JP5745120B1 - Methane fermentation method and methane fermentation system - Google Patents

Abstract

[PROBLEMS] To improve separation efficiency of litter from organic waste containing litter and feces, to improve litter crushing efficiency, to increase the amount of biogas produced by methane fermentation, and to further improve methane fermentation To provide a methane fermentation method and a methane fermentation system capable of increasing the utility value of later digestive juice and reducing the amount of waste. SOLUTION: A first litter separating step 2 for separating a litter from organic waste containing litter and feces, a crushing step 3 for crushing the litter separated in the first litter separating step 2, and a first litter separation. Digestion generated in methane fermentation process 5 and methane fermentation process 5 in which the organic waste after separation of the litter in process 2 and the litter crushed in crushing process 3 are introduced into a methane fermentation tank and methane fermented A second litter separating process 6 for separating the litter from the liquid, and the digested liquid after the litter is separated in the second litter separating process 6 is used as an organic waste for the first litter separating process 2 Methane fermentation method and methane fermentation system to be added. [Selection] Figure 1

Description

  The present invention relates to a methane fermentation method and a methane fermentation system, and more particularly, to a methane fermentation method and a methane fermentation system in which an organic waste containing a litter and feces is processed to perform methane fermentation.

  In Patent Document 1, in a method of subjecting organic waste containing a large amount of cellulosic fibers to methane fermentation, the organic waste or a treatment liquid obtained by subjecting the organic waste to methane fermentation is treated with other methods. It is disclosed that after mixing the water with a small amount of solids, solid-liquid separation and / or dehydration, pulverizing the obtained solids in the pulverization step, and then charging the pulverized solids into the methane fermentation step. Yes.

  Patent Document 1 may be any water that has a small amount of suspended solids, but is preferably treated water in a subsequent water treatment step of methane fermentation, such as activated sludge treated water. It is said.

JP 2002-248448 A

  Bedding is placed in the breeding space for livestock. At this time, feces excreted on the litter adhere to the litter.

  The inventor has already found that the methane fermentation efficiency of the bedding can be improved by crushing the bedding in advance when the bedding is methane-fermented with the organic waste.

  When crushing the litter, it is preferable to separate the litter from the organic waste, but it is difficult to peel off the dung if it is attached to the litter.

  The crushing efficiency at the time of crushing the bedding is reduced by moisture brought in by feces. In particular, it has been found that when a rotary crusher is used as the crushing means, the reduction in crushing efficiency is significant.

  When separating the litter from the organic waste, the present inventor tried to add water to the organic waste so that the feces can be easily separated from the litter.

  Thereby, it became clear that feces were easily peeled off from the litter, the separation efficiency of the litter was improved, and the efficiency of crushing the litter could be improved.

  However, it has been found that this process causes a new problem that a large amount of diluted thin digestive juice is produced as a digestive juice after the subsequent methane fermentation because water is newly added. As a result, for example, when the digestive juice is sprayed on the farmland as liquid fertilizer, the thin digestive fluid must be sprayed in a large amount, so that the efficiency of the spraying work is impaired. In addition, the amount of disposal when discarding is increased. In addition, this process has room for further improvement from the viewpoint of increasing the amount of biogas produced by methane fermentation.

  As a result of intensive studies by actually conducting tests, the present inventor added water by adding a digested liquid after methane fermentation to the organic waste when separating the bedding from the organic waste. It has been found that it is possible to make it easier to peel feces from the bedding, as in the case of the above.

  Not only the digestive liquid added in this way, but the digestive liquid after the methane fermentation in the latter stage is small and thick compared to the process of adding water or the like described above. It was found that not only improvement and reduction of waste amount can be realized, but also the amount of biogas produced by methane fermentation can be increased.

  Furthermore, when the digested liquid after methane fermentation is subjected to methane fermentation again, undigested organic matter is well decomposed, and the value as a fertilizer such as liquid fertilizer can be increased.

  It has also been confirmed that the above-described effect becomes remarkable particularly when a digestive liquid having a TS (total solid content) of 3% or more is added.

  Therefore, the problem of the present invention is that it is possible to improve the separation efficiency of the litter from the organic waste containing the litter and feces, to improve the crushing efficiency of the litter, and to increase the amount of biogas generated by methane fermentation. Furthermore, it is providing the methane fermentation method and methane fermentation system which can raise the utility value of the digestive liquid after methane fermentation, and can reduce a discard amount.

  Still other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

(Claim 1)
A first litter separating step of separating the litter from organic waste containing litter and feces;
A crushing step of crushing the litter separated in the first litter separation step;
A methane fermentation process in which the organic waste after the litter is separated in the first litter separation process and the litter crushed in the crushing process are introduced into a methane fermentation tank to perform methane fermentation;
A second litter separating step for separating the litter from the digestive juice produced in the methane fermentation step,
The methane fermentation method, wherein the digested liquid after the bedding is separated in the second litter separation step is added to the organic waste to be used in the first litter separation step.

(Claim 2)
2. The methane fermentation method according to claim 1, wherein the digested liquid after the bedding is separated in the second bedding separating step has a TS of 3% or more.

(Claim 3)
The methane fermentation method according to claim 1 or 2, wherein in the crushing step, a rotary crusher is used as a crushing means.

(Claim 4)
The method for methane fermentation according to any one of claims 1 to 3, wherein the litter separated in the second litter separating step is reused as a litter.

(Claim 5)
First litter separating means for separating the litter from organic waste containing litter and feces;
Crushing means for crushing the litter separated by the first litter separating means;
A methane fermentation tank for introducing methane fermentation by introducing the organic waste after the litter is separated by the first litter separating means and the litter crushed by the crushing means;
And a second bedding separating means for separating the bedding from the digestive juice produced by the methane fermentation in the methane fermentation tank,
The methane fermentation system, wherein the digested liquid after the bedding is separated by the second bedding separating means is added to the organic waste provided to the first bedding separating means.

(Claim 6)
6. The methane fermentation system according to claim 5, wherein the digested liquid after the bedding is separated by the second bedding separating means has a TS of 3% or more.

(Claim 7)
The methane fermentation system according to claim 5 or 6, wherein the crushing means is a rotary crusher.

(Claim 8)
The methane fermentation system according to any one of claims 5 to 7, wherein the bedding separated by the second bedding separating means is reused as a bedding.

  According to the present invention, the separation efficiency of the litter from the organic waste containing litter and feces can be improved, the crushing efficiency of the litter can be improved, the amount of biogas produced by methane fermentation can be increased, and Further, it is possible to provide a methane fermentation method and a methane fermentation system that can increase the utility value of digested liquid after methane fermentation and reduce the amount of waste.

The block diagram which shows an example of the methane fermentation method of this invention Explanatory drawing showing the basic configuration of the rotary crusher Figure to verify fecal peeling action The figure explaining the methane fermentation method of an Example The figure explaining the methane fermentation method of a reference example Figure showing examples of bedding fragments Figure to verify the size of bedding fragments and methane fermentation efficiency

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an example of the methane fermentation method of the present invention.

  In FIG. 1, 1 is a digestive liquid addition process, 2 is a 1st litter separation process, 3 is a crushing process, 4 is a mixing process, 5 is a methane fermentation process, 6 is a 2nd litter separation process.

  In the illustrated methane fermentation method, organic waste containing bedding and feces is used as a raw material. Preferred examples of feces include feces from animals such as cows, pigs, and horses. The bedding is not particularly limited as long as it consists of herbaceous biomass (soft biomass), and examples thereof include rice straw, wheat straw (hereinafter sometimes referred to as wheat straw), and grass. The bedding can be preferably used after use, that is, with the above-mentioned feces attached.

  In the digestive liquid addition process 1, the digestive liquid produced | generated with the methane fermentation is added to organic waste. This digestive juice will be described in detail later.

  In the digestive fluid addition step 1, the means for adding the digestive fluid to the organic waste is not particularly limited. The digestive liquid may be simply added to the organic waste, but it is also preferable to mix the organic waste and the digestive liquid using, for example, a mixing tank or a mixing and stirring tank. As the separating means used in the first litter separating step 2 in the subsequent stage, it is also preferable to use one having an action of mixing organic waste and digestive juice.

  The amount of digestive juice added to 100 parts by weight of organic waste is not particularly limited, but is preferably in the range of 10 parts by weight to 1000 parts by weight, for example. Moreover, it is also preferable that the addition amount of digestive juice is adjusted so that the moisture content after mixing the digestive juice becomes a predetermined moisture content or a moisture content equal to or higher than a predetermined value. As an example, for an organic waste (raw material) having a water content of 85% or less, the water content after mixing the digestion liquid is 88% or more, preferably 90% or more, and most preferably 95% or more. It is also preferable to add digestive juice.

  In the first litter separation step 2, the litter is separated from the organic waste to which the digestive juice is added in the digestive fluid addition step 1.

  Due to the action of the digestive fluid, feces are easily peeled off from the bedding, so that the efficiency of separating the bedding from the organic waste is improved. Thereby, it can also prevent that a water | moisture content is brought in by feces and the effect of reducing the moisture content of a litter can also be acquired.

  The first litter separating means for separating litter from organic waste is not particularly limited. For example, screw press dewatering machine, filter press dewatering machine, belt press dewatering machine, centrifugal dewatering machine, multiple disk dewatering machine, roller press A dehydrator, a Wavy press dehydrator, or the like can be preferably used. In particular, the screw press dehydrator is preferable because it suitably exhibits the action of mixing the organic waste and the digestive juice, and the fecal exfoliation action of the digestive juice is easily exhibited.

  In the crushing step 3, the litter separated in the first litter separating step 2 is crushed.

  The litter provided for the crushing step 3 can be efficiently crushed because feces are suitably separated in the first litter separating step 2.

  The crushing means for crushing the litter is not particularly limited. For example, a ball mill crusher, a stone mill crusher, a cutting machine, a rotary crusher, or the like can be preferably used, and a rotary crusher is particularly preferable. The rotary crusher will be described in detail later.

  The size (length) of the litter after crushing is not particularly limited, but is preferably a fragment having a length of 100 mm or less. For example, the particles may be pulverized until the particle size is on the order of microns (specifically, for example, less than 1 mm), but more preferably 1 mm or more. Most preferably, the litter of fragments of 10 mm to 100 mm in length, preferably 10 mm to 50 mm in length occupies the majority (50% by weight or more) of the entire litter.

  The present inventor has shown that even a relatively large bedding piece having a length of 10 mm to 100 mm, preferably 10 mm to 50 mm, generates a sufficient amount of biogas by the subsequent methane fermentation. Heading. In addition, since the bedding pieces have a certain length, the bedding after methane fermentation can be suitably reused as bedding and the like. Such a bedding after methane fermentation is less hygienic and less sanitary because organic matter is decomposed by methane fermentation.

  In particular, a rotary crusher can be preferably used from the viewpoint of efficiently obtaining a relatively large litter piece having a length of 10 mm to 100 mm, preferably a length of 10 mm to 50 mm. In particular, since the rotary crusher is easily affected by feces adhering to the litter, the effect of improving the crushing efficiency due to the feces being peeled from the litter is great.

  In the mixing step 4, the organic waste after the bedding is separated in the first bedding separating step 2 and the bedding crushed in the crushing step 3 are mixed.

  The mixing means is not particularly limited. For example, a methane fermentation tank used in the subsequent methane fermentation step 5 may also be used. Alternatively, it is also preferable to separately provide a mixing tank or a mixing agitation tank and mix them in advance before introducing them into the methane fermentation tank.

  In the methane fermentation process 5, the organic waste after the bedding is separated in the first bedding separation process 2 and the bedding crushed in the crushing process 3 are introduced into a methane fermentation tank and subjected to methane fermentation.

  The temperature of methane fermentation is not particularly limited as long as it is a temperature at which methane fermentation proceeds (usually 35 ° C. or higher). For example, any type such as a so-called medium temperature type, high temperature type, and ultra high temperature type can be applied. In the present invention, fermentation is preferably performed at a temperature of 50 ° C. or higher and 70 ° C. or lower. At this temperature, it becomes possible to sterilize germs and the like, so that the hygiene of the bedding separated from the digested liquid after methane fermentation can be improved, and the utility value as a bedding can be increased.

  In this invention, since the digestive liquid after methane fermentation is added in the digestive liquid addition process 1 to the organic waste provided to the 1st bedding separation process 2 mentioned above, the methane fermentation in the methane fermentation process 5 In this case, the fuel cost can be reduced. That is, compared with water (for example, 10 ° C.) or activated sludge water (usually 20 ° C.), the digestive juice produced from methane fermentation is the temperature in the methane fermentation tank (as described above, usually 35 ° C. or higher, Preferably it is in a relatively high temperature state derived from 50 ° C. or more and 70 ° C. or less. For example, the digested liquid extracted from the methane fermentation tank and added in the digested liquid adding step 1 preferably easily maintains a temperature of 30 ° C. or higher, more preferably 40 ° C. or higher, and most preferably 50 ° C. or higher. Can be made. Accordingly, it is possible to reduce the amount of heat when heating the organic waste for methane fermentation as compared with the case where water or activated sludge is added, thereby reducing the fuel cost.

  Methane fermentation is preferably continued for 5 days or longer, more preferably 10 days or longer, and most preferably 15 days or longer. The methane fermentation may be a batch type or a continuous type. When the methane fermentation is performed continuously, the average residence time in the fermenter corresponds to the duration of the methane fermentation.

  Biogas and digestive fluid are produced with methane fermentation.

  Since the bedding introduced into the methane fermentation tank as a raw material is crushed in the crushing step 3, a sufficient amount of biogas can be generated by methane fermentation.

  Moreover, the digestive juice produced | generated with the methane fermentation in the methane fermentation process 5 is small and thick compared with the process which adds the water etc. mentioned above by the effect | action of the digestive juice added in the digestive juice addition process 1. Can be. Thereby, the improvement of the spraying work efficiency as liquid manure, for example, and reduction of the amount of disposal can be realized. Furthermore, the effect which can further increase the gas amount of the biogas produced | generated by methane fermentation compared with the process which adds the water etc. mentioned above is also acquired.

  In addition, when the digested liquid after methane fermentation is subjected to methane fermentation again, the undigested organic matter is well decomposed, and the value as a fertilizer such as liquid fertilizer can be increased.

  For example, the biogas can be collected and temporarily stored in a gas holder as necessary, and then purified by a refining facility and used as power for a generator. It is also preferable to use the electric power obtained in this way for electric power sales.

  In the second bedding separation step 6, the bedding (the bedding after fermentation) is separated from the digested liquid generated along with the methane fermentation in the methane fermentation step 5.

  The second litter separating means that can be adopted in the second litter separating step 6 is not particularly limited, and for example, the same thing as the first litter separating means that can be adopted in the first litter separating step 2 can be used. A screw press dehydrator is particularly suitable.

  It is preferable to collect and reuse the separated litter. In particular, it can be suitably reused as a bedding material.

  A part of the digestive liquid after the bedding is separated is returned to the above-described digestive liquid addition step 1 and added to the organic waste. The other part of the digestive juice can be used as a fertilizer such as liquid fertilizer or added to feed. By reusing the digestive liquid in this way, the amount of digested liquid discarded can be further reduced.

  The digested liquid after the bedding has been separated preferably has a TS of 3% or more. When TS is 3% or more, the amount of biogas produced by methane fermentation can be further increased. In addition, digestive juice having a TS of 3% or more also exhibits an excellent nutritional effect when used as a fertilizer such as liquid fertilizer or added to a feed or the like. Therefore, the utility value of the digested liquid after methane fermentation can be further increased, and the amount of waste can be further reduced.

  It is also preferable to return the digested liquid to the mixing tank or the mixing and stirring tank used in the mixing step 4.

  According to the present invention, since the digestive juice can be suitably recycled as described above, it is possible to reduce the load of processing the digestive juice by wastewater treatment or the like. The digested liquid after methane fermentation may be returned to the upstream process as described above, and the remaining digested liquid may be used as a fertilizer to effectively use the entire amount of the digested liquid.

  Next, the rotary crusher preferably used as the crushing means in the crushing step 3 will be described in detail.

  FIG. 2 is an explanatory diagram showing a basic configuration of the rotary crusher.

  In FIG. 2, 30 is a rotary crusher, 31 is a chamber, 32 is a rotating shaft, 33 is a rotating element, 34 is a mounting portion, and 35 is a motor.

  In the rotary crusher 30, a rotary shaft 32 is provided near the center of the bottom in a chamber 31 having an internal space, and a rotary element 33 formed of a chain is attached to a mounting portion 34 formed at the tip of the rotary shaft 32. Is attached.

  When an object to be processed (the solid phase separated in the first litter separating step 1 described above and including at least the litter) is introduced into the chamber 31, the rotating element 33 that rotates and acts on the centrifugal force is rotated. Collide with. As a result, the bedding is crushed and fragmented.

  By appropriately setting the operating conditions, it is possible to easily generate a litter crushed into 10 mm to 100 mm pieces as a workpiece.

  The rotating element 33 is not limited to a chain, and may be a chain or a blade. The radius of rotation of the rotating element 33 (the length from the center of rotation to the outer peripheral end) is not particularly limited, but is preferably in the range of 50 cm to 200 cm.

  As an example of operating conditions, by setting the rotation speed of the rotating shaft to 800 to 1600 rpm and the processing time to 25 to 40 seconds (total of charging time 10 seconds, crushing time 5 seconds to 20 seconds, and discharging time 10 seconds) It becomes possible to suitably generate a litter crushed into 10 mm to 100 mm pieces.

  In particular, since the rotary crusher as described above is easily affected by feces adhering to the litter, the effect of improving crushing efficiency due to peeling of the feces from the litter is great.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

1. Solid-liquid separation test (test to peel feces from litter) 1
Example 1
Digestive liquid (TS = 4%) generated during methane fermentation is added to organic waste (raw material) containing feces and litter (rice bran of rice), and the organic matter is removed using a screw press. The bedding was separated from the toxic waste. Table 1 shows the results of measuring the weight, TS, and VS (incineration loss (organic matter amount)) for each of the raw materials (including digestive fluid), the separated litter, and the organic waste after the litter was separated. Shown in

(Comparative Example 1)
In Example 1, the litter was separated in the same manner as in Example 1 except that the digestive juice was not added. Table 1 shows the results of measuring the weight, TS, and VS for each of the raw material, the separated bedding, and the organic waste after the bedding was separated.

<Evaluation>
From Table 1, it can be seen that in Example 1 in which the digestive juice was added to the organic waste, the moisture content could be reduced (high TS and VS) because the separation efficiency of the litter was excellent and less water was brought in by the feces. .

  On the other hand, in the case where nothing is added (Comparative Example 1), since the separation of the feces is insufficient, the separation efficiency of the bedding is inferior, and there is a limit to the reduction of the moisture content due to the moisture brought in by the feces (TS, (VS is small).

  In addition, it was confirmed that the same results were obtained even when the rice bran (rice straw) used as the bedding material in the above tests was replaced with wheat straw and pasture.

  From the above, according to the present invention, it was confirmed that the separation efficiency of the bedding from the organic waste containing the bedding and feces can be improved, and the crushing efficiency of the bedding can be improved.

2. Solid-liquid separation test (test to peel feces from litter) 2
(Example 2)
As a raw material, a litter (rice bran) with adult cow dung was prepared. The water content of the raw material is 85%.

  Digested liquid (TS = 4.6%) was added to this raw material, and the mixture was uniformly mixed by stirring to obtain a mixture.

  At this time, the addition amount of the digestive liquid with respect to a raw material was adjusted so that the moisture content of a mixture might become the value (88%., 90% or 95%) shown in Table 2, and the mixtures 1-3 from which a moisture content differs, respectively. Got.

  Next, the mixtures 1 to 3 were subjected to solid-liquid separation using a filter having a pore diameter of 1 mm, and the amount of feces (= TS) in the liquid was measured for the obtained desorbed liquid (liquid side fraction).

  From the measured value, the fecal adhesion rate (%) to the litter after solid-liquid separation was determined based on the following formula.

A (%) = ([B ₀ −B ₁ ] / B ₀ ) × 100
In the above formula, A is the fecal adhesion rate (%) to the litter after solid-liquid separation, B ₀ is the feces TS (kg) in the original raw material (the litter with the feces adhered), and B ₁ is It is feces TS (kg) in the detachment liquid after solid-liquid separation.

  FIG. 3 shows the relationship between the moisture content (%) of the mixtures 1 to 3 and the fecal adhesion rate (%) to the bedding after solid-liquid separation. In the graph of FIG. 3, the horizontal axis represents the moisture content (%) of the mixture before solid-liquid separation, and the vertical axis represents the fecal adhesion rate (%) to the litter after solid-liquid separation.

(Reference Example 1)
In Example 2, water was used in place of the digestive juice, and the amount of water added to the raw material was adjusted so that the water content of the mixture was the value shown in Table 3 (88%, 90%, or 95%). Mixtures 4 to 6 having different moisture contents were obtained.

  Similarly to Example 2, the relationship between the moisture content (%) of the mixtures 4 to 6 and the fecal adhesion rate (%) to the bedding after solid-liquid separation is shown in FIG.

<Evaluation>
FIG. 3 shows that in the comparison system of digestive juice and water, the fecal adhesion rate depends on the moisture content, and when compared at the same moisture content, Example 2 to which the digestive juice was added and water It can be seen that there is no substantial difference in the fecal adhesion rate in Comparative Example 2 to which is added. From this, it can be seen that by adding the digestive fluid, it is possible to achieve the same fecal adhesion rate as when water is added.

  Furthermore, the addition of digestive juice can have a positive effect on the overall methane fermentation process compared to the case of adding water. This becomes clear from the verification in the following “3. Methane fermentation test”.

  In addition, it was confirmed that the same results were obtained even when the rice bran (rice straw) used as the bedding material in the above tests was replaced with wheat straw and pasture.

3. Methane fermentation test (Example 3)
According to the methane fermentation method shown in FIG. 1, methane fermentation was performed using an organic waste containing a litter (rice bran) with feces attached as a raw material.

  Table 4 shows the mass balance (wet weight (t), moisture content (%), TS (%), and TS (t)) in each process (A to H in FIG. 4).

A to H correspond to the following, respectively.
A: Raw material B: Digestive liquid added in the digestive liquid addition step C: Raw material provided to the first bedding separation process 2 after the addition of the digestive liquid D: Biogas (CH ₄₎ generated from the methane fermentation process 5 ; 55%)
E: Digestive fluid produced from methane fermentation process 5 F: Fraction fraction separated in second litter separation process 6 (litter material)
G: Digestive liquid after the bedding has been separated H: Liquid fertilizer (digested liquid excluding the portion returned to the digestive liquid addition step 1)

(Reference Example 2)
Using the same raw material as in Example 3, methane fermentation was performed by the methane fermentation method shown in FIG.

  In FIG. 5, 101 is a digestive fluid addition process, 102 is a first litter separation process, 103 is a crushing process, 104 is a mixing process, 105 is a methane fermentation process, and 106 is a second litter separation process. That is, in Example 3, the digestive juice addition step 1 is not provided, but instead, a water addition step 101 for adding water to the raw material is provided.

  The raw material (the raw material mixed with the digestive liquid) supplied to the first bedding separation step 2 of Example 1 and the raw material (the raw material mixed with water) supplied to the first bedding separation step 102 of Reference Example 2 Then, the water content was evaluated under the same conditions. Therefore, the amount of water added to the raw material in the water addition step 101 is adjusted to be smaller than the amount of the digestive fluid added in the digestive fluid addition step 1 of Example 3.

  Table 5 shows the mass balance (wet weight (t), moisture content (%), TS (%), and TS (t)) in each stage of the process (A ′ to H ′ in FIG. 5).

A ′ to H ′ correspond to the following, respectively.
A ′: Raw material B ′: Water added in the water addition step 101 C ′: Raw material used in the first bedding separation step 102 after the addition of water D ′: Biogas generated from the methane fermentation step 105 (CH ₄ ; 55%)
E ′: Digestive fluid generated from the methane fermentation step 105 F ′: Fraction fraction separated in the second litter separation step 106 (litter material)
G ′: Digested liquid after the bedding has been separated H ′: Liquid fertilizer

<Evaluation>
In Example 3 in which the digestive juice was added, the amount of liquid fertilizer was reduced and the time and effort of spraying was reduced compared to Reference Example 2 in which water was added, or the treatment facility capacity can be reduced when drainage treatment is selected. It can be seen that the above effects can be obtained. Furthermore, in Example 3, as compared with Reference Example 2, it was confirmed by an additional test that liquid fertilizer contains a large amount of low molecular weight organic substances that are not detected as TS. Such low molecular weight organic matter is presumed to have been produced as a result of digestion of the digested liquid again to methane fermentation, resulting in good digestion of undegraded organic matter. It enhances value.

Furthermore, in Example 3, compared with Reference Example 2, it was confirmed that the amount of biogas generated in methane fermentation was increased (Reference Example 2; 34.1 m ³ → Example 3; 34.8 m ³ ). .

  Furthermore, compared with the reference example 2, in Example 3, there also exists a merit which can reduce water usage-amount.

  Combined with the verification results in “2. Solid-liquid separation test (test to peel feces from litter) 2” above, when adding digestive juice, fecal adhesion rate equivalent to that of adding water can be achieved. It can be seen that, as a whole, the methane fermentation process exhibits significant effects from the viewpoints of reducing the amount of water used, increasing the amount of gas generated, and reducing the labor of spraying liquid manure.

  In addition, it was confirmed that the same results were obtained even when the rice bran (rice straw) used as the bedding material in the above tests was replaced with wheat straw and pasture.

4). Effect of fragment size on methane fermentation efficiency (Reference Example 3)
The effect of the size of bedding on the methane fermentation efficiency was investigated. Here, from the viewpoint of improving the accuracy of verification, the bedding is accurately fragmented using scissors or the like. According to the present invention, feces can be suitably peeled from the litter, and the separation efficiency of the litter can be improved, thereby improving the crushing efficiency when producing a litter fragment having a size such as the following litter fragments 1 to 4, for example. Can do. In particular, the below-mentioned bedding pieces 1 to 3 correspond to bedding pieces that can be suitably manufactured by a rotary crusher in which crushing efficiency is suitably improved by the present invention.

(1) Manufacture of litter fragments (crushing treatment)
Here, wheat straw was used as a bedding material.
<Bedding fragment 1; 100 mm fragment>
A piece of wheat straw cut into 100 mm length with scissors was defined as a litter fragment 1 (FIG. 6).

<Bedding fragment 2; 50 mm fragment>
A piece of wheat straw cut into 50 mm length with scissors was used as a bedding piece 2 (FIG. 6).

<Bedding fragment 3; fragment of more than 1 mm to 20 mm>
After the wheat straw was cut with scissors, it was further crushed with a household mixer, passed through a sieve having a diameter of 1 mm, and the piece on the sieve was used as a bedding piece 3 (FIG. 6).

<Bedding fragment 4; fragment of 1 mm or less>
In the production of the bedding piece 3, the piece under the sieve was used as the bedding piece 4 (FIG. 6).

(2) Methane fermentation

<Test 1>
10 g of litter fragment 1 (100 mm fragment) was mixed with 1.2 L of digestive juice (derived from cow dung), and methane fermentation was carried out under the conditions of 55 ° C., no pH control and manual stirring. FIG. 7 shows changes with time in the amount of biogas produced by methane fermentation.

<Test 2>
In Test 1, methane fermentation was performed in the same manner as in Test 1 except that the bedding piece 1 was replaced with the bedding piece 2 (50 mm piece). FIG. 7 shows changes with time in the amount of biogas produced by methane fermentation.

<Test 3>
In Test 1, methane fermentation was performed in the same manner as in Test 1 except that the bedding piece 1 was replaced with the bedding piece 3 (over 1 mm to 20 mm piece). FIG. 7 shows changes with time in the amount of biogas produced by methane fermentation.

<Test 4>
Methane fermentation was performed in the same manner as in Test 1 except that the bedding piece 1 was replaced with the bedding piece 4 (fragment of 1 mm or less) in Test 1. FIG. 7 shows changes with time in the amount of biogas produced by methane fermentation.

<Test 5>
In Test 1, methane fermentation was carried out in the same manner as in Test 1 except that the litter fragment 1 was not used and only the digestive juice was used. FIG. 7 shows changes with time in the amount of biogas produced by methane fermentation.

<Evaluation>
As shown in FIG. 7, when fermenting a piece of litter with a size of 10 mm to 50 mm, the start of biogas generation may be delayed somewhat immediately after the start of the fermentation process, but when fermentation is continued, It has been found that a sufficient amount of biogas can be recovered. When fermenting a piece of litter with a size of 100 mm, it is inferior to the case of a piece of litter with a size of 10 mm to 50 mm, but after 15 days, the amount of biogas generated in test 4 (1 mm or less) I found that I was approaching.

  Moreover, it was confirmed that the post-fermented bedding substantially retains the shape before the fermentation and is suitably used as a bedding.

  In addition, it was confirmed that the same results were obtained even when the wheat straw (wheat straw) used as the bedding material in the above tests was replaced with rice straw and pasture.

1: Digestive liquid addition process 2: First litter separation process 3: Crushing process 4: Mixing process 5: Methane fermentation process 6: Second litter separation process

Claims (8)

A first litter separating step of separating the litter from organic waste containing litter and feces;
A crushing step of crushing the litter separated in the first litter separation step;
A methane fermentation process in which the organic waste after the litter is separated in the first litter separation process and the litter crushed in the crushing process are introduced into a methane fermentation tank to perform methane fermentation;
A second litter separating step for separating the litter from the digestive juice produced in the methane fermentation step,
The methane fermentation method, wherein the digested liquid after the bedding is separated in the second litter separation step is added to the organic waste to be used in the first litter separation step.   2. The methane fermentation method according to claim 1, wherein the digested liquid after the bedding is separated in the second bedding separating step has a TS of 3% or more.   The methane fermentation method according to claim 1 or 2, wherein in the crushing step, a rotary crusher is used as a crushing means.   The method for methane fermentation according to any one of claims 1 to 3, wherein the litter separated in the second litter separating step is reused as a litter. First litter separating means for separating the litter from organic waste containing litter and feces;
Crushing means for crushing the litter separated by the first litter separating means;
A methane fermentation tank for introducing methane fermentation by introducing the organic waste after the litter is separated by the first litter separating means and the litter crushed by the crushing means;
And a second bedding separating means for separating the bedding from the digestive juice produced by the methane fermentation in the methane fermentation tank,
The methane fermentation system, wherein the digested liquid after the bedding is separated by the second bedding separating means is added to the organic waste provided to the first bedding separating means.   6. The methane fermentation system according to claim 5, wherein the digested liquid after the bedding is separated by the second bedding separating means has a TS of 3% or more.   The methane fermentation system according to claim 5 or 6, wherein the crushing means is a rotary crusher.   The methane fermentation system according to any one of claims 5 to 7, wherein the bedding separated by the second bedding separating means is reused as a bedding.