A method for recycling perishable organic solid waste

Abstract

The present invention discloses a method for resource utilization of perishable organic solid waste, which is used for solid waste treatment and resource utilization. The method provided by the present invention comprises the following steps: S1. thermally hydrolyzing municipal sludge and restaurant waste respectively to obtain municipal sludge thermal hydrolysis clear liquid and restaurant waste thermal hydrolysis clear liquid; S2. mixing the municipal sludge thermal hydrolysis clear liquid and the restaurant waste thermal hydrolysis clear liquid to obtain fungal culture liquid; S3. culturing multicellular fungi in the fungal culture liquid to obtain mycelium fiber. The method provided by the present invention can effectively improve the resource utilization efficiency of perishable organic solid waste, that is, significantly improve the effective utilization rate of COD therein and increase the growth amount of mycelium fiber.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste treatment and resource utilization, and in particular to a method for resource utilization of perishable organic solid waste. Background Art

[0002] Municipal sludge and restaurant kitchen waste are typical urban perishable organic solid wastes, with high water content, rich organic matter content, easy to decompose and cause secondary pollution, large output and continuous growth, etc., which have become one of the most important and persistent urban environmental problems. At the same time, the organic matter contained in municipal sludge and restaurant kitchen waste is an important resource. If it can be fully utilized, it will bring significant economic benefits.

[0003] At present, the treatment of municipal sludge and food waste is still mainly carried out separately. Incineration, landfill and anaerobic digestion are mainly used for sludge, and anaerobic fermentation and biogas recovery after drying and oil extraction are mainly used for food waste. In other words, the above-mentioned treatment methods for municipal sludge and food waste are mainly to recover energy substances, such as biogas, and the resource grade is relatively low.

[0004] There are also technologies that attempt to improve the resource quality of municipal sludge and food waste, such as fermentation to produce alcohol, mycelium and other products, but there are many problems in the resource process: municipal sludge is difficult to dewater, the conversion efficiency of organic matter in the biological transformation process is low, and the fermentation cycle is long; food waste is easily inhibited by acidification; the above technical bottlenecks have limited the improvement of the resource level of sludge and food waste.

[0005] Therefore, how to improve the resource utilization efficiency of perishable organic solid waste such as municipal sludge and food waste is an issue that needs to be focused on in the solid waste treatment process. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a method for resource utilization of perishable organic solid waste, which can effectively improve the resource utilization efficiency of perishable organic solid waste, that is, significantly improve the COD utilization rate therein and increase the growth of mycelium fiber.

[0007] According to an embodiment of the first aspect of the present invention, a method for recycling perishable organic solid waste is provided, the method comprising the following steps:

[0008] S1. Thermally hydrolyze municipal sludge and food waste to obtain a clear solution of thermal hydrolysis of municipal sludge and a clear solution of thermal hydrolysis of food waste;

[0009] S2. Mixing the municipal sludge thermal hydrolysis liquid and the kitchen waste thermal hydrolysis liquid to obtain a fungal culture solution;

[0010] S3. Cultivating multicellular fungi in the fungal culture solution to obtain hyphae fibers.

[0011] The method according to the embodiment of the present invention has at least the following beneficial effects:

[0012] (1) The present invention can promote the dehydration of municipal sludge and the release of organic matter after the municipal sludge and restaurant kitchen waste are subjected to thermal hydrolysis respectively, thereby improving the dehydration performance of municipal sludge and the biodegradability of organic matter, wherein the improvement of dehydration performance is beneficial to the post-treatment process of municipal sludge; the thermal hydrolysis treatment of restaurant kitchen waste can enhance the separation effect of oil and fat and the resource utilization of organic matter by quality and phase separation. Since the post-treatment methods of restaurant kitchen waste and municipal sludge are different, the former can also be used for solid fermentation to produce high-value chemicals such as biogas, ethanol, and lactic acid, and the latter can be used in agriculture as a bio-based fertilizer. Therefore, the present invention adopts separate thermal hydrolysis treatment methods, and can carry out reuse according to the material characteristics of the residual solid phase product of thermal hydrolysis. Furthermore, since the components in municipal sludge and restaurant kitchen waste are different, the thermal hydrolysis treatment conditions are different, and if mixed thermal hydrolysis is performed, unnecessary energy consumption will occur between municipal sludge and restaurant kitchen waste, and excessively high temperature will easily cause a violent Maillard reaction in restaurant kitchen waste, reducing the biodegradability of restaurant kitchen waste. Therefore, considering the differences in material properties, different post-processing and recycling methods, energy consumption and utilization, etc., the present invention adopts a method of separate thermal hydrolysis.

[0013] (2) Generally, the pH of the supernatant from the thermal hydrolysis of municipal sludge is higher than the pH required for fungal culture, while the pH of the supernatant from the thermal hydrolysis of food waste is lower than the pH required for fungal culture. In the present invention, the two are mixed and used, and the pH of the resulting fungal culture solution can meet the conditions for fungal culture without the need for excessive pH adjustment.

[0014] Generally, municipal sludge thermal hydrolysis supernatant is rich in nitrogen, with a C / N ratio of 3.3 to 3.8; food waste thermal hydrolysis supernatant is rich in carbon, with a C / N ratio of 40 to 82; and fungal culture requires a suitable C / N; therefore, the present invention mixes municipal sludge thermal hydrolysis supernatant and food waste thermal hydrolysis supernatant for use, adjusts the C / N ratio of the fungal culture solution, and makes it more suitable for fungal culture, compared with using municipal sludge thermal hydrolysis supernatant or food waste thermal hydrolysis supernatant as the fungal culture solution alone, the fungal culture solution components used in the present invention have a synergistic effect, optimize the biological transformation environment, and significantly improve the growth of mycelium and the effective utilization rate of COD.

[0015] (3) The product obtained by the present invention is mycelium fiber, which overcomes the current problem of single product in the bioconversion of perishable organic solid waste into biogas. At the same time, mycelium fiber can be used as raw material for further processing such as paper-based materials, packaging materials, leather, carbon-based electrode precursors, etc., which can significantly increase the added value of the resource utilization of municipal sludge and food waste.

[0016] According to some embodiments of the present invention, the solid content of the municipal sludge used in the thermal hydrolysis is 6%-15%, for example, about 8%.

[0017] According to some embodiments of the present invention, in step S1, the thermal hydrolysis temperature of the municipal sludge is 140-170° C., and the duration is 1.0 to 2.0 h.

[0018] The thermal hydrolysis process of the municipal sludge requires cell disruption to promote the release of organic matter, which is difficult, so the temperature required for thermal hydrolysis is relatively high.

[0019] Specifically, the thermal hydrolysis temperature of the municipal sludge may be about 160°C.

[0020] According to some embodiments of the present invention, in step S1, the method of obtaining the municipal sludge thermal hydrolysis supernatant comprises centrifugation.

[0021] The centrifugal rotation speed is 5000-12000 rpm.

[0022] The centrifugation time is 5 to 20 minutes, for example, about 10 minutes.

[0023] Thus, the thermal hydrolysis product of the municipal sludge can be separated into solid and liquid.

[0024] According to some embodiments of the present invention, step S1 further includes crushing the food waste before the thermal hydrolysis. This can reduce the particle size of the food waste and improve the dissolution rate of the effective ingredients in the thermal hydrolysis process. On the other hand, after crushing, the food waste is slurried, which is convenient for weighing and adjusting the solid content.

[0025] According to some embodiments of the present invention, in step S1, the COD concentration in the municipal sludge thermal hydrolysis clear liquid is 10-20 g / L, for example, specifically about 16 g / L.

[0026] It is understandable that in order to avoid damaging the crushing equipment, hard objects in the food waste need to be removed before the crushing.

[0027] According to some embodiments of the present invention, the crushing is performed in a high-speed crusher.

[0028] During the crushing process, the rotation speed of the high-speed crusher is 10000-30000 rpm. For example, the specific rotation speed may be about 20000 rpm.

[0029] The duration of the crushing is 10 to 20 minutes, for example, specifically about 10 minutes.

[0030] According to some embodiments of the present invention, the solid content of the food waste used for the thermal hydrolysis is 6% to 15%. If the solid content of the crushed food waste is within the above range, the thermal hydrolysis can be directly performed; if the solid content is higher than the above range, water needs to be added for dilution. The solid content of the food waste can specifically be about 8%.

[0031] According to some embodiments of the present invention, in step S1, the thermal hydrolysis temperature of the kitchen waste is 90-130°C, and the duration is 1.0-2.0 hours. The thermal hydrolysis temperature of the kitchen waste is about 120°C.

[0032] Compared with the municipal sludge, the thermal hydrolysis of the food waste does not require cell disruption, and the dissolution of components such as organic matter is easier, so the thermal hydrolysis temperature can be lower than the thermal hydrolysis temperature of the municipal sludge.

[0033] According to some embodiments of the present invention, the method for obtaining the supernatant of the thermal hydrolysis of the food waste comprises centrifuging and separating the thermal hydrolysis product of the food waste.

[0034] Thus, the thermal hydrolysis products of the food waste form three layers of incompatible parts, namely, the food waste thermal hydrolysis clear liquid, grease and solid residue.

[0035] The thermal hydrolysis process promotes the dissolution and separation of fats in kitchen waste, and the obtained fats can be directly used as fuel, or as raw materials for the preparation of lubricating oil and engine oil, which further improves the economic efficiency of the reuse of the perishable organic solid waste.

[0036] The COD concentration of the obtained food waste thermal hydrolysis clear liquid is 90 to 110 g / L, for example, specifically about 100 g / L.

[0037] The centrifugation of the thermal hydrolysis product of the food waste has a rotation speed of 5000 to 14000 rpm, for example, specifically about 12000 rpm.

[0038] The centrifugation time of the thermal hydrolysis product of the kitchen waste is 5 to 20 minutes, for example, about 10 minutes.

[0039] According to some embodiments of the present invention, step S2 further includes diluting the municipal sludge thermal hydrolysis clear liquid or the food waste thermal hydrolysis clear liquid before the mixing so that the COD concentrations of the two are the same. It can be seen that the mixing in step S2 is actually the mixing of the municipal sludge thermal hydrolysis clear liquid and the food waste thermal hydrolysis clear liquid after adjusting the COD concentration, and the mixing ratio is also calculated according to the volume after dilution.

[0040] The fungal culture solution obtained by the dilution and mixing does not need to adjust the pH, etc., to avoid excessive consumption of other chemical reagents.

[0041] According to some embodiments of the present invention, the COD concentration of the fungal culture solution is 10000-25000 mg / L, for example, specifically about 16000 mg / L.

[0042] According to some embodiments of the present invention, in step S2, the volume percentage of the hot hydrolysis liquid of the kitchen waste in the fungal culture liquid is 20-80%.

[0043] According to some embodiments of the present invention, in step S2, the volume percentage of the hot hydrolyzed liquid of food waste in the fungal culture liquid is 25-75%, for example, specifically about 50%.

[0044] According to some embodiments of the present invention, step S3 further includes sterilizing the fungal culture solution before the culturing.

[0045] According to some embodiments of the present invention, in step S3, the multicellular fungus includes at least one of Aspergillus niger, Rhizopus australis and Aspergillus flavus.

[0046] According to some embodiments of the present invention, in step S3, the culturing method is shaking culture.

[0047] The shaking speed of the shaking culture is 100-200 rpm, for example, specifically about 150 rpm.

[0048] According to some embodiments of the present invention, in step S3, the culture temperature is 25-35°C. For example, it can be about 28°C.

[0049] According to some embodiments of the present invention, in step S3, during the culturing process, the dissolved oxygen concentration is 0.5-3.0 mg / L.

[0050] According to some embodiments of the present invention, in step S3, the culturing time is 2 to 5 days.

[0051] According to some embodiments of the present invention, in step S3, during the culturing process, the pH of the system is 3.5-7.0.

[0052] According to some embodiments of the present invention, in step S3, the method for obtaining the mycelium fibers includes performing solid-liquid separation on the cultured product. The method for performing solid-liquid separation on the cultured product includes filtration, specifically including at least one of ordinary filtration and vacuum filtration; the mesh aperture used in the filtration is 0.1 to 0.4 mm. The filtration is performed under water flushing conditions, thereby the obtained mycelium fibers can be cleaned simultaneously during the filtration process and the filtration efficiency can be improved.

[0053] According to some embodiments of the present invention, obtaining the mycelium fibers further comprises drying the obtained solid product after solid-liquid separation; and the drying of the mycelium fibers comprises at least one of freeze drying or medium-temperature drying.

[0054] According to some embodiments of the present invention, the mycelium fibers can be used as raw materials for paper-based materials, packaging materials, leather, and carbon-based electrodes.

[0055] If there is no special explanation, the actual meaning of “about” in the present invention is that the error is allowed to be within the range of ±2%, for example, about 100 is actually 100±2%×100.

[0056] Unless otherwise specified, “between” in the present invention includes the number itself, for example, “between 2 and 3” includes the endpoint values ​​2 and 3.

[0057] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0059] Figure 1 It is a schematic diagram of a flow chart of an embodiment of the present invention.

[0060] Figure 2 This is a graph showing the change in mycelial fiber biomass over culture time in Example 1 of the present invention.

[0061] Figure 3 It is a graph showing the change of mycelial fiber biomass with culture time in Example 1 of the present invention and Comparative Examples 1-2.

[0062] Figure 4 It is a comparison of the actual measured biomass and the weighted biomass when cultured for 36 hours in Example 1 of the present invention and Comparative Examples 1-2.

[0063] Figure 5 It is the effective conversion rate of COD when cultured for 36 hours in Example 1 of the present invention and Comparative Examples 1-2. DETAILED DESCRIPTION

[0064] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0065] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0066] Example 1

[0067] This embodiment provides a method for recycling perishable organic solid waste. The specific process is as follows: Figure 1 As shown, the specific steps are:

[0068] S1. Thermal hydrolysis of municipal sludge: The municipal sludge with a solid content of about 6% was thermally hydrolyzed at 160°C for 1 hour and then centrifuged at a speed of 12000rpm for 10 minutes to obtain the municipal sludge thermal hydrolysis clear liquid; the remaining solid residue was collected for later use. The COD concentration of the municipal sludge thermal hydrolysis clear liquid was 16g / L.

[0069] Thermal hydrolysis of food waste: After removing the hard objects, the food waste is crushed by a high-speed crusher, wherein the speed of the high-speed crusher is 20000rpm, and the crushing time is 10min. The crushed food waste is diluted with water to a solid content of about 15wt.%, and then thermal hydrolysis is carried out at 120℃ for 1h. After thermal hydrolysis, the food waste is separated into three phases by centrifugation, the centrifugal speed is 12000rpm, and the centrifugal time is 10min, and the grease and food waste thermal hydrolysis clear liquid are recovered. Among them, the COD of the food waste thermal hydrolysis clear liquid is about 100g / L.

[0070] S2. Dilute the hot hydrolysis liquid of kitchen waste obtained in step S1 with water until the COD is diluted to 16 g / L, and then mix it with the hot hydrolysis liquid of municipal sludge obtained in step S1. Prepare three mixed solutions according to the volume ratio of the diluted hot hydrolysis liquid of kitchen waste to the hot hydrolysis liquid of municipal sludge (referred to as sludge: kitchen in the attached figure) of 1:3, 2:2 and 3:1 respectively, and sterilize the obtained mixture as fungal culture solution. S3. Cultivate fungi in the fungal culture solution obtained in step S2, the strain is Aspergillus niger, and culture at 28°C with an oscillation frequency of 150 rpm for 5 days.

[0071] Comparative Example 1

[0072] This comparative example provides a method for recycling perishable organic solid waste, which is different from Example 1 in that:

[0073] In step S2, the fungal culture solution only includes the diluted food waste thermal hydrolysis supernatant, that is, the volume ratio of the food waste thermal hydrolysis supernatant to the municipal sludge thermal hydrolysis supernatant is 4:0.

[0074] Comparative Example 2

[0075] This comparative example provides a method for recycling perishable organic solid waste, which is different from Example 1 in that:

[0076] In step S2, the fungal culture solution only includes the supernatant liquid of thermal hydrolysis of municipal sludge, that is, the volume ratio of the supernatant liquid of thermal hydrolysis of food waste to the supernatant liquid of thermal hydrolysis of municipal sludge is 0:4.

[0077] Test Case

[0078] This test example tests the mycelial fiber biomass at different times in the example and comparative examples 1 to 2. The results show that during the cultivation process of Example 1, the mycelial fiber biomass (the mass of dry mycelial fibers grown per liter of fungal culture solution) reaches a peak value within 36 to 48 hours, and the mycelial fiber biomass within the same time period increases with the increase in the content of the hot hydrolysis clear liquid of food waste in the fungal culture solution. Since the mycelial fiber biomass in Example 1 reaches a peak value at 36 hours, this test example also tests the range of changes in mycelial fiber over time within 36 hours in comparative examples 1 to 2. The test results show that the peak yield of mycelial fiber biomass in Example 1 is significantly higher than that in comparative example 2, and is equal to that in comparative example 1. This shows that the present invention, by mixing the hot hydrolysis clear liquids of two perishable organic solid wastes, at least significantly improves the COD utilization rate in the hot hydrolysis clear liquid of municipal sludge. It should be noted that, since the content of biodegradable nutrients in the supernatant of hot hydrolysis of food waste is higher than that in the supernatant of hot hydrolysis of municipal sludge, the mycelial fiber biomass in Comparative Example 1 may remain unchanged or increase to a certain extent as the culture time increases. Figures 2-3 The results for 36 h are shown in Table 1.

[0079] Table 1 Mycelial fiber biomass (36h) in Example 1 and Comparative Examples 1-2

[0080]

[0081] In order to further reflect the synergistic effect between the thermal hydrolysis supernatants of the two perishable organic solid wastes in the present invention, the present invention also compares the measured value and weighted calculated value of the mycelial fiber biomass at 36 hours in Example 1, wherein the weighted calculated value is calculated based on the mycelial fiber biomass of Comparative Examples 1 and 2 when cultured for 36 hours. For example, in Comparative Examples 1 to 2, the mycelial fiber biomass at 36 hours is x and y, respectively. Then, when mud: kitchen = 3:1, the weighted calculated value is 0.75y + 0.25x. The test results show that in the method provided by the present invention, when mud: kitchen = 3:1, 2:2 and 1:1, the measured value of the mycelial fiber biomass is 43.1%, 21.3% and 23.3% higher than the corresponding weighted calculated value, respectively. This indicates that in the method provided by the present invention, a significant synergistic effect occurs between the thermal hydrolysis supernatants of the two perishable organic solid wastes. The result comparison diagram is shown in FIG. Figure 4 shown.

[0082] Furthermore, this test example also tested the COD effective conversion rate in the fungal culture solution in the embodiment and comparative examples 1 to 2, wherein the COD equivalent of the mycelium (COD 菌体 ) is 1.31 times the dry weight of mycelial fiber, COD 去除 is the amount of COD removed from the fungal culture solution. The results show that when the ratio of sludge to kitchen waste is 3:1, the COD effective conversion rate is the highest, about 59%, which is significantly higher than 55% in Comparative Example 1 and 44% in Comparative Example 2. This further illustrates that in the method provided by the present invention, the use of the municipal sludge thermal hydrolysis clear liquid and the food waste thermal hydrolysis clear liquid is mixed, which significantly improves the utilization rate of COD in the fungal culture solution by fungi, and an unexpected synergistic effect is produced between the two. The specific test results are as follows Figure 5 shown.

[0083] In summary, the method of the present invention can effectively utilize the easily perishable organic solid waste municipal sludge and restaurant kitchen waste, significantly improve the added value of the resource utilization of municipal sludge and restaurant kitchen waste, and overcome the deficiency of methane as the main product of the current bioconversion. In addition, the thermal hydrolysis clear liquid of municipal sludge and restaurant kitchen waste produces a significant synergistic effect, which is more conducive to the growth of mycelial fibers and the effective utilization of COD.

[0084] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for recycling perishable organic solid waste, characterized in that: The method comprises the following steps: S1. Thermally hydrolyze municipal sludge and food waste to obtain a clear solution of thermal hydrolysis of municipal sludge and a clear solution of thermal hydrolysis of food waste; The thermal hydrolysis temperature of the municipal sludge is 140-170°C and the duration is 1.0-2.0h; The thermal hydrolysis temperature of the kitchen waste is 90-130° C., and the duration is 1.0-2.0 h; S2. Mixing the municipal sludge thermal hydrolysis liquid and the kitchen waste thermal hydrolysis liquid to obtain a fungal culture solution; S3. Cultivating multicellular fungi in the fungal culture solution to obtain hyphae fibers.

2. The method according to claim 1, characterized in that Step S2 also includes diluting the municipal sludge thermal hydrolysis clear liquid or the food waste thermal hydrolysis clear liquid before the mixing so that the COD concentrations of the two are the same.

3. The method according to claim 1 or 2, characterized in that: The COD concentration of the fungal culture solution is 10000-25000 mg / L.

4. The method according to claim 1 or 2, characterized in that: In step S2, the volume percentage of the hot hydrolyzed liquid of the kitchen waste in the fungal culture solution is 20-80%.

5. The method according to claim 4, characterized in that In step S2, the volume percentage of the hot hydrolyzed liquid of the kitchen waste in the fungal culture solution is 25-75%.

6. The method according to claim 1 or 2, characterized in that: In step S3, the multicellular fungus includes at least one of Aspergillus niger, Rhizopus australis and Aspergillus flavus.

7. The method according to claim 1 or 2, characterized in that: In step S3, the culture temperature is 25-35°C.

8. The method according to claim 1 or 2, characterized in that: In step S3, the culturing time is 2 to 5 days.

Images