Cement block, process for its preparation and its use as algal reef

Abstract

To provide a new base material usable as an algal reef.MEANS: To provide a cement block including a granule which contains a finely pulverized product of a lignocellulosic biomass raw material and yeast and has an acidic pH, a method for producing the cement block, and use of the cement block as an algal reef. According to the present invention, it is possible to provide a cement block which can be used as an algal reef, which has a small load on the natural environment, and which can promote favorable adhesion and growth of seaweed.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a cement block, its manufacturing method and its use as an algae reef. [Background technology]

[0002] In recent years, a phenomenon known as "isoyake" (barren seaweed beds) has been expanding along the coasts of Japan, where seaweed communities (seaweed beds) have significantly decreased or disappeared, leaving the area barren. Isoyake leads to the decline and poor growth of various seaweed root resources, including economically valuable species such as sea urchins, and there has been growing interest in preventing the spread of isoyake and in creating new seaweed beds that have disappeared. Seaweed bed creation is an important issue for the recovery of fishery resources and the maintenance of ecosystems, and there is particularly high hope for it as it could contribute to the promotion of blue carbon.

[0003] One of the technologies aimed at creating seaweed beds is the use of artificial reefs for creating seaweed beds, known as seaweed bed reefs or algae reefs. Traditionally, concrete algae reefs have been widely used due to their excellent stability and wave resistance, and the large surface area where seaweed grows. On the other hand, due to concerns about the environmental impact caused by the semi-permanent nature of concrete, algae reefs made from natural materials such as wood chips and wood combustion ash powder have also been proposed (for example, Patent Document 1 and Patent Document 2). Furthermore, artificial reefs have been proposed in which ready-mix concrete contains crushed biomass materials such as wood, rice straw, wheat straw, and rice husks as components (Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-239396 [Patent Document 2] Japanese Patent Application Publication No. 2023-172967 [Patent Document 3] Japanese Patent Application Publication No. 2019-058186 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a new substrate that can be used as a seaweed reef. [Means for solving the problem]

[0006] The present inventors have found that a cement block containing granules with an acidic pH, which contain finely pulverized lignocellulosic biomass raw material and yeast, has excellent properties as a seaweed reef.

[0007] The present disclosure provides the following inventions. Item 1. A cement block containing granules having an acidic pH, which contain finely ground lignocellulosic biomass raw material and yeast. Item 2. The cement block according to Item 1, wherein the pH of the granules is within the range of 2 to 6. Item 3. The cement block according to Item 1 or 2, wherein the granules further contain a binder. Item 4. The cement block according to Item 3, wherein the binder is starch or sodium alginate. Item 5. The cement block according to any one of Items 1 to 4, wherein the granules have a water-insoluble coating layer on the surface thereof. Item 6. The cement block according to Item 5, wherein the water-insoluble coating layer contains calcium alginate. Item 7. The cement block according to any one of Items 1 to 6, wherein the finely pulverized lignocellulosic biomass raw material has been subjected to a saccharification treatment. Item 8. The cement block according to any one of Items 1 to 7, wherein the finely ground lignocellulosic biomass raw material and the yeast are residues of ethanol fermentation. Item 9. The cement block according to any one of Items 1 to 8, for use as a seaweed reef. Item 10. A method for producing a cement block containing granules, comprising the steps of preparing granules from a mixture having an acidic pH and containing finely ground lignocellulosic biomass raw material and yeast, and hardening cement so as to contain the granules. Item 11. A method for growing marine plants, comprising the step of placing in the sea the cement block defined in any one of Items 1 to 9 or the cement block produced by the method defined in Item 10. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a cement block that can be used as a seaweed reef, which has a low impact on the natural environment and can promote good adhesion and growth of seaweed. [Brief explanation of the drawings]

[0009] [Figure 1] This is a graph showing the number of viable yeasts contained in granules (granulation Ia, molding Ia, granulation IIa, molding IIa) prepared from the ethanol fermentation residue (fermented wood flour) of finely ground lignocellulosic biomass raw material in a mortar block cured for two weeks. [Figure 2] 1 is a graph showing the change over time in the number of viable yeasts contained in granules (molded Ia, molded Ib, molded IIa, molded IIb) prepared from fermented wood flour in mortar blocks cured for 2 to 13 weeks. [Figure 3] 1 is a graph showing the change over time in the number of viable yeasts contained in fermented wood flour in a dry state or in a hydrated state. [Figure 4] This is a phenolphthalein-stained image (left) of the cross section of the mortar block after it was split and the granules were removed, and a schematic diagram of the carbonation that occurs around the granules inside the mortar block (right). [Figure 5] This is an image showing the arrangement of granules within fermented wood flour mortar specimens Ia5530 and IIb5530. [Figure 6] This is a surface image of fermented wood flour mortar specimen Ib5530 after 48 days of exposure in the sea (left image), and a cross-sectional image cut along the dotted line in the image (right image). [Figure 7] These are images of the appearance of plain mortar specimens N5520, N5540, N6530, and N6030, and fermented wood flour mortar specimens Ia5530, IIa5530, and IIb5530, after 159 days of exposure in the sea. [Figure 8] These are images of the appearance of plain mortar specimen N5530 and fermented wood flour mortar specimen Ib5530 after 159 days of exposure in the sea. [Figure 9] 1 is a graph showing the weight increase of each test specimen during the exposure test period. [Figure 10] This is an image of a cross section of fermented wood flour mortar specimen Ia5530, cut along the center line of three granules, after 216 days of exposure in the sea. [Figure 11] This is an image of a plate containing cultured microorganisms contained in the granules of fermented wood flour mortar specimen Ia5530 after 216 days of exposure in the sea. [Figure 12] 1 is a graph showing the relationship between the unit cement content of a mortar block and compressive strength. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following description may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments or specific examples. In this specification, a numerical range expressed using "~" or "-" means a range that includes the numerical values ​​at both ends as upper and lower limits, unless otherwise specified. The upper and lower limits of each numerical range exemplified in this specification can be combined in any way.

[0011] [Granules] The granules in the present invention are obtained by granulating a mixture (hereinafter also referred to as raw material mixture) having an acidic pH and containing finely pulverized lignocellulose biomass raw material (hereinafter also referred to as finely pulverized biomass raw material) and yeast.

[0012] The pulverized biomass material can be prepared by pulverizing a lignocellulosic biomass raw material. Lignocellulosic biomass raw material is a material containing wood fibers with a lignocellulose structure, such as tree trunks, bark, branches, roots, leaves, and stems. Examples of lignocellulosic biomass raw materials that can be used include lumber, unused wood generated during thinning and final felling, sawmill residues such as bark, backboards, and sawdust generated at sawmills, and construction waste wood generated at civil engineering construction sites and when dismantling wooden buildings.

[0013] There are no particular limitations on the type of tree used as a lignocellulosic biomass raw material. The tree may be a broad-leaved tree or a conifer, and examples thereof include birches (plants of the Betulaceae family, Betula platyphylla, Betula ermanii, Betula maximowicziana, etc.), umbellata (plants of the Lauraceae family, Betula umbellata, etc.), cedars (Cryptomeria japonica (a species of the Cupressaceae family, Cryptomeria japonica, endemic to Japan, which grows wild in Hokkaido, Honshu, Shikoku, Kyushu, Yakushima, etc., as well as T. plicata, Japanese cedar), willows (plants of the Salix family, Salicaceae, Weeping willow, White willow, Salix bako, Poplar, etc.), and Bayberry (Myrica myrica, Myricaceae). Examples of suitable trees include, but are not limited to, pine species (such as Abies sachalinensis, Pinus densiflora, Pinus blackensis, Pinus red pine, Pinus umbellata, Pinus luchuensis, and Pinus koraiensis), and yellowfin tuna species (Phellodendron amurense, Phellodendron amurense, Phellodendron obtusa, Phellodendron sieboldii, Phellodendron chinensis, and Phellodendron holly), etc.

[0014] Pulverization of lignocellulosic biomass raw materials can be carried out using means commonly used by those skilled in the art. For example, the lignocellulosic biomass raw materials are coarsely or mediumly crushed to a maximum diameter of about 0.5 mm to 10 mm using a commercially available crusher (coarse crusher or medium crusher) capable of crushing wood, such as a sawdust maker, roll crusher, cutter mill, or other machine, and then finely crushed using a dry grinder.

[0015] Dry mills include impact mills (e.g., hammer mills, pin mills, bead mills, etc.) that pulverize materials by applying impact with striking elements, pins, blades, etc., and jet mills (airflow impact mills) that generate jets of high-pressure air or gas to collide and pulverize materials. It is particularly preferable to use mills equipped with a screen or airflow classification mechanism that can recover finely pulverized materials of the desired size. An example of such a mill is the "Polvogene" airflow impact mill / classifier manufactured by Nara Machinery Manufacturing Co., Ltd. The airflow impact mill / classifier is a dry airflow impact mill equipped with a classifier, capable of reducing the particle size of millimeter-sized raw materials to the level of fine pulverization achieved by jet mills. Combining a highly efficient milling section with a separately powered classifier allows for a wide range of airflow volume adjustment, resulting in excellent temperature control of the raw materials and significantly improved pulverization efficiency of biomass raw materials. It also boasts superior hourly processing capacity compared to other dry pulverizers. It combines the characteristics of air classification and impact crushing, and has the advantage of generating less heat during crushing.

[0016] The pulverized biomass material may be surface-treated. Surface treatment refers to a treatment that breaks down the lignocellulose structure on the particle surface by friction and defibrates the particles without causing volumetric pulverization as much as possible.

[0017] The surface treatment can be carried out, for example, by suspending the finely pulverized material in an aqueous medium using a stone mill. The aqueous medium can be any water, such as pure water, distilled water, sterilized water, tap water, well water, or spring water, and may contain a pH adjuster or other additives. The aqueous medium can be used in an amount of about 1 to 20 times, preferably 2 to 15 times, and more preferably 5 to 10 times, the weight of the finely pulverized material.

[0018] A millstone grinder is a grinder that grinds materials by passing them through the gap between two paired grinding wheels (grinders), and an example of such a grinder is the "Supermass Colloider" (product name) manufactured by Masuko Sangyo Co., Ltd. The surface treatment of the finely ground material can be carried out by appropriately adjusting the operating conditions of the millstone grinder, such as the clearance between the grinding wheels, the rotational speed of the grinding wheels, and the number of repeated treatments (number of passes). Operating conditions include, for example, a grinder diameter of 4 to 8 inches, a clearance of 0.05 mm or less, preferably 0.01 mm or less, a rotational speed of 300 to 2500 rpm, preferably 500 to 2000 rpm, a load current of 3 to 5 A, and a number of passes of 1 or more, preferably 1 to 4.

[0019] The surface treatment destroys the lignocellulose structure on the particle surface of the pulverized biomass material, resulting in a defibrated state. This allows the cellulose and hemicellulose of the particles to be efficiently exposed to the aqueous medium, improving their decomposition efficiency. The surface treatment can be confirmed by observing the particle surfaces of the pulverized biomass material using a scanning electron microscope or other optical means.

[0020] Regardless of whether the pulverized biomass is surface-treated or not, the volume average diameter may be 250 μm or less, for example, 10 to 250 μm, preferably 20 to 200 μm, more preferably 30 to 150 μm, and even more preferably 40 to 110 μm.

[0021] The pulverized biomass product, whether surface-treated or not, may have a cumulative particle size distribution measured by laser diffraction with a volumetric d(10) of 4 to 15 μm, preferably 5 to 15 μm, and more preferably 6 to 14 μm, a d(50) of 15 to 80 μm, preferably 20 to 75 μm, and more preferably 30 to 70 μm, and a d(90) of 60 to 200 μm, preferably 65 to 150 μm, and more preferably 70 to 120 μm or less. The volumetric mode diameter measured by laser diffraction may be 15 to 80 μm, preferably 20 to 70 μm, and more preferably 30 to 65 μm.

[0022] In the present invention, the particle size distribution of the finely pulverized product is measured by laser diffraction. Measurements can be performed using commercially available particle size distribution measuring devices, such as Microtrac (trade name) from MicrotracBEL or Mastersizer (trade name) from Malvern Panalytical. When the particles contained in the measured finely pulverized product are accumulated in ascending order of particle size, the particle size at the point where the accumulated volume is 10% of the total volume is d(10), the particle size at the point where the accumulated volume is 50% of the total volume is d(50), and the particle size at the point where the accumulated volume is 90% of the total volume is d(90). In addition, the particle size with the highest occurrence rate in the volume-based frequency distribution is the mode diameter, and the arithmetic mean value of the volume-based particle diameters is the volume-average diameter.

[0023] The finely pulverized biomass material may be subjected to a saccharification treatment. Saccharification can be carried out by adding a saccharifying enzyme to a suspension of the finely pulverized material in an aqueous medium. The saccharifying enzyme may have cellulase activity, and preferably has hemicellulase activity. As the saccharifying enzyme, a commercially available enzyme preparation may be used, or an isolated and purified enzyme may be used, or a culture solution or extract of a microorganism that produces the saccharifying enzyme may be used. Examples of preferred saccharifying enzymes include commercially available cellulase preparations such as "Acremocellulase KM" and "Cellulase TP5-Kyowa" (both trade names) from Kyowa Kasei Co., Ltd., "Meicelase" (trade name) from Meiji Seika Pharma Co., Ltd., and "Sucrase C" (trade name) from Mitsubishi Chemical Corporation.

[0024] For the saccharification treatment, the finely pulverized suspension may be used as is, or an aqueous medium may be added to the finely pulverized suspension, or the aqueous medium may be removed by solid-liquid separation. In addition, a pH adjuster or other additives may be added to the finely pulverized suspension.

[0025] Saccharification can be carried out by adjusting reaction conditions such as the amount of enzyme added, reaction time, temperature, and pH to suit the saccharifying enzyme used. When using a commercially available cellulase preparation, the saccharification can be carried out according to the protocol recommended by the manufacturer. In one embodiment, saccharification is carried out by adding a saccharifying enzyme in an amount equivalent to 5 to 10% by mass of the finely pulverized material to an aqueous medium suspension containing 1 to 50% by mass, preferably 2 to 30% by mass, and more preferably 5 to 20% by mass of the finely pulverized material and having a pH of 4 to 7, and allowing the reaction to proceed with stirring at a temperature of 30°C to 60°C.

[0026] The saccharification process hydrolyzes the pulverized biomass. When saccharification is complete, cellulose is ultimately converted into glucose, and hemicellulose is ultimately converted into the constituent sugars of hemicellulose, such as xylose and mannose. In saccharification, complete saccharification is not essential; partial saccharification is acceptable.

[0027] The yeast used in the present invention preferably has the ability to metabolize sugars derived from lignocellulosic biomass feedstocks. As such yeast, baker's yeast or brewer's yeast is preferably used, and various strains can be used, such as dry yeast for bread making, "Kyokai Yeast" (registered trademark), which is a brewer's yeast distributed by the Brewing Society of Japan, and strains preserved in the Microorganism Bank.

[0028] The amount of yeast contained in the raw material mixture can be determined depending on the type of yeast, other components contained in the raw material mixture, the pH of the raw material mixture, and other conditions. The yeast content is, for example, 1 × 10 per 1 g of finely pulverized biomass. 2 cfu or more, preferably 1 x 10 per gram of finely ground biomass 3 cfu or more, preferably 1 x 10 4 There is no upper limit to the yeast content, and for example, 1 × 10 per 1 g of finely ground biomass. 10 less than cfu, 1×10 9 cfu or less, or 1 x 10 8The colony forming unit (cfu) can be calculated from the number of colonies formed when a suspension of a test sample containing yeast is diluted to an appropriate dilution ratio and inoculated onto a solid medium commonly used for culturing yeast, such as potato dextrose agar medium, and cultured.

[0029] The raw material mixture has an acidic pH. The pH of the raw material mixture is, for example, within the range of 2 to 6, preferably within the range of 2.5 to 5.5, more preferably within the range of 3 to 5, and even more preferably within the range of 3.5 to 4.5. The pH of the raw material mixture can be adjusted by adding a pH adjuster, for example, an acidic substance such as an organic acid. The pH of the raw material mixture can be measured using an aqueous suspension of the raw material mixture.

[0030] The moisture content of the raw material mixture may be such that subsequent granulation is possible. Furthermore, to improve granulation properties, the raw material mixture may further contain a binder. The binder may be any binder capable of binding the raw material mixture, and is preferably a biodegradable binder. Examples of binders include starch, sodium alginate, gelatin, agarose, gellan gum, and guar gum. Preferred binders are starch or sodium alginate.

[0031] The raw material mixture can be prepared by, for example, mixing finely ground biomass and yeast, optionally adding a pH adjuster and a binder, etc. The raw material mixture may further contain nutrients for better growth and attachment of marine plants.

[0032] The raw material mixture can also be prepared using ethanol fermentation residues of saccharified finely pulverized biomass. The finely pulverized biomass contained in the fermentation residues has a large specific surface area and improved nutrient adsorption capacity due to the partially destroyed and decomposed lignocellulose structure. In particular, the residues of ethanol fermentation using yeast have the advantage that they can be used as a raw material mixture as they are, since they are a mixture of finely pulverized biomass and yeast. When using ethanol fermentation residues without yeast or with a low yeast content as a raw material mixture, yeast can be added as needed.

[0033] Ethanol fermentation is carried out by adding a microorganism capable of producing ethanol from sugars, preferably yeast used in brewing or bread making, to a suspension of finely ground biomass after saccharification. Examples of yeast used for ethanol fermentation are the yeasts exemplified above.

[0034] Ethanol fermentation can be carried out under conditions suitable for the microorganisms used by adjusting, for example, the amount of microorganism added, fermentation time, temperature, pH, aeration rate, stirring, etc. Methods for ethanol fermentation using microorganisms from saccharified lignocellulosic biomass feedstocks are known to those skilled in the art, and these known methods can be used for the ethanol fermentation in the present invention.

[0035] Ethanol fermentation may be carried out in parallel with saccharification, a process known as multiple parallel fermentation. Multiple parallel fermentation may be carried out by simultaneously adding a saccharifying enzyme and a microorganism for ethanol fermentation to a suspension of finely pulverized biomass. However, it is preferable to first carry out saccharification under conditions suitable for saccharification, and then, without performing any special operations to terminate saccharification, modify the conditions as necessary to be suitable for ethanol fermentation, and then add the microorganisms to carry out ethanol fermentation. In one embodiment, an aqueous medium suspension containing 1 to 50% by mass, preferably 2 to 30% by mass, and more preferably 5 to 20% by mass of the finely pulverized material and having a pH of 4 to 7 is subjected to saccharification treatment with stirring at 30 to 60°C for 12 to 60 hours, after which 0.5 to 5% by mass of dry yeast is added to the suspension, and multiple parallel fermentation is carried out at 40 to 50°C for 3 to 10 days.

[0036] The ethanol fermentation residue can be recovered from the suspension after ethanol fermentation by solid-liquid separation such as filtration, centrifugation, decantation, etc. The ethanol fermentation residue can be used after drying by an appropriate means so that the moisture content (mass ratio of water to dry mass) is about 10% or less.

[0037] It is preferable to use the ethanol fermentation residue as a raw material mixture with the fermentation liquor attached, as this brings acidic substances such as organic acids and nutrients from the fermentation liquor into the raw material mixture, reducing or eliminating the need for pH adjusters, and enhancing the nutrients necessary for the attachment and growth of marine plants.

[0038] The granules in the present invention are prepared by granulating a raw material mixture. From the viewpoint of yeast viability, granulation is preferably carried out by a method that does not involve heat treatment, and can be carried out, for example, by putting the raw material mixture into a mold and applying pressure. Granules may also be prepared by first preparing large granules and then shredding or crushing them to the desired size.

[0039] The shape of the granules is not limited, and is preferably rectangular or spherical. The size of the granules is such that the longest side of the granules is 10 mm or more if the shape is rectangular, or the longest diameter of the granules is 10 mm or more if the shape is spherical or other. The size of the granules may be, for example, 15 mm or more, 20 mm or more, 25 mm or more, 30 mm or more, 40 mm or more, or 50 mm or more, and may be 100 mm or less, 90 mm or less, 80 mm or less, 70 mm or less, or 60 mm or less. In one embodiment, the granules are approximately rectangular, with the longest side measuring 20 mm to 30 mm square. In another embodiment, the granules are approximately spherical, with a diameter of 20 mm to 30 mm.

[0040] The granules may have a water-insoluble coating layer on their surface. The water-insoluble coating layer preferably contains calcium alginate. The calcium alginate coating can be achieved by immersing the granules successively in an aqueous sodium alginate solution and an aqueous calcium chloride solution. The coating layer may further contain nutrients for better attachment and growth of marine plants.

[0041] [Cement Block] The cement block of the present invention is a block formed by hardening cement and contains granules therein. The raw materials for the cement block preferably include aggregate in addition to cement. The cement block is preferably a mortar block formed from mortar or a concrete block formed from concrete, more preferably a mortar block.

[0042] Examples of cement used in the production of cement blocks include Portland cement (ordinary Portland cement, high-early-strength Portland cement, etc.), blended cement (blast-furnace cement, fly ash cement, etc.), ecocement, and special cement. There are no limitations on the aggregate used in the production of cement blocks; for example, sand can be used as fine aggregate for mortar blocks, and gravel can be used as coarse aggregate and sand as fine aggregate for concrete blocks. Cement blocks may contain other components such as additives.

[0043] The shape of the cement block is not limited, and may be, for example, rectangular or flat. The size of the cement block is also not limited, and may be adjusted appropriately depending on the number and size of the granules to be contained therein, the installation location, etc. In one embodiment, the cement block has a length of 10 cm to 50 cm, a width of 10 cm to 50 cm, and a height of 5 cm to 10 cm, and has a generally flat shape.

[0044] Cement blocks do not require the strength required for civil engineering and architectural structures; they only need to be strong enough to withstand the stresses of manufacturing, distribution, and installation. The strength of a cement block can be adjusted by changing conditions such as the type of cement used, the type of aggregate, the water-cement ratio, and the aggregate-cement ratio. For example, when using ordinary Portland cement, cement blocks can be prepared with a water-cement ratio (W / C) in the range of 0.5 to 2.5 and an aggregate-cement ratio (S / C) in the range of 1 to 20.

[0045] The cement block contains one or more granules. When multiple granules are contained, not all of them need to be contained within the block, and some of the granules may be exposed on the surface of the cement block. Furthermore, there are no limitations on the arrangement of the multiple granules within the cement block, and they may be uniformly or unevenly arranged. The distance from the block surface to the granule surface may be adjusted appropriately depending on how quickly the block is desired to erode. By shortening the distance from the block surface to the granule surface, for example to about 1 to 10 mm, it is expected that block erosion and the resulting exposure of the granules will occur more quickly.

[0046] The volume ratio of the granules to the total volume of the cement block is not limited as long as the cement block maintains a strength sufficient to prevent it from easily collapsing during production, distribution, and installation, and is, for example, 1 to 60%, preferably 3 to 40%, and more preferably 5 to 20%.

[0047] Cement blocks can be prepared by pouring cement into a formwork, placing granules in place, pouring more cement on top of that, vibrating the mixture to remove any air bubbles, and then curing the mixture.

[0048] [Use as a seaweed reef] The cement block of the present invention can be used as a seaweed reef. The mechanism of action is presumed to be as follows, but is not limited to this.

[0049] When cement blocks are placed underwater, seawater penetrates the block, and the highly alkaline water in the cement penetrates the granules. Because the granules are acidic, neutralization lowers the pH of the cement around the granules, resulting in insufficient hydration, making them weak and susceptible to seawater erosion. The highly alkaline water also provides moisture to the yeast within the granules. Because the granules are acidic, neutralization mitigates the effects of high alkalinity. The supplied moisture activates the yeast, which grows using the finely ground biomass and other nutrients within the granules as a nutrient source. Carbon dioxide produced by the yeast also contributes to the weakening of the cement. The finely ground biomass contained in the granules acts as a carrier for moisture and nutrients and as a nutrient source for the yeast. When the cement block erodes, the granules are exposed and come into contact with seawater, releasing the yeast and other nutrients contained within, promoting the settlement and growth of marine organisms.

[0050] Since the above-mentioned erosion occurs gradually over time in the sea, the cement block of the present invention is expected to have the long-term function of promoting the settlement and growth of marine plants. The cement block of the present invention, which has the property of gradually eroding over time (auto-substrate renewal ability), has the advantage of placing less strain on the natural environment because it will eventually disappear.

[0051] The cement block may be used by suspending it in the water using a rope or other mooring means, or by sinking it to the seabed as is or by connecting it to a suitable weight or the like.

[0052] Marine plants that are expected to attach and grow on algal reefs using cement blocks are marine plants that can form seaweed beds, such as seaweed and seagrass. Examples of seaweed include brown algae such as kelp, wakame, hijiki, mozuku, Sargassum, and Amaran, and red algae such as Acabra ginnansou, Gracilaria, Porphyra, and Gelidium. An example of seagrass is Zostera marina. By incorporating marine plant zoospores or seeds within the cement blocks, preferably within the granules, marine plants that do not exist in the sea area where the blocks are installed can attach and grow.

[0053] The present invention will be specifically explained below by showing examples. However, these examples are intended to aid in understanding the present invention and are not intended to limit the technical scope of the present invention. [Example]

[0054] Example 1: Production of mortar blocks using finely ground birch as a raw material and evaluation of the yeast count (1) Preparation of wood flour The bark-removed birch logs were dried for one week in a constant temperature and humidity chamber (Espec) at a temperature of 25°C and a humidity of 20%, then chipped and crushed for 30 seconds in a rotary crusher (Sansho Industry NR-04A). The chips were then passed through a sieve (mesh 50) to collect the crushed material with a diameter of less than 300 μm.

[0055] An airflow impact crushing and classifying device (Nara Machinery Manufacturing, Polvogene PG-3) was used, with a crushing rotation speed of 8000 min -1 , Grinding current value: 15~17A, Classifier rotation speed: 6000 min -1 , Classification current value: 1 to 1.5A, Suction air volume: 4m 3 The above pulverized material was dry-pulverized under the conditions of a feed rate of 3 kg / min and a raw material supply rate of 3 kg / hr, and the finely pulverized material was recovered.

[0056] (2) Surface treatment A suspension prepared by mixing 2.5 kg of the finely pulverized material prepared in (1) with 12.5 L of water (weight ratio 1:5) was processed using a stone mill (Masuko Sangyo Co., Ltd., Supermass Colloider MKCA6-3INV) under conditions of a clearance of 0.01 mm, a rotation speed of 1000 rpm, and a current value of 3.7 A (tentative test conditions). The passed suspension was further processed under conditions of a clearance of <0.01 mm, a rotation speed of 1500 rpm, and a current value of 3.9 A (main test conditions), and the passed suspension of the finely pulverized material was collected.

[0057] The particle size distribution of wood flour samples before, after, and after surface treatment (preliminary and final tests) was measured using a laser diffraction / scattering particle size analyzer, MT-3300EXII (MicrotracBEL). Surface treatment did not significantly alter the particle size or size distribution of the wood flour. For all wood flour samples, the d(10) was within the range of 11.00–13.00 μm, the d(50) was within the range of 33.93–62.00 μm, and the d(90) was within the range of 95.96–104.7 μm. The mode diameter was within the range of 35.38–59.89 μm, and the volume mean particle size (MV) was within the range of 50.34–103.2 μm. The surface layer of the wood flour samples after surface treatment was destroyed.

[0058] (3) Saccharification and fermentation The entire wood flour suspension obtained in (2) was transferred to a 30 L culture vessel, and 300 g of Acremocellulase KM (Kyowa Kasei Co., Ltd.), an enzyme preparation with cellulase and hemicellulase activity, was added. Saccharification was performed by incubating at 50°C with stirring. Two days after the start of treatment, the temperature of the fermentation vessel was lowered to 45°C, and 100 g of dry yeast (Oriental Yeast) was added. The mixture was then incubated for an additional 5.5 days to perform parallel multiple fermentation. After fermentation was complete, the culture was separated into solid and liquid by filtration using a medium-sized strainer bag, and the solids were recovered and freeze-dried to yield 2.8 kg of fermented wood flour.

[0059] The moisture content of the dried fermented wood flour was 6.43%. Furthermore, when 1 g of dried fermented wood flour was placed in a beaker containing 100 ml of distilled water and stirred with a stirrer, the pH was measured, which showed a value of approximately 4. The fermented wood flour contained finely ground biomass and yeast, and also contained components derived from the fermentation liquid that was carried over because no washing procedure was performed after solid-liquid separation. The analysis results of the nutrients contained in the wood flour before and after saccharification and fermentation are shown in Table 1. [Table 1]

[0060] (4) Preparation of granules 100 g of fermented wood flour (3) was mixed with 325-350 ml of a 1.0 wt% aqueous solution of starch (Hokuren potato starch, Hokuren), and then filled into an ice cube tray as a mold to prepare rectangular granules (hereinafter referred to as granules Ia in the examples). 100 g of fermented wood flour (3) was mixed with 200 ml of a 1.0 wt% aqueous solution of sodium alginate (Wako Pure Chemical Industries, Ltd. 191-099965 Sodium Alginate 500-600 (500-600 cPs), Fujifilm Wako Pure Chemical Industries, Ltd.), and then manually rolled into spherical granules (hereinafter referred to as granules IIa in the examples).

[0061] Furthermore, granules Ia and IIa were immersed in the aforementioned sodium alginate aqueous solution for a few seconds, then transferred to a 2.5 wt% calcium chloride aqueous solution and immersed for 5 minutes to form insoluble calcium alginate, and then dried for 5 days to prepare granules coated with calcium alginate (hereinafter referred to as Molded Ia and Molded IIa, respectively, in the examples).

[0062] In addition, in the preparation process of molding Ia and molding IIa, granules were separately prepared by freezing and storing them at −20 to −16° C. after calcium alginate formation and before drying (hereinafter referred to as molding Ib and molding IIb, respectively, in the examples).

[0063] (5) Manufacturing of mortar blocks Mortar was prepared by blending ordinary Portland cement with water and river sand as fine aggregate, with a water-to-cement ratio (W / C) of 0.55 and a sand-to-cement ratio (S / C) of 3.0. Half of the mortar was poured into a mold measuring 160 mm long x 40 mm wide x 40 mm high. Eight pieces of either Granule Ia, Molded Ia, or Molded Ib, prepared in (4), or ten pieces of Granule IIa, Molded IIa, or Molded IIb, were placed at approximately equal intervals at least 5 mm from the mold. The remaining half of the mortar was poured into the mold and compacted. After a curing period of 2 to 13 weeks, the blocks were split open to remove the granules, and the yeast counts were evaluated.

[0064] (6) Evaluation of yeast count in mortar blocks Approximately 5 g of the crushed granules removed from the mortar block and 100 ml of sterilized saline were placed in a homogenizing bag and suspended, then the suspension was applied to the surface of potato dextrose agar medium at an appropriate dilution ratio and cultured for 5 days in an incubator set at 25°C. The number of colonies that appeared was counted and used as the yeast count per gram of granules. The number of colonies was also counted in the same way for the granules before embedding them in the mortar, and this was used as the yeast count at week 0.

[0065] The yeast count of the dried fermented wood flour prepared in (3) was 4.0 × 10, the average of four tests. 3 cfu / g. Based on this value, the yeast counts in the mortar blocks after two weeks of curing for Granulation Ia, Molded Ia, Granulation IIa, and Molded IIa are shown in Figure 1. For both Granulation Ia and Molded Ia, which used starch as a binder, the yeast count increased by approximately 100-fold after two weeks in the mortar blocks. Furthermore, for Granulation IIa and Molded IIa, which used sodium alginate as a binder, the yeast count before embedding in the mortar was lower than for Granulation Ia and Molded Ia, but after two weeks the yeast count increased by 100-1000-fold.

[0066] Figure 2 shows the time-dependent changes in yeast counts in the mortar blocks for Forms Ia, Ib, IIa, and IIb. Due to experimental limitations, measurements for Form Ib were limited to four weeks. Similar to the results shown in Figure 1, the yeast count increased within two weeks, but remained largely unchanged over the following 13 weeks. The low yeast counts for Forms Ia and IIb after four weeks and for Form IIb after 10 weeks are presumably due to individual differences in the granules. Furthermore, no significant differences were observed between Forms Ia and Ib, or between Forms IIa and IIb, indicating that frozen storage of fermented wood flour had no effect on the yeast count.

[0067] In previous studies, when fermented wood flour was mixed in powder form into mortar, the yeast died.

[0068] (7) Evaluation of yeast numbers in fermented wood flour To investigate the effect of moisture in fermented wood flour on the number of yeast cells, the fermented wood flour prepared in (3) was stored in an incubator at 25°C for two weeks, either dry or fully hydrated. One gram of fermented wood flour from 0, 1, or 2 weeks after storage was placed in a homogenizing bag and suspended in 100 ml of sterilized saline. The suspension was then applied to the surface of potato dextrose agar medium at an appropriate dilution ratio and cultured for five days in an incubator set at 25°C, after which the number of colonies that appeared was counted.

[0069] The yeast count of the dried fermented wood flour prepared in (3) (4.0 × 10 3 Figure 3 shows the change in yeast count over time in dry and hydrated fermented wood flour, based on cfu / g. There was almost no change in yeast count in fermented wood flour stored in a dry state. On the other hand, in fermented wood flour that had been moistened, the yeast count increased by approximately 10,000 times in one week. These results indicate that supplying moisture to fermented wood flour activates the yeast and promotes its proliferation.

[0070] (8) Evaluation of pH around the granules The left side of Figure 4 shows a cross-sectional photograph of the mortar block produced in (5) after splitting it and removing the granules (molded IIa or IIb) from the spherical depressions. The area within about 5 mm of the granules was uncolored, but the rest of the area was colored reddish purple. Since the color range of phenolphthalein is approximately pH 8-10, it was confirmed that the alkalinity of the mortar was neutralized around the granules.

[0071] The results of Example 1 showed that when water penetrates into the granules embedded in the mortar and makes them moist, the acid derived from the fermented wood flour neutralizes the alkalinity of the surrounding mortar, making the pH at which yeast can survive. The penetrated water also activates and multiplies the yeast, allowing it to survive for at least 13 weeks.

[0072] [Example 2] Evaluation of the usability of mortar blocks as algae reefs Mortar was prepared by mixing ordinary Portland cement with water and river sand as fine aggregate, and poured into a formwork with internal dimensions of 160 mm length x 136 mm width x 40 mm height. After compaction, the mortar was cured for two weeks to prepare the nine types of mortar blocks shown in Table 2 as test specimens. The compressive strength of the specimens was measured in accordance with JIS A1108:2018 "Test method for compressive strength of concrete." [Table 2]

[0073] Specimens N5520, N5530, N5540, N6530, and N6030 are comparative mortar blocks without granules embedded therein (collectively referred to as plain mortar specimens in the examples). Specimens Ia5530, Ib5530, IIa5530, and IIb5530 are mortar blocks of the present invention (collectively referred to as fermented wood flour mortar specimens in the examples). After half of the mortar was poured into a mold, eight pieces of either molded Ia or molded Ib prepared in Example 1 (4), or ten pieces of either molded IIa or molded IIb, were placed at approximately equal intervals at a position about 5 mm or more away from the mold (FIG. 5). The remaining half of the mortar was poured in and then compacted. For specimens Ia5530 and Ib5530, the volume ratio of the granules to the entire block was approximately 10%, and for specimens IIa5530 and IIb5530, the volume ratio of the granules to the entire block was approximately 14%.The dimensions of both specimens were approximately 160mm x 135mm x 40mm.

[0074] An exposure test to examine the algae growth status of the above mortar specimens was conducted at the F quay of Hakodate Dock Co., Ltd.'s Hakodate Shipyard in Hakodate, Hokkaido, by immersing them in the sea. One fermented wood flour mortar specimen and one plain mortar specimen were hung from a rope, spaced approximately 1 m apart, and placed alternately 1.8 m from the quay. The hanging depth was set at 170 cm above the tide table datum for the fermented wood flour mortar specimens and 270 cm for the plain mortar specimens to prevent adjacent specimens from colliding with each other due to wave action. The exposure test began on September 14, 2023.

[0075] By the 48th day of exposure (November 1, 2023), small algae were observed on the surface of most specimens, but no significant differences were observed. The surface of specimen Ib5530 is shown in Figure 6 (left), and an image of a cross section taken along the dotted line in Figure 6 (right) is shown. Holes of approximately 5–10 mm were observed in the circled areas in the figure. These holes are presumably formed by seawater erosion, resulting from insufficient hydration of the mortar due to the acidity of the granules. Furthermore, the fermented wood flour mortar specimens exhibited less Ca(OH)2 leaching, which indicates a higher alkalinity than the plain mortar specimens, suggesting that they are more susceptible to algae growth. On the other hand, no chipping or peeling was observed on the surface of the plain mortar specimens, and within the scope of this experiment, no difference in durability was observed due to the difference in composition.

[0076] Figures 7 and 8 show external images of each specimen on the 159th day of exposure (February 20, 2024). All specimens except N6530 had kelp growing on them, but while the plain mortar specimen had only a few kelp strands, the fermented wood flour mortar specimen had more kelp in number and length than the plain mortar specimen, with many kelp strands over 50 cm in length observed. N6530 had no kelp growing on it at all, and instead had a different organism with a high moisture content attached to it.

[0077] The weight gain of the specimens during the exposure test is shown in Figure 9. Considering that organisms other than kelp had attached to N6530, and that the fermented wood flour mortar specimen was measured lower than its actual weight because the entire specimen, including the kelp, could not be placed on the scale, it was shown that the fermented wood flour mortar specimen had a better effect on the attachment and growth of kelp than the plain mortar specimen.

[0078] On the 216th day of exposure (April 17, 2024), specimen Ib5530 was wet cut with a band saw along the longitudinal axis of the specimen, with the largest surface facing downwards, so as to pass through the center lines of the three outermost granules (referred to as the upper left, center left, and lower left, respectively) (FIG. 10). Each granule was scraped out from the cut surface using a medicine spoon, its mass was measured, and the number of yeast cells in the granules was counted in the same manner as in Example 1(6).

[0079] An image of the potato dextrose agar medium after cultivation is shown in Figure 11, and the number of yeast cells in each granule is shown in Table 3. Despite all granules having been exposed to the seawater for a long period of approximately 7 months, the survival of yeast cells was confirmed. [Table 3]

[0080] [Test Example 1: Basic test for substrate development] To investigate the relationship between the composition of mortar and compressive strength, nine types of mortar blocks shown in Table 4 were prepared as test specimens. All of these mortar blocks had no granules embedded inside, and were prepared in the same manner as in Example 2, and their compressive strengths were measured. [Table 4]

[0081] The results are shown in Figure 12. It was confirmed that there was a positive correlation between the unit cement content of the specimens and the average compressive strength. This indicates that it is possible to adjust the desired low-strength mortar block by changing the raw material composition of the mortar and adjusting the unit cement content.

Claims

1. A cement block containing granules having an acidic pH, which contain finely ground lignocellulosic biomass raw material and yeast.

2. 2. The cement block according to claim 1, wherein the pH of the granules is in the range of 2 to 6.

3. The cement block of claim 1 , wherein the granules further comprise a binder.

4. 4. The cement block of claim 3, wherein the binder is starch or sodium alginate.

5. 2. The cement block according to claim 1, wherein the granules have a water-insoluble coating layer on the surface thereof.

6. 6. The cement block of claim 5, wherein the water-insoluble coating layer comprises calcium alginate.

7. 2. The cement block according to claim 1, wherein the finely pulverized lignocellulosic biomass raw material has been subjected to a saccharification treatment.

8. The cement block according to claim 1, wherein the finely ground lignocellulosic biomass raw material and the yeast are residues of ethanol fermentation.

9. 10. The cement block of claim 1 for use as a seaweed reef.

10. A method for producing a cement block containing granules, comprising the steps of: preparing granules from a mixture having an acidic pH, which mixture contains finely ground lignocellulosic biomass raw material and yeast; and hardening cement so as to contain the granules.

11. A method for growing marine plants, comprising the step of placing in the sea a cement block as defined in any one of claims 1 to 9 or a cement block produced by the method as defined in claim 10.

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