Porous charcoal pellets for soil improvement and their manufacturing method

Abstract

It has a bacteriostatic effect that regulates the balance of microbial communities in the soil, suppressing harmful bacteria and stably activating beneficial bacteria. [Solution] A mixture is made by mixing carbonized rice husks (rice husk charcoal) with an aqueous solution of naturally derived starch that has been heated and gelatinized. This mixture is then granulated and dried to obtain porous pellets, in which the carbonized rice husks have a moisture content of 4% or less, a pH of 7-8, and fine pores of 1-2 nm and medium pores of 3-50 nm.

Description

[Technical Field]

[0001] The present invention relates to a porous smoked charcoal pellet for agricultural soil improvement that promotes crop growth and a method for producing the same. More specifically, the present invention relates to a porous smoked charcoal pellet for soil improvement having a bacteriostatic effect that inhibits harmful bacteria and colonizes beneficial bacteria, which is produced by carbonizing plant-derived biomass such as rice husks under oxygen-deficient conditions to obtain a carbon material, then solidifying the carbon material with a carbohydrate-based binder derived from natural sources such as starch, and forming the mixture into pellets, and a method for producing the same. [Background Art]

[0002] Traditionally, in rice producing regions, the use of rice husks and smoked rice husk charcoal as soil conditioners, processed into powder or granules and spread in farmland, has been employed since ancient times. Alternatively, they are mixed into soil as a medium together with artificial zeolite or the like, and used as a soil conditioner (see, for example, Patent Document 1). These soil conditioners are known to have the functions of improving air permeability, increasing water retention capacity and fertilizer retention capacity, in addition to the function of decomposing harmful components by microorganisms. These conventional soil conditioners using rice husks and smoked rice husk charcoal are used in powder form or coarse granular form. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2012-103 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] However, conventional soil conditioners made from rice hulls and rice hull charcoal do not provide stable colonization of microorganisms even when added, and do not necessarily produce long-term effects. Generally, it is said that pathogenic bacteria (Fusarium, Pythium, etc.) become dominant in acidic soils. Powdered rice hulls and rice hull charcoal soil conditioners generate dust during fertilization, worsening the working environment. On the other hand, if rice hulls and rice hull charcoal soil conditioners have a porous structure similar to activated carbon, which has been chemically or physically treated to increase adsorption efficiency, they will not function as soil conditioners. Conventional rice hull charcoal soil conditioners have the function of adsorbing components necessary for the proliferation of beneficial bacteria, like activated carbon, and do not necessarily promote the proliferation of only beneficial bacteria. Soil for growing crops should ideally have a bacteriostatic effect (an effect that inhibits the growth and proliferation of harmful microorganisms) that balances the microbial community in the soil, suppressing harmful bacteria and stably activating beneficial bacteria.

[0005] The object of the present invention is to provide porous charcoal pellets for soil improvement and a method for producing the same, which have a bacteriostatic effect that balances the microbial community in the soil in order to suppress harmful bacteria and stably activate beneficial bacteria. [Means for solving the problem]

[0008] The porous biomass pellets for soil improvement according to the present invention 1 are A porous pellet is obtained by heating and gelatinizing a carbon material made from plant-derived biomass carbonized under oxygen-deficient conditions, a naturally derived sugar-based binder, mixing it with the carbon material, and then granulating and drying it. The carbon material has a water content of 4% or less, a pH of 7-8, and has fine pores of 1-2 nm and medium pores of 3-50 nm. The aforementioned carbon material is rice husk charcoal, which is obtained by carbonizing rice husks to a carbon content of 30-50%. The carbohydrate binder is a naturally derived starch obtained from one or more selected from cassava starch, rice starch, corn starch, and wheat starch. The aforementioned Porous pellets It is characterized by creating a bacteriostatic environment that suppresses acid-causing pathogens by promoting the dominance of beneficial bacteria in the soil.

[0009] The method for producing porous biomass pellets for soil improvement according to the present invention 1 is a method for producing porous biomass pellets for soil improvement according to the present invention 1, The aforementioned Porous pellets The product is characterized by mixing the rice husk charcoal and the sugar-based binder in heated hot water to form a paste solution, granulating it into cylindrical shapes with an outer diameter of 4 to 6 mm, sun-drying it, and then finally drying it at 60 to 90°C to achieve a moisture content of 4% or less.

[0010] [Biomass, carbon materials] In this invention, biomass refers to rice husks, coconut shells, bamboo, wood, rice straw, and other plant-derived materials. In this invention, carbon material refers to biomass that has been carbonized under oxygen-deficient conditions. [Carbohydrate Binder] In this invention, a carbohydrate-based binder refers to a naturally derived substance such as starch, cassava starch, rice starch, corn starch, wheat starch, sugar, molasses, cellulose derivatives, and chitosan, which has the function of solidifying or bonding carbon materials into granules. [Rice husks, and rice husk charcoal] In this invention, "rice husk" refers to the outermost layer of the rice grain (paddy rice), also known as coarse bran, polished bran, hulled bran, or simply rice husk. Rice husk charcoal is produced by carbonizing these rice husks in an oxygen-free environment using conventional methods. [starch] The starch referred to in this invention is a naturally occurring polysaccharide that is universally present in plant tissues, is an important energy source for animals including humans, and is a naturally derived starch obtained from plants such as rice, potatoes, wheat, and cassava.

[0011] [Gelatinization of starch] Gelatinization of plant-derived starch is a phenomenon in which starch molecules lose their regularity and become paste-like when heated with water. This heated paste-like substance is mixed with rice husk charcoal and granulated to form the porous biomass pellets for soil improvement described in this invention. [Pelletization] The porous biomass pellets for soil improvement of the present invention are prepared by mixing carbon material and starch in a paste-like solution using a mixer or by hand, compressing and granulating the mixture in a granulator into cylindrical, spherical, or other shapes with a particle size of 4 to 6 mm and a length of 4 to 6 mm or more, and then drying them at 60 to 90°C to reduce the moisture content to 4% by weight or less.

[0012] [Minor pores, medium pores] The carbon material produced by carbonizing plant-derived biomass under oxygen-deficient conditions according to the present invention has micropores of 1 to 2 nm and medium pores of 3 to 50 nm. These micropores and medium pores can be observed using an electron microscope. Furthermore, they can be identified and observed using the adsorption amounts of iodine and methylene blue, which are used in the observation of activated carbon.

[0013] [Micropore] The carbon material of the present invention has a larger specific surface area the more micropores it has, making it easier for air, water, and microorganisms to accumulate. Micropores can be confirmed by iodine adsorption performance and electron microscopy. Iodine adsorption performance is an indicator of the surface area and adsorption capacity of an adsorbent. Specifically, the more iodine it can adsorb, the higher the performance of the adsorbent. Commercially, for activated carbon, an iodine value of 150 or higher is generally considered to be common. In the case of rice husk charcoal, the iodine adsorption performance is approximately 120 mg / g, as shown in Table 2 below. From this value and observation with an electron microscope, it can be seen that rice husk charcoal has micropores of 1 to 2 nm. This iodine adsorption performance value is milder than that of activated carbon and is within the optimal range for agricultural biochar. The micropores of rice husk charcoal provide an exquisite balance that neither excessively absorbs microorganisms and their nutrients nor allows them to escape. In other words, it has high aeration and water retention, making it easy for added beneficial bacteria to thrive.

[0014] (middle hole) Furthermore, the carbon material of the present invention has mesopores of 3 to 50 nm. The size of these mesopores is confirmed by a methylene blue adsorption test, which is known as a standard method for measuring the adsorption amount of methylene blue on adsorbents such as bentonite. The methylene blue adsorption amount of the carbon material used in the present invention is about 50 mg / g or less. From this methylene blue adsorption amount and observation with an electron microscope, the rice husk charcoal of the present invention has mesopores of 3 to 50 nm. These mesopores gently retain nutrients and moisture and prevent drying, so they also function to promote and maintain aggregation of soil particles.

[0015] Based on the present invention described above, an outline of the mechanism (action and function) of the biomass pellets for soil improvement of the present invention is as shown in Table 1 below. [Table 1] [Effects of the Invention]

[0016] The effects of the porous biomass pellets for soil improvement of the present invention can be summarized as follows. (1) Useful bacteria become dominant and suppress pathogenic bacteria (bacteriostatic action), (2) Fertilizer retention and slow-release properties are improved, (3) Carbon fixation amount and density are increased (for example, the carbon content is about 4 times that of non-granulated rice husk smoke charcoal), (4) It has high LCA (Life Cycle Assessment) efficiency and conforms to international credit schemes for carbon dioxide reduction. [Brief Description of Drawings]

[0017] [Figure 1] FIG. 1 is a schematic process diagram showing an example of a method for producing porous biomass pellets for soil improvement using rice husk charcoal. [Mode for Carrying Out the Invention]

[0018] The embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a schematic diagram of a process showing an example of a method for producing porous biomass pellets for soil improvement using rice husk charcoal. The outline of the manufacturing process is as follows (1) to (7). (1) Charcoal smoking (steaming) "1. Charcoal production (steaming)" shown in Figure 1 refers to a process where rice husks are used as the carbon material, and the rice husks are steamed to produce rice husk charcoal. Under oxygen-deficient conditions with an oxygen concentration of approximately 10% or less, the firing conditions involve heating at a temperature of 380-450°C for approximately 16 hours to carbonize the rice husks to a carbon content of approximately 30-50%. The rice husk charcoal producer used in "(1) Production of rice husk charcoal" in Figure 1 carbonizes the rice husks by burning them in an oxygen-free environment. Various types of rice husk charcoal producers, such as batch type and continuous type, are known and commercially available on the market for this steaming process. Furthermore, the rice husk charcoal used as the raw material in this embodiment is also produced using these general-purpose products, and no special equipment is required.

[0019] (2) Extinguishing a fire by oxygen depletion "2. Oxygen-deficient fire extinguishing" shown in Figure 1 involves placing the steamed rice husk charcoal into a so-called fire extinguishing pot and sealing it. This process completely stops combustion by sealing the rice husk charcoal so that no air can enter and oxygen is cut off. (3) Starch solution production The "starch solution production" shown in Figure 1 is the production of a paste-like starch solution by heating plant-derived starch. Plant-derived starch, such as detoxified cassava flour, is added to water to a concentration of approximately 8% relative to the water. The mixture is heated until the starch becomes paste-like (gelled). Gelation, also known as alpha-(α) formation, is a process that makes the starch more soluble in hot water and gives it properties such as viscosity and water retention. The heating temperature for gelation varies depending on the type of starch, but is generally around 55°C to 85°C. When using modified starch, the gelation temperature varies depending on the degree of various treatments such as cross-linking, acid treatment, and acetylation, so it should be adjusted according to the type of modified starch.

[0020] (4) Mixture of charcoal + starch solution Figure 1 shows "4. Mixing of charcoal and starch solution," which is a process of mixing rice husk charcoal, a biomass carbon material, with a paste-like starch solution. Rice husk charcoal and a mixture containing starch solution are placed in a rotating drum and mixed uniformly to form a mixture. (5) Carbonized granules The "charcoal granules" shown in Figure 1 are produced by a process that transforms the above mixture, which is in powder or granular form, into small, solid granules of a specific shape and size through processes such as compression and granulation. This pelletization of the mixture makes it easier to handle, as it does not scatter when used for fertilization, etc. The above mixture is transformed into spherical or cylindrical pellets using a granulator such as a compression granulator. The compression granulator does not need to be special; any commercially available general granulator that does not deform enough to maintain a spherical or cylindrical shape when the pellets are dried and used is acceptable, and pressurized compression is not essential.

[0021] (6) Sun drying (temporary drying) "6. Sun drying (initial drying)" shown in Figure 1 is sun drying to dry the pellets granulated in "(5) Charcoal granulation" above, reducing the moisture content to approximately 7-10%. (7)Final drying "7. Final Drying" shown in Figure 1 is the process of drying the pellets, which have a moisture content of approximately 7-10% after "(6) Sun-drying (initial drying)" above, in a dryer at approximately 60-90°C until the moisture content is reduced to approximately 4% or less. The rice husk charcoal pellets are completed in this process.

[0022] [Rice husks, and rice husk charcoal] In the embodiments of this invention, rice husks refer to the outermost layer of the rice grain (paddy rice), also known as coarse bran, polished bran, rice bran, or simply rice husks. Rice husk charcoal is obtained through the aforementioned processes of "1. Charcoal burning (steaming)" and "2. Oxygen-deficient extinguishing." The size of the pores and medium pores of the rice husk charcoal is measured using the same method as for activated carbon. The amount of iodine and methylene blue adsorbed, which are used in the observation of activated carbon, can be identified and observed. [Table 2]

[0023] [Other embodiments] Although the pellet shapes described above are spherical and cylindrical, they are not necessarily limited to these shapes; they may also be elliptical or other shapes. Therefore, the pellet shape in this invention is not limited to spherical or cylindrical. Furthermore, the porous charcoal pellets for soil improvement may have beneficial bacteria that promote growth attached in spore form to the surface or to the micropores or pores of the carbon material, and these bacteria will be activated when scattered on soil suitable for growth. [Industrial applicability] The porous biomass pellets for soil improvement described above are primarily intended for soil improvement in paddy fields and cultivated fields. However, they are not limited to soil improvement in paddy fields and cultivated fields, and can be applied to landscaping, sewage treatment, etc. Therefore, the porous biomass pellets for soil improvement referred to in this invention are not necessarily limited to soil improvement.

Claims

1. A porous pellet is obtained by heating and gelatinizing a carbon material made from plant-derived biomass carbonized under oxygen-deficient conditions, a naturally derived sugar-based binder, mixing it with the carbon material, and then granulating and drying it. The carbon material has a water content of 4% or less, a pH of 7 to 8, and has fine pores of 1 to 2 nm and medium pores of 3 to 50 nm. The carbon material is rice husk charcoal, which is obtained by carbonizing rice husks to a carbon content of 30-50%. The carbohydrate binder is a naturally derived starch obtained from one or more selected from cassava starch, rice starch, corn starch, and wheat starch. The porous pellets create a bacteriostatic environment that promotes the dominance of beneficial bacteria in the soil and suppresses acid-causing pathogens. A porous biomass pellet for soil improvement characterized by the following features.

2. A method for producing porous biomass pellets for soil improvement according to claim 1, The porous pellets are prepared by mixing the rice husk charcoal and the carbohydrate-based binder in a paste solution obtained by heating water, granulating them into cylindrical pellets with an outer diameter of 4 to 6 mm, sun-drying them, and then performing a final drying at 60 to 90°C to achieve a moisture content of 4% or less. A method for producing porous biomass pellets for soil improvement, characterized by the following features.

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