JP2009046335A - Method for producing compost - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a compost, where the generation amount of greenhouse gas from compost production facilities can be reduced, and simultaneously, a compost of high quality owing to the progression of maturation can be produced. <P>SOLUTION: In the method for producing the compost, the concentration of nitrous oxide in a nitrous oxide-containing gas generated from compost production facilities is measured at each predetermined time, and, in the case the measured value exceeds standard value, turning is performed, so as to suppress the generation of nitrous oxide. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing compost, and more particularly to a method for producing compost while suppressing the generation of greenhouse gases.

  Conventionally, aerobic fermentation (sedimentation fermentation) was conducted by introducing sludge cakes from sludge generated from sewage treatment plants and rural village wastewater treatment plants, and compost materials consisting of organic waste such as livestock manure and dredging into compost production facilities. A method for producing compost by maturation) is known.

  The present inventors have found that dinitrogen monoxide is generated by the following mechanism when producing compost.

  Organic materials containing nitrogen, such as proteins in compost raw materials, are decomposed into ammonia by the activity of microorganisms (fungi and bacteria), and then oxidized to nitrous acid and nitric acid. If consumed and the supply of air (oxygen) is not sufficient, the inside becomes anaerobic.

  Under anaerobic conditions, the atmosphere is partially reduced, and a reduction reaction from nitric acid to nitrogen (nitric acid → nitrous acid → nitrogen oxide → dinitrogen monoxide → nitrogen) occurs.

  Among the microorganisms that perform this series of reduction reactions, among the fungi that perform the reduction reaction, there are bacterial species that do not have an enzyme that reduces dinitrogen monoxide to nitrogen.

  According to such fungi, since dinitrogen monoxide cannot be reduced, the reduction of nitric acid stops only up to dinitrogen monoxide, and dinitrogen monoxide is accumulated and released as a final substance.

  There are many composting facilities around the world, and if even a small amount is generated from each facility, a large amount of nitrous oxide will be generated on a global scale.

  Dinitrogen monoxide is a greenhouse gas that is considered to cause warming along with carbon dioxide, methane, chlorofluorocarbons known as a kind of Freon, and the like.

  The greenhouse effect of nitrous oxide is said to be 100 times or 300 times that of carbon dioxide (210 times according to IPCC).

  There are currently no restrictions on the generation of biologically-derived greenhouse gases, but in the future, it will be required to take specific control measures for each source in order to suppress the generation.

  Based on the above findings, the present inventor reduced greenhouse gas emissions by suppressing dinitrogen monoxide in compost production and by performing “turn-over” using the concentration of dinitrogen monoxide as a trigger. At the same time, the inventors have found that it is possible to produce high-quality compost by the progress of ripening, and have reached the present invention.

  Conventionally, Patent Document 1 discloses a technique for switching back by monitoring the odor generated from compost or the like, and Patent Document 2 monitors the compost temperature distribution to switch back at an appropriate timing. Techniques for performing are disclosed. Further, Patent Document 3 discloses an apparatus for producing compost that is completely matured at low cost, by using the same means for stirring air injection and stirring.

  However, Patent Documents 1 to 3 do not disclose a technique that focuses on the amount of dinitrogen monoxide generated from compost. Therefore, in terms of suppression of the generation of dinitrogen monoxide, the turning back is insufficient, and dinitrogen monoxide is sometimes generated.

Patent Document 4 discloses a method for measuring dinitrogen monoxide in a sewage sludge combustion furnace and controlling the generation amount to be small. However, in Patent Document 4, the gas in the incinerator is irradiated with a gas in the near-infrared wavelength region as it is to measure the absorbance. However, the combustion gas contains carbon dioxide in addition to dinitrogen monoxide. Since carbon dioxide and dinitrogen monoxide have similar infrared absorption characteristics, there is a possibility that an error occurs in the concentration of dinitrogen monoxide depending on the carbon dioxide concentration in the measurement gas.
JP 2004-196621 A JP 2005-145775 A JP 2006-219332 A JP 2004-125331 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a compost manufacturing method capable of reducing the amount of greenhouse gas generated from a compost manufacturing facility and simultaneously manufacturing high-quality compost due to the progress of ripening.

  The other subject of this invention becomes clear by the following description.

  The above problems are solved by the following inventions.

(Claim 1)
A method for producing compost, characterized by suppressing generation of dinitrogen monoxide.

(Claim 2)
In the compost manufacturing method of manufacturing compost by aerobic fermentation of compost raw materials,
A method for producing compost, characterized in that the generation of dinitrogen monoxide is suppressed by turning back.

(Claim 3)
The method for producing compost according to claim 1 or 2, wherein, in the compost production process, turning over is performed every predetermined time to suppress generation of dinitrogen monoxide.

(Claim 4)
Measure the dinitrogen monoxide concentration of the gas containing dinitrogen monoxide generated from the compost manufacturing facility,
The compost manufacturing method according to claim 1, wherein the measured value exceeds the reference value and is turned over.

(Claim 5)
The gas containing carbon dioxide and dinitrogen monoxide generated from the compost production facility is collected, and then the collected gas is passed through an alkaline absorbent to separate the carbon dioxide.
Obtain the absorbance of the gas containing the obtained dinitrogen monoxide,
5. The method for producing compost according to claim 1, wherein the concentration is calculated when the concentration calculated from the obtained absorbance exceeds a reference value.

(Claim 6)
The method for producing compost according to claim 4 or 5, wherein the reference value is a value determined at a concentration of dinitrogen monoxide of 500 ppm or more.

(Claim 7)
The method for producing compost according to any one of claims 1 to 6, wherein the moisture content of the compost raw material in a maturing facility for compost production is maintained at 40 to 70%.

  According to the present invention, it is possible to provide a method for producing compost capable of reducing the amount of greenhouse gas generated from a compost production facility and at the same time producing high-quality compost due to the progress of ripening. Since it absorbs with a chemical | medical agent, the manufacturing method of a compost which does not have the influence of a carbon dioxide concentration in the case of a measurement of a dinitrogen monoxide can be provided.

  Embodiments of the present invention will be described below.

  In the present invention, the compost manufacturing facility uses organic waste such as sludge cake, livestock excrement and dredged dewatered sludge generated from sewage treatment plants and rural village wastewater treatment plants as the main compost raw materials, and aerobic fermentation. It is a facility that produces compost that is mainly used as fertilizer for plants such as agricultural crops and parks.

  In the present invention, the facility for manufacturing the compost is not limited at all. It is preferable that there is a covering structure such as a roof or a cover, and an opening for exhausting the air inside is provided so that the gas generated from the compost can be taken out. Even if there is no structure to cover and the gas generated from compost is released to the atmosphere in a normal state, the present invention can be used effectively if the gas generated from compost can be sampled. it can.

  FIG. 1 is a schematic diagram of an apparatus for measuring greenhouse gases from exhaust gas sampled from a facility that generates greenhouse gases.

In the present invention, the greenhouse gases to be measured are dinitrogen monoxide and methane, preferably dinitrogen monoxide (N ₂ O).

  1 is an exhaust introduction pipe for introducing exhaust exhausted from the facility, 2 is a sampling fan provided in the exhaust introduction pipe 1, 3 is a vial containing an alkaline liquid inside, and in the vial A liquid phase 3b composed of a gas phase 3a and an alkaline absorbent is formed.

  When measuring the greenhouse gas concentration, the sampling fan 2 is operated, the exhaust gas is sucked from the exhaust gas introduction pipe 1 provided at the exhaust port of the facility, and introduced into the vial 3. The vial 3 is brought into contact with the alkaline absorbent and the introduced exhaust to absorb carbon dioxide and sulfur dioxide in the exhaust which hinders the measurement of greenhouse gases.

  In order to enhance the absorption effect, the gas 3a can be sucked by the pump 4, returned to the liquid phase 3b in the vial 3, and aerated again.

  Examples of the alkaline absorbent include alkali metal hydroxides and alkaline earth metal hydroxides, among which sodium hydroxide is preferable. Its pH is at least 8 or higher and absorption close to saturation is also preferred.

  Reference numeral 5 denotes an optical measuring instrument that measures the absorbance of the greenhouse gas in the infrared region. A gas excluding carbon dioxide and sulfur dioxide is introduced into the vial 3 and the concentration of the warming gas containing dinitrogen monoxide is measured. Examples of optical measuring instruments that measure absorbance in the infrared region include non-dispersive infrared absorption gas analyzers and wide-spread infrared gas analyzers. Measures nitrous oxide concentration.

  Note that the dinitrogen monoxide concentration can be suppressed by eliminating the anaerobic state, and therefore, it is preferable to switch back every predetermined time in order to suppress the generation of dinitrogen monoxide.

  If the nitrous oxide concentration exceeds the standard value, the inside of the compost becomes anaerobic and it is thought that greenhouse gases that cause global warming are generated. Do. Further, the switching can be controlled using the reference value as a trigger.

  Examples of the turning-back method include, but are not limited to, a method in which compressed air is sent from an air introduction pipe provided under the compost and aerobicized, and a method in which the agitation is performed by stirring with a machine or the like. The switching operation may be performed until the concentration of the greenhouse gas to be measured falls below a predetermined value, or it may be performed a specified number of times and then remeasured, and the effect of switching is insufficient (exceeding the specified concentration). )), It may be switched again.

  In the present invention, a compost manufacturing apparatus is provided by measuring a greenhouse gas, inputting a measurement result, and providing a control unit that outputs an instruction signal to switch back when the measurement result exceeds a reference value. Can be controlled automatically.

  FIG. 2 is a diagram showing an embodiment used in the compost manufacturing method of the present invention.

  In FIG. 2, 7 is a compost manufacturing apparatus. The compost production apparatus 7 has a plurality of tanks 703 in which a rectangular or cylindrical compost production apparatus main body 701 is partitioned by a plurality of partition walls 702, and the compost is fermented and aged in the tank 703.

  The compost raw material charged into the tank 703 from the compost raw material inlet 704 is fermented and matured while moving from the tank close to the compost raw material inlet 704 to the tank near the compost product outlet 705.

  An inclined portion 706 is provided at the bottom of each tank 703 to eliminate dead space, and the lower part of the tank 703 is formed in a conical shape or a pyramid shape.

  A space is formed between the lower portion of the inclined portion 706 and the compost manufacturing apparatus main body 701, and a heater 707 for adjusting the temperature is provided in each space.

  At the bottom of the tank 703, one or more air supply pipes 708 for introducing air into the compost are installed, and the air supply pipe 708 is connected to a compressor 709 for supplying pressurized air. The tip of the air supply pipe 708 is in the tank 703, and air is supplied into the compost by supplying pressurized air from the air supply pipe 708, and at the same time, the compost can be stirred. In the compost manufacturing apparatus of FIG. 2, “turning back” is performed by this air introduction and stirring.

  The air introduced from the air supply pipe 708 is preferably configured to be temperature-controllable, and is preferably supplied with air heated by a heater (not shown) or the like.

  It is also preferable to provide another air supply pipe (not shown) in the tank 703 and connect it to a blower that supplies humidified air, and supply humidified air in addition to pressurized air.

  Reference numeral 710 denotes an exhaust port provided in the upper part of the compost manufacturing apparatus main body 701. The exhaust inlet 710 is connected to the exhaust port 710 so that a part of the exhaust can be sampled.

  Excess exhaust gas that is not used for the measurement of the warming gas is directly discharged from the exhaust port 710.

  An example of a control flow in the control unit 6 that controls the compost manufacturing apparatus 7 is shown in FIG.

  First, the control unit 6 operates the sampling fan 2, sucks exhaust gas from the exhaust introduction pipe 1 provided at the exhaust port of the facility, and introduces it into the vial 3 (S1).

  The vial 3 is brought into contact with the alkaline absorbent and the introduced exhaust to absorb carbon dioxide and the like in the exhaust that hinders the measurement of the greenhouse gas (S2). Further, the pump 4 is operated as necessary.

  The absorbance in the infrared region is measured by the optical measuring instrument 5 (S3), and the concentration of the warming gas is calculated from the absorbance (S4).

  It is determined whether the greenhouse gas concentration exceeds a reference value (S5).

  Here, the reference value is a value determined in a range where the concentration of dinitrogen monoxide is 500 ppm or more. In the case of methane, it is preferable that the methane concentration is a value determined in a range of 500 ppm or more when the same turnover as that of dinitrogen monoxide is performed.

  If the reference value is not exceeded, it is determined that the anaerobic state has not been reached and the process ends.

  When it exceeds the reference value, the control unit 6 operates the compressor 709 to introduce air into the tank 703 and perform switching (S6). Thereafter, the process returns to S1.

  When the compost production apparatus is equipped with a motor-driven stirring blade or the like as the stirring means and a blower or the like as the air supply means, the control unit 6 can be controlled to perform reversal by operating the motor and the blower. it can.

  Further, in order to suppress the activity of anaerobic bacteria, promote fermentation by aerobic bacteria, suppress fungal metabolism and advance aging, the moisture content during compost aging is, for example, 40 to 70%, preferably 50 to It is important to maintain 60%. It is preferable that the moisture content is maintained as described above even in a dry type compost production mode.

  When the water content exceeds 70%, the environment becomes easy for fungi to grow and actively grows. Moreover, the air permeability of compost decreases due to an increase in the moisture content, and it easily falls into an anaerobic state.

  As a result, fungi grow actively under anaerobic conditions, and according to such fungi, dinitrogen monoxide cannot be reduced, so the reduction of nitric acid stops at dinitrogen monoxide, and finally Nitrogen monoxide accumulates as a substance and the amount released is increased.

  Therefore, apart from the method of controlling switching by measuring greenhouse gases, there is also a method of controlling switching by monitoring a unique odor (so-called mold odor) emitted by fungi. In addition, this method and this invention can also be used together.

  The moisture content can be measured by a commonly used method as needed. If the moisture content is insufficient, the moisture is replenished with humidified air, mist, watering, etc. Can be promoted and adjusted.

  By appropriately managing the moisture content and turning it back, the inside of the compost becomes anaerobic and the growth of fungi can be suppressed, and the generation of greenhouse gases can be further suppressed. Moreover, since an aerobic state is maintained so that greenhouse gas may not be generated (become anaerobic), fermentation and ripening by aerobic bacteria are promoted, and high quality compost can be produced.

  In the present invention, when the measured greenhouse gas concentrations of dinitrogen monoxide and methane exceed a reference value, the control can be performed and a warning can be issued. The warning can be performed, for example, on a monitor screen (not shown).

  The effects of the present invention are illustrated below by examples.

Example 1
Semi-aged compost (moisture content of 54%) derived from sewage sludge collected from a dry type (water content of about 50%) composting apparatus was placed in two Erlenmeyer flasks A and B and sealed (start of experiment).

  The Erlenmeyer flask was shaken at intervals of 5 to 10 minutes so as to be in contact with the air in the Erlenmeyer flask (turned back), and the Erlenmeyer flask A was collected 1 hour after the start of the experiment, and the gas in the Erlenmeyer flask B was collected after 2 hours. Carbon dioxide was absorbed through a sodium hydroxide solution, and the concentration of dinitrogen monoxide was measured using a gas chromatograph equipped with an electron capture detector.

Example 2
As in Example 1, Erlenmeyer flasks C and D in which semi-aged compost were sealed were allowed to stand (no turning over). One hour after the start of the experiment, the gas in the Erlenmeyer flask C was collected and the dinitrogen monoxide concentration was measured in the same manner as in Example 1. The Erlenmeyer flask D was allowed to stand for 1 hour, then shaken (turned back) at intervals of 5 to 10 minutes, collected gas 2 hours after the start of the experiment, and measured the dinitrogen monoxide concentration.

Comparative Example 1
The concentration of dinitrogen monoxide was measured in the same manner as in Example 1 except that water content was adjusted to 78% by adding water to semi-aged compost. (Erlenmeyer flasks E and F)

Comparative Example 2
The same compost as in Comparative Example 1 was used, and the conditions were the same as in Example 2. The concentration of dinitrogen monoxide was measured. (Erlenmeyer flask G, H)

  Table 1 shows the measurement results of dinitrogen monoxide concentrations in Examples 1 and 2 and Comparative Examples 1 and 2.

  In Example 1, the nitrous oxide concentration was kept low because it was stirred (turned back) by shaking at predetermined intervals and the anaerobic formation in the compost was suppressed by touching the air in the Erlenmeyer flask.

  Since Example 2 was allowed to stand for 1 hour from the start of the experiment, anaerobization in the compost progressed and the nitrous oxide concentration increased (contrast of Erlenmeyer flasks A and C). It can be seen that there is a large difference in the concentration of dinitrogen monoxide generated by the fact that the switching is not performed.

  However, when it was stirred (turned back) at predetermined time intervals thereafter, the concentration of nitrous oxide decreased (erlenmeyer flask D). Even if a high concentration of nitrous oxide was detected, it was possible to reduce nitrous oxide by switching back and eliminating anaerobic conditions.

  Comparative Example 1 was the same as Example 1 and Comparative Example 2 was the same as Example 2 except for the moisture content of the sample. However, the nitrous oxide concentration measured in the Erlenmeyer flasks E to H tended to be higher than that of the Erlenmeyer flasks A to D. It is thought that because the moisture content was high, the permeability of compost decreased and it was easy to become anaerobic, and the metabolism (growth) of fungi advanced.

Schematic diagram of a device for measuring greenhouse gases The figure which shows the one aspect | mode used for the compost manufacturing method of this invention. Control flow chart in the control unit that controls the compost manufacturing equipment

Explanation of symbols

1: exhaust pipe 2: sampling fan 3: vial 3a: gas phase 3b: liquid phase 4: pump 5: optical measuring instrument 6: control unit 7: compost manufacturing apparatus 701: compost manufacturing apparatus main body 702: partition wall 703: tank 704: Compost raw material inlet 705: Compost product outlet 706: Inclined part 707: Heater 708: Air supply pipe 709: Compressor 710: Exhaust port

Claims (7)

  A method for producing compost, characterized by suppressing generation of dinitrogen monoxide. In the compost manufacturing method of manufacturing compost by aerobic fermentation of compost raw materials,
A method for producing compost, characterized in that the generation of dinitrogen monoxide is suppressed by turning back.   The method for producing compost according to claim 1 or 2, wherein, in the compost production process, turning over is performed every predetermined time to suppress generation of dinitrogen monoxide. Measure the dinitrogen monoxide concentration of the gas containing dinitrogen monoxide generated from the compost manufacturing facility,
The compost manufacturing method according to claim 1, wherein the measured value exceeds the reference value and is turned over. The gas containing carbon dioxide and dinitrogen monoxide generated from the compost production facility is collected, and then the collected gas is passed through an alkaline absorbent to separate the carbon dioxide.
Obtain the absorbance of the gas containing the obtained dinitrogen monoxide,
5. The method for producing compost according to claim 1, wherein the concentration is calculated when the concentration calculated from the obtained absorbance exceeds a reference value.   The method for producing compost according to claim 4 or 5, wherein the reference value is a value determined at a concentration of dinitrogen monoxide of 500 ppm or more. The method for producing compost according to any one of claims 1 to 6, wherein the moisture content of the compost raw material in a maturing facility for compost production is maintained at 40 to 70%.

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