JP2018118894A - Compost producing method and production equipment for producing compost - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compost producing method and production equipment for producing compost capable of uniformly mixing surplus sludge and food residue and increasing productivity of the compost by enhancing fermentation of the mixture.SOLUTION: A compost producing method configured to produce a compost from surplus sludge obtained by biological processing subjected to wastewater and food residue comprises: a coarse pulverization process for pulverizing food residue by a cutter type pulverizer 10; a fine pulverization process for further pulverizing the residue obtained in the coarse pulverization process by a stone mill type pulverizer 20; a mixing process for mixing the surplus sludge and the food residue pulverized in the fine pulverization process; a dehydration process for dehydrating the mixture obtained in the mixing process by a dehydrator 40; and a fermentation process for fermenting the mixture obtained in the dehydration process to produce the compost.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a compost manufacturing method and a manufacturing apparatus therefor, which manufacture compost from surplus sludge generated by biological treatment of wastewater and food residues.

  In food factories and the like, food wastes (food residues) remain when producing processed products from foods, but instead of discarding the food residues, attempts have been made to effectively use them as resources. As one of them, there is a method of producing compost by mixing food residue with surplus sludge generated when organic wastewater such as sewage is biologically treated and fermenting it.

  For example, the following Patent Document 1 includes a step of crushing garbage, a step of dehydrating and drying the crushed garbage, a step of separating impurities from the dried garbage, and a garbage and sludge after separation. And a step of fermenting the mixed garbage / sludge and composting, a method of composting garbage is described.

  On the other hand, in Patent Document 2 below, both a solubilizing device for solubilizing food waste and a solid content and a liquid content of the solubilized food waste are introduced, together with the biological treatment residue of human waste and waste water. An organic waste treatment system is described, comprising: a storage tank to be stored automatically; and a biological treatment apparatus for biologically treating the stored substance introduced into the storage tank. The form describes that after the raw garbage is roughly crushed with a coarse crusher, the coarsely crushed raw garbage is further finely broken with a fine crusher (see paragraph 0024).

JP 2002-97094 A Japanese Patent Laying-Open No. 2015-13264

  In the above-mentioned Patent Document 1, garbage is crushed, dehydrated and dried, mixed with sludge, and fermented to obtain compost. However, since garbage is dehydrated and dried, heat energy for drying is required, and drying time is also required.

  In addition, in Patent Document 2, it is described that food waste is solubilized and used for methane fermentation, or used for composting as it is, but the food waste and excess sludge are mixed. There is no mention of composting.

  Accordingly, an object of the present invention is to provide a compost manufacturing method and a manufacturing apparatus therefor, in which food residues and surplus sludge are mixed so that compost can be efficiently manufactured.

  In order to achieve the above object, one of the present invention is a method for producing compost from surplus sludge generated by biological treatment of waste water and food residue, and the food residue is pulverized by a cutter-type pulverizer. A coarse pulverization step, a fine pulverization step of further pulverizing the residue obtained in the coarse pulverization step, a mixing step of mixing the excess sludge with the food residue pulverized in the fine pulverization step, and A dehydration step of dehydrating the mixture obtained in the mixing step with a dehydrator; and a fermentation step of fermenting the mixture dehydrated in the dehydration step into compost.

  According to the invention, the food residue is roughly pulverized with a cutter-type pulverizer and further finely pulverized with a stone mortar-type pulverizer, and then mixed with excess sludge so that the excess sludge and food residue can be mixed uniformly. The excess sludge can be easily aggregated through the finely pulverized food residue, and the dehydration operation in the subsequent dehydration step can be easily performed. As a result, operations such as drying can be omitted or simplified, and the solid content concentration of the mixture can be increased. Moreover, since the food residue finely pulverized is mixed with surplus sludge that is difficult to be decomposed by microorganisms, fermentation can be promoted to increase the productivity of compost.

  In the method for producing compost of the present invention, the dehydrator in the dehydration step is a screw conveyor having a plurality of annular plates arranged on the outer trunk portion and rotatably arranged on the inner circumference thereof, and having spiral blades. It is preferable that it is a multiple plate type screw press dehydrator which has.

  According to this aspect, the dehydrator is a multi-plate screw press having an outer body portion in which a plurality of annular plates are disposed, and a screw conveyor that is rotatably disposed on the inner periphery thereof and has spiral blades. Since it is a dehydrator, even a mixture of food residue and excess sludge can be efficiently dehydrated, and a mixture with a high solid content concentration can be obtained without going through a drying step or the like.

  In the method for producing compost of the present invention, the food residue is preferably a residue of cut vegetables or processed fishery products. According to this aspect, since the food residue is a residue of cut vegetables or processed fishery products, these can be utilized without waste, and fermentation when mixed with excess sludge can be promoted.

  On the other hand, another aspect of the present invention is a compost production apparatus for producing compost from surplus sludge generated by biological treatment of waste water and food residues, and cutter-type pulverization for roughly pulverizing the food residues A stone mortar pulverizer for further finely pulverizing the food residue pulverized by the cutter pulverizer, a mixing means for mixing the surplus sludge with the food residue pulverized by the stone mortar pulverizer, and the mixing An apparatus for producing compost, comprising: a dehydrator for dehydrating the mixture obtained by the means; and a fermentation processing unit for fermenting the mixture dehydrated by the dehydrator to produce compost.

  According to the above invention, the food residue is roughly pulverized with a cutter-type pulverizer, and further finely pulverized with a stone mortar-type pulverizer, and then mixed with the excess sludge by mixing means, so that the excess sludge and the food residue are uniformly distributed. Can be mixed. In addition, since this mixture tends to agglomerate excess sludge through finely pulverized food residues, it can be efficiently dehydrated by a dehydrator, and the work such as drying is omitted or simplified, and the solid content concentration of the mixture Can be increased. In addition, when fermented in the fermentation processing section, finely pulverized food residue is uniformly mixed with surplus sludge, so that surplus sludge is easily decomposed by microorganisms, promoting fermentation and increasing compost productivity. Can be increased.

  In the method for producing compost of the present invention, the dehydrator includes an outer trunk portion in which a plurality of annular plates are arranged, and a screw conveyor that is rotatably arranged on the inner periphery thereof and has spiral blades. It is preferable.

  According to the above aspect, since the dehydrator is a multi-plate screw press dehydrator, even a mixture of food residue and excess sludge can be efficiently dehydrated, and operations such as drying can be omitted or simplified. can do.

  According to the present invention, the food residue is roughly pulverized with a cutter pulverizer and further finely pulverized with a stone mortar pulverizer, and then mixed with excess sludge so that the excess sludge and food residue can be mixed uniformly. , The excess sludge can be easily aggregated through the finely pulverized food residue, the subsequent dehydration work can be easily performed, the solid content concentration of the mixture can be increased, and the fermentation is promoted To increase the productivity of compost.

It is a schematic explanatory drawing of the manufacturing method and manufacturing apparatus of the compost concerning this invention. It is explanatory drawing of the crushing process in the manufacturing method and manufacturing apparatus. It is explanatory drawing of the spin-drying | dehydration process in the manufacturing method and manufacturing apparatus.

  Hereinafter, an embodiment of a compost manufacturing apparatus according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the compost manufacturing apparatus according to this embodiment (hereinafter also simply referred to as “manufacturing apparatus”) is for manufacturing compost from surplus sludge generated by biological treatment of waste water and food residues. The cutter type pulverizer 10 for roughly pulverizing food residues, the mortar type pulverizer 20 for further finely pulverizing the food residues pulverized by the cutter type pulverizer 10, and the mortar type pulverizer 20 A mixing tank 30 for mixing surplus sludge with the food residue, a dehydrator 40 for dehydrating the mixture obtained in the mixing tank 30, and a fermentation processing unit for fermenting the mixture dehydrated by the dehydrator 40 to make compost. 50.

  In addition, although the food residue in this embodiment is a residue of a cut vegetable or a fishery product (for example, salmon roasted seaweed, seaweed paste), it may be other than these and is not particularly limited. .

  As shown in FIG. 2, the manufacturing apparatus includes a transfer unit 5 that transfers the food residue as described above at a predetermined speed. The transfer means 5 of this embodiment is arranged so that the start end portion 5a is arranged downward and the end portion 5b faces obliquely upward. For example, a screw conveyor can be adopted as the transfer means 5, but a belt conveyor or the like may be used as long as the food residue can be transferred.

  A cutter-type pulverizer 10 for coarsely pulverizing food residues is disposed downstream of the transfer means 5 (on the end portion 5b side). The cutter-type pulverizer 10 in this embodiment includes a bottomed cylindrical main body 11 provided with an upper opening 11a, and a rotary shaft 12 that is pivotally supported upward from the center of the bottom and rotated by a drive source (not shown). A plurality of rotary plates 13 fixed in the axial direction of the rotary shaft 12 and rotated as the rotary shaft 12 rotates, a rotary cutter 14 attached to the outer periphery of the rotary plate 13, and the rotary cutter 14 facing the rotary cutter 14 As shown, the fixed cutter 15 fixed to the inner periphery of the main body 11 and the chute 17 extending downward from the bottom of the main body 11 are provided. In addition, an end portion 5 b of the transfer means 5 is disposed above the upper opening 11 a of the main body 11.

  And the food residue thrown into the upper opening 11a of the cutter-type crusher 10 from the terminal part 5b of the transfer means 5 is fixed to the rotary cutter 14 provided on the outer periphery of the rotary plate 13 rotating via the rotary shaft 12. The cutter 15 is coarsely pulverized to a predetermined size. The coarsely pulverized food residue is discharged from the main body 11 through the chute 17 and transferred to the stone mill crusher 20.

  In addition, as a cutter type pulverizer as described above, for example, “disc cutter DC-2, DC-3” (trade name, manufactured by Glow Engineering Co., Ltd.) can be used. Moreover, as a cutter-type grinder, it is not limited to the said structure, What is necessary is just a grinder which has a cutter which can grind a food residue.

  On the downstream side of the cutter grinder 10 (here, the lower side of the cutter grinder 10), a stone mill grinder 20 for further finely grinding food residues is disposed. A stone mill crusher 20 in this embodiment includes a main body 21 provided with a hopper 21a having a substantially trumpet shape at the top, and a rotary shaft that is rotatably disposed at the center of the bottom of the main body 21 and is rotated by a drive source (not shown). 22, a substantially disc-shaped rotating grinder 23 fixed to the rotating shaft 22 and rotating with the rotation of the rotating shaft 22, and disposed above the rotating grinder 23 with a gap 25 therebetween. And a fixed grinder 24 having a substantially annular shape having an opening 24a at the center, and a chute 27 extending downward from the side wall of the main body 11. A concave portion 23 a is formed at the center of the rotating grinder 23. Further, the chute 17 of the cutter type pulverizer 10 is located above the hopper 21a.

  Then, the coarsely crushed food residue introduced into the main body 21 from the chute 17 of the cutter grinder 10 through the hopper 21a is supplied into the recess 23a of the rotating grinder 23 through the opening 24a of the fixed grinder 24. Is done. Further, the coarsely pulverized food residue enters the gap 25 between the rotating grinder 23 and the fixed grinder 24 by the centrifugal force of the rotating grinder 23 that rotates via the rotating shaft 22, and the rotating grinder 23 and the fixed grinder 24. It is designed to be crushed as if crushed. The finely pulverized food residue is discharged from the main body 21 through the chute 27, stored in the residue storage box 28, and transferred to a mixing tank 30 described later.

  In addition, as a stone mill type pulverizer as described above, for example, “Glow Mill” (trade name, manufactured by Glow Engineering Co., Ltd.) can be used. Further, the stone mill type grinder is not limited to the above structure, and may be any grinder having a grinder capable of finely grinding food residues.

  Moreover, it is preferable that the average particle diameter of the food residue coarsely pulverized by the cutter pulverizer 10 is 3 to 10 mm, and more preferably 3 to 5 mm. In addition, in this invention, an average particle diameter means the 50% mass value obtained by plotting the integrated mass after classifying with a sieve on a graph.

  Moreover, it is preferable that the average particle diameter of the food residue finely pulverized by said stone mill type | mold grinder 20 is 0.1-0.8 mm, and it is more preferable that it is 0.1-0.4 mm.

  Next, the mixing means will be described. This mixing means has a mixing tank 30 having a predetermined stirring device. Further, on the upstream side of the mixing tank 30, a sludge storage tank 31 and a sludge metering tank 32 are arranged. In the sludge storage tank 31, excess sludge generated by biological treatment of organic wastewater such as sewage is stored. In addition, a sludge measuring tank 32 is connected to the sludge storage tank 31 via a pipe L1. The sludge metering tank 32 is connected to the mixing tank 30 via a pipe L2 and is connected to the sludge storage tank 31 via a pipe L3.

  The surplus sludge supplied from the sludge storage tank 31 to the sludge metering tank 32 is metered according to the supply amount of the food residue finely pulverized by the stone mill crusher 20 to the mixing tank 30. Thus, it is supplied to the mixing tank 30 via the pipe L2. In addition, the surplus sludge more than a required amount is returned to the sludge storage tank 31 via the pipe L3. Further, a flocculant addition device 33 for supplying a flocculant (for example, an anionic polymer flocculant, a cationic polymer flocculant, etc.) is connected to the mixing tank 30 via a pipe L4. And the surplus sludge supplied to the mixing tank 30 and the food residue finely pulverized by the stone mill crusher 20 are mixed in a state where the flocculant is added, so that a mixture is generated. .

  A dehydrator 40 for dehydrating the mixture is disposed on the downstream side of the mixing tank 30. As shown in FIG. 3, the dehydrator 40 in this embodiment includes an outer body portion 43 in which a plurality of annular plates 44 and 45 are disposed, and a rotatable blade 46b disposed on the inner periphery thereof. A multi-plate screw press dehydrator having a screw conveyor 46 is provided.

  More specifically, the dehydrator 40 has a horizontally long main body 41, and an outer body 43 is disposed in the main body 41. The outer body portion 43 includes a large-diameter annular plate 44 arranged at predetermined intervals along the axial direction (longitudinal direction of the main body 41), and a plurality of small-diameter annular plates 45 interposed therebetween. It is arranged so that it can move freely. The screw conveyor 46 disposed in the outer body 43 has a rotation shaft 46a rotatably supported at both ends in the longitudinal direction of the main body 41 and rotated by a driving means (not shown). The rotation shaft 46a Is provided with a spiral blade 46b. When the screw conveyor 46 rotates, the spiral blade 46b comes into sliding contact with the inner peripheral surface of the small-diameter annular plate 45, and the annular plate 45 rotates eccentrically. As a result, the mixture that enters the outer body 43 and is transferred by the screw conveyor 46 is compressed by the annular plates 44 and 45 and the screw conveyor 46 to be dehydrated. In addition, the water dehydrated from the mixture is drained from the gap between the annular plate 44 and the annular plate 45.

  In addition, a charging pipe 41a for charging the mixture is provided above one end in the longitudinal direction of the main body 41, and water dehydrated from the mixture is discharged to the lower side near the one end in the longitudinal direction of the main body 41. A drain pipe 41b is provided. Further, a chute 47 for discharging the dehydrated mixture is provided below the other longitudinal end of the main body 41. The dehydrator 40 is installed in an inclined state so that the mixture input side (input pipe 41a side) is downward and the mixture discharge side (chute 47 side) is upward.

  Then, the mixture charged into the main body 41 via the charging pipe 41a is transferred into the outer trunk 43 by the screw conveyor 46, and proceeds to the downstream side in the outer trunk 43 in the above process. As described above, the water is dehydrated by the compression action of the annular plates 44 and 45 and the screw conveyor 46 and discharged from the chute 47, and the water dehydrated from the mixture is drained from the main body 41 through the drain pipe 41b. The dehydrated mixture is accommodated in the mixture accommodation box 49 via the chute 47 and transferred to the fermentation processing unit 50.

  With the dehydrator 40, the water content of the mixture of the food residue and the excess sludge is preferably 90 to 99% by mass, and more preferably 95 to 98% by mass. By setting it as such moisture content, it becomes possible to perform the fermentation process for compost manufacture, without drying a mixture or simplifying drying operation.

  As the multi-plate screw press dehydrator, for example, “Multi-plate screw press sludge dehydrator STP series” (trade name, manufactured by Shin Meiwa Kogyo Co., Ltd.) can be used. Further, the structure of the multi-plate screw press dehydrator is not limited to the above structure. Further, in this embodiment, a multi-plate screw press dehydrator is adopted as the dehydrator. However, for example, a belt press type, a vacuum type, a centrifugal type, or the like may be used. There is no limitation.

  The fermentation processing unit 50 is disposed on the downstream side of the dehydrator 40, receives the mixture dehydrated by the dehydrator 40, and aerates the mixture to ferment the mixture into compost. . In addition, an aeration blower 51 is connected to the fermentation processing unit 50 so that air is sent in.

  Next, an embodiment of a method for producing compost according to the present invention using the above manufacturing apparatus will be described.

  This compost manufacturing method includes a coarse pulverization step of pulverizing food residues with a cutter pulverizer 10, a fine pulverization step of further pulverizing the residue obtained in the coarse pulverization step with a stone mortar pulverizer 20, and fine pulverization. A mixing step of mixing surplus sludge with the food residue pulverized in the step, a dehydration step of dehydrating the mixture obtained in the mixing step with a dehydrator 40, and a fermentation step of fermenting the mixture dehydrated in the dehydration step into compost Is included.

  That is, first, the food residue is introduced into the starting end portion 5a of the transfer means 5 and transferred at a predetermined speed, and from the terminal end portion 5b, the food residue is introduced into the upper opening 11a of the cutter grinder 10 (see FIG. 2).

  And the input food residue is coarsely pulverized to a predetermined size by the rotary cutter 14 provided on the outer periphery of the rotary plate 13 rotating via the rotary shaft 12 and the fixed cutter 15 (coarse pulverization step).

  The coarsely pulverized food residue is fed from the hopper 21a of the stone mill crusher 20 through the chute 17. This food residue is supplied into the concave portion 23a of the rotating grinder 23 through the opening 24a of the fixed grinder 24, and enters the gap 25 between the rotating grinder 23 and the fixed grinder 24 by the centrifugal force of the rotating grinder 23. Grinded with grinders 23 and 24 and finely pulverized to a predetermined size (a fine pulverization step). The finely pulverized food residue is accommodated in a residue accommodating box 28 via a chute 27 and transferred to a mixing tank 30 as a mixing means. In addition, it is preferable that the moisture content of the pulverized food residue is adjusted to a range of 90 to 99% by mass.

  On the other hand, surplus sludge generated by biological treatment of wastewater is once stored in the sludge storage tank 31 and supplied to the sludge measurement tank 32 via the pipe L1, and the required amount is measured in the sludge measurement tank 32, It is supplied to the mixing tank 30 via the pipe L2. Further, the flocculant is supplied from the flocculant adding device 33 to the mixing tank 30 through the pipe L4. In addition, it is preferable that the moisture content of the surplus sludge supplied is adjusted to 90-99 mass%.

  And in the mixing tank 30 which is a mixing means, a surplus sludge is mixed with the food residue obtained at the fine grinding | pulverization process in the state which added the flocculant, and a mixture is produced | generated (mixing process). In addition, the mixing ratio (mass ratio) of food residue and surplus sludge is not particularly limited, but food residue: surplus sludge = 1: 1 to 5 is preferable, and food residue; surplus sludge = 1: 1 to 3 is more preferable. . Moreover, it is preferable that the water content of a mixture is adjusted to 90-99 mass%.

  Next, the mixture obtained in the mixing step is charged into the main body 41 through the charging pipe 41a of the dehydrator 40 (see FIG. 3). The mixture is transferred into the outer body 43 by the screw conveyor 46 and dehydrated by the compression action of the annular plates 44 and 45 and the screw conveyor 46 in the process of proceeding downstream in the outer body 43 (dehydration process). ). The dehydrated mixture is accommodated in the mixture accommodating box 49 via the chute 47 and transferred to the fermentation processing unit 50. In addition, when the water content of the dehydrated mixture is still high, it may be dried by an appropriate method to reduce the water content, and then transferred to the fermentation treatment unit 50. Further, the water content of the mixture dehydrated by the dehydrator 40 is preferably 70 to 90% by mass, and more preferably 75 to 85% by mass.

  And in the fermentation process part 50, a mixture can be fermented by aeration with the air supplied from the aeration blower 51, and compost can be obtained (fermentation process). Fermentation may be performed by a conventional method, but compost suitable as a fertilizer can be produced by, for example, fermenting for 60 to 90 days. The moisture content of the finally obtained compost is preferably 40 to 80% by mass, and more preferably 40 to 60% by mass.

  As described above, in the method for producing compost, the food residue is coarsely pulverized by the cutter type pulverizer 10 and further finely pulverized by the stone mortar type pulverizer 20 and then mixed with the excess sludge. And the food residue can be mixed uniformly with little variation, and excess sludge can be easily aggregated through the finely pulverized food residue, so that the dehydration work in the subsequent dehydration process can be easily performed. be able to. That is, after coarsely pulverizing with the cutter-type pulverizer 10 and finely pulverizing the food residue with the stone mortar-type pulverizer 20, the particle size of the food residue can be easily made uniform. A small and uniform mixture of food residue and excess sludge can be obtained. As a result, operations such as drying after dehydration can be omitted or simplified, and the solid content concentration of the mixture can be increased. Moreover, since the finely pulverized food residue is uniformly mixed with surplus sludge that is not easily decomposed by microorganisms, fermentation can be promoted to increase the productivity of compost.

  Further, in this embodiment, the dehydrator 40 in the dehydration step is arranged to be rotatable on the outer body portion 43 in which a plurality of annular plates 44 and 45 are disposed, and on the inner periphery thereof, and the spiral blade 46b is provided. Since it is a multi-plate screw press dehydrator having a screw conveyor 46, it can be efficiently dehydrated even if it is a mixture of food residue and surplus sludge, and the solid content concentration can be obtained without going through a drying step or the like. Can be obtained.

  Furthermore, in this embodiment, since the food residue is a residue of cut vegetables or processed fishery products, these can be utilized without waste, and fermentation when mixed with excess sludge can be promoted.

  It should be noted that the present invention is not limited to the above-described embodiment, and various modified embodiments are possible within the scope of the present invention, and such an embodiment is also included in the scope of the present invention. .

DESCRIPTION OF SYMBOLS 5 Transfer means 5a Start part 5b Termination part 10 Cutter-type crusher 11 Main body 11a Upper opening 12 Rotating shaft 13 Rotating plate 14 Rotating cutter 15 Fixed cutter 17 Chute 20 Stone mill crusher 21 Main body 21a Hopper 22 Rotating shaft 23 Rotating grinder 23a Recessed part 24 fixed grinder 24a opening 25 gap 27 chute 28 residue storage box 30 mixing tank 31 sludge storage tank 32 sludge metering tank 33 flocculant addition device 40 dehydrator 41 main body 41a input pipe 41b drain pipe 43 outer body 44, 45 annular plate 46 Screw conveyor 46a Rotating shaft 46b Blade 47 Chute 49 Mixture storage box 50 Fermentation processing section 51 Aeration blower L1 Piping L2 Piping L3 Piping L4 Piping

Claims (5)

A method for producing compost from surplus sludge generated by biological treatment of wastewater and food residues,
A coarse pulverization step of pulverizing the food residue with a cutter pulverizer;
A fine pulverization step of further pulverizing the residue obtained in the coarse pulverization step with a stone mill type pulverizer;
A mixing step of mixing the surplus sludge with the food residue pulverized in the fine pulverization step;
A dehydration step of dehydrating the mixture obtained in the mixing step with a dehydrator;
A fermentation step of fermenting the mixture dehydrated in the dehydration step into compost;
The compost manufacturing method characterized by including.   The dehydrator in the dewatering step is a multi-plate screw press dehydrator having an outer body portion in which a plurality of annular plates are disposed, and a screw conveyor that is rotatably disposed on the inner periphery thereof and has spiral blades. The method for producing compost according to claim 1.   The method for producing compost according to claim 1, wherein the food residue is a residue of cut vegetables or processed fishery products. An apparatus for producing compost for producing compost from surplus sludge generated by biological treatment of wastewater and food residues,
A cutter grinder for roughly crushing the food residue;
A stone mill crusher for further finely crushing the food residue crushed by the cutter crusher;
A mixing means for mixing the surplus sludge with the food residue crushed by the stone mill crusher;
A dehydrator for dehydrating the mixture obtained by the mixing means;
A fermentation processing unit for fermenting the mixture dehydrated by the dehydrator into compost;
An apparatus for producing compost, comprising:   The dehydrator is a multi-plate screw press dehydrator having an outer body portion in which a plurality of annular plates are disposed, and a screw conveyor rotatably disposed on an inner periphery thereof and having spiral blades. Item 4. A compost production apparatus according to Item 4.

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