A method for producing biogas through anaerobic fermentation of straw

Abstract

This invention discloses a method for producing biogas through anaerobic fermentation of straw, belonging to the field of solid waste treatment and disposal. The method involves hydrothermal pretreatment of straw to obtain a solid-liquid mixture, which is then subjected to anaerobic fermentation using sludge as inoculum to produce biogas. Both straw and polylactic acid (PLA) are potentially high-quality fermentation substrates. Converting them into biogas through anaerobic fermentation increases the utilization rate of waste and reduces secondary pollution to the environment.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment and disposal, and in particular relates to a method for producing biogas through anaerobic fermentation of straw. Background Technology

[0002] During anaerobic fermentation of straw, the unique encapsulation structure of lignocellulose forms compact crystals, resulting in dense straw, low porosity, poor accessibility of cellulose and hemicellulose to microorganisms and extracellular enzymes, and significantly reduced fermentation efficiency. Furthermore, the hydrothermal pretreatment of straw introduces a new waste product, polylactic acid (PLA), which degrades slowly during anaerobic fermentation, requiring 250 days to several years (Cucina et al., 2021). Therefore, there is an urgent need in this field for a method to produce biogas from straw through anaerobic fermentation in a short time without generating PLA waste. Summary of the Invention

[0003] The purpose of this invention is to provide a method for producing biogas through anaerobic fermentation of straw, thereby solving the problems existing in the prior art. This invention proposes to utilize hydrothermal technology, employing an acidic hydrothermal environment generated by polylactic acid hydrothermal treatment to break and dissolve the ester-ether bonds in lignin, achieving the separation of cellulose and hemicellulose. Simultaneously, it catalyzes the hydrolysis of cellulose and hemicellulose under low-temperature conditions, promoting the subsequent anaerobic fermentation of straw to produce biogas.

[0004] One of the technical solutions:

[0005] A method for producing biogas through anaerobic fermentation of straw involves pretreating straw with hydrothermal heat to obtain a solid-liquid mixture, and then using sludge as an inoculum to perform anaerobic fermentation of the solid-liquid mixture to produce biogas.

[0006] Preferably, 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

[0007] The sludge has a total saturation (TS) of 9–12%, a saturation (VS) of 6–8%, and a pH of 7.1–7.3; and / or

[0008] The anaerobic fermentation was carried out at a temperature of 35–39°C, with an organic load of 25–35 gVS / L, for a duration of 60–80 days.

[0009] More preferably, the hydrothermal pretreatment is performed at a temperature of 120°C for a time of 60 minutes; and / or

[0010] The sludge has a total sulfide (TS) content of 11.1%, a standard sulfide (VS) content of 6.86%, and a pH of 7.52; and / or

[0011] The anaerobic fermentation was carried out at a temperature of 37±1℃, with an organic load of 25~35gVS / L and a duration of 52d.

[0012] Technical Solution Two:

[0013] A method for producing biogas through anaerobic fermentation of straw involves mixing straw with polylactic acid and then subjecting the mixture to hydrothermal pretreatment to obtain a solid-liquid mixture. Sludge is then used as an inoculum to perform anaerobic fermentation of the solid-liquid mixture to produce biogas.

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

[0015] The hydrothermal pretreatment is performed at a temperature of 120–180°C for 50–90 minutes, and the solid-liquid ratio of the straw and polylactic acid to water is 1 g: 10 mL; and / or

[0016] The sludge has a total saturation (TS) of 9–12%, a saturation (VS) of 6–8%, and a pH of 7.1–7.3; and / or

[0017] The anaerobic fermentation was carried out at a temperature of 35–39°C, with an organic load of 25–35 gVS / L, for a duration of 60–80 days.

[0018] More preferably, the hydrothermal pretreatment is performed at a temperature of 180°C for a time of 60 minutes; and / or

[0019] The sludge has a total sulfide (TS) content of 11.1%, a standard sulfide (VS) content of 6.86%, and a pH of 7.52; and / or

[0020] The anaerobic fermentation was carried out at a temperature of 37±1℃, with an organic load of 25~35gVS / L and a duration of 60d.

[0021] Preferably, the sludge is prepared by acclimation of kitchen waste, with the following acclimation parameters: time 15-50 days, temperature 32-39℃, stirring rate 10-30 rpm, stirring for 5-10 minutes every 2-3 hours, and acclimation under nitrogen.

[0022] This invention proposes a synergistic hydrothermal pretreatment method for polylactic acid and straw to improve the efficiency of hydrolysis acidification and biogas production in the anaerobic fermentation process, and to achieve 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] Straw and polylactic acid are both potentially high-quality fermentation substrates. By treating them through anaerobic fermentation and converting them into biogas, the utilization rate of waste is increased and secondary pollution to the environment is reduced.

[0025] Polylactic acid (PLA) is mixed with straw and subjected to hydrothermal pretreatment. The acidic hydrothermal environment created by this process effectively catalyzes the conversion of (hemi)cellulose and the dissolution of lignin, promoting anaerobic fermentation of straw to produce biogas. The pretreated PLA-straw mixture is then directly subjected to anaerobic fermentation, avoiding substrate loss and simplifying the operation.

[0026] Polylactic acid (PLA) degrades slowly during anaerobic fermentation, resulting in a long fermentation time. Hydrothermal treatment provides an acidic hydrothermal environment for straw, accelerating the depolymerization of lignin with cellulose and hemicellulose, increasing the surface area of ​​cellulose and hemicellulose in contact with anaerobic microorganisms, and effectively shortening the fermentation time. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The above are characterization diagrams of the hydrothermal liquid after pretreatment of corn straw and polylactic acid under different hydrothermal temperature conditions in Examples 1-3 of the present invention. In this diagram, A represents the soluble chemical oxygen demand (SCOD) and pH, and B represents the change in VFA content.

[0029] Figure 2 A shows a comparison of the lignocellulose composition of CS and PLA after hydrothermal pretreatment at different temperatures and CS alone after hydrothermal pretreatment at different temperatures. B shows scanning electron microscope (SEM) images of CS and PLA after hydrothermal pretreatment at different temperatures and CS alone after hydrothermal pretreatment at different temperatures.

[0030] Figure 3 Figure A shows a comparison of the cumulative biogas yield of each group in Example 1 through anaerobic fermentation; Figure B shows a comparison of the cumulative methane yield of each group in Example 1 through anaerobic fermentation; Figure C shows a comparison of the cumulative biogas yield of each group in Example 2 through anaerobic fermentation; Figure D shows a comparison of the cumulative methane yield of each group in Example 2 through anaerobic fermentation; Figure E shows a comparison of the cumulative biogas yield of each group in Example 3 through anaerobic fermentation; and Figure F shows a comparison of the cumulative methane yield of each group in Example 3 through anaerobic fermentation. Detailed Implementation

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

[0032] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0033] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0034] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

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

[0036] This invention provides a method for producing biogas through anaerobic fermentation of straw, the steps of which are as follows:

[0037] 1) Pretreatment stage: Polylactic acid and straw water are placed in 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 and anaerobic fermentation is carried out to produce biogas.

[0039] The method for obtaining the solid-liquid mixture in step 1) is as follows: the first group involves pretreating polylactic acid powder and straw powder separately with hydrothermal heat, and then mixing the resulting solid-liquid mixture to obtain an anaerobic fermentation solid-liquid mixture; the second group involves pretreating polylactic acid powder and straw powder with hydrothermal heat to obtain a solid-liquid mixture; the third group involves pretreating straw powder alone with hydrothermal heat to obtain a solid-liquid mixture; and the fourth group involves pretreating polylactic acid powder alone with hydrothermal heat to obtain a solid-liquid mixture.

[0040] In some preferred embodiments of the present invention, in step 1), the polylactic acid powder and straw powder are subjected to hydrothermal pretreatment. The temperature inside the hydrothermal reactor is 120-180℃, the time is 30-90 min, the stirring speed is 100-180 rpm, and the 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 mixture of polylactic acid powder and straw powder after hydrothermal treatment is 3.0-3.2.

[0041] In some preferred embodiments of the present invention, in step 2), the anaerobic fermentation temperature 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 min every 4 hours, and the anaerobic fermentation is carried out in a nitrogen atmosphere.

[0042] In some preferred embodiments of the present invention, in step 2), the anaerobic fermentation sludge is acclimated to kitchen waste for 15 to 50 days at an acclimation temperature of 32 to 39°C, with an acclimation stirring rate of 10 to 30 rpm and stirring for 5 to 10 minutes every 2 to 3 hours. The acclimation 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 to 8.0, and the initial pH value is adjusted by sodium hydroxide or hydrochloric acid, wherein the concentration of sodium hydroxide or hydrochloric acid is preferably 1 to 4 mol / L, and more preferably 3 mol / L; the pH value of polylactic acid and straw after hydrothermal treatment alone or in combination is 2.0 to 3.5, and the initial anaerobic fermentation pH value is adjusted by 3 mol / L sodium hydroxide to 7.0 to 8.0, and further optimized to 7.1 to 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 used in this embodiment of the invention is corn straw.

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

[0047] 1) Four groups of hydrothermal reaction solid-liquid mixtures were prepared: Group 1 (Hy-CS+Hy-PLA): Polylactic acid powder (2.3g) and straw powder (2.4g) were respectively subjected to hydrothermal pretreatment (the solid-liquid ratio of raw materials to water was 1g:10mL), and the resulting solid-liquid mixtures were mixed at a mass ratio (VS) of 1:1; Group 2 (Hy-(CS+PLA)): Polylactic acid powder (2.3g) and straw powder (2.4g) were mixed at a mass ratio (VS) of 1:1 and then subjected to hydrothermal pretreatment (polylactic acid powder was ... A solid-liquid mixture was obtained by combining acid powder and straw powder with water in a solid-liquid ratio of 1:10; the third group (Hy-CS) was obtained by hydrothermal pretreatment of straw powder alone (4.9g) (raw material to water mass ratio of 1:10); the fourth group (Hy-PLA) was obtained by hydrothermal pretreatment of polylactic acid powder alone (4.5g) (raw material to water mass ratio of 1:10). The temperature in the above hydrothermal reactors was 120℃, the time was 60min, and the stirring speed was 150rpm.

[0048] 2) The control groups consisted of untreated corn stalks (4.9g), untreated PLA (4.5g), and untreated corn stalks and PLA (2.4g corn stalks, 2.3g PLA). The blank control group consisted of only 40g inoculum and 140mL water. All samples were placed in four anaerobic fermentation reactors. 40g of successfully acclimated sludge was added to each reactor, and water was added to bring the effective volume of each reactor to 180mL. The total sludge concentration (TS) was 11.1%, the standard deviation (VS) was 6.86%, and the pH was 7.52. All anaerobic fermentation reactors were purged with N2 for 10 minutes and then placed in a constant temperature and humidity water bath at 37±1℃ for 52 days of anaerobic fermentation. The flasks were manually shaken three times a day for 2 minutes each time. Gas was collected daily, and the gas composition and pH were measured. Samples were stored for each time period.

[0049] The control group consisted of samples that did not undergo hydrothermal pretreatment, namely corn stalks (CS), polylactic acid (PLA), and a mixture of stalks and PLA (CS+PLA) undergoing anaerobic fermentation, while the blank group consisted of anaerobic sludge.

[0050] Figure 3 The results from the study showed that the biogas yield from anaerobic fermentation of Hy-CS was 199.0±12.0 mL / gTS, and the biogas yield from anaerobic fermentation of Hy-(CS+PLA) was 126.2±6.43 mL / gTS, which was 22.29% lower than that from anaerobic fermentation of Hy-CS+Hy-PLA (162.4±17.9 mL / gTS). The biogas yields from anaerobic fermentation of Hy-PLA and CS+PLA were 45.63±7.96 mL / gTS and 41.19±5.42 mL / gTS, respectively.

[0051] Figure 3 The results from the B study showed that the methane yield from anaerobic fermentation of Hy-CS was 135.7±9.29 mL / gTS, while the methane yield from anaerobic fermentation of Hy-(CS+PLA) was 86.92±5.51 mL / gTS, which was 17.77% lower than that from anaerobic fermentation of Hy-CS+Hy-PLA (105.7±5.85 mL / gTS). The methane yields from anaerobic fermentation of Hy-PLA and CS+PLA were 34.3±6.79 mL / gTS and 64.16±5.41 mL / gTS, respectively.

[0052] Example 2

[0053] 1) Four groups of hydrothermal reaction solid-liquid mixtures were prepared: Group 1 (Hy-CS+Hy-PLA): Polylactic acid powder (2.3g) and straw powder (2.3g) were respectively subjected to hydrothermal pretreatment (the solid-liquid ratio of raw materials to water was 1g:10mL), and the resulting solid-liquid mixtures were mixed at a mass ratio (VS) of 1:1; Group 2 (Hy-(CS+PLA)): Polylactic acid powder (2.3g) and straw powder (2.4g) were mixed at a mass ratio (VS) of 1:1 and then subjected to hydrothermal pretreatment (polylactic acid powder was ... The first group (Hy-CS) obtained a solid-liquid mixture by hydrothermal pretreatment of straw powder (4.9g) with water at a mass ratio of 1:10; the second group (Hy-PLA) obtained a solid-liquid mixture by hydrothermal pretreatment of polylactic acid powder (4.5g) with water at a mass ratio of 1:10. The temperature in the hydrothermal reactor was 150℃, the time was 60min, and the stirring speed was 150rpm.

[0054] 2) The control groups consisted of untreated corn stalks (4.9g), untreated PLA (4.5g), and untreated corn stalks and PLA (2.4g corn stalks, 2.3g PLA). The blank group consisted of only 40g inoculum and 140mL water. All were placed in four anaerobic fermentation reactors. 40g of successfully acclimated sludge was added to each reactor, and water was added to each reactor's effective volume to 180mL. The sludge's total sludge concentration (TS) was 11.1%, its relative sludge concentration (VS) was 6.86%, and its pH was 7.52. All anaerobic fermentation reactors were purged with N2 for 10 min, then placed in a constant temperature and humidity water bath at 37±1℃ for anaerobic fermentation for 60 days. The flasks were manually shaken three times daily for 2 min each time. Gas was collected daily, and its composition was analyzed. pH samples were also taken and stored for each time period.

[0055] The control group consisted of samples that did not undergo hydrothermal pretreatment, namely corn stalks (CS), polylactic acid (PLA), and a mixture of stalks and PLA (CS+PLA) undergoing anaerobic fermentation, while the blank group consisted of anaerobic sludge.

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

[0057] Figure 3 The results from the study showed that the methane yield from anaerobic fermentation of Hy-CS was 164.22±13.99 mL / gTS, the methane yield from anaerobic fermentation of Hy-PLA was 103.13±24.41 mL / gTS, the methane yield from anaerobic fermentation of Hy-(CS+PLA) was 228.04±13.79 mL / gTS, and the methane yield from anaerobic fermentation of Hy-CS+Hy-PLA was 218.13±6.59 mL / gTS.

[0058] Example 3

[0059] 1) Four groups of hydrothermal reaction solid-liquid mixtures were prepared: Group 1 (Hy-CS+Hy-PLA): Polylactic acid powder (2.3g) and straw powder (2.4g) were respectively subjected to hydrothermal pretreatment (the solid-liquid ratio of raw materials to water was 1g:10mL), and the resulting solid-liquid mixtures were mixed at a mass ratio (VS) of 1:1; Group 2 (Hy-(CS+PLA)): Polylactic acid powder (2.3g) and straw powder (2.4g) were mixed at a mass ratio (VS) of 1:1 and then subjected to hydrothermal pretreatment (polylactic acid powder was ... A solid-liquid mixture was obtained by combining acid powder and straw powder with water in a solid-liquid ratio of 1:10; the third group (Hy-CS) was obtained by hydrothermal pretreatment of straw powder alone (4.9g) (raw material to water mass ratio of 1:10); the fourth group (Hy-PLA) was obtained by hydrothermal pretreatment of polylactic acid powder alone (4.5g) (raw material to water mass ratio of 1:10). The temperature in the above hydrothermal reactor was 180℃, the time was 60min, and the stirring speed was 150rpm.

[0060] 2) The control groups consisted of untreated corn stalks (4.9g), untreated PLA (4.5g), and untreated corn stalks and PLA (2.4g corn stalks, 2.3g PLA). The blank control group consisted of only 40g inoculum and 140mL water. All samples were placed in four anaerobic fermentation reactors. 40g of successfully acclimated sludge was added to each reactor, and water was added to bring the effective volume of each reactor to 180mL. The total sludge concentration (TS) was 11.1%, the standard deviation (VS) was 6.86%, and the pH was 7.52. All anaerobic fermentation reactors were purged with N2 for 10 minutes and then placed in a constant temperature and humidity water bath at 37±1℃ for anaerobic fermentation for 60 days. The flasks were manually shaken three times a day for 2 minutes each time. Gas was collected daily, and the gas composition and pH were measured. Samples were stored for each time period.

[0061] The control group consisted of samples that did not undergo hydrothermal pretreatment, namely corn stalks (CS), polylactic acid (PLA), and a mixture of stalks and PLA (CS+PLA) undergoing anaerobic fermentation, while the blank group consisted of anaerobic sludge.

[0062] Figure 3 The results from the study showed that the biogas yield from anaerobic fermentation of Hy-CS was 239.11±9.42 mL / gTS, that of Hy-PLA was 391.33±36.30 mL / gTS, that of Hy-(CS+PLA) was 367.63±16.98 mL / gTS, and that of Hy-CS+Hy-PLA was 343.93±25.84 mL / gTS. Hy-(CS+PLA) yielded 1.54 times that of Hy-CS, and its biogas yield was 6.89% higher than that of Hy-CS+Hy-PLA. These results indicate that the synergistic hydrothermal pretreatment of polylactic acid and straw has a positive effect on anaerobic fermentation biogas production.

[0063] Figure 3 The results from the study showed that the methane yield from anaerobic fermentation of Hy-CS was 124.87±5.52 mL / gTS, the methane yield from anaerobic fermentation of Hy-PLA was 280.24±30.30 mL / gTS, the methane yield from anaerobic fermentation of Hy-(CS+PLA) was 266.42±11.17 mL / gTS, and the methane yield from anaerobic fermentation of Hy-CS+Hy-PLA was 236.84±18.12 mL / gTS.

[0064] Figure 1 These are characterization graphs of the hydrothermal fluids pretreated with corn straw and polylactic acid under different hydrothermal temperature conditions in Examples 1-3 of this invention; where A represents soluble chemical oxygen demand (SCOD) and pH, and B represents the change in VFA content. Figure 1As the hydrothermal pretreatment temperature increases, the SCOD of the CS hydrothermal liquid gradually increases from 5.41±0.05% to 7.46±0.28 / 20.08±0.34 g / L, while the SCOD of the PLA hydrothermal liquid increases from 1.52±0.08 to 15.64±0.28 / 111.3±3.2 g / L, indicating that PLA is more sensitive to hydrothermal temperature. For the CS+PLA group, the SCODs after hydrothermal pretreatment at 120℃ and 150℃ were 4.43±0.07 and 17.25±0.28, respectively, which are 29.5% and 48.1% higher than the theoretically calculated values ​​(3.42±0.07 and 11.65±0.28), respectively, indicating that the combined hydrothermal treatment of both promoted further depolymerization and dissolution of organic matter. As the hydrothermal pretreatment temperature increased from 120℃ to 150℃ and 180℃, the pH of CS decreased from 6.10±0.16 to 5.64±0.38 and 4.39±0.27, respectively. The initial pH of PLA (polylactic acid) was approximately 7.00±0.20. Pretreatment at 120℃ achieved a hydrothermal liquid pH of 4.91±0.12. When the pretreatment temperature was increased to 150℃, the pH rapidly decreased to 3.00±0.20. When the hydrothermal treatment temperature was increased to 180℃, the pH further decreased to 2.52±0.17.

[0065] Figure 2 Image A shows a comparison of lignocellulose composition after hydrothermal pretreatment of a mixture of CS and PLA at different temperatures, and after hydrothermal pretreatment of CS alone at different temperatures. Image B shows scanning electron microscope (SEM) images of the lignocellulose after hydrothermal pretreatment of a mixture of CS and PLA at different temperatures, and after hydrothermal pretreatment of CS alone at different temperatures. Figure 2 As shown in Figure A, after pretreatment at different hydrothermal temperatures, the hemicellulose content in the lignocellulose of Hy-CS and Hy-(CS+PLA) decreased significantly, while the relative percentages of cellulose and lignin generally increased, indicating that more hemicellulose separated in the liquid phase than lignin and cellulose was present. At a hydrothermal temperature of 180℃, the hemicellulose content of Hy-CS was 5.71±0.02%, that of Hy-(CS+PLA) was 3.89±0.03%, and that of CS was 26.70±0.05%, showing a significant decrease in hemicellulose content in both experimental groups. Furthermore, the hemicellulose content of Hy-(CS+PLA) was 1.83% lower than that of Hy-CS, indicating that the addition of PLA facilitated the disintegration of the CS-encapsulated structure under hydrothermal treatment. Figure 2As can be seen from B, the untreated CS has a compact structure with almost no pores and a dense microstructure. After hydrothermal pretreatment at different temperatures, it was found that the microstructure of CS was further damaged with the increase of pretreatment intensity, and more internal structures were exposed (such as CS-120, CS-150, and CS-180), which is conducive to the exfoliation of lignin and the hydrolysis of cellulose.

[0066] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for producing biogas through anaerobic fermentation of straw, characterized in that, Straw and polylactic acid are mixed and pretreated with hydrothermal heat to obtain a solid-liquid mixture. Sludge is used as inoculum to anaerobic ferment the solid-liquid mixture to produce biogas. The mass ratio of straw to polylactic acid is 1:1; the solid-liquid ratio of the sum of straw and polylactic acid to water is 1g:10mL; the sludge has a total saturation (TS) of 11.1%, a total saturation (VS) of 6.86%, and a pH of 7.1–7.

3. The hydrothermal pretreatment was carried out at a temperature of 180℃ for 60 minutes; the anaerobic fermentation was carried out at a temperature of 37±1℃, an organic load of 25~35gVS / L for 60 days.

2. The method for producing biogas through anaerobic fermentation of straw according to claim 1, characterized in that, The sludge was prepared by acclimation of kitchen waste. The acclimation parameters were: time 15-50 days, temperature 32-39℃, stirring rate 10-30 rpm, stirring for 5-10 minutes every 2-3 hours, and acclimation under nitrogen.

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