Pressure assisted nitro-oxidation process for upcycling natural organic waste

Abstract

Processes include treating natural organic materials from diverse waste sources using nitric acid (HNO3) as the primary chemical under pressure conditions. The pressurizing medium includes air, NOx, N2, CO2, O2, O3, and NH3 and their mixtures under pressure between about 10 psi and about 750 psi, at a temperature ranging from about 25°C to about 100°C and for a duration ranging from about 0.1 hours to about 72 hours. The resulting fibers and effluent can be used to make cellulose-based farming products, such as biogel growing media, soilless substrate binding agents, water and nutrient retention agents, and liquid fertilizers.

Description

PRESSURE ASSISTED NITRO-OXIDATION PROCESS FOR UPCYCLING NATURAL ORGANIC WASTE CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Patent Application No. 63 / 571,059 filed onMarch 28, 2024. The entire contents of this application are hereby incorporated by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention

[0002] The present invention relates to nitro-oxidation processes (NOPs). More specifically,the present invention relates to nitro-oxidation processes performed under pressure (i.e., pressure-assisted NOPs (PANOPs)) that can be used to upcycle natural organic waste. 2. Description of the Related Art

[0003] Interest has been growing in using natural organic wastes from sources, such asgardening, horticulture, agriculture, forestry, timber industry, food processing and dairy industry, and animal husbandry, as feedstock materials for creating valued products. These waste resources, derived from natural organic origins, are being considered for repurposing into new products.

[0004] Many of the existing waste processing techniques require large amounts of land,chemicals, water, and / or consume a great deal of energy. Furthermore, any equipment or facility used in the process may corrode or deteriorate due to the chemicals or processing times.

[0005] Enhanced techniques, especially capable of reducing time, chemicals, and energy forprocessing natural organic waste to create valued products are highly sought after. SUMMARY OF THE INVENTION

[0006] To overcome the problems described above, example embodiments of the presentinvention provide methods of treating natural organic wastes from diverse waste sources using nitric acid as the primary treatment chemical under pressure conditions, where the methodscan significantly reduce the processing time, the amount of nitric acid, and the concentration of nitric acid used.

[0007] Nitric acid is an essential chemical in manufacturing of synthetic nitrogen fertilizers(e.g. ammonium nitrate). It is a strong digestion reagent and an effective oxidant for the decomposition of organic matter and oxidation of lignocellulosic components. The pressurizing medium includes air, NOx, N2, CO2, O2, O3, and NH3and their mixtures.

[0008] In certain example embodiments, the methods provided involve combininglignocellulosic biomasses, chitin biomasses, starch biomasses, protein biomasses, and / or their mixtures as feedstocks with nitric acid at a concentration from moderate level to highly concentrated level (e.g., 20% (v / v) – 65% (v / v)) along with one or more catalytic agents (e.g., metals, metal oxides, nitrites and nitrates), which can also exist as impurities in the feedstocks. This mixture is then maintained at a temperature ranging from 25°C to 100°C and a pressure between 10 psi and 750 psi for a duration ranging from 0.1 hours to 72 hours. Following this, the treated fiber residues (e.g. carboxylated cellulose and chitin) and effluents are separated from the mixture.

[0009] In certain example embodiments, the plant biomass encompasses a variety ofmaterials such as lignocellulosic woods, lignocellulose non-woods (natural fibers, grasses, and agricultural residues), pure cellulose (e.g., wood pulps, papers and carboards), phytoplanktons, algal celluloses, tunicate celluloses, and their combinations.

[0010] In certain example embodiments, the sources from which the plant biomass can beused include woody and non-woody plants such as jute, palm trees, sugarcane bagasse, corn, wheat, oat, rice, sorghum, oil palm, bamboo, spinifex, coastal bermudagrass, miscanthus, switchgrass, azolla, seaweed, flax, hemp, ramie, kenaf stalk fiber, kenaf core, abaca, sisal, pineapple, banana leaves, banana peels, banana fibers, curaua, lotus leaf stalks, roselle, seed hair fiber, cotton fiber, kapok fiber, areca nut fiber, coconut, potato, cabbage, tomato, vegetable, rubberwood, Indian screw tree, achira fiber, citrus, soybean, soybean straw, spent grain, soy hull, pea hull, grape pomace, fruit pomace, and their combinations.

[0011] In certain example embodiments, the protein biomass from sources that can beused can include cow, chicken, fish, pig, goat, lamb, duck, turkey, prawns, crab, shrimp, lobster, mussels, oysters, scallops, clams, and various combinations of these.

[0012] In certain example embodiments, the protein biomass can include a blend oflignocellulosic and protein feedstocks, including cow manure, horse manure, chicken manure, pig manure, food waste, and various mixtures of these elements.

[0013] In some example embodiments, the acid component also includes an additional acidchosen from among hydrochloric acid, sulfuric acid, acetic acid, hydrobromic acid, hydrofluoric acid, or a combination of these acids.

[0014] In certain example embodiments, the component used as an oxidizing agent isincludes a nitrite salt, specifically chosen from a list that includes sodium nitrite (NaNO2), potassium nitrite (KNO2), ammonium nitrite (NH4NO2), calcium nitrite (Ca(NO2)2), magnesium nitrite (Mg(NO2)2), barium nitrite (Ba(NO2)2), lithium nitrite (LiNO2), zinc nitrite (Zn(NO2)2), copper(II) nitrite (Cu(NO2)2), and silver nitrite (AgNO2), along with various combinations of these salts.

[0015] In certain example embodiments, the component used as an oxidizing agentincludes a nitrate salts, specifically chosen from a list that includes sodium nitrate (NaNO3), potassium nitrate (KNO3), ammonium nitrate (NH4NO3), calcium nitrate (Ca(NO3)2), magnesium nitrate (Mg(NO3)2), barium nitrite (Ba(NO3)2), lithium nitrite (LiNO3), zinc nitrite (Zn(NO3)2), copper(II) nitrite (Cu(NO3)2), and silver nitrite (AgNO3), along with various combinations of these salts.

[0016] In certain example embodiments, the metal element used as an oxidizing agentincludes magnesium (Mg), manganese (Mn), zinc (Zn), copper (Cu), iron (Fe), aluminum (Al), calcium (Ca) and strontium (Sr), along with various combinations of these elements.

[0017] In certain example embodiments, the quantity of the oxidizing agent utilized rangesfrom about 0.05 millimoles to about 60 millimoles for every gram of biomass.

[0018] In certain example embodiments, the acid and oxidizing agent blend is kept attemperatures ranging from about 40°C to about 100°C, and at pressures from about 10 psi to about 500 psi, over a period ranging from about 0.1 hours to about 72 hours.

[0019] In some example embodiments, various gases and organic and inorganic solventvapors are utilized, including nitrogen (N2), oxygen (O2), ozone (O3), argon (Ar), helium (He), ammonia (NH3), nitrogen dioxide (NO2), nitrous oxide (N2O), sulfur dioxide (SO2), sulfur (S), hydrogen (H2), carbon dioxide (CO2), compressed air, etc. and their combinations. These gases serve different purposes depending on the desired requirements of the specific type of cellulose and its derivatives. They provide pressure through inert atmospheres, increases solubility of organic matter in acid, and / or aid in various chemical reactions crucial for production processes depending on the specific physicochemical properties of the final products.

[0020] The pressure inside a reactor could be influenced by the use of a range of solvents invarious ways. In some example embodiments, these could be water, acetone, chloroform, dichloromethane, acetonitrile, n-hexane, methanol, ethanol, acetic acid, 1-butanol, 2-butanole, 2-butanone, t-butyl alcohol, carbon tetra chloride, diethyl ether, etc. and their various combinations. The solvents should be selected based on their volatility, expansion capability, miscibility, etc. The solvents could be used as part of pressure control mechanisms within NOP reactor system. In high-pressure NOP reactions, the use of the preceding solvents could help to regulate and maintain the desired pressure levels.

[0021] In certain example embodiments, various type of pressure vessels could be used,including batch reactor, single- and train-screw extruders, mixer blender, and rotary and fixed bed reactors. In other example embodiment, autoclave, microwave reactor, storage pressure tank, supercritical fluid reactor, etc. or a combination of these apparatuses could be used.

[0022] In some example embodiments, various gases are utilized, encompassing nitrogen,oxygen, argon, helium, nitrogen dioxide, nitrous oxide, compressed air, and their respective combinations.

[0023] In example embodiments, the quantity of the acid component utilized ranges fromabout 10 millimoles to about 300 millimoles per gram of biomass.

[0024] In some example embodiments, the fibers generated mechanical treatments, whichinclude options like sonication, homogenization, cryocrushing, grinding, and steam explosion,as well as their combinations. These mechanical treatments can take place over a duration ranging from about 1 minute to about 6 hours.

[0025] In some example embodiments, the fibers produced are subjected to chemicaltreatments, including alkaline and acid treatments. These chemical treatments can involve substances such as sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), hydrochloric acid (HCl), sulfuric acid (H2SO4), and phosphoric acid (H3PO4), either individually or in combination. The duration of these chemical method spans from about 1 minute to about 12 hours.

[0026] In example embodiments, the oxidized cellulose fibers created can have an averagefiber length ranging from about 10 nanometers to about 10,000 nanometers.

[0027] In example embodiments, the oxidized cellulose fibers generated can have anaverage nominal diameter ranging from about 2 nanometers to about 200 nanometers.

[0028] In example embodiments, the gellable substrate's weight percentage (wt%) canrange from about 0.1% by weight to about 15% by weight.

[0029] In example embodiments, the lignin and hemicellulose content in the gellablesubstrate can range from about 1% by weight to about 15% by weight.

[0030] In example embodiments, the base components or their salts used in the methodsof the example embodiments can include sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), and their combinations and can be used neutralize the NOP effluent produced.

[0031] In certain example embodiments, the production of cellulose-based biogels caninvolve cross-linking with cations found in the neutralized NOP effluent. These cations can be selected from macronutrient and micronutrient groups, such as calcium, magnesium, iron (II), iron (III), zinc, manganese, nickel, aluminum, sodium, potassium, and various combinations of these elements.

[0032] In certain example embodiments, employing compressed gas can enable theremoval of oxidizing agents and can amplify the impact of NOx gas that is generated during the interaction between nitric acid and biomasses.

[0033] The above and other features, elements, characteristics, steps, and advantages ofthe 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

[0034] The patent or application file contains at least one drawing executed in color. Copiesof this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0035] Fig. 1A shows a PANOP reactor system according to an example embodiment of thepresent invention.

[0036] Fig. 1B shows a constructed 1-L PANOP reactor system.

[0037] Fig. 2 is a graph showing the degree of oxidization, determined by potentiometrictitration, of various CMF samples.

[0038] Figs.3A–3D are transmission electron microscopic (TEM) images of carboxylatedCNFs (CNF-J_KN, CNF-J-35, CNF-J-55 and CNF-J-75) obtained from the samples prepared under 1-5 psi (with KNO2), as well as 35 psi, 55 psi, and 75 psi (all without KNO2), respectively. Figs. 3A–3D are in color.

[0039] Fig. 4 shows a deconvoluted X-ray diffraction (XRD) spectra for sample CMF-J-75.

[0040] Fig. 5 shows an X-ray diffraction (XRD) spectra for samples CMF-J_KN, CMF-J-35,CMFf-55, and CMF-J-75 obtained from raw jute fibers.

[0041] Fig. 6 shows FTIR-ATR spectra of raw jute, CMF-J_KN, CMF-J-35, CMF-J-55, and CMF-J-75.

[0042] Fig. 7 shows a solid state 13C CPMAS NMR spectra of CMF-J_KN, CMF-J-35, CMF-J-55,and CMF-J-75 samples.

[0043] Fig. 8 shows the ζ potential analysis of varying CNF samples at a pH of 7.5.

[0044] Fig. 9 shows a UV-vis absorption spectra of CNF-J-35, CNF-J-55, CNF-J-75, and CNF-J_KN samples, where each spectrum is arbitrarily shifted for clarity.

[0045] Fig. 10 shows CMF-J-75 (left), CMF-J_KN (middle), and CMF-J-RT-75_KN (right)samples prepared from raw jute. Fig.10 is in color.

[0046] Fig. 11 shows flow curves of CNF-J_KN, CNF-J-35, CNF-J-55, and CNF-J-75suspensions obtained from jute.

[0047] Fig. 12 shows the degree of oxidation, determined by potentiometric titration, ofCMF samples prepared by PANOP at room temperature. DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0048] Prior approaches for the treatment of biomass to obtain carboxycellulose orcarboxylated cellulose nanofibers (CNF) are disclosed in U.S. Patent No.10,894,838, the entire contents of which is incorporated herein by reference. These methods are generally associated with a Nitro-Oxidation Process (NOP) for producing oxidized cellulose fibers, including both nanofibers and macrofibers, from untreated or raw biomass. The advantages of these processes include simplicity, cost efficiency, minimal chemical usage, and reduced consumption of energy and water. Conventional methods for extracting cellulose from biomass usually involve several steps, such as alkaline treatment (like using NaOH, KOH, etc.), chemical pulping, and further chemical modification processes (for instance, sulfuric acid hydrolysis, TEMPO oxidation). These steps are often necessary to eliminate non-cellulosic components, mainly lignin and hemicellulose, from the biomass. Additionally, previous methods for cellulose extraction and oxidation typically utilize 65% (w / w) nitric acid, posing challenges for large-scale production due to the handling of toxic acids.

[0049] Example embodiments of the present invention include methods for thesimultaneous production of cellulose fibers and liquid fertilizers directly from jute. However, these methods can be applied to various types of other biomasses that include lignocellulose and non-lignocellulose woods, pure cellulose, grasses, phytoplanktons, algal celluloses, tunicate celluloses, and their combinations, as well as protein biomass like cow, chicken, fish, pig, goat, lamb, duck, turkey, prawns, crab, shrimp, lobster, mussels, oysters, scallops, clams, and their combinations, in addition to food and animal waste. The example embodiments of the present invention include methods in which various nitrite salts, nitrate salts, and metal elements that are combined with nitric acid under different pressure conditions using gases, such as compressed air, NOx, N2, CO2, O2, O3, NH3, and their mixtures. Simultaneously, other types of gases could be used, including inert gases such as argon and helium, etc. This combination isused to defibrillate and oxidize raw biomass in a single-step process. In example embodiments, the processes can result in no or significantly reduced by-product waste. The use of compressed gas in example embodiments can eliminate or significantly reduce oxidizing agents and can enhance the effect of NOx gas, which is produced when nitric acid interacts with biomasses. This leads to the formation of oxidized cellulose in the scale of macrofibres, microfibers, and nanofibers, which in some instances are superior to those produced by the standard NOP. The oxidized cellulose fibers and effluent obtained can be utilized in a variety of applications, such as , such as biogel growing media, soilless substrate binding agents, water and nutrient retention agents, wastewater adsorbents, packaging additives, biomedical materials, as well as liquid fertilizers, respectively.

[0050] Besides jute, in some example embodiments, suitable sources of plant biomassencompass a variety of feedstock materials , e.g., palm trees, sugarcane bagasse, corn, wheat, oats, rice, sorghum, oil palms, bamboo, spinifex, coastal bermudagrass, miscanthus, switchgrass, azolla, seaweeds, flax, hemp, ramie, fibers from kenaf stalks and cores, abaca, sisal, pineapple, banana leaves, banana peels, banana fibers, curaua, stalks of lotus leaves, roselle, fibers from seeds and cotton, kapok fibers, fibers from areca nuts, coconuts, potatoes, cabbages, tomatoes, all other vegetables, rubberwood, the Indian screw tree, achira fibers, citrus fruits, soybeans, soybean straws, spent grains, soy hulls, pea hulls, grape pomace, fruit pomace, and their combinations.

[0051] Suitable sources of protein biomass include cow, chicken, fish, pig, goat, lamb, duck,turkey, prawns, crab, shrimp, lobster, mussels, oysters, scallops, clams, and their various combinations.

[0052] Animal wastes that are appropriate to use as a biomass source include cow manure,horse manure, chicken manure, pig manure, and their combinations.

[0053] The food waste that can be utilized as a biomass source can come from any originand may be mixed with any of the previously mentioned biomass sources, including plant biomass, protein biomass, animal waste, and similar materials.

[0054] In example embodiments, the production of cellulose nanomaterials and a nutrient-enriched effluent is achieved by combining various catalytic quantities of oxidizing agents withan appropriate acid, such as nitric acid, under different pressure conditions. The methods of the example embodiments can eliminate or significantly reduce the necessity for large quantities ofNaNO2, KNO2, or similar inorganic compounds as the primary oxidizing agent. Additionally,decreasing the amount of oxidizing agents can lower the costs of scaling up the process by at least 20%.

[0055] The methods of the example embodiments involve extracting the nutrients andoxidizing untreated biomass feedstocks to produce carboxylated cellulose fibers and a nitrogen- enriched effluent. This is achieved by applying nitric acid and leveraging the influence of pressure. The effluent resulting from these processes is characterized by a lower concentration of inorganic elements, attributed to the reduced use of nitric acid and oxidizing agents, and a higher presence of organic element / compounds rich in nitrogen, which provide nutrients essential for plant growth.

[0056] In accordance with example embodiments, there is no need for intensivepretreatment of raw biomass, making the method more economical and energy efficient. The entire method can occur in a single step, beginning with the reaction of biomass waste as the feedstock with specific reaction conditions. In example embodiments, the biomass is treatedwith nitric acid (HNO3) at a desired concentration. While the use of HNO3 is discussed below,alternative acids can be employed, such as phosphoric acid (H3PO4), hydrochloric acid (HCl), sulfuric acid (H2SO4), acetic acid (CH3COOH), hydrobromic acid (HBr), and hydrofluoric acid (HF). Additionally, in some example embodiments, a combination of these acids might be utilized.

[0057] The concentration of acid employed in the example embodiments can range fromabout 5 millimoles to about 500 millimoles per gram of biomass, within manufacturing and / or measurement tolerances. In certain example embodiments, the concentration is specified to be from about 20 millimoles to about 140 millimoles per gram of biomass, within manufacturing and / or measurement tolerances.

[0058] Example embodiments can use various nitrite salts, such as sodium nitrite (NaNO2),potassium nitrite (KNO2), ammonium nitrite (NH4NO2), calcium nitrite (Ca(NO2)2), magnesium nitrite (Mg(NO2)2), barium nitrite (Ba(NO2)2), lithium nitrite (LiNO2), zinc nitrite (Zn(NO2)2),copper(II) nitrite (Cu(NO2)2), and silver nitrite (AgNO2), along with various combinations of these salts.

[0059] Example embodiments can use various nitrate salts, such as sodium nitrate (NaNO3),potassium nitrate (KNO3), ammonium nitrate (NH4NO3), calcium nitrate (Ca(NO3)2), magnesium nitrate (Mg(NO3)2), barium nitrite (Ba(NO3)2), lithium nitrite (LiNO3), zinc nitrite (Zn(NO3)2), copper(II) nitrite (Cu(NO3)2), and silver nitrite (AgNO3), along with various combinations of these salts.

[0060] Example embodiments can use a metal element used as an oxidizing agent, includingmagnesium (Mg), manganese (Mn), zinc (Zn), copper (Cu), iron (Fe), aluminum (Al), calcium (Ca) and strontium (Sr), along with various combinations of these elements.

[0061] In the example embodiments, the oxidizing agent's concentration may range fromabout 0.05 millimoles to about 60 millimoles per gram of biomass, within manufacturing and / or measurement tolerances. Specifically, in example embodiments, the concentration can be from about 2.8 millimoles to about 11.5 millimoles per gram of biomass, within manufacturing and / or measurement tolerances.

[0062] The acid and oxidizing agent in the method might be mixed with the biomassfeedstock at temperatures ranging from about 25°C to about 140°C, within manufacturing and / or measurement tolerances. In some example embodiments, this temperature range can be from about 30°C to about 100°C, within manufacturing and / or measurement tolerances. Additionally, the nitric acid and, if used, potassium nitrite can be in contact with the biowaste for a duration of about 0.1 hours to 72 hours, within manufacturing and / or measurement tolerances. In certain example embodiments, this period can from about 1 hours to about 24 hours, within manufacturing and / or measurement tolerances, while in other example embodiments, the period can be from about 2 hours to about 9 hours, within manufacturing and / or measurement tolerances.

[0063] The results of the methods according to the example embodiments, e.g., a biogelfertilizer (a blend of biogel and fertilizer) or functionalized cellulose nanofibers, often termed as nitro-oxidized cellulose nanofibers (NOCNF), depends on the type of biomass being treated. Forinstance, in the production of biogel fertilizers, the biomass that is treated might include animal waste, food waste, their combinations, and similar materials.

[0064] When the biomass source involves fibrous cellulosic materials, the methods of theexample embodiments yield biodegradable, eco-friendly charged micro- and nano-cellulose derived from the fibers in the biowaste source. This charged micro- and nano-cellulose can take the form of functionalized micro- or nano-fibers, or in some cases, a biogel. The process of ionic gelation of a nanocellulose suspension results in the formation of a biogel.

[0065] In cases where the product of the disclosed methods is fibrous, these fibers canundergo mechanical treatments, including techniques like sonication, homogenization, cryocrushing, grinding, and steam explosion, or a mix of these mechanical treatments. The duration of these additional mechanical-treatment steps can vary, with some example embodiments ranging from about 1 minute to about 360 minutes, within manufacturing and / or measurement tolerances, and in other example embodiments, from about 0.5 hours to about 4 hours, within manufacturing and / or measurement tolerances.

[0066] The fibers generated through the described methods can include oxidized cellulosefibers with an average length ranging from about 10 nanometers to about 10,000 nanometers, within manufacturing and / or measurement tolerances. In certain example embodiments, the length spans from about 100 nanometers to about 1000 nanometers, within manufacturing and / or measurement tolerances. Additionally, these fibers may possess an average nominal diameter between about 2 nanometers and about 100 nanometers, within manufacturing and / or measurement tolerances, with some example embodiments including diameters from about 5 nanometers to about 100 nanometers, within manufacturing and / or measurement tolerances.

[0067] When the biomass source lacks fibrous materials, the outcome of theaforementioned processes or treatments involving biomass with acid and oxidizing agent results in a liquid biowaste effluent. This effluent, containing nutrients like nitrates, and other ingredients can be utilized as a plant’s fertilizer.

[0068] In certain example embodiments, the produced oxidized cellulose fibers can be usedto create a gellable substrate. The fiber suspension's weight percentage (wt%) in this substratemight range from about 0.5% by weight to about 10% by weight, within manufacturing and / or measurement tolerances. In some example embodiments, this range is from about 1% by weight to around 5% by weight, within manufacturing and / or measurement tolerances. Additionally, in some example embodiments, the gellable substrate may contain lignin and hemicellulose, with these components including about 1% by weight to about 25% by weight of the substrate, within manufacturing and / or measurement tolerances.

[0069] In certain example embodiments, the effluent obtained from the methods of theexample embodiments can be neutralized through treatment with a base and / or its corresponding salt. Appropriate bases or their salts can include sodium hydroxide, potassium hydroxide, ammonium hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, and their various combinations.

[0070] In different example embodiments, the cellulose-based biogels created through themethods of the example embodiments can undergo a cross-linking phase. This involves bringing the recovered materials into contact with certain cations. Appropriate cations for this cross- linking can be selected from the macronutrient and micronutrient groups, including calcium, magnesium, iron (II), iron (III), zinc, manganese, nickel, aluminum, sodium, potassium, and various combinations of these.

[0071] As previously mentioned, the biogels resulting from the methods of the exampleembodiments can be employed as fertilizers or as mediums for soilless plant cultivation. The nanocellulose obtained through the nitro-oxidation process (NOP) offers an easily accessible, affordable, and eco-friendly method for transforming biowaste into valuable substances for various agricultural uses, such as water purification, soilless cultivation media, and NPK fertilizer. The methods of the example embodiments can provide an economical, straightforward, and environmentally sustainable methods to treat wastewater and similar waste sources, making them suitable for reuse as fertilizers or materials for soil-free growth.

[0072] The methods can offer several benefits, including but not limited to:^ Reducing or minimally using oxidizing agents and lesser quantities of nitric acid usinghigher pressure benefits, making the process more sustainable and cost-effective (potentially reducing costs by about 10% to about 85%).^ The methods are versatile, applicable to a range of biomasses such as agriculturalorganic waste, food waste, lignocellulosic wood or non-wood biomasses, and animal waste. Additionally, the methods can be completed relatively quickly, with some embodiments taking about 0.5 hours to about 9 hours. ^The effluent produced is nutrient-rich, essential for plant growth, contributing to aclosed-loop system. ^The methods employ acid and a smaller amount of oxidizing agent (includingcatalytic impurities in raw biomass feedstocks) in a single-step process, eliminating the need for additional pretreatment steps like alkaline treatment or chemical pulping, thereby being less energy-intensive, quicker, and more cost-efficient. ^The methods allow for more effective upcycling of biomass due to the significantlylower chemical ratio compared to previous methods using sodium nitrite. ^The products and effluent generated can be utilized in a wide array of applicationssuch as liquid biofertilizers, biogels, wastewater adsorbents, food packaging, biomedical uses, etc. Utilizing food and agricultural waste in these methods forms a closed-loop system where the treated biowastes can be used for regrowing crops or plants, achieving a plant-to-plant cycle.

[0073] To summarize, the described methods are capable of treating various plantbiomasses, protein biomasses, and their combinations. These methods lead to the creation of a nitrogen-enriched effluent and strong biogel materials. These methods can effectively break down non-cellulosic components and can chemically alter the biomass, producing reliable, safe, and useful materials suitable for diverse applications. Such reactions yield a nitrogen-rich effluent and robust biogels. In certain example embodiments, the biogel and effluent produced through this process can be utilized as a medium for soilless plant growth and as a fertilizer.

[0074] Non-restrictive Examples are described below. These Examples are meant forillustrative purposes only and do not confine the scope of the disclosure. Within this context, "room temperature" is defined as a range from about 20°C to about 30°C, within manufacturing and / or measurement tolerances. Furthermore, unless specified differently, measurements like parts and percentages, including those in solution percentages, are based on weight.EXAMPLES 1. Materials and Methods 1.1. Materials

[0075] Untreated jute was bought from Tithi Enterprise (Bangladesh), and microcrystallinecellulose (MCC), having a degree of polymerization between 250-350 anhydroglucose units, (AGU) was purchased from Ingredient Depot (Quebec, Canada). The compositions of the jute sample were characterized earlier, where the contents of cellulose, hemicellulose and lignin were 51 wt%, 11 wt% and 18 wt%, respectively. Ammonium hydroxide (NH4OH) and nitric acid (HNO3, 68-70%) were purchased from VWR Chemicals (PA, USA). Sodium chloride (NaCl), sodium hydroxide (NaOH), and potassium nitrite (KNO2, 97%) were purchased from Fisher Chemical (PA, USA). Potassium hydroxide (KOH, 85%) was obtained from Beantown Chemical (NH, USA), and ethanol (C2H5OH 70%) was purchased from Decon Laboratories (PA, USA). Deionized water (DI) was used throughout the reagent preparation and experimentation. 1.2. ICP-OES Characterization of Raw Jute

[0076] The impurities of raw jute samples were characterized by the inductively coupledplasma-optical emission spectroscopy (ICP-OES) technique using a Thermo Fisher iCAP 6500 instrument (Thermo Fisher Scientific, NY, USA). In this study, 16 scans were collected and then averaged at a group of 4. Concentrations of P, K, Ca, Zn, Cu, B, Se, Y, Cr, Al, Mn, Mg, Mo, Na, S, Si, Ag, As, Cd, Ce, Co, Li, Ni, Pb, Sb, Se, and Ti were determined using the acid digestion protocol as outlined in the standard reference material 2706 from the National Institute of Standards and Technology (NIST). The sample solution was heated in an Environmental Express 35- position 100 mL HotBlock 150 under stirring using an Environmental Express StirBase (Thermo Fisher Scientific, NY, USA). The elemental compositions of raw jute fibers characterized by ICP- OES are summarized as follows. 1.3. PANOP Reactor Design and Carboxylated Cellulose Microfiber (CMF) Preparation

[0077] Fig. 1A shows diagram of the pressure-assisted nitro-oxidation process (PANOP)system including on a polytetrafluoroethylene (PTFE) equipped reactor 1 with a heating / cooling jacket 2, air compressor / gas tank 4, agitator / mixer 5, and scrubber 6 for NOx gas. The PANOP system can also include nitric acid tank 3, feedstock supply 7, pressure gauge 8, thermocouple probe 9, and pressure relief valve 10. Fig.1B shows the photograph of the constructed PANOP reactor system using the 1-L SS-314 reactor (TGYF C 1000, manufactured by Zhengzhou Keda Machinery and Instrument Equipment Co., China) and its associated parts.

[0078] To prepare carboxylated cellulose microfibers (CMFs) using the PANOP setup, thefollowing procedures were taken. First, the pressure relief valve 10 was set at a targeted value (e.g., 3 psi, 35 psi, 45 psi, 55 psi, 65 psi, 75 psi, respectively) to ensure the reaction took place at a constant pressure condition. Then, 20 g of the feedstock sample (jute or MCC) was loaded into the PTFE lined SS-314 reactor 1. Subsequently, 280 mL of 50% HNO3(v / v) were slowly added to the reactor 1. After pressurized using a compressed air gas tank 4 (the input pressure set at a value slightly lower the relief valve pressure), the system was carefully checked for leakage to ensure that the system was completely sealed. The agitator 5 was then turned on to initiate the mixing at a 100 rpm rate, and the reactor temperature was raised to 50oC slowly. Finally, a high-pressure dosing pump was used to introduce the KNO2 solution (19.2 g dissolved in 20 mL of water) into the reactor 1.

[0079] In PANOP operation, the total reaction time was set for 9 h. The excessive reactorpressure was captured by a NOx scrubber 6, containing 15-20% KOH solution. To quench the PANOP reaction, 250 mL of DI water was slowly added into the reactor 1, where the resulting slurry was poured into a 2000 mL beaker for further processing. A vacuum filtration unit withWhatman filter paper (pore size 15 ^m-18 ^m) was used to separate CMF and the acidiceffluent. The effluents were neutralized using KOH or NH4OH to achieve a desired NPK ratio, where the products were used as liquid fertilizers. The resulting CMF was washed with deionized (DI) water until its pH value reached 3.0. 1.4. Yield and DO Determination of Carboxylated CMF

[0080] To calculate the yield (%) of carboxylated CMF produced by the PANOP system, 40mL of the CMF suspension (at pH = 3.0) was poured into a 50 mL of Falcon tube, which was thencentrifuged at 9000 rpm for 5 min in a Hermle centrifuge (model Z 326, Benchmark Scientific, NJ, USA). The solid CMF residues were then separately and freeze-dried using a BenchTop Manifold Freeze Dryer (model BT48A, Millrock Technology, NY, USA) for 24-48 h. Following the completion of the freeze-drying process, the dried CMF sample was weighed to calculate the percentage yield using Eq.1, %Yield = MFD ∗V i40∗M *100 (1)where MFDis the mass of the freeze-driedsuspension (mL), Miis initial mass of the biomass feedstock (jute or MCC, g).

[0081] To determine the DO value of CMF, potentiometric titration was carried out on thefreeze-sample fiber using a Hanna potentiometric titrator (model HI901, Hanna Instruments, RI, USA) to determine the carboxylate content through the titration curve approach. Specifically, a sample weighing between 0.4-0.5 g was placed in a 200 mL beaker along with 75 mL of DI water, 5 mL of 0.01 M HNO3and 5 mL of 0.01 M NaCl. The mixture was stirred continuously (using a magnetic stirring bar) overnight at a speed of 400 rpm. After reaching the end point of the titration, the DO was calculated using the following Eq.2: DO (mmol / g) = M NaOH × ΔV(2) MFDwhere M is concentration of NaOH, ΔV is the NaOH volume difference of NaOH between the sample and blank (mL), MFDis the mass of the sample (g). A blank sample including of 5 mL of 0.01 M HNO3and 5 mL of 0.01 M NaCl was also run by the titrator. 1.5. Defibrillation of Carboxylated CMF to Produce Carboxylated CNF

[0082] Carboxylated CNF suspensions were produced by mechanically defibrillating CMFthrough a homogenizer (GEA model Panda Plus 2000, GEA Group, Germany). Before homogenizing the CMF sample, its pH value was first adjusted from 3.0 to 6.0 using 0.05 M of NH4OH. This step ensured the deprotonation of carboxyl group (-COOH) to carboxylate group - COO- (pKa ~ 3.5). The CMF suspension (pH = 6.0) was undergone two cycles of homogenization at a pressure between 400 bars to 500 bars to produce a homogeneous carboxylated CNF suspension.1.6. Characterizations of CMF and CNF

[0083] TEM equipped with a FEI Tecnai G2 Spirit BioTWIN Instrument (Thermo FisherScientific, MA, USA) at an acceleration voltage of 120 kV was used to characterize the structure and dimensions of the carboxylated CNF. TEM samples were prepared by placing ~ 10 μL of 1 mg / mL carboxylated CNF suspension on carbon coated copper grids followed by staining with uranyl acetate (1%). Then XRD was carried out using the Rigaku MiniFlex 600 Benchtop equipment (Rigaku Corp., Japan) at the 2θ angle from 10° to 100° and a scanning rate of 10° min–1to determine the crystallinity index (CI) of the CMF. The Fourier Transform Infrared (FTIR) spectroscopy analysis was carried out using a PerkinElmer Spectrum One instrument (PerkinElmer, MA, USA). Samples were examined in the ATR mode from 900 to 3750 cm-1at aresolution of 4 cm -1, where six scans per sample were taken. Solid state 13C cross-polarizationmagic angle spinning (CP-MAS) nuclear magnetic resonance (NMR) spectroscopy was utilized to characterize the structure of the biomass fibers and the resulting CMF employing a Bruker Ultra shield 500WB plus NMR spectrometer (Bruker Corp., MA, USA). The CI of the sample was also estimated by assessing the ratio of areas representing crystalline and amorphous cellulosesignals in the 13C CP-MAS NMR spectrum. The zeta potential measurements were performedusing a Malvern Zetasizer Nano ZS instrument (Malvern Panalytical, MA, USA). The sample was characterized in three cycles with each cycle including twenty measurements. The ultraviolet- visible (UV-Vis) spectrophotometry analysis were performed using Thermo Scientific Genesys 10S UV-Vis spectrophotometer (Thermo Fisher Scientific, NY, USA). The UV spectra for each sample were collected from 200 nm to 800 nm in a quartz cuvette. Finally, the rheological measurements of CNF suspensions were performed using a Discovery Hybrid Rheometer (HR-3, TA Instruments, DE, USA) where the sample was sandwiched in a parallel plate geometry (diameter = 40 mm, gap = 1 mm). All the measurements were conducted at 25°C with a 10 min stabilization period to minimize the solvent evaporation. The flow sweep tests were performed at a shear rate range between 0.1 s-1- 400.0 s-1with 5 points per decade. 2. Results 2.1. Pressure Effect on DO Value of CMF

[0084] In Table 1, two different feedstocks: jute and MCC, were chosen to investigate theeffects of pressure as well as the added reagent (KNO2) on the DO value of CMF. The motivation for selecting these two feedstocks is because jute contains the cellulose content only around 50-60% (and metal impurities), while MCC contains almost only cellulose (~100%). We hypothesize that pure MCC and HNO3will lead to only acid hydrolysis of cellulose, while the jute and HNO3will result in acid hydrolysis and oxidation of cellulose. In Table 1, it is seen that the NOP with only a small amount of added pressure (1 psi-5 psi for jute and 15 psi for MCC) using the same amount of KNO2yielded a higher DO value for jute (1.25 mmol / g for CMF-J_KN) than that for MCC (1.11 mmol / g, CMF-M-15_KN). This is because the presence of impurities in jute (i.e., lignin and metal components, such as aluminum, iron, and magnesium as seen in Table 2) can also react with HNO3and produce nitrosonium ions (NO+) as an effective cellulose oxidation agent. This was visible during the NOP reaction, which produced a deeper red-brown color, indicative of the production of NO2, for jute than that for MCC. The yield of CMF-J_KN was 45% and the yield of CMF-M-15_KN was 94% (Table 3), which are very close with their starting cellulose compositions. Table 1. Summary of PANOP reacƟon condiƟons and the DO values of resulƟng CMFs.Sample name Feedstock Feedstock ReacƟon condiƟons ^^^^^^^^,DO, Weight, g g mmol / g 50% React. React. React. HNO3, Time, h temp., °C Press., mL psi CMF-J_KN Jute 20 280 9 50 ~ 1-5 19.2 1.25CMF-J-35 Jute 20 280 9 50 35 - 1.89CMF-J-45 Jute 20 280 9 50 45 - 2.38CMF-J-55 Jute 20 280 9 50 55 - 2.43CMF-J-65 Jute 20 280 9 50 65 - 2.30CMF-J-75 Jute 20 280 9 50 75 - 1.98CMF-J-75-KN Jute 20 280 9 50 75 19.2 2.23CMF-M-MCC 20 280 9 50 15 19.2 1.1115_KN CMF-M-MCC 20 280 9 50 75 19.2 3.6075_KN CMF-M-75 MCC 20 280 9 50 75 - 0.12Table 2. Elemental composiƟons of raw jutefibersJute nutrients Al Ca Fe K Mg Mn Mo Na P S Si Znmg nutrient / g jute 0.293 4.393 0.525 0.297 0.516 0.023 0.000 0.047 0.153 0.364 0.300 0.011 Table 3. PANOP reacƟon parameters for treaƟng jute and MCCfiber feedstocks (20 g) using 280mL of 50% HNO3 and 9 h reacƟon Ɵme; and the yield and degree of oxidaƟon (DO) in the resulƟng carboxylated cellulose microfibers (CMF) (KN: KNO2, RT: room temperature) ReacƟon DO Sample name Feedstock condiƟonKNO (g) Yield%(mmol / g)2(°C / psi) CMF-J_KN Jute 1.25 50 / <1-5 19.2 45CMF-J-35 Jute 1.89 50 / 35 - 42CMF-J-45 Jute 2.38 50 / 45 - 44CMF-J-55 Jute 2.43 50 / 55 - 41CMF-J-65 Jute 2.30 50 / 65 - 37CMF-J-75 Jute 1.98 50 / 75 - 38CMF-J-75_KN Jute 2.23 50 / 75 19.2 43CMF-M-15_KN MCC 1.11 50 / 15 19.2 94CMF-M-75_KN MCC 3.60 50 / 75 19.2 95CMF-M-75 MCC 0.12 50 / 75 - 96CMF-J-RT Jute 1.15 RT / 3 - 58CMF-J-RT-35 Jute 0.88 RT / 35 - 59CMF-J-RT-45 Jute 0.82 RT45 - 54CMF-J-RT-55 Jute 0.94 RT / 55 - 61CMF-J-RT-65 Jute 0.83 RT / 65 - 54CMF-J-RT-75 Jute 0.74 RT / 75 - 62CMF-J-RT-35_KN Jute 1.26 RT / 35 19.2 55CMF-J-RT-45_KN Jute 0.86 RT / 45 19.2 60CMF-J-RT-55_KN Jute 1.00 RT / 55 19.2 58CMF-J-RT-65_KN Jute 0.85 RT / 65 19.2 55CMF-J-RT-75_KN Jute 2.10 RT / 75 19.2 53CMF: cellulose microfibers produced by the pressure-assisted nitro-oxidation process; J: raw jute feedstock; M: microcrystalline cellulose (MCC) feedstock; RT: room temperature; KN: KNO2; DO: degree of oxidation.

[0085] In the NOP treatment of raw jute without KNO2, the increase of pressure (from 35psi to 55 psi) is found to enhance the DO value of CMF (e.g., 1.89 mmol / g for CMF-J-35, and 2.43 mmol / g for CMF-J-55, also shown in Fig.2). The pressure here includes both NOx gases created by the HNO3reacted with the metal impurities as well as the compressed air, where the latter is used to modulate the total pressure. The increase in DO can be explained by the enhanced dissolution of NOx gases in the aqueous solution according to the Le Chatelier principle, thus increasing the NO+concentration leading to a higher degree of cellulose oxidation. However, the further increase in pressure (i.e., 65 psi and 75 psi) shows that the DO value becomes lower (DO = 2.30 mmol / g for CMF-J-65 and DO = 1.98 mmol / g for CMF-J-75). This may be explained by two possibilities. (1) The increase in pressure disfavors formation of new NOx gases, leading to an equilibrium which does not yield a sufficient concentration of HNO2. (2) The increase in pressure leads to an increase in the rate of depolymerization of cellulose; carboxylated fibers that depolymerize will dissolve into the solvent and lead to a decrease in carboxylic acid functionalization across the cellulose chains.

[0086] The MCC sample cannot be oxidized without the assistance of KNO2, supporting themechanistic claim that NOx gas formation (leading to HNO2 production) is necessary foroxidation to occur. For example, the DO value was only 0.12 mmol / g for CMF-M-75 (Table 1). In the presence of KNO2, MCC showed the DO value is increased with pressure (1.11 mmol / g for CMF-M-15_KN and 3.60 mmol / g for CNF-M-75_KN). The DO value of 3.6 mmol / g of CMF derived from MCC is significantly higher than those values reported in previous studies. Interestingly, the yields for all CMFs from MCC were quite high (~ 95%), indicating the samples suffered almost no degradation.

[0087] The pressure results for jute are quite different from those for MCC. In the presenceof KNO2, CMF produced from jute also showed an increase in DO with pressure: 1.25 mmol / g for CMF-J_KN and 2.23 mmol / g for CNF-J-75_KN. However, this increase was much smaller than those of CMFs (CMF-M-15_KN and CNF-M-75_KN) obtained from MCC (Table 1). Oneexplanation could be that the lack of impurities in MCC (i.e., lignin, hemicellulose, proteins, metals) resulted in less side reactions with NO+, resulting in an increase in nitrosation during the reaction. Additionally, MCC chains are immediately exposed to reactants, while all the jute cellulose must first defibrillate and hydrolyze before reactive cellulose fibers are exposed to be oxidized; the increase in reaction time likely resulted in a more substantial increase in DO for MCC compared to jute. 2.2. Morphology, Crystalline Structure and Crystallinity of CMF or CNF

[0088] TEM was used to characterize the morphology of carboxylated CNFs, defibrillated byhomogenization of CMFs, to investigate their morphology and fiber dimensions. Figs.3A–3D show TEM images of 4 CNF samples (CNF-J_KN (Fig.3A), CNF-J-35 (Fig.3B), CNF-J-55 (Fig.3C), and CNF-J-75 (Fig.3D)) obtained from samples CMF-J_KN, CMF-J-35, CMF-J-55, and CMF-J-75, respectively. It is seen that CNF-J-75 produced at the highest pressure (75 psi) represents very well dispersed nanofibers compared to CNF-J_KN produced at the atmospheric pressure. This can be explained by the higher DO value of CMF-J-75 (i.e., more -COOH groups or a higher amount of surface charges), resulting in greater repulsion between the fibers, which helps to separate them more efficiently into nanoscale fibrils. The typical width of CNF-J-75 nanofibers is ranged between 3 nm–5 nm, whereas that of CNF-J_KN is 10 nm–15 nm, suggesting the formation of fiber aggregation in CNF-J_KN. It is also seen that the increasing pressure in NOP decreases the fiber length, which supports our earlier argument. Furthermore, CNFs produced from 35 psi and 55 psi showed almost the same nanofiber morphology with a similar fiber width between 4 nm–8 nm.

[0089] XRD analysis was used to evaluate the pressure effect of NOP on the crystallinestructure and degree of crystallinity of selected CMF samples, and the results are summarized in Table 4. The degree of crystallinity was determined by the peak deconvolution of the XRD profile, where the analysis for CMF-J-75 is illustrated in Fig.4. In the XRD profile of CMF-J-75, several crystalline peaks at 2θ values of 15.32°, 16.96°, 21.27°, 23.10° and 35.04°, corresponding to theplanes of (110), (1ī0), (120), (200), and (040) of the cellulose I structure (resembling the native cellulose in raw jute), and a broad background peak at 20.67°,corresponding to the amorphous phase of cellulose, are seen. In this analysis, all peaks weredescribed by Gaussian functions and the fitted peaks achieved very high coefficients of determination (R2> 0.995). The crystallinity index (CI) was determined by using the followingequation (3), where ICr represents the sum of the peak areas associated with the (110), (1ī0),(120), (200), and (040) planes, and Iamorphous represents the peak area of the amorphous phase(2θ = 20.67).^^^^ = ^ ^^^^^^^^^^^^+^^^^^^^^^^^^ℎ^^^^^^൨ ^^ 100% (3)Furthermore, the crystallite size (L) perpendicular to the fiber direction was estimated using the Scherrer equation: L = kλ / (βcosθ), where k is 0.9, λ (X ray wavelength) is 0.154 nm, and β represents the width of the 200 reflection (the most dominant crystal peak) at the 2θ value of 23.10°.

[0090] Fig. 5 illustrates the XRD profiles of CMF-J_KN, CMF-J-35, CMF-J-55, and CMF-J-75samples, where all profiles exhibit the cellulose I structure with no changes in peak positions. This indicates that the structure of cellulose remains unchanged after oxidation under the applied pressure conditions (35 psi–75 psi). In Table 4, it is seen that both crystal index and apparent crystal size (perpendicular to the chain for fiber axis) of sample CMF-J_KN are larger than those of CMFs produced at higher pressures (i.e., 35 psi, 55 psi, and 75 psi). This is consistent with previous results of DO values and TEM observations, supporting the notion that pressure can enhance the oxidation conditions and increase the solubility of oxidation-induced degraded component. The combined effect of oxidation and dissolution can be used to explain the observation in Table 4 that the apparent crystal size increases with pressure (as smaller nanofiber / fragments are lost during washing or become soluble in the effluent), and the residual CMF has a lower crystallinity index at high pressure. It is seen that pressure can facilitate the oxidation process to convert hydroxyl groups into carboxyl groups on both outer and internal surfaces of microfibers (including aggregation of nanofibers), enabling nanofiber defibrillation and breakage simultaneously under mechanical forces.Table 4. Crystallinity index and apparent crystallite size of CMF samples extracted from jute.Samples no. Apparent Crystallite Size (nm) Crystallinity Index (CI) (%)CMF-J_KN 3.53 71.14CMF-J-35 3.18 66.10CMF-J-55 3.21 66.38CMF-J-75 3.33 65.98on

[0091] The FTIR-ATR spectroscopy was performed to analyze the chemical functionality onraw jute as well as CMFs obtained through varying NOP conditions, and the results are depicted in Fig.6. It is seen that the spectrum of raw jute fibers exhibit several characteristic peaks of cellulose: 3333 cm−1due to the O–H stretching and 2922 cm−1due to the C–H symmetrical stretching from the cellulose moiety; 1524 cm−1due to the C=C aromatic symmetrical stretching from the lignin component; and 1469, 1249, and 819 cm−1related to the xylan and glucomannan units in hemicellulose. Upon oxidation, some hydroxyl groups are converted into the carboxyl groups. This is seen by the slight decrease in the C–H stretching peak at 2922 cm−1and the notable increase in the carboxyl group (COOH) at 1731 cm−1, confirming the oxidation of the anhydroglucose units at the C6 position. The increase of the 1731 cm-1peak coincides with the increase in DO at a higher pressure (see Table 1). Furthermore, the peaks attributed to the hemicellulose and lignin components at 1469, 1249, 819, and 1524 cm−1are significantly reduced or almost absent in the spectra of CMFs produced at 35 psi, 55 psi, and 75 psi.

[0092] Solid-state 13C CPMAS NMR spectroscopy was also performed on these four CMFsamples to obtain complementary structural information, and the results are depicted in Fig.7. In Fig.7, the NMR spectra indicate the corresponding carbon atoms of the anhydro glucose unit (the building block of cellulose chains). The distinct peak at 171 ppm represents an oxidized form of C6 (COOH). The increase of this peak intensity from CMF-J-35 to CMF-J-75 as compared to CMF-J_KN clearly suggests enhanced oxidation, which is supported by the relatively high DO values in Table 1. This observation is also consistent with the FTIR-ATR analysis discussedearlier. In the NMR spectra of CMFs, the peak between the 60 ppm and 70 ppm chemical shift is due to the C6 carbon linked to the -OH group; the dominant peak between the 70 ppm to 80ppm chemical shift is due to the C2, C3, and C5 carbons; the peaks at ∼88 ppm and 83 ppmchemical shifts are due to the crystalline and non-crystalline phase, respectively, of the C4carbon; the peak at ∼93 ppm is due to the C1 anomeric carbon at the reducing end of thecellulose chain; and the peak between 100 ppm to 105 ppm can also be assigned to the C1 carbon. In Fig.7, the intensity of the 93 ppm peak (due to the reducing carbon end group) increases with pressure, supporting the notion that CMF degrades at high pressure. It is seenthat the CMF-J-35, CMF-J-55, and CMF-J-75 exhibit more prominent non-crystalline areas forboth C4 and C6 carbons when compared to that of CMF-J_KN. Additionally, the crystalline peak of the C4 carbon at 88 ppm is found to decrease in intensity with the increase in pressure. Similarly, the peak intensity at around 65 ppm, representing both crystalline and amorphous regions of the C6 carbon, also displays a decrease with increasing pressure. 2.4. Surface Charge of CNF

[0093] The zeta (ζ) potential measurements were carried out to determine the surfacecharge of carboxylated CNF samples in water, obtained by defibrillation of CMF suspensions. The ζ potential is a parameter to indicate the surface charge of the colloidal particle and can be used to determine the stability of CNF in suspension. The results of the ζ potentials for varyingCNF samples are shown in Fig. 8. It is seen that the ζ -potential values for most CNF samples arebelow -50 mV (except for CNF-J-75), and it appears to increase (towards the negative value)with the increasing pressure. Overall, the ζ -potential correlates well with the DO value in Table1. The higher negative ζ -potential indicates the greater tendency to form a stable colloidalsuspension due to stronger electrostatic repulsive forces between CNFs. This conclusion is also consistent with the TEM observations in Fig.3, where CNFs become more aggregated with lessnegative ζ -potential values.2.5. Lignin Content Comparison between CNFs

[0094] The UV-vis spectroscopy was performed to compare the lignin content of varyingCNFs. This approach is not an absolute method that can precisely determine the lignin content on CNF as by the acid hydrolysis method. However, this approach can provide a quickcomparison regarding the residual lignin content on CNF prepared under different PANOP conditions. The UV-VIS spectra of four different CNF suspensions (CNF-J_KN, CNF-J-35, CNF-J-55 and CNF-J-75) are shown in Fig.9 (the spectra are shifted vertically for the ease of comparison). These spectra were taken from the CNF suspension with a concentration of 0.045%, where the absorbance at 280 nm was used as the reference region as which is commonly linked to the lignin component. It was found that CNF-J_KN showed a higher absorbance value at 280 nm than CNF samples prepared under pressure (i.e., CNF-J-35, CNF-J-55, and CNF-J-75), indicating that CNF-J_KN has a relatively higher lignin content. The low absorbance values (at 280 nm) for CNF-J-35, CNF-J-55, and CNF-J-75 indicate that these samples all have a low lignin content. This further confirms that pressure facilitates the delignification process of raw jute. Such a notion is also supported by the color appearance of the CMF sample as shown in Fig.10, where CMF-J-75 exhibits the whitest color indicative of a low lignin content. 2.6. Viscosity Analysis of CNF Suspensions

[0095] Rheological experiments of CNF suspensions (at 0.45 wt%) with different DO valueswere carried out to evaluate the effect of pressure on the aspect ratio of CNF. Fig.11 shows their viscosity profiles as a function of shear rate for four different CNFs (CNF-J_KN, CNF-J-35, CNF-J-55, and CNF-J-75). It is seen that all CNF suspensions exhibit a shear thinning behavior. The viscosity of CNF-J_KN (DO = 1.25 mmol / g and yield = 45% in CMF, Table 3) displays the highest values, followed closely by that of CNF-J-35 (DO = 1.89 mmol / g, yield = 43% in CMF). Judging by the similar yields of their CMFs (45% vs.43%), we conclude that the fiber lengths of CNF-J_KN and CNF-J-35 are similar, where little fiber degradation takes place. The decrease in viscosity can be attributed to the higher DO value of CNF-J-35, resulting in greater repulsion among the nanofibers leading to reduction in fiber entanglements. The viscosity profiles of CNF-J_55 (DO = 2.43 mmol / g and yield = 41%) and CNF-J-75 (DO = 1.98 mmol / g, yield = 38%) are substantially lower than those of CNF-J_KN and CNF-J-35, which can be attributed to the degradation of fiber length resulting in a lower aspect ratio. The cellulose degradation in these two samples is supported by their lower yields (38% and 41%). The viscosity of CNF-J-75 is higher than that of CNF-J_55. Again, this can be explained by the higher DO value of CNF-J_55,which leads to greater repulsion between the nanofibers and reduction in entanglements of the fiber network. 2.7. PANOP at Room Temperature

[0096] The pressure effect on the DO value and the yield of CMF produced by PANOP atroom temperature was also investigated, with and without the presence of catalytic KNO2. The DO and yield results along with the PANOP reaction parameters are illustrated in Table 3. From this table, the degree of oxidation (determined by potentiometric titration) of the CMF sample is plotted again the applied pressure in Fig.12. It is seen that without the presence of KNO2, PANOP still exhibits some efficiency on the oxidation of raw jute, resulting in a DO value around 0.8 mmol / g independent of the applied pressure. Judging from the CMF yield (54% - 62%) and the compositions of raw jute (cellulose ~ 51 wt%, hemicellulose ~ 11 wt% and lignin ~ 18%), using PANOP at room temperature cannot completely remove the lignin and hemicellulose components (i.e., the pulping process is incomplete) with and without the addition of KNO2. However, the reaction condition of PANOP at room temperature can still produce NO2, that can also create carboxylate groups on cellulose, lignin, and hemicellulose. At 75 psi, the PANOP reaction in the presence of KNO2created a high DO value (2.1 mmol / g) and a yield (53%) that is close to the cellulose content (51%) of raw jute. This indicates that the reaction condition at 75 psi is approaching to a fully delignification state and can simultaneously achieve a high degree of oxidation on cellulose. Nevertheless, the residual lignin content is still visible as seen in the yellow appearance of the CMF-J-RT-75_KN sample (Fig.10). 3. Summary of the Examples

[0097] The effect of pressure on the nitro-oxidation process to produce carboxylates CNFwas investigated using two model feedstocks MCC for the study of cellulose oxidation, and raw jute for the study of combined pulping (delignification) and cellulose oxidation processes. It was found the increasing pressure generally enhances the dissolution of NOx (produced by the complex reactions between HNO3, KNO2, metallic impurities in the feedstock (e.g. aluminum, iron and magnesium), H2O and O2), and increases the generation of nitrosating species as an effective oxidizing agent. Using MCC feedstock, the NOP-produced cellulose fibers (75 psi, 50oC and KNO2) displayed a very high DO (3.6 mmol / g); however, cellulose fibers produced under thesame condition using raw jute only exhibited an intermediate degree of oxidation (2.23 mmol / g). This is because the enhanced production of NO+species, not only promotes pulping, but also induces cellulose degradation (resulting in the dissolution of highly oxidized cellulose segments and thus a low yield). Finally, the NOP reaction at room temperature significantly retards the pulping and cellulose oxidation processes; however, the increase in pressure seems to impose a similar effect as raising the temperature.

[0098] It should be understood that the foregoing description is only illustrative of thepresent 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

WHAT IS CLAIMED IS:

1. A method of processing a feedstock, the method comprising: mixing the feedstock with an oxidizing agent and an acid mixture, including nitric acid,with a concentraƟon higher than 20% v / v to form a mixture;maintaining the mixture at a temperature in a range from about 25°C to about 100°C and a pressure between about 10 psi and about 750 psi for about 0.1 hours to about 72 hours; and isolaƟng processedfiber residues and effluent; wherein the feedstock including at least one of a plant biomass, a protein biomass, or a combinaƟon thereof.

2. The method of claim 1, wherein the plant biomass is selected from lignocellulosic wood, non-lignocellulosic wood, lignocellulose, pure cellulose, grass, phytoplankton, algaecellulose, tunicate cellulose, or a combinaƟon thereof.

3. The method of claim 2, wherein the plant biomass is sourced from jute, palm trees, sugarcane bagasse, corn, wheat, oat, rice, sorghum, oil palm, bamboo, spinifex, coastal bermudagrass, miscanthus, switchgrass, azolla, seaweed,flax, hemp, ramie, kenaf stalkfiber, kenaf core, abaca, sisal, pineapple, banana leaves, banana peels, bananafibers, curaua, lotusleaf stalks, roselle, seed hairfiber, coƩonfiber, kapokfiber, areca nutfiber, coconut, potato,cabbage, tomato, vegetable, rubberwood, Indian screw tree, achirafiber, citrus, soybean,soybean straw, spent grain, soy hull, pea hull, grape pomace, fruit pomace, or a combinaƟonthereof.

4. The method of claim 1, wherein the protein biomass is selected from cow, chicken, fish, pig, goat, lamb, duck, turkey, prawns, crab, lobster, shrimp, mussels, oysters, scallops,clams, or a combinaƟon thereof.

5. The method of claim 1, wherein the protein biomass includes cow manure, horsemanure, chicken manure, pig manure, food waste, or a combinaƟon thereof.

6. The method of claim 1, wherein the acid mixture further includes phosphoric acid, hydrochloric acid, sulfuric acid, aceƟc acid, hydrobromic acid, hydrofluoric acid, or a combinaƟon thereof.

7. The method of claim 1, wherein the oxidizing agent includes a nitrites-based salt selected from sodium nitrite (NaNO₂), potassium nitrite (KNO₂), ammonium nitrite (NH₄NO₂), calcium nitrite (Ca(NO₂)₂), magnesium nitrite (Mg(NO₂)₂), barium nitrite (Ba(NO₂)₂), lithium nitrite (LiNO₂), zinc nitrite (Zn(NO₂)₂), copper(II) nitrite (Cu(NO₂)₂), silver nitrite (AgNO₂), or a combinaƟon thereof.

8. The method of claim 1, wherein the oxidizing agent includes a nitrates-based salt selected from sodium nitrate (NaNO3), potassium nitrate (KNO3), ammonium nitrate (NH4NO3), calcium nitrate (Ca(NO3)2), magnesium nitrate (Mg(NO3)2), barium nitrite (Ba(NO3)2), lithium nitrite (LiNO3), zinc nitrite (Zn(NO3)2), copper(II) nitrite (Cu(NO3)2), and silver nitrite (AgNO3), ora combinaƟon thereof.

9. The method of claim 1, wherein the oxidizing agent includes a nitrates-based salt that includes a metal element selected from magnesium (Mg), manganese (Mn), zinc (Zn), copper(Cu), iron (Fe), aluminum (Al), calcium (Ca), stronƟum (Sr), or a combinaƟon thereof.

10. The method of claim 1, wherein a concentraƟon of the acid mixture ranges fromabout 10 mmol to about 300 mmol per gram of biomass.

11. The method of claim 1, wherein an amount of the oxidizing agent is in a range from about 0.01 moles per gram of biomass to 0.25 moles per gram of biomass.

12. The method of claim 1, wherein a pressurizing medium includes nitrogen (N2), oxygen (O2), ozone (O3), argon (Ar), helium (He), ammonia (NH3), nitrogen dioxide (NO2), nitrous oxide (N2O), sulfur dioxide (SO2), sulfur (S), hydrogen (H2), carbon dioxide (CO2), compressed air,and a combinaƟon thereof.

13. The method of claim 1, wherein the mixture is maintained at a temperature in a range from about 40°C to about 100°C for about 0.5 hours to about 72 hours.

14. The method of claim 1, further comprising mechanically processing the processedfiber residues by sonicaƟon, homogenizaƟon, cryocrushing, grinding, steam explosion, or acombinaƟon of thereof.

15. The method of claim 14, wherein the mechanically processing lasts from about 1 minute to about 360 minutes.

16. The method of claim 15, wherein the processedfiber residues include oxidized cellulosefibers with an average length of between about 10 nm and about 10,000 nm.

17. The method of claim 15, wherein the processedfiber residues include oxidized cellulosefibers with an average diameter ranging from about 2 nm to about 100 nm.

18. The method of claim 1, wherein the processedfiber residues include oxidized cellulosefibers; and the method further includes creaƟng a gellable substrate from the oxidized cellulose fibers; and the gellable substrate includes between about 0.1 wt% and about 20 wt% of the oxidized cellulosefibers.

19. The method of claim 18, wherein the gellable substrate includes lignin and hemicellulose in amounts ranging from about 1% by weight to about 20% by weight.

20. The method of claim 1, further comprising neutralizing the effluent by base components or their salts selected from sodium hydroxide, potassium hydroxide, ammoniumhydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, or a combinaƟon thereof.

21. A method of making cellulose-based biogels comprising cross-linking the processedfiber residues of claim 1 with one or more caƟons selected from macronutrient andmicronutrient groups including calcium, magnesium, iron (II), iron (III), zinc, manganese, nickel,aluminum, sodium, potassium, or a combinaƟon thereof.

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