aim of improving the yield of anaerobic fermentation biogas is fulfilled. However, the implementation of existing physical, chemical and biological pretreatment technologies causes problems of increased engineering cost and secondary pollution.

Therefore, methods for improving the yield of biogas by straw anaerobic fermentation, which overcome lignin inhibition, are urgently needed in the art.

Disclosure of Invention

In view of the above, the present invention aims to provide an environment-friendly method for performing freeze-thaw cycle pretreatment on straws to overcome lignin inhibition and improve the yield of anaerobic straw fermentation biogas, thereby solving the technical problem of reducing the biogas yield due to lignin inhibition in the existing straw fermentation, effectively alleviating the harm caused by lignin inhibition and the problem of secondary pollution in the prior art, and simultaneously considering both economy and feasibility.

The object of the present invention and the solution of the technical problem can be achieved by the following technical solutions.

The invention provides a method for improving the yield of straw anaerobic fermentation biogas by using straw freeze-thaw cycle pretreatment, which comprises the following steps:

1) crushing the straws to 1-3cm in length;

2) soaking the straws in water;

3) sealing the soaked straws to prevent weathering;

4) standing and frost-swelling the straws for 8-15 days in an environment with the average temperature of-20 to-35 ℃ and below;

5) unfreezing the frozen and swelled straws; and

6) uniformly mixing the straws subjected to freeze-thaw cycle pretreatment, adding active anaerobic bacteria according to the total volume of the fermentation liquid, adding water according to the total weight of the fermentation liquid to adjust the dry matter (TS) content of the straws to be not higher than 8%, adjusting the pH value of the fermentation liquid to 6-8, and performing medium-temperature combined anaerobic fermentation.

The object of the present invention and the solution of the technical problem thereof can also be achieved by the following embodiments.

In the method for improving the yield of the straw anaerobic fermentation biogas by using the straw freeze-thaw cycle pretreatment, the mass ratio of water to straw dry matter (TS) is 1: 5-30. In a particular embodiment, the mass ratio of water to straw dry matter (TS) is 1:10, preferably 1:15, more preferably 1: 20.

In the method for improving the yield of the anaerobic fermentation biogas of the straws by using freeze-thaw cycle pretreatment of the straws, in the step 4), the straws are kept stand and frozen for 15 days at the average temperature of-20 ℃ and below; preferably, standing and frost-swelling the straws for 10 days in an environment with the average temperature of-30 ℃ and below; more preferably, the straw is kept still and is frozen for 8 days in an environment with the average temperature of-35 ℃ and below.

In the method for improving the yield of the straw anaerobic fermentation biogas by using freeze-thaw cycle pretreatment of the straw, in the step 6), the amount of the active anaerobic strain is 30-50% based on the total volume of the fermentation feed liquid.

In the method for improving the yield of the straw anaerobic fermentation biogas by using the freeze-thaw cycle pretreatment of the straw, the temperature during fermentation is 30-35 ℃ in the step 6).

In the method for improving the yield of the straw anaerobic fermentation biogas by using the freeze-thaw cycle pretreatment of the straw, the pH value is adjusted to 7 in the step 6).

In the method for improving the yield of the straw anaerobic fermentation biogas by utilizing the freeze-thaw cycle pretreatment of the straw, 40 percent of active anaerobic strains are added in the step 6) based on the total volume of the fermentation feed liquid.

In the method for improving the yield of the straw anaerobic fermentation biogas by using the freeze-thaw cycle pretreatment of the straw, water is added to dilute the straw until the content of dry matter (TS) in the straw is 8%, and then the combined anaerobic fermentation is performed.

In the method for improving the yield of the straw anaerobic fermentation biogas by utilizing freeze-thaw cycle pretreatment of the straw, 40% of the active anaerobic strain is added in step 6) based on the total volume of the fermentation feed liquid, water is added in the fermentation feed liquid based on the total weight of the fermentation feed liquid to adjust the content of dry matter (TS) of the straw to 8%, and the pH value of the fermentation feed liquid is adjusted to 7.0, and then the combined anaerobic fermentation is carried out.

In the method for improving the yield of the straw anaerobic fermentation biogas by using freeze-thaw cycle pretreatment of the straw, in the step 6), the concentration of the dry matter (TS) of the corn straw is 8% under the condition of 35 ℃ of active anaerobic bacteria, and the biogas slurry containing abundant anaerobic microbial flora with high activity is obtained after anaerobic fermentation normally produces the biogas for 30 days.

In the method for improving the yield of the anaerobic fermentation biogas of the straws by using the freeze-thaw cycle pretreatment of the straws, compared with the straws which are not subjected to the freeze-thaw cycle pretreatment, the method can shorten the fermentation period by at least 30 days.

In the method for improving the yield of the anaerobic fermentation biogas of the straws by using the freeze-thaw cycle pretreatment of the straws, compared with the straws which are not subjected to the freeze-thaw cycle pretreatment, the method can improve the yield of the biogas by at least 48%.

Compared with the prior art, the method has the following advantages: according to the method, the straw is subjected to freeze-thaw cycle pretreatment to overcome lignin inhibition, so that the yield of the straw anaerobic fermentation biogas is improved, and after the crop straw is subjected to multiple freeze-thaw cycles, the volume of moisture in straw cells expands, so that the physical structure of the straw is damaged, the physical shielding effect of lignin is relieved, and the problem of secondary pollution in the prior art is solved; on the other hand, after multiple times of freeze thawing, the hydrophobicity of the lignin macromolecules is reduced, and the ineffective adsorption inhibition of lignin on hydrolase is effectively eliminated. The method reduces the inhibiting effect of lignin in the anaerobic fermentation process, shortens the fermentation period, improves the methane yield, and is an economically and technically feasible pretreatment mode.

Drawings

FIG. 1 shows a test set-up (10L jar as fermentation device +10L jar as gas collection device +5000mL cylinder for measuring biogas production) used in an embodiment of the process of the present invention.

Detailed Description

The technical solutions of the present invention will be clearly and completely described below in connection with specific embodiments, but it should be understood by those skilled in the art that the embodiments described below are only for illustrating the present invention and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a method for improving the yield of straw anaerobic fermentation biogas by using straw freeze-thaw cycle pretreatment, which comprises the following steps:

1) crushing the straws to 1-3cm in length;

2) soaking the straws in water;

3) sealing the soaked straws to prevent weathering;

4) standing and frost-swelling the straws for 8-15 days in an environment with the average temperature of-20 to-35 ℃ and below;

5) unfreezing the frozen and swelled straws; and

6) uniformly mixing the straws subjected to freeze-thaw cycle pretreatment, adding 30-40% of the active anaerobic strain based on the total volume of the fermentation liquid, adding water based on the total weight of the fermentation liquid to adjust the content of dry matters (TS) of the straws to be not higher than 8%, adjusting the pH value of the fermentation liquid to 6-8, and performing medium-temperature combined anaerobic fermentation.

In embodiments of the method of the invention, the straw may be corn stover, rice stover, wheat straw, or the like, or a mixture thereof.

In one embodiment of the invention, in order to increase the water absorption and freeze-thaw effect of the straw, the straw may be crushed to a length of 1-3cm, for example crushed to 1cm, 1.5cm, 2.0cm, 2.5cm, 3cm, and any value in between any two values, for example 1.2cm, 1.3cm, etc. The straw can fully absorb moisture when being soaked in water after being crushed.

In an embodiment of the invention, the mass ratio of water to dry matter of straw (TS) during soaking may be between 1 and 5-25. In particular embodiments, the mass ratio of water to straw is 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:6, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, preferably 1:10, more preferably 1:15, most preferably 1: 20. The soaking time may be 2-3 days, such as 2 days, 2.5 days, or 3 days, to ensure that the straw absorbs moisture sufficiently.

In embodiments of the invention, during standing frost heave of straw, standing frost heave may be performed in an ultra-low temperature refrigerator. In a specific embodiment of the invention, resting and frost heaving are carried out in an MDF-U32V ultra-low temperature refrigerator. In another embodiment of the invention, the resting frost heaving may be performed using natural conditions, such as using the natural climate in the winter season, such as in the northeast region, thereby saving energy.

The standing frost heave time is affected by the temperature during standing frost heave, generally the lower the average temperature, the less the standing frost heave time. Therefore, in the embodiment of the invention, the straws are kept still and are frozen for 15 days in the environment with the average temperature of-20 ℃ and below; preferably, standing and frost-swelling the straws for 10 days in an environment with the average temperature of-30 ℃ and below; more preferably, the straw is kept still and is frozen for 8 days in an environment with the average temperature of-35 ℃ and below.

In the embodiment of the present invention, the thawing of the straw after the standing and frost heaving treatment may be performed under natural conditions of 0 ℃ or higher, or may be performed by heating. In a preferred embodiment of the present invention, the thawing is performed by natural conditions of 0 ℃ or more, thereby achieving the purpose of saving energy. In a further preferred embodiment of the invention, thawing is carried out for 3 to 6 days under natural conditions at 20 ℃ to 30 ℃.

In an embodiment of the invention, the pH of the pretreated straw is typically between 5 and 7. In order to fully perform anaerobic fermentation and provide biogas yield, the straw materials should be uniformly mixed during anaerobic fermentation, and the pH value of the straw materials should be adjusted to 6-8. In a particular embodiment of the invention, in step 6), the straw pH is adjusted to 6, 6.5, 7, 7.5, 8, and values between any two values, e.g. 6.2, 6.4, 7.4, 7.6, 7.7, 7.8, 7.9.

In the embodiment of the invention, the active anaerobic strain is the biogas slurry which contains rich anaerobic microbial flora with higher activity and has the concentration of corn straw dry matter (TS) of 8% under the condition of 35 ℃, and is subjected to anaerobic fermentation for 30 days after normal gas production. The active anaerobic strain contains a large amount of active methanogenic flora, and after the active anaerobic strain is added into a system, the number and the activity of the effective methanogenic flora can be rapidly improved, the starting time can be greatly shortened, and the gas production efficiency is greatly improved.

In the embodiment of the invention, in order to remove large-particle substances which are difficult to degrade, such as stones, sands, lignin and the like in the active strain, the active anaerobic strain can be screened by a 40-mesh sieve.

In the embodiment of the invention, the fermentation liquid refers to a mixture of straws, water and active anaerobic bacteria. In the step 6), 30-50% of active anaerobic strain is added based on the total volume of the fermentation liquid. In a specific embodiment of the present invention, the amount of the active anaerobic species added may be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% of the total volume of the fermentation liquor.

In an embodiment of the invention, the straw dry matter (TS) content is adjusted to not more than 8% by adding water, based on the total weight of the fermentation broth, after the addition of the active anaerobic bacteria species. In a specific embodiment of the present invention, the dry matter (TS) content of the straw may be adjusted to 5%, 5.5%, 6%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 8%, preferably the dry matter (TS) content of the straw is adjusted to 8%.

In embodiments of the invention, the method of the invention is capable of shortening the fermentation period by at least 30 days, for example, 31 days, 32 days, 33 days, 34 days, 35 days, 36 days and more, under the same conditions as compared to straw that has not been pretreated by a freeze-thaw cycle.

In embodiments of the invention, the method of the invention is capable of increasing the biogas yield by at least 48%, such as by 48%, 48.5%, 49%, 49.5%, 50%, 51%, 51.5%, 52%, 52.5%, 53%, 54, 5%, 55%, 55.5%, 56%, 56.5%, 57%, 57.5%, 58%, 58.5%, 59%, 59.5%, 60% and above, under the same conditions as compared to straw that has not been pretreated by a freeze-thaw cycle.

Without being bound by theory, it is believed that after multiple freeze-thaw cycles of crop straw, the intracellular moisture volume expands, thereby destroying the physical structure of the straw and mitigating the physical barrier effect of lignin during anaerobic fermentation. On the other hand, after multiple times of freeze thawing, the hydrophobicity of the lignin macromolecules is reduced, and the invalid adsorption limit of lignin on hydrolytic enzyme is effectively removed, so that the yield of the straw anaerobic fermentation biogas is improved, and the fermentation period is shortened.

Preferred embodiments of the present invention will be described in detail with reference to the following examples. It is to be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the present invention. Various modifications and substitutions may be made by those skilled in the art without departing from the spirit and scope of the invention, and all such modifications and substitutions are intended to be within the scope of the claims.

The experimental procedures used in the following examples are all conventional procedures unless otherwise specified. Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

Example 1

In this embodiment, a method for improving straw anaerobic fermentation biogas yield by overcoming lignin inhibition through corn straw freeze-thaw cycle pretreatment is provided, which includes the following steps:

step one, crushing dried corn straws to 1-3cm, and soaking for 2-3 days according to the mass ratio of water to the dry matter (TS) of the corn straws of 1:10 to ensure that the corn straws fully absorb water;

step two, putting the soaked corn straws into an easy-sealing bag to prevent weathering;

step three, standing and frost-swelling the straws for 15 days in an ultralow temperature refrigerator of MDF-U32V in an environment with the average temperature of-20 ℃ and below;

transferring the frozen and swelled corn straws to a pretreatment room, and naturally thawing at 20 ℃ for 6 days;

and step five, weighing about 6g of 3 parts of corn straws subjected to freeze-thaw cycle pretreatment, and measuring the dry matter (TS) and VS (volatile solid) contents of the corn straws by using a high-temperature drying box and a muffle furnace. Weighing 240g (calculated by TS) of freeze-thaw cycle pretreated corn straws, adding 1200mL of active anaerobic strain (30%) which passes through 40 meshes, adding water to dilute to 4000mL (calculated by the specific gravity of 1 of water and calculated by the total mass), adjusting the pH value to 6.5, and performing medium-temperature (35 ℃) anaerobic fermentation, wherein the content of dry matters (TS) of the corn straws in the fermentation liquid is 6%.

In addition, 240g (in TS) of untreated corn stover was weighed, 1200mL of 40 mesh-screened active anaerobic bacteria was added, diluted to 4000mL with water, pH adjusted to 6.5, and subjected to mesophilic (35 ℃) anaerobic fermentation at a dry matter (TS) content of 6% in the corn stover as a Control (CK).

This experiment adopted 10L wide-necked bottle as fermenting installation, adopted 10L wide-necked bottle as the gas collection device, adopted 5000mL graduated flask to measure marsh gas output (see figure 1). The methane yield is measured by a saturated salt solution discharging method.

146000mL of biogas is co-produced in 60 days by the method of pre-treatment and re-fermentation, and the amount of biogas produced by untreated Control (CK) is 98000 mL. Therefore, compared with CK, the method of the embodiment 1 improves the biogas yield by 48.98% after the freeze-thaw cycle pretreatment; when the treatment is carried out, the yield of methane is 48000mL more than that of CK, and the yield still needs 30 days to reach 48000mL according to the average yield of CK of 1600mL/d, so that the gas production fermentation period can be shortened by 30 days.

Example 2

In this embodiment, another method for improving the yield of biogas by straw anaerobic fermentation by overcoming lignin inhibition through freeze-thaw cycling pretreatment of corn straws is provided, which comprises the following steps:

step one, crushing dried corn straws to 1-3cm, and soaking for 2-3 days according to the mass ratio of water to the dry matter (TS) of the corn straws of 1:15 to ensure that the corn straws fully absorb water;

step two, putting the soaked corn straws into an easy-sealing bag to prevent weathering;

thirdly, standing and frost heaving the straws for 10 days in an environment with the average temperature of-25 ℃ in winter and below by using the northeast climate condition;

transferring the frozen and swelled corn straws to a pretreatment room, and naturally thawing at 24 ℃ for 5 days;

weighing about 6g of 3 parts of freeze-thaw cycle pretreated corn straws, and measuring the dry matter (TS) and volatile solid content (VS) contents of the corn straws by using a high-temperature drying box and a muffle furnace. Weighing 280g (calculated by TS) of pretreated corn straws, adding 1600mL of active anaerobic strain (40%) which passes through 40 meshes, adding water to dilute to 4000mL, adjusting the pH value to be neutral (pH7.0), and carrying out medium-temperature (35 ℃) anaerobic fermentation, wherein the content of the dry matter (TS) of the corn straws is 7%.

Additionally, 280g (calculated by TS) of untreated corn stalks are weighed, 1600mL of active anaerobic strain which passes through 40 meshes is added, water is added for dilution to 4000mL, the pH value is adjusted to be neutral (pH7.0), medium temperature (35 ℃) anaerobic fermentation is carried out, and the content of dry matter (TS) of the corn stalks is 7 percent and is used as a Control (CK).

This experiment adopted 10L wide-necked bottle as fermenting installation, adopted 10L wide-necked bottle as the gas collection device, adopted 5000mL graduated flask to measure marsh gas output (see figure 1). The methane yield is measured by a saturated salt solution discharging method.

The method for re-fermenting after pretreatment produces 154000mL of biogas in 60 days, and the biogas production amount of untreated Control (CK) is 99850 mL. Therefore, compared with the control, the method in the embodiment 2 improves the biogas yield by 54.23%, the treatment yield is 54150mL more than CK, and the gas yield can still reach 54150mL within 32 days according to the CK average gas yield of 1664mL/d, so the gas production fermentation period can be shortened by 32 days.

Example 3

The embodiment provides another method for improving the yield of the straw anaerobic fermentation biogas by overcoming lignin inhibition through freeze-thaw cycle pretreatment of corn straws, which comprises the following steps:

step one, crushing dried corn straws to 1-3cm, and soaking for 2-3 days according to the ratio of water amount to the mass (TS) of the corn straws of 1:20 to ensure that the corn straws fully absorb water;

step two, putting the soaked corn straws into an easy-sealing bag to prevent weathering;

step three, standing and frost heaving the corn straws for 8 days in an environment with the average temperature of-35 ℃ and below;

transferring the frozen and swelled corn straws to a pretreatment room, and naturally thawing at 30 ℃ for 3 days;

weighing about 6g of 3 parts of freeze-thaw cycle pretreated corn straws, and measuring the dry matter (TS) and Volatile Solid (VS) contents of the corn straws by using a high-temperature drying box and a muffle furnace. Weighing 320g (calculated by TS) of pretreated corn straws, adding 2000mL of active anaerobic strain (50%) which passes through 40 meshes, adding water to dilute to 4000mL, adjusting the pH value to 7.5, and performing medium-temperature (35 ℃) anaerobic fermentation, wherein the content of the dry matter (TS) of the corn straws is 8%; weighing 320g (calculated by TS) of untreated corn stalks, adding 2000mL of active anaerobic strain (50%) which passes through 40 meshes, adding water to dilute to 4000mL, adjusting the pH value to 7.5, and carrying out medium temperature (35 ℃) anaerobic fermentation, wherein the content of dry matter (TS) of the corn stalks is 8% and the Control (CK) is used.

This experiment adopted 10L wide-necked bottle as fermenting installation, adopted 10L wide-necked bottle as the gas collection device, adopted 5000mL graduated flask to measure marsh gas output (see figure 1). The methane yield is measured by a saturated salt solution discharging method.

The method for re-fermenting after pretreatment produces 166400mL of biogas in 60 days, and the amount of untreated biogas is 100860 mL. Therefore, compared with the control, the method in the embodiment 3 improves the biogas yield by 64.98%, the treatment amount of the biogas is 65540mL more than CK, and the biogas production amount still needs 39d to reach 65540mL according to the average gas production amount of CK 1681mL/d, so that the biogas production fermentation period can be shortened by 39 days.

Example 4

The embodiment provides another method for improving the yield of the straw anaerobic fermentation biogas by overcoming lignin inhibition through freeze-thaw cycle pretreatment of rice straws, which comprises the following steps:

crushing dried rice straws to 1-3cm, and soaking for 2-3 days according to the mass ratio of water to dry rice straw (TS) of 1:10 to ensure that the rice straws fully absorb water;

step two, putting the soaked rice straws into an easy-sealing bag to prevent weathering;

step three, standing and frost heaving the rice straws for 15 days in an environment with the average temperature of-20 ℃ and below;

step four, transferring the rice straws subjected to the frost heaving treatment to a pretreatment room, and naturally thawing at 20 ℃ for 6 days;

and step five, weighing about 6g of the rice straws subjected to freeze-thaw cycle pretreatment by 3 parts, and measuring the dry matter (TS) and Volatile Solid (VS) contents of the rice straws by using a high-temperature drying box and a muffle furnace. Weighing 320g (calculated by TS) of pretreated rice straw, adding 1600mL of active anaerobic strain (40%) which passes through 40 meshes, adding water to dilute to 4000mL, adjusting the pH value to be neutral (pH7.0), and performing medium-temperature (35 ℃) anaerobic fermentation, wherein the content of dry matter (TS) of the rice straw is 8%; weighing 320g (calculated by TS) of untreated rice straws, adding 1600mL of active anaerobic strain passing through 40 meshes, adding water to dilute to 4000mL, adjusting the pH value to be neutral (pH7.0), and carrying out medium temperature (35 ℃) anaerobic fermentation, wherein the content of dry matter (TS) of the rice straws is 8% and the Control (CK) is used.

This experiment adopted 10L wide-necked bottle as fermenting installation, adopted 10L wide-necked bottle as the gas collection device, adopted 5000mL graduated flask to measure marsh gas output (see figure 1). The methane yield is measured by a saturated salt solution discharging method.

The method for re-fermenting after pretreatment produces 144400mL of biogas in 60 days, and the amount of untreated biogas is 96860 mL. Therefore, compared with the control, the method in the example 4 improves the biogas yield by 49.08%, the treatment rate is 47540mL more biogas production than CK, and the average gas production rate of CK is 1614mL/d, and the gas production rate still needs 30 days to reach 47540mL, so the gas production fermentation period can be shortened by 30 days.

Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.