JP2003260450A - Method for recycling garbage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for disposing garbage without being accompanied with environmental disruption. <P>SOLUTION: In a method for recycling the garbage through polylactic acid, the method for recycling the garbage comprises a process (1) for storing the garbage in a polylactic acid bag, a process (2) for recovering the garbage stored in the polylactic acid bag in the process (1), a process (3) in which after the garbage recovered in the process (2) and the polylactic acid bag are made under a sterilized condition, they are offered to lactic acid fermentation to obtain lactic acid, wherein the sterilized condition is created by obtaining a mixture of the garbage stored in the polylactic acid bag and an alkaline solution and amount of alkali incorporated in the alkaline solution is enough to make the garbage to the sterilized condition and is at most equimolar to amount of lactic acid produced, a process (4) in which the polylactic acid bag is manufactured from lactic acid obtained in the process (3), and a process (5) for storing the garbage in the polylactic acid bag manufactured in the process (4) to returning the process (1). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for recycling raw garbage. More specifically, the present invention stores raw garbage in a polylactic acid bag, collects the raw garbage, and subject the collected raw garbage to lactic acid fermentation to obtain lactic acid. Using this lactic acid, a polylactic acid bag is produced. The present invention relates to a method for recycling raw garbage by storing the raw garbage in this polylactic acid bag.

[0002]

2. Description of the Related Art In recent years, the environmental destruction caused by dust has become a serious problem, including the generation of dioxin due to the incineration of dust. With respect to raw garbage discarded from businesses such as homes and restaurants, attempts have been made to recycle it by composting it or lactic acid fermentation using it as a raw material. The method of treating garbage by the lactic acid fermentation method is
Since the product lactic acid can be used as a raw material for biodegradable plastics, it is considered to be one of the effective methods for recycling raw garbage.

However, the raw garbage discarded from homes and businesses is usually collected in a non-biodegradable bag made of polyethylene or the like. In order to recycle such garbage by lactic acid fermentation, a complicated pretreatment step for separating the garbage and the polyethylene bag etc. is required in advance, which causes an increase in the cost of recycling the garbage. ing. Furthermore, the separated polyethylene bags have to be discarded by incineration, landfilling, etc., and the problem of environmental destruction has not been completely solved.

Non-Patent Document 1 describes that lactic acid fermentation is performed using raw garbage dried in a polylactic acid bag as a raw material. This non-patent document 1 describes that natural lactic acid fermentation is carried out by adding water to raw garbage dried in a polylactic acid bag and performing an intermittent pH control method. According to this intermittent pH control method, it is described that standard lactic acid fermentation can be carried out by covering the raw garbage even if it is dried. Also,
In this non-patent document 1, Lactobacillus rhamunos
It is also described that the us is inoculated and the fermentation pH is controlled on the acidic side (pH 6).

However, the intermittent pH control method described in Non-Patent Document 1 above is a method for carrying out lactic acid fermentation using natural lactic acid fermentation, that is, lactic acid-fermenting bacteria originally contained in garbage. Therefore, in this intermittent pH control method, sterilization is not performed before lactic acid fermentation. Further, in this non-patent document 1, it is completely impossible to recycle raw garbage by producing a polylactic acid bag using the produced lactic acid and using the polylactic acid bag for storing raw garbage. Not disclosed.

Further, Patent Document 1 discloses a method for producing lactic acid from an organic waste as a raw material for the purpose of producing lactic acid at a low cost with high selectivity and concentration from an organic waste such as garbage. Have been described. Specifically, this patent document 1
In addition, the fermentation step of fermenting the raw material mainly composed of organic waste to make it weakly acidic, and the alkaline agent adding step of adding an alkaline agent to the weakly acidic raw material to raise the pH are repeated. , A method for producing lactic acid is described.

The method described in Patent Document 1 is characterized by utilizing natural lactic acid bacteria and not performing sterilization treatment such as steam sterilization as in Non-Patent Document 1 (No. 1). 0011 paragraph). Further, in this Patent Document 1, it is completely disclosed that the produced lactic acid is used to manufacture a polylactic acid bag, and the polylactic acid bag is used to store the garbage, whereby the garbage can be recycled. It has not been.

Further, Non-Patent Document 2 describes a method of performing lactic acid fermentation by controlling the temperature of raw garbage at 37 ° C. and pH at 7, and adding L lactic acid bacteria. In this non-patent document 2, a case where steam sterilization is performed and a case where steam sterilization is not performed are compared, and it is described that a lactic acid fermentation liquid having a higher concentration was obtained when steam sterilization was not performed than when steam sterilization was performed. . In addition, it is completely disclosed in Patent Document 2 that the produced lactic acid is used to manufacture a polylactic acid bag and the polylactic acid bag is used to store the garbage, whereby the garbage can be recycled. It has not been.

[0009]

[Non-Patent Document 1] Yoshito Shirai, another person, lactic acid fermentation using raw garbage dried in a polylactic acid bag as a raw material, Proceedings of the Autumn Meeting of the Chemical Society of Japan, Japan, August 26, 1999,
Volume 32, 137

[Patent Document 1] Japanese Patent Laid-Open No. 11-285397

[Patent Document 2] Yoshito Shirai and 2 others, L-lactic acid fermentation of raw garbage, Proceedings of the Annual Meeting of the Chemical Engineering Society, Japan, 1999
64 times a year, 200 pages

[0010]

The present invention has been made to solve the above problems, and specifically provides a method for disposing of garbage without causing environmental damage. With the goal.

[0011]

The present inventors have found that the above problems can be solved by the following method for recycling garbage, and have completed the present invention. That is, the present invention is
The following methods are provided.

(I) In the method of recycling raw garbage via polylactic acid, (1) a step of storing the raw garbage in the polylactic acid bag, and (2) collecting the raw garbage stored in the polylactic acid bag in the step 1 And (3) a step of sterilizing the garbage collected in step 2 and the polylactic acid bag and then subjecting it to lactic acid fermentation to obtain lactic acid, the sterilized state being stored in the polylactic acid bag. It is created by obtaining a mixture of raw garbage and an alkaline solution, and the amount of alkali contained in the alkaline solution is sufficient to sterilize the garbage and the amount of lactic acid produced. To the polylactic acid bag produced from the lactic acid obtained in the step 3, and (5) storing raw garbage in the polylactic acid bag produced in the step 4. By having and A method for recycling raw garbage, comprising returning to the step 1.

(II) The method for recycling raw garbage according to (I), wherein the sterilization state is a number of bacteria or less that does not adversely affect lactic acid fermentation in step 3.

(III) The alkaline solution is ammonia, a hydroxide of an alkali metal or an alkaline earth metal,
And an aqueous solution of an alkaline compound selected from the group consisting of an alkali metal or alkaline earth metal salt of carbonic acid, (I) or (II) as a method for recycling garbage.

(IV) The method for recycling raw garbage according to any one of (I) to (III), wherein the lactic acid fermentation in the step 3 is performed by a continuous method or a semi-batch method.

(V) The lactic acid fermentation in the step 3 is carried out by a batch method (I) to (III).
The method for recycling raw garbage according to any one of 1.

(VI) The raw garbage contained in the polylactic acid bag of step 2 is in a dry state (I)
A method for recycling raw garbage according to any one of (1) to (V).

(VII) The method of recycling raw garbage according to any one of (I) to (V), wherein the raw garbage contained in the polylactic acid bag in the step 2 is in a wet state. .

BEST MODE FOR CARRYING OUT THE INVENTION The method for recycling garbage according to the present invention will be described in detail below. The raw garbage used in the method of the present invention usually means garbage containing food discarded from homes, restaurants and the like. The food includes not-yet-processed food such as heated food and so-called leftover rice after processed food.
In addition, as long as there is no obstacle such as blockage in the device, or unless it shows toxicity to the added microorganisms,
What is contained in what is normally discarded as "burning garbage" such as paper, plastic, and wood chips may be mixed.

[0019] Usually, the raw material constituting the garbage used in the method of the present invention includes vegetables, fruits, marine products such as meat and fish, rice, bread, tea grounds, etc., but is not limited to these. Absent. For example, a suitable combination of shochu distilled spirits, beer wort meal, okara, molasses, waste starch powder, production-adjusted agricultural products, fishery waste such as fish roe, etc. may be used.

FIG. 1 shows a block diagram of each step of the method for recycling garbage according to the present invention.

In step 1 of the method for recycling raw garbage of the present invention, the raw garbage is stored in a polylactic acid bag. The polylactic acid bag is proposed to be used for transporting raw garbage through a research on the needs of consumers, which is a large-scale project of the Science and Technology Agency in which the present inventor is involved. A commercially available product can be used as the polylactic acid bag.

The raw garbage contained in the polylactic acid bag varies depending on the ambient temperature, humidity, etc., but if left in an atmosphere of about 50 ° C., the raw garbage is usually put out of the polylactic acid bag within 1 week to 10 days. Moisture is released and becomes dry. Here, the dry state means a water content of 30% or less. In the method of the present invention, such dried raw garbage can be recycled or wet wet garbage can be recycled. Here, the wet state means a state in which the water content is higher than that in the dry state.

In the present invention, what should contain raw garbage is defined as a polylactic acid bag, but it is made of polylactic acid, and the raw garbage can be stored in a sealed state. The shape, thickness, etc. are not particularly limited as long as the water can be eluted to the outside.

Next, in step 2 of the method for recycling garbage according to the present invention, the garbage contained in the polylactic acid bag in step 1 is collected. There is no particular limitation on the method of collection, and for example, the collection method conventionally performed in the municipalities can be used. It is preferable that what is collected in step 2 does not contain any substance other than the polylactic acid bag and the garbage.

Next, in step 3 of the method for recycling garbage according to the present invention, the garbage collected in step 2 is subjected to lactic acid fermentation to obtain lactic acid.

Step 3 of the present invention includes the first aspect. The step 3 has a second aspect as a reference aspect. 2 and 3 are block diagrams of respective steps of the first aspect and the second aspect, respectively.

As shown in FIG. 2, the first step 3 of the present invention is performed.
In the lactic acid fermentation, (A) obtaining a mixture of the garbage and the alkaline solution contained in the polylactic acid bag collected in step 2 of the method for recycling garbage of the present invention, and (B) The method includes a step of subjecting the mixture obtained in the step A to lactic acid fermentation using a microorganism to obtain lactic acid, and (C) a step of providing the lactic acid in the step B as a raw material for a polylactic acid bag in step 4 described later.

As shown in FIG. 3, in the second embodiment of the step 3, in the lactic acid fermentation, (a) the raw lactic acid stored in the polylactic acid bag collected in the step 2 of the method for recycling raw garbage of the present invention. A step of separating the waste from the polylactic acid bag, (b) a step of sterilizing the raw garbage separated in the step a, and (c) a step of sterilizing the raw garbage sterilized in the step b by lactic acid fermentation by microorganisms to obtain lactic acid And (d) mixing the polylactic acid bag separated in step a with the alkaline solution to obtain lactic acid, and (e) combining the lactic acid obtained in steps c and d, and The step of providing the raw material for the polylactic acid bag in step 4 described later is included. This second aspect will be described later.

The first aspect of lactic acid fermentation carried out in step 3 of the present invention will be described below. In step A of the first aspect, raw garbage and an alkaline solution are mixed.

There is no particular limitation on the amount of raw garbage to be used, and it can be mixed.
It can be set appropriately according to the capacity of the reaction tank used for
However, in order to efficiently carry out the first aspect, dry
It is preferable that the dry weight has a garbage concentration of about 10%.
Yes. An example is 10 liters (hereinafter referred to as "L").
Write down. ) 1 to dry weight for a reaction vessel of about
It is possible to use about 100 kg (5 kg when wet) of raw garbage
it can. The capacity of the reaction tank is the amount of raw garbage used as raw materials.
The method of the present invention can be appropriately set according to the
When carrying out with garbage collected from homes, etc.,
For example, 500m ³It can be applied to a reaction tank of a moderate size.
You can If the reaction tank has a large capacity, it will be connected to the reaction tank.
Since the diameter of the conduit that is
To reduce the possibility of conduit blockage due to unobtainable substances
You can

The alkaline solution to be mixed with the raw garbage is one which can be mixed with the raw garbage to make the mixture have an alkaline property, preferably a pH value of 9.5 or more, and the lactic acid in the next step B. There is no particular limitation as long as it does not adversely affect the fermentation. As an example, an aqueous solution of ammonia, an alkali metal or alkaline earth metal hydroxide (for example, sodium hydroxide, potassium hydroxide), and an alkali metal or alkaline earth metal salt of carbonic acid (for example, calcium carbonate) is used. Can be used.

As the amount of the alkaline solution, an amount corresponding to an equimolar amount or less of an alkaline substance with respect to lactic acid produced by lactic acid fermentation in step B described in detail below can be used.

The amount of lactic acid produced by lactic acid fermentation varies depending on the type of raw garbage used, the type of microorganism used, and the like.
Therefore, the amount of the alkaline solution used, before applying the method of the present invention, previously subjected a small amount of garbage sample to lactic acid fermentation,
It is desirable to measure the amount of lactic acid produced and roughly estimate from that value.

If the amount of the alkaline solution used is too small,
It is not preferable because bacteria having weak tolerance to alkalinity cannot be sterilized sufficiently, and as a result, in the next step B, the remaining bacteria which are not sterilized can propagate.

It is preferable to stir the garbage and the alkaline solution in order to sufficiently mix them. The stirring time is not particularly limited as long as the garbage and the alkaline solution are sufficiently mixed. When the method of the present invention is carried out using garbage collected from households, etc., the residence time is usually 2 days to 10 days.
It can be set to about a day.

The raw garbage and the alkaline solution can be mixed at room temperature (10 to 30 ° C.), but from the viewpoint of decomposition of the polylactic acid bag or efficient sterilization, 50 to 80 ° C.
It is preferable to carry out at a temperature in the range.

In the mixture obtained in the step A of the first aspect, the sugar concentration can be usually set in the range of 50 g / L to 100 g / L.

In the method of recycling raw garbage of the present invention, the raw garbage to be recycled is usually Bacillus.
It is known that general bacteria such as genus, Pseudomonas and Closeridiam are included. In the method of the present invention,
Bacteria contained in raw garbage are sterilized by the alkali used in the step A of this embodiment 1, and preferably, a mixture of the sterilized raw garbage and an alkaline solution is subjected to the next step B. Here, "being in a sterilized state" means that the number of bacteria in the mixture obtained in step A is a number that does not adversely affect lactic acid fermentation in step B. In particular,
The bacterial concentration in the reaction tank in step B is preferably 50,000 CFU / milliliter (hereinafter referred to as “mL”) or less. Normally, 10 million CFU /
Since bacteria of about mL are contained, if the number of bacteria contained in the mixture obtained in the step A is 1/100 or less, it means that the mixture is sufficiently sterilized. The number of bacterial colonies can be measured by the method described in the Biotechnology Experiment Manual, edited by Japan Society of Biotechnology.

The use of the alkaline solution of step A of the first aspect described above is intended for sterilization. Sterilization is
It is also possible to use steam that is conventionally used. However, the sterilization method using steam requires energy and time, and an expensive apparatus having a pressure resistant structure is required, which may increase the cost required for recycling garbage. Therefore, it is preferable to use an alkaline solution in consideration of cost and the like.

In the step B of the first aspect, the above step A
Lactic acid fermentation using microorganisms is carried out in the presence of the mixture obtained in (1). The lactic acid fermentation using a microorganism may be any of a continuous method, a semi-batch method and a batch method.

Here, the continuous method means a substance to be subjected to fermentation,
Specifically, it refers to a method in which the mixture obtained in the above step A is continuously supplied to a fermenter and the fermentation liquid is recovered from the fermenter at a flow rate equal to the supply flow rate. However, continuous supply does not mean that supply is not interrupted even for a moment, and includes intermittent supply after a certain period of time. In this case, the recovery flow rate of the fermentation liquor is made equal to the supply flow rate.

The semi-batch method is a substance used for fermentation,
Specifically, the supply of the mixture obtained in the above step A to the fermenter is continuous, but the fermentation liquid is not recovered but left in the fermenter. The continuous supply in the semi-batch method does not mean that the supply is not interrupted even for a moment, as in the case of the continuous method, and includes intermittent supply at fixed intervals.

The batch method means a method in which, once the mixture obtained in the above step A has been supplied to the fermenter, the fermented liquid is not recovered but remains in the fermenter.

The microorganism used for lactic acid fermentation is not particularly limited, and is not particularly limited as long as it can act on garbage to produce lactic acid. Examples of microorganisms include lactic acid bacteria, Lactob
acillus, Streptococcus, Pediococcus, Leucomo
The genus stoc can be mentioned. Among these, homolactic acid bacteria that produce only lactic acid can be preferably used as the lactic acid bacteria from the viewpoint of industrial production. As these lactic acid bacteria, those described in catalogs such as ATCC and IFO can be used.

The conditions for lactic acid fermentation by the continuous method include the type of microorganism used, its optimum pH, optimum temperature, sugar consumption rate, lactic acid production rate, the amount of the mixture obtained in step A, the size of the fermentation tank used, etc. It can be appropriately set according to

The residence time in step B can be set within the range of 2 to 10 days, preferably 2.5 to 7 days. This residence time also takes into consideration the frequency of collecting raw garbage used in the method of the present invention from homes and the like.

The microorganism concentration in the fermenter is 10 ⁹ to 10 ^10.
It can be set in the range of CFU / mL.

The capacity of the fermenter can be appropriately set according to the amount of raw garbage used as a raw material, etc. When the method of the present invention is carried out using raw garbage collected from households, for example, It can be applied to a fermenter having a size of about 500 m ³ .

The pH in the fermentor will change as the fermentation progresses.
It may change depending on the amount of the alkaline substance used in the step A and the amount of lactic acid produced. Therefore, the pH can be adjusted to the optimum pH by adding a substance capable of adjusting the pH such as an acidic substance such as sulfuric acid, if necessary. However, such a step becomes an additional step, and causes an increase in cost for carrying out the method of the present invention. Therefore, process A
It is preferable to set the amount of the alkaline substance used in step 1 so as to be equal to or less than the equimolar amount of lactic acid produced.

The pH value of the fermenter is set in the range of 4 to 9, preferably 4.5 to 6.0, and the temperature is set in the range of 20 to 80 ° C, preferably 30 to 70 ° C. can do. The fermentation time is not particularly limited, and it can be continuously performed as long as the microorganism can perform lactic acid fermentation. The atmosphere in the fermentor can be anaerobic or aerobic, depending on the microorganism used. The microorganism may be in a free state in the fermenter or may be supported on a carrier such as urethane foam.

On the other hand, the conditions for lactic acid fermentation by the semi-batch method are as follows:
The fermentation conditions can be set in the same manner as in the continuous method except that the fermented liquid is not recovered from the fermenter.

The lactic acid fermentation in step 3 of the method for recycling raw garbage of the present invention can be carried out using an apparatus usually used for lactic acid fermentation. An example of an apparatus for carrying out the continuous fermentation method will be described below with reference to FIG. 4, but the present invention is not limited to this.

FIG. 4 is a schematic diagram of a continuous fermentation apparatus that can be used in the first embodiment of step 3 of the present invention. The continuous fermentation apparatus of FIG. 4 has a fermentation section I and an alkaline solution supply section I containing garbage.
I, and the fermentation liquor recovery unit III. Although the apparatus of FIG. 4 does not include a temperature control device, the fermentation section I can be provided with a temperature control means as needed.

In the apparatus shown in FIG. 4, in the fermentation section I,
There is a fermenter 1. The microorganism 5 is suspended in the fermentation liquid 7. The fermenter 1 comprises an air pressure adjusting means 9 and stirring means 11a, 1
1b, fermentation liquid level control means 13a, 13b. The level control means 13a, 13b are interlocked with a pump 21 described later to maintain the liquid level of the fermented liquor 7 in the fermenter 1 at a predetermined position so that the fermented liquor in the fermenter is kept constant To do. The garbage-containing alkaline solution supply section II is filled with the mixture of the garbage and the alkaline solution prepared in the step A of the present invention. The garbage-containing alkaline solution 17 is introduced from the container 15 to the fermenter 1 by a line 19 using a pump 21. An outlet 31 is provided in the vicinity of the bottom surface of the fermenter 1, and the fermented liquor 7 is collected in a collector 39 of a collecting section III using a pump 35 through a line 33.

Next, a second mode, which is a reference mode of step 3 of the method for recycling raw garbage of the present invention, will be described. As shown in FIG. 3, in the lactic acid fermentation of the second aspect,
(A) a step of separating the raw garbage contained in the polylactic acid bag collected in step 2 of the method for recycling raw garbage of the present invention from a polylactic acid bag, and (b) the raw garbage separated in the step a And (c) subjecting the raw garbage sterilized in step b to lactic acid fermentation by microorganisms to obtain lactic acid,
(D) The step of mixing the polylactic acid bag separated in the step a with an alkaline solution to obtain lactic acid, and (e) the lactic acid obtained in the steps c and d are combined, and the lactic acid bag of the present invention described later is used. The step of supplying the raw material of the polylactic acid bag in step 4 of the method for recycling raw garbage is included.

In the step a of the second aspect, the method for separating the garbage and the polylactic acid bag is not particularly limited as long as the separation can be completed completely. For example, the polylactic acid bag can be crushed by crushing. .

In step b of mode 2, the separated garbage is sterilized. The sterilization method is not particularly limited as long as the number of bacteria is equal to or less than the number that does not adversely affect lactic acid fermentation in step b. For example, the sterilization method may be performed using the alkaline solution of the first aspect described above or by steam. You can also The conditions for sterilizing with steam include, for example, 120
It can be carried out at 2 ° C and 2 ° C.

The method of performing sterilization by steam and the apparatus used therefor can be performed by the method and apparatus conventionally used.

In step c of the second embodiment, the sterilized raw garbage is subjected to lactic acid fermentation by microorganisms to obtain lactic acid. This lactic acid fermentation can be performed by the continuous method or the semi-batch method of the first aspect described above, or by the batch method. When the batch method is used, the pH value of the fermented liquid at the end of lactic acid fermentation is 3.5.
It is preferable to set it in the range of from 5.0 to 5.0 from the viewpoint of preservation.

On the other hand, the polylactic acid bag separated in step a of the second embodiment is dissolved by mixing with an alkaline solution to obtain lactic acid (step d). As the alkaline substance forming the alkaline solution used, the alkaline solution described in the first embodiment can be used.

From the viewpoint of dissolving the polylactic acid bag, it is preferable to set the amount of the alkaline solution so that the pH value of the reaction solution after dissolving the polylactic acid bag is in the range of 9.0 to 14. As an example, for a polylactic acid bag having a weight of about 1 kg, about 4 L of ammonia water having a concentration of 25% by weight can be used.

In the step 2 of the step 2, the lactic acid obtained in the steps c and d is combined, and the polylactic acid bag in the step 4 of the method for recycling the garbage according to the present invention, that is, the step for producing the polylactic acid bag. To be used as a raw material. The method for producing a polylactic acid bag from lactic acid is described, for example, in "Biodegradable Plastic Handbook", edited by Yoshiharu Dohi.

By utilizing the polylactic acid bag obtained in the above step 4 as the polylactic acid bag for storing the raw garbage in the step 1 of the method for recycling raw garbage of the present invention, the recycling of raw garbage can be achieved. Complete.

[0064]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited thereto.

Vegetables 40, fruits 30, meat / fish 14, rice 10, tea grounds 6 as a model of raw garbage discharged from home
Synthetic dust adjusted at a ratio of (all by weight) was used in the following examples.

Example 1 5 g of 500 g of the above-mentioned synthetic dust
The polylactic acid bag (manufactured by Shimadzu Corp.) was stored for 1 day at room temperature (water content 80%), and collected and placed in a tank containing 500 mL of 1% ammonia water. The bag was dissolved as it was, and the garbage and the ammonia water were mixed. 1 in advance
L bioreactor with a similar mixture of food waste and water
00 mL was charged and this was batch fermented. Fermentation temperature is 3
From the 4th day of batch fermentation at 7 ° C, continuous fermentation was started using raw garbage treated in aqueous ammonia. Lactob for lactic acid bacteria
acillus rhamnosus was used. The residence time of raw garbage was 4 days. The execution results are shown in the graphs of FIGS. 5 and 6.

FIG. 5 shows the number of bacteria in a mixture of synthetic waste and aqueous ammonia (37 ° C.) when the synthetic waste alone (without addition of ammonia) and the temperature at the time of mixing the synthetic waste and aqueous ammonia. This is a comparison with the number of bacteria at 70 ° C. In FIG. 5, the vertical axis represents the number of bacteria. The horizontal axis represents the time after adding ammonia water to the synthetic waste.

From the results shown in FIG. 5, it is clear that the addition of ammonia markedly reduces the number of bacteria in the mixture and has a great bactericidal effect. The decrease in the number of bacteria is
It is clear that setting the temperature of the mixture to 70 ° C is greater than setting it to 37 ° C.

FIG. 6 is a graph showing changes in the amount and pH of lactic acid, acetic acid and formic acid in the fermentation broth after starting continuous fermentation. In FIG. 6, the vertical axis (left) represents pH, and the vertical axis (right) represents the concentration of each acid. The horizontal axis represents the time from the start of continuous fermentation.

From the results shown in FIG. 6, it is clear that only lactic acid is stably produced by the lactic acid fermentation carried out in step 3 of the method for recycling garbage according to the present invention.

Reference Example 1 5 g of the above-mentioned synthetic dust of 500 g
It was put in a polylactic acid bag (manufactured by Shimadzu Corporation). 3 at 70 ° C
After the passage of days, the polylactic acid bag having the water content of 30% was crushed, and then the polylactic acid bag was crushed to separate the raw garbage and the crushed polylactic acid bag. 500 g of water was added to the raw garbage, which was placed in a fermenter and subjected to steam sterilization. The fermentation temperature was adjusted to 37 ° C and pH 6. Lactobacillus rhamnosus was used as the lactic acid bacterium. On the other hand, polylactic acid bag has 25% ammonia water 50m
It was put in L and dissolved. The fermentor is p
Although H was lowered, ammonia water in which this polylactic acid bag was dissolved was added to control the pH to 6. Polylactic acid was completely dissolved in 25% ammonia water and coexisted in ammonia water as ammonium lactate, but when these were added for pH adjustment, they coexisted with the produced lactic acid in the fermenter,
After purification and synthesis, it becomes polylactic acid again. After 4 days of fermentation, the ammonia water in which the polylactic acid bag had been dissolved was consumed for pH adjustment, the lactic acid concentration reached 65 g / L, and the expected results were obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the steps of the method of the present invention.

FIG. 2 is a block diagram showing the steps of step 3 (first aspect) of the method of the present invention.

FIG. 3 is a block diagram showing steps of a reference aspect (second aspect) of step 3 of the method of the present invention.

FIG. 4 is a schematic diagram of an example of a continuous fermentation apparatus for carrying out the method of the present invention.

FIG. 5 is a graph showing the sterilization state of raw garbage with an alkaline solution.

FIG. 6 is a graph showing the production amount of lactic acid and the like produced by continuous fermentation.

Claims (7)

[Claims] 1. A method of recycling raw garbage via polylactic acid, comprising: (1) storing the raw garbage in a polylactic acid bag; and (2) collecting the raw garbage stored in the polylactic acid bag in step 1 above. And (3) a step of sterilizing the garbage collected in step 2 and the polylactic acid bag and then subjecting the bag to lactic acid fermentation to obtain lactic acid, wherein the sterilized state is a raw material stored in the polylactic acid bag. It is created by obtaining a mixture of garbage and an alkaline solution, the amount of alkali contained in the alkaline solution is sufficient to sterilize the raw garbage, and the amount of lactic acid produced On the other hand, a step of equimolar or less, (4) a step of producing a polylactic acid bag from the lactic acid obtained in the step 3, and (5) a step of storing raw garbage in the polylactic acid bag produced in the step 4 By having A method for recycling raw garbage, characterized by returning to step 1. 2. The method for recycling raw garbage according to claim 1, wherein the sterilization state is a number of bacteria or less that does not adversely affect lactic acid fermentation in step 3. 3. The alkaline solution is an aqueous solution of an alkaline compound selected from the group consisting of ammonia, alkali metal or alkaline earth metal hydroxides, and carbonic acid alkali metal or alkaline earth metal salts. The method for recycling raw garbage according to claim 1 or 2, which is characterized in that. 4. The method for recycling raw garbage according to any one of claims 1 to 3, wherein the lactic acid fermentation in the step 3 is carried out by a continuous method or a semi-batch method. 5. The method for recycling raw garbage according to any one of claims 1 to 3, wherein the lactic acid fermentation in the step 3 is performed by a batch method. 6. The method of recycling raw garbage according to claim 1, wherein the raw garbage contained in the polylactic acid bag in the step 2 is in a dry state. 7. The method of recycling raw garbage according to claim 1, wherein the raw garbage contained in the polylactic acid bag in the step 2 is in a wet state.