Plant-derived fuel production method

Abstract

The present invention provides a plant-derived fuel production method including: a step for cleaning a plant-derived biomass; and a step for subjecting the cleaned plant-derived biomass to steam explosion, said method not including a step for cleaning the plant-derived biomass that has been subjected to steam explosion.

Description

Plant-derived fuel production method

[0001] The present invention broadly relates to a method for producing plant-derived fuels.

[0002] In recent years, plant-derived fuels have been attracting attention from the perspectives of preventing global warming and achieving carbon neutrality. However, plant-derived fuels, especially plant-derived solid fuels, have a relatively low calorific value and a high ash content, such as alkali metals. The ash contained in the fuel generates clinker on the inner walls of a combustion furnace, thereby reducing the operating rate of the combustion furnace. Patent Documents 1 and 2 disclose methods for producing plant-derived fuels with reduced ash content.

[0003] Specifically, Patent Document 1 discloses a method for producing solid fuel, which includes providing pulverized biomass and washing the pulverized biomass powder with an aqueous washing solution. Patent Document 2 discloses a method for producing solid fuel, which includes washing biomass, steam exploding the washed biomass to obtain exploded biomass, and washing the exploded biomass after steam explosion.

[0004] JP 2023-544871 A JP 2023-95161 A

[0005] The problem to be solved by the present invention is to provide a method for producing a plant-derived fuel having a higher calorific value and a reduced ash content, compared to the methods disclosed in Patent Documents 1 and 2.

[0006] As a result of intensive research to solve the above problems, the inventors have found that steam explosion of washed biomass can produce a fuel with a higher calorific value and can sufficiently reduce the ash content, rather than pulverizing and washing the biomass. Furthermore, they have found that washing the biomass only before the steam explosion process can produce a fuel with a higher calorific value and can sufficiently reduce the ash content, rather than washing the biomass before and after the steam explosion process.

[0007] That is, this application encompasses the following inventions. [1] A method for producing plant-derived fuel, comprising the steps of washing plant-derived biomass and steam exploding the washed plant-derived biomass, but excluding the step of washing the steam-exploded plant-derived biomass. [2] The method according to [1], wherein the plant-derived biomass is biomass derived from one or more plants selected from the group consisting of sorghum, Erianthus, Giant Miscanthus, Napier grass, switchgrass, corn, sugarcane bagasse, kenaf, pearl millet, foxtail millet, millet, finger millet, and bamboo. [3] The method according to [1] or [2], wherein the steam explosion is carried out under a pressure of 2.5 to 3.5 MPa for 10 to 20 minutes. [4] The method according to any one of [1] to [3], wherein the washing is carried out using water. [5] The method according to any one of [1] to [4], wherein the washing reduces inorganic elements in the plant-derived biomass. [6] The method according to any one of [1] to [5], wherein the total mass fraction of sodium and mass fraction of potassium in the washed plant-derived biomass is 1800 ppm or less, and the mass fraction of chlorine is 500 ppm or less. [7] The method according to any one of [1] to [6], further comprising a step of forming the steam-exploded plant-derived biomass into granules.

[0008] According to the present invention, a method for producing a plant-derived fuel having a low ash content and a high calorific value can be provided.

[0009] 1 shows the results of elemental analysis of a washed sorghum sample immediately after harvest. 2 shows the results of elemental analysis of a washed sorghum silage sample. 3 shows the results of analysis of potassium concentration in a washed sorghum sample immediately after harvest and an silage sample. 4 shows the results of analysis of chlorine concentration in a washed sorghum sample immediately after harvest and an silage sample. 5 shows the results of higher heating value and lower heating value of a washed and pressed silage sample and an untreated silage sample.

[0010] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described, but the scope of the present invention should not be interpreted as being limited to the following embodiment.

[0011] The present embodiment provides a method for producing plant-derived fuel, which includes a step of washing plant-derived biomass and a step of steam exploding the washed plant-derived biomass, but does not include a step of washing the steam-exploded plant-derived biomass.

[0012] The type of plant in this embodiment may be any type and may be appropriately determined by a person skilled in the art depending on the purpose, but is preferably a herbaceous plant. Among herbaceous plants, sorghum, Erianthus, Giant Miscanthus, Napier grass, switchgrass, corn, sugarcane bagasse, kenaf, pearl millet, foxtail millet, millet, finger millet, and bamboo are more preferred, and sorghum is even more preferred among them. In this embodiment, the plant-derived biomass and plant-derived fuel are preferably biomass and fuel derived from one or more plants selected from the group consisting of sorghum, Erianthus, Giant Miscanthus, Napier grass, switchgrass, corn, sugarcane bagasse, kenaf, pearl millet, foxtail millet, millet, finger millet, and bamboo, respectively.

[0013] As used herein, "plant-derived biomass" refers to a composition containing any organic matter derived from a plant. In this embodiment, the plant-derived biomass may be the plant itself or a processed plant product. Examples of processed plant products include plants (silage) that have been lactic acid fermented to increase their storability as feed. Silage can be produced by any method, for example, by drying harvested plants to a moisture content of approximately 70-80%, cutting them appropriately, sealing them under anaerobic conditions, and then subjecting them to lactic acid fermentation. Sealing the silage allows it to be stored for long periods without spoilage and also prevents the loss of carbon components due to the generation of carbon dioxide, which leads to a decrease in the calorific value of the fuel. In this embodiment, the plant-derived biomass subjected to the washing process or steam explosion process is preferably a highly storable processed plant product, such as silage. Using a highly storable processed plant product facilitates the preservation of raw materials for the production of plant-derived fuel. Furthermore, the plant-derived biomass in this embodiment may be biomass derived from any part of the plant, but when the plant in this embodiment is a herbaceous plant, it is preferable that the biomass is mainly composed of biomass derived from the stems and leaves of the herbaceous plant and contains as little biomass derived from the fruiting parts as possible.

[0014] The plant-derived fuel produced by the method of this embodiment may be in any form, but is preferably a solid fuel, and more preferably a pellet fuel. When the fuel produced by the method of this embodiment is a pellet fuel, the moisture content of the pellet fuel is preferably 10% or less, and the pellets may be black pellets. As used herein, the term "pellet fuel" refers to fuel formed into a certain shape by crushing or breaking raw materials.

[0015] Step of Washing Plant-Derived Biomass (Washing Step) The production method of this embodiment includes a step of washing plant-derived biomass. Washing the plant-derived biomass before the steam explosion step reduces the ash content contained in the plant-derived biomass, thereby reducing the ash content in the final fuel. Washing may particularly reduce ash derived from liquid components in plants, such as ash derived from the cytoplasm, vacuoles, and extracellular solutions of plant cells. As used herein, "ash" is a general term for incombustible substances. The ash in this embodiment may be any inorganic element other than oxygen, carbon, hydrogen, and nitrogen. The washing step in this embodiment may reduce inorganic elements, particularly sodium, potassium, and chlorine.

[0016] The cleaning liquid used in the cleaning step may be any cleaning liquid known to those skilled in the art, such as water, an aqueous cleaning liquid containing a surfactant, a semi-aqueous cleaning liquid containing a water-soluble solvent, or a non-aqueous cleaning liquid containing an organic solvent, but water is preferred.

[0017] The conditions in the washing step, such as the amount of washing liquid, the number of washes, the temperature, and the washing time, can be appropriately determined by a person skilled in the art as long as they can reduce the ash content in the plant-derived biomass, but preferred examples of each are described below.

[0018] It is preferable to wash the plant-derived biomass once with a washing solution having a weight that is about 2 to 5 times the total weight of the plant-derived biomass. Alternatively, it is preferable to wash the plant-derived biomass 2 to 5 times with a washing solution having a weight that is about 1 time the total weight of the plant-derived biomass. In other words, it is preferable that the total weight of the washing solution used is about 2 to 5 times the weight of the plant-derived biomass to be washed. As used herein, "about X (X is a natural number)" refers to any value within the range of values ​​that becomes X when rounded to one decimal place.

[0019] In one embodiment, the method of the present embodiment comprises washing the plant-derived biomass once with water in an amount about 2 times, about 3 times, about 4 times, or about 5 times the total weight of the plant-derived biomass, hi one embodiment, the method of the present embodiment comprises washing the plant-derived biomass two, three, four, or five times with water in an amount about 1 time the total weight of the plant-derived biomass.

[0020] The washing step is preferably carried out at room temperature, which may be, for example, about 10 to 30° C. Alternatively, washing may be carried out at a temperature higher than room temperature, in which case the total amount of washing liquid used can be reduced.

[0021] In one embodiment, the washing step is carried out at a temperature of about 10°C to 15°C, 15°C to 20°C, 20°C to 25°C, or 25°C to 30°C.

[0022] The washing time is determined appropriately depending on the amount of washing liquid, the number of washings, the washing temperature, etc., but is preferably about 5 to about 30 minutes, and more preferably about 10 to about 20 minutes.

[0023] In one embodiment, the method of this embodiment comprises washing the plant-derived biomass once for about 15 minutes with water at 20-25°C in an amount about three times the total weight of the plant-derived biomass.

[0024] The operation in the washing step can be appropriately determined by a person skilled in the art, but for example, washing may be performed by adding a washing liquid to the plant-derived biomass, shaking, and then discarding the washing liquid; washing may be performed by adding a washing liquid to the plant-derived biomass, crushing the plant-derived biomass, and then discarding the washing liquid; or washing may be performed by immersing the plant-derived biomass in a washing liquid, squeezing the immersed plant-derived biomass, and discarding the squeezed liquid.

[0025] The washing step of this embodiment can reduce the ash content in the plant-derived biomass. Preferably, the washing step reduces inorganic elements in the plant-derived biomass, particularly reducing sodium, potassium, and chlorine. When the washing step reduces sodium, potassium, and chlorine, the plant-derived biomass after washing preferably has a total mass fraction of sodium and potassium of 1800 ppm or less and a mass fraction of chlorine of 500 ppm or less, and more preferably has a total mass fraction of sodium and potassium of 1000 ppm or less and a mass fraction of chlorine of 100 ppm or less.

[0026] Compared to when the plant-derived biomass is the plant itself, when the plant-derived biomass is biomass derived from a plant whose tissues or cells have been destroyed or decomposed, the ash content, such as chlorine, sodium, and potassium, can be reduced more. By using a plant whose tissues or cells have been destroyed or decomposed, it can be easier to reduce, by washing, the ash content derived from liquid components in the plant, such as ash derived from the cytoplasm, vacuoles, and extracellular solutions of plant cells. Examples of plants whose tissues or cells have been destroyed or decomposed include shredded plants and silage. Compared to when the plant-derived biomass is the plant itself, when the plant-derived biomass is shredded plants or silage, the ash content, such as chlorine, sodium, and potassium, can be reduced more.

[0027] The washing process reduces the ash content of plant-derived biomass, such as chlorine, sodium, and potassium, and thus reduces the ash content of the fuel finally obtained after the washing process and subsequent processes such as steam explosion. The ash in the fuel generates clinker on the inner walls of machinery into which the fuel is fed, such as combustion furnaces. The clinker can prevent machinery from operating normally, resulting in reduced availability. The method of this embodiment, which includes a washing process, can produce fuel with reduced ash content that causes less damage and trouble to machinery such as combustion furnaces.

[0028] Furthermore, since the method of this embodiment can reduce the amount of ash in the fuel, the ash content reduction effect can be more pronounced when the raw material plant is a plant that contains a lot of ash, such as a herbaceous plant.

[0029] Here, the reduction in ash content such as chlorine, sodium, and potassium can be evaluated by a person skilled in the art as appropriate, and can be evaluated, for example, by optical emission spectroscopy. Specific examples of optical emission spectroscopy include inductively coupled plasma optical emission spectroscopy (ICP-OES, ICP-MS, etc.). Furthermore, sodium may be evaluated in accordance with the industrial wastewater testing method of Japanese Industrial Standards JIS K0102 (2016).

[0030] Fuel produced by a method that includes a step of washing plant-derived biomass has a reduced ash content, which is a non-combustible substance, and has a higher calorific value than fuel produced by a method that does not include a washing step.

[0031] Furthermore, the washing step may also reduce sugars in the plant-derived biomass. If a large amount of sugar is present in the plant-derived biomass, solidification (caramelization) may occur, damaging the inner walls of the machine used in the steam explosion step after the washing step. The method of the present embodiment, which includes a washing step, may be able to alleviate this problem. If sugars in the plant-derived biomass are reduced by the washing step, the sugars contained in the plant-derived biomass are transferred to the washing liquid by washing, and the washing liquid after washing contains sugars. The washing liquid containing sugars can be used to produce bioethanol. This embodiment may also include a step of producing bioethanol. For example, when washing is performed by adding a washing liquid to compressed plant-derived biomass and discarding the washing liquid, the sugar content of the pressed liquid obtained by compressing the plant-derived biomass may be 8 to 20 in Brix sugar content. The sugar content of the washing liquid after adding washing liquid in an amount approximately 1 to 3 times the total weight of the plant-derived biomass is preferably about 3 to 12 in Brix sugar content, more preferably about 3 to 8 or about 5 to 12.

[0032] The machines and containers used to carry out the washing step can be appropriately determined by those skilled in the art depending on the purpose. For example, a concrete mixer, a sugar juicer, a diffuser machine, etc. can be used. To carry out the washing step on a large scale, it is preferable to use a sugar juicer, a diffuser machine, etc.

[0033] After the washing step, a steam explosion step is carried out. The washed plant-derived biomass may be used in the steam explosion step as is without any treatment, but it is preferable to adjust the moisture content of the washed plant-derived biomass to preferably 70% or less, more preferably 50% or less, before using it in the steam explosion step. The method for adjusting the moisture content can be appropriately determined by those skilled in the art, but it can be adjusted, for example, by drying with heat or squeezing.

[0034] Step of steam exploding washed plant-derived biomass (steam explosion step) The method of this embodiment includes a step of steam exploding washed plant-derived biomass. Steam explosion of plant-derived biomass increases the carbon content of the plant biomass and the bulk density of the plant biomass, resulting in a higher calorific value. As used herein, "steam explosion" refers to treating a substance in a pressure-resistant vessel in the presence of high-temperature, high-pressure steam, followed by rapid decompression to expand the steam, thereby destroying and pulverizing the substance. Steam explosion may be steam explosion.

[0035] The conditions for the steam explosion step, such as pressure, temperature, and treatment time, can be appropriately determined by a person skilled in the art. The pressure is preferably 1.5 MPa to 4 MPa, and more preferably 2 MPa to 3.5 MPa. The temperature is preferably 100°C to 400°C, and more preferably 160°C to 320°C. The treatment time is preferably 5 minutes to 20 minutes, and more preferably 10 minutes to 20 minutes. These conditions may be determined as any combination, such as a combination of a preferred condition and a more preferred condition. In one embodiment, the method of this embodiment includes a step of steam exploding the washed plant-derived biomass under pressure conditions of about 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, or 3.5 MPa. In one embodiment, the method of the present embodiment comprises steam exploding the washed plant-derived biomass under conditions of about 160 to 200, 200 to 240, 240 to 280, or 280 to 320° C. In one embodiment, the method of the present embodiment comprises steam exploding the washed plant-derived biomass for about 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 minutes. In one embodiment, the method of the present embodiment includes a step of steam exploding the washed plant-derived biomass by treating it under conditions of a pressure of about 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, or 3.5 MPa and about 160 to 200, 200 to 240, 240 to 280, or 280 to 320°C for about 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 minutes.

[0036] Fuel obtained by a method including a step of steam exploding plant-derived biomass has a higher calorific value than fuel obtained by a method that does not include a steam explosion step. Furthermore, fuel obtained by a method including a step of washing plant-derived biomass and a step of steam exploding the washed plant-derived biomass has a higher calorific value than fuel obtained by a method that does not include a step of washing plant-derived biomass and includes a step of steam exploding unwashed plant-derived biomass. Furthermore, fuel obtained by a method including a step of washing plant-derived biomass and a step of steam exploding the washed plant-derived biomass has a higher calorific value than fuel obtained by a method that includes a step of washing plant-derived biomass but does not include a steam explosion step. In other words, fuel produced by a method that includes both a washing step and a steam explosion step has a higher calorific value than fuel produced by a method that includes only one of the washing step or the steam explosion step.

[0037] Step of forming steam-exploded plant-derived biomass into granules (granulation step) The method of this embodiment may further include a step of forming steam-exploded plant-derived biomass into granules. That is, the method of this embodiment may be a method for producing granular pellet fuel. The plant-derived biomass after steam explosion may be used directly in the granulation step without any treatment. However, when the moisture content of the plant-derived biomass after steam explosion exceeds 60%, it is preferable to use plant-derived biomass whose moisture content has been adjusted to preferably 60% or less, more preferably 50% or less, in the granulation step. The method for adjusting the moisture content of the plant-derived biomass after steam explosion can be appropriately determined by those skilled in the art, but it can be adjusted, for example, by concentration or compression. When adjusting the moisture content by compression, it is preferable that the compressed liquid obtained by compression is re-mixed at any timing after the granulation step. If the compressed liquid is not re-mixed, the calorific value of the final fuel obtained may be lower than when the compressed liquid is re-mixed later. That is, removing the liquid components contained in the plant-derived biomass after steam explosion by squeezing or washing can lead to a decrease in the calorific value. If the steam-exploded plant-derived biomass is not squeezed or washed, or if the steam-exploded plant-derived biomass is squeezed or washed but the squeezed liquid or washing liquid is later remixed, the calorific value of the final fuel obtained can be higher than in a case where the steam-exploded plant-derived biomass is squeezed or washed but the squeezed liquid or washing liquid is not later remixed. Therefore, the method of this embodiment does not include a step of washing the steam-exploded plant-derived biomass.

[0038] The method for forming into granules can be appropriately determined by those skilled in the art, and may be formed using a machine known to those skilled in the art, or may be formed manually. When forming using a machine, for example, a rotary kiln or the like can be used. The plant-derived biomass formed into granules can be used as fuel as is, but it is preferable to use it after adjusting the moisture content to 10% or less. The method for adjusting the moisture content after forming can be appropriately determined by those skilled in the art, and can be adjusted, for example, by natural drying or drying with heat. If the steam-exploded plant-derived biomass is compressed or washed before the granulation step, the moisture content may be adjusted after re-mixing the compressed liquid or washing liquid with the formed plant-derived biomass.

[0039] By forming the steam-exploded plant-derived biomass into granules rather than cylindrical shapes, the amount of energy input for moisture content adjustment, such as the drying process, can be reduced. That is, granular pellets have a larger surface area than cylindrical pellets, allowing more water to evaporate and making drying easier. The exploded plant-derived biomass may be naturally dried during the granulation process, making moisture content adjustment unnecessary. When a rotary kiln is used as the forming machine, the rotation of the rotary kiln can further reduce the amount of energy input for moisture content adjustment, such as drying.

[0040] The calorific value of the fuel produced in this embodiment can be evaluated appropriately by a person skilled in the art, and can be evaluated, for example, according to the calorific value testing method of Japanese Industrial Standards JIS Z7302-2 (1999).

[0041] The Hardgrove Crushability Index (HGI) of the fuel produced in this embodiment can also be calculated as appropriate by a person skilled in the art, for example, according to Coals - Testing Methods of Japanese Industrial Standards JIS M8801. The HGI may also vary depending on the conditions in the steam explosion step and other steps in the method of this embodiment.

[0042] The present invention will be specifically explained below by showing examples, but the present invention is not limited to these examples.

[0043] Sorghum washing experiments were performed using sorghum strains owned by the University of Tokyo, including a high-biomass standard strain, a high-biomass early-maturing pellet strain, a high-biomass multi-branching strain, a medium-biomass high-sugar ethanol silage strain, a dwarf standard strain, and a dwarf mutant strain. The sorghum was lactic acid fermented and silaged (hereafter referred to as the silage sample) or immediately after harvest (hereafter referred to as the immediately after harvest sample). Approximately three times the volume of water at 20-25°C was added to the silage sample and washed for 15 minutes in a cement mixer (electric concrete mixer, Mazetaro AMZ-50Y, manufactured by Almis Corporation).

[0044] Elemental analysis after washing The washed silage samples or immediately after harvest samples were subjected to elemental analysis using ICP-MS (7800 ICP MS, Agilent Technologies, Inc.) to measure the elemental content. The results of elemental analysis of immediately after harvest and silage samples of the high-biomass reference line, high-biomass early-season pellet line, and medium-biomass high-sugar ethanol silage line after washing are shown in Figures 1-1 to 1-4. The results in Figures 1-1 to 1-4 confirmed that washing reduces the concentrations of potassium and chlorine. Furthermore, the results in Figures 1-3 and 1-4 show that the potassium and chlorine concentrations were significantly reduced in the silage samples compared to the immediately after harvest samples.

[0045] Sugar content of the water after pressing The sugar content (brix sugar content) of the pressed water after pressing the samples immediately after harvest was 8 to 20. This suggests that washing reduces the sugar content in sorghum.

[0046] Steam Explosion The washed silage sample was steam exploded using a steam explosion apparatus (Steam Explosion Apparatus, Nippon Denetsu Co., Ltd.) at 2.2-3 MPa for 5-18 minutes at 200-240°C. After steam explosion, the sample was washed, pressed, concentrated, granulated (pelletized), dried, mixed with the pressed liquid, and / or re-dried to produce fuel pellets. As a comparative example, the silage sample that was not steam exploded was dried, powdered, and then shaped into a cylindrical shape to produce fuel pellets. Detailed conditions for each sample are shown in Table 1.

[0047]

[0048] Measurement of Calorific Value The higher and lower heating values ​​(kcal / kg) of each sample listed in Table 1 were measured by Sanko Environmental Research Center Co., Ltd. in accordance with the calorific value test method of Japanese Industrial Standard JIS Z7302-2 (1999), and the results are shown in Table 2. All calorific value values ​​in Table 2 are shown as values ​​converted to an anhydrous basis. The results of the comparative examples in Table 2, in which only processing such as pulverization was performed without steam explosion, indicate that the steam explosion results in a higher calorific value. The results of Examples 1-2 and 1-3 in Table 2 indicate that when steam explosion is performed and the compressed liquid is then mixed, the calorific value is higher, and when the compressed liquid is discarded without being mixed, the calorific value is lower. In other words, it is suggested that removing the liquid contained in the sample after steam explosion by squeezing or washing may lead to a decrease in the calorific value. Furthermore, the results of Examples 1-4 and 1-5 in Table 2 indicate that washing before steam explosion results in a higher calorific value.

[0049]

[0050] Furthermore, a comparison of the higher and lower heating values ​​of a silage sample from a medium-biomass, high-sugar ethanol silage strain that had been washed and pressed with a silage sample from the same strain that had not been treated in any way confirmed that the silage sample that had been washed and pressed had a higher heating value (Figure 2). The heating value values ​​in Figure 2 are shown as values ​​converted on an arrival basis.

[0051] Measurement of Hardgrove Crushability Index (HGI) 50 g of the fuel pellets prepared above were crushed 60 times in a Hardgrove Crushability Tester (1134-S, Yoshida Seisakusho Co., Ltd.), and the crushed product was sieved through a sieve with 75 μm mesh. The mass above the sieve was measured to the nearest 0.01 g, and this value was subtracted from 50 g to obtain the mass under the sieve, W (g), and the Hardgrove Crushability Index (HGI) was calculated using the following formula: <Formula> HGI = 13 + 6.93 * W The calculated HGI of the fuel pellets prepared above was 48 to 59.

Claims

1. A method for producing plant-derived fuel, comprising: washing plant-derived biomass; and steam exploding the washed plant-derived biomass, but not washing the steam-exploded plant-derived biomass.

2. The method according to claim 1, wherein the plant-derived biomass is biomass derived from one or more plants selected from the group consisting of sorghum, erianthus, giant miscanthus, napier grass, switchgrass, corn, sugarcane bagasse, kenaf, pearl millet, foxtail millet, finger millet, and bamboo.

3. The method according to claim 1 or 2, wherein the steam explosion is carried out under a pressure of 2.5 to 3.5 MPa for 10 to 20 minutes.

4. The method according to claim 1 or 2, wherein washing is carried out with water.

5. The method of claim 1 or 2, wherein washing reduces inorganic elements in the plant-derived biomass.

6. The method according to claim 1 or 2, wherein the sum of the mass fraction of sodium and the mass fraction of potassium in the washed plant-derived biomass is 1800 ppm or less, and the mass fraction of chlorine is 500 ppm or less.

7. The method of claim 1 or 2, further comprising forming the steam exploded plant-derived biomass into granules.

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