Method for producing biodiesel by using organic solid waste anaerobic fermentation liquor and microalgae

Abstract

The invention discloses a method for producing biodiesel by using organic solid waste anaerobic fermentation liquor and microalgae, which comprises the following steps: inoculating microalgae into a culture medium for culture, and collecting algae cells; and adding the organic solid waste anaerobic fermentation liquor into the residual culture medium, inoculating microalgae for culture, and collecting new algae cells. According to the method, the organic solid waste anaerobic fermentation liquid is directly added into the residual culture medium, so that a new microalgae culture system can be quickly formed, the production process can be simplified, continuous culture of microalgae can be realized, the accumulation amount of microalgae biomass and the yield of biodiesel can be increased, the use amount of water can be remarkably reduced, and the production cost can be reduced. And addition of a new carbon source is avoided, so that the production cost is reduced. The method has the advantages of being simple in process, convenient to operate, low in cost, high in microalgae biomass yield, high in biodiesel yield, good in biodiesel quality and the like, is suitable for large-scale production of the biodiesel, and facilitates industrial application of the biodiesel.

Description

Technical Field

[0001] The invention belongs to the field of biomass energy and microalgae biotechnology, and relates to a method for producing biodiesel by utilizing organic solid waste anaerobic fermentation liquid and microalgae. Background Art

[0002] With the over-exploitation of fossil fuels, the future energy crisis will pose a serious threat to human society, so it is urgent to develop new sustainable resources to meet the growing demand. As the raw material for the production of third-generation biomass energy, microalgae has outstanding advantages over the traditional crops used for biofuel processing in the first two generations: 1) it will not conflict with the development and utilization of arable land resources; 2) the metabolic growth period is relatively short; 3) it can be cultivated in harsh environments and can remove pollutants at the same time.

[0003] At present, the two major limiting factors for the market promotion and application of the technology of using microalgae to produce biodiesel are the high production cost and the need to consume a large amount of water resources. The improvement measures commonly used to reduce production costs and water resource consumption are mainly to use anaerobic fermentation liquid or organic wastewater as the source of water and nutrients for the cultivation of oil-producing microalgae. By rationally utilizing anaerobic fermentation liquid or organic wastewater, not only can the cost of microalgae production of biodiesel be reduced, and waste can be turned into treasure, but also the anaerobic fermentation liquid and organic wastewater can be harmlessly treated, reducing the secondary environmental pollution that may be caused by anaerobic fermentation liquid and organic wastewater. However, when anaerobic fermentation liquid is directly used as the source of water and nutrients required for the growth of microalgae, since the anaerobic fermentation liquid usually has a very high ammonia nitrogen concentration and phosphorus concentration, if it is directly added to the cultivation system of microalgae, it will inevitably have an adverse effect on the normal growth of microalgae, making it difficult to obtain a large amount of microalgae biomass, which in turn leads to a low yield of biodiesel. In addition, when organic wastewater is used as the water source and nutrient source required for the growth of microalgae, since organic wastewater usually contains a large amount of toxic and harmful substances, it will have an adverse effect on the normal growth of microalgae, and thus it is not conducive to improving the yield of microalgae, and thus the yield of biodiesel is low. At the same time, if the anaerobic fermentation liquid or organic wastewater is pretreated, the complexity of the production process will inevitably increase, and the corresponding processing equipment will also be increased, which is not conducive to reducing the production cost of biodiesel. In addition, in the production method of the existing reuse culture medium, the remaining culture solution of the previous stage is used as the reuse wastewater for preparing a new culture medium, and then the new culture medium is used to continue to cultivate microalgae to increase the lipid yield of microalgae. However, due to the lack of nutrients in the reuse wastewater, it is necessary to supplement nutrients (such as glucose) to ensure that the culture medium can meet the growth needs of microalgae, which makes the method still have the defect of high production cost, which is not conducive to realizing the large-scale production of microalgae biodiesel. Therefore, obtaining a method for producing biodiesel based on microalgae with simple process, convenient operation, low cost and high biodiesel yield is of great significance for promoting the widespread application of biodiesel. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for producing biodiesel by using anaerobic fermentation liquid of organic solid waste and microalgae, which has the advantages of simple process, convenient operation, low cost, high microalgae biomass yield and high biodiesel yield.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for producing biodiesel using anaerobic fermentation liquid of organic solid waste and microalgae comprises the following steps:

[0007] S1, inoculating microalgae into culture medium for cultivation, and collecting algal cells;

[0008] S2. Adding the organic solid waste anaerobic fermentation liquid to the remaining culture medium in step S1, stirring, sterilizing, inoculating microalgae, culturing the microalgae, and collecting algae cells.

[0009] The above method is further improved in that, in step S2, the volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining culture medium is ≤15%.

[0010] The above method is further improved, in step S2, the volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining culture medium is 5% to 15%.

[0011] The above method is further improved, in step S2, the volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining culture medium is 10% to 15%.

[0012] The above method is further improved, in step S2, the organic solid waste anaerobic fermentation liquid contains volatile fatty acids; the organic solid waste anaerobic fermentation liquid is a clarified liquid obtained by anaerobic fermentation of organic solid waste as raw material; the organic solid waste is kitchen waste; the sterilization is carried out at a temperature of 115°C to 130°C; and the sterilization time is 30 minutes.

[0013] The above method is further improved in that the volume ratio of the microalgae to the culture medium is 5%; the microalgae are Chlorophyta; and the culture medium is a microalgae culture medium.

[0014] The above method is further improved, wherein the microalgae is cultured under a light-dark ratio of 12h:12h or in complete darkness; when the microalgae is cultured under light conditions, the light intensity used is 180 μmol / m 2 S~240μmol / m 2 ·S; the microalgae are cultured at a temperature of 25°C to 30°C; the microalgae are cultured for 24 days.

[0015] The above method is further improved and further comprises the following steps:

[0016] S3. Repeat step S2, using the remaining culture medium as circulating water and the organic solid waste anaerobic fermentation liquid as a nutrient source to continuously culture the microalgae.

[0017] The above method is further improved and further comprises the following steps:

[0018] S4. Extract lipids or fatty acid methyl esters from algae cells to obtain biodiesel.

[0019] The above method is further improved, in step S4, the lipid extraction is to mix the algae cells with a chloroform-methanol solution, and ultrasonically extract to obtain lipids; the chloroform-methanol solution is obtained by mixing chloroform and methanol; the volume ratio of chloroform to methanol is 1:2 to 1:3; the time of ultrasonic extraction is 8 minutes to 12 minutes.

[0020] The above method is further improved, wherein the fatty acid methyl ester extraction is performed by mixing algae cells with a concentrated sulfuric acid-methanol solution, treating the mixture in a water bath at 80°C for 140-160 minutes, adding a methanol-water solution, stirring, and collecting an upper phase to obtain fatty acid methyl ester; the concentrated sulfuric acid-methanol solution is prepared by preparing concentrated sulfuric acid and methanol; the volume ratio of the concentrated sulfuric acid to methanol is 2:100; the methanol-water solution is prepared by preparing methanol and water; the volume ratio of the methanol to water is 2:1.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] (1) In view of the defects of the existing methods for producing biodiesel based on microalgae, such as complex process, high cost, low microalgae biomass yield, low biodiesel yield and substandard quality, the present invention creatively proposes a method for producing biodiesel using organic solid waste anaerobic fermentation liquid and microalgae. By directly adding the organic solid waste anaerobic fermentation liquid to the remaining culture medium, not only can a new culture medium suitable for the growth of microalgae be quickly formed, which is conducive to simplifying the production process and realizing the continuous culture of microalgae, thereby facilitating the increase of the accumulation of microalgae biomass and ultimately the increase of biodiesel yield, but also the water consumption can be significantly reduced, and the addition of new carbon sources can be avoided, which is conducive to reducing production costs and achieving the reduction of organic solid waste disposal. At the same time, in the present invention, the new culture system constructed with the remaining culture medium as circulating water and the organic solid waste anaerobic fermentation liquid as the nutrient source is conducive to the normal growth of microalgae under dark conditions, thereby effectively reducing production costs while saving resources. The method of producing biodiesel by utilizing anaerobic fermentation liquid of organic solid waste and microalgae has the advantages of simple process, convenient operation, low cost, high microalgae biomass yield, high biodiesel yield and good quality, etc. It is suitable for large-scale production of biodiesel and is convenient for realizing the industrial application of biodiesel.

[0023] (2) In the method of the present invention, by optimizing the volume ratio of the anaerobic fermentation liquid of organic solid waste to the remaining culture medium to ≤15%, in particular, the volume ratio of the two is 10% to 15%, which is more conducive to increasing the microalgae biomass yield and improving the biodiesel yield and quality. This is because when the volume ratio is lower than 5%, the nutrient concentration provided is insufficient to support the complete growth cycle of the microalgae. Although nutrient stress conditions can increase the lipid content, the total biomass concentration cannot be guaranteed, so the lipid yield does not meet the requirements; and when the volume ratio is higher than 15%, the ammonia nitrogen content in the anaerobic fermentation liquid exceeds the tolerance range of the microalgae, causing cell damage and death, which has a negative impact on the culture. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0025] Figure 1 This is a graph showing the concentration changes of various volatile fatty acids (VFAs) in the culture medium in Example 1 of the present invention.

[0026] Figure 2 This is a graph showing the concentration changes of various volatile fatty acids (VFAs) in the culture medium in Example 2 of the present invention.

[0027] Figure 3 This is a graph showing the concentration changes of various volatile fatty acids (VFAs) in the culture medium in Example 3 of the present invention.

[0028] Figure 4 This is a graph showing the concentration changes of various volatile fatty acids (VFAs) in the culture medium in Example 4 of the present invention.

[0029] Figure 5 This is a graph showing the concentration changes of various volatile fatty acids (VFAs) in the culture medium in Example 5 of the present invention.

[0030] Figure 6 This is a graph showing the concentration changes of various volatile fatty acids (VFAs) in the culture medium in Example 6 of the present invention.

[0031] Figure 7 Graph showing the changes in dry weight of microalgae biomass under different culture conditions in Examples 1-6 of the present invention and Comparative Example 1.

[0032] Figure 8 The content distribution diagram of each microalgae fatty acid methyl ester component under different culture conditions in Examples 1-6 of the present invention and Comparative Example 1 is shown. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0034] In the following examples, unless otherwise specified, the raw materials and instruments used are commercially available, the processes used are conventional processes, and the equipment used are conventional equipment.

[0035] Example

[0036] A method for producing biodiesel using anaerobic fermentation liquid of organic solid waste and microalgae comprises the following steps:

[0037] S1, inoculating microalgae into culture medium for cultivation, and collecting algal cells;

[0038] S2. Add the organic solid waste anaerobic fermentation liquid to the remaining culture medium in step S1 according to a volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining culture medium of ≤15%, stir, sterilize, inoculate microalgae, culture the microalgae, and collect algae cells.

[0039] In this embodiment, it is further improved that in step S2, the volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining culture medium is 5% to 15%.

[0040] In this embodiment, it is further improved that in step S2, the volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining culture medium is 10% to 15%.

[0041] In the present embodiment, it is further improved that in step S2, the organic solid waste anaerobic fermentation liquid contains volatile fatty acids; the organic solid waste anaerobic fermentation liquid is a clarified liquid obtained by anaerobic fermentation of organic solid waste as raw material; the organic solid waste is kitchen waste; the sterilization is carried out at a temperature of 115°C to 130°C; and the sterilization time is 30 minutes.

[0042] In this embodiment, it is further improved that the volume ratio of the microalgae to the culture medium is 5%; the microalgae are Chlorophyta; and the culture medium is a microalgae culture medium.

[0043] In this embodiment, the microalgae are further improved, and the culture is carried out under the condition of a light-dark ratio of 12h:12h or in complete darkness; when the microalgae are cultured under light conditions, the light intensity used is 180 μmol / m 2 S~240μmol / m 2 ·S; the microalgae are cultured at a temperature of 25°C to 30°C; the microalgae are cultured for 24 days.

[0044] In this embodiment, the method further comprises the following steps:

[0045] S3. Repeat step S2, using the remaining culture medium as circulating water and the organic solid waste anaerobic fermentation liquid as a nutrient source to continuously culture the microalgae.

[0046] S4. Extract lipids or fatty acid methyl esters from the collected algae cells to obtain biodiesel.

[0047] In this embodiment, the lipid extraction is to mix the algae cells with a chloroform-methanol solution and perform ultrasonic extraction to obtain lipids; the chloroform-methanol solution is obtained by mixing chloroform and methanol; the volume ratio of chloroform to methanol is 1:2 to 1:3; and the ultrasonic extraction time is 8 min to 12 min.

[0048] In this embodiment, the fatty acid methyl ester extraction is to mix the algae cells with a concentrated sulfuric acid-methanol solution, treat in a water bath at 80°C for 140min to 160min, add a methanol-water solution, stir, collect the upper phase, and obtain fatty acid methyl ester; the concentrated sulfuric acid-methanol solution is prepared by concentrated sulfuric acid and methanol; the volume ratio of concentrated sulfuric acid to methanol is 2:100; the methanol-water solution is prepared by methanol and water; the volume ratio of methanol to water is 2:1.

[0049] Example 1

[0050] A method for producing biodiesel using anaerobic fermentation liquid of organic solid waste and microalgae comprises the following steps:

[0051] (1) Microalgae (Chlorella Vulgaris) were inoculated into BG-11 medium (commercially available) at a volume ratio of 5% for microalgae and BG-11 medium, and cultured in the dark at 28°C for 24 days. After the culture was completed, the algae cells were collected by centrifugation.

[0052] (2) Collect the remaining BG-11 medium in step (1), add the organic solid waste anaerobic fermentation liquid according to the volume ratio of organic solid waste anaerobic fermentation liquid to the remaining BG-11 medium of 5%, stir evenly, sterilize at 121°C for 30 minutes, obtain a new culture medium, inoculate microalgae (Chlorella Vulgaris) into the new culture medium according to the volume ratio of microalgae to BG-11 medium (commercially available) of 5%, culture in the dark at 28°C for 24 days, and after the culture is completed, centrifuge and collect algae cells. In this step, the concentration changes of various volatile fatty acids (VFAs) in the new culture medium are as follows: Figure 1 As shown in Table 1 and Figure 7 shown.

[0053] In step (2), the organic solid waste anaerobic fermentation liquid used contains volatile fatty acids. The preparation method of the organic solid waste anaerobic fermentation liquid comprises the following steps: organic solid waste (kitchen waste) is used as a raw material, and is fed into an anaerobic fermentation tank for anaerobic fermentation to obtain a fermentation liquid rich in a variety of volatile fatty acids as the main components, and the fermentation liquid is centrifuged to obtain a clarified liquid, which is the organic solid waste anaerobic fermentation liquid used in the present invention.

[0054] (3) Collect the algal cells in step (1) and step (2).

[0055] (4) extracting lipids and fatty acid methyl esters from algae cells to obtain biodiesel, specifically:

[0056] (4.1) Lipid extraction: algae cells were mixed with chloroform-methanol solution, and ultrasonic extraction was performed for 10 minutes to obtain lipids, wherein the chloroform-methanol solution used was obtained by mixing chloroform and methanol, and the volume ratio of chloroform to methanol was 1:2. In this step, the accumulation amount of lipids is shown in Table 1.

[0057] (4.2) Extraction of fatty acid methyl esters is as follows: algae cells are mixed with a concentrated sulfuric acid-methanol solution, treated in a water bath at 80°C for 150 min, a methanol-water solution is added, stirred, and the upper phase is collected to obtain fatty acid methyl esters, wherein the concentrated sulfuric acid-methanol solution used is prepared from concentrated sulfuric acid and methanol, and the volume ratio of concentrated sulfuric acid to methanol is 2:100; the methanol-water solution used is prepared from methanol and water, and the volume ratio of methanol to water is 2:1. In this step, the component distribution of fatty acid methyl esters is shown in Table 2 and Figure 8 shown.

[0058] Example 2

[0059] A method for producing biodiesel using organic solid waste anaerobic fermentation liquid and microalgae is basically the same as Example 1, except that in Example 2, the volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining BG-11 culture medium is 10%.

[0060] In this example, the concentration changes of various volatile fatty acids (VFAs) in the new culture medium are as follows: Figure 2 shown.

[0061] Example 3

[0062] A method for producing biodiesel using organic solid waste anaerobic fermentation liquid and microalgae is basically the same as Example 1, except that in Example 3, the volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining BG-11 culture medium is 15%.

[0063] In this example, the concentration changes of various volatile fatty acids (VFAs) in the new culture medium are as follows: Figure 3shown.

[0064] Example 4

[0065] A method for producing biodiesel using anaerobic fermentation liquid of organic solid waste and microalgae is basically the same as Example 1, except that in Example 4, the microalgae are cultured under the condition of a light-dark ratio of 12h:12h, and the illumination intensity used during illumination is 220μmol / m 2 ·S.

[0066] In this example, the concentration changes of various volatile fatty acids (VFAs) in the new culture medium are as follows: Figure 4 shown.

[0067] Example 5

[0068] A method for producing biodiesel using organic solid waste anaerobic fermentation liquid and microalgae is basically the same as Example 4, except that in Example 5, the volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining BG-11 culture medium is 10%.

[0069] In this example, the concentration changes of various volatile fatty acids (VFAs) in the new culture medium are as follows: Figure 5 shown.

[0070] Example 6

[0071] A method for producing biodiesel using organic solid waste anaerobic fermentation liquid and microalgae is basically the same as Example 4, except that in Example 6, the volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining BG-11 culture medium is 15%.

[0072] In this example, the concentration changes of various volatile fatty acids (VFAs) in the new culture medium are as follows: Figure 6 shown.

[0073] Comparative Example 1

[0074] A method for producing biodiesel using microalgae is basically the same as Example 4, except that in Comparative Example 1, no organic solid waste anaerobic fermentation liquid is added.

[0075] Table 1 is the comparative data of microalgae biomass concentration, lipid content and lipid concentration under different culture conditions. As can be seen from Table 1, in Comparative Example 1, without adding anaerobic fermentation broth as a mixed nutrient source, the circulating water (remaining culture medium) cannot support the growth of microalgae, and the biomass and lipid accumulation are both the lowest. With the increase of the fermentation broth addition ratio, the lipid concentration will also rise in a related trend, where the lipid concentration in Example 6 reaches a maximum value of 557.60 mg / L, but the corresponding conditions are that light is required and the fermentation broth addition ratio is 15%, which will increase the production cost in the actual application process. In Example 3, there is no need for a lighting environment, the fermentation broth addition ratio is 15%, and the lipid concentration can reach 529.30 mg / L, which can further save costs when the accumulation amount is relatively considerable.

[0076] Table 1 Comparative data of different culture conditions on microalgae biomass concentration, lipid content and lipid concentration

[0077] Culture conditions Biomass concentration (g / L) Lipid content (%) Lipid concentration (mg / L) Example 1 5% fermentation liquid + dark 976.59±3.22 31.96±1.29 312.00±11.69 Example 2 10% fermentation liquid + dark 1245.57±8.97 34.71±0.77 432.20±8.68 Example 3 15% fermentation liquid + dark 1447.93±31.82 36.54±0.72 529.30±20.43 Example 4 5% fermentation liquid + light 998.75±9.27 37.31±0.20 372.60±1.79 Example 5 10% fermentation liquid + light 1255.33±15.78 39.10±0.98 490.90±16.17 Example 6 15% fermentation liquid + light 1454.51±20.37 38.34±0.39 557.60±2.78 Comparative Example 1 No Additive + Light 609.94±13.96 30.73±0.52 187.80±2.57

[0078] Figure 1 This is a graph showing the concentration changes of various volatile fatty acids (VFAs) in the culture medium in Example 1 of the present invention.

[0079] Figure 2 This is a graph showing the concentration changes of various volatile fatty acids (VFAs) in the culture medium in Example 2 of the present invention.

[0080] Figure 3 This is a graph showing the concentration changes of various volatile fatty acids (VFAs) in the culture medium in Example 3 of the present invention.

[0081] Figure 4 This is a graph showing the concentration changes of various volatile fatty acids (VFAs) in the culture medium in Example 4 of the present invention.

[0082] Figure 5 This is a graph showing the concentration changes of various volatile fatty acids (VFAs) in the culture medium in Example 5 of the present invention.

[0083] Figure 6 This is a graph showing the concentration changes of various volatile fatty acids (VFAs) in the culture medium in Example 6 of the present invention.

[0084] Depend on Figure 1-6 It can be seen that microalgae can completely absorb and utilize each VFAs component in the anaerobic fermentation broth.

[0085] Figure 7 Graph showing the changes in dry weight of microalgae biomass under different culture conditions in Examples 1-6 of the present invention and Comparative Example 1.

[0086] Figure 8The content distribution diagram of each microalgae fatty acid methyl ester component under different culture conditions in Examples 1-6 of the present invention and Comparative Example 1 is shown. Figure 3 The corresponding content is the mass percentage of each component.

[0087] Table 2 shows the performance data of microalgae fatty acid methyl esters under different culture conditions in Examples 1-6 of the present invention and Comparative Example 1.

[0088] From Table 1 and Figure 7 , Figure 8 It can be seen that in the present invention, the technology of anaerobic fermentation liquid of organic solid waste combined with recycling of harvested water can effectively support the cultivation and lipid accumulation of microalgae, and the fatty acid methyl ester finally obtained also meets the basic content characteristics of biodiesel production. At the same time, it can be seen from Table 2 that the fatty acid methyl ester prepared by the present invention retains the good properties of biodiesel and improves some parameter characteristics.

[0089] Table 2 Performance data of microalgae fatty acid methyl esters under different culture conditions in Examples 1-6 of the present invention and Comparative Example 1

[0090]

[0091]

[0092] It can be seen that the method of producing biodiesel using anaerobic fermentation liquid of organic solid waste and microalgae in the present invention has the advantages of simple process, convenient operation, low cost, high microalgae biomass yield, high biodiesel yield and good quality. It is suitable for large-scale production of biodiesel and is convenient for the industrial application of biodiesel. At the same time, it can meet the basic requirements of waste reduction and resource utilization and biofuel production.

[0093] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for producing biodiesel using anaerobic fermentation liquid of organic solid waste and microalgae, characterized in that: The following steps are involved: S1, inoculating microalgae into culture medium for cultivation, and collecting algal cells; S2. Adding the organic solid waste anaerobic fermentation liquid to the remaining culture medium in step S1, stirring, sterilizing, inoculating microalgae, culturing the microalgae, and collecting algae cells.

2. The method according to claim 1, characterized in that In step S2, the volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining culture medium is ≤15%.

3. The method according to claim 2, characterized in that In step S2, the volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining culture medium is 5% to 15%.

4. The method according to claim 3, characterized in that In step S2, the volume ratio of the organic solid waste anaerobic fermentation liquid to the remaining culture medium is 10% to 15%.

5. The method according to any one of claims 1 to 4, characterized in that: In step S2, the organic solid waste anaerobic fermentation liquid contains volatile fatty acids; the organic solid waste anaerobic fermentation liquid is a clarified liquid obtained by anaerobic fermentation of organic solid waste as raw material; the organic solid waste is kitchen waste; the sterilization is carried out at a temperature of 115°C to 130°C; and the sterilization time is 30 minutes.

6. The method according to any one of claims 1 to 4, characterized in that: The volume ratio of the microalgae to the culture medium is 5%; the microalgae are Chlorophyta; and the culture medium is a microalgae culture medium.

7. The method according to any one of claims 1 to 4, characterized in that: The microalgae are cultured under a light-dark ratio of 12h:12h or in complete darkness; when the microalgae are cultured under light conditions, the light intensity used is 180 μmol / m 2 S~240μmol / m 2 ·S; the microalgae are cultured at a temperature of 25°C to 30°C; the microalgae are cultured for 24 days.

8. The method according to any one of claims 1 to 4, characterized in that: The following steps are also included: S3. Repeat step S2, using the remaining culture medium as circulating water and the organic solid waste anaerobic fermentation liquid as a nutrient source to continuously culture the microalgae.

9. The method according to claim 8, characterized in that The following steps are also included: S4. Extract lipids or fatty acid methyl esters from algae cells to obtain biodiesel.

10. The method according to claim 9, characterized in that In step S4, the lipid extraction is to mix the algae cells with a chloroform-methanol solution, and ultrasonically extract to obtain lipids; the chloroform-methanol solution is obtained by mixing chloroform and methanol; the volume ratio of chloroform to methanol is 1:2 to 1:3; the ultrasonic extraction time is 8 minutes to 12 minutes; The fatty acid methyl ester extraction is as follows: algae cells are mixed with a concentrated sulfuric acid-methanol solution, treated in a water bath at 80°C for 140-160 minutes, a methanol-water solution is added, stirred, and the upper phase is collected to obtain fatty acid methyl ester; the concentrated sulfuric acid-methanol solution is prepared by preparing concentrated sulfuric acid and methanol; the volume ratio of the concentrated sulfuric acid to methanol is 2:100; the methanol-water solution is prepared by preparing methanol and water; the volume ratio of the methanol to water is 2:1.

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