Biogas production method based on enzyme-bacterium compound preparation and fruit waste

Abstract

The invention discloses a biogas production method based on an enzyme-bacterium compound preparation and fruit waste, and belongs to the technical field of agricultural waste resourceful treatment. The production method comprises the following steps: mixing and crushing fruit wastes into particles with the particle size of 1-5mm to obtain a mixed material; mixing with ultrapure water, adjusting the pH to be acidic, and heating in a water bath to obtain a mixed solution; cooling, adjusting the pH value, adding an enzyme-bacterium compound preparation, fermenting, centrifuging, and discarding the precipitate to obtain a fermentation liquid; adjusting the pH value to 6.8-7.5, transferring into an anaerobic fermentation tank, adding methanosarcina pasteurii, and carrying out secondary fermentation to obtain fermentation gas; and leading out from the anaerobic fermentation tank, and sequentially carrying out gas-liquid separation, desulfurization and dehydration treatment to obtain pure biogas. According to the method, the fruit waste is converted into high-quality clean energy, the biogas yield and the methane content are remarkably increased, and an efficient and reliable new way is provided for resourceful treatment of fruit processing byproducts.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of agricultural waste resource processing, and particularly relates to a biogas production method based on an enzyme-bacterium composite preparation and fruit waste. BACKGROUND

[0002] With the rapid development of fruit processing industry, a large amount of fruit waste such as peel, core and stem is produced. The fruit waste has high water content and rich organic matter content, and is prone to corruption and fermentation if not properly treated, causing environmental pollution. However, from the resource property, the fruit waste is rich in sugars, pectin, cellulose and hemicellulose, and is an ideal raw material for anaerobic fermentation to produce biogas.

[0003] At present, the resource processing methods for fruit waste mainly include direct landfill, composting and anaerobic digestion. Among them, the anaerobic digestion technology can simultaneously realize waste reduction, stabilization and clean energy (biogas) recovery, and therefore is concerned. The traditional fruit and vegetable waste anaerobic digestion process mainly adopts single-phase fermentation or directly puts the material into the anaerobic reactor after simple pretreatment. However, due to the characteristics of fruit waste such as fast hydrolysis speed and easy acidification, direct fermentation in a single reactor can easily lead to rapid accumulation of volatile fatty acids (VFAs), thereby inhibiting the activity of methanogenic bacteria, causing system acidification instability, and ultimately resulting in poor biogas yield and system operation stability. SUMMARY

[0004] The present application aims to provide a biogas production method based on an enzyme-bacterium composite preparation and fruit waste, which can convert fruit waste into high-quality clean energy, significantly improve biogas yield and methane content, and provide an efficient and reliable new way to solve the resource processing of fruit processing by-products.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows: A biogas production method based on an enzyme-bacterium composite preparation and fruit waste, comprising the following steps: S1, mixing and crushing the fruit waste into particles with a particle size of 1-5 mm to obtain a mixed material; S2, mixing the mixed material obtained in S1 with ultrapure water, adjusting the pH to be acidic, and heating in a water bath to obtain a mixed solution; S3, cooling the mixed solution obtained in S2, adjusting the pH, adding an enzyme-bacterium composite preparation, fermenting, centrifuging, discarding the precipitate, and obtaining a fermentation liquor; S4, adjusting the pH of the fermentation liquor obtained in S3 to 6.8-7.5, transferring it to an anaerobic fermentation tank, adding a Pasteur methanosaeta, and performing secondary fermentation to obtain a fermentation gas; S5, the fermentation gas generated in S4 is led out of the anaerobic fermentation tank, and sequentially subjected to gas-liquid separation, desulfurization and dehydration treatment to obtain pure biogas.

[0006] Preferably, in S1, the fruit waste comprises fruit stems and fruit shells, the fruit stems and fruit shells are derived from at least one of litchi or longan, and the dry weight mass ratio of the fruit stems to the fruit shells is (1:3)-(3:1).

[0007] Preferably, in S2, the pH is adjusted to 2-3, 80-120 The mixture is heated in a water bath for 1.5-2 h to obtain a mixed solution.

[0008] Preferably, in S3, the mixed solution obtained in S1 is cooled to 40-50 , and the pH is adjusted to 5.5-6.5.

[0009] Preferably, in S3, the enzyme-bacteria complex preparation comprises a complex hydrolytic enzyme preparation and a hydrolytic acidification bacterial agent, and the addition amount of the enzyme-bacteria complex preparation is 1.0%-3.0% of the dry weight of the mixture in S1 in terms of the complex hydrolytic enzyme preparation, and 1%-5% of the total volume of the fermentation system in S3 in terms of the hydrolytic acidification bacterial agent.

[0010] Preferably, the complex hydrolytic enzyme preparation comprises lignin peroxidase, xylanase, glucanase, pectinase and cellulase in an enzyme activity unit ratio of (4-5):(1-3):(2-3):(1-3):(2-5).

[0011] Preferably, the hydrolytic acidification bacterial agent comprises one of Clostridium butyricum and Lactobacillus amylovorus.

[0012] Preferably, in S3, the fermentation temperature is 35-42 , the fermentation time is 2-5 days, the centrifugation speed is 500-1200 rpm, and the centrifugation time is 15-20 min.

[0013] Preferably, in S4, the addition amount of the Methanosarcina mazei is 3%-8% of the total volume of the fermentation system in S4.

[0014] Preferably, in S4, the secondary fermentation temperature is 35-42 , and the secondary fermentation time is 15-25 days.

[0015] Compared with the prior art, the present application has the following advantages and technical effects: The application discloses a biogas production method based on an enzyme-bacterium composite preparation and fruit waste, and realizes efficient and deep degradation of fruit stem and fruit shell waste by adopting the enzyme-bacterium composite preparation and cooperating with acid pretreatment and a two-phase fermentation process. Embodiment data show that, compared with the comparative example 1, the biogas yield and methane content of the method for treating litchi and longan waste are significantly improved, and the energy recovery efficiency and quality are significantly improved. The application converts fruit waste into high-quality clean energy, and realizes significant progress in gas production efficiency, treatment rate, system stability and economic benefits, and provides an efficient and reliable new way for solving the resource treatment of fruit processing by-products.

[0016] The technical solutions of the application are further described below through examples. DETAILED DESCRIPTION

[0017] The technical solutions of the application are further described below through examples.

[0018] Unless otherwise defined, the technical terms or scientific terms used in the application should be understood as the general meanings understood by those skilled in the art.

[0019] In the application, unless otherwise specified, other test materials and instruments and equipment are conventional test materials in the art, and can be purchased through commercial channels.

[0020] Example 1 A biogas production method based on an enzyme-bacterium composite preparation and fruit waste comprises the following steps: S1, taking litchi fruit stems and fruit shells, drying and crushing, mixing according to a dry weight mass ratio of 1:3, crushing to a particle size of 5 mm to obtain a mixture; S2, weighing 100g of the mixture obtained in S1 and mixing with 500mL of ultrapure water, adjusting the pH to 2.5, 100 water bath heating for 1.5h to obtain a mixed solution; S3, cooling the mixed solution obtained in S2 to 45 , adjusting the pH to 6.0, adding an enzyme-bacterium composite preparation, 40 fermenting for 3 days, centrifuging at 800rpm for 15min, discarding the precipitate to obtain a fermentation liquor, wherein the enzyme-bacterium composite preparation comprises a composite hydrolytic enzyme preparation and a Clostridium butyricum bacterial liquid (viable bacterial count 1 10 9 ), and the composite hydrolytic enzyme preparation is a composite hydrolytic enzyme preparation with an enzyme activity unit ratio (U) of lignin peroxidase: xylanase: The glucanase, pectinase, and cellulase were mixed in a ratio of 4.5:2:2.5:2:3.5, and the addition amount was 2.0% of the dry weight of the mixture. The amount of Clostridium butyricum inoculum added was 3% of the total volume of the fermentation system. S4. Adjust the pH of the fermentation broth obtained in S3 to 7.2, transfer it to an anaerobic fermenter, and add *Methanococcus pasteurella* bacterial solution (live count...). 1 10 9 The amount added is 5% of the total volume of the fermentation system, and the fermentation process is carried out for 37 days. Secondary anaerobic fermentation for 20 days yielded fermentation gas. S5. The fermentation gas generated in S4 is drawn out from the anaerobic digester and passed through a gas-liquid separator, a desulfurizing agent, and a desiccant in sequence to obtain pure biogas.

[0021] Example 2 A biogas production method based on enzyme-bacterial compound preparation and fruit waste includes the following steps: S1. Take longan fruit stalks and shells, dry them and crush them, mix them at a dry weight ratio of 1:1, crush them into particles with a diameter of 5mm, and obtain the mixture. S2. Weigh 100g of the mixture obtained in S1 and mix it with 500mL of ultrapure water, adjusting the pH to 3.90. Heating in a water bath for 2 hours yields a mixed solution; S3. Cool the mixed solution obtained in S2 to 50°C. Adjust the pH to 5.5, add the enzyme-bacterial compound preparation, 42 Fermentation for 2 days, centrifugation at 1000 rpm for 18 minutes, discarding the precipitate to obtain the fermentation broth. The enzyme-bacterial compound preparation includes a compound hydrolytic enzyme preparation and *Lactobacillus amyloliquefaciens* (live count...). 1 10 9 The compound hydrolytic enzyme preparation is formulated with an enzyme activity unit ratio (U) of lignin peroxidase: xylanase: The ratio of glucanase:pectinase:cellulase is 4:1:2:3:5, and the amount added is 1.5% of the dry weight of the mixture. The amount of Lactobacillus amyloliquefaciens broth added is 4% of the total volume of the fermentation system. S4. Adjust the pH of the fermentation broth obtained in S3 to 7.0, transfer it to an anaerobic fermenter, and add *Methanococcus pasteurella* bacterial solution (live count...). 1 10 9 The amount added is 7% of the total volume of the fermentation system, and the process is carried out for 40 minutes. Secondary anaerobic fermentation for 18 days yielded fermentation gas. S5. The fermentation gas generated in S4 is drawn out from the anaerobic digester and passed through a gas-liquid separator, a desulfurizing agent, and a desiccant in sequence to obtain pure biogas.

[0022] Example 3 A biogas production method based on enzyme-bacterial compound preparation and fruit waste includes the following steps: S1. Take the fruit stalks and shells of lychee and longan, dry them, crush them, mix them at a dry weight ratio of 3:1, crush them into particles with a diameter of 5mm, and obtain the mixture. S2. Weigh 100g of the mixture obtained in S1 and mix it with 500mL of ultrapure water, adjusting the pH to 2. Heating in a water bath for 1.5 hours yields a mixed solution; S3. Cool the mixed solution obtained in S2 to 40°C. Adjust the pH to 6.5, add the enzyme-bacterial compound preparation, 35 Fermentation for 5 days, centrifugation at 1200 rpm for 20 minutes, and discarding the precipitate yielded the fermentation broth. The enzyme-bacterial compound preparation included a compound hydrolytic enzyme preparation and *Lactobacillus amyloliquefaciens* (live count...). 1 10 9 The compound hydrolytic enzyme preparation is formulated with an enzyme activity unit ratio (U) of lignin peroxidase: xylanase: The ratio of glucanase:pectinase:cellulase = 5:3:3:1:2 is mixed and the amount added is 3% of the dry weight of the mixture. The amount of Lactobacillus amyloliquefaciens broth added is 5% of the total volume of the fermentation system. S4. Adjust the pH of the fermentation broth obtained in S3 to 7.0, transfer it to an anaerobic fermenter, and add *Methanococcus pasteurella* bacterial solution (live count...). 1 10 9 The amount added is 5% of the total volume of the fermentation system, and the process is carried out for 40 minutes. Secondary anaerobic fermentation for 20 days yielded fermentation gas. S5. The fermentation gas generated in S4 is drawn out from the anaerobic digester and passed through a gas-liquid separator, a desulfurizing agent, and a desiccant in sequence to obtain pure biogas.

[0023] Comparative Example 1 The production method is the same as in Example 1, except that no enzyme preparations or hydrolytic acidifying bacteria are added in S3.

[0024] Comparative Example 2 The production method is same as example 1, the difference is that in S3, the complex hydrolytic enzyme preparation used only contains cellulase and xylanase (mixed in the ratio of 1:1 according to enzyme activity units), and the total amount of addition is same as example 1 (2.0%), and the hydrolytic acidification bacteria agent is same as example 1.

[0025] Comparative example 3 The production method is same as example 1, the difference is that in S3, the Clostridium butyricum liquid is not added.

[0026] The above examples 1-3 and comparative examples 1-3 are tested.

[0027] The total volume of gas produced by the anaerobic fermentation tank is recorded daily by using a wet gas flow meter, and after the secondary fermentation is stable, the volume percentage of methane in the biogas is determined by using a gas chromatograph, and the results are shown in Table 1.

[0028] Table 1 Total volume of biogas and volume percentage of methane

[0029] As can be seen from Table 1, the biogas yield and methane content of examples 1-3 of the present application are higher than those of comparative examples 1-3, which indicates that the addition of enzyme-bacteria complex preparation will cause the failure of the whole hydrolysis and acidification process, and the biogas yield and quality will decrease sharply, and the enzyme and bacteria in the present application are a functional complementary and synergistic organic whole, and any one of them cannot achieve the technical effect of the present application.

[0030] Finally, it should be pointed out that: the above examples are only used to illustrate the technical solutions of the present application but not to limit them, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the present application, and these modifications or equivalent replacements also cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for biogas production based on enzyme-bacteria complex preparation and fruit waste, characterized in that, The method comprises the following steps: S1, mixing and crushing fruit waste into particles with a particle size of 1-5 mm to obtain a mixture; S2, mixing the mixture obtained in S1 with ultrapure water, adjusting the pH to be acidic, heating in a water bath to obtain a mixed solution; S3, cooling the mixed solution obtained in S2, adjusting the pH, adding an enzyme-bacteria complex preparation, fermenting, centrifuging, discarding the precipitate, and obtaining a fermentation liquor; S4, adjusting the pH of the fermentation liquor obtained in S3 to 6.8-7.5, transferring it to an anaerobic fermentation tank, adding a pasteurized Methanosarcina, and performing secondary fermentation to obtain fermentation gas; S5, introducing the fermentation gas produced in S4 from the anaerobic fermentation tank, and sequentially performing gas-liquid separation, desulfurization and dehydration treatment to obtain pure biogas.

2. The production method according to claim 1, characterized by, In S1, the fruit waste includes fruit stems and fruit shells, and the fruit stems and fruit shells are derived from at least one of lychee or longan, and the dry weight mass ratio of the fruit stems to the fruit shells is (1:3)-(3:1).

3. The production method according to claim 1, characterized by, S2, adjust pH to 2-3, 80-120 Heat in water bath for 1.5-2h to get the mixed solution.

4. The production method according to claim 1, characterized by, In S3, the mixed solution obtained in S1 is cooled to 40-50 pH is adjusted to 5.5-6.

5.

5. The production method according to claim 1, characterized by, In S3, the enzyme-bacteria complex preparation comprises a complex hydrolytic enzyme preparation and a hydrolytic acidification bacterial agent, and the addition amount of the enzyme-bacteria complex preparation is 1.0%-3.0% of the dry weight of the mixture in S1 in terms of the complex hydrolytic enzyme preparation and 1%-5% of the total volume of the fermentation system in S3 in terms of the hydrolytic acidification bacterial agent.

6. The production method according to claim 5, characterized by, The complex hydrolytic enzyme preparation consists of lignin peroxidase, xylanase, - glucanase, pectolytic enzyme and cellulase in the ratio of enzyme activity units (4-5):(1-3):(2-3):(1-3):(2-5).

7. The production method according to claim 5, characterized by, The hydrolytic acidification bacterial agent comprises one of Clostridium butyricum and Lactobacillus amylovorus.

8. The production method according to claim 1, characterized by, In S3, the temperature of the fermentation is 35-42 , the time of the fermentation is 2-5 days, the speed of the centrifugation is 500-1200 rpm, and the time of the centrifugation is 15-20 min.

9. The production method according to claim 1, characterized by, In S4, the addition amount of the pasteurized Methanosarcina is 3%-8% of the total volume of the fermentation system in S4.

10. The production method according to claim 1, characterized by, In S4, the secondary fermentation temperature is 35-42 , and the secondary fermentation time is 15-25 days.

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