Biomass extract and method for producing biomass extract

Abstract

To provide a biomass extract and a method for producing a biomass extract that can effectively utilize a biomass raw material.SOLUTION: A biomass extract is a water-soluble biomass extract extracted from a biomass raw material containing lignin or hemicellulose, and contains more carbon than the carbon content of saccharides contained in the biomass raw material. A method for producing a biomass extract comprises heating and pulverizing a biomass raw material to prepare a biomass pulverized product, and extracting a biomass extract from the biomass pulverized product with water.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a biomass extract and a method for producing a biomass extract. [Background technology]

[0002] In recent years, technology to produce biomass fuel from non-food biomass (cellulosic biomass) such as wood, grass, and rice straw has been attracting attention as an alternative to food biomass such as sugarcane and corn.

[0003] Patent Document 1 describes a method for producing biomass fuel in which a biomass raw material containing cellulose is pulverized under heating at a temperature of 100° C. or higher but lower than 300° C., and water-soluble components are extracted with water. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-111034 Summary of the Invention [Problem to be solved by the invention]

[0005] Cellulosic biomass raw materials contain hemicellulose and lignin in addition to cellulose. Patent Document 1 describes a method for solubilizing cellulose, but does not describe a method for solubilizing hemicellulose or lignin. In particular, lignin has a different structure from cellulose, making it difficult to apply the above-mentioned solubilization method. Furthermore, lignin that is not extracted with water is discarded as residue, preventing the most effective use of biomass raw materials.

[0006] Therefore, there is a demand for a biomass extract in which lignin and hemicellulose are solubilized and extracted in water, and a method for producing the biomass extract. [Means for solving the problem]

[0007] The biomass extract of the present invention is a water-soluble biomass extract extracted from a biomass raw material containing lignin or hemicellulose, and contains carbon derived from the lignin and has a carbon content that is 10% or more of the carbon content of sugars contained in the biomass raw material.

[0008] Biomass feedstocks contain sugars such as cellulose. It is known that when such biomass feedstocks are heated and pulverized, polymers such as cellulose are decomposed into smaller molecules, becoming water-soluble. The present inventors conducted extensive research into water-soluble biomass extracts and discovered that biomass extracts, which are the result of water-solubilizing sugars, contain water-soluble lignin (lignin-like substances), a component other than sugars. This led to the present invention. Specifically, the biomass extract of the present invention contains carbon derived from lignin and has a carbon content that is 10% or more of the carbon content of the sugars contained in the biomass feedstock. This allows water-soluble biomass extracts to be obtained by converting water-insoluble lignin into lignin-like substances, thereby enabling the conversion of lignin-derived carbon into other substances without using organic solvents or the like. Therefore, the pulverized biomass product and biomass extract of the present invention are highly useful from the perspective of green chemistry and can broaden the applications of lignin, thereby enabling the effective use of biomass feedstocks. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a process block diagram of a solubilization treatment of biomass raw materials. [Figure 2] FIG. 1 is a diagram showing the solubilization rate and the presence or absence of lignin-like substances according to the examples. [Figure 3] FIG. 1 is a diagram showing the solubilization rate of each component according to an example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the biomass extract and the method for producing the biomass extract according to the present invention will be described with reference to the drawings. Note that the embodiments described below are merely examples for explaining the present invention, and the present invention is not limited to these embodiments. Therefore, the present invention can be implemented in various forms without departing from the gist of the present invention.

[0011] It is known that when biomass raw materials are heated and pulverized, polymers such as cellulose are broken down into smaller molecules and become water-soluble. This allows for the production of a water-soluble biomass extract. The inventors focused on the ratio of the carbon content of the biomass extract to the carbon content of the sugars contained in the biomass raw material (amount of water-soluble organic carbon / amount of carbon contained in the sugars contained in the raw material; hereinafter referred to as the solubilization rate) and found that some biomass extracts produced under specified conditions have a solubilization rate of more than 100%. Further research on such biomass extracts revealed that biomass extracts with a solubilization rate of more than 100% contain carbon derived from lignin, leading to the present invention.

[0012] That is, the biomass extract according to the present invention is water-soluble and can be obtained by extraction from a biomass raw material containing lignin or hemicellulose. The biomass extract also contains carbon derived from lignin, with a carbon content of 10% or more of the carbon content of the sugars contained in the biomass raw material. This means that the solubilization rate is 10% or more, and the water-insoluble lignin has been solubilized in water (hereinafter, the water-solubilized lignin may be referred to as a lignin-like substance). This allows the water-insoluble lignin to be converted into a lignin-like substance and obtained as a water-soluble biomass extract, making it possible to convert the lignin-derived carbon into other substances without using organic solvents or the like.

[0013] Such a biomass extract can be produced by solubilizing a biomass raw material. The solubilization method for a biomass raw material will be explained with reference to FIG.

[0014] Examples of biomass raw materials in the present invention include grass or plant biomass such as rice straw, wheat straw, and bagasse; thinning materials such as bamboo and bamboo grass; wood processing waste such as sawdust, chips, and scraps; woody biomass such as roadside tree pruning materials, wooden construction waste, bark, and driftwood; and cellulose products such as waste paper. Sludge, livestock manure, agricultural waste, and urban waste can also be used as long as they contain lignin or hemicellulose to an extent that they can be used as biomass raw materials. These biomass raw materials may be used alone or in combination with multiple different types, and may contain, for example, polysaccharides such as starch, hemicellulose, and pectin in addition to lignin and oligosaccharides.

[0015] Before being heated and pulverized in the heating and pulverization step 1, the biomass raw material may be coarsely pulverized to particles of approximately 1 mm to 100 mm in a coarse pulverization step. Coarse pulverization allows the biomass raw material to be formed into a shape that is easy to handle. In the coarse pulverization step, a pulverization method can be selected depending on the form of the biomass raw material, and for example, a general-purpose pulverizer such as a hammer mill, cutter mill, vibration mill, ball mill, rod mill, roller mill, colloid mill, disk mill, or jet mill can be used. Furthermore, the pulverization treatment in the coarse pulverization step can be either a dry or wet method, but dry pulverization is preferable in terms of reducing the crystallinity of cellulose.

[0016] Furthermore, the biomass raw material may be dried in a drying step before being heated and pulverized in the heating and pulverization step 1. Whether or not to perform the drying step may be determined by measuring the moisture content of the biomass raw material and determining the moisture content. The moisture content of the biomass raw material in the heating and pulverization step 1 is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 10% by mass or less. Therefore, the biomass raw material may be dried in the drying step so that the moisture content of the biomass raw material in the heating and pulverization step 1 reaches the above-mentioned value. The drying step may be performed by natural drying, or by heating the biomass raw material using hot air drying or an electric heater. Note that the coarse pulverization step may be performed after the moisture content of the biomass raw material is reduced to the above-mentioned value or less. By performing dry pulverization on biomass raw material with a low moisture content, the crystallinity of cellulose can be efficiently reduced.

[0017] The biomass raw material that has been coarsely pulverized in the coarse pulverization step or whose moisture content has been adjusted in the drying step is heated and pulverized in the heating and pulverization step 1 to produce a pulverized biomass product. In the heating and pulverization step 1, the heating and pulverization process is carried out at a temperature of 60°C or higher but lower than 300°C. There are no particular restrictions on the method for heating the biomass raw material, and the container can be heated using an electric heater, high frequency waves, microwaves, steam, or the like. Pulverization may also be carried out using a ball mill such as a planetary ball mill. When a ball mill is used, the biomass raw material is subjected to a pulverizing force from the balls, which greatly enhances the mechanochemical effect of pulverization.

[0018] In the heating and grinding process 1, the decomposition of the biomass raw material can be accelerated by obtaining a mechanochemical effect through heating and grinding. That is, after the biomass raw material is decomposed into components such as cellulose, hemicellulose, and lignin, the frictional heat generated by the ball mill is thought to activate the molecular motion of cellulose and other components, accelerating the reduction of crystallinity and the breakdown of molecules into smaller molecules.

[0019] The rotation speed of the ball mill in the heating and grinding step 1 is preferably in the range of 200 rpm to 2000 rpm. The higher the rotation speed, the more rapidly carbonization progresses, but a rotation speed of more than 300 rpm and less than 1500 rpm is preferred in consideration of the balance between production energy and equipment load. Furthermore, the ball diameter and ball weight can be set to any value, but in order to grind the biomass raw material to 10 mm or less, if the vessel capacity of the ball mill is 2 L, it is recommended that they be 1 mmφ to 30 mmφ and 1 kg to 8 kg.

[0020] The heat-pulverization treatment is preferably carried out for 10 minutes or more. Since the longer the treatment time, the faster the reaction of depolymerization progresses, it is desirable to perform the treatment for a long time, but in order to efficiently obtain water-soluble components, it is preferable to perform the treatment for about 10 minutes to 2 hours. As described above, by obtaining the mechanochemical effect, it is possible to solubilize biomass raw materials containing hemicellulose, lignin, etc. at low temperatures in a short time. Furthermore, since no solvents or catalysts are used in the heat-pulverization step 1, the process is safe and production costs can be reduced.

[0021] The heating and grinding step 1 may be performed while removing moisture generated during the heating and grinding step 1. The removal of moisture may be performed by placing a moisture adsorbent such as a dehumidifier in the ball mill, or by cooling a portion of the ball mill to remove moisture as water droplets. The atmosphere during the heating and grinding step 1 may be atmospheric pressure or an atmosphere selected from the group consisting of oxygen, nitrogen, argon, and rare gases. However, from the viewpoint of removing moisture, it is preferable to connect a vacuum pump to the grinding container and perform the step under negative pressure or vacuum. Specifically, the pressure inside the ball mill may be 0.01 MPa or less, and preferably 1 kPa or less. This allows the water generated during the heating and grinding step 1 to be sucked out of the grinding container by the vacuum pump, thereby removing the moisture.

[0022] When water is generated in the heat-pulverization step 1, water-soluble components of the degraded biomass raw material dissolve in water, producing a solubilized solution. When the solubilized solution thus produced is heated, a water-insoluble precipitate is produced. Here, "insoluble" refers to components that are not extracted as an aqueous solution when the precipitate is washed with water. This precipitate is thought to be produced by the reaction of water with degraded cellulose, lignin, and the like. Therefore, by removing the water generated in the heat-pulverization step 1, the generation of precipitates in the heat-pulverization step 1 can be suppressed, and components derived from hemicellulose, lignin, and the like can also be recovered as a biomass extract. This makes it possible to improve the yield of the biomass extract and recover lignin-like substances as a water-soluble biomass extract.

[0023] Furthermore, by performing the heating and grinding step 1 under negative pressure or vacuum, it is possible to reduce the heating temperature. This is because the saturated vapor pressure of water is low under vacuum, and water evaporates at a low temperature. This allows the heating temperature in the heating and grinding step 1 to be set low, which makes it possible to reduce production costs.

[0024] It is also possible to suppress the generation of water in the heating and grinding step 1 by reducing the moisture content of the biomass raw material to be heated and ground in the heating and grinding step 1. This suppresses the formation of precipitates, and components derived from hemicellulose, lignin, etc. can also be recovered as a water-soluble biomass extract.

[0025] Subsequently, in extraction step 2, a biomass extract, which is a water-soluble component, is extracted from the pulverized biomass product that has been heat-pulverized in heat-pulverization step 1. The pulverized biomass product contains oligosaccharides and lignin-like substances with a degree of polymerization that allows them to be extracted into water, making it highly applicable to medical, cosmetic, and agricultural applications. In extraction step 2, water is added to the pulverized product obtained in heat-pulverization step 1 in an amount of 0.1 to 500 times the volume of the pulverized product, and the mixture is mixed. The mixture is then subjected to solid-liquid separation in a solid-liquid separator to obtain the water-soluble component (extract) and the residue. Examples of solid-liquid separators include devices that use gravity sedimentation, centrifugation, membrane separation, coagulation separation, and flotation separation.

[0026] The biomass extract obtained in extraction step 2 may be subjected to total organic carbon measurement, sugar component analysis, NMR, GC-MS, etc. to identify its components. The solubilization rate may also be determined from the total organic carbon measurement. A solubilization rate of over 100% means that components other than sugars contained in the biomass raw material have been extracted as water-soluble components. Therefore, in this case, it is estimated that in addition to monosaccharides or polysaccharides derived from carbohydrates such as cellulose, lignin, a component other than sugars, is contained in the water-soluble components.

[0027] The biomass extract may be mixed with a solid acid catalyst and stirred to hydrolyze it, producing a saccharified solution containing monosaccharides such as glucose as the main component. The saccharified solution thus obtained can be fermented or distilled to produce ethanol, a biomass fuel. Furthermore, the lignin contained in the biomass extract may be chemically modified and used as a plastic material.

[0028] According to the present invention, a biomass extract derived from lignin or hemicellulose can be obtained from biomass raw materials containing these components at low temperatures in a short time by undergoing the heating and crushing step 1 and the extraction step 2. Furthermore, according to the present invention, the biomass raw materials can be solubilized by a simple method without using a solvent or catalyst, which reduces the production energy required and makes the process safe.

[0029] [Example] Examples of the present invention will be described below, but the present invention is not limited to the descriptions of these examples.

[0030] In the following examples, biomass extracts were evaluated by analyzing the constituent sugars and calculating the solubilization rate. The components of the biomass extract were identified by the constituent sugar analysis. The solubilization rate was determined by measuring the sugar content of the biomass raw material calculated by the constituent sugar analysis and the total organic carbon amount obtained by using a TOC meter (total organic carbon meter) on the solubilized solution as the amount of water-soluble organic carbon.

[0031] Example 1 A biomass extract was prepared using a biomass raw material with a sugar content of 66.8%, other components of 28.6%, and a moisture content of 4.6%. The sugar components included cellulose and hemicellulose, and the other components included lignin. This biomass raw material was subjected to a drying process prior to the heat-milling step 1 to reduce the moisture content to 3%, and then heat-milled using a heater-equipped ball mill (ball 5 mm diameter, 7.5 kg) at 120°C, 700 rpm, and under vacuum. Heat-milling was performed for 30 minutes in the heat-milling step 1, and approximately 65 times the amount of water was added to each of the resulting pulverized materials, mixed, and then subjected to solid-liquid separation in a solid-liquid separator to obtain a biomass extract.

[0032] Example 2 A biomass extract was obtained in the same manner as in Example 1, except that the time for the heating and grinding step 1 was set to 60 minutes.

[0033] Example 3 A biomass extract was obtained in the same manner as in Example 1, except that the drying step was not carried out before the heating and grinding step 1, and the heating and grinding step 1 was carried out for 10 minutes under atmospheric pressure.

[0034] Example 4 A biomass extract was obtained in the same manner as in Example 3, except that the heating and grinding step 1 was carried out for 30 minutes.

[0035] Example 5 A biomass extract was obtained in the same manner as in Example 3, except that the heating and grinding step 1 was carried out for 45 minutes.

[0036] Example 6 A biomass extract was obtained in the same manner as in Example 3, except that the heating and grinding step 1 was carried out for 70 minutes.

[0037] 2 shows the heating and grinding time, the presence or absence of a drying step, the heating and grinding conditions, the solubilization rate, and the presence or absence of lignin-like substances for each of the biomass extracts according to Examples 1 to 6. The presence or absence of lignin-like substances was investigated by analyzing the constituent sugars of each biomass extract. It was found that lignin-like substances were contained in all of the examples.

[0038] Furthermore, a tendency was observed for the solubilization rate to increase with increasing time spent performing the heating and grinding step 1. In particular, in Examples 1 and 2, biomass extracts with high solubilization rates could be obtained in a short time, demonstrating that biomass extracts can be efficiently produced by drying the biomass raw material in the drying step and then performing the heating and grinding treatment while removing moisture.

[0039] For Examples 3 to 6, the component ratios of hexose, pentose, and lignin-like substances relative to the raw material contained in the biomass extract were further measured. Figure 3 shows the measurement results. As shown in Figure 3, when the heating and grinding step 1 was performed under atmospheric pressure without a drying step, the amounts of hexose, pentose, and lignin-like substances contained in the biomass extract tended to increase after heating and grinding for 10 minutes or more. Therefore, it was suggested that when the heating and grinding step 1 was performed under atmospheric pressure without a drying step, a heating and grinding time of 10 minutes or more is preferable.

[0040] In the above-described embodiment, the following configurations are envisioned. (1) A water-soluble biomass extract extracted from a biomass raw material containing lignin or hemicellulose, the biomass extract containing carbon derived from the lignin and having a carbon content that is 10% or more of the carbon content of sugars contained in the biomass raw material.

[0041] Biomass raw materials contain sugars such as cellulose. It is known that when such biomass raw materials are heated and pulverized, polymers such as cellulose are decomposed into smaller molecules, becoming water-soluble. The present inventors conducted extensive research into water-soluble biomass extracts and discovered that biomass extracts, which are the result of water-solubilizing sugars, contain water-soluble lignin (lignin-like substances), a component other than sugars, which led to the present invention. Specifically, the biomass extract of the present invention contains carbon derived from lignin and has a carbon content that is 10% or more of the carbon content of the sugars contained in the biomass raw material. This allows water-soluble biomass extracts to be obtained by converting water-insoluble lignin into lignin-like substances, thereby enabling the conversion of lignin-derived carbon into other substances without using organic solvents or the like. Therefore, the biomass extract of the present invention is highly useful from the perspective of green chemistry and can broaden the uses of lignin, thereby enabling the effective use of biomass raw materials.

[0042] (2) The biomass extract of (1) is preferably extracted from a pulverized biomass product prepared by heating and pulverizing a biomass raw material.

[0043] According to this configuration, by heating and pulverizing the biomass raw material, polymers such as cellulose contained in the biomass raw material are decomposed into smaller molecules, producing a pulverized biomass product containing oligosaccharides and lignin-like substances with a degree of polymerization that allows them to be extracted into water.Then, by extracting a biomass extract from the pulverized biomass product with water, the yield of water-soluble biomass extract can be improved.

[0044] (3) It is preferable that the biomass extract of (1) or (2) further contains carbon derived from hemicellulose.

[0045] According to this configuration, since the biomass extract contains carbon derived from hemicellulose, the carbon derived from hemicellulose can be converted into other substances. In particular, since the carbon derived from hemicellulose can be extracted as a water-soluble biomass extract without using an organic solvent, the uses of hemicellulose can be expanded.

[0046] (4) A method for producing a biomass extract according to any one of (1) to (3), comprising heating and pulverizing a biomass raw material to produce a pulverized biomass product, and extracting the biomass extract from the pulverized biomass product with water.

[0047] According to this configuration, the biomass extract is extracted with water from the pulverized biomass material, which is obtained by heating and pulverizing the biomass raw material. Therefore, no chemicals or solvents are used in the biomass extract production process. This makes the process safe and highly useful from the perspective of green chemistry. Furthermore, because the pulverized biomass material is composed of sugars and lignin with a degree of polymerization that allows them to be extracted with water, each component can be used for medical, cosmetic, agricultural, and other purposes. [Industrial Applicability]

[0048] INDUSTRIAL APPLICABILITY The present invention is applicable to a pulverized biomass product prepared from a biomass raw material containing lignin or hemicellulose, a water-soluble biomass extract extracted from the biomass raw material, and a method for producing a biomass extract. [Explanation of symbols]

[0049] 1: Heating and grinding process, 2: Extraction process

Claims

1. A water-soluble biomass extract extracted from a biomass feedstock containing lignin or hemicellulose, Contains carbon derived from the lignin, A biomass extract having a carbon content that is 10% or more of the carbon content of the sugars contained in the biomass raw material.

2. The biomass extract according to claim 1, which is extracted from a pulverized biomass product prepared by heating and pulverizing the biomass raw material.

3. 10. The biomass extract of claim 1, further comprising carbon derived from said hemicellulose.

4. A method for producing a biomass extract according to any one of claims 1 to 3, A method for producing a biomass extract, comprising heating and pulverizing the biomass raw material to produce a pulverized biomass product, and extracting a biomass extract from the pulverized biomass product with water.

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