JP2009234855A - Method of composting organic waste substance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of composting organic waste substances by which the stripping conditions can be easily controlled when ammonia contained in the organic waste substances is removed so as to effectively prevent the occurrence of offensive odor that is one of problems in a composting process of the organic waste substances by a subsequent field heaping system. <P>SOLUTION: The method of composting the organic waste substances includes: a first treating step S1 comprising accommodating an organic waste substance into a treating tank 10 having an agitation means 15 therein and capable of being closed, then liberating ammonia contained in the organic waste substance by exposing the organic waste substance at a pH of 7.5-9.5 and a temperature of 85-120°C for 20 min to 3 h, and previously stripping a prescribed amount of ammonia by steam generated in the treating tank 10 or air or steam supplied from outside; and a second treating step S2 for composting the organic waste substance subjected to the first treatment by microorganism. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for composting organic waste, and more particularly, to a method for composting organic waste that uses microorganisms to compost organic waste.

  Composting technology is recognized as a mature technology that converts livestock waste, municipal waste waste and organic waste such as sewage sludge into usable fertilizers and soil amendments. It can also be said that this is a preferable technique. It is known that various microorganisms are involved in the process of decomposing, humifying and producing good quality compost of these organic wastes. For the sustainable use of organic waste, which is a raw material for compost, it is necessary to control pathogenic microorganisms in the raw material, and other means to avoid other problems related to human health It is very important to take

  In particular, when compost is manufactured based on raw materials made from livestock waste such as cattle, pigs, and bird manure, the composting process based on the pile-up method can cause illness or mental illness due to bad odor. It is known to have serious consequences for worsening health due to unpleasant discomfort. Of course, it has been reported that long-term exposure to the stimulating odorous components that occur during the composting process can cause bronchitis. It can be said that they are forced to take physical damage. Odor components generated in the composting process using livestock waste include ammonia, volatile fatty acids, indoles, sulfide compounds, and amines. Ammonia accounts for the main odor components, and countermeasures have been taken. It is important to take. However, livestock waste contains the essential elements necessary for agricultural crops in a well-balanced manner, and is known to be a raw material for organic materials that can be used as good compost.

  In addition, in European countries, ammonia gas generated during field reduction, incineration and composting of livestock waste is a major source of ammonia gas in the atmosphere. It is also reported that it is oxidized in the soil by including it and causing the same effect as acid rain or causing eutrophication problems. Therefore, ammonia gas countermeasures are a major issue to be solved from the viewpoint of global environmental protection, and it is necessary to develop environmental protection type compost manufacturing technology that takes into consideration the surrounding area environment and the global environment.

  Commonly used physicochemical and biological odor countermeasures for ammonia include a method of washing ammonia with an acidic chemical solution, and high-density nitrifying bacteria etc. in the breathable filler in the biological deodorization device. Research has been conducted on a method of carrying and treating, and a suction-air composting method that collects ammonia generated in the compost manufacturing process by forcibly sucking and ventilating odors.

For example, Patent Document 1 discloses a method for alleviating odor generated during fermentation of organic solid waste, and the weight of the organic solid waste is initially set in the process of fermentation treatment by microorganisms in the apparatus. It is characterized in that an easily decomposable organic substance that alleviates the ammonia odor is introduced when the amount reaches 10%.
Patent Document 2 discloses a deodorizing method and a deodorizing device for gas generated in a composting facility for organic waste, and the ammonia contained in the gas is absorbed by the contact liquid to be removed. Is.

  Moreover, as a method which does not require an apparatus or a facility, there is a method for directly adding odor-reducing microorganisms to compost (bioaugmentation).

  On the other hand, some inventors of the present application have made extensive studies on composting organic waste, and a method and apparatus for treating organic waste capable of composting organic waste in a short time by microorganisms (Patent Document) 3) Organic waste fermentation treatment device (Patent Document 4), which is covered with a heat insulating material so that fermentation heat generated by fermentation of organic waste does not leak to the outside, almost the same at all height positions in the treatment tank The garbage processing apparatus (patent document 5) which can be fermented in an advanced state is invented, and the patent applicant of the present application has applied for a patent.

JP 2002-86195 A JP 2001-293331 A JP 2001-276777 A JP 2001-047019 A JP-A-11-199356

  One cause of malodor is the intense ammonia production and volatilization from the raw materials during the composting process. Ammonia is the most common odor component produced in anaerobic and aerobic conditions. At composting facilities, ammonia volatilization accounts for over 99% of the nitrogen released into the atmosphere along with very small amounts of N2O and amines. Needless to say, it is very important to maintain appropriate ammonia in the compost for growing the crop. Therefore, development of an effective technique for appropriately controlling the volatilization of ammonia is demanded.

  Techniques such as the above-mentioned method of washing ammonia with an acidic chemical solution are highly effective as measures to prevent the scattering of ammonia, but they require special equipment and facilities. The current situation is not reached. In addition, the direct addition method (bioaugmentation) of odor-reducing microorganisms to compost is mainly aimed at reducing odors derived from volatile fatty acids generated in the composting process. Few cases have been used to mitigate. The main reason for this is that there is no high-temperature nitrifying bacteria necessary or sufficient to prevent ammonia from being easily released and volatilized in the high temperature phase (60 ° C to 80 ° C) of the compost production process. It is said that.

  While various physicochemical and biological ammonia treatment technologies currently exist, maintaining appropriate ammonia in the compost is also an important factor in producing good compost. The ammonia stripping method, one of the physicochemical treatment processes, can efficiently remove high-concentration ammonia contained in livestock wastewater, etc. It is known that the removal rate can be adjusted depending on conditions.

However, when applying the ammonia stripping method to remove ammonia from livestock waste, conditions such as pH, temperature, inflow of air and steam must be controlled simultaneously, and the operation is very complicated. It is.
Further, the conventional organic waste composting apparatus and the organic waste composting method using the same are intended to complete the composting of the organic waste in the apparatus. For this reason, there is a problem that the composting apparatus is occupied for a long period from the input of the organic waste to the completion of composting. In order to process a large amount of organic waste, it is necessary to manufacture a device having a larger capacity or to increase the number of devices, and the cost and the processing amount are limited.

  On the other hand, the bad odor generated in the composting process is due to the high concentration of ammonia in the organic waste to be treated, so it is considered that the odor generated in the composting process can be suppressed by removing it beforehand. It is done.

  Therefore, the present invention can easily control the stripping conditions when removing ammonia contained in organic waste including livestock waste by the ammonia stripping method. By adjusting the ammonia concentration in the organic waste in advance to the extent that ammonia volatilization does not occur due to the heat of fermentation that occurs during the composting process (the chemical equilibrium is maintained), An object of the present invention is to provide a method for composting organic waste that can effectively prevent the generation of malodor that has been a major problem in the composting process.

  In addition, the present invention makes it possible to efficiently use the treatment tank by ending the treatment of the organic waste in the treatment tank in a short time without the treatment apparatus being occupied until the composting of the organic waste is completed. An object is to provide a method for composting organic waste.

  In order to solve the above-mentioned problem, the present invention according to claim 1 is a sealable treatment tank provided with a stirring means in an organic waste composting method in which organic waste is composted using microorganisms. The organic waste is housed in the container and exposed to the organic waste for 20 minutes to 3 hours at a temperature of 85 ° C. to 120 ° C. while adjusting the pH of the organic waste to 7.5 to 9.5. Primary that removes a predetermined amount of nitrogen contained in organic waste by stripping nitrogen contained in ammonia as ammonia and stripping the generated ammonia with water vapor generated in the treatment tank, air supplied from outside or water vapor It is characterized by including a treatment process and a secondary treatment process in which organic waste after the primary treatment is composted with microorganisms.

  By applying the ammonia stripping method to organic waste, which is a raw material before composting, especially high-concentration ammonia contained in livestock waste, the ammonia odor generated in the post-composting process is ensured. To suppress. Moreover, the water contained in the organic waste evaporates by heating, and the ammonia in the organic waste can be removed simultaneously by the vapor, so the pH and temperature of the organic waste are controlled and held for 20 minutes to 3 hours. This is very easy because it is only necessary.

  In order to solve the above-mentioned problem, the present invention described in claim 2 is a method for composting organic waste according to claim 1, wherein ammonia removed by stripping in the primary treatment step is recovered with an acid. Features.

  In order to solve the above-mentioned problem, the present invention according to claim 3 is the method for composting organic waste according to claim 1 or 2, wherein the temperature in the treatment tank is increased by stirring the organic waste. The stirring means is operated so as to generate frictional heat due to contact between wastes, contact between the organic waste and the inner wall of the treatment tank, or contact between the organic waste and the stirring means, thereby increasing the temperature to 85 ° C to 120 ° C. It is characterized by warming.

  In order to solve the above-mentioned problem, the present invention according to claim 4 is the organic waste composting method according to claim 1 or 2, wherein the temperature in the treatment tank is 85 by heat exchange with hot water or steam. It is characterized by heating to a temperature of from -120 ° C.

  In order to solve the above-mentioned problem, the present invention according to claim 5 is the organic waste composting method according to claim 1 or 2, wherein the temperature in the treatment tank supplies water vapor directly into the treatment tank. It is characterized by heating to 85 to 120 ° C.

  According to the method for composting organic waste according to the present invention, the pH and temperature of the organic waste are controlled and held for 20 minutes to 3 hours while the organic waste is accommodated in the treatment tank and stirred. Since only the operation is required, it is very simple, and since the processing tank is not occupied for a long period of time, there is an effect that the processing tank can be used efficiently.

  Moreover, according to the method for composting organic waste according to the present invention, it is possible to effectively suppress the generation of ammonia odor in the composting process of organic waste such as livestock waste.

  Furthermore, according to the method for composting organic waste according to the present invention, the final compost is an excellent compost exhibiting high humification.

  The organic waste composting method according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a flowchart of an embodiment of a method for composting organic waste according to the present invention, and FIG. 2 is a conceptual diagram of an embodiment of a method for composting organic waste according to the present invention.

  The illustrated organic waste composting method is a primary process for stripping a predetermined amount of ammonia from livestock waste such as cattle, pigs and bird manure, and organic waste such as waste such as raw garbage (step S1). ) And a secondary step (step S2) of composting organic waste stripped with a predetermined amount of ammonia, and the primary step (S1) further treats organic waste to be treated. A step of storing in the tank (step S11), a step of adjusting the pH and temperature of the organic waste stored in the processing tank (step S12), and a predetermined amount of ammonia from the organic waste in the processing tank. A step of ripping (step S13) and a step of recovering stripped ammonia (step S14) are provided. On the other hand, the secondary step (S2) includes a step (step S21) of composting (composting) the organic waste from which a predetermined amount of ammonia has been removed in the primary step (S1) using microorganisms.

  The processing tank 10 includes an accommodating portion 11 for accommodating organic waste therein, and a discharge port 13 is provided on the lower side of the accommodating portion 11. Further, a motor 17 for rotating the stirring blade 15 (see FIG. 3) disposed inside the accommodating portion 11 is disposed on the bottom plate of the processing tank 10. The processing tank 10 is formed of, for example, a metal material such as iron or steel, and the accommodating portion 11 is supported by a plurality of support pillars 10a. The accommodating part 11 has a substantially cylindrical shape, and a lid part 11a that can be opened and closed for introducing organic waste is provided on the upper surface thereof. The accommodating portion 11 and the lid portion 11a are designed to withstand the internal pressure rise, and the internal temperature of the accommodating portion 11 and the lid portion 11a is 120 as the pressure in the accommodating portion 11 increases due to ammonia or vapor generated from organic waste. It has reached ℃. In addition, it is also possible to prevent heat loss in the accommodating portion 11 by covering the periphery of the processing tank 10 with a heat insulating material. In addition, a shaft 15 a serving as a rotating shaft of the stirring blade 15 is erected inside the accommodating portion 11, and the stirring blade 15 is rotated by rotating the shaft 15 a by a motor 17.

  A discharge mechanism such as a screw conveyor is provided inside the discharge port 13 to discharge the treated organic waste after the removal of a predetermined amount of ammonia to the outside. Although not shown, the processing tank 10 is provided with a temperature sensor and a pH sensor, and a control panel for controlling the rotation of the screw conveyor and the motor 17 is attached. Further, the processing tank 10 may be provided with an illumination device, a viewing window for internal observation, and the like. On the other hand, the treatment tank 10 is provided with an exhaust duct 12 for discharging the ammonia in the accommodating portion 11 to the outside. The exhaust duct 12 is connected to a scrubber 20 for recovering ammonia. The scrubber 20 has a cylindrical shape with a narrowed upper end, and the exhaust duct 12 from the treatment tank 10 is connected to the lower side of the scrubber 20, and a sulfuric acid solution shower is performed from above on the ammonia introduced into the scrubber 20. Has come to pour down. As a result, ammonia is neutralized to ammonium sulfate. This ammonium sulfate is recovered as appropriate.

  As shown in FIG. 3, the stirring blade 15 is provided on a plate-like upper rotary blade 15b provided so as to protrude in the horizontal direction from the vicinity of the upper portion of the rotary shaft 15a, and on the lower side of the rotary shaft 15a. A substantially U-shaped lower rotary blade 15c is provided. The upper rotary blade 15b and the lower rotary blade 15c are provided at two positions opposite to each other, and the upper rotary blade 15b and the lower rotary blade 15c are arranged at positions shifted by 90 ° from each other. A portion that vertically connects the upper end portion and the lower end portion of the lower rotary blade 15 c is formed in accordance with the inner surface shape of the inner wall surface of the housing portion 11, and is attached to the inner wall surface of the housing portion 11. While operating to scrape waste, the connecting portion of the lower rotary blade 15c performs an agitation operation so as to press the organic waste against the inner wall surface of the accommodating portion 11, so that frictional heat is easily generated. Yes. Further, the upper rotary blade 15b scrapes off the organic waste that rises along the inner wall of the housing portion 11 as the stirring blade 15 rotates, and maintains the organic waste in a uniform state. The organic waste is rubbed by the agitation by the agitation blade 15 by contact between the organic wastes, the lower rotary blade 15b and the inner wall of the accommodating portion 11, and further the direct contact between the upper rotary blade 15b and the lower rotary blade 15c. Generate frictional heat. The temperature in the accommodating part 11 is heated to 85 degreeC-120 degreeC with this frictional heat. In addition, in order to heat the temperature in the accommodating part 11 to 85 degreeC-120 degreeC, the outer periphery of the accommodating part 11 is performed by heat exchange with hot water or steam, or water vapor | steam is directly supplied in the accommodating part 11. Can also be done.

Hereinafter, the organic waste composting method according to the present invention will be described based on specific examples.
First, as an organic waste to be treated, a compost sample composed of cow dung (80%) and sawdust (20%) was used. The compost sample was adjusted to pH 9.0 and water content 51% so that ammonia remained appropriately. Then, the compost sample is subjected to primary processing (S1) in the processing tank 10 provided with a storage section 11 of about 0.6 m ³ , and then a compost pile having a length of 2 m, a width of 1.8 m, and a height of 1.2 m. 30 was formed and the secondary treatment (S2) was performed.

  In the primary treatment step (S1), the compost sample to be treated was accommodated in the accommodating portion 11 (S11), and about 120 kg of the compost sample was mechanically agitated by the stirring blades 15 installed in the accommodating portion 11. In the present embodiment, the temperature in the housing portion 11 was raised to 100 ° C. within 2 hours by the frictional heat generated in the housing portion 11. That is, when the compost sample is agitated, the compost sample, the compost sample and the inner wall of the accommodating portion 11, or the compost sample and the stirring blade 15 come into contact with each other to generate frictional heat. This frictional heat is actively used. As a matter of fact, the stirring blade 15 was operated at a stirring speed of 60 rpm / min. Heat treatment of the compost sample at 100 ° C. is extremely effective for producing sanitary and safe compost by controlling organic waste, particularly pests and pathogenic microorganisms derived from livestock waste. The maximum temperature (100 ° C.) was maintained for at least 30 minutes in order to remove excess ammonia in the compost sample and adjust the water content. During this time, the pH of the compost sample was kept so as not to exceed the range of 7.5 to 9.5 (S12). The reason why the pH is kept within the range is that the ammonia removal efficiency deteriorates if the pH is exceeded. When pH exceeds the range of 7.5-9.5, an acid agent and an alkali agent are added and the pH is adjusted suitably.

A predetermined amount of ammonia is stripped by exposing the compost sample at a pH of 7.5 to 9.5 and a temperature of 85 ° C. to 120 ° C. for 20 minutes to 3 hours (S13). ). The stripped ammonia was sent to the scrubber 20 through the exhaust duct 12 and recovered as ammonium sulfate by showering with a sulfuric acid solution (S14).
The compost sample that has been processed is discharged from the discharge port 13 of the processing tank 10 to form a compost pile 30 having a length of 2 m, a width of 1.8 m, and a height of 1.2 m. The treatment step (S2), that is, composting with microorganisms (composting) was performed for 6 weeks (S21).

  Here, in order to comparatively analyze the physicochemical and microbiological characteristics of the organic waste composting method according to the present invention, a compost mountain having the same volume as the compost mountain 30 in the secondary treatment step (S2) described above. Were separately formed, and composting was promoted. The compost pile 30 of the secondary treatment step (S2) and the compost pile of the comparative example were each mixed once a week, and each compost sample was collected every week for 1.5 months. Moreover, the compost sample in the storage unit 11 during the primary treatment step (S1) was collected when the temperature in the storage unit 11 reached 25, 50, 75, 85, and 100 ° C. In order to compare the physicochemical characteristics of the final compost samples, the pH, volatile residue, water content, C / N ratio, total nitrogen, inorganic nitrogen, total phosphorus Analysis of total potash and humic index (Organic Matter Evolution Index (OMEI)) was conducted.

  Table 1 shows the analysis results of this example and the comparative example.

  In the present embodiment, the temperature of the container 11 was raised by frictional heat with the compost sample generated by mechanical stirring of the stirring blade 15 of the treatment tank 10. About 53% of the ammoniacal nitrogen was removed by the time the temperature in the container 11 reached 50 ° C., and finally the removal rate reached 80% by 100 ° C. within 3 hours. During operation of the treatment tank 10, a small amount of nitrate nitrogen and nitrite nitrogen was detected (FIG. 4-A). In the subsequent secondary treatment step (S2), the concentration of ammoniacal nitrogen in the compost sample did not change until composting was completed (FIG. 4-B). Moreover, the odor problem which causes volatilization of ammonia during the secondary treatment step (S2) did not occur. This is because the excess ammonia contained in the raw material is stripped in advance, so that the ammonia concentration in the raw material keeps chemical equilibrium against changes in fermentation heat and pH generated in the secondary treatment step (S2). It is thought that it was because of being leaned. In FIG. 4, “reactor internal temperature” refers to the temperature in the container 11. The “ultra-high temperature pretreatment reactor” refers to the treatment tank 10 and shows a change in the concentration of inorganic nitrogen during the treatment of organic waste by the treatment tank 10. The “ultra-high temperature pretreatment odorless deposition method” is the secondary treatment step (S2) in the method of the present invention, and the “simple field loading method” is a comparative example of the field loading method. That is.

  On the other hand, in the comparative example by the composting method by the open stacking method, about 78% of ammonia nitrogen in the initial compost sample was released, and the problem of bad odor due to the ammonia odor continued for 1.5 months (FIG. 4). -B). In addition, nitrate nitrogen and nitrite nitrogen gradually accumulated in the compost sample over one month from the start. However, the final ammonia concentrations in the compost samples of the examples and comparative examples were almost the same.

  Here, it was confirmed that in the examples, much more humic acid was formed in the compost sample than in the comparative example. From the analysis based on the OMEI value, it was found that humic acid was also generated in the compost sample in the container 11 (FIG. 5A). In the primary treatment step (S1), a large amount of humic acid was produced in the compost sample in the first 3 weeks, and the OMEI value remained almost constant until composting was completed (FIG. 5-B). The final compost produced by this example gave off an earthy odor, and the shape of the compost was considerably fine. On the other hand, the OMEI value of the compost sample of the comparative example was lower than the OMEI value of the compost sample of this example. Many substances having large particles were still observed in the final compost sample of the comparative example. In FIG. 5, “reactor internal temperature” refers to the temperature in the container 11. The “ultra-high temperature pretreatment reactor” refers to the treatment tank 10 and shows a change in humification rate (OMEI) when organic waste is treated in the treatment tank 10. The “ultra-high temperature pretreatment odorless deposition method” is the secondary treatment step (S2) in the method of the present invention, and the “simple field loading method” is a comparative example of the field loading method. That is.

  Next, the water content of the final compost sample of this example and the compost sample of the comparative example was adjusted to 50% with water, and each compost 30 was tried to be stirred. As a result, the temperature of the compost mountain 30 of this example did not increase among the volume mountains after one day of cultivation, whereas the temperature of the compost mountain of the comparative example increased to around 60 ° C. This indicates that the readily decomposable organic matter in the compost sample according to this example is completely decomposed.

  As shown in Table 1, in this example and the comparative example, the pH changed between 8.8 and 9.2. In the primary step (S1) of this embodiment, the C / N ratio of the raw material in the container 11 is significantly increased from 26.6 to 34.8 due to volatilization of ammonia, and after the secondary step (S2), Finally, it stabilized at 30.3. On the other hand, the C / N ratio of the compost sample of the comparative example was lower than the C / N ratio of the compost sample of the example, and finally became 21.5.

  Furthermore, in order to clarify the characteristics of the compost produced by this example, the physicochemical characteristics of various composts produced by other raw materials and methods were analyzed. Table 2 shows the results.

  It was found that the OMEI value of the compost produced by this example was much higher than other composts produced mainly from cow dung. Moreover, the compost manufactured by the present Example shows the highest C / N ratio compared with other composts.

  As described above, the preferred embodiment of the present invention has been described in detail. However, the present invention is not limited to the specific embodiment, and within the scope of the gist of the present invention described in the claims, Needless to say, various modifications and changes are possible.

It is a flowchart of one Embodiment of the composting method of the organic waste which concerns on this invention. It is a conceptual diagram of one Embodiment of the composting method of the organic waste which concerns on this invention. It is a figure which shows an example of a stirring blade. A is a graph showing a change in nitrogen concentration in the treatment tank in the primary treatment, and B is a graph showing a change in nitrogen concentration in the secondary treatment. A is a graph showing humification in the treatment tank in the primary treatment, and B is a graph showing humification in the secondary treatment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Treatment tank 10a Support pillar 11 Accommodating part 11a Cover part 12 Exhaust duct 13 Discharge port 15 Stirring blade 15a Rotating shaft 15b Upper rotating blade 15c Lower rotating blade 17 Motor 20 Scrubber 30 Compost mountain

Claims (5)

In a method for composting organic waste that uses microorganisms to compost organic waste,
An organic waste is accommodated in a sealable treatment tank equipped with a stirring means inside, and the pH of the organic waste is adjusted to 7.5 to 9.5, and a temperature of 85 ° C. to 120 ° C. for 20 minutes. By exposing for 3 hours to liberate nitrogen contained in the organic waste as ammonia, and stripping the generated ammonia with water vapor generated in the treatment tank, air supplied from outside or water vapor A primary treatment step of removing a predetermined amount of nitrogen contained in the organic waste in advance;
A secondary treatment step of composting organic waste after primary treatment with microorganisms;
A composting method for organic waste, comprising: The organic waste composting method according to claim 1,
An organic waste composting method comprising recovering ammonia removed by stripping in the primary treatment step with an acid. In the composting method of the organic waste according to claim 1 or 2,
The temperature in the treatment tank generates frictional heat due to contact between organic wastes, contact between organic wastes and the inner wall of the treatment tank, or contact between organic wastes and stirring means by stirring the organic waste. The organic waste composting method is characterized in that the stirring means is operated so as to cause the temperature to rise to 85 ° C to 120 ° C. In the composting method of the organic waste according to claim 1 or 2,
The organic waste composting method is characterized in that the temperature in the treatment tank is heated to 85 ° C to 120 ° C by heat exchange with hot water or steam. In the composting method of the organic waste according to claim 1 or 2,
The organic waste composting method is characterized in that the temperature in the treatment tank is heated to 85 ° C. to 120 ° C. by directly supplying water vapor into the treatment tank.

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