Processing method for organic waste

Abstract

To provide a processing method for organic waste and a feeding promoter, by which organic waste can be efficiently converted into feed and fertilizer by feeding the organic waste to insects of the order Diptera.SOLUTION: A processing method for organic waste, in which an object to be treated containing organic sludge generated by biological treatment or organic residue generated by food processing treatment is converted into feed and fertilizer by being fed to insects of the order Diptera, comprises a digestate addition step of adding, to the object to be treated, a digestate generated by anaerobic digestion treatment as a feeding promoter. The processing method further comprises a feeding step of scattering eggs or young larvae of the insects onto the object to be treated to which the digestate has been added, and allowing hatched larvae or the young larvae to feed on the object to be treated.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for treating organic waste, in which a material to be treated, including organic sludge produced in various biological treatments including activated sludge treatment, or organic residues produced in food processing, is fed to Diptera insects to produce fertilizer. [Background technology]

[0002] Patent Document 1 discloses a method for treating organic waste, such as excrement, shochu and beer lees, tofu husks, and raw dust, by feeding the larvae of houseflies (Musca domestica) that have hatched from eggs to convert the waste into organic fertilizer. The method describes that the organic waste covered includes all biodegradable organic waste that can be eaten by housefly larvae, and that the excrement includes not only livestock excrement such as chicken manure, horse manure, and pig manure, but also human excrement.

[0003] Patent Document 2 discloses a method for treating organic waste in which sewage sludge generated in sewage treatment facilities is fed to moth fly larvae to reduce the volume of the sludge and the moth flies are collected as a protein source. It also discloses that other insects, such as chironomids, that grow by eating sludge may be used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-132683 [Patent Document 2] Japanese Patent Publication No. 2021-151647 Summary of the Invention [Problem to be solved by the invention]

[0005] According to Patent Document 1, housefly eggs are scattered on biomass waste such as livestock manure, for example pig manure, and the hatched larvae are made to feed on the biomass waste, causing the larvae to grow.The biomass waste can be reduced in volume through the feeding activity and heat generated by the larvae, and can be used as organic fertilizer, and the grown larvae can be used as feed.

[0006] However, even if housefly eggs are scattered on sewage sludge, which is organic sludge produced by biological treatment, the hatched larvae do not grow sufficiently, making it difficult to efficiently reduce the volume of sewage sludge or use it as feed for the larvae.

[0007] The cause of this phenomenon is not clear, but it is speculated that, unlike pig manure, sewage sludge may contain some substance that inhibits housefly activity, or that it may not contain enough symbiotic bacteria that stimulate housefly activity.

[0008] It has also been confirmed that a similar phenomenon occurs with rice bran, an organic residue produced during food processing.

[0009] In other words, even when the materials to be treated, including organic sludge produced in biological treatment or organic residues produced in food processing, are fed to Dipteran insects, there is a problem in that they cannot always be efficiently used as feed and fertilizer.

[0010] An object of the present invention is to provide a method for treating organic waste, which can efficiently convert organic waste into feed and fertilizer by feeding the organic waste to Diptera insects, and a feeding stimulant. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, a first characteristic feature of the organic waste treatment method according to the present invention is a method for treating organic waste in which a treatment object containing organic sludge produced in biological treatment or organic residues produced in food processing is turned into fertilizer by having Diptera insects feed on it, and the method comprises: a digestive fluid addition step of adding digestive fluid produced in anaerobic digestion to the treatment object; and a feeding step of scattering eggs or young larvae of the insects on the treatment object to which the digestive fluid has been added, and allowing the larvae or young larvae that have hatched from the eggs to feed on the treatment object.

[0012] As a result of extensive testing and research, the inventors of the present application have discovered that by carrying out a digestive fluid addition process in which digestive fluid produced in anaerobic digestion is added to a treatment object containing organic sludge produced in biological treatment or organic residues produced in food processing, good feeding activity of Diptera insects on the treatment object in the feeding process is promoted. As a result, well-grown insects can be obtained as feed material, and the treatment object that has undergone the feeding process can be used as a good fertilizer material.

[0013] The second characteristic feature of the present invention is that, in addition to the first characteristic feature described above, sewage sludge is used as the organic sludge, and Brachyceratops, which includes houseflies, is used as the Diptera insects.

[0014] Even when sewage sludge produced by biological treatment is used as the material to be treated, the process of adding digestive fluid to the sewage sludge promotes good feeding activity by Diptera insects, and in particular promotes significant feeding activity on the sewage sludge by Brachyceratops insects, including houseflies, thereby enabling the sewage sludge to be recycled efficiently.

[0015] The third characteristic configuration is that, in addition to the first or second characteristic configuration described above, the digestive liquid addition step is a step of adjusting the amount of digestive liquid to be added so that the amount of digestive liquid added is 50 parts by weight or more per 100 parts by weight of solid content of the treatment object.

[0016] It has been newly discovered that when carrying out the digestive fluid addition process using sewage sludge as the material to be treated, a better feeding process can be achieved by adding the digestive fluid in an amount of 50 parts by weight or more per 100 parts by weight of the solid content of the material to be treated. Note that if the amount of digestive fluid added is less than 50 parts by weight, the larval production rate will decrease.

[0017] The fourth characteristic feature of the present invention is that, in addition to the second characteristic feature described above, the amount of the eggs or young larvae dispersed in the feeding process is 0.02 to 0.05% by weight relative to the sewage sludge.

[0018] The amount of eggs or young larvae sprayed onto the material to be treated during the feeding process is preferably 0.02 to 0.05% by weight relative to the sewage sludge, which results in good egg hatching rates, larval growth rates, and larval production rates, and promotes volume reduction of the material to be treated through feeding activity, resulting in good feed and fertilizer production. Note that if the spray amount is less than 0.02%, the hatching rate tends to decrease, and although the larvae grow well, their numbers are small, preventing volume reduction of the material to be treated through feeding activity, making good feed and fertilizer production difficult. If the spray amount is more than 0.05%, the number of larvae is too high for the nutrients in the material to be treated, resulting in poor growth and making good feed and fertilizer production difficult.

[0019] The fifth characteristic feature of the present invention is that, in addition to the third characteristic feature described above, the amount of the eggs or young larvae dispersed in the feeding process is 0.02 to 0.05% by weight relative to the sewage sludge.

[0020] By adding the digestive fluid so that the amount of digestive fluid added is 50 parts by weight or more per 100 parts by weight of the solid content of the material to be treated, and by adjusting the amount of eggs to be spread so that the weight ratio to the sewage sludge is in the range of 0.02 to 0.05%, it is possible to promote efficient feed and fertilizer production with a high egg hatching rate, a high larval production rate, and a large volume reduction rate of the material to be treated.

[0021] The sixth characteristic configuration is that, in addition to the first characteristic configuration described above, the method further includes an adjustment step of repeatedly carrying out a unit feed fertilizer treatment consisting of the digestive fluid adding step, the feeding step, and the recovery step on treatment objects of the same origin, and adjusting the amount of digestive fluid added in the digestive fluid adding step and / or the amount of eggs or young larvae scattered in the feeding step in the unit feed fertilizer treatment that is subsequently carried out, based on the yield of the feed fertilizer obtained in the unit feed fertilizer treatment that was previously carried out.

[0022] Even if the origin of the material to be treated is the same, variations in the composition of the material may occur due to various factors, including seasonal fluctuations, and as a result, when the unit feed fertilizer treatment is repeated, the yield and quality of the obtained fertilizer may vary. Even in such cases, by adjusting the amount of digested fluid added in the digested fluid addition step and / or the amount of eggs spread in the feeding step based on the quality and yield of the fertilizer obtained in previous unit feed fertilizer treatments, the quality and yield of the fertilizer obtained each time can be kept stable.

[0023] The feeding stimulant for dipteran insect larvae according to the present invention is characterized in that it contains digestive fluid produced in anaerobic digestion treatment. [Effects of the Invention]

[0024] As described above, according to the present invention, it is possible to provide a method for treating organic waste and a feeding promoter that can efficiently turn organic waste into fertilizer by feeding it to Diptera insects. [Brief explanation of the drawings]

[0025] [Figure 1] 1(a) and 1(b) are flow charts showing the steps of a method for treating organic waste. [Figure 2] 1 is an explanatory diagram of a treatment system that performs a method for treating organic waste. [Figure 3] 1(a) and 1(b) are explanatory diagrams of an organic waste treatment device. [Figure 4]FIG. 1 is a diagram illustrating the characteristics of samples A to E used in Experiment 1 (sewage sludge). [Figure 5] (a) is a characteristic graph of larval production rate showing the results of Experiment 1, (b) is a characteristic graph of larval size showing the results of Experiment 1, and (c) is a characteristic graph of load rate showing the results of Experiment 1. [Figure 6] (a) is a characteristic diagram of the final moisture content of the sample showing the results of Experiment 1, and (b) is a characteristic diagram of the volume reduction rate showing the results of Experiment 1. [Figure 7] FIG. 1 is a diagram illustrating the characteristics of samples A1 to E1 used in Experiment 2 (sewage sludge). [Figure 8] (a) is a characteristic graph of larval production rate showing the results of Experiment 2, (b) is a characteristic graph of larval size showing the results of Experiment 2, and (c) is a characteristic graph of load rate showing the results of Experiment 2. [Figure 9] (a) is a characteristic diagram of the final moisture content of the sample showing the results of Experiment 2, and (b) is a characteristic diagram of the volume reduction rate showing the results of Experiment 2. [Figure 10] FIG. 10 is a diagram illustrating the characteristics of samples A2 to D2 used in Experiment 3 (rice bran). [Figure 11] (a) is a characteristic graph of larvae production volume showing the results of Experiment 3, (b) is a characteristic graph of larvae size showing the results of Experiment 3, and (c) is a characteristic graph of load rate showing the results of Experiment 3. [Figure 12] (a) is a characteristic diagram of the final moisture content of the sample showing the results of Experiment 3, and (b) is a characteristic diagram of the volume reduction rate showing the results of Experiment 3. DETAILED DESCRIPTION OF THE INVENTION

[0026] [Organic waste disposal method] The following describes a method for treating organic waste according to the present invention, specifically a method for treating organic waste by single feeding in which the material to be treated, including organic sludge produced in activated sludge treatment or organic residues produced in food processing, is fed to Diptera insects to turn them into fertilizer, and a feeding promoter.

[0027] Organic sludge produced by biological treatment refers to organic sludge produced when organic wastewater discharged from sewage or food factories is purified by biological treatment. For example, in the case of activated sludge treatment of sewage, this includes not only the excess sludge that settles and separates in the final settling tank after sewage treatment by the activated sludge method, but also mixed sludge with raw sludge that settles and separates in the primary settling tank. It also includes organic sludge that has been digested by anaerobic microorganisms. Organic residues produced in food processing include, for example, rice bran produced in rice milling.

[0028] Insects of the order Diptera refer to insects belonging to the suborder Brachycera, which includes species known as flies and horseflies, and the suborder Nematocera, which includes species known as mosquitoes, midges, and crane flies. In particular, the house fly (Musca domestica), which belongs to the suborder Brachycera, can be suitably used in the present invention.

[0029] Below, we will explain in detail an example in which sewage sludge is used as the material to be treated and houseflies are used as the Diptera insect. As shown in FIG. 1(a), the organic waste treatment method involves sequentially carrying out a digestive fluid addition step (S1), an ingestion step (S2), a recovery step (S3), an insecticide step (S4), and a drying step (S5).

[0030] The digestive fluid addition process (S1) is a process in which the digestive fluid produced in the anaerobic digestion process is added to the material to be treated, and the amount of digestive fluid added to the material to be treated is adjusted within a predetermined range. The feeding process (S2) is a process in which eggs of the housefly, a Diptera insect, are scattered on the material to which the digestive fluid has been added, and the hatched housefly larvae (hereinafter simply referred to as "larvae") feed on the material to be treated, thereby reducing the volume of the material to be treated and promoting the growth of the larvae through their activity and feeding. The feeding process lasts for 5 to 8 days at room temperature of 15 to 35°C.

[0031] The recovery process (S3) utilizes the larvae's tendency to disperse at the end of their final stage of life to recover them from the material to be treated before they metamorphose into pupae. The insecticide process (S4) is a process of killing and sterilizing the larvae recovered in the recovery process using high-temperature water or the like. The drying process (S5) is a process of drying the larvae that have been killed and using them as feed ingredients for livestock and farmed fish, and a process of drying the reduced-volume material to be treated and using them as fertilizer ingredients.

[0032] In the digestion fluid addition step (S1), a small amount of sawdust is mixed with sewage sludge, which is the main component and has been previously separated into solids and liquids at a sewage treatment plant and dehydrated to a moisture content of about 75%, and the digestion fluid extracted from the methane fermentation device is added as a feeding regulator for the larvae, thereby adjusting the properties of the material to be treated. Note that sawdust may be mixed with the sewage sludge prior to the digestion fluid addition step (S1). The mixing of sawdust is intended to prevent the sewage sludge from clumping and to ensure air gaps that allow the larvae to move easily, but is not essential.

[0033] Figure 2 shows an organic sludge treatment system equipped with a sewage treatment facility 1, a methane fermentation unit 5, a treatment unit 10, etc. Organic wastewater that flows into the sewage treatment facility 1 undergoes sedimentation and separation of solid components in a primary sedimentation tank 2, and then undergoes biological treatment with activated sludge in a biological treatment tank 3. The supernatant liquid from which the sludge components have settled in a final sedimentation tank 4 is extracted as treated water, which undergoes disinfection and advanced treatment before being released into a river or used as treated water on-site.

[0034] Of the activated sludge extracted in the final settling tank 4, the excess sludge other than the sludge returned to the biological treatment tank 3 is the organic sludge, which is the treatment target of the present invention. When an MBR method is adopted in which a membrane separation device is immersed in the biological treatment tank 3 instead of the final settling tank 4, the sludge that has undergone solid-liquid separation in the membrane separation device is the organic sludge, which is the treatment target of the present invention.

[0035] Furthermore, the digested liquid extracted from the methane fermentation apparatus 5 after the digestion treatment is subjected to a digested liquid addition step. The methane fermentation apparatus 5 is a treatment apparatus that produces biogas such as methane gas by subjecting organic waste such as food waste and paper waste to methane fermentation treatment under anaerobic conditions.

[0036] The sewage sludge generated in the biological treatment is first dehydrated in a dehydrator to a moisture content of about 80% and then fed into a premixer 6, where it is stirred and mixed with sawdust and digestive fluid to obtain a compositionally adjusted material to be treated. The material to be treated is then fed into a treatment device 10, where housefly eggs are scattered and the feeding process is carried out, and the larvae recovered in the recovery process are killed and sterilized in a larva killing mechanism 16 and then dried in a drying mechanism 18 to become feed material. After the feeding process, the material to be treated is dried in a drying mechanism 19 to become fertilizer material. It is also possible to add feed material to the dried material to make fertilizer material.

[0037] In the digestive fluid addition process, a better feeding process can be achieved by adding the digestive fluid so that the amount of digestive fluid added per 100 parts by weight of the solid content of the material to be treated is in the range of 50 parts by weight or more, more preferably 100 parts by weight or more, and even more preferably 150 parts by weight or more.

[0038] If the amount of digestive fluid added is less than 50 parts by weight per 100 parts by weight of the solid content of the material to be treated, the larval production rate will decrease. There is no particular upper limit on the amount of digestive fluid added to the material to be treated, but if the amount added is too large, the moisture content of the material to be treated will increase, which may create an environment unsuitable for larval growth. When the material to be treated contains organic sludge, the moisture content of a suitable environment for houseflies is approximately 82 to 86%, and it is preferable to add an amount that falls within this moisture content range. The upper limit of the amount added can be, for example, 600 parts by weight or less, 550 parts by weight or less, 500 parts by weight or less, 450 parts by weight or less, or 400 parts by weight or less per 100 parts by weight of the solid content of the material to be treated. When rice bran is used as the organic residue generated in food processing, a moisture content of 68 to 75% is preferred.

[0039] The amount of eggs dispersed during the feeding process is adjusted to a weight ratio of 0.02 to 0.05% relative to the sewage sludge. Adjusting the amount of eggs dispersed so that the weight ratio is within the range of 0.02 to 0.05%, more preferably 0.03 to 0.04%, results in favorable egg hatching rates, larval growth rates, and larval production rates, and promotes volume reduction of the treated material through feeding activity, resulting in favorable feed and fertilizer production. Note that if the amount of eggs dispersed is less than 0.02%, the hatching rate tends to decrease, and although the larvae grow well, their numbers are small, preventing volume reduction of the treated material through feeding activity, making it difficult to achieve favorable feed and fertilizer production. If the amount of eggs dispersed is greater than 0.05%, the number of larvae will be too high relative to the nutrients in the treated material, resulting in poor growth and making it difficult to achieve favorable feed and fertilizer production.

[0040] When young larvae are dispersed instead of eggs during the feeding process, the amount of young larvae dispersed can be adjusted so that the weight ratio of young larvae obtained from the amount of eggs dispersed corresponds to the above-mentioned numerical range, and the numerical range will essentially be the same.

[0041] In the insecticide process, the larvae collected in the collection process are killed and sterilized by boiling them in hot water at 100°C for 10 minutes, and then in the drying process they are dried with hot air at 70°C for 8 hours.In addition, the material to be treated, which has been reduced in volume due to the larvae's feeding activity, is dried with hot air at 68°C for 18 hours in the drying process.

[0042] After the drying process, the larvae are used as feed for pets, livestock, and farmed fish, and as fertilizer for agricultural crops. Because they are rich in protein, they are a useful nitrogen source. Furthermore, because housefly larvae grow in an extremely bacterial environment, they produce unique antibacterial and growth-promoting substances, among other useful compounds, and are used as a raw material for extracting these compounds.

[0043] The material to be treated that has undergone the drying process is utilized as a raw material for fertilizer for agricultural crops, particularly for phosphoric acid and nitrogen. The mixture of the larvae and the material to be treated that has undergone the drying process may also be used as a raw material for fertilizer. In this case, the larvae and the material to be treated can be dried together without recovering the larvae in the recovery process.

[0044] In other words, the organic waste treatment method of the present invention is a method for treating organic waste in which a treatment target containing organic sludge from biological treatment or organic residues from food processing is turned into feed and fertilizer by feeding it to Dipteran insects, and it may include at least a digestive fluid addition step of adding digestive fluid produced by anaerobic digestion to the treatment target, and a feeding step of scattering insect eggs or young larvae on the treatment target to which the digestive fluid has been added and allowing the larvae or young larvae that hatch from the eggs to feed on the treatment target. Furthermore, it is preferable that the method further includes a recovery step of recovering insects from the treatment target before they metamorphose into pupae by utilizing their dispersal habit at the end of their final instar, and that the insects recovered in the recovery step be used as feed material and / or the treatment target ingested by the insects in the feeding step be used as fertilizer material.

[0045] [Configuration of organic waste treatment equipment] 3(a) and (b) show an organic waste treatment device 10 for carrying out the organic waste treatment method described above. The treatment device 10 functions as a housefly rearing facility and includes a box 12 that is rectangular in plan view and has an open top, a larva transport mechanism 14 that is a vibrating transport mechanism, a larva killing mechanism 16, and drying mechanisms 18 and 19.

[0046] The processing device 10 is installed in a roofed building or tent. The box 12 can be made of a suitable material such as a resin material like PET or a metal material like aluminum. In this embodiment, the box has a rectangular shape with long sides of about 2 m and short sides of about 0.8 m, but the material and size can be set as appropriate.

[0047] A plurality of boxes 12 are installed along the larva transport mechanisms 14 so as to straddle the two rows of larva transport mechanisms 14, and a plurality of boxes 12 are stacked on top of each box 12. A pair of inclined surfaces 12a with upwardly sloping edges are formed on the sides of the boxes 12 facing the two rows of larva transport mechanisms 14, and a recess 12b formed between the pair of inclined surfaces 12a is filled in a thin layer with the material to be treated that has undergone the digestive fluid addition step.

[0048] A predetermined amount of housefly eggs are scattered on top of the material to be treated filled in the recess 12b, and the hatched larvae carry out the feeding process. By opening the top of the box 12, an aerobic atmosphere is maintained in which the material to be treated comes into contact with oxygen, and the growth of anaerobic bacteria that cause spoilage is suppressed. Each box 12 is supported by a base 17, and the base 17 is configured to be movable by wheels W. The symbol M represents housefly larvae.

[0049] The larvae M hatched from the eggs grow through a feeding process, and the collection process is carried out by utilizing the dispersal habit of the larvae at the end of the final stage, where they crawl out of the object to be treated just before pupating. That is, the larvae M just before pupating move to the end of each box 12 via a pair of inclined surfaces 12a, and are dropped from the end of each box 12 toward the larva transport mechanism 14 installed below and collected.

[0050] The larvae M that have fallen into the larva transport mechanism 14 are transported to a water tank filled with high-temperature water at 100°C, which serves as the larva killing mechanism 16, and boiled for a predetermined time to kill and sterilize the larvae. Thereafter, the larvae are caught with a net and put into the drying mechanism 18 for drying.

[0051] The organic waste treatment method of the present invention is completed by the feed and fertilizer treatment, which consists of a series of processes from the digested liquid addition step (S1) to the drying step (5) shown in Figure 1(a). Thereafter, the feed and fertilizer treatment is repeated with new organic waste. Even organic waste from the same origin does not always have consistent properties, and the yield of the resulting feed and fertilizer raw materials varies.

[0052] FIG. 1(b) shows an example of an organic waste treatment method in which an evaluation step (S7) and an adjustment step (S8) are carried out, followed by repeated feed and fertilizer treatment, to ensure stable treatment of such organic waste.

[0053] In the evaluation step (S7), the yield and properties of the feed and fertilizer obtained in the feed and fertilizer process carried out in the past are evaluated, and based on the evaluation results, an adjustment step (S8) is carried out to adjust the amount of digestive fluid added in the digestive fluid addition step and / or the amount of eggs scattered in the feeding step in the feed and fertilizer process to be carried out subsequently. [Example]

[0054] An experimental example of the treatment for making fertilizer using sewage sludge as the material to be treated will be described below. [Experimental Example 1] Samples A to E were prepared by mixing different amounts of digestive juice into a mixture of sewage sludge (solids content 22.3% by weight), the material to be treated, and sawdust. A fixed amount of housefly eggs was sprayed onto each of Samples A to E, and the larvae production rate, larvae size, hatching rate, final fertilizer moisture content, and volume reduction rate were measured from the first day of spraying until seven days later. A rectangular box measuring 19 cm x 27 cm, smaller than the box described above, was prepared and each sample was filled in layers. Sample N was a sample to which no digestive juice was added.

[0055] Figure 4 shows the composition of samples A to E, Figure 5(a) shows the larvae production rate, Figure 5(b) shows the larvae size, Figure 5(c) shows the hatching rate, Figure 6(a) shows the moisture content of the final fertilizer (samples after 7 days), and Figure 6(b) shows the volume reduction rate.The larvae production rate is the ratio calculated by (total live weight of collected larvae) / (weight of sewage sludge applied), the hatching rate is the ratio calculated by (total number of collected larvae) / (total number of housefly eggs spread), and the volume reduction rate is the ratio calculated by (total weight of initial sample - total weight of final fertilizer) / (total weight of initial sample).

[0056] With a constant amount of housefly eggs scattered, the larval production rate and size of the housefly larvae used as feed were greatest for sample D, and a tendency for these to decrease whether the amount of digestive juice added was increased or decreased compared to sample D was confirmed. No significant correlation was observed between the hatching rate and the amount of digestive juice added. No larvae grew in sample N. The changes in the final fertilizer moisture content and volume reduction rate are simply the result of drying in a stationary state.

[0057] When the amount of housefly eggs scattered was constant, the volume reduction rate of the material to be treated as fertilizer correlated with the amount of digestive fluid added, and the volume reduction rate tended to decrease as the amount of digestive fluid mixed in increased. In other words, it is estimated that the more digestive fluid added, the more active the feeding activity becomes.

[0058] When the material to be treated contains organic sludge, in order to provide a suitable environment for houseflies, the upper limit of the moisture content of the material to be treated after the addition of the digestive fluid is preferably 85.5%, and more preferably 85%. The lower limit of the moisture content of the material to be treated after the addition of the digestive fluid is preferably 82%, and more preferably 83.0%, and even more preferably 84.0%.

[0059] In addition, to compare the composition with Sample A, an experiment was conducted under the same conditions using a sample to which 200 ml of water was added instead of the 200 ml of digestive fluid. It was found that the larval production rate was significantly lower than that of Sample A, and the size of the larvae was also significantly smaller.

[0060] [Experimental Example 2] Samples A1 to F1 were prepared by scattering different amounts of housefly eggs on a mixture of sewage sludge (solid content 26.4% by weight) and sawdust to which a certain amount of digestive fluid was added, and the larvae production rate, larvae size, hatching rate, final fertilizer moisture content, and volume reduction rate were measured from the first day of scattering until seven days later.

[0061] Based on the results of Experimental Example 1, samples A1 to F1 were prepared by keeping the composition of the treatment object constant and varying the amount of eggs sprayed so that the moisture content of the treatment object was approximately equal to that of sample D, and the larvae production rate, larvae size, hatching rate, final fertilizer moisture content, and volume reduction rate were measured from the first day of spraying until 7 days had passed.

[0062] Figure 7 shows the composition of samples A1 to F1, which had different egg application rates, Figure 8(a) shows the larval production rate, Figure 8(b) shows the larval size, Figure 8(c) shows the hatching rate, Figure 9(a) shows the final fertilizer moisture content, and Figure 9(b) shows the volume reduction rate.

[0063] The larval production rate was highest for sample E1, which had an egg application rate of 0.18 g, and it was confirmed that the size of the larvae tended to decrease as the egg application rate increased. Furthermore, a lower egg application rate tended to result in a lower hatching rate. Consequently, it is considered preferable for the egg application rate to be in the range of 0.02 to 0.05% by weight relative to the sewage sludge, and more preferably in the range of 0.03 to 0.04%.

[0064] [Description of another embodiment] The above-described embodiment has been described as an example in which sewage sludge is used as the organic sludge produced by activated sludge treatment and houseflies are used as the dipteran insects, but the present invention is not limited to sewage sludge and can be widely applied to organic wastes that do not allow dipteran insects to feed effectively on the organic waste alone, regardless of moisture content, such as organic sludge produced by biological treatment including activated sludge treatment and organic residues produced by food processing.

[0065] As explained above, when feeding the material to be treated, including organic sludge produced by biological treatment, to the larvae of dipteran insects, the digestive fluid produced by the anaerobic digestion process can be suitably used as a feeding promoter.

[0066] Experiment 3 confirmed that rice bran (solid content: 87.2% by weight) can be used as an example of organic residue generated during food processing. As shown in Figure 10, a comparative experiment was conducted on rice bran (samples A2 and C2) whose moisture content had been adjusted to a predetermined level by mixing sawdust and water, and rice bran (samples B2 and D2) whose moisture content had been adjusted to a predetermined level by mixing sawdust and digested fluid. As shown in Figures 11(a)-(c) and 12(a) and (b), it was confirmed that samples B2 and D2 were significantly better in terms of larvae production, larvae size, hatching rate, and final fertilizer moisture content. There was no change in the volume reduction rate.

[0067] Furthermore, the present invention is not limited to house flies and can be widely applied to Diptera insects, and can suitably employ Brachyceratops insects including house flies and American soldier flies. When house flies are employed, they can be treated more efficiently because they require only a single feeding and the feeding process takes a shorter period of about 7 to 10 days than American soldier flies, which require additional feeding and the feeding process takes a longer period of about one month. [Explanation of symbols]

[0068] 1: Sewage treatment facility 5: Methane fermentation equipment 10: Biological treatment equipment 12: Box body 14: Larva transport mechanism 16: Larvicidal mechanism 18:Drying mechanism

Claims

1. A method for treating organic waste, in which a treatment target containing organic sludge produced in biological treatment or organic residues produced in food processing is turned into fertilizer by feeding it to Diptera insects, comprising: a digestion liquid adding step of adding digestion liquid produced by anaerobic digestion treatment to the treatment target; a feeding step of scattering eggs or young larvae of the insects on the treatment object to which the digestive fluid has been added, and allowing the larvae or young larvae hatched from the eggs to feed on the treatment object; A method for treating organic waste, comprising:

2. 2. The method for treating organic waste according to claim 1, wherein sewage sludge is used as the organic sludge and Brachyceratops including houseflies is used as the Diptera insects.

3. 3. The organic waste treatment method according to claim 1, wherein the digestive liquid addition step is a step of adjusting the amount of digestive liquid added so that the amount of digestive liquid added per 100 parts by weight of solids of the material to be treated is 50 parts by weight or more.

4. 3. The method for treating organic waste according to claim 2, wherein the amount of the eggs or young larvae dispersed in the feeding step is 0.02 to 0.05% by weight relative to the sewage sludge.

5. 4. The method for treating organic waste according to claim 3, wherein the amount of the eggs dispersed in the feeding step is 0.02 to 0.05% by weight relative to the sewage sludge.

6. 2. The organic waste treatment method according to claim 1, further comprising an adjustment step of: repeating a feed and fertilizer treatment process to obtain feed and fertilizer raw materials by performing the digestive liquid addition step and the feeding step on materials to be treated of the same origin; and adjusting the amount of digestive liquid added in the digestive liquid addition step and / or the amount of eggs or young larvae spread in the feeding step in a feed and fertilizer treatment process to be subsequently performed, based on the yield of the feed and fertilizer raw materials obtained in a feed and fertilizer treatment process previously performed.

7. A feeding stimulant for dipteran insect larvae containing digestive fluid produced during anaerobic digestion.

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