Retention of low-temperature carbonized woody biomass by coating with by-product tar during low-temperature carbonization of woody biomass; method for retention of woody biomass.

Abstract

This invention provides a method for making woody biomass low-temperature carbonized materials difficult to decompose. [Solution] The wood biomass low-temperature carbonization process involves dissolving and recovering by-product tar that condenses and adheres to the inner wall of the pyrolysis gas channel during low-temperature carbonization of wood biomass at a carbonization temperature of less than 350°C using an organic solvent; immersing the wood biomass low-temperature carbonized material in the organic solvent by-product tar solution produced by the above step; and drying the wood biomass low-temperature carbonized material subjected to the above step, thereby coating the surface of the wood biomass low-temperature carbonization material with wood biomass low-temperature carbonization by-product tar and making it difficult to decompose. The wood biomass low-temperature carbonized material involves placing the wood biomass low-temperature carbonized material in a coating container; heating and maintaining the coating container from the above step at 110 to 180°C; and introducing pyrolysis gas generated during low-temperature carbonization of wood biomass at a carbonization temperature of less than 350°C into the coating container from the above step, thereby coating the surface of the wood biomass low-temperature carbonization material with wood biomass low-temperature carbonization by-product tar and making it difficult to decompose.

Description

Technical Field

[0001] The present invention relates to a countermeasure against global warming, which coats the surface of a low-temperature woody biomass carbide produced by carbonization at a carbonization temperature of less than 350 ° C (hereinafter referred to as low-temperature carbonization) with tar by-produced during the low-temperature carbonization of woody biomass (hereinafter referred to as by-produced tar), and utilizes the antibacterial and insect-proof effects of terpenoids, steroids, etc. contained in the by-produced tar and the film-forming effect of the thermal decomposition products contained in the by-produced tar to make the low-temperature woody biomass carbide hardly decomposable, thereby enabling long-term stable storage of carbon derived from carbon dioxide in the atmosphere absorbed and fixed by the woody biomass during growth. Background Countermeasures against global warming

[0002] In the guidelines issued by the Intergovernmental Panel on Climate Change (IPCC) (IPCC 1997, 2000, 2003, 2006) regarding climate change, the absorption and fixation of carbon dioxide during the growth of woody biomass is to reduce greenhouse gases in the atmosphere, and carbon storage by storing woody biomass or processed woody biomass products is defined as one of the countermeasures against global warming.

[0003] If appropriate management is implemented, like the Horyuji Temple (built in 607 AD), woody biomass can be stably stored for more than a thousand years. However, empty houses collapse within decades due to damage by food-eating insects such as termites. As described in [Non-Patent Document 1], forest thinning residues and fallen trees are decomposed within decades by wood parasitic fungi such as mushrooms and food-eating insects such as termites. It is difficult to continuously implement appropriate management such as antibacterial and insect-proof measures for woody biomass for a long time. Countermeasures against global warming by producing woody biomass carbide

[0004] The production of woody biomass carbide, for example, using an externally heated pyrolysis furnace to produce woody biomass carbide by indirect heating at a temperature of 300 ° C to 700 ° C in a low-oxygen atmosphere has been widely carried out conventionally.

[0005] [Non-Patent Literature 2] In the IPCC guidelines, carbonization is recognized as one of the processing methods that make woody biomass less susceptible to decomposition even without proper management. In the J-Credit system, in which the Japanese government certifies greenhouse gas emission reductions and absorptions as credits, carbonization is also recognized as one of the processing methods that makes woody biomass less susceptible to decomposition even without proper management. Woody biomass carbonization temperature and carbon retention rate after 100 years in underground storage

[0006] According to [Non-Patent Literature 3], the cell wall is thick and strong in order to support the woody biomass. The cell wall is mainly composed of cellulose, lignin, and hemicellulose. According to [Non-Patent Literature 4], almost all hemicellulose decomposes at temperatures above 290°C. Cellulose and lignin hardly decompose at temperatures below 350°C. Low-temperature carbonized woody biomass produced at temperatures below 350°C contains large amounts of cellulose and lignin, and therefore may be decomposed by wood-parasitic fungi and insects that feed on wood if stored in soil. As the carbonization temperature increases, the decomposition of cellulose and lignin progresses, releasing oxygen, hydrogen, and carbon. Since oxygen and hydrogen are released more easily than carbon, more carbon remains, and the carbon content of woody biomass char is relatively high. According to [Non-Patent Literature 5], the carbon content of woody biomass char is 55.79% at carbonization temperatures of 300°C, 71.81% at 400°C, 80.66% at 500°C, 89.12% at 600°C, and 92.06% at 700°C. Since lumps of carbon are difficult to decompose, when stored in soil, the higher the carbonization temperature, the more difficult it is for woody biomass char to decompose. According to [Non-Patent Literature 2] Vol.4, Ch2, Ap4.4, Figure 4 Ap.1, when woody biomass char is stored in soil, the IPCC guideline defined values ​​for the carbon retention rate after 100 years, with the initial carbon content in the woody biomass char being 100%, are: 300℃: 56.8%, 400℃: 66.2%, 500℃: 75.7%, 600℃: 85.1%, and 700℃: 96.0%.

[0007] When stored in soil, the IPCC guideline definition of carbon retention rate after 100 years for low-temperature carbonized woody biomass is low. Therefore, in the international carbon emissions trading market, low-temperature woody biomass char is traded at about half the price of woody biomass char produced at carbonization temperatures of 350°C or higher. Under the J-Credit scheme, woody biomass carbonized at temperatures of 350°C or higher is defined as "biochar," and biochar is traded for a fee as a carbon credit. On the other hand, the storage of low-temperature woody biomass carbonized in soil is not recognized as a carbon credit. However, as will be explained in the following sections, low-temperature carbonized woody biomass also has characteristics suitable for combating global warming, such as (1) a high carbon retention rate after carbonization, (2) a low amount of greenhouse gases such as carbon dioxide, carbon monoxide, and methane released into the atmosphere during carbonization, and (3) low energy requirements for carbonization. Woody Biomass Carbonization Temperature and Carbon Retention Rate After Carbonization

[0008] Although carbon is less readily released than oxygen and hydrogen, as the carbonization temperature increases, the amount of carbon released during carbonization increases, while the amount of carbon remaining in the woody biomass char decreases. According to [Non-Patent Literature 5], if the amount of carbon in the raw woody biomass is considered to be 100%, the carbon retention rate in the char is 75.9% at 300°C, 50.0% at 400°C, 48.7% at 500°C, 50.5% at 600°C, and 48.6% at 700°C. The carbon retention rate of woody biomass charred at temperatures above 350°C is approximately 50% or less, and the remaining carbon is released into the atmosphere as greenhouse gases such as carbon dioxide, carbon monoxide, and methane. Carbon monoxide is a precursor of carbon dioxide. According to IPCC guidelines, the greenhouse effect of methane is 28 times that of carbon dioxide (IPCC 2006).

[0009] As the carbonization temperature increases, the energy required for carbonization also increases. Antibacterial and insecticidal effects of bioactive substances within woody biomass cells.

[0010] Almost all woody biomass synthesizes and stores terpenes and steroids with physiological activity, such as antibacterial and insecticidal effects, within its cells. The distinctive scent of wood is mainly due to terpenes and steroids. Japanese cedar (Cryptomeria japonica) and Japanese cypress (Hinoki cypress) have strong scents because they contain large amounts of terpenes and steroids. Terpenes in Japanese cedar include ferruginol and sugiol, while terpenes in Japanese cypress include ferruginol and hinothiol. According to [Non-Patent Literature 6], the ferruginol content of natural Japanese cedar is about 0.2%. According to [Non-Patent Document 7], terpenes and steroids such as ferginol have antibacterial effects and inhibit the growth of mushroom mycelium. Japanese cedar and cypress contain large amounts of terpenes and steroids and are therefore not used in mushroom cultivation. Broad-leaved trees such as oak and sawtooth oak have low terpene and steroid content and are used in mushroom cultivation. Diterpenes and steroids also have insecticidal effects. Before the chemical synthesis of paradichlorobenzene and other compounds, cypress and cedar were used as insecticides. Pyrolysis gases and by-product tars are generated during the carbonization of woody biomass.

[0011] The carbonization of woody biomass decomposes the hemicellulose, cellulose, and lignin that make up the cell walls, generating thermal decomposition products such as phenols, sugars, furans, and alcohols. These thermal decomposition products further decompose to produce carbon dioxide, carbon monoxide, methane, and other substances. The carbonization of woody biomass breaks down cell walls, releasing intracellular substances such as terpenes and steroids. Pyrolysis gases are a mixture of pyrolysis products, gases such as carbon dioxide, carbon monoxide, and methane, and substances such as terpenes and steroids. Terpenes, steroids, and thermal decomposition products (phenols, sugars, furans, alcohols, etc.) condense and adhere to the inner wall of the thermal decomposition gas flow path in the portion below approximately 220°C. This deposited material is the by-product tar. According to [Non-Patent Literature 6] and [Non-Patent Literature 8], by-product tar contains high concentrations of terpenes and steroids. For example, the ferginol concentration in by-product tar is approximately 12%. [Background technology]

[0012] The inventors of this invention, in collaboration with a company, have invented and patented a method for efficiently recovering terpenes and steroids from by-product tar adhering to the inner wall of a pyrolysis gas channel during low-temperature carbonization (Patent No. 6726912). The inventors of this invention have invented and patented a method for efficiently separating terpenes, steroids, and thermal decomposition products from by-product tar during low-temperature carbonization, and a method for utilizing the separated thermal decomposition products as a binder for briquetting (Patent No. 7011138). As described in Japanese Patent No. 7011138, the pyrolysis products undergo condensation polymerization to form an insoluble film. This allows the separated pyrolysis products to be used as a binder. [Overview of the project] [Problems that the invention aims to solve]

[0013] Low-temperature carbonized woody biomass produced by carbonization at temperatures below 350°C has characteristics suitable for combating global warming, such as a high carbon retention rate after carbonization, low release of greenhouse gases into the atmosphere during production, and low energy consumption during production. However, because it contains a large amount of cellulose and lignin, it has properties similar to woody biomass and is easily decomposed by wood-parasitic fungi and food-eating insects. For example, when stored in soil, the carbon retention rate after 100 years is approximately 60%. Due to this drawback, the trading price of woody biomass cryogenic char in the international carbon emissions trading market is about half the price of woody biomass char produced at carbonization temperatures of 350°C or higher. Under the J-Credit program, the storage of woody biomass cryogenic char in soil is not recognized as eligible for carbon credits. [Means for solving the problem]

[0014] According to [Non-Patent Literature 7], cedar prevents the growth of wood-parasitic fungi such as mushrooms due to the antibacterial action of ferginol, etc. According to [Non-Patent Literature 6], the ferginol content in natural cedar is about 0.2%. Before the chemical synthesis of paradichlorobenzene and other compounds, cypress and cedar were used as insecticides. Terpenes and steroids also possess insecticidal properties. According to [Non-Patent Literature 6] and [Non-Patent Literature 8], tar produced as a by-product during low-temperature carbonization at temperatures below 350°C contains high concentrations of terpenes, steroids, and thermal decomposition products (phenols, sugars, furans, alcohols, etc.). For example, the ferruginol concentration in the by-product tar is approximately 12%. Coating the surface of low-temperature carbonized woody biomass with by-product tar prevents the growth of wood-parasitic fungi and food-eating insects due to the antibacterial and insecticidal effects of terpenes and steroids. According to [Non-Patent Document 9], wood-parasitic fungi require an oxygen concentration of 20% or more for reproduction. Food-eating insects require an oxygen concentration of approximately 20% for survival. Because carbonization is carried out in a low-oxygen environment, the inside of the woody biomass low-temperature carbonized material is low in oxygen immediately after production. When the surface of the woody biomass low-temperature carbonized material is coated with by-product tar, the thermal decomposition products form a film, which can maintain the low-oxygen environment inside. As a result, wood-parasitic fungi cannot proliferate inside the woody biomass low-temperature carbonized material, and food-grade insects cannot survive. By coating the surface of low-temperature carbonized woody biomass with by-product tar, the antibacterial and insecticidal effects of terpenes and steroids contained in the by-product tar, as well as the film formation of thermal decomposition products, prevent the proliferation of wood-parasitic fungi and the survival of insects that feed on wood, thereby making the low-temperature carbonized woody biomass difficult to decompose. [Effects of the Invention]

[0015] By coating the surface of low-temperature carbonized woody biomass with tar, a by-product of carbonization at temperatures below 350°C, the antibacterial and insecticidal effects of diterpenes and steroids contained in high concentrations in the by-product tar, as well as the thermal decomposition products that form a film on the surface and maintain a low-oxygen state inside, make the low-temperature carbonized woody biomass difficult to decompose, thereby increasing the carbon retention rate after 100 years. By solving the drawback of easily decomposable low-temperature carbonized woody biomass, it is possible to make use of characteristics suitable for measures against global warming, such as (1) high carbon residual rate during carbonization, (2) less greenhouse gas emissions into the atmosphere during production, and (3) less energy consumption during production. As a result, low-temperature carbonized woody biomass can be made one of the effective measures against global warming. By increasing the carbon residual rate after 100 years, it is possible to raise the trading price of low-temperature carbonized woody biomass in the international carbon emission trading market and promote its spread.

Prior Art Documents

[0016]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

[0017] Mushrooms such as shiitake and enoki are common wood-parasitic fungi. A substrate in which the highly prolific oyster mushroom, *Pleurotus ostreatus*, is planted on broadleaf tree sawdust is commercially available for raising stag beetles and other insects. Stag beetles cannot decompose woody biomass. *Pleurotus ostreatus* breaks down the cellulose, hemicellulose, and lignin contained in broadleaf trees into sugars and other substances that stag beetles can utilize. This *Pleurotus ostreatus* substrate has bran and sugars added to the broadleaf tree sawdust to facilitate the growth of *Pleurotus ostreatus*. First, we mixed oak sawdust (a type of broadleaf tree) or cedar sawdust with oyster mushroom substrate to confirm the antifungal effect of woody biomass. In the case of a 50% oak sawdust + 50% oyster mushroom substrate mixture, and a 80% oak sawdust + 20% oyster mushroom substrate mixture, the surface of the mixture was covered with white oyster mushroom mycelium after 20 days of storage at room temperature. In the case of a 90% oak sawdust + 10% oyster mushroom substrate mixture, the surface of the mixture did not change. In all cases of 50% / 80% / 90% cedar sawdust + 50% / 20% / 10% oyster mushroom substrate mixtures, the surface of the mixture did not change after 20 days of storage at room temperature. We were able to confirm that oak has some degree of antibacterial effect. Although it is less than that of cedar, this is thought to be because oak also contains terpenes and steroids. We were able to confirm that cedar has a high antibacterial effect. The results are shown in Table 1. If the surface did not change, it was judged to have an antibacterial effect and marked with ○. If the surface was covered with white oyster mushroom mycelium, it was judged to have no antibacterial effect and marked with ×.

[0018] Low-temperature carbonized cedar sawdust (hereinafter referred to as "low-temperature cedar carbonized material") was prepared by low-temperature carbonization of cedar sawdust at a carbonization temperature of 300°C. The antimicrobial effect was measured by mixing this carbonized material with Pleurotus ostreatus mushroom substrate. In all cases (50% / 80% / 90% cedar carbonized material + 50% / 20% / 10% Pleurotus ostreatus mushroom substrate), the surface of the mixture was covered with a white layer of Pleurotus ostreatus mycelium after 20 days of storage at room temperature. Low-temperature carbonization releases terpenes and steroids. Therefore, low-temperature cedar carbonized material does not have antimicrobial effect. The results are shown in Table 2.

[0019] Cedar sawdust was carbonized at a low temperature of 300°C, and after the low-temperature carbonization was completed, by-product tar was dissolved and recovered from the inner wall of the pyrolysis gas flow path using an organic solvent (acetone). The low-temperature carbonized cedar was then immersed in this organic solvent solution containing the dissolved by-product tar, dried, and coated with the by-product tar on its surface (hereinafter referred to as by-product tar coated low-temperature carbonized cedar). The antimicrobial effect was measured by mixing oyster mushroom substrate with by-product tar-coated cedar low-temperature carbonized material. In all cases of mixing by-product tar-coated cedar low-temperature carbonized material (50% / 80% / 90%) + oyster mushroom substrate (50% / 20% / 10%), the surface of the mixture did not change after 20 days of storage at room temperature. By-product tar-coated cedar low-temperature carbonized material has antimicrobial effect. The results are shown in Table 2.

[0020] An external thermal decomposition furnace and a coating furnace were prepared, and the outlet of the external thermal decomposition furnace and the inlet of the coating furnace were connected with a stainless steel pipe. Cedar sawdust was filled into the external thermal decomposition furnace and carbonized at a carbonization temperature of 300°C. The low-temperature carbonized cedar material, which had been pre-carbonized at 300°C, was filled into the coating furnace, and the coating furnace temperature was heated and maintained at 110°C / 150°C / 180°C / 200°C / 220°C. Nitrogen gas was supplied from the inlet of the external thermal decomposition furnace, and the thermal decomposition gas generated during the low-temperature carbonization of the cedar sawdust was introduced into the coating furnace, condensing and coating the surface of the low-temperature carbonized cedar material with by-product tar contained in the thermal decomposition gas (hereinafter referred to as 110°C / 150°C / 180°C / 200°C / 220°C by-product tar coated low-temperature carbonized cedar material). Since the pyrolysis gas contains carbon monoxide, methane, etc., an electric heating element attached to the outlet of the coating furnace was heated to burn the pyrolysis gas. A mixture of 50% / 80% / 90% by-product tar-coated cedar low-temperature carbonized material and 50% / 20% / 10% oyster mushroom substrate was stored at room temperature for 20 days. The by-product tar-coated cedar low-temperature carbonized material exhibited antibacterial effects when the heat retention temperature during pyrolysis gas introduction was 110°C, 150°C, and 180°C, and partially exhibited antibacterial effects when the heat retention temperature was 200°C and 220°C. The results are shown in Table 3. A brief explanation of the table follows.

[0021] [Table 1] Oak sawdust / cedar sawdust: 50% / 80% / 90% + Pleurotus ostreatus mushroom substrate: 50% / 20% / 10% mixture, stored at room temperature for 20 days. ○: No surface change = antibacterial effect present, ×: Surface covered with white Pleurotus ostreatus mycelium = no antibacterial effect. [Table 2] Low-temperature carbonized cedar / by-product tar coating. Low-temperature carbonized cedar: 50% / 80% / 90% + Pleurotus ostreatus mycelium: 50% / 20% / 10% mixture, stored at room temperature for 20 days. ○: No surface change = antibacterial effect present, ×: Surface covered with white Pleurotus ostreatus mycelium = no antibacterial effect. [Table 3] Mixture of 110℃ / 150℃ / 180℃ / 200℃ / 220℃ by-product tar-coated cedar low-temperature carbonized material: 50% / 80% / 90% + Pleurotus ostreatus mycelium: 50% / 20% / 10%, stored at room temperature for 20 days. ○: No surface change = antibacterial effect present, ×: Surface covered with white Pleurotus ostreatus mycelium = no antibacterial effect. [Brief explanation of the drawing]

[0022] [Figure 1] A mixture of 50% low-temperature carbonized cedar and 50% Pleurotus ostreatus mushroom substrate was stored at room temperature for 20 days, after which the surface was covered with a white layer of Pleurotus ostreatus mycelium. [Figure 2] A mixture of 50% cedar low-temperature carbonized by-product tar-coated material produced at 110℃ and 50% oyster mushroom substrate was stored at room temperature for 20 days, with no surface changes observed. [Figure 3]Schematic diagram of a combination of a rotary kiln-type externally heated pyrolysis furnace for low-temperature carbonization (internal cylinder temperature: less than 350°C) and a rotary kiln-type coating furnace (internal cylinder temperature: 110 to 180°C). This method enables the continuous production of low-temperature carbonized woody biomass coated with by-product tar from low-temperature carbonization of woody biomass. Woody biomass raw material is supplied to the inner cylinder of the pyrolysis furnace. Hot gas is supplied to the outer cylinder of the pyrolysis furnace to heat the internal temperature of the inner cylinder to less than 350°C. Because the pyrolysis furnace is tilted, as the inner cylinder rotates, the woody biomass gradually moves from the supply side to the discharge side while being carbonized. Low-temperature carbonized woody biomass and pyrolysis gas are supplied from the inner cylinder of the pyrolysis furnace to the inner cylinder of the coating furnace. Hot gas is supplied to the outer cylinder of the coating furnace to heat the internal temperature of the inner cylinder to 110 to 180°C. Because the coating furnace is tilted, rotating the inner cylinder of the coating furnace causes the woody biomass low-temperature carbonized material to gradually move from the supply side to the discharge side. During this movement, the by-product tar coats the surface of the woody biomass low-temperature carbonized material. The inner cylinders of the pyrolysis furnace and the coating furnace can be integrated if the internal temperature of the pyrolysis furnace inner cylinder can be controlled to less than 350°C and the internal temperature of the coating furnace inner cylinder to 110 to 180°C. The experimental apparatus used for this patent application consists of (1) a pyrolysis furnace in which cedar sawdust is packed into a quartz pipe and heated using an electric furnace, (2) a coating furnace in which pre-carbonized cedar sawdust low-temperature carbonized material is packed into another quartz pipe and heated using an electric heater, and (3) stainless steel pipes connecting these two quartz pipes, and low-temperature carbonization and coating are performed in a batch system. Thermometers were installed inside each quartz pipe to measure and control the internal temperature. Nitrogen gas was supplied from the inlet of the pyrolysis furnace. Since the exhaust gas from the coating furnace contains carbon monoxide, methane, etc., an electric heating element attached to the outlet of the coating furnace was heated to burn off the exhaust gas. [Table 1] [Table 2] [Table 3]

Claims

1. By coating the surface of woody biomass low-temperature carbonized material, produced by low-temperature carbonization at temperatures below 350°C, with tar, a by-product of woody biomass low-temperature carbonization, the decomposition of the woody biomass low-temperature carbonized material is made more difficult.

2. A method for making woody biomass low-temperature carbonized products difficult to decompose involves coating the surface of woody biomass low-temperature carbonized products, which are produced by low-temperature carbonization at temperatures below 350°C, with an organic solvent solution obtained by dissolving and recovering tar produced as a by-product during woody biomass low-temperature carbonization, and then drying the solution.

3. A method for making woody biomass low-temperature carbonized charred material difficult to decompose involves placing woody biomass low-temperature carbonized charred material, produced by low-temperature carbonization at temperatures below 350°C, into a coating furnace heated and maintained at a temperature of 110°C to 180°C, introducing pyrolysis gas produced as a by-product during low-temperature carbonization of woody biomass into the coating furnace, and condensing and adhering the by-product tar to the surface of the woody biomass low-temperature carbonized charred material to create a coating.

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