JP6640004B2 - Method for producing glucose from used absorbent articles - Google Patents

Description

  The present invention relates to a method for producing glucose from a spent absorbent article comprising pulp fibers and a superabsorbent polymer. In particular, the present invention relates to a method for saccharifying pulp fibers contained in a used absorbent article containing a pulp fiber such as a disposable diaper and a superabsorbent polymer to obtain a saccharified solution containing glucose.

  An absorbent article such as a disposable diaper usually comprises an absorbent containing pulp fibers and a superabsorbent polymer, and an outer envelope such as a nonwoven fabric or a plastic film surrounding the absorbent. These absorbent articles are discarded and incinerated after use. However, in recent years, from the viewpoint of environmental consideration, it has been studied to collect and recycle the materials constituting the absorbent articles. For example, there is an attempt to saccharify pulp fibers contained in a used absorbent article with an enzyme to obtain a saccharified solution containing glucose. However, although the absorbent article contains the superabsorbent polymer together with the pulp fiber, it is not easy to separate and remove the superabsorbent polymer, and there has been a problem in using the used absorbent article as a saccharification raw material.

  In order to solve this problem, for example, Patent Document 1 discloses a method of saccharifying cellulose-containing waste containing a superabsorbent polymer such as a disposable diaper, from a saccharified solution to a superabsorbent polymer and other foreign substances (plastic film, nonwoven fabric). A method is disclosed in which calcium chloride is added to a saccharified solution to salt out the superabsorbent polymer to remove the superabsorbent polymer in order to facilitate removal of the superabsorbent polymer.

JP 2013-202021 A

In the method disclosed in Patent Document 1, since calcium chloride is added after the saccharification step to salt out the superabsorbent polymer, the superabsorbent polymer absorbs water in the saccharification step to expand the volume. There is a problem that the saccharification efficiency is reduced because the volume of the saccharification tank capable of saccharification reaction decreases.
It is also conceivable to add calcium chloride to salt out the superabsorbent polymer before the saccharification step. However, in this case, there is a problem that salts reduce the activity of the enzyme.
An object of the present invention is to increase the saccharification efficiency of pulp fibers contained in a used absorbent article without inhibiting saccharification.

The present invention is a method of producing glucose from a spent absorbent article comprising pulp fibers and a superabsorbent polymer, the method comprising:
Removing a mixture of pulp fiber, superabsorbent polymer and water from the used absorbent article,
A step of applying a voltage to the mixture of pulp fiber, superabsorbent polymer and water using a pair of electrodes to inactivate the superabsorbent polymer, and a mixture of pulp fiber and the inactivated superabsorbent polymer and water In the presence of an enzyme, and saccharifying the pulp fiber with the enzyme to obtain a saccharified solution containing glucose.

The present invention includes the following aspects.
[1] A method for producing glucose from a spent absorbent article containing pulp fibers and a superabsorbent polymer, the method comprising:
Removing a mixture of pulp fiber, superabsorbent polymer and water from the used absorbent article,
A step of applying a voltage to the mixture of pulp fiber, superabsorbent polymer and water using a pair of electrodes to inactivate the superabsorbent polymer, and a mixture of pulp fiber and the inactivated superabsorbent polymer and water In the presence of an enzyme to saccharify the pulp fiber with the enzyme to obtain a saccharified solution containing glucose.
[2] The method according to [1], further comprising a step of applying water to the used absorbent article before the step of taking out the mixture of pulp fiber, superabsorbent polymer and water from the used absorbent article.
[3] The method according to [1] or [2], further comprising a step of collecting a drainage containing urine-derived components discharged from the superabsorbent polymer in the step of inactivating the superabsorbent polymer.
[4] The method further includes a step of filtering or dehydrating a residue obtained after taking out the mixture of pulp fiber, superabsorbent polymer and water from the used absorbent article, and collecting a waste liquid containing urine-derived components [1]. -The method according to any one of [3].
[5] After the step of inactivating the superabsorbent polymer and before the step of obtaining the saccharified solution, the method further includes a step of adjusting the water content of a mixture of pulp fiber, the inactivated superabsorbent polymer and water [1] ] The method according to any one of [4] to [4].
[6] After the step of inactivating the superabsorbent polymer and before the step of obtaining the saccharified solution, the method further includes a step of adjusting the pH of a mixture of pulp fiber, the inactivated superabsorbent polymer and water [1]. -The method according to any one of [5].
[7] The method according to any one of [3] to [6], further comprising a nutrient recovery step of recovering urine-derived nutrients from wastewater containing urine-derived components.
[8] Any of [3] to [7], further including a microbial fuel cell step of charging wastewater containing urine-derived components to the microbial fuel cell to reduce the TOC concentration in the wastewater and recovering power generated by power generation. The method described in Crab.
[9] The method according to any one of [1] to [8], further comprising a sterilizing step of sterilizing a mixture of pulp fiber, the inactivated superabsorbent polymer, and water before the step of obtaining the saccharified solution.
[10] The method according to [9], wherein the viable cell count of the mixture after the sterilization step is 1 × 10 ³ or less.
[11] The method according to any one of [1] to [10], wherein the superabsorbent polymer is a superabsorbent polymer derived from acrylic acid.
[12] The method according to any one of [2] to [11], wherein the step of applying water to the used absorbent article is a step of immersing the used absorbent article in warm water of 50 ° C or more and less than 100 ° C. Method.
[13] In the step of applying water to the used absorbent article, the weight of the used absorbent article after applying water is 90% or more of the maximum absorption weight of the used absorbent article. The method according to any one of [12].
[14] The step of taking out the mixture of pulp fiber, superabsorbent polymer and water from the used absorbent article includes passing the used absorbent article between a pair of rollers to remove the pulp from the envelope of the used absorbent article. The method according to any one of [1] to [13], which is a step of squeezing a mixture of fiber, superabsorbent polymer and water.
[15] A method for producing ethanol or lactic acid by fermenting glucose obtained by the method according to any one of [1] to [14].
[16] The method according to any one of [1] to [14], further comprising a step of separating the saccharified solution containing glucose and the inactivated superabsorbent polymer.
[17] The method further comprises the step of solidifying the residue or inactivated superabsorbent polymer after removing the mixture of pulp fiber, superabsorbent polymer and water from the spent absorbent article [1] to [14]. And the method according to any one of [16].

  According to the present invention, prior to the saccharification step, a voltage is applied to a mixture of pulp fiber, superabsorbent polymer and water using a pair of electrodes to inactivate the superabsorbent polymer. There is no decrease in the saccharification efficiency due to a decrease in the volume capable of saccharification reaction in the saccharification tank due to volume expansion due to absorption of water. In addition, since the superabsorbent polymer is inactivated by voltage application, salts and water held by the superabsorbent polymer are desalted and dehydrated and discharged. There is no reduction in the volume that allows the saccharification reaction due to the expanded superabsorbent polymer. Furthermore, since additives such as calcium chloride are not added to inactivate the superabsorbent polymer, there is no decrease in enzyme activity due to salt.

FIG. 1 is a schematic diagram of an example of an apparatus for performing the method of the present invention. FIG. 2 is a diagram for explaining a method of measuring the maximum absorption weight. FIG. 3 shows an example of the configuration of the microbial fuel cell.

  The present invention is a method for producing glucose from a spent absorbent article comprising pulp fibers and a superabsorbent polymer.

  The absorbent article is not particularly limited as long as it contains pulp fibers and a superabsorbent polymer, and examples thereof include disposable diapers, incontinence pads, urine absorbing pads, sanitary napkins, panty liners, and the like. Above all, incontinence pads and disposable diapers that are collectively collected at a facility or the like are preferable because they have a relatively large amount of pulp without labor for separation.

  Although it does not specifically limit as a pulp fiber, A fluff-like pulp fiber, a chemical pulp fiber, etc. can be illustrated.

Superabsorbent polymer, also called SAP (Superabsorbent Polymer), has a three-dimensional network structure in which a water-soluble polymer is appropriately cross-linked, and absorbs water from several tens to several hundred times. Water is insoluble in water, and once absorbed water does not separate even if some pressure is applied, for example, acrylic acid-based, starch-based, amino acid-based particulate or fibrous polymers may be exemplified. it can. In the present invention, an acrylic acid-based superabsorbent polymer is preferred because polyacrylic acid is converted into polyacrylic acid by inactivation, and the effect of lowering the pH in the saccharification step can be expected. The superabsorbent polymers of acrylic acid, having a sodium substituted carboxyl group -COONa, upon absorption of water -COONa is -COO ^- and ionized into the Na ^+, dissociating the Na ⁺ ions, superabsorbent The dissociated ion concentration in the polymer increases, and the water outside the superabsorbent polymer enters the superabsorbent polymer due to the osmotic pressure difference between the inside and outside of the superabsorbent polymer, and as a result, the superabsorbent polymer swells and a large amount of Will retain water.

  The method of the present invention includes a step of removing a mixture of pulp fibers, a superabsorbent polymer, and water from a used absorbent article (hereinafter, also simply referred to as a “removing step”). The method of removing the mixture of pulp fiber, superabsorbent polymer and water from the used absorbent article is not limited, but the used absorbent article is passed between a pair of rollers (by a roller press) to remove the used absorbent article. A method of squeezing a mixture of pulp fiber, superabsorbent polymer and water from the outer package of the article (nonwoven fabric, film, rubber, etc.) is preferred. In that case, before passing the used absorbent article between the pair of rollers, the used absorbent article is used to facilitate squeezing the mixture of pulp fiber, superabsorbent polymer and water from the envelope. May be cut into strips or passed between a pair of rolls for the purpose of crushing or perforating the outer package.

In the method of the present invention, a step of applying a voltage to a mixture of pulp fiber, superabsorbent polymer and water using a pair of electrodes to inactivate the superabsorbent polymer (hereinafter, also referred to simply as “voltage applying step”) ). When the superabsorbent polymer has a sodium-substituted carboxyl group (—COO ⁻ Na ⁺ ), in this step, Na ⁺ ions in the superabsorbent polymer are negatively electrophoretically generated by an electric field formed by voltage application. As it moves toward the electrode, Na ⁺ ions are released from the superabsorbent polymer, and the concentration of dissociated ions in the superabsorbent polymer decreases, so that the water in the superabsorbent polymer goes out due to the osmotic pressure difference. The superabsorbent polymer dehydrates and shrinks. -COO in superabsorbent polymers ^- but to form to -COOH bonded with H ⁺ ions generated by ionization of the water, the structure will not be able to extend the network internal crosslinking is too strong by hydrogen bonding, superabsorbent The reactive polymer is inactivated.

  The method of applying the voltage is not limited. For example, if a mixture of pulp fiber, superabsorbent polymer and water is sandwiched between two horizontally arranged wire meshes, and a voltage is applied between the two wire meshes, Good. The applied voltage is not limited as long as the superabsorbent polymer can be inactivated.

The drainage discharged from the superabsorbent polymer by the application of the voltage passes through the wire mesh and falls under the wire mesh by gravity. The drainage that has fallen under the wire mesh is collected in a drainage collection container arranged below the wire mesh. The effluent contains Na ⁺ ions released from the superabsorbent polymer, OH ⁻ ions generated by ionization of water, salts derived from urine, organic matters derived from excretion, and the like.

  The voltage application step may be performed by a batch type (batch type) or a flow type. When the method is carried out in a flow-through manner, for example, it can be carried out in an apparatus as shown in FIG.

In the method of the present invention, a mixture of pulp fiber, inactivated superabsorbent polymer, and water is coexisted with an enzyme, and the pulp fiber is saccharified with the enzyme to obtain a saccharified solution containing glucose (hereinafter, simply referred to as “saccharification”). Step ”). According to the method of the present invention, the superabsorbent polymer coexists in the saccharification step, but does not inhibit the saccharification reaction because the superabsorbent polymer has already been inactivated. In addition, since Na ⁺ ions desorbed from the superabsorbent polymer and OH ⁻ ions generated by ionization of water are removed together with the wastewater, the pulp fiber in the saccharification process, the inactivated superabsorbent polymer, and water are removed. Is not made alkaline, and the acidity at which the enzyme works can be maintained.

  An enzyme containing at least cellulase is used. The cellulase is not particularly limited. For example, it is preferable to use a cellulase having a high hydrolytic ability, which is produced by a microorganism such as Trichoderma, Aspergillus or Acremonium. Among them, cellulase derived from the genus Acremonium has been found to have a very high hydrolytic ability even in the presence of lignin, and thus it is particularly preferable to use this. Cellulases include endoglucanases that randomly cut cellulose chains, exoglucanases that release cellobiose from the ends of cellulose chains (cellobiohydrolases), and β-glucosidases that degrade cellobiose into glucose. These cellulases having different decomposition modes may be used in combination.

  The amount of cellulase used in the saccharification is not particularly limited, and can be appropriately set according to the capacity of the saccharification tank, the amount of the object to be treated, the activity of the cellulase to be used, and the like. More specifically, the amount of cellulase used is preferably 0.1 to 30% by weight based on the amount of pulp fibers. If the amount of cellulase added is too small relative to the amount of pulp fiber, the enzyme treatment takes a long time and there is a problem in performance. On the other hand, if the amount is too large, the saccharification rate does not increase so much even if the amount of the enzyme used increases, which is disadvantageous from the viewpoint of cost.

The solid content concentration in the mixture of pulp fiber, inactivated superabsorbent polymer and water in the saccharification step is not limited as long as the saccharification reaction proceeds, but is preferably 1 to 50% by weight, more preferably 5 to 20% by weight. % By weight.
The content of the pulp fiber in the mixture of the pulp fiber, the inactivated superabsorbent polymer, and water in the saccharification step may be appropriately set according to the activity of the cellulase to be used, and is not particularly limited. It is 5 to 25% by weight, more preferably 2.5 to 10% by weight.

  The temperature and pH in the saccharification step may be appropriately set according to the type of cellulase to be used and the like, but need to be set within a range where the cellulase functions sufficiently and does not inactivate. For example, the temperature is preferably set within the range of 10 to 70 ° C, and the pH is preferably set to 3.0 to 8.0. The processing time is preferably about 5 to 72 hours.

  The method of the present invention comprises a step of applying water to a used absorbent article (hereinafter simply referred to as a "water applying step") before a step of taking out a mixture of pulp fiber, superabsorbent polymer and water from the used absorbent article. ) May be further included. By applying water to the used absorbent article and sufficiently swelling the superabsorbent polymer, it becomes easy to take out the pulp fiber and the superabsorbent polymer from the used absorbent article, and the pulp is used in the voltage application step. The contact resistance between the fiber, superabsorbent polymer and water mixture and the electrode can be reduced, and the presence of water makes it easier for electricity to flow through the mixture of pulp fiber, superabsorbent polymer and water This increases the efficiency of the voltage application process. In absorbent articles such as disposable diapers, an absorber composed of pulp fibers and a superabsorbent polymer is usually sandwiched between upper and lower coating layers (outer envelope). Cheap. Further, by providing water, it becomes easy to take out the pulp fiber and the superabsorbent polymer from the used absorbent article. As a result, the amount of the pulp fiber to be recovered is not reduced so much that the pulp fiber can be recovered efficiently.

  The amount of water to be applied is not limited as long as the superabsorbent polymer can be inactivated in the voltage application step, but the weight of the used absorbent article after applying water is 90% of the maximum absorption weight of the used absorbent article. % Is preferable. When the used absorbent article is swelled to 90% or more of the maximum absorption weight of the used absorbent article, the used absorbent article swells into a bread pan, so that the absorbent composed of pulp fiber and superabsorbent polymer can be easily extruded and can be taken out efficiently.

Here, the maximum absorption weight corresponds to the weight after immersing the absorbent article in tap water in the following procedure.
[Method of measuring maximum absorption weight]
(1) As shown in FIG. 2A, cuts 65 are made in elastic materials 63, 64 capable of forming pockets and flattened so that the absorbent article 61 does not reach the absorber 62.
(2) Immerse in a water bath filled with sufficient tap water, with the absorbing surface facing down, and leave it for 30 minutes.
(3) After standing, the absorbent surface 67 is placed down on the net 66, and the weight after draining for 20 minutes is defined as the maximum absorbed weight (see FIG. 2 (b)).

The method of applying water is not limited, but a method of immersing the used absorbent article in water is preferable. According to the method of dipping in water, the superabsorbent polymer can be swollen and washed at the same time. When the used absorbent article contains impurities such as stool, the impurities such as stool can also be removed.
The temperature of the water is not limited, but is preferably 55 ° C. or more and less than 100 ° C., more preferably 60 ° C. or more and less than 100 ° C., and further preferably 70 ° C. or more and less than 100 ° C. By using warm water of 55 ° C. or higher, the water absorption efficiency of the superabsorbent polymer is increased, some bacteria are firstly sterilized, and the hot melt adhesive used in the absorbent article is softened. In addition, since the absorbent is easily extruded, pulp fiber recovery efficiency is increased.
The immersion time is not limited as long as inactivation of the superabsorbent polymer can be performed in the voltage application step, but is preferably 1 minute or more, more preferably 5 minutes or more, and further preferably 10 minutes or more.

The method of the present invention further comprises a step of collecting a drainage containing urine-derived components discharged from the superabsorbent polymer in the step of inactivating the superabsorbent polymer (hereinafter, also referred to simply as “drainage collecting step”). .). The effluent contains Na ⁺ ions released from the superabsorbent polymer, OH ⁻ ions generated by ionization of water, salts derived from urine, organic matters derived from excretion, and the like. This step can be performed simultaneously with the inactivation step. The collected effluent can be sent to a nutrient recovery step and / or a microbial fuel cell step, which will be described later, to be used effectively. By collecting and reusing non-pulp fibers, the recycling rate of used absorbent articles is increased.

  The method of the present invention further comprises a step of filtering or dehydrating a residue after removing the mixture of pulp fiber, superabsorbent polymer and water from the used absorbent article, and collecting a drainage containing urine-derived components ( Hereinafter, it may be simply referred to as “filtration or dehydration step”). The effluent includes salts derived from urine, organic matters derived from excrement, and the like. The collected effluent can be sent to a nutrient recovery step and / or a microbial fuel cell step, which will be described later, to be used effectively. By collecting and reusing non-pulp fibers, the recycling rate of used absorbent articles is increased.

  The method of the present invention further comprises, after the step of inactivating the superabsorbent polymer, and before the step of obtaining a saccharified solution, a step of adjusting the water content of the mixture of pulp fiber and the inactivated superabsorbent polymer and water. (Hereinafter, it may be simply referred to as “moisture content adjusting step”). The purpose of this step is to adjust the water content such that the saccharification reaction proceeds efficiently in the saccharification step. Here, the water content (% by weight) is equal to a value obtained by subtracting the solid content concentration (% by weight) from 100% by weight.

  The method of the present invention further comprises a step of adjusting the pH of a mixture of pulp fiber, the inactivated superabsorbent polymer and water after the step of inactivating the superabsorbent polymer and before the step of obtaining a saccharified solution ( Hereinafter, it may be simply referred to as “pH adjustment step”). The purpose of this step is to adjust the pH so that the saccharification reaction proceeds efficiently in the saccharification step. If a mixture of pulp fiber, inactivated superabsorbent polymer and water is left in contact with the atmosphere, it absorbs carbon dioxide in the atmosphere and changes its pH, so pulp fiber and the inactivated superabsorbent polymer and water It is preferable to adjust the pH of the mixture immediately before starting the saccharification reaction.

The method of the present invention may further include a nutrient recovery step of recovering urine-derived nutrients from wastewater containing urine-derived components. Nutrients refer to salts containing nitrogen, phosphorus, or potassium that can be used as fertilizers, and more specifically, ammonium salts, phosphates, and the like. The collected nutrients can be used as fertilizer.
The method of recovering nutrients is not limited, but a method of recovering nutrients containing phosphorus by crystallizing phosphorus in wastewater as hydroxyapatite (hereinafter also referred to as “HAP method”), A method of recovering nutrients containing phosphorus and / or nitrogen by crystallizing phosphorus and / or nitrogen in the wastewater as magnesium ammonium phosphate (hereinafter, also referred to as “MAP method”) can be exemplified. .

The HAP method is a method that utilizes the crystallization phenomenon of hydroxyapatite (Ca ₁₀ (OH) ₂ (PO ₄ ) ₆ ) generated by the reaction between PO ₄ ^3- and Ca ²⁺ and OH ⁻ in the wastewater. The reaction formula is as follows.
_{^{10Ca 2+ + 2OH - + 6PO 4}} 3- → Ca 10 (OH) 2 (PO 4) 6 (1)
In the HAP method, Ca ²⁺ and OH ⁻ are added to an aqueous solution containing phosphorus and contacted with a seed crystal in a supersaturated state (metastable range), whereby hydroxyapatite is crystallized on the surface of the seed crystal and phosphorus Is to be collected. Phosphorite ore, bone charcoal, calcium silicate hydrate, or the like can be used as the seed crystal.
In this method, the Ca ²⁺ concentration needs to be 5 mmol / L or more, the pH needs to be 8 or more, more preferably the Ca ²⁺ concentration needs to be 10 mmol / L or more, and the pH needs to be 9 or more.

MAP method, PO ₄ ^3- and NH ₄ ⁺ in the effluent, is a method of utilizing crystallization phenomenon of magnesium ammonium phosphate _{(MgNH 4 PO 4 · 6H 2} O) produced by the reaction of Mg ^2+. The reaction formula is as follows.
^{_{Mg 2+ + NH 4 + + PO}} 4 3- + 6H 2 O → MgNH 4 PO 4 · 6H 2 O (2)
In this method, the Mg ²⁺ concentration is preferably 30 to 60 mmol / L, and the pH is preferably 6.8 to 7.7.

The method of the present invention may further include a microbial fuel cell step of charging the microbial fuel cell with the effluent containing urine-derived components to reduce the TOC concentration in the effluent and recovering power generated by power generation.
Here, the microbial fuel cell is a device that converts organic substances as fuel into electric energy using microorganisms. In a microbial fuel cell, a negative electrode and a positive electrode are immersed in a solution of an organic substance that is a fuel, and electrons generated when the organic substance is oxidized and decomposed by microorganisms are collected at the negative electrode, and the electrons move to the positive electrode via an external circuit. In the positive electrode, electrons are consumed by a reduction reaction of the oxidant. Electrons flow due to the difference between the oxidation-reduction potential of the chemical reaction occurring at the negative electrode and the chemical reaction occurring at the positive electrode, and energy corresponding to the product of the potential difference between the two electrodes and the current flowing through the external circuit is obtained in the external circuit.
In the microbial fuel cell process, the effluent is charged into the microbial fuel cell to reduce the TOC concentration in the wastewater and collect power generated by power generation. In the microbial fuel cell, the microorganisms oxidize and decompose organic matter such as waste and fine pulp contained in the effluent, so that the TOC concentration in the wastewater is reduced and power is generated.

  The microorganism used in the microbial fuel cell is not particularly limited as long as it can contribute to oxidative decomposition of organic matter and generation of electric energy, but hydrogen-producing microorganisms are mainly used, and among them, obligate anaerobic bacteria are used. A facultative anaerobic bacterium is preferably used.

  FIG. 3 shows an example of the configuration of the microbial fuel cell. In the figure, 101 is a drainage tank, 102 is a pump, 103 is a negative electrode reaction tank, 104 is a negative electrode, 105 is a proton exchange membrane, 106 is a positive electrode tank, 107 is a positive electrode, 108 is a tester, 109 is a personal computer, and 110 is sludge sedimentation. A tank, 111 is a pump, and 112 is a purified water tank.

Preferably, the pH of the wastewater from the microbial fuel cell step is less than 8.0. If the pH of the wastewater from the microbial fuel cell process is too high, the power generation efficiency of the microbial fuel cell process will decrease.
The TOC concentration of the wastewater from the microbial fuel cell process is preferably 2000 mg / L or less. If the TOC concentration of the wastewater from the microbial fuel cell step is 2000 mg / L or less, the purification treatment can be easily performed in a general purification tank or the like in the next step. When the wastewater is directly discharged from the microbial fuel cell step, the TOC concentration of the wastewater is preferably 30 mg / L or less.

The method of the present invention may further include, before the step of obtaining the saccharified solution, a sterilization step of sterilizing a mixture of pulp fiber, the inactivated superabsorbent polymer, and water. After the sterilization step, the number of viable bacteria in the treatment liquid supplied to the saccharification step is preferably 1 × 10 ³ or less.
However, according to the method of the present invention, in the voltage application step, the cell membrane of the bacterium is destroyed by the application of the voltage, and the bacterium is killed. Therefore, the voltage application step has a bactericidal function and also functions as a bactericidal step. When the viable cell count before the voltage application step is 1 × 10 ⁹ , the viable cell count of the mixture of pulp fiber, inactivated superabsorbent polymer and water after the voltage application step may be reduced to 1 × 10 ³ or less. it can. Therefore, it is not always necessary to provide a sterilization step separately from the voltage application step.
Sterilization also contributes to improving the efficiency of fermentation in the fermentation process.

The method of the present invention may further include a step of separating the inactivated superabsorbent polymer from the saccharified solution containing glucose (hereinafter, also simply referred to as “separation step”). By this step, the inactivated superabsorbent polymer and other solid contaminants are separated and removed from the saccharified liquid, whereby a saccharified liquid free of the superabsorbent polymer and other solid contaminants can be obtained. The method for separating the saccharified solution and the inactivated superabsorbent polymer is not limited, and examples thereof include filtration, sedimentation, and centrifugation. Above all, filtration is preferred. Since the superabsorbent polymer is inactivated, filtration can be easily performed.
The saccharified solution containing glucose obtained in the separation step may be used as it is in the fermentation step described below, or glucose may be isolated from the saccharified solution containing glucose.

  The method of the present invention further comprises the step of solidifying the residue or inactivated superabsorbent polymer after removing the mixture of pulp fiber, superabsorbent polymer and water from the spent absorbent article (hereinafter simply referred to as " Solid fueling step ”). The residue after removing the mixture of pulp fiber, superabsorbent polymer and water from the used absorbent article includes nonwoven fabric, plastic film, rubber and the like. The plastic material recovered from the spent absorbent article can be recycled by converting it into a solid fuel. By collecting and reusing non-pulp fibers, the recycling rate of used absorbent articles is increased. The conversion to solid fuel can be performed by a so-called RPF method.

The method of the present invention further comprises the steps of: after the voltage application step, before the saccharification step, Na ⁺ ions released from the superabsorbent polymer, OH ⁻ ions generated by ionization of water, salts derived from urine, excretion-derived substances. The method may include a dehydration step of dehydrating a waste liquid containing an organic substance or the like. The enzyme activity in the saccharification process is prevented from lowering, and the recycling rate in the nutrient recovery process and the microbial fuel cell process is increased.

The glucose obtained by the method of the present invention may be fermented to produce ethanol or lactic acid. To produce ethanol or lactic acid, a saccharification step is followed by a fermentation step.
In order to produce ethanol, glucose obtained by the method of the present invention may be fermented with yeast. More specifically, yeast may be added to the saccharified solution containing glucose obtained by the method of the present invention and fermented, or after separating glucose from the saccharified solution containing glucose obtained by the method of the present invention. Alternatively, the separated glucose may be fermented by yeast. Yeast may be added to the saccharified solution containing the inactivated superabsorbent polymer and fermented. The yeast used for ethanol fermentation is not particularly limited, and any of natural yeast and genetically modified yeast can be used. Typical examples include yeasts of the genus Saccharomyces. The amount of yeast used during ethanol fermentation is not particularly limited, and can be appropriately set according to the capacity of the fermenter, the amount of sugar solution, the activity of the yeast used, and the like. The temperature and pH in the ethanol fermentation step are not particularly limited, and can be appropriately set according to the amount of sugar to be subjected to ethanol fermentation and the type of yeast.
Further, by using a lactic acid-producing bacterium or the like instead of yeast, a chemical product such as lactic acid can be obtained.

  Saccharification and fermentation may be performed simultaneously in one step. That is, in the saccharification / fermentation step, cellulase and yeast are added to a mixture of pulp fiber, superabsorbent polymer, and water, and pulp fiber is saccharified by cellulase to produce glucose. To produce ethanol. According to this method, ethanol can be produced from a mixture of pulp fiber, superabsorbent polymer and water in the same treatment tank. Ethanol production using the enzymatic saccharification method, for example, a saccharification treatment by adding a cellulase solution prepared by dissolving a cellulase powder in a solvent such as a buffer to a pre-reaction solution containing pulp fibers, and then saccharifying, and then adding yeast And ethanol fermentation.

Hereinafter, the present invention will be further described with reference to the drawings, but the present invention is not limited to the embodiments shown in the drawings.
FIG. 1 is a schematic diagram of an example of an apparatus 1 for implementing the present invention.
The apparatus 1 includes a take-out step 2, a voltage application step 3, and a saccharification step 4.

  The take-out step 2 includes a conveyor 21, a cutter 22, and a pair of rollers 23. The used absorbent article 11 is placed on a conveyor 21 and transported, and cut by a cutter 22 into, for example, a strip having a predetermined width. The cut used absorbent article is sent to a pair of rollers 23. Therefore, the outer envelope 12 constituting the used absorbent article passes between the pair of rollers 23, and a mixture of pulp fiber, the superabsorbent polymer, and water is squeezed out of the outer envelope by the pair of rollers 23. Accumulate in front of the roller 23. The mixture 13 of the pulp fiber, the superabsorbent polymer, and the water accumulated before the pair of rollers 23 is periodically scraped out and sent to the voltage application step 3.

The voltage applying step 3 has a first electrode 31 and a second electrode 32. The second electrode 32 is provided above the first electrode 31. The first electrode 31 is a belt conveyor made of a wire mesh. The second electrode 32 also has a belt shape and may be made of a conductive material, and need not be a wire mesh, but may be a wire mesh. A predetermined voltage is applied between the first electrode 31 and the second electrode 32 (not shown). Either the first electrode 31 or the second electrode 32 may be a positive electrode. The lower half of the belt forming the second electrode 32 moves at the same speed (from left to right in the drawing) as the upper half of the belt conveyor forming the first electrode 31. The gap between the first electrode 31 and the second electrode 32 is made adjustable, and is preferably adjusted so that the gap becomes smaller as moving from left to right. The mixture 13 of pulp fiber, superabsorbent polymer and water removed from the used absorbent article in the removal step is placed on the first electrode 31 and transported, and the first electrode 31 and the second electrode 32, and a voltage is applied. The wastewater 14 containing Na ⁺ ions, OH ⁻ ions, salts derived from urine, organic matter derived from excrement, and the like is discharged from the superabsorbent polymer to which the voltage is applied. The discharged drainage 14 passes through a wire mesh forming the first electrode 31, drops into a drainage recovery container 33 installed below the first electrode 31, and is stored. From the outlet of the voltage application step 3, the mixture 15 of the pulp fiber, the inactivated superabsorbent polymer and water is discharged, and sent to the saccharification step 4.

  The saccharification step 4 has a saccharification tank 41. The saccharification tank 41 is charged with the mixture 15 of the pulp fiber, the inactivated superabsorbent polymer and water sent from the voltage application step 3. When a predetermined amount of the mixture 15 has been charged, the saccharification tank 41 is replaced. Thereafter, the mixture 15 sent from the voltage applying step 3 is charged into the replaced saccharification tank. Water is added to the saccharification tank 41 into which a predetermined amount of the mixture 15 has been added to adjust the solid content concentration, a pH adjuster or the like is added to adjust the pH, and further, the cellulase powder is added to a solvent such as a buffer solution. A saccharification treatment is performed by adding a cellulase solution prepared by dissolution. When the pulp fiber is sufficiently saccharified, the saccharified solution is filtered to remove the inactivated superabsorbent polymer and other solid contaminants from the saccharified solution.

  The method of the present invention can be suitably used for recycling used absorbent articles such as disposable diapers.

DESCRIPTION OF SYMBOLS 1 Apparatus 2 Take-out process 3 Voltage application process 4 Saccharification process 11 Spent absorbent article 12 Outer package 13 Mixture of pulp fiber, superabsorbent polymer, and water 14 Drainage 15 Pulp fiber, inactivated superabsorbent polymer, and water Mixture 21 Conveyor 22 Cutter 23 A pair of rollers 31 First electrode 32 Second electrode 33 Drainage collection container 41 Saccharification tank 101 Drainage tank 102 Pump 103 Negative reaction tank 104 Negative electrode 105 Proton exchange membrane 106 Positive electrode tank 107 Positive electrode 108 Tester 109 Personal computer 110 Sludge settling tank 111 Pump 112 Purification water tank

Claims (15)

A method of producing glucose from a spent absorbent article comprising pulp fibers and a superabsorbent polymer, the method comprising:
A step of applying water for swelling the superabsorbent polymer to the used absorbent article,
By passing the used absorbent article between a pair of rollers and squeezing a mixture of pulp fiber, superabsorbent polymer and water from the outer envelope of the used absorbent article, Removing the mixture of superabsorbent polymer and water,
A step of applying a voltage to the mixture of pulp fiber, superabsorbent polymer and water using a pair of electrodes to inactivate the superabsorbent polymer, and a mixture of pulp fiber and the inactivated superabsorbent polymer and water In the presence of an enzyme to saccharify the pulp fiber with the enzyme to obtain a saccharified solution containing glucose. The method further includes a step of filtering or dehydrating a residue after removing the mixture of pulp fiber, superabsorbent polymer, and water from the used absorbent article, and collecting a drainage containing urine-derived components,
The method according to claim 1, wherein the wastewater containing urine-derived components discharged from the superabsorbent polymer in the step of inactivating the superabsorbent polymer is collected.   The method according to claim 2, further comprising a nutrient recovery step of recovering urine-derived nutrients from wastewater containing urine-derived components. A method of producing glucose from a spent absorbent article comprising pulp fibers and a superabsorbent polymer, the method comprising:
Removing a mixture of pulp fiber, superabsorbent polymer and water from the used absorbent article,
A step of applying a voltage to the mixture of pulp fiber, superabsorbent polymer and water using a pair of electrodes to inactivate the superabsorbent polymer,
In the step of causing the mixture of pulp fiber and the inactivated superabsorbent polymer and water to coexist with the enzyme, saccharifying the pulp fiber with the enzyme to obtain a saccharified solution containing glucose, and in the step of inactivating the superabsorbent polymer A liquid containing urine-derived components discharged from the superabsorbent polymer, or a residue obtained after removing a mixture of pulp fiber, superabsorbent polymer, and water from the used absorbent article is collected by filtration or dehydration. A method comprising a microbial fuel cell step in which a waste liquid containing urine-derived components is injected into a microbial fuel cell to reduce the TOC concentration in the wastewater and recover power generated by power generation. The method according to any one of claims 1 to 4 , wherein the step of applying water to the used absorbent article is a step of immersing the used absorbent article in warm water of 50C or more and less than 100C. In the step of applying water to the used absorbent article is the weight of the used absorbent article after application of the water is more than 90% of the maximum absorption weight of the used absorbent article, any of claims 1 to 5 Or the method of claim 1 . After the step of inactivating the superabsorbent polymer, before the step of obtaining the sugar solution, claim further comprising the step of adjusting the water content of the mixture of superabsorbent polymer and water which pulp fibers and inactivated 1-6 The method according to any one of claims 1 to 4. After the step of inactivating the superabsorbent polymer, before the step of obtaining the sugar solution, according to claim 1 to 7, further comprising the step of adjusting the pH of the mixture of superabsorbent polymer and water which pulp fibers and inactivated A method according to any one of the preceding claims. The method according to any one of claims 1 to 8 , further comprising, before the step of obtaining the saccharified solution, a sterilizing step of sterilizing a mixture of pulp fiber, the inactivated superabsorbent polymer, and water. The method according to claim 9 , wherein the viable cell count of the mixture after the sterilization step is 1 × 10 ³ or less. The method according to any one of claims 1 to 10 , wherein the superabsorbent polymer is a superabsorbent polymer derived from acrylic acid. A method for producing ethanol or lactic acid by fermenting glucose obtained by the method according to any one of claims 1 to 11 . The method according to any one of claims 1 to 11 , further comprising a step of separating the saccharified solution containing glucose from the inactivated superabsorbent polymer. Claim 1 to 11 and 13 residues or superabsorbent polymer inactivated after the used absorbent article was taken out of a mixture of pulp fibers and super absorbent polymer and water further comprising the step of solid fuel of Item 2. The method according to item 1. After the voltage application step and before the saccharification step, the effluent containing Na ⁺ ions released from the superabsorbent polymer, OH ⁻ ions generated by ionization of water, salts derived from urine, or organic matters derived from excreta is removed. the method according to any one of claims 1 to 11 13 and 14, further comprising a dehydration step of dehydrating.

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