Cellulosic biogel growing media

Abstract

A method for preparing a soil-less growing media includes a step of combining cellulose-based fibers with sizes from macro-scale to nano-scale and crosslinking agents, including, for example, inorganic salts representing macro- and / or micro-nutrients of a plant, to form a biogel and a step of incubating the biogel until the biogel solidifies when the cellulose fibers and the crosslinking agent crosslink to obtain the soil-free growing media.

Description

CELLULOSIC BIOGEL GROWING MEDIACROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Patent Application No. 63 / 554,101 filed on February 15, 2024. The entire contents of this application are hereby incorporated by reference.BACKGROUND OF THE INVENTION1. Field of the Invention

[0002] The present invention is related to cellulosic biogel or hydrogel substrates that can be used as sustainable alternatives to replace conventional growing media, such as soil, peat, coir, wood fibers and wood chips, coconut fibers, wools, rice hulls, etc. The present invention addresses challenges in current agricultural and horticultural practices by providing high- performance substrates with high water contents that support effective plant growth, while promoting environmental sustainability.2. Description of the Related Art

[0003] Peat, a widely used natural but non-renewable material, has found extensive usage in both agricultural and horticultural applications. Its popularity stems from the fibrous structure with high porosity enabling moisture retention, and from the ability to increase acidity. Peat is commonly integrated into agricultural blends and potting soils, as amendments for lawn and garden soils, and is also used in turf maintenance on golf courses to improve the water holding capacity and reduce overall weight. Despite its versatile utility, concerns have arisen regarding the carbon-intensity associated with peat extraction, posing a significant threat to the delicate peat bog ecosystems. The extraction process has various environmental consequences, including surface water eutrophication, release of pollutants such as metals and carbon dioxide (CO?) causing air pollution, and disruption of wildlife habitats. Preceding peat extraction, it is essential to lower the water table to dry the surface of the peatland, leading to increasing peat decay, particularly in the upper layers, and the release of more CO? into the atmosphere. This reduction in water supply could result in fundamental or irreversible changes in the ecology. Consequently, there is a growing inclination to preserve peatlands and minimizetheir primary uses, especially in agriculture, forestry, and peat extraction for fuel and other commercial applications. This shift aims to ensure the sustainability of these ecosystems, recognizing the need for responsible practices to mitigate the environmental impact associated with peat extraction.

[0004] Numerous alternatives to peat have been proposed, including coir, wood fibers, wood chips, coconut fibers, wools, sands, and rice hulls. However, none of these substitutes has proven ideal for plant growth due to several drawbacks. For instance, wood fibers and wood chips struggle to store sufficient water or nutrients, while soil, although rich in iron, has limitations in nutrient retention. Coir, compared to peat, offers better water retention but a greater volume of air space. The addition of rice husks can enhance water permeability in growing media but falls short in retaining significant volumes of water or nutrients. Addressing these challenges is crucial to developing a viable and sustainable alternative to peat or other peat alternatives in the realm of plant growth and cultivation.

[0005] As a result, there is an increasing demand for sustainable substitutes for peat or peat-based growing materials. These substitutes must deliver the desired properties of high- performance growing media, while minimizing environmental impact. Such alternatives are essential to address the ecological concerns associated with peat extraction and to support the transition to environmentally sustainable agricultural and horticultural practices.SUMMARY OF THE INVENTION

[0006] The example embodiments of the present invention address the above-discussed challenges by providing a cellulosic growing medium derived from plant biomasses and other natural organic wastes. This growing medium incorporates a blend of cellulose in macro-, micro-, and nano sizes (i.e., 1 nm-100 nm, 100 nm-5,000 nm, and greater than 5,000 nm), crosslinked with different salts representing the macro- and micro-nutrients of a plant. The manufacturing process can involve combining carboxylated cellulose derived from a lignocellulosic feedstock (e.g., woody and no-woody plants) and agricultural residues or natural fibers to create a fibrous mixture with a desired blending ratio. The mixture is then crosslinked with different ions (including monovalent, divalent, and trivalent), chosen from macro- and micro-nutrients, at ambient or room temperature. Following the crosslinking reaction, themixture undergoes incubation for about 1 min up to about 100 days to produce the biogel or hydrogel growing medium. The resulting biogel has a water content of about 90%-about 99% or more, a maximum dry bulk density of approximately 0.0083 g / cm3-approximately 0.0086 g / cm3, and a maximum wet bulk density close to about 1.0 g / cm3depending on the specific formulation used. This biogel composition is suitable as a standalone growing medium and can also be used as an additive, binding- and wetting-agent to peat-based or soilless substrate (e.g., coir, wood fibers and wood chips, coconut fibers, wools, rice hulls) growing media with superior properties than unmodified substrates without the biogel composition. This innovative biogel growing medium offers the versatility to replace peat as a standalone medium or as a blending agent to enhance the properties of known substrates, such as bark and wood fibers or chips, composted pine bark, perlite, vermiculite, sand, rock wool, compost, animal manure, rice hulls, hardwood bark, softwood bark, coir, and similar elements.

[0007] In one example embodiment, a method for preparing a soil-free growing media includes, as shown at (a) in Fig. 1, combining macro-, micro- to nano-scale cellulosic fibers and a crosslinking agent to form a biogel; and, as shown at (b) in Fig. 1, incubating the biogel until the biogel solidifies when the cellulose fibers and the crosslinking agent crosslink to obtain the soil- free growing media.

[0008] The biogel can solidify when a surface charge of the cellulose fibers is partially or fully neutralized with the crosslinking agent. The step (b) of incubating the biogel can performed for about 1 min-about 100 hours at room temperature. The soil-free growing media can have a water holding capacity of about 1%-about 99% or more.

[0009] The cellulose fibers are obtained from lignocellulosic biomass feedstocks and / or natural organic wastes. The biomass feedstocks can be derived from woody and non-woody plants. The biomass feedstocks can be derived from jute, palm trees, sugarcane bagasse, corn, wheat, oats, rice, sorghum, oil palm, bamboo, spinifex, coastal bermudagrass, miscanthus, switchgrass, azolla, seaweeds, flax, hemp, ramie, kenaf stalk fiber, kenaf core, abaca, sisal, pineapple, banana leaf, banana peel, banana fiber, curaua, lotus leaf stalk, roselle, seed hair fiber, cotton fiber, kapok fiber, areca nut fiber, coconut, potato, cabbage, tomato, rubberwood, Indian screw tree, achira fiber, citrus, soybean, soybean straw, spent grain, soy hull, pea hull,grape pomace, fruit pomace, or combinations thereof. In yet another aspect, the biomass feedstocks are derived from bacteria, algae, tunicate, and combinations thereof.

[0010] The natural organic wastes can include food waste, such as green waste, fruits and vegetable wastes, meat and fish wastes (including bones), food-soiled paper, non-hazardous wood waste, landscape waste, and other sources of waste products of organic origin.

[0011] The crosslinking agent can be at least one inorganic salt and / or at least one crosslinking molecular compound.

[0012] The at least one inorganic salt can be selected from sodium (Na)-, potassium (K)-, calcium (Ca)-, magnesium (Mg)-, iron (Fe)-, aluminum (Al)-, manganese (Mn)-, zinc (Zn)-, copper (Cu)-, molybdenum (Mo)-, nitrogen (N)-, phosphorus (P)-, sulfur (S)-, boron (B)-, nickel (Ni)- based salt ions, and combinations thereof.

[0013] The crosslinking agent can include at least one crosslinking molecular compound selected from genipin, polydopamine, lignosulfonate, chitosan, glutaraldehyde, citric acid, and polyvinyl alcohol.

[0014] Step (a) can include a growing medium including cellulose in the range of about 0.01 wt% to about 99.99 wt% combined with a salt solution in the concentration range of about 1 mmol to about 1000 mmol. The growing medium can include about 0.01 wt% to about 40 wt% cellulose and about 40 wt% to about 100 wt% cellulose components including cellulose nanofibers, cellulose nanocrystals, tunicate cellulose, bacterial cellulose, or amalgamations thereof.

[0015] The cellulose fibers can have a degree of oxidation (DO) between about 0.5 mmol / g and about 3.0 mmol / g, and more specifically the cellulose fibers can have a DO from about 0.8 mmol to about 2.0 mmol of COOH per gram of oxidized cellulose fibers.

[0016] The biogel can further include lignin, hemicellulose, holocellulose, proteins, fatty acids, or combinations thereof.

[0017] The method can further include step (c) in Fig. 1 wherein the biogel is infused with air bubbles or nanobubbles.

[0018] Step (a) of forming the biogel can further include combining at least one cellulose- fiber derivative, which can be carboxylated cellulose fibers and / or sulfonated cellulose fibers.

[0019] An example embodiment of the present inventions includes a method of growing plants comprising planting seeds or plants in a soil-free growing media made by one of the various other example embodiments of the present invention.

[0020] An example embodiment of the present inventions includes a soil-free growing media made by one of the various other example embodiments of the present invention.

[0021] According to an example embodiment of the present invention, a soil-free growing media includes a solidified biogel including cellulose fibers that are macro-, micro- and / or nanoscale (i.e., 1 nm-100 nm, 100 nm-5,000 nm, and greater than 5,000 nm) and a crosslinking agent. The cellulose fibers and the crosslinking agent are crosslinked.

[0022] A surface charge of the cellulose fibers can be partially or fully neutralized with the crosslinking agent. The soil-free growing media can have a water holding capacity of approximately 1%-approximately 99% or more. The at least one inorganic salt can be selected from sodium (Na)-, potassium (K)-, calcium (Ca)-, magnesium (Mg)-, iron (Fe)-, aluminum (Al)-, manganese (Mn)-, zinc (Zn)-, copper (Cu)-, molybdenum (Mo)-, nitrogen (N)-, phosphorus (P)-, sulfur (S)-, boron (B)-, nickel (Ni)-based salt ions, and combinations thereof.

[0023] The crosslinking agent can include at least one crosslinking molecular compound selected from the group consisting of genipin, polydopamine, lignosulfonate, chitosan, glutaraldehyde, citric acid, and polyvinyl alcohol.

[0024] The biogel can further include lignin, hemicellulose, holocellulose, proteins, fatty acids, or combinations thereof. The biogel can further include air bubbles, nanobubbles, or biochar. The biogel can include at least one cellulose-fiber derivative, which can be carboxylated cellulose fibers and / or sulfonated cellulose fibers.

[0025] The above and other features, elements, characteristics, steps, and advantages of the present invention will become more apparent from the following detailed description of example embodiments of the present invention with reference to the attached drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The patent or application file contains at least one drawing executed in color. The patent or application file also contains a corresponding black and white line drawing for each of the at least one drawing executed in color. Copies of this patent or patent applicationpublication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0027] Fig. 1 provides a schematic flowchart illustrating the formation of the biogel or hydrogel growing medium.

[0028] Figs. 2A and 2B shows a successful germination of pelleted lettuce seeds (> 90%- 95%). The vegetative stage is shown after almost two and a half weeks, showing successful plant growth with Ca+2concentrations of 100 mM at (a) and 200 mM at (b), as well as Mg+2concentrations of 100 mM at (c) and 200 mM at (d). Fig. 2A is in black and white. Fig. 2B is in color.

[0029] Fig. 3 shows steady shear viscosity at the steady state versus shear rate for various biogels (crosslinked using a Ca+2solution (200 mM), a Mg+2solution (200 mM), a Ca+2(100 mM) and Fe+3(100 mM) mixed solution at a ratio of 4:1, a Ca+2(100 mM) and Al+3(100 mM) mixed solution at a ratio of 4:1). All the samples showed notable shear thinning behavior, which was mainly caused by the collapse of cellulose gel networks at higher shear rates.

[0030] Figs. 4A-4C show dynamic frequency sweeps for various ion induced biogels (crosslinked using a Ca+2solution (200 mM), a Mg+2solution (200 mM), a Ca+2(100 mM) and Fe+3(100 mM) mixed solution at a ratio of 4:1, a Ca+2(100 mM) and Al+3(100 mM) mixed solution at a ratio of 4:1). Fig. 4A shows the storage modulus (closed symbol); Fig. 4B shows loss modulus (open symbol); Fig. 4C shows tan(6) data of control and biogels crosslinked by various ions. All the ion induced samples showed greater storage modulus than loss modulus over the entire range of frequency (0.1 Hz to 100 Hz), indicating solid-like behavior of biogels.Furthermore, hydrogels induced by the addition of trivalent ions (Al3+and Fe3+) demonstrated higher values for both storage modulus and loss modulus compared to those induced only by divalent ions (Ca+2and Mg+2) without trivalent ions, reflecting the increase in material stiffness. The tan(6) data represents the relative measure of the viscous and elastic properties of the material. The value of tan 6 was higher for free cellulose nanofibers (CNFs) than the divalent and trivalent cations induced biogels. The decrease in tan6 of the biogel indicates an increase in the gel strength, which is caused by ionic crosslink among cellulose nanofibers (CNFs_ with the cations creating a stiffer gel structure.

[0031] Figs. 5A and 5B show optical microscopic images of oxidized cellulose microfibers prior to homogenization, highlighting the structural aggregation of nanofibers into microfibers. The inset shows the oxidized cellulose microfiber slurry in a vial. Fig. 5A is in black and white. Fig. 5B is in color.

[0032] Fig. 6 shows the results of FTIR-ATR spectroscopy conducted to analyze the chemical functionality of oxidized cellulose microfibers produced by a nitro-oxidation process (NOP). These microfibers were used to formulate biogel plugs or mats according to example embodiments of the present invention.DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0033] Specific example embodiments of the present invention are provided. The example embodiments are given merely as illustrations and do not constitute a comprehensive compilation. The example embodiments of the present invention can be implemented in a number of different ways. The figures may not be accurate to scale, and some aspects may have been emphasized or downplayed to draw attention to particular areas. Thus, the particular structural and functional information provided should not be interpreted as restrictive, but rather as a basis modifying the example embodiments of the present invention in many ways.

[0034] Herein, the term "biogel growing medium" refers to a substrate that can be peat free, soil free, coir free, wood fibers and chips free, etc. or a combination of materials. This substrate is designed to provide physical support, retain water, incorporate air bubbles, and supply nutrients for plant growth. The substrate can facilitate seed germination and can enable the establishment of a plant's root system within the biogel growing medium. This, in turn, promotes root growth as the roots extend into the spaces between individual cellulose fibers of the medium. Frequently, as a transparent hydrogel, the biogel allows observation of root development and propagation during seed germination and plant growth.

[0035] Herein, the term "cellulose" denotes an oxidized cellulosic fibrous material ranging in cross-sectional size from macro to micro to nano, extractable from any lignocellulosic biomass feedstocks and / or natural organic wastes. This cellulose is crosslinked with a salt or mixed salts, for example, to enhance water and nutrient retention and to anchor a seedsecurely on the gel surface for a duration adequate for seed germination and root development within the biogel plugs or mats.

[0036] Biomass feedstocks can be sourced from both woody and non-woody plants, encompassing agricultural residues and natural fibers. These include materials derived from jute, palm trees, sugarcane bagasse, corn, wheat, oats, rice, sorghum, oil palm, bamboo, spinifex, coastal bermudagrass, miscanthus, switchgrass, seaweeds, flax, hemp, ramie, kenaf stalk fiber, kenaf core, abaca, sisal, pineapple, banana leaf, banana peel, banana fiber, curaua, lotus leaf stalk, roselle, seed hair fiber, cotton fiber, kapok fiber, areca nut fiber, coconut, potato, cabbage, tomato, rubberwood, Indian screw tree, achira fiber, citrus, soybean, soybean straw, spent grain, soy hull, pea hull, grape pomace, fruit pomace, and various combinations thereof.

[0037] Cellulose extraction is not limited to plant sources; it can also be derived from bacteria, algae, tunicate, or their various combinations. The growing medium can encompass one or more nanocellulose components. The term 'nanocellulose components' encompasses cellulose nanofibers (CNF), cellulose nanocrystals (CNC), tunicate cellulose, bacterial cellulose, or amalgamation or derivatives thereof.

[0038] Natural organic waste can encompass food waste (green waste, fruits and vegetable wastes, meat and fish wastes including bones), food-soiled paper, non-hazardous wood waste, green waste, landscape waste, and other sources of waste products of organic origin. This includes by-products from gardening, agriculture, forestry, timber industry, food processing industries, and similar sources, which have garnered growing interest as potential starting materials for the cellulose production for various biogel products.

[0039] An illustration of the CNF preparation through a nitro-oxidation process (NOP) for step (a) is outlined in U.S. Pat. No. 10,894,838, which is incorporated by reference in its entirety. This NOP process employs various biomass feedstocks, allowing for the utilization of both hard and softwoods, including agricultural residues. However, non-woody feedstocks with low lignin content, specifically agricultural residues, can be used in this procedure.

[0040] Crosslinking refers to the interaction between negatively charged cellulose fibers and positively charged salt ions through electrostatic attraction. This interaction involves twoparticle types with opposite charges, leading to mutual attraction. Depending on the type of salt ions, such as transitional metal ions, interactions with cellulose functionalities can occur through a metal-ligand interaction. This interaction can involve a coordinate covalent bond, also known as a dative covalent bond, dipolar bond, or coordinate bond. Besides salts, molecular compounds such as genipin, polydopamine, lignosulfonate, chitosan, glutaraldehyde, citric acid, polyvinyl alcohol, or others can be used to crosslink the cellulose fibers to form a biogel substrate.

[0041] In certain example embodiments, the crosslinking agent includes monovalent (n - +1), divalent (n - +2), and trivalent (n - +3) salts. These salts, including both cation and counterions, can be selected from include sodium (Na)-, potassium (K)-, calcium (Ca)-, magnesium (Mg)-, iron (Fe)-, aluminum (Al)-, manganese (Mn)-, zinc (Zn)-, copper (Cu)-, molybdenum (Mo)-, nitrogen (N)-, phosphorus (P)-, sulfur (S)-, boron (B)-, chlorine (Cl)-, nickel (Ni)-based salt ions, or a combination thereof. In some example embodiments, the salts can be selected from calcium (Ca), magnesium (Mg), zinc (Zn), iron (Fe), aluminum (Al), or combinations thereof. It is also possible to use other salts.

[0042] These components act as macronutrients and micronutrients for the plants that are utilized to form a biogel. These salts, and similar types, can be applied in the form of solution or granules, powder, pills, or equivalent forms.

[0043] A biogel composition or growing medium can include cellulose in the range of approximately 0.01 wt% to approximately 99.99 wt%, within manufacturing and / or measurement tolerances, combined with a salt solution in the concentration range of about 0.001 to about 1000 mmol, within manufacturing and / or measurement tolerances. In specific formulations, the biogel composition or growing medium can include approximately 0.01 wt% cellulose and about 1.0 wt% cellulose components, within manufacturing and / or measurement tolerances. Alternatively, the biogel composition or growing medium can include cellulose in the range of about 1.0 wt% to about 10 wt%, within manufacturing and / or measurement tolerances, and cellulose components in the range of about 10 wt% to about 20 wt%, within manufacturing and / or measurement tolerances. Another variation might involve cellulose in the range of about 20 wt% to about 30 wt%, within manufacturing and / or measurementtolerances, and cellulose components in the range of about 30 wt% to about 40 wt%, within manufacturing and / or measurement tolerances. In an alternate formulation, the biogel composition or growing medium can include about 40 wt% cellulose and about 50 wt% cellulose components, within manufacturing and / or measurement tolerances. In other words, the growing medium can include about 1.0 wt% to about 50 wt% cellulose components, within manufacturing and / or measurement tolerances. Moreover, the composition can integrate about 50 wt% to about 100 wt%, within manufacturing and / or measurement tolerances, or more of additional components, relative to the total weight of the biogel or growing medium.

[0044] To achieve a stable growing medium crosslinked by various ions, a cellulose content of at least approximately about 0.5 wt%-about 1 wt%, within manufacturing and / or measurement tolerances, or around about 1 wt%-about 5 wt%, within manufacturing and / or measurement tolerances, can be used.

[0045] A salt solution can encompass monovalent, divalent, or trivalent ions within a concentration range of approximately about 1 mmol to about 100 mmol. Alternatively, the salt solution can include salts ranging from about 100 mmol to about 200 mmol, within manufacturing and / or measurement tolerances, accompanied by ion components in the range of about 200 mmol to about 500 mmol, within manufacturing and / or measurement tolerances. Furthermore, the individual salts or a combination of various salts can incorporate an additional 500 mmol to 1000 mmol or more, relative to the total weight of the cellulose in the biogel or growing medium.

[0046] While cellulose is a major ingredient of the biogel, the biogel can also include one or more of lignin, hemicellulose, holocellulose, proteins, or fatty acids. The specific composition of lignin depends on the feedstock used. If softwood is utilized, then the lignin includes coniferyl alcohol; for hardwood, the lignin includes coniferyl alcohol and sinapyl alcohol; and grass lignin includes three monomers: coniferyl, sinapyl, and p-coumaryl alcohol. Hemicellulose includes xyloglucans, xylans, mannans, glucomannans, and beta-(l-->3,l-->4)-glucans. Additionally, cellulose can contain proteins and their derivatives, such as amino acids and fatty acids depending on the used feedstocks. During NOP, effluents can contain additional nutrients extracted from the feedstock (referred to as "feedstock nutrients), which can be incorporatedinto the cellulose matrix in the biogel. The inclusion of NOP effluents can enhance the overall nutritional value in biogel growth medium for plant growth.

[0047] Referring to Fig. 1, this schematic flowchart outlines the process of creating biogel or growing medium. In step a), carboxylated cellulose is extracted from various biomass feedstocks and natural organic matters (i), along with plant macro- or micro-nutrient salt ions (I), where n - +1, +2, and +3 ions (ii). This combination results in the formation of the initial biogel composition (iii).

[0048] The cellulose components (i) can be derived from both woody and non-woody feedstocks, including non-woody feedstocks with low-lignin content, along with natural organic waste components. Typically, step a) involves combining cellulose fibers with a crosslinking agent to form a biogel and then incubating the biogel to crosslink the cellulose fibers and crosslinking agent to solidify the biogel when the cellulose fibers and crosslinking agents crosslink to obtain the soil-free growing media. The biogel can solidify when the surface charge of the cellulose fibers is partially or fully neutralized, i.e., l%-100% neutralized, with the crosslinking agent. For example, the biogel can solidify when the COO’ or SO42of the cellulose fibers are neutralized with the crosslinking agent. The crosslinking agent can be an inorganic salt or a crosslinking molecular compound. The soil-free growing media can have a water holding capacity of approximately 1%-approximately 99% or more.

[0049] For example, step a) can involve combining about 1 wt% to about 2 wt% of cellulose fibers, within manufacturing and / or measurement tolerances, with about 100 mmol to about 200 mmol salt solutions, within manufacturing and / or measurement tolerances, based on the total weight or volume of the biogel composition or growing medium. But other amounts and concentrations of materials can be used. In addition to or instead of the cellulose fibers, cellulose-fiber derivatives can be combined with the salt solutions. For example, the cellulose- fiber derivative can include functionalized cellulose fibers, such as carboxylated cellulose fibers and sulfonated cellulose fibers.

[0050] Alternatively, step a) can involve combining about 2 wt% to about 10 wt% of cellulose fibers with about 200 mmol to about 500 mmol of plant nutrients, within manufacturing and / or measurement tolerances. Another option is to combine about 10 wt% to50 wt% of cellulose fibers, within manufacturing and / or measurement tolerances, with about 500 mmol to 1000 mmol of nutrient salts, within manufacturing and / or measurement tolerances. In a further alternative, the initial composition (i) can predominantly include about 100% cellulose fibers, within manufacturing and / or measurement tolerances with an ionic concentration exceeding about 1000 mmol, within manufacturing and / or measurement tolerances, based on the total weight of the biogel composition or growing medium.

[0051] In step b), the initial composition in (III) undergoes incubation for about 1 min-about 100 hours, within manufacturing and / or measurement tolerances, at ambient or room temperature to facilitate the diffusion of provided ions from the top to the bottom. Ambient or room temperature can be in the range of 19°C to 25°C (66°F to 77°F), within measurement tolerances. For some applications, the incubation period can be about 1 hour to about 3 days (about 72 hours), within manufacturing and / or measurement tolerances, or can be about 1 day (about 24 hours) to about 3 days (about 72 hours), within manufacturing and / or measurement tolerances. The extent of ionic diffusion is typically influenced by the capillary force generated by surface tensions and the pore sizes of the hydrogel. To minimize fast evaporation of moisture content in the biogel composition or growing medium, the biogels can be stored in the refrigerator at about 5°C-about 8°C for a duration sufficient for this purpose. The biogel can be kept at room temperature for less than 7 days-10 days to mitigate plugs shrinkage.

[0052] In step c), the initial composition (iii) has the option of being infused with air bubbles or nanobubbles (air and / or oxygen) (iv) using a nanobubble generator. This process aims to stimulate root growth and contribute to the formation of the biogel composition or growing medium. The bubbles can be infused with ions in real-time. Additional components like biochar or activated carbon (v) can be introduced during steps (a-e). This approach has been demonstrated to enhance the pore volume, improved aeration, enhanced water absorption, and environmentally friendly attributes.

[0053] The moisture or water content of the biogel composition or growing medium (a-e) typically is over 99% of the total weight of the biogel composition or growing medium where the remaining 1 wt% is cellulose fibers.

[0054] In an optional step e), the biogel composition or growing medium (iii) undergoes further refinement, and additional components (iv) and (v) mentioned earlier can be incorporated.

[0055] As mentioned previously, the biogel composition or growing medium can be used independently or integrated into a traditional substrate or growing medium, serving as a partial or complete substitute for one or more components. It has the flexibility to replace various constituents commonly found in growing mixes, such as peat, wood fibers, wood chips, composted pine bark, perlite, vermiculite, volcanic gravel, mulch, black soil, sand, rock wool, compost, animal manure, rice hulls, hardwood bark, softwood bark, coir, other organic materials like composted organic matter, or a combination thereof.

[0056] The substitution by the biogel composition or growing medium can be incremental, displacing a specified percentage of the existing components in a growing mix. The replacement percentages can vary, ranging from about 1 wt% to about 99 wt%, within manufacturing and / or measurement tolerances, of one or more components in the soil or soilless composition or growing medium. For example, in a standard growing mix including about 70 wt%-about 80 wt% peat, within manufacturing and / or measurement tolerances, and about 20 wt%-about 30 wt% perlite, within manufacturing and / or measurement tolerances, or about 60%-about 70% of coir, within manufacturing and / or measurement tolerances, and about 30%-about 40% of peat, within manufacturing and / or measurement tolerances, the growing medium of example embodiments of the present invention can completely replace the peat, coir, and perlite.

[0057] This resulting growing medium provides environmental advantages by significantly reducing peat content, making it more economically viable compared to conventional growing mixes that typically include perlite or other materials. Additionally, the growing medium exhibits superior water retention compared to traditional mixes involving peat, perlite, and other components, substantially reducing water demand for plants. The crosslinking ions in the biogel act as plant macronutrients and / or micronutrients, enhancing the efficiency and speed of plant growth compared to other substrates.

[0058] Moreover, as a transparent matrix, this substrate allows for the observation and monitoring of root propagation throughout the medium, enabling real-time monitoring of plantgrowth. Apart from traditional farming, such a substrate is easily adaptable to hydroponics, vertical farming, floriculture, aeroponics, and other cultivation methods.

[0059] Air bubbles can be already present in the cellulose fibers, generated during the homogenization process, depending on the amount of lignin. These inherent air bubbles within the growing medium create optimal conditions for plant growth by effectively spreading dissolved oxygen more widely throughout the growing medium. This can help with the development of the root systems and the overall plant health. Roots play several roles, including the absorption of oxygen for growth, as well as the uptake of water and minerals. Well-oxygenated roots enhance the efficiency of plants in converting sugars into energy for growth, while at the same time, ensuring adequate water retention in the growing medium. This can allow the roots to have access to the right amount of water, allowing it to travel through the stems to the leaves for processes such as photosynthesis, root growth, and efficient water uptake by the growing plant without becoming oversaturated. However, conventional growing mixes often face challenges in maintaining an uninterrupted supply of water on demand.

[0060] As indicated in Table 1 of this document, the pH of the biogel composition or growing medium can vary within the range of 2.82 to 6.43, depending on the crosslinking cations used. While some biogel growing media exhibit an ideal pH range for plant growth, such as 5.8 to 6.2 for lettuce, those with lower pH levels can be easily adjusted using cellulose fibers with a higher pH or adjusting pH of added trivalent ions. Additionally, the biogel contains nutrients (pS) ranging from about 471 to about 1763, depending on the ions used for crosslinking the fibers. Also, the cellulose fibers contain ammonium hydroxide (NH4OH) which has been used to raise the pH prior to homogenization of the cellulose fibers. The presence of (NH4+) could potentially serve as a nitrogen source for the plants. Additionally, the counterions of the added salts were nitrate (NO3)-based, contributing to the overall nitrogen requirement of the plants. Plants have the ability to absorb nitrogen in the forms of (NO3 ) or (NH4+), and their total nitrogen uptake typically involves a combination of both (NH4+) and (NO3 ).

[0061] The biogel composition or growing medium can incorporate feedstock nutrients.Ideally, the NOP effluents can be enhanced nutritionally with monovalent, divalent, andtrivalent ions that are naturally present in the feedstocks. Moreover, the effluent can include compounds obtained from plants, fungi, bacteria, lichens, invertebrates, insects, minerals, or a combination thereof. Notably, exemplary sources of feedstock plant nutrients include, but are not limited to, calcium, magnesium, phosphate, potassium, and more.

[0062] The properties of feedstocks, such as the amount of lignin, moisture, and other factors, can influence both the cellulose fibers and the intensity of color imparted to the biogel and growing media. For instance, lower amounts of lignin can yield a light white or transparent color in the biogel composition or growing medium, whereas higher quantities of lignin can result in a dark yellowish or brownish-yellow hue. The color appearance of biogel or growing media is also contingent on the color of the crosslinking agent solution. For instance, calcium, magnesium, and aluminum nitrate typically produce a similar transparent color in cellulose fibers, appearing almost clear. In contrast, iron can generate a biogel with a red color.

[0063] Table 2 provides test results for a specific example embodiment of a biogel composition or growing medium, including approximately 0.9 wt%-approximiately 1.0 wt% cellulose components, within manufacturing and / or measurement tolerances, and approximately 100 mmol-approximately 200 mmol of crosslinking cations, within manufacturing and / or measurement tolerances.

[0064] The biogel composition in example embodiments of the present invention has the benefit of attaining a greater water holding capacity, specifically over 99%. These percentages are calculated based on the total volume of the biogel or growing medium, measured in a vial with dimensions of 2 cm in diameter and 3.03 cm in height.

[0065] Gardeners seeking water conservation through intelligent irrigation techniques may explore the use of innovative substrates like biogel or specialized growing media. These substrates can prove effective, particularly for plants with higher water requirements, optimizing water usage in comparison to plants with lower water needs.Wet and dry bulk density of biogel

[0066] The bulk density of the biogel can be influenced by the cellulose composition of the growing media and the level of compaction due to ionic crosslinking. The determination of cellulose bulk density typically involves extracting a core sample by inserting a metal corer intothe biogel at the desired depth and horizon. This process yields a biogel sample with a known total volume (Vt). Subsequently, both wet bulk density (g / cm3) and dry bulk density (g / cm3) can be calculated from this sample. The wet bulk density of the biogel and growing media can range from about 0.90 g / cm3to about 0.94 g / cm3, within manufacturing and / or measurement tolerances.

[0067] The feasibility of biogel or growing media, prepared with Ca+2and Mg+2within a pH range of about 5.9-about 6.5, within manufacturing and / or measurement tolerances, has been examined for the growth of leafy greens, particularly lettuce, as illustrated in Figs. 2A and 2B. Following a successful germination of pelleted lettuce seeds (> 90%-95%), the vegetative stage is shown after almost two and a half weeks, showing successful plant growth with calcium concentrations of 100 mM at (a), 200 mM at (b), as well as magnesium concentrations of 100 mM at (c) and 200 mM at (d). This formulation can be further optimized for the growth of various plants using the same optimized condition.

[0068] Due to the high-water content (> 99%) in the biogel or growing media, there is a tendency for the plugs to shrink over time. This phenomenon occurs more rapidly in lower atmospheric moisture or humidity conditions. To mitigate the shrinking effect of the biogel or growing media, storing them in a refrigerator at a temperature between 4°C to 8°C can slow down the shrinkage process. Alternatively, to address the shrinking effects of biogels or growing media, incorporating about 5 wt% to about 99 wt% of cellulose-based fibers, pulped fibers or partially pulped fibers, biochar, or other carbon-based materials, within manufacturing and / or measurement tolerances, in the initial composition (based on the total weight of the initial composition) is suggested. Additional materials like traditional soil or soil-less growing media can be introduced during the production process, allowing the final solid composition of the biogel product to be adjusted to the desired level.

[0069] The biogel composition or growing medium can have a different viscosity and stiffness depending on the types of ions use. Fig. 3 shows steady shear viscosity versus shear rate of various biogels. The steady shear viscosity of various ion induced biogels are presented in Fig. 3. All of the biogels showed notable shear thinning behavior, which was mainly caused bythe collapse of cellulose gel networks. A small amount of additional trivalent cations can significantly increase the viscosity of the biogel over the entire shear rate range, indicating more crosslinking taking place between trivalent cations than divalent cations.

[0070] Figs. 4A-4C show the storage modulus and loss modulus of various ion induced. All cation crosslinking biogel samples showed greater storage modulus than loss modulus over the entire range of frequency (0.1 Hz to 100 Hz), representing solid-like behavior. These results were also confirmed with tan 6 < 1. For the CNF control, the value of tan 6 was higher than the cations induced biogel. The decrease in tan 6 indicated an increase in gel strength, which caused by crosslinking between cellulose fibers rendering a stiffer biogel structure. Furthermore, hydrogels induced by trivalent ions (Al3+and Fe3+) demonstrated higher values for both storage modulus and loss modulus compared to those induced by divalent ions, reflecting increased material stiffness.

[0071] Figs. 5A and 5B show carboxylated cellulose microfibers produced via the NOP approach. These carboxylated cellulose microfibers were successfully homogenized and fibrillated into cellulose nanofibers (CNFs), which can be utilized in the fabrication of biogels- based plugs or mats through crosslinking with metal or non-metal crosslinking cations. The oxidized cellulose fibers, functionalized with carboxyl (-COOH) groups, exhibit a width of less than 100 microns and a length exceeding several hundred microns prior to homogenization. Fibers with a higher aspect ratio, particularly those with increased length, can be used to enhance the structural integrity and mechanical strength of biogel plugs designed for plant growth applications. As shown in the inset image, the oxidized cellulose fibers exhibit a whitish coloration, indicative of their modified surface chemistry and fibrillar morphology.

[0072] The results of attenuated total reflectance-Fourier transform infrared (FTIR-ATR) spectroscopy of carboxylated cellulose fibers is shown in Fig. 6, which displays the spectrum of several characteristic cellulose peaks: a broad peak at 3335 cm-1corresponding to O-H stretching, and a peak at 2901 cm-1attributed to C-H symmetrical stretching from the cellulose structure. Additionally, a peak at 1717 cm-1represents stretching of COOH from the oxidized cellulose fibers that typically participate in the crosslinking with different monovalent, divalent, or trivalent ions that results in biogel growing media production.

[0073] The application of biogel or growing media extends beyond gardening and can find valuable use in various agricultural sectors, particularly as a soil amendment to enhance productivity while mitigating water losses during drought or water-stressed conditions.Incorporating biogel into sandy soils can augment plant water availability through a gradual and sustained release of water. The water molecules within biogel exist in free, intermediate, and bound states, ensuring a controlled and gradual supply based on plant demands.

[0074] Moreover, biogel and growing media exhibit versatile applications in hydraulic contexts, such as supporting vegetation growth, aiding in restoration efforts, and enhancing soil mechanics and erosion resistance. The cellulose present in biogel can directly bond with soil or sand components. The high viscosity of biogel enables it to serve as a bed or binder for hydroseeding, where a mixture of biogel and seeds forms a slurry applied to the ground. This application offers advantages such as nutrient delivery, improved germination, and enhanced plant establishment, among other benefits.

[0075] In addition to its role as a soil amendment, biogel or growing media proves highly beneficial in addressing various environmental challenges. These applications include erosion control in erosion-prone areas, the incorporation of hydrogels in erosion control blankets, land reclamation initiatives, slope stabilization projects, and dust suppression in construction sites. The unique properties of biogel make it a versatile solution for mitigating erosion, promoting ecological restoration, and ensuring stability in diverse landscapes.

[0076] It should be understood that the foregoing description is only illustrative of the present invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the present invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications, and variances that fall within the scope of the appended claims.

Claims

CLAIMS1. A method for preparing a soil-free growing media comprising:(a) forming a biogel by combining: cellulose fibers that are macro-, micro- and / or nano-scale; and a crosslinking agent; and(b) incubating the biogel until the biogel solidifies when the cellulose fibers and the crosslinking agent crosslink to obtain the soil-free growing media.

2. The method of claim 1, wherein the biogel solidifies when a surface charge of the cellulose fibers is partially or fully neutralized with the crosslinking agent.

3. The method of claim 1 or 2, wherein the step (b) of incubating the biogel is performed for about 1 min to about 100 hours at room temperature.

4. The method of claim one of claims 1-3, wherein the soil-free growing media has a water holding capacity of approximately 1%-approximately 99% or more.

5. The method of one of claims 1-4, wherein the cellulose fibers are obtained from lignocellulosic biomass feedstocks and / or natural organic wastes.

6. The method of claim 5, wherein the biomass feedstocks are derived from woody and / or non-woody plants.

7. The method of claim 5 or 6, wherein the biomass feedstocks are derived from jute, palm trees, sugarcane bagasse, corn, wheat, oats, rice, sorghum, oil palm, bamboo, spinifex, coastal bermudagrass, miscanthus, switchgrass, azolla, seaweeds, flax, hemp, ramie, kenaf stalk fiber, kenaf core, abaca, sisal, pineapple, banana leaf, banana peel, banana fiber, curaua, lotus leaf stalk, roselle, seed hair fiber, cotton fiber, kapok fiber, areca nut fiber, coconut, potato,cabbage, tomato, rubberwood, Indian screw tree, achira fiber, citrus, soybean, soybean straw, spent grain, soy hull, pea hull, grape pomace, fruit pomace, or combinations thereof.

8. The method of one of claims 5-7, wherein the biomass feedstocks or the cellulose fibers are derived from bacteria, algae, tunicate, or combinations thereof.

9. The method of one of claims 5-8, wherein the natural organic wastes include food waste, green waste, fruits and vegetable wastes, meat and fish wastes including the bones, food-soiled paper, non-hazardous wood waste, green waste, landscape waste, other sources of waste products of organic origin, or combinations thereof.

10. The method of one of claims 1-9, wherein the crosslinking agent is at least one inorganic salt and / or at least one crosslinking molecular compound.

11. The method of claim 10, wherein the at least one inorganic salt is selected from the group consisting of sodium (Na)-, potassium (K)-, calcium (Ca)-, magnesium (Mg)-, iron (Fe)-, aluminum (Al)-, manganese (Mn)-, zinc (Zn)-, copper (Cu)-, molybdenum (Mo)-, nitrogen (N)-, phosphorus (P)-, sulfur (S)-, boron (B)-, nickel (Ni)-based salt ions, and combinations thereof.

12. The method of claim 10, wherein the at least one inorganic salt is selected from the group consisting of calcium (Ca)-, magnesium (Mg)-, iron (Fe)-, aluminum (Al)-, zinc (Zn)-, nitrogen (N)-, potassium (K)-based salts, and combinations thereof.

13. The method of claim 10, wherein the crosslinking agent includes at least one crosslinking molecular compound selected from the group consisting of genipin, polydopamine, lignosulfonate, chitosan, glutaraldehyde, citric acid, and polyvinyl alcohol.

14. The method of one of claims 1-13, wherein step (a) includes a growing medium including cellulose in a range of about 0.01 wt% to about 99.99 wt% combined with a salt solution in a concentration range of about 0.01 mmol to about 1000 mmol.

15. The method of claim 14, wherein the growing medium includes about 0.01 wt% to about 40 wt% cellulose including cellulose nanofibers, cellulose nanocrystals, tunicate cellulose, bacterial cellulose, or amalgamations thereof.

16. The method of one of claims 1-15, wherein the biogel further includes lignin, hemicellulose, holocellulose, proteins, fatty acids, or combinations thereof.

17. The method of one of claims 1-16, further comprising step (c) of infusing the biogel with air bubbles, nanobubbles, or biochar.

18. The method of one of claims 1-17, wherein step (a) of forming the biogel includes further combining at least one cellulose-fiber derivative.

19. The method of claim 18, wherein the at least one cellulose-fiber derivative includes carboxylated cellulose fibers and / or sulfonated cellulose fibers.

20. A method of growing plants comprising planting seeds or plants in a soil-free growing media made by the method of one of claims 1-19.

21. A soil-free growing media made by the method of one of claims 1-19.

22. A soil-free growing media comprising: a solidified biogel including: cellulose fibers that are macro-, micro- and / or nano-scale; anda crosslinking agent; wherein the cellulose fibers and the crosslinking agent are crosslinked.

23. The soil-free growing media of claim 1, wherein a surface charge of the cellulose fibers is partially or fully neutralized with the crosslinking agent.

24. The soil-free growing media of claim 22 or 23, the soil-free growing media has a water holding capacity of approximately 90%-approximately 99% or more.

25. The soil-free growing media of one of claims 22-24, wherein the crosslinking agent is at least one inorganic salt and / or at least one crosslinking molecular compound.

26. The soil-free growing media of claim 25, wherein the at least one inorganic salt is selected from the group consisting of sodium (Na)-, potassium (K)-, calcium (Ca)-, magnesium (Mg)-, iron (Fe)-, aluminum (Al)-, manganese (Mn)-, zinc (Zn)-, copper (Cu)-, molybdenum (Mo)-, nitrogen (N)-, phosphorus (P)-, sulfur (S)-, boron (B)-, nickel (Ni)-based salt ions, and combinations thereof.

27. The soil-free growing media of claim 25, wherein the at least one inorganic salt is selected from the group consisting of calcium (Ca)-, magnesium (Mg)-, iron (Fe)-, aluminum (Al)-, zinc (Zn)-, nitrogen (N)-, potassium (K)-based salts, and combinations thereof.

28. The soil-free growing media of claim 25, wherein the crosslinking agent includes at least one crosslinking molecular compound selected from the group consisting of genipin, polydopamine, lignosulfonate, chitosan, glutaraldehyde, citric acid, and polyvinyl alcohol.

29. The soil-free growing media of one of claims 22-28, wherein the biogel further includes lignin, hemicellulose, holocellulose, proteins, fatty acids, or combinations thereof.

30. The soil-free growing media of one of claims 22-29, wherein the biogel includes air bubbles, nanobubbles, or biochar.

31. The soil-free growing media of one of claims 22-30, wherein the biogel includes at least one cellulose-fiber derivative.

32. The soil-free growing media of claim 31, wherein the at least one cellulose-fiber derivative includes carboxylated cellulose fibers and / or sulfonated cellulose fibers.

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