Method for producing biogas through anaerobic fermentation of straw

Abstract

The invention discloses a method for producing biogas through anaerobic fermentation of straws, and belongs to the field of solid waste treatment, the method comprises the following steps: carrying out hydrothermal pretreatment on the straws to obtain a solid-liquid mixture, and carrying out anaerobic fermentation on the solid-liquid mixture by taking sludge as an inoculum to produce biogas. Straw and polylactic acid are potential high-quality fermentation substrates and are converted into biogas through anaerobic fermentation, so that the utilization rate of waste is increased, and secondary pollution to the environment is reduced.

Description

Technical Field

[0001] The invention belongs to the field of solid waste treatment and disposal, and particularly relates to a method for producing biogas through anaerobic fermentation of straw. Background Art

[0002] During the anaerobic fermentation of straw, due to the special packaging structure of lignocellulose, compact crystals are formed in space, resulting in compact straw, low porosity, poor accessibility of microorganisms and extracellular enzymes to cellulose and hemicellulose, and greatly reduced fermentation efficiency. At the same time, a new waste, polylactic acid, is introduced during the hydrothermal pretreatment of straw. It degrades slowly during anaerobic fermentation, and the degradation time takes 250 days to several years (Cucina et al., 2021). Therefore, there is an urgent need in the art for a method of producing biogas using anaerobic fermentation of straw in a short period of time without generating polylactic acid waste. Summary of the invention

[0003] The purpose of the present invention is to provide a method for producing biogas by anaerobic fermentation of straw to solve the problems existing in the above-mentioned prior art. The present invention intends to use hydrothermal technology to generate an acidic hydrothermal environment through hydrothermal treatment of polylactic acid to break and dissolve the ester-ether bonds in lignin, thereby achieving the separation of cellulose and hemicellulose, while catalyzing the hydrolysis of cellulose and hemicellulose under low temperature conditions, and promoting the subsequent anaerobic fermentation of straw to produce biogas.

[0004] One of the technical solutions:

[0005] A method for producing biogas by anaerobic fermentation of straw comprises the following steps: hydrothermally pretreating the straw to obtain a solid-liquid mixture, using sludge as inoculant, and anaerobic fermenting the solid-liquid mixture to produce biogas.

[0006] Preferably, the temperature of the hydrothermal pretreatment is 120-180°C, the time is 50-90 min, and the solid-liquid ratio of the straw to water is 1 g: 10 mL; and / or

[0007] The TS of the sludge is 9-12%, the VS is 6-8%, and the pH is 7.1-7.3; and / or

[0008] The temperature of the anaerobic fermentation is 35-39° C., the organic load is 25-35 gVS / L, and the time is 60-80 days.

[0009] More preferably, the hydrothermal pretreatment temperature is 120° C. and the time is 60 min; and / or

[0010] The TS of the sludge is 11.1%, the VS is 6.86%, and the pH is 7.52; and / or

[0011] The temperature of the anaerobic fermentation is 37±1° C., the organic load is 25-35 gVS / L, and the time is 52 days.

[0012] Technical solution 2:

[0013] A method for producing biogas by anaerobic fermentation of straw comprises the following steps: mixing straw with polylactic acid and then performing hydrothermal pretreatment to obtain a solid-liquid mixture; using sludge as inoculant, performing anaerobic fermentation on the solid-liquid mixture to produce biogas.

[0014] Preferably, the mass ratio (VS) of the straw to the polylactic acid is 1:1; and / or

[0015] The hydrothermal pretreatment temperature is 120-180°C, the time is 50-90 min, and the solid-liquid ratio of the sum of the straw and polylactic acid to water is 1 g: 10 mL; and / or

[0016] The TS of the sludge is 9-12%, the VS is 6-8%, and the pH is 7.1-7.3; and / or

[0017] The temperature of the anaerobic fermentation is 35-39° C., the organic load is 25-35 gVS / L, and the time is 60-80 days.

[0018] More preferably, the hydrothermal pretreatment temperature is 180°C and the time is 60 min; and / or

[0019] The TS of the sludge is 11.1%, the VS is 6.86%, and the pH is 7.52; and / or

[0020] The temperature of the anaerobic fermentation is 37±1° C., the organic load is 25-35 gVS / L, and the time is 60 days.

[0021] Preferably, the sludge is prepared by taming kitchen waste, and the taming parameters are: time 15 to 50 days, temperature 32 to 39° C., stirring rate 10 to 30 rpm, stirring for 5 to 10 minutes every 2 to 3 hours, and taming under nitrogen.

[0022] The present invention proposes a polylactic acid and straw synergistic hydrothermal pretreatment method, which improves the efficiency of hydrolysis acidification and biogas production in the anaerobic fermentation process, and realizes low-energy consumption, low-cost, high-efficiency green energy treatment of polylactic acid and straw biomass.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] Both straw and polylactic acid are potential high-quality fermentation substrates. They can be converted into biogas through anaerobic fermentation, which not only increases the utilization rate of waste but also reduces secondary pollution to the environment.

[0025] The polylactic acid is mixed with straw for hydrothermal pretreatment. Under the acidic hydrothermal environment formed by hydrothermal technology, it can effectively catalyze the conversion of (hemi)cellulose and the dissolution of lignin, and promote the anaerobic fermentation of straw to produce biogas. The pretreated polylactic acid and straw mixture is directly subjected to anaerobic fermentation, which avoids the loss of substrate and is simple to operate.

[0026] Polylactic acid alone degrades slowly during anaerobic fermentation and takes a long time to ferment. Hydrothermal treatment provides an acidic hydrothermal environment for the straw, which accelerates the depolymerization of lignin from cellulose and hemicellulose, increases the area of ​​cellulose and hemicellulose that anaerobic microorganisms are in contact with, and effectively shortens the fermentation time. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0028] Figure 1 Characterization diagram of hydrothermal liquid after corn stover and polylactic acid pretreatment under different hydrothermal temperature conditions in Examples 1-3 of the present invention, wherein A is soluble chemical oxygen demand (SCOD) and pH, and B is a diagram of changes in VFA content;

[0029] Figure 2 A is a comparison of the composition of lignocellulose after hydrothermal pretreatment of CS and PLA at different temperatures and CS alone at different temperatures; B is a scanning electron microscope (SEM) image of CS and PLA mixed with hydrothermal pretreatment at different temperatures and CS alone at different temperatures;

[0030] Figure 3 A is a comparison chart of the cumulative biogas yields of anaerobic fermentation in each group in Example 1, B is a comparison chart of the cumulative methane yields of anaerobic fermentation in each group in Example 1, C is a comparison chart of the cumulative biogas yields of anaerobic fermentation in each group in Example 2, D is a comparison chart of the cumulative methane yields of anaerobic fermentation in each group in Example 2, E is a comparison chart of the cumulative biogas yields of anaerobic fermentation in each group in Example 3, and F is a comparison chart of the cumulative methane yields of anaerobic fermentation in each group in Example 3. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0033] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0034] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0035] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0036] The embodiment of the present invention provides a method for producing biogas by anaerobic fermentation of straw, the steps of which are as follows:

[0037] 1) Pretreatment stage: Put polylactic acid and straw water into a hydrothermal reactor for hydrothermal pretreatment to obtain a hydrothermal solid-liquid mixture.

[0038] 2) Anaerobic biogas production stage: the solid-liquid mixture obtained in step 1) is mixed with sludge to perform anaerobic fermentation to produce biogas.

[0039] Among them, the method for obtaining the solid-liquid mixture in step 1) is: the first group is to perform hydrothermal pretreatment on the polylactic acid powder and the straw powder respectively, and then mix the obtained solid-liquid mixture to obtain an anaerobic fermentation solid-liquid mixture; the second group is to mix the polylactic acid powder and the straw powder and then perform hydrothermal pretreatment to obtain a solid-liquid mixture; the third group is to perform hydrothermal pretreatment on the straw powder alone to obtain a solid-liquid mixture; the fourth group is to perform hydrothermal pretreatment on the polylactic acid powder alone to obtain a solid-liquid mixture.

[0040] In some preferred embodiments of the present invention, in step 1), the polylactic acid powder and the straw powder are hydrothermally pretreated, the temperature in the hydrothermal reactor is 120-180°C, the time is 30-90min, the stirring speed is 100-180rpm, and the addition ratio of raw materials to water is 1:5-1:20; the pH of the polylactic acid powder after hydrothermal treatment is 2.2-2.7, the pH of the straw powder after hydrothermal treatment is 5.5-6.0, and the pH of the polylactic acid powder and the straw powder after hydrothermal treatment is 3.0-3.2.

[0041] In some preferred embodiments of the present invention, in step 2), the temperature of the anaerobic fermentation is 35-39°C, the organic load of the anaerobic fermentation is 25-35 gTS / L, the anaerobic fermentation time is 60-80 days, the fermentation stirring rate is 20-30 rpm, the stirring interval is 20-25 minutes every 4 hours, and the anaerobic fermentation is carried out in a nitrogen environment.

[0042] In some preferred embodiments of the present invention, in step 2), the anaerobic fermentation sludge is acclimated for 15 to 50 days by adding food waste, the acclimation temperature is 32 to 39° C., the acclimation stirring rate is 10 to 30 rpm, stirring is performed for 5 to 10 minutes every 2 to 3 hours, and the acclimation environment is carried out under nitrogen.

[0043] In some preferred embodiments of the present invention, the initial pH value of the anaerobic fermentation is preferably 7.0-8.0, and the initial pH value is adjusted by sodium hydroxide or hydrochloric acid, and the concentration of the sodium hydroxide or hydrochloric acid is preferably 1-4 mol / L, and more preferably 3 mol / L; the pH value of polylactic acid and straw after hydrothermal treatment alone or mixed hydrothermal treatment is 2.0-3.5, and the initial anaerobic fermentation pH value is adjusted to 7.0-8.0 with 3 mol / L sodium hydroxide, which is further optimized to 7.1-7.4.

[0044] In some preferred embodiments of the present invention, in step 2), the TS of the added anaerobic sludge is 9-12%, the VS is 6-8%, and the pH of the sludge is 7.1-7.3.

[0045] The straw in the embodiment of the present invention is corn straw.

[0046] Example 1 A method for producing biogas by anaerobic fermentation of straw

[0047] 1) Preparation of four groups of hydrothermal reaction solid-liquid mixtures: the first group (Hy-CS + Hy-PLA): polylactic acid powder (2.3 g) and straw powder (2.4 g) were hydrothermally pretreated (the solid-liquid ratio of raw materials to water was 1 g: 10 mL), and the solid-liquid mixtures obtained from the two were mixed at a mass ratio (VS) of 1: 1; the second group (Hy-(CS + PLA)): polylactic acid powder (2.3 g) and straw powder (2.4 g) were mixed at a mass ratio (VS) of 1: 1 and then hydrothermally pretreated (polylactic acid The third group (Hy-CS): the solid-liquid mixture was obtained by hydrothermal pretreatment of straw powder (4.9 g) alone (the mass ratio of raw material to water was 1:10); the fourth group (Hy-PLA) was obtained by hydrothermal pretreatment of polylactic acid powder (4.5 g) alone (the mass ratio of raw material to water was 1:10), the temperature in the hydrothermal reactor was 120°C, the time was 60 min, and the stirring speed was 150 rpm;

[0048] 2) The control groups were untreated corn straw (4.9 g), untreated PLA (4.5 g), untreated corn straw and PLA (2.4 g corn straw, 2.3 g PLA), and the blank group was only 40 g inoculum and 140 mL water, which were placed in four anaerobic fermentation reactors. 40 g of successfully domesticated sludge was added to each anaerobic fermentation reactor, and water was added to the effective volume of each anaerobic fermentation reaction of 180 mL; the TS of the sludge was 11.1%, the VS was 6.86%, and the pH was 7.52. All anaerobic fermentation reactors were heated with N 2 After flushing for 10 minutes, the flask was placed in a constant temperature and humidity water bath at 37±1℃ for anaerobic fermentation for 52 days. The flask was manually shaken 3 times a day for 2 minutes each time. Gas was collected and its composition was tested, and samples were taken to measure pH every day. The samples taken in each time period were saved.

[0049] The control group consisted of samples without hydrothermal pretreatment, namely corn straw (CS), polylactic acid (PLA) and a mixture of corn straw and polylactic acid (CS+PLA), which were subjected to anaerobic fermentation respectively, and the blank group consisted of anaerobic sludge.

[0050] Figure 3 Figure A shows that the biogas yield of anaerobic fermentation of Hy-CS is 199.0±12.0mL / gTS, and the biogas yield of anaerobic fermentation of Hy-(CS+PLA) is 126.2±6.43mL / gTS, which is 22.29% lower than the biogas yield of anaerobic fermentation of Hy-CS+Hy-PLA (162.4±17.9mL / gTS); the biogas yields of anaerobic fermentation of Hy-PLA and CS+PLA are 45.63±7.96mL / gTS and 41.19±5.42mL / gTS, respectively.

[0051] Figure 3 Figure B shows that the methane yield of anaerobic fermentation of Hy-CS is 135.7±9.29 mL / gTS, and the methane yield of anaerobic fermentation of Hy-(CS+PLA) is 86.92±5.51 mL / gTS, which is 17.77% lower than the methane yield of anaerobic fermentation of Hy-CS+Hy-PLA (105.7±5.85 mL / gTS); the methane yields of anaerobic fermentation of Hy-PLA and CS+PLA are 34.3±6.79 mL / gTS and 64.16±5.41 mL / gTS, respectively.

[0052] Example 2

[0053] 1) Preparation of four groups of hydrothermal reaction solid-liquid mixtures: the first group (Hy-CS + Hy-PLA): polylactic acid powder (2.3 g) and straw powder (2.3 g) were hydrothermally pretreated (the solid-liquid ratio of raw materials to water was 1 g: 10 mL), and the solid-liquid mixtures obtained from the two were mixed at a mass ratio (VS) of 1: 1; the second group (Hy-(CS + PLA)): polylactic acid powder (2.3 g) and straw powder (2.4 g) were mixed at a mass ratio (VS) of 1: 1 and then hydrothermally pretreated (polylactic acid The third group (Hy-CS): the solid-liquid mixture was obtained by hydrothermal pretreatment of straw powder (4.9 g) alone (the mass ratio of raw material to water was 1:10); the fourth group (Hy-PLA) was obtained by hydrothermal pretreatment of polylactic acid powder (4.5 g) alone (the mass ratio of raw material to water was 1:10), the temperature in the hydrothermal reactor was 150°C, the time was 60 min, and the stirring speed was 150 rpm;

[0054] 2) The control groups were untreated corn straw (4.9 g), untreated PLA (4.5 g), untreated corn straw and PLA (2.4 g corn straw, 2.3 g PLA), and the blank group was only 40 g inoculum and 140 mL water, which were placed in four anaerobic fermentation reactors. 40 g of successfully domesticated sludge was added to each anaerobic fermentation reactor, and water was added to the effective volume of each anaerobic fermentation reactor to 180 mL; the TS of the sludge was 11.1%, the VS was 6.86%, and the pH was 7.52. All anaerobic fermentation reactors were heated with N 2 Flush for 10 minutes, then place in a constant temperature and humidity water bath at 37±1℃ for 60 days of anaerobic fermentation, and shake the bottle manually 3 times a day, each time for 2 minutes. Collect gas and test its composition, take samples and measure pH every day, and save the samples taken in each time period.

[0055] The control group consisted of samples without hydrothermal pretreatment, namely corn straw (CS), polylactic acid (PLA) and a mixture of corn straw and polylactic acid (CS+PLA), which were subjected to anaerobic fermentation respectively, and the blank group consisted of anaerobic sludge.

[0056] Figure 3 Middle C shows that the anaerobic fermentation biogas yield of Hy-CS is 233.85±19.05mL / gTS, the anaerobic fermentation biogas yield of Hy-PLA is 222±17.11mL / gTS, the anaerobic fermentation biogas yield of Hy-(CS+PLA) is 382.07±7.27mL / gTS, and the anaerobic fermentation biogas yield of Hy-CS+Hy-PLA is 339.67±8.33mL / gTS.

[0057] Figure 3 Figure D shows that the methane yield of anaerobic fermentation of Hy-CS is 164.22±13.99 mL / gTS, the methane yield of anaerobic fermentation of Hy-PLA is 103.13±24.41 mL / gTS, the methane yield of anaerobic fermentation of Hy-(CS+PLA) is 228.04±13.79 mL / gTS, and the methane yield of anaerobic fermentation of Hy-CS+Hy-PLA is 218.13±6.59 mL / gTS.

[0058] Example 3

[0059] 1) Preparation of four groups of hydrothermal reaction solid-liquid mixtures: the first group (Hy-CS + Hy-PLA): polylactic acid powder (2.3 g) and straw powder (2.4 g) were hydrothermally pretreated (the solid-liquid ratio of raw materials to water was 1 g: 10 mL), and the solid-liquid mixtures obtained from the two were mixed at a mass ratio (VS) of 1: 1; the second group (Hy-(CS + PLA)): polylactic acid powder (2.3 g) and straw powder (2.4 g) were mixed at a mass ratio (VS) of 1: 1 and then hydrothermally pretreated (polylactic acid The third group (Hy-CS): the solid-liquid mixture was obtained by hydrothermal pretreatment of straw powder (4.9 g) alone (the mass ratio of raw material to water was 1:10); the fourth group (Hy-PLA) was obtained by hydrothermal pretreatment of polylactic acid powder (4.5 g) alone (the mass ratio of raw material to water was 1:10), the temperature in the hydrothermal reactor was 180°C, the time was 60 min, and the stirring speed was 150 rpm;

[0060] 2) The control groups were untreated corn straw (4.9 g), untreated PLA (4.5 g), untreated corn straw and PLA (2.4 g corn straw, 2.3 g PLA), and the blank group was only 40 g inoculum and 140 mL water, which were placed in four anaerobic fermentation reactors. 40 g of successfully domesticated sludge was added to each anaerobic fermentation reactor, and water was added to the effective volume of each anaerobic fermentation reaction of 180 mL; the TS of the sludge was 11.1%, the VS was 6.86%, and the pH was 7.52. All anaerobic fermentation reactors were heated with N 2 Flush for 10 minutes, then place in a constant temperature and humidity water bath at 37±1℃ for 60 days of anaerobic fermentation, and shake the bottle manually 3 times a day, each time for 2 minutes. Collect gas and test its composition, take samples and measure pH every day, and save the samples taken in each time period.

[0061] The control group consisted of samples without hydrothermal pretreatment, namely corn straw (CS), polylactic acid (PLA) and a mixture of corn straw and polylactic acid (CS+PLA), which were subjected to anaerobic fermentation respectively, and the blank group consisted of anaerobic sludge.

[0062] Figure 3 Figure E shows that the biogas yield of anaerobic fermentation of Hy-CS is 239.11±9.42mL / gTS, the biogas yield of anaerobic fermentation of Hy-PLA is 391.33±36.30mL / gTS, the biogas yield of anaerobic fermentation of Hy-(CS+PLA) is 367.63±16.98mL / gTS, and the biogas yield of anaerobic fermentation of Hy-CS+Hy-PLA is 343.93±25.84mL / gTS. Hy-(CS+PLA) is 1.54 times that of Hy-CS, and the biogas yield of anaerobic fermentation of Hy-(CS+PLA) is 6.89% higher than that of Hy-CS+Hy-PLA. These results indicate that the synergistic hydrothermal pretreatment of polylactic acid and straw is positive for anaerobic fermentation to produce biogas.

[0063] Figure 3 Figure F shows that the methane yield of anaerobic fermentation of Hy-CS is 124.87±5.52 mL / gTS, the methane yield of anaerobic fermentation of Hy-PLA is 280.24±30.30 mL / gTS, the methane yield of anaerobic fermentation of Hy-(CS+PLA) is 266.42±11.17 mL / gTS, and the methane yield of anaerobic fermentation of Hy-CS+Hy-PLA is 236.84±18.12 mL / gTS.

[0064] Figure 1 The hydrothermal fluid characterization diagram of corn stalks and polylactic acid pretreatment under different hydrothermal temperature conditions in Examples 1-3 of the present invention; wherein A is the soluble chemical oxygen demand (SCOD) and pH, and B is the VFA content change diagram. Figure 1It can be seen that with the increase of hydrothermal pretreatment temperature, the SCOD of CS hydrothermal liquid gradually increased from 5.41±0.05% to 7.46±0.28 / 20.08±0.34g / L, and the SCOD of PLA hydrothermal liquid increased from 1.52±0.08 to 15.64±0.28 / 111.3±3.2g / L, which shows that PLA is more sensitive to hydrothermal temperature. For the CS+PLA group, the SCOD after hydrothermal pretreatment at 120℃ and 150℃ was 4.43±0.07 and 17.25±0.28, respectively, which is 29.5% and 48.1% higher than the theoretical calculated values ​​(3.42±0.07, 11.65±0.28), respectively, indicating that the combined hydrothermal of the two promoted the further depolymerization and dissolution of organic matter. As the hydrothermal pretreatment temperature increased from 120°C to 150°C and 180°C, the pH of CS decreased from 6.10±0.16 to 5.64±0.38 and 4.39±0.27. The initial pH of PLA was about 7.00±0.20. After pretreatment at 120°C, the pH of the hydrothermal liquid reached 4.91±0.12. When the hydrothermal pretreatment temperature was increased to 150°C, its pH dropped rapidly to 3.00±0.20. When the hydrothermal treatment temperature was increased to 180°C, its pH further dropped to 2.52±0.17.

[0065] Figure 2 A is a comparison of the composition of lignocellulose after hydrothermal pretreatment of CS and PLA at different temperatures and CS alone at different temperatures; B is a scanning electron microscope (SEM) image of CS and PLA mixed with hydrothermal pretreatment at different temperatures and CS alone at different temperatures; Figure 2 As can be seen from Figure A, after pretreatment at different hydrothermal temperatures, the hemicellulose in the wood cellulose of Hy-CS and Hy-(CS+PLA) decreased significantly, while the relative percentages of cellulose and lignin generally increased, indicating that more hemicellulose was separated in the liquid phase than lignin and cellulose. Under the hydrothermal temperature of 180°C, the hemicellulose of Hy-CS was 5.71±0.02%, the hemicellulose of Hy-(CS+PLA) was 3.89±0.03%, and the hemicellulose of CS was 26.70±0.05%. The hemicellulose of the two experimental groups decreased significantly. In addition, the hemicellulose of Hy-(CS+PLA) was 1.83% lower than that of Hy-CS, indicating that the addition of PLA is conducive to the disintegration of the CS wrapping structure under hydrothermal treatment. Figure 2B It can be seen that the CS without hydrothermal pretreatment has a compact structure, almost no pores, and a tight organizational structure. After hydrothermal pretreatment at different temperatures, it is found that with the increase of pretreatment intensity, the organizational structure of CS is further damaged, and more internal structures are exposed (such as CS-120, CS-150, and CS-180), which is conducive to the stripping of lignin and the hydrolysis of cellulose.

[0066] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for producing biogas by anaerobic fermentation of straw, characterized in that: The straw is hydrothermally pretreated to obtain a solid-liquid mixture, and the solid-liquid mixture is anaerobic fermented to produce biogas using sludge as inoculum.

2. The method for producing biogas by anaerobic fermentation of straw according to claim 1, characterized in that: The hydrothermal pretreatment temperature is 120-180°C, the time is 50-90 min, and the solid-liquid ratio of straw to water is 1 g: 10 mL; and / or The TS of the sludge is 9-12%, the VS is 6-8%, and the pH is 7.1-7.3; and / or The temperature of the anaerobic fermentation is 35-39° C., the organic load is 25-35 gVS / L, and the time is 60-80 days.

3. The method for producing biogas by anaerobic fermentation of straw according to claim 2, characterized in that: The hydrothermal pretreatment temperature is 120°C and the time is 60 minutes; and / or The TS of the sludge is 11.1% and the VS is 6.86%; and / or The temperature of the anaerobic fermentation is 37±1° C., the organic load is 25-35 gVS / L, and the time is 52 days.

4. A method for producing biogas by anaerobic fermentation of straw, characterized in that: The straw and polylactic acid are mixed and then hydrothermally pretreated to obtain a solid-liquid mixture, and the solid-liquid mixture is anaerobic fermented to produce biogas using sludge as inoculum.

5. The method for producing biogas by anaerobic fermentation of straw according to claim 4, characterized in that: The mass ratio (VS) of the straw to the polylactic acid is 1:1; and / or The hydrothermal pretreatment temperature is 120-180°C, the time is 50-90 min, and the solid-liquid ratio of the sum of the straw and polylactic acid to water is 1 g: 10 mL; and / or The TS of the sludge is 9-12%, the VS is 6-8%, and the pH is 7.1-7.3; and / or The temperature of the anaerobic fermentation is 35-39° C., the organic load is 25-35 gVS / L, and the time is 60-80 days.

6. The method for producing biogas by anaerobic fermentation of straw according to claim 5, characterized in that: The hydrothermal pretreatment temperature is 180°C and the time is 60 minutes; and / or The TS of the sludge is 11.1% and the VS is 6.86%; and / or The temperature of the anaerobic fermentation is 37±1° C., the organic load is 25-35 gVS / L, and the time is 60 days.

7. The method for producing biogas by anaerobic fermentation of straw according to claim 1 or 4, characterized in that: The sludge is prepared by taming kitchen waste, and the taming parameters are: time 15 to 50 days, temperature 32 to 39° C., stirring rate 10 to 30 rpm, stirring for 5 to 10 minutes every 2 to 3 hours, and taming under nitrogen.

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