Method for preparing fatty acid by anaerobic fermentation of organic solid waste

Abstract

The invention discloses a method for preparing fatty acid by anaerobic fermentation of organic solid waste, which comprises the following steps: S1, inoculating activated sludge into an anaerobic reactor, and adding the organic solid waste for anaerobic fermentation; s2, part of fermentation products are discharged from the anaerobic reactor in the anaerobic fermentation process, the discharged fermentation products are subjected to solid-liquid separation to obtain biogas residues, the organic solid waste and the biogas residues are added into the anaerobic reactor, and the volume ratio of the biogas residues to the organic solid waste is 1: (6-10); s3, the step S2 is repeated, anaerobic fermentation is continuously carried out, and organic solid waste treatment is completed. According to the method, the organic carbon source in the organic solid waste can be continuously and efficiently converted into the fatty acid, the method has the advantages of being simple in process, low in cost, high in preparation efficiency, high in substrate utilization rate, high in fatty acid yield, high in medium-chain fatty acid proportion and the like, and a new way is provided for efficient resource utilization of the organic solid waste.

Description

Technical Field

[0001] The invention belongs to the field of organic solid waste utilization, and specifically relates to a method for preparing fatty acids by anaerobic fermentation of organic solid waste. Background Art

[0002] With the rapid development of economy, the output of organic solid waste is also increasing. In particular, with the improvement of people's living standards, the large amount of food waste has an increasingly serious impact on the environment, which has attracted widespread attention. At the same time, the main components of food waste are organic matter such as starch, animal fat, and dietary fiber. It has the characteristics of high water content, high oil content, high salt content, and carbon-nitrogen ratio suitable for biodegradation. Therefore, the reduction, harmlessness, and resource utilization related to it have become the focus of everyone's general attention.

[0003] The anaerobic fermentation process can convert most of the organic matter in the food waste into high value-added products, such as fatty acids, methane, etc., thereby achieving organic degradation and turning food waste into treasure, so this process has gradually received research attention. However, during the anaerobic fermentation process, due to the good acidification performance of food waste, the overall environmental conditions of anaerobic fermentation are difficult to control, and the accumulated fatty acids will further cause changes in the microbial flora, which will have a negative impact on the overall operation of the anaerobic fermentation system. Ultimately, it is difficult to improve the utilization rate of food waste and the yield of fatty acids, especially, it is difficult to increase the content of medium-chain fatty acids in anaerobic fermentation products. Obtaining fatty acids with longer carbon chains can effectively improve the economic value of anaerobic fermentation products. For example, in the prior art, the organic waste slurry is directly fed into an anaerobic fermentation acid production reactor, and anaerobic fermentation is carried out for 7 days at a temperature of 50±0.5°C, a pH value of 6.5±0.05, a stirring speed of 150rpm, and a fermentation organic load of 48kg tVS / m3·d. At this time, the concentration of volatile organic acids (VFA) in the fermentation clear liquid is 10450mg COD / L-17088mg COD / L, and there are still shortcomings such as low substrate utilization and low fatty acid yield. For another example, in the prior art, before putting the food waste into the anaerobic fermentation bottle, the food waste mixture is placed in a reactor with an ultrasonic energy density of 1-1.25 W / mL for ultrasonic pretreatment for 20-30 minutes, and then mixed with the residual sludge, wherein the food waste after ultrasonic pretreatment is mixed with the residual sludge so that the pH value of the fermentation substrate is maintained at 5-6.5, and the loosely structured non-water-soluble organic matter is further dissolved and hydrolyzed after the ultrasonic action, and converted into low-molecular monosaccharides and amino acids, and then converted into short-chain fatty acids, wherein when S / I=6 and the fermentation time is 48 hours, the output of short-chain fatty acids is the largest, which is 967.12 mgCOD / g-VS, and 72.27% of the soluble organic matter in the fermentation liquid is converted into short-chain fatty acids. Although the production and acid production rate of fatty acids can be increased by ultrasonic pretreatment combined with residual sludge, the yield of fatty acids is still low, and medium-chain fatty acids are not obtained or the content is low. At the same time, the additional ultrasonic pretreatment will inevitably increase the complexity of the process, and will also increase energy consumption and production costs. In addition, the above-mentioned acid production method still has defects such as low preparation efficiency and difficulty in accumulating fatty acids in large quantities. For example, the cycle of anaerobic fermentation is usually 7 days, and it is difficult to accumulate more fatty acids by extending the fermentation time. This is because if anaerobic fermentation is continued, organic solid waste will make it difficult to maintain the normal growth of microorganisms, causing the microorganisms to further decompose fatty acids and convert fatty acids into other products, resulting in a decrease in the content of fatty acids; if organic solid waste is added, most of the original activated sludge needs to be removed, and it still takes a long time to activate the sludge, which leads to a longer preparation cycle and lower preparation efficiency.Therefore, how to obtain a preparation method with simple process, low cost, high preparation efficiency, high substrate utilization, high fatty acid yield and high proportion of medium-chain fatty acids is of great significance for further improving the efficiency of food waste treatment and resource utilization, and achieving the reduction and harmless treatment of organic solid waste. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing fatty acids by anaerobic fermentation of organic solid waste, which has simple process, low cost, high preparation efficiency, high substrate utilization rate, high fatty acid yield and high proportion of medium-chain fatty acids.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0006] A method for preparing fatty acids by anaerobic fermentation of organic solid waste comprises the following steps:

[0007] S1. Inoculating activated sludge into an anaerobic reactor and adding organic solid waste for anaerobic fermentation;

[0008] S2. During the anaerobic fermentation process, part of the fermentation product is discharged from the anaerobic reactor, and the discharged fermentation product is subjected to solid-liquid separation to obtain biogas residue; organic solid waste and biogas residue are added to the anaerobic reactor; the volume ratio of the biogas residue to the organic solid waste is 1:6-10;

[0009] S3, repeating step S2, continuing anaerobic fermentation, and completing the treatment of organic solid waste.

[0010] The above method is further improved, in step S2, the volume ratio of the biogas residue to the organic solid waste is 1:7-9.

[0011] The above method is further improved in that in step S2, during the anaerobic fermentation process, after 0.5 to 5 days of anaerobic fermentation, part of the fermentation product is discharged from the anaerobic reactor.

[0012] The above method is further improved in that in step S2, during the anaerobic fermentation process, after 1 to 2 days of anaerobic fermentation, part of the fermentation product is discharged from the anaerobic reactor.

[0013] The above method is further improved, in which in step S2, the fermentation product is discharged from the overflow port at the upper end of the anaerobic reactor; the discharge amount of the fermentation product is the same as the total amount of the biogas residue and organic solid waste added.

[0014] The above method is further improved in that in step S3, the duration of the anaerobic fermentation is ≥ 7 days.

[0015] The above method is further improved in that in step S3, the duration of the anaerobic fermentation is 7 to 40 days.

[0016] The above method is further improved, in which, during the anaerobic fermentation process, when the pH value is lower than 5, a peristaltic pump is used to transport alkali solution to the anaerobic reactor to adjust the pH value until the pH value is 6, and then the transport of the alkali solution is stopped; the flow rate of the peristaltic pump is 1mL / min to 3mL / min; the alkali solution is a sodium hydroxide solution; and the concentration of the alkali solution is 4mol / L.

[0017] The above method is further improved in that the temperature of the reaction system is controlled at 35°C to 40°C and the pH value is controlled at 5.2 to 7.4 during the anaerobic fermentation process.

[0018] The above method is further improved, and in step S1, before adding organic solid waste, it also includes: taming the activated sludge in the anaerobic reactor; the taming is carried out under anaerobic conditions; the temperature of the reaction system is controlled to be 35°C to 40°C during the taming process; the taming time is ≥1 day; the volume ratio of the activated sludge to the organic solid waste is 3000:430, and the organic solid waste is food waste.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] (1) In view of the defects of the existing anaerobic fermentation process, such as difficulty in effectively utilizing substrates, low fatty acid yield, and low preparation efficiency, the present invention creatively proposes a method for preparing fatty acids by anaerobic fermentation of organic solid waste. The method adopts the means of refluxing the fermentation sludge, which can not only realize the full utilization of the substrate, but also significantly improve the yield and accumulation of fatty acids, and significantly improve the content of medium-chain fatty acids. Specifically, the activated sludge and organic solid waste are first fed into an anaerobic reactor for anaerobic fermentation. Then, during the anaerobic fermentation process, a portion of the fermentation product is discharged from the anaerobic reactor at regular intervals. After solid-liquid separation, the obtained sludge is refluxed together with new organic solid waste into the anaerobic reactor. The reflux process is repeated, and the sludge and organic solid waste are continuously added to the anaerobic reactor for anaerobic fermentation. Fermentation, on the one hand, due to the reflux of biogas residue, it can ensure that the sludge at the material entrance has a high activity, and with the progress of anaerobic fermentation, the activated sludge in the biogas residue is continuously domesticated, and the activity of the sludge in the anaerobic reactor is continuously improved, so that the degradation treatment of organic solid waste can be quickly started, and the degradation efficiency of organic solid waste can be continuously improved, thereby significantly improving the production rate of fatty acids, so as to ensure that more fatty acids can be produced in a shorter time, and at the same time, with the continuous improvement of sludge activity, the utilization rate of organic solid waste can also be significantly improved. On the other hand, due to the continuous addition of organic solid waste, they can supplement sufficient carbon sources for the growth of microorganisms, so that during the long fermentation process, the accumulation of fatty acids caused by the consumption of fatty acids by microorganisms can be effectively avoided. On this basis, the volume ratio of organic solid waste to biogas residue is further optimized to 1:6-10 in the present invention, that is, the reflux ratio of biogas residue is 1:6-10. By optimizing the reflux ratio, the formation and accumulation of medium-chain fatty acids can be promoted while ensuring full utilization of substrates and significantly improving the yield and accumulation of fatty acids. In the present invention, after anaerobic fermentation for 7 days, the content of fatty acids can account for more than 60% of soluble COD, at which time the total amount of fatty acids in the fermentation liquid exceeds 20g COD / L, and medium-chain fatty acids can be produced; after anaerobic fermentation for two weeks, the content of fatty acids can reach more than 80% of soluble COD, at which time the total amount of fatty acids in the fermentation liquid exceeds 35g COD / L, and the content of medium-chain fatty acids can account for up to 9.1% of soluble COD. When the anaerobic fermentation is carried out for 30 days, the total amount of fatty acids in the fermentation liquid is as high as 59.921g COD / L.The method of preparing fatty acids by anaerobic fermentation of organic solid waste of the present invention can continuously and efficiently convert organic carbon sources in organic solid waste into fatty acids, and has the advantages of simple process, low cost, high preparation efficiency, high substrate utilization rate, high fatty acid yield and high proportion of medium-chain fatty acids. It can not only broaden the production source of fatty acids and reduce production costs, but also significantly improve the utilization rate of organic solid waste (such as kitchen waste), and provide a new way for efficient resource utilization of organic solid waste, and has a very broad application prospect.

[0021] (2) In the present invention, by optimizing the volume ratio of biogas residue to organic solid waste to 1:7-9, the reflux of biogas residue can make full use of the fermentation substrate, so the volatile fatty acid content in the product fermentation liquid is significantly increased, and medium-chain fatty acids appear. In the existing technology, there are generally two methods for producing fatty acids by anaerobic fermentation. One is to use multiple substrates for long-term anaerobic fermentation to produce acid, for example, a certain amount of organic solid waste is anaerobic fermented for 7 days to produce fatty acids. This technology adds a large amount of organic solid waste at the beginning of fermentation, which seriously damages the fermentation system and reduces the activity of anaerobic sludge, so the fermentation time becomes longer; the second is to add a small amount of substrate in a short period of time for anaerobic fermentation to produce acid, for example, a small amount of organic solid waste is anaerobic fermented for 1 day and then the fermentation product is discharged, and then new organic solid waste is added to the system for fermentation for 1 day, and the cycle is repeated to produce fatty acids. Although this technology overcomes the damage of the fermentation substrate to the system, there is a problem that the amount of fermentation substrate should not be too much, and the small amount of substrate concentration will make the yield unable to achieve the ideal result.

[0022] (3) In the present invention, during the anaerobic fermentation process, when the pH value is lower than 5, the alkali solution is transported to the anaerobic reactor by a peristaltic pump to adjust the pH value until the pH value is 6, and the input of the alkali solution is stopped, wherein the flow rate of the peristaltic pump is 1mL / min~3mL / min. Such a pH adjustment method can not only effectively control the pH value of the system in the anaerobic reactor to 5.2~7.4, but also effectively avoid the reduction of the pH value of the fermentation environment due to the increase in the content of acidic fatty acids, so that the efficiency of anaerobic fermentation to produce fatty acids will not be reduced due to the low pH value. At the same time, by optimizing the flow rate of the peristaltic pump, the pH in the anaerobic reactor can be effectively avoided from increasing sharply, thereby effectively avoiding the adverse effects on the sludge activity caused by the drastic change of the pH value during the pH adjustment process, and thus further improving the production of fatty acids. In addition, in the present invention, the concentration of the alkali solution used is 4mol / L. By using a high concentration of alkali solution to adjust the pH value, the amount of alkali solution added can be reduced, thereby effectively controlling the pH value of the system and effectively avoiding the change of the working volume of the anaerobic reactor, thereby ensuring the continuous progress of anaerobic fermentation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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.

[0024] Figure 1 This is a graph showing the changes in the yield of various fatty acids during the anaerobic fermentation process in Example 1 of the present invention as a function of anaerobic fermentation time.

[0025] Figure 2 This is a graph showing the change in the proportion of various fatty acids during the anaerobic fermentation process in Example 1 of the present invention as the anaerobic fermentation time changes.

[0026] Figure 3 It is a comparison chart of the yields of various fatty acids during anaerobic fermentation at different ratios of kitchen waste to biogas residue in Example 1 of the present invention and Comparative Examples 1-4. DETAILED DESCRIPTION

[0027] 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.

[0028] In the following examples, unless otherwise specified, the materials and instruments used are commercially available.

[0029] Embodiment 1:

[0030] A method for preparing fatty acids by anaerobic fermentation of organic solid waste according to the present invention, specifically preparing fatty acids by anaerobic fermentation of kitchen waste, comprises the following steps:

[0031] S1. Take 3L of activated sludge, which comes from the Kaifu District Sewage Treatment Plant in Changsha City. It is acclimated under anaerobic conditions at 37°C for one day and then inoculated into an anaerobic reactor. It is heated by a jacket arranged on the outer surface of the anaerobic reactor (the jacket is filled with circulating warm water at 37°C) and a heating rod arranged in the anaerobic reactor to adjust the fermentation environment temperature in the anaerobic reactor and stabilize the temperature at 37°C; seal the anaerobic reactor, turn on the stirring device, temperature sensor and pH sensor, add 430mL of food waste from the bottom of the anaerobic reactor, specifically, transport it at a rate of 86mL / min for 5 minutes, and send the food waste into the anaerobic reactor for anaerobic fermentation.

[0032] S2. During the anaerobic fermentation process, after 1 day of anaerobic fermentation, part of the fermentation product is discharged from the overflow port at the top of the anaerobic reactor until the remaining mixture is 3L, and 430mL of the discharged fermentation product is separated into solid and liquid, specifically, by using a filter to obtain filtrate and biogas residue; the biogas residue and food waste obtained in step S1 are added to the anaerobic reactor at a volume ratio of 1:8 to continue anaerobic fermentation, wherein the total amount of biogas residue and food waste added is 430mL.

[0033] S3, repeating step S2, allowing the anaerobic fermentation to continue for 30 days, that is, the anaerobic reactor continues to operate for 30 days to complete the treatment of the kitchen waste.

[0034] In this embodiment, during the anaerobic fermentation process, when the pH of the system in the anaerobic reactor is lower than 5, a peristaltic pump is used to transport a 4 mol / L sodium hydroxide solution to the anaerobic reactor to adjust the pH value until the pH value reaches 6, and then the transport of the sodium hydroxide solution is stopped. During the process of adjusting the pH value using the peristaltic pump, the flow rate of the peristaltic pump is controlled to be 2 mL / min.

[0035] The anaerobic reactor used in the present invention adopts a bottom-in and top-out mode; in order to stabilize the sludge retention time at 8 days, an overflow port is arranged at the position where the liquid level of the anaerobic reactor is 3 liters.

[0036] Figure 1 This is a graph showing the changes in the yield of various fatty acids during the anaerobic fermentation process in Example 1 of the present invention as a function of anaerobic fermentation time. Figure 2 This is a graph showing the change in the proportion of various fatty acids during the anaerobic fermentation process in Example 1 of the present invention as the anaerobic fermentation time changes.

[0037] from Figure 1 and Figure 2 It can be seen that with the continuous progress of anaerobic fermentation, the daily output of fatty acids gradually increased; after 7 days of fermentation, the acetic acid was 6.39g COD / L, the propionic acid was 4.60g COD / L, the isobutyric acid was 0.17g COD / L, the n-butyric acid was 4.18gCOD / L, the isovaleric acid was 0.23g COD / L, the n-valeric acid was 2.26g COD / L, the n-hexanoic acid was 0.95g COD / L, and the n-heptanoic acid was 0.87g COD / L. After 30 days of fermentation, the acetic acid was 11.21g COD / L, the propionic acid was 17.15g COD / L, the isobutyric acid was 0.70g COD / L, the n-butyric acid was 22.27g COD / L, the isovaleric acid was 1.01g COD / L, the n-valeric acid was 5.20g COD / L, the n-hexanoic acid was 1.60g COD / L, the n-heptanoic acid was 0.75g COD / L, and the total fatty acid concentration reached 59.92g COD / L.

[0038] Comparative Example 1:

[0039] A method for preparing fatty acids by anaerobic fermentation of organic solid waste is basically the same as the method in Example 1, except that in step S2, the volume ratio of kitchen waste to biogas residue is 1:2.

[0040] In Comparative Example 1, after anaerobic fermentation for 7 days, acetic acid was 6335.38 mg COD / L, propionic acid was 201.92 mg COD / L, isobutyric acid was 20.97 mg COD / L, n-butyric acid was 829.18 mg COD / L, isovaleric acid was 47.73 mg COD / L, and n-valeric acid was 29.32 mg COD / L.

[0041] Comparative Example 2:

[0042] A method for preparing fatty acids by anaerobic fermentation of organic solid waste is basically the same as the method in Example 1, except that in step S2, the volume ratio of kitchen waste to biogas residue is 1:5.

[0043] In Comparative Example 2, after 7 days of anaerobic fermentation, acetic acid was 9170.47 mg COD / L, propionic acid was 846.91 mg COD / L, isobutyric acid was 53.23 mg COD / L, n-butyric acid was 1051.63 mg COD / L, isovaleric acid was 80.86 mg COD / L, and n-valeric acid was 141.20 mg COD / L.

[0044] Comparative Example 3:

[0045] A method for preparing fatty acids by anaerobic fermentation of organic solid waste is basically the same as the method in Example 1, except that in step S2, the volume ratio of kitchen waste to biogas residue is 1:11.

[0046] In Comparative Example 3, after 7 days of anaerobic fermentation, the acetic acid was 4190.49 mg COD / L, the propionic acid was 1323.05 mg COD / L, the isobutyric acid was 82.19 mg COD / L, the n-butyric acid was 927.09 mg COD / L, the isovaleric acid was 126.74 mg COD / L, and the n-valeric acid was 705.84 mg COD / L.

[0047] Comparative Example 4:

[0048] A method for preparing fatty acids by anaerobic fermentation of organic solid waste is basically the same as the method in Example 1, except that in step S2, the volume ratio of kitchen waste to biogas residue is 1:14.

[0049] In Comparative Example 4, after anaerobic fermentation for 7 days, the acetic acid was 4429.66 mg COD / L, the propionic acid was 1392.46 mg COD / L, the isobutyric acid was 92.67 mg COD / L, the n-butyric acid was 665.85 mg COD / L, the isovaleric acid was 145.65 mg COD / L, and the n-valeric acid was 545.12 mg COD / L.

[0050] Figure 3It is a comparison chart of the yields of various fatty acids during anaerobic fermentation at different ratios of kitchen waste to biogas residue in Example 1 of the present invention and Comparative Examples 1-4. Figure 3 The yields of various fatty acids at 1, 3, 5, and 7 days of anaerobic fermentation under different ratios of food waste to biogas residue. Figure 3 It can be seen that after 7 days of anaerobic fermentation, when the volume ratio of kitchen waste to sludge is 1:8, the output of various fatty acids is greatly increased, and medium-chain fatty acids can be produced within 7 days.

[0051] From the above results, it can be seen that the method of preparing fatty acids by anaerobic fermentation of organic solid waste in the present invention can continuously and efficiently convert the organic carbon source in the organic solid waste into fatty acids, and has the advantages of simple process, low cost, high preparation efficiency, high substrate utilization, high fatty acid yield and high proportion of medium-chain fatty acids. It can not only broaden the production source of fatty acids and reduce production costs, but also significantly improve the utilization rate of organic solid waste (such as kitchen waste), and provide a new way for the efficient resource utilization of organic solid waste, and the application prospect is very broad.

[0052] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing fatty acids by anaerobic fermentation of organic solid waste, characterized in that: The following steps are involved: S1. Inoculating activated sludge into an anaerobic reactor and adding organic solid waste for anaerobic fermentation; S2. During the anaerobic fermentation process, part of the fermentation product is discharged from the anaerobic reactor, and the discharged fermentation product is subjected to solid-liquid separation to obtain biogas residue; organic solid waste and biogas residue are added to the anaerobic reactor; the volume ratio of the biogas residue to the organic solid waste is 1:6-10; S3, repeating step S2, continuing anaerobic fermentation, and completing the treatment of organic solid waste.

2. The method according to claim 1, characterized in that In step S2, the volume ratio of the biogas residue to the organic solid waste is 1:7-9.

3. The method according to claim 1 or 2, characterized in that: In step S2, during the anaerobic fermentation process, after 0.5 to 5 days of anaerobic fermentation, part of the fermentation product is discharged from the anaerobic reactor.

4. The method according to claim 3, characterized in that In step S2, during the anaerobic fermentation process, after 1 to 2 days of anaerobic fermentation, part of the fermentation product is discharged from the anaerobic reactor.

5. The method according to claim 4, characterized in that In step S2, the fermentation product is discharged from the overflow port at the upper end of the anaerobic reactor; the discharge amount of the fermentation product is the same as the total amount of the biogas residue and organic solid waste added.

6. The method according to claim 1 or 2, characterized in that: In step S3, the duration of the anaerobic fermentation is ≥ 7 days.

7. The method according to claim 6, characterized in that In step S3, the duration of the anaerobic fermentation is 7 to 40 days.

8. The method according to claim 1 or 2, characterized in that: During the anaerobic fermentation process, when the pH value is lower than 5, a peristaltic pump is used to transport alkali solution to the anaerobic reactor to adjust the pH value until the pH value reaches 6, and then the transport of the alkali solution is stopped; the flow rate of the peristaltic pump is 1 mL / min to 3 mL / min; the alkali solution is a sodium hydroxide solution; and the concentration of the alkali solution is 4 mol / L.

9. The method according to claim 1 or 2, characterized in that: During the anaerobic fermentation process, the temperature of the reaction system is controlled to be 35° C. to 40° C., and the pH value is 5.2 to 7.

4.

10. The method according to claim 1 or 2, characterized in that: In step S1, before adding organic solid waste, it also includes: taming the activated sludge in the anaerobic reactor; the taming is carried out under anaerobic conditions; the temperature of the reaction system is controlled to be 35°C to 40°C during the taming process; the taming time is ≥1 day; the volume ratio of the activated sludge to the organic solid waste is 3000:430, and the organic solid waste is food waste.

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