Nitro-oxidative carboxylation of non-plant biomass for nanocellulose and co-products

Abstract

Carboxylated cellulosic nanofibers (CNFs) having a degree of oxidation (DO) from about 0.5 mmol·g⁻¹–about 2.5 mmol·g⁻¹, wherein the CNFs are obtained by treating a non-plant biomass feedstock using a nitro-oxidation process (NOP), and wherein the DO is measured on washed oxidized cellulose obtained by the NOP at a pH greater than about 2.5.

Description

Attorney Docket No. 201291.11. PCTNITRO-OXIDATIVE CARBOXYLATION OF NON-PLANT BIOMASS FOR NANOCELLULOSE AND CO-PRODUCTSCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Patent Application No. 63 / 716,060 filed on November 4, 2024. The entire contents of this application are hereby incorporated by reference.BACKGROUND OF THE INVENTION1. Field of the Invention

[0002] The present invention relates to nitro-oxidized cellulosic nanofibers (NOCNF) and to processes for producing the same by a nitro-oxidation process (NOP) - specialized oxidation / carboxylation methods tailored to convert a broad range of non-plant biomass materials into nanocellulose and other valuable carboxylated cellulosic derivatives, while simultaneously generating a nutrient-rich effluent suitable for recovery or reuse.2. Description of the Related Art

[0003] Reliance on forestry or non-wood plants (such as cotton) as feedstocks for NOPs constrains geography, cost, and sustainability, where the treatments to remove lignin, hemicellulose, and extractives— often referred as pulping treatments— add operational costs and produce waste. Many regions possess abundant non-plant biomasses— animal manure, insect biomass, aquatic biomass, agricultural and food-processing residues, livestock waste (e.g. paunches from slaughterhouses), and mixed municipal organic waste— that are rich in polysaccharides but remain underutilized due to heterogeneity and contaminants (ash, proteins, lipids, salts, and microbial content). Non-plant feedstocks often contain proteins, mineral ash, residual ammonia or nitrates, fats, and diverse carbohydrates (e.g., chitin / chitosan, peptidoglycans) that interfere with controlled cellulose oxidation and subsequent fibrillation.

[0004] Known NOPs, involving the use of nitric acid with dual dissolution (of organic matter) and oxidizing ability, primarily focus on the transformation of plant-based biomass to carboxylated nanocellulose. However, plant biomass differs significantly from non-plantbiomass, which typically has higher nitrogen, lipid, and protein content, along with unique chemical compositions and structural properties. These differences reduce the effectiveness of known NOPs when applied to non-plant biomass. Conventional routes to produce carboxylated nanocellulose typically start from purified, plant-derived cellulose (e.g., wood pulp, cotton linters) and employ mechanical fibrillation and / or chemical oxidations such as TEMPO- mediated oxidation, periodate / chlorite sequences, or sulfuric-acid hydrolysis to generate surface charge to facilitate the fibrillation process. These known methods are costly as they involve multiple steps and the spent chemicals and processed water need to be recycled, reused, and post-treated. For example, the TEMPO-mediated oxidation process requires expensive oxidizing agents and strict pH control; the periodate / chlorite approach involves toxic chemicals and the effluent must be treated to ensure environmental safety; concentrated sulfuric-acid hydrolysis generates sulfate ester groups that can compromise thermal stability and requires acid-recovery operations. These known processes are relatively ineffective to process lignocellulosic feedstocks with high impurity or nitrogenous components, leading to low degree of cellulose oxidation (low carboxyl content), incomplete cellulose fibrillation, or excessive degradation. Conventional pretreatments (alkali cooking, bleaching, enzymatic steps, etc.) increase the operational cost, water usage, and post-treatment cost, and may still yield products with inconsistent charge density, fiber morphology, or dispersibility.

[0005] To produce lower cost carboxylated nanocellulose, it is imperative to expand the application of nitro-oxidation process to directly treat non-plant and mixed organic biomasses, such as animal waste food waste, where the process can (a) effectively produce carboxylate groups on the cellulose surface to facilitate the nanofibrillation process, (b) integrate quench, washing, and ion-exchange steps, and (c) produce carboxylated nanocellulose suitable for agriculture, biomedicine, construction materials, packaging and environmental remediation, while the NOP produced nutrient-rich effluents can be directly neutralized and conditioned into fertilizers for plant growth.SUMMARY OF THE INVENTION

[0006] To overcome the problems described above, example embodiments of the present invention provide nitro-oxidation processes that convert heterogeneous non-plant biomass—including animal manure, aquatic biomass, insect biomass, agricultural / food-processing residues (e.g., shells, bones, membranes), livestock waste, and consumer / residential / urban organics— into carboxylated nanocellulose and a nutrient-rich aqueous effluent. In certain example embodiments, pretreated biomass (moisture 0 wt%-80 wt%) is contacted with 25 wt%-70 wt% HNO3at 20°C-80°C for 0.5 h-12 h, optionally with a nitrite promoter, under atmospheric or sealed-reactor conditions with headspace control. The resulting co-product effluent can be used as a fertilizer and can contain a total nitrogen content in a range from 5 wt%-35 wt% (e.g., nitrate, nitrite and amino acid) with recoverable macro / micronutrients (e.g., K, P, Ca, Mg, S). The resulting carboxylated nanocellulose can be used to prepare suspensions, gels, films, powders, and aerogels for applications in agriculture, biomedicine, filtration, composites, packaging, and environmental remediation.

[0007] Example embodiments of the present invention address the above goals by providing modified nitric-acid based nitro-oxidation and carboxylation process tailored to nonplant biomass that both produces NOCNF and recovers soluble macro- and micronutrients in the effluent. Example embodiments of the present invention use NOP technology to enable the creation of carboxylated nanocelluloses with high degrees of oxidation, despite the presence of high contents of noncellulosic components (e.g., lignin, lipid, fat, protein, etc.).

[0008] Example embodiments of the present invention specifically address the challenges of using heterogeneous non-plant feedstocks in NOP operation, yielding carboxylated nanocellulose that can be used in multiple applications, including rheology modification, barrier films, composites, agricultural growing media, biomedicine, environmental remediation, and the like, while also producing a nutrient-enriched effluent containing carbons (e.g., degraded lignin, hemicellulose, lipids, fats, etc.), organic and inorganic nitrogen species (e.g., amino acids, nitrites, nitrates, etc.), that can be conditioned into effective slow-release fertilizers for plant growth.

[0009] Example embodiments of the present invention concern conversion of organic biomass into nanostructured, carboxylated cellulosic materials. In particular, example embodiments of the present invention relate to production of nitro-oxidized cellulosicnanofibers (NOCNF) via a nitro-oxidation process (NOP) applied to non-plant biomass and mixed organic waste feedstocks or streams.

[0010] Processes of example embodiments of the present application applie to diverse feedstocks, including, without limitation, animal manure, aquatic biomass, agricultural and food processing residues, insect biomass, livestock waste, and other organic materials, such as consumer, residential, and urban organic waste. The processes of the example embodiments of the present invention are designed to introduce carboxyl functional groups into at least a portion of the resultant materials, enhancing chemical and physical properties for use in agriculture (e.g., gels, films, soil amendments), biomedicine, cosmetic, construction materials, environmental remediation, packaging and related applications with the co-product effluents containing solubilized macronutrients and micronutrients recoverable for downstream agricultural use.

[0011] According to example embodiment of the present invention, carboxylated cellulosic nanofibers (CNFs) can have a degree of oxidation (DO) from about 0.5 mmol-g"1-about 2.5 mmol-g"1, wherein the CNFs are obtained by treating a non-plant biomass feedstock using a nitro-oxidation process (NOP), and wherein the DO is measured on washed oxidized cellulose obtained by the NOP at a pH greater than about 2.5.

[0012] The CNFs can include carboxylated lignin-containing cellulosic nanofibers (LCNF) having residual lignin from about 0.5 wt%-20 wt%. The CNFs can be included in an aqueous suspension, a hydrogel, a spray-dried powder, a film, an aerogel, or a foam. Carboxylation of the CNFs can occur predominantly at a C6 position of glucose units in cellulose. Attenuated total reflectance-infrared (ATR-IR) spectroscopy of the CNFs can show attenuation of ~1510- 1530 cm-1lignin bands. The D50 fibril width can be about 3 nm-about 50 nm, as determined by TEM.

[0013] The solids yield can be about 2 wt%-about 50 wt% relative to dry weight of the nonplant biomass feedstock.

[0014] The non-plant biomass feedstock can be selected from animal manure, cow manure, horse manure, poultry litter, aquatic biomass, shrimp shells, lobster shells, agricultural residues, food-processing waste, eggshells, egg membranes, livestock / animal-processing waste, bones,cartilage, insect biomass, algae, seaweed, mixed food waste, consumer / residential / urban / municipal organic waste, or a mixture thereof. The non-plant biomass feedstock can include a lignocellulosic component.

[0015] Animal-derived fractions can be included in the non-plant biomass feedstock, and attenuated total reflectance-infrared (ATR-IR) spectroscopy of the CNFs can show amide bands at ~1630 cm-1and ~1550 cm-1with the 1720 cm"1-l730 cm-1carboxyl band dominant.

[0016] According to example embodiments of the present invention, an aqueous effluent can co-produced with the carboxylated cellulosic nanofibers of one of other example embodiments. The aqueous effluent can include (a) carboxylated cellulosic nanofibers from about 0.01 wt%-about 0.1 wt%; (b) a total nitrogen content from about 5 wt%-35 wt%; (c) solubilized macro- / micronutrients selected from P, K, S, Ca, Mg, Na, Fe, Zn, Mn, Si, Cu, or a combination thereof; and (d) being substantially free of insoluble mineral grit removed during solid-liquid separation.

[0017] The total nitrogen content can include a nitrate, a nitrite, an amino acid, or a combination thereof. The aqueous effluent can further include phosphate at about 0.05 g-L"1- about 2 g-L"1and / or calcium at about 0.1 g-L"1-about 5 g-L"1.

[0018] According to an example embodiment of the present invention, a method for producing carboxylated nanocellulose from non-plant biomass feedstock includes (a) pretreating the non-plant biomass feedstock to adjust moisture to about 0 wt%-80 wt%; (b) contacting the non-plant biomass feedstock with about 25 wt%-about 70 wt% HNO3at about 20°C-about 80°C with a reaction time of about 0.5 h-about 12 h to form a mixture; (c) agitating the mixture at about 100 rpm-about 600 rpm, under (i) atmospheric conditions at about 15 psi or (ii) sealed-reactor conditions at a pressure from about 5 psi-about 160 psi above atmospheric pressure with a headspace maintained between about 50% and about 90%, to produce solids and effluent; (d) separating the solids from the effluent; and (e) washing the solids to a pH of greater than about 2.5. The method can be performed without TEMPO nitroxyl catalysts, sodium hypochlorite, sodium bromide, or concentrated sulfuric-acid hydrolysis.

[0019] The method can further include mechanically reducing a size of the non-plant biomass feedstock to yield a D50 feed diameter < about 2 mm. An atmospheric reactor candirect off-gas to an alkaline scrubber or an adsorption column for vapor capture / recycle. A sealed reactor can reach a maximum pressure of about 50 psi-about 160 psi above atmospheric pressure, and headspace is tuned to control peak pressure and DO. Step (b) can include using a nitrite promoter of about 1 mM-about 500 mM. Step (e) can include ionexchange and / or pH-swing neutralization to set carboxylate counter-ions to H+or Ca2+or NH4+. The method can further include low-energy blending and / or high-pressure homogenization to form a hydrogel network. The method can further include collecting the effluent, and neutralizing and / or concentrating the effluent to form a liquid fertilizer, wherein the liquid fertilizer can include nitrate and at least one of K, Ca, Mg, P, or S. The method can further include colorimetrically verifying presence of nitrate and / or nitrite, wherein a total nitrogen in the liquid fertilizer can be about 5 wt%-about 35 wt%.

[0020] The solids yield of the NOP can be about 2 wt%-about 50 wt% relative to dry weight of the non-plant biomass feedstock. The solids can include carboxylated cellulosic nanofibers (CNFs) with a degree of oxidation (DO) from about 0.5 mmol-g"1-about 2.5 mmol-g"1. Step (a) can include removing lipids and / or proteins.

[0021] The non-plant biomass feedstock can be selected from animal manure, cow manure, horse manure, poultry litter, aquatic biomass, shrimp shells, lobster shells, agricultural residues, food-processing waste, eggshells, egg membranes, livestock / animal-processing waste, bones, cartilage, insect biomass, algae, seaweed, mixed food waste, consumer / residential / urban / municipal organic waste, or a mixture thereof.

[0022] If the non-plant biomass feedstock includes lipids, then step (c) can includes initially oxidizing the non-plant biomass feedstock to mitigate lipid interference and to form an oxidized mixture, and then carboxylating the oxidized mixture to preserve cellulose backbones in the non-plant biomass feedstock.

[0023] If the non-plant biomass feedstock is nitrogen-rich having a total nitrogen content from about 5%-about 35%, the method can include using ammonia scavengers and / or nitrogen-byproduct controllers to limit side reactions.

[0024] The method can be performed for about 3 h-about 5 h with about 50 wt% HNO3at about 50°C to achieve a yield of at least about 30% and a degree of oxidation (DO) of the CNFs of at least about 1.0 mmol-g"1.

[0025] In an absence of nitrite, the reaction time can be at least about 7 h and an acid strength can be non-diluted HNO3to achieve a degree of oxidation (DO) of the CNFs of at least about 1.0 mmol-g"1.

[0026] According to an example embodiment of the present invention, a method of tuning a nitro-oxidation process to a selected feedstock class includes setting an acid concentration, a nitrite level, a time, a temperature, an agitation, and a moisture to produce carboxylated cellulosic nanofibers (CNFs) having a degree of oxidation (DO) of about 0.5 mmol-g"1-about 2.5 mmol-g"1and to produce effluent. The feedstock class is selected from animal manure, aquatic biomass, agricultural residues, food-processing waste, insect biomass, livestock / animal- processing waste, consumer / residential / urban organic waste, or a mixture thereof.

[0027] If the feedstock class includes animal manure, the acid concentration can be about 50 wt% HNO3, the reaction time can be about 3 h-about 9 h, and the temperature can be about 50°C; the DO can be at least 1.0 mmol-g"1; and nitrate can be at least about 8 M in the effluent.

[0028] If the feedstock class includes insect biomass, the method can include pre-treating the feedstock class to selectively preserves chitin and can include oxidizing the feedstock to preferentially carboxylate cellulosic fractions.

[0029] If the feedstock class includes aquatic biomass, the method can include a lipid- extraction and / or staged-oxidation prior to carboxylation.

[0030] According to an example embodiment of the present invention, a nitro-oxidation system includes (a) a reactor that is configured for atmospheric or sealed operation with headspace control and that is configured to receive a non-plant biomass feedstock; (b) an acidmetering unit that delivers about 25 wt%-about 70 wt% of HNO3to the reactor so that the HNO3comes into contact with the non-plant biomass feedstock so that a nitro-oxidation process is performed on the non-plant biomass feedstock; (c) an agitator providing about 100 rpm-about 600 rpm; (d) an off-gas train including an alkaline scrubber and / or an adsorptioncolumn; and (e) a solid-liquid separator. The system produces the carboxylated cellulosic nanofibers of one of the other example embodiments and an aqueous effluent.

[0031] 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

[0032] 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 application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0033] Fig. 1 shows attenuated total reflectance-infrared (ATR-IR) spectra comparing carboxylated cellulose microfibers (CMF) produced by NOP with KNO2(NOP) versus without KNO2(CTRL) after a 9-hour reaction.

[0034] Fig. 2 shows ATR-IR spectra comparing carboxylated CMF produced by NOP after a 3-hour reaction time. Parameters include the addition of KNO2(NOP) and without KNO2(CTRL), and varying HNO3concentration: 50% CTRL = 0.417 M, 50% NOP = 0.222 M, 75% CTRL = 0.500 M, 75% NOP = 0.417 M, non-diluted (non-D) CTRL = 0.794 M, and non-D NOP = 0.635 M.

[0035] Fig. 3 shows ATR-IR spectra comparing carboxylated CMF produced by NOP after a 5-hour reaction time. Parameters include the addition of KNO2(NOP) and without KNO2(CTRL), and varying HNO3concentration: 50% CTRL = 0.417 M, 50% NOP = 0.222 M, 75% CTRL = 0.500 M, 75% NOP = 0.417 M, non-D CTRL = 0.794 M, and non-D NOP = 0.635 M.

[0036] Fig. 4 shows ATR-IR spectra comparing carboxylated CMF produced by NOP after a 7-hour reaction time. Parameters include the addition of KNO2(NOP) and without KNO2(CTRL), and varying HNO3concentration: 50% CTRL = 0.417 M, 50% NOP = 0.222 M, 75% CTRL = 0.500 M, 75% NOP = 0.417 M, non-D CTRL = 0.794 M, and non-D NOP = 0.635 M.

[0037] Fig. 5 shows ATR-IR spectra comparing carboxylated CMF produced by NOP after a9-hour reaction time. Parameters include the addition of KNO2(NOP) and without KNO2(CTRL),and varying HNO3concentration: 50% CTRL = 0.417 M, 50% NOP = 0.222 M, 75% CTRL = 0.500 M, 75% NOP = 0.417 M, non-D CTRL = 0.794 M, and non-D NOP = 0.635 M.

[0038] Figs. 6A and 6B are pictures of VitaMix blended NOP produced CMF after (A) 5 minutes, (B) 15 minutes, and (C) 20 minutes. Fig. 6A is in black and white. Fig. 6B is in greyscale.

[0039] Figs. 7A and 7B are transmission electron microscopy (TEM) images of cow manure derived CNF morphology produced through (A) homogenization or (B-D) blending. (A) CNF produced after 2 passes at 200 bar-400 bar through a homogenizer. (B-D) CNF produced after allowed time at max speed on a VitaMix blender after (B) 5 minutes, (C) 15 minutes, and (D) 20 minutes. Fig. 7A is in black and white. Fig. 7B is in greyscale.

[0040] Figs. 8A and 8B are pictures of hydrogel formation using CNF produced via 20- minute VitaMix blending. CNF hydrogels were produced using solutions with concentrations of 200 mM Ca (left), 100 mM Ca (middle), and 50 mM Ca (right). Fig. 8A is in black and white. Fig. 8B is in greyscale.

[0041] Fig. 9 is a graph of the pressure and temperature over time plot for reaction batch R05CML24116.

[0042] Fig. 10 is a graph of the pressure and temperature over time plot for reaction batch R05CML250108.

[0043] Fig. 11 is a graph of the pressure and temperature over time plot for reaction batch R05CML250109.

[0044] Fig. 12 is a chart of NOP CMF yield results comparing different headspace parameters by increasing LELY cow manure mass from 200 g to 500 g in increments of 100 g.

[0045] Fig. 13 is a chart of NOP CMF yield results comparing different reaction times of LELY cow manure NOP.

[0046] Fig. 14 is a chart of NOP CMF yield results comparing different agitator rotation speeds for LELY cow manure.

[0047] Fig. 15 shows Fourier transform infrared (FTIR) spectra of raw yellow potato and sweet potato skins and resulting NOP produced CNFs.

[0048] Fig. 16 shows FTIR spectra for (a) raw materials and (b) NOP CNFs produced from the food mixture at varying days of incubation.

[0049] Figs. 17A and 17B shows photographs of (a) combined plant and non-plant food waste, (b) produced carboxylated CNFs from NOP treatment, and (c) calcium crosslinked CNF hydrogel. Fig. 17A is in black and white. Fig. 17B is in greyscale.

[0050] Fig. 18 show the ATR-IR spectrum of CMF produced from mixed food waste by the NOP treatment with 70% HNO3.

[0051] Figs. 19A and 19B show (a) Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analysis of the NOP effluent (using 30%-50% nitric acid) from chicken bones and (b) images of the extracted NOP effluents. Fig. 19A is in black and white. Fig. 19B is in greyscale.

[0052] Figs. 20A and 20B show (a) ICP-OES analysis of the NOP effluent (using 30%-50% nitric acid) from shrimp shells, and (b) images of the extracted NOP effluents. Fig. 20A is in black and white. Fig. 20B is in greyscale.

[0053] Figs. 21A and 21B show (a) ICP-OES analysis of the NOP effluent (using 30%-50% nitric acid) from lobster shells, and (b) images of the extracted NOP effluents. Fig. 21A is in black and white. Fig. 21B is in greyscale.

[0054] Fig. 22 shows the ATR-IR spectrum of NOP produced solid suspension (collagen containing material) from chicken bone treated with 70% HNO3.

[0055] Fig. 23 shows the ATR-IR spectrum of carboxylated CMF produced from ground coconut shell using 70% HNO3.DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0056] Example embodiments of the present invention provide nitro-oxidation processes to produce carboxylated nanocelluloses from diverse non-plant biomass sources. For example, example embodiments of the present invention can optimize the NOP treatments disclosed in U.S. Patent No. 10,894,838 or in PCT Application No. PCT / US2015 / 060261. The entire contents of U.S. Patent No. 10,894,838 and PCT Application No. PCT / US2015 / 060261 are hereby incorporated by reference. It is also possible to optimize other NOP treatments. Through tailored pre-treatment, oxidation conditions, moisture content adjustments, and purification steps, the processes of the example embodiments efficiently convert various non-plant biomass feedstocks into carboxylated nanocellulose and other cellulosic products. By incorporatingcarboxyl functional groups, the NOP treatments can enhance the reactivity, binding capacity, and compatibility of the resulting nanocellulose suitable for various end uses. The carboxylation feature on nanocellulose, combined with creation of high nitrogen, lipid, protein, and recoverable macro- and micronutrients (e.g., nitrate, phosphate, potassium, magnesium, calcium, etc.) content in the effluent, allows for the production of effective agricultural materials not achievable through the known plant-based oxidation processes. In certain example embodiments, the processes are implemented under atmospheric or sealed-reactor conditions with optional nitrite promoters, controlled headspace, and feedstock moisture management, enabling simultaneous formation of carboxylated nanocellulose and a nutrientrich effluent suitable for recovery, recycling, or direct use. These processes methods can be performed without TEMPO nitroxyl catalysts, sodium hypochlorite, sodium bromide, or concentrated sulfuric-acid hydrolysis.

[0057] Example embodiments of the present invention include methods that tune nitrooxidation processes (NOPs) for a selected feedstock class by tuning, for example, an acid concentration, a nitrite level, time, temperature, agitation amount, moisture level, or headspace in a sealed reactor. For example, the feedstock class can be selected from animal manure, aquatic biomass, agricultural residues, food-processing waste, insect biomass, livestock / animal-processing waste, consumer / residential / urban organic waste, or a mixture thereof. By tuning, the methods can simultaneously produce effluent and carboxylated cellulosic nanofibers (CNFs), and the non-plant biomass feedstock can be selected from animal manure, cow manure, horse manure, poultry litter, aquatic biomass, shrimp shells, lobster shells, agricultural residues, food-processing waste, eggshells, egg membranes, livestock / animal-processing waste, bones, cartilage, insect biomass, algae, seaweed, mixed food waste, consumer / residential / urban / municipal organic waste, or a mixture thereof. The non-plant biomass feedstock can include a lignocellulosic component and / or animal-derived fractions.

[0058] The CNFs can have a degree of oxidation (DO) from about 0.5 mmol-g"1-about 2.5 mmol-g"1, within manufacturing and / or measurement tolerances, and can be obtained by treating a non-plant biomass feedstock using a nitro-oxidation process (NOP). The DO can bemeasured on washed oxidized cellulose obtained by the NOP at a pH greater than about 2.5, within manufacturing and / or measurement tolerances. Carboxylation of the CNFs can occur predominantly at a C6 position of glucose units in cellulose.

[0059] The CNFs can include carboxylated lignin-containing cellulosic nanofibers (LCNF). The LCNG can have residual lignin from about 0.5 wt%-20 wt%, within manufacturing and / or measurement tolerances.

[0060] As shown by attenuated total reflectance-infrared (ATR-IR) spectroscopy, the CNFs can show attenuation of ~1510-1530 cm-1lignin bands, or can show amide bands at ~1630 cm-1and ~1550 cm-1with the 1720 cm"1-l730 cm-1carboxyl band dominant. The D50 fibril width can be about 3 nm-about 50 nm. The D50 fibril width can be determined by TEM.

[0061] The CNFs can be used as a non-TEMPO carboxylated nanocellulose. For example, the CNFs can be used in rheology modification, hydrogel formation via ionic crosslinking (e.g., Ca2+), barrier films / coatings, composite reinforcement, biomedical dressings or scaffolds, filtration / adsorbents, or soil conditioners. The CNF lack TEMPO-origin nitroxyl residues and has sulfate half-esters than about 0.10 wt% S, within manufacturing and / or measurement tolerances. The CNFs can be included in an aqueous suspension, a hydrogel, a spray-dried powder, a film, an aerogel, or a foam. The NOCNF can be blended with starches, chitin / chitosan, proteins, or biodegradable polymers to form biodegradable packaging or textile fibers.

[0062] Methods for producing carboxylated nanocellulose from non-plant biomass feedstock can pre-treat the non-plant biomass feedstock. For example, the moisture of the non-plant biomass feedstock can be adjusted. The moisture can be adjusted in a range from about 0 wt%-80 wt%, within manufacturing and / or measurement tolerances. In some example embodiments the pretreatment can be skipped. Alternatively or in addition to adjusting the moisture, the non-plant biomass feedstock can be mechanically reduced in size by any suitable method. The reduced feedstock can have a D50 feed diameter < about 2 mm. Pre-treatment can include removing lipids and / or proteins.

[0063] The methods can include contacting the non-plant biomass feedstock with an acid, such as HNO3in an NOP process, to form a mixture. The concentration of HNO3can be about 25wt%-about 70 wt%, within manufacturing and / or measurement tolerances, and the reaction can occur at a temperature from about 20°C-about 80°C, within manufacturing and / or measurement tolerances, with a reaction time of about 0.5 h-about 12 h, within manufacturing and / or measurement tolerances. In addition, a nitrite promoter can be used in an anmount of about 1 mM-about 500 mM, within manufacturing and / or measurement tolerances.

[0064] The mixture can be agitated using any suitable agitator to produce solids and aqueous effluent. For example, the mixture can be agitated about at about 100 rpm-about 600 rpm, within manufacturing and / or measurement tolerances.

[0065] The NOP reaction can be conducted at atmospheric conditions (e.g., about 15 psi), within manufacturing and / or measurement tolerances. Alternatively, the NOP reaction can be conducted in a sealed reactor. The pressure in the sealed reactor can be at a pressure from about 5 psi-about 160 psi above atmospheric pressure, within manufacturing and / or measurement tolerances. The sealed reactor can have free gas volume or headspace maintained between about 50% and about 90% of the reactor volume, within manufacturing and / or measurement tolerances, or maintained between about 10% and about 90% of the reactor volume, within manufacturing and / or measurement tolerances. As an example, a sealed reactor can reach a maximum pressure of about 50 psi-about 160 psi above atmospheric pressure, within manufacturing and / or measurement tolerances, and headspace can be tuned to control peak pressure and DO.

[0066] After agitating the mixture, the solids (including the CNFs) and the effluent can be separated. The solids yield can be about 2 wt%-about 50 wt% relative to dry weight of the nonplant biomass feedstock, within manufacturing and / or measurement tolerances. The solids can include carboxylated cellulosic nanofibers (CNFs) with a degree of oxidation (DO) from about 0.5 mmol-g"1-about 2.5 mmol-g"1, within manufacturing and / or measurement tolerances.

[0067] The separated solids can be washed to a pH of greater than about 2.5, within manufacturing and / or measurement tolerances. Washing can include ion-exchange and / or pH- swing neutralization to set carboxylate counter-ions to H+or Ca2+or NH4T After washing, low- energy blending and / or high-pressure homogenization can be used to form a hydrogel network.

[0068] The effluent can be collected. The effluent can include (a) carboxylated cellulosic nanofibers from about 0.01 wt%-about 0.1 wt%; (b) a total nitrogen content from about 5 wt%-35 wt%; (c) solubilized macro- / micronutrients selected from P, K, S, Ca, Mg, Na, Fe, Zn, Mn, Si, Cu, or a combination thereof; and (d) being substantially free of insoluble mineral grit removed during solid-liquid separation. After being collected, the effluent can be neutralized and / or concentrated, which can them be used to form a liquid fertilizer. Such a liquid fertilizer can include nitrate and at least one of K, Ca, Mg, P, or S. The presence of nitrate and / or nitrite can be colorimetrically verified. The total nitrogen content in the liquid fertilizer can be about 5 wt%-about 35 wt%, within manufacturing and / or measurement tolerances. The liquid fertilizer can be used in soil, fertigation, or hydroponic systems. The effluent can be co-applied with the CNFs to deliver soil conditioning plus nutrient supply.

[0069] The total nitrogen content of the effluent can include a nitrate, a nitrite, an amino acid, or a combination thereof. The effluent can include phosphate at about 0.05 g-L"1-about 2 g-L"1and / or calcium at about 0.1 g-L"1-about 5 g-L"1.

[0070] If the non-plant biomass feedstock includes lipids, then, when the mixture is being agitated, the non-plant biomass feedstock can be initially oxidized to mitigate lipid interference, and then the oxidized mixture can be carboxylated to preserve cellulose backbones in the nonplant biomass feedstock.

[0071] If the feedstock class includes aquatic biomass, the method can also include a lipid- extraction and / or staged-oxidation prior to carboxylation.

[0072] If the non-plant biomass feedstock is nitrogen-rich (e.g., having a total nitrogen content from about 5%-about 35%, within manufacturing and / or measurement tolerances), ammonia scavengers and / or nitrogen-byproduct controllers can be used to limit side reactions.

[0073] If the feedstock class includes animal manure, the acid concentration can be about 50 wt% HNO3, the reaction time can be about 3 h-about 9 h, and the temperature can be about 50°C; the DO can be at least about 1.0 mmol-g"1; and nitrate can be at least about 8 M in the effluent, within manufacturing and / or measurement tolerances.

[0074] If the feedstock class includes insect biomass, pre-treating can include selectively preserving chitin in the feed stock and can include oxidizing the feedstock to preferentially carboxylate cellulosic fractions.

[0075] In an absence of nitrite, the reaction time can be at least about 7 h and an acid strength can be non-diluted HNO3to achieve a degree of oxidation (DO) of the CNFs of at least about 1.0 mmol-g"1, within manufacturing and / or measurement tolerances.

[0076] As an example, the method can be performed for about 3 h-about 5 h with about 50 wt% HNO3at about 50°C to achieve a yield of at least about 30% and a degree of oxidation (DO) of the CNFs of at least about 1.0 mmol-g"1, within manufacturing and / or measurement tolerances.

[0077] Nitro-oxidation systems according to example embodiments of the present invention can be used to produce the CNFs and effluent. The nitro-oxidation systems can include a reactor that is configured to receive a non-plant biomass feedstock, an acid-metering unit, an agitator, an off-gas train, and a solid-liquid separator.

[0078] The reactor can be configured for atmospheric operation. Alternatively, the reactor can be configured for sealed operation with headspace control (i.e., the volume of free gas can be controlled). The headspace can be controlled by controlling the amount of non-plant biomass feedstock in the reactor. More non-plant biomass feedstock results in less headspace.

[0079] The acid-metering unit can deliver about 25 wt%-about 70 wt% of acid (e.g., HNO3) to the reactor so that the acid comes into contact with the non-plant biomass feedstock to undergo an NOP reaction.

[0080] The agitator can provide about 100 rpm-about 600 rpm, within manufacturing and / or measurement tolerances.

[0081] The off-gas train can include atmospheric reactor that can direct off-gas to an alkaline scrubber and / or an adsorption column for vapor capture / recycle.

[0082] The solid-liquid separator can be any suitable separator that can separate the solids and effluent.Example 1. NOP Treatment of Cow Manure to Produce Carboxylated Cellulose Microfibers (CMF)

[0083] In an example nitro-oxidation process (NOP), a feedstock is contacted with nitric acid (HNO3) of selected concentration and, optionally, potassium nitrite (KNO2) as an additional oxidization agent. In certain example embodiments, KNO2can be omitted, and an NOP can be performed using only HNO3under elevated pressure in a sealed reactor.

[0084] In one example embodiment (e.g., ambient-pressure NOP), cow manure (80% moisture) obtained from the Cornell Cooperative Extension of Suffolk was treated by combining untreated manure with varying volumes of HNO3(28%— 50%) at 50°C for 3 hours, 5 hours, 7 hours, or 9 hours, with or without 14 mmol of KNO2. Total solid yield and degree of oxidation (DO) (by potentiometric titration) were determined, and reaction time was used as the basis to compare carboxylated cellulose microfibers (CMFs) and effluent products across varying conditions (see Table 1 for reaction matrices; Tables 2-6 and Figures 1-5 for the resulting CMFs).Table 1: Various parameters for Suffolk cow manure NOP reactions.

[0085] In Fig. 1, attenuated total reflectance infrared (ATR-IR) spectra of all fiber products exhibited features consistent with carboxylated cellulose, including a broad -OH band at ~3330 cm-1and a carbonyl band at ~1709 cm-1(see Figs. 1-5). Solid yield generally increased as the reaction volume decreased, which is attributed to greater fiber-fiber friction during nitrooxidation, thereby promoting mechanical defibrillation. The highest yields were observed for 3 h / 50% NOP, 5 h / 50% NOP, and 3 h / 50% CTRL, at 34.76%, 33.16%, and 31.36%, respectively. The highest degrees of oxidation (DO) were measured for 5 h / 50% NOP (1.23 mmol g-1), 9 h non-diluted CTRL (1.21 mmol g-1), and 7 h / 50% CTRL (1.03 mmol g-1). The lowest DO valuesoccurred at 9 h / 50% NOP (0.68 mmol g’1), 7 h / 50% NOP (0.74 mmol g’1), and 9 h / 75% NOP (0.71 mmol g-1). Across the tested matrix, CTRL (HNO3-only) runs produced DO values that were generally comparable to, and in some cases slightly below, those obtained under NOP conditions (HNO3with optional KNO2), with specific outcomes depending on acid concentration and reaction time (see Tables 2-6 below)Table 2: Calculated yield and degree of oxidation (via potentiometric titration) of carboxylated CMF produced by NOP with (NOP) and without (CTRL) KNO2 after a 9-hour reaction time.Table 3: Calculated yield and degree of oxidation (via potentiometric titration) of carboxylated CMF produced by NOP with (NOP) and without (CTRL) KNO2 after a 3-hour reaction time. Parameters included the addition of KNO2 (NOP) and without KNO2 (CTRL), and concentration of HNO3 varied where 50% CTRL = 0.417 M, 50% NOP = 0.222 M, 75% CTRL = 0.500 M, 75% NOP = 0.417 M, non-D CTRL = 0.794 M, and non-D NOP = 0.635 M.Table 4: Calculated yield and degree of oxidation (via potentiometric titration) of carboxylated CMF produced by NOP with (NOP) and without (CTRL) KNO2 after a 5-hour reaction time. Parameters included the addition of KNO2 (NOP) and without KNO2 (CTRL), and concentration of HNO3 varied where 50% CTRL = 0.417 M, 50% NOP = 0.222 M, 75% CTRL = 0.500 M, 75% NOP = 0.417 M, non-D CTRL = 0.794 M, and non-D NOP = 0.635 M.Table 5: Calculated yield and degree of oxidation (via potentiometric titration) of carboxylated CMF produced by NOP with (NOP) and without (CTRL) KNO2 after a 7-hour reaction time. Parameters included the addition of KNO2 (NOP) and without KNO2 (CTRL), and concentration of HNO3 varied where 50% CTRL = 0.417 M, 50% NOP = 0.222 M, 75% CTRL = 0.500 M, 75% NOP = 0.417 M, non-D CTRL = 0.794 M, and non-D NOP = 0.635 M.Table 6: Calculated yield and degree of oxidation (via potentiometric titration) of carboxylated CMF produced by NOP with (NOP) and without (CTRL) KNO2 after a 9-hour reaction time. Parameters included the addition of KNO2 (NOP) and without KNO2 (CTRL), and concentration of HNO3 varied where 50% CTRL = 0.417 M, 50% NOP = 0.222 M, 75% CTRL = 0.500 M, 75% NOP = 0.417 M, non-D CTRL = 0.794 M, and non-D NOP = 0.635 M.

[0086] Overall, across 3h-9 h and various acid strengths (50%, 75%, non-diluted), the data show that moderate acid and shorter times maximize solids recovery, while oxidation peaks earlier under NOP samples and later under CTRL samples. At 50% HNO3, yields are highest at 3 h-5 h with KNO2(34.76% at 3 h; 33.16% at 5 h), exceeding the matched CTRL samples (31.36% at 3 h; 26.57% at 5 h) and declining at longer times; corresponding degrees of oxidation (DO) reach a maximum of ~1.25 mmol g-1at 5 h (NOP) and then drop by 7 h-9 h (0.74 mmol g-1- 0.68 mmol g-1). At higher acid concentrations (75%) and at non-diluted conditions, yields arelower overall, and NOP DO values remain < 0.97 mmol g-1at 7 h-9 h. In contrast, CTRL samples (i.e., HNO3-only) show a steadier rise in DO with time / strength, achieving ~1.03 mmol g-1at 7 h (50%) and an overall peak of ~1.21 mmol g-1at 9 h under non-diluted HNO3, albeit with lower yields (~25%). These results indicate a practical window at 50% HNO3for 3 h-5 h with KNO2to balance high solids yield (33%— 35%) with elevated oxidation, while extended, stronger-acid CTRL conditions favor maximum DO on the retained solids at the expense of recovery.Example 2: CNF and Hydrogel Preparation from NOP Treatment of Cow Manure using Low-Energy Blending and Metal Ion Gelation

[0087] To reduce the energy demand of conventional homogenization used to produce homogeneous cellulose nanofiber (CNF) suspensions, a substitute blending approach was evaluated on nitro-oxidized CMF derived from cow manure. The CMF sample was prepared at 50°C for 9 h using a manure solids-to-50 wt% HNO3mass ratio of 1:14, and was then subjected to high-speed blending (VitaMix) for 5 min, 15 min, or 20 min as shown in Figs. 6A and 6B. Fiber morphology from the blended suspensions (5 min-20 min) was compared with CNF made by pressure-based homogenization as shown in Figs. 7A and 7B. The homogenized CNF appeared slightly thicker than the blended CNF, consistent with differences in shear generationhomogenization producing shear via pressure drop, whereas blending increases shear exposure primarily through mixing time. The blending route was further used to form CNF gel networks by adding aqueous calcium nitrate (Ca(NO3)2) solutions at 200 mM, 100 mM, or 50 mM to the blended CNF; gels were prepared at a 0.5 mL salt solution : 5 mL CNF suspension ratio (see Figs. 8A and 8B). After overnight setting, bubbles remained dispersed within the gel networks. This example demonstrates that high-speed blending can produce CNF from NOP produced CMF, where the CNF dispersion can be subsequently crosslinked by metal ions and form a stable hydrogel. The use of highOspeed blending can reduce the energy consumption typically required for homogenization.Example 3: NOP Effluent Characterization to Quantify Nutrient Recovery from the Feedstock

[0088] The nutrient recovery in the NOP effluent was characterized as a function of time and acid-strength conditions. First, NOP effluents from varying reactions described above were collected and analyzed by ICP-OES (results are shown in Tables 7 and 8 below). Specifically, NOPeffluents from the use of 0.794 M HNO3runs at 3 h, 5 h, 7 h, and 9 h were characterized to quantify the Al, Ca, Cu, Fe, K, Mg, Na, P, S, Si, Zn, and Ni content (as shown in Table 7). The concentration study at a fixed 3 h reaction time to evaluate the effect of HNO3strengths (including 0.417 M and 0.5 M) on the macronutrient recovery efficiency was also carried out and the results are shown in Table 8.

[0089] The time effect at 0.794 M HNO3is shown in Table 7. The macronutrient (Ca, K, Mg, P, S) concentrations increased steadily until 3 h but did not increase further with additional reaction time (5 h-9 h). This indicates that at ~3 h, all macronutrients were recovered at this acid strength (0.794 M HNO3). The micronutrient levels (e.g., Fe, Zn, Cu) also did not show noticeable time-dependent gains above 3 h.

[0090] The concentration effect at 3 h is shown in Table 8. The results indicates that 0.417 M HNO3was sufficient to recover all macronutrients, where higher concentrations offering limited benefit for Ca / K / Mg / P / S recovery under these conditions. Micronutrient recoveries across concentrations at 3 h did not show a consistent trend. One 0.5 M HNO3sample exhibited anomalously high Fe and elevated levels of other metals; this invariability is attributed to exogenous mixed-metal debris (e.g., rock or ingested metallic particulates) present in the manure during NOP.Table 7: ICP-OES data on cow manure NOP treatment varying reaction time (3, 5, 7, and 9 hr). Values reported are in ppm.Table 8: ICP-OES data on cow manure NOP treatment varying concentration of nitric acid (0.794, 0.5, and 0.417 M). Values reported are in ppm.

[0091] As a whole, for the manure feedstock and the conditions tested, it appears that 3 h reaction time is adequate for recovery of macronutrients, and ~0.417 M HNO3at 3 h provides an efficient acid dose for recovery of Ca, K, Mg, P, and S. Extending time to 5 h-9 h at 0.794 M offers minimal additional nutrient recovery. In other words, micronutrient levels are largely time-insensitive over this window. These findings enable the selection of shorter, lower-acid NOP conditions to produce effluents enriched in plant-available nutrients while limiting the reagent use.

[0092] In another example embodiment, cow and horse manures (dried to <50% moisture) were treated by an NOP in a sealed reactor with 50% HNO3at 50°C for 9 h. The retained solids were predominantly carboxylated cellulose, while the acidic NOP effluent contained the solubilized carbon and nutrient fractions. ICP-OES (validated with NIST SRM 2706) showed that elemental compositions of NOP effluents closely matched the totals measured by acid digestion of the raw feedstocks, indicating that NOP solubilizes essentially all recoverable nutrients (P, K, S, Ca, Na, Fe, Mg, Mn, Zn, Si, and others). The overall difference before and after an NOP of cow and horse manure is illustrated in Tables 9, 10 and Tables 11, 12, respectively. The main systematic difference was higher K in effluents due to the use of KNO2during NOP. Sand / large mineral particulates remained insoluble and were removed with the carboxylated cellulose solids. Colorimetric assays confirmed that the effluents are nitrogen-rich, with nitrate the dominant species and total nitrogen on the order of 13%-14% N for cow and horse manure effluents as shown in Table 13.Table 9: Total P, K, S, Ca, and Na concentrations of raw biomass feedstock.Table 10: Total Fe, Mg, Mn, Zn, and Si concentrations of raw biomass feedstock.aValues indicated are averages of 3-5 replicates ± standard deviation or SD. Element concentrations were determined by ICP-OES analysis. M Total element concentrations in mg per g of biomass.Table 11: Total P, K, S, Ca, and Na concentrations recovered in the NOP effluent.Table 12: Total Fe, Mg, Mn, Zn, and Si concentrations recovered in the NOP effluent.aValues indicated are averages of 3-5 replicates ± standard deviation, SD. Element concentrations were determined by ICP-OES analysis. M Total element concentrations in mg per g of biomass.Table 13: Average nitrate and nitrite concentrations in the NOP effluent.concentration of nitrate was determined by subtracting the nitrite concentration from the concentration of total nitrite after the reduction of nitrate by VCh. lbl The concentration was determined by colorimetric detection by UV / Vis spectroscopy. M Total nitrogen values are representative of the sum of the mean concentrations of nitrate and nitrite, converted into stoichiometric elemental nitrogen.Example 4: NOP Treatment of Cow Manure Under Elevated Pressure

[0093] Cow-manure feedstock (as-received or dried to <5% moisture) was treated in a 5 L sealed autoclave equipped with agitation (~200 rpm) and a silicone heating jacket. Unless noted otherwise, runs used 50 % HNO3at a manure solid : acid ratio of 1:14, a setpoint of 50 °C, and a 9 h reaction time measured after completion of acid addition via peristaltic pump. Temperature and pressure were logged continuously for different reactions as shown in Figs. 9, 10, and 11.

[0094] Headspace study: Two sealed runs evaluated the effect of gas headspace for reactions R05CML24116 and R05CML250108 (Figs. 9 and 10). With increased headspace (reaction R05CML24116), the reaction proceeded to completion under seal; peak pressure reached ~141 psi and the recovered fiber exhibited a degree of oxidation (DO) of ~0.80 mmol-g"1as shown in Table 14 below. Reducing headspace (reaction R05CML250108) caused arapid temperature / pressure rise ~15 min after acid addition. For safety, the autoclave was vented and heating disabled; the reaction was then allowed to finish as an open system. The resulting material showed a lower DO (~0.441 mmol-g"1in Table 14) and a higher solid yield than reaction R05CML24116, consistent with premature pressure relief and reduced closed- system severity. A repeat sealed run (reaction R05CML250109) with controlled headspace reached a lower peak pressure (~111 psi) as shown in Fig. 11 and produced fiber with DO ~0.687 mmol-g"1in Table 14, further indicating that higher sealed-reactor pressure correlates with increased oxidation of the retained solids. Collectively, these results demonstrate that sealed-reactor NOP can be safely executed at 50°C, and that headspace management is a key lever for controlling maximum pressure and the resulting oxidation state of the product.Table 14: Parameters, % yield, and degree of oxidation of carboxylated CMF for various LELY cow manure NOP reactions.Example 5: Atmospheric-Pressure NOP to Treat Cow Manure at Varying Reactor Conditions (The Effects of Headspace, Agitation, and Reaction Time)

[0095] A 5-L stainless-steel reactor operated at atmospheric pressure was fitted with a condenser and two interchangeable off-gas pathways: (i) to an alkaline scrubber and (ii) to an adsorption column for capture / recycle of acidic vapors. Cow manure (moisture 60.96%) samples were provided by LELY and were used as received. Headspace was modulated by changing the mass of manure charged to the reactor (e.g., 300 g, 400 g, 500 g), thereby decreasing free gas volume (i.e., headspace) as mass increased. For example, if 500 g of biomass is used, then a headspace of about 75% of the reactor can be created; if 400 g of biomass is used, then a headspace of about 80% of the reactor can be created; if 300 g of biomass is used, then a headspace of about 85% of the reactor can be created; and if 200 g of biomass is used, then a headspace of about 90% of the reactor can be created. Nitric acid(process-grade) was charged to give the target solid : acid ratio as shown in Table 15 below.Agitation speed (rpm) and reaction time were varied per Table 15, and solids were recovered by filtration, washed, and dried for yield determination, as shown in Figs. 12-14.Table 15: Atmospheric pressure NOP reaction parameters for LELY cow manure treatment.

[0096] Headspace (manure mass): While decreasing headspace did not yield a strict monotonic trend, a general decline in solids yield was observed as mass increased from 300 g -> 400 g -> 500 g (as shown in Fig. 12), consistent with higher effective severity and enhanced solubilization at reduced gas volume.

[0097] Time: Shorter reaction times produced higher yields (as shown in Fig. 13), attributable to reduced defib ri I lation / delign if ication and less conversion of particulates to soluble species.

[0098] Agitation: Higher agitator rpm led to lower solids yields (as shown in Fig. 14), consistent with increased fiber-fiber friction that promotes mechanical defibrillation and delignification under an NOP.

[0099] Overall, for atmospheric NOP operation using this reactor, lower manure mass (i.e., greater headspace), moderate agitation, and shorter residence times favor higher solids recovery, while higher rpm and longer times drive deeper fiber conversion at the expense of yield.Example 6: NOP Treatment of Yellow and Sweet Potato Peels to Produce C arb oxy late d CNF

[0100] Mixed yellow-potato and sweet-potato peels were collected. Peels were oven-dried at 60°C for 24 h which is then treated with the 50% HNO3and 417 mM NaNO2(NOP), 50°C, constant stirring; reaction time was 6 h-9 h.

[0101] Dried peels were charged to the reactor and contacted with 50% HNO3containing 417 mM NaNO2at 50°C under continuous agitation for the indicated time (6 h, 7.5, or 9 h) in Fig. 15. After completion, the reaction slurry was diluted with deionized water, and the solids were recovered by filtration. The solids were washed with DI water until the filtrate pH ~ 2.5, yielding carboxylated CMF suspensions that were reserved for homogenization to produce CNFs.

[0102] ATR-IR spectra of all prepared CNFs from raw yellow potato (Po) and sweet potato (SP) indicated in Figure 15 (i) loss of lignin-associated features, evidenced by the disappearance of the ~1520 cm-1band (aromatic skeletal vibration), and (ii) oxidation of cellulosic components, evidenced by the appearance / intensification of a ~1730 cm-1band attributable to carboxyl (C=O) groups formed predominantly at the C6 position of glucose units. These spectral changes are consistent with successful nitro-oxidation and partial delignification / hemicellulose removal, producing oxidized CNFs suitable for downstream gelation or film formation.Example 7: NOP Treatment of Food Waste (Type 1) to Produce CNF and Hydrogel

[0103] Food waste mixture made up of chicken bones, eggshells, rice, potato skins, and corn husk was prepared and stored in an incubator at 35°C for 1 day, 7 days, 14 days, or 21 days. Following the incubation, the combined food waste was mixed with 40% nitric acid under constant stirring for 6 hours at 50°C. Once the reaction was complete, the produced CMFs were washed with DI water until reaching a pH of 2.5 and saved for homogenization to produce CNFs. ATR-IR spectra were collected on both the raw individual food and the resulting CNFs from the food mixture at varying days of incubation as shown in Fig. 16. As a baseline, characteristic cellulose features were observed near 3350 cm-1(-OH), 2930 / 2860 cm-1(-CH), 1710 cm-1(-COO"), 1150 cm-1(-CO-C), and 1080 cm-1(-CO). In the CNFs derived from the mixed food waste, additional amide bands appeared at ~1630 cm-1(Amide I) and ~1550 cm-1(Amide II), and a doublet near 1710 / 1730 cm-1was observed and assigned to carboxylic groups formed during oxidation and N-H stretching of collagen contributed by the chicken-bone fraction. These spectral changes indicate successful nitro-oxidation of starchy / plant components with superimposed protein signatures from the non-plant fraction, yielding oxidized CNFs suitable for gel formation. To demonstrate functionality, a hydrogel was prepared by ionic crosslinking the CNF suspension with 150 mM Ca(NO3)2; the resulting gel exhibited structural integrity comparable to hydrogels formed from CNF alone (see Figs. 17A and 17B), confirming that CNFs produced from heterogeneous food waste via NOP can be directly crosslinked without loss of network performance.Example 8: NOP Treatment of Mixed Food Waste (Type 2) to Produce C arb oxy late d CMF

[0104] Dried mixed food waste (potato, strawberry, carrot, lettuce) of 7.464 g total was placed into a 1,000-mL three-neck round-bottom flask fitted with overhead stirring (400 rpm), condenser, and thermometer; oil bath set to 50°C. About 44.784 mL of 70% HNO3was charged to the flask with the feedstock. The mixture was stirred at 400 rpm at 50 °C for 4 h under ambient pressure. To quench & work-up, the reaction was quenched by addition of 800 mL DI water. Solids were captured by filtration and washed with ~3 L DI water until the fiber pH > 3, then dried to constant mass. Dried solids (including CMF) were recovered in 8.51% yield (w / w). The ATR-IR analysis of the NOP produced CMF (as shown in Fig. 18) from this food waste mixture showed a band at ~1727 cm-1, consistent with carboxyl (C=O) stretching from oxidized cellulose, confirming successful nitro-oxidation and carboxylation of the fiber product.Example 9: NOP Treatment of Shrimp, Lobster, and Chicken Bones to Recover Nutrients

[0105] Post-consumer shrimp shells, lobster shells, and chicken bones were obtained from a Long Island composting group. Materials were oven-dried at 60°C for 24 h. NOP treatments of these materials were carried out to recover nutrients. No cellulose products can be obtained as the feedstock contained no lignocellulosic components. The NOP reaction conditions include nitric acid at 30%-50%, 50°C, 4-h reaction under constant stirring and atmospheric pressure. Each dried material (shrimp, lobster, chicken bones) was separately charged to the reactor and contacted with HNO3at the indicated concentration for 4 h. Upon completion, solids andliquors were separated by filtration. Filtrates ("effluents") were retained for elemental analysis by ICP-OES; recovered solids were washed with deionized water and saved for further characterization.

[0106] It was observed that decreasing the acid concentration from 50% to 30% reduced the solubilization of proteins and lipids present in the starting materials, yielding visibly richer organic content in the post-reaction solids and correspondingly lower clarity of the liquors (see (b) in Figs. 19A-21B). At higher acid strengths (> 40%-50 %), liquors became clearer and more colored, consistent with greater extraction / oxidation of organics and dissolution of mineral components.

[0107] Effluent analysis was carried out by ICP-OES analysis on each effluent to quantify the recovered nutrients (e.g., Ca, P, Na, Mg, Fe, Zn, etc.), as shown in (a) in Figs. 19A-21B. The dataset enables comparison of extraction efficiency vs. acid strength across the three animal- derived feedstocks.

[0108] In another example embodiment, a 1000-mL tri-neck round-bottom flask, approximately 7.417 grams of whole chicken bone and 44.5 mL of 70% nitric acid were added. The flask was then placed onto an oil bath, where the temperature was raised to 50°C and stirred at 300 RPM. After two hours, the reaction was quenched by adding 800 mL of water. During the reaction, the majority of the bone dissolved in the nitric acid. The fibrous portions were washed with approximately 1 L of water. The filtered materials were dried, and the percent recovery was 1.32%. The obtained material was characterized using FT-IR spectroscopy. The ATR-IR spectrum, as shown in Fig. 22, showed a sharp peak around 1738 cm-1 and a broad peak around 3000-3500 cm-1, which corresponded to the carboxyl and hydroxyl groups of the organic collagen present within the chicken bone.

[0109] In general, under otherwise identical conditions (50°C, 4 h), higher HNO3concentrations promote greater removal / oxidation of protein and fat fractions from shrimp / lobster shells and chicken bones, while lower concentrations (30%) produce reduced solubilization of these components. ICP-OES analysis of the effluents provides a quantitative basis for selecting acid strength to target either mineral / organic removal or retention in the solid fraction.T1Example 10: NOP Treatment of Ground Coconut Shell to Produce Carboxylated CMF

[0110] A 1,000-mL three-neck round-bottom flask with overhead stirring (400 rpm), condenser, thermometer; oil bath at 50°C was used to treat ground coconut shell, ~7.0 g (ovendry basis). About 42 mL of 70 % HNO3was added to the flask containing the feedstock. The slurry was stirred at 400 rpm at 50°C for 4 h under ambient pressure. To stop the NOP, the reaction was quenched with 800 mL distilled water. Solids were collected by filtration and washed with ~3 L water until the filtrate pH > 3, then dried to constant mass. Dried oxidized CMFs were obtained in 24.56% yield (w / w). The ATR-IR of the NOP produced CMF is shown in Fig. 23 and shows a band at ~1720 cm-1, consistent with carboxyl (C=O) stretching from nitrooxidation of cellulose, confirming successful introduction of carboxylate functionality.

[0111] 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

WHAT IS CLAIMED IS:

1. Carboxylated cellulosic nanofibers (CNFs) comprising a degree of oxidation (DO) from about 0.5 mmol-g"1-about 2.5 mmol-g"1, wherein the CNFs are obtained by treating a non-plant biomass feedstock using a nitro-oxidation process (NOP), and wherein the DO is measured on washed oxidized cellulose obtained by the NOP at a pH greater than about 2.5.

2. The carboxylated cellulosic nanofibers of claim 1, wherein the non-plant biomass feedstock is selected from animal manure, cow manure, horse manure, poultry litter, aquatic biomass, shrimp shells, lobster shells, agricultural residues, food-processing waste, eggshells, egg membranes, livestock / animal-processing waste, bones, cartilage, insect biomass, algae, seaweed, mixed food waste, consumer / residential / urban / municipal organic waste, or a mixture thereof.

3. The carboxylated cellulosic nanofibers of claim 1 or 2, wherein the non-plant biomass feedstock includes a lignocellulosic component.

4. The carboxylated cellulosic nanofibers of one of claims 1-3, wherein the CNFs includes carboxylated lignin-containing cellulosic nanofibers (LCNF) having residual lignin from about 0.5 wt%-20 wt%.

5. The carboxylated cellulosic nanofibers of one of claims 1-4, wherein the CNFs are included in an aqueous suspension, a hydrogel, a spray-dried powder, a film, an aerogel, or a foam.

6. The carboxylated cellulosic nanofibers of one of claims 1-5, wherein carboxylation of the CNFs occurs predominantly at a C6 position of glucose units in cellulose.

7. The carboxylated cellulosic nanofibers of one of claims 1-6, wherein attenuated total reflectance-infrared (ATR-IR) spectroscopy of the CNFs shows attenuation of ~1510-1530 cm-1lignin bands.

8. The carboxylated cellulosic nanofibers of one of claims 1-6, wherein animal-derived fractions are included in the non-plant biomass feedstock, and attenuated total reflectanceinfrared (ATR-IR) spectroscopy of the CNFs shows amide bands at ~1630 cm-1and ~1550 cm-1with the 1720 cm"1-l730 cm-1carboxyl band dominant.

9. The carboxylated cellulosic nanofibers of one of claims 1-8, wherein D50 fibril width is about 3 nm-about 50 nm, as determined by TEM.

10. The carboxylated cellulosic nanofibers of one of claims 1-9, wherein a solids yield is about 2 wt%-about 50 wt% relative to dry weight of the non-plant biomass feedstock.

11. An aqueous effluent co-produced with the carboxylated cellulosic nanofibers of one of claims 1-10, the aqueous effluent comprising:(a) carboxylated cellulosic nanofibers from about 0.01 wt%-about 0.1 wt%;(b) a total nitrogen content from about 5 wt%-35 wt%;(c) solubilized macro- / micronutrients selected from P, K, S, Ca, Mg, Na, Fe, Zn, Mn, Si, Cu, or a combination thereof; and(d) being substantially free of insoluble mineral grit removed during solid-liquid separation.

12. The aqueous effluent of claim 11, wherein the total nitrogen content includes a nitrate, a nitrite, an amino acid, or a combination thereof.

13. The aqueous effluent of claim 11 or 12, further comprising phosphate at about 0.05 g-L"1-about 2 g-L"1and / or calcium at about 0.1 g-L"1-about 5 g-L"1.

14. A method for producing carboxylated nanocellulose from non-plant biomass feedstock, the method comprising:(a) pre-treating the non-plant biomass feedstock to adjust moisture to about 0 wt%-80 wt%;(b) contacting the non-plant biomass feedstock with about 25 wt%-about 70 wt% HNO3at about 20°C-about 80°C with a reaction time of about 0.5 h-about 12 h to form a mixture;(c) agitating the mixture at about 100 rpm-about 600 rpm under (i) atmospheric conditions or (ii) sealed-reactor conditions at a pressure from about 5 psi-about 160 psi above atmospheric pressure with a headspace maintained between about 50% and about 90% to produce solids and effluent;(d) separating the solids from the effluent; and(e) washing the solids to a pH of greater than about 2.5, wherein the method is performed without TEMPO nitroxyl catalysts, sodium hypochlorite, sodium bromide, or concentrated sulfuric-acid hydrolysis.

15. The method of claim 14, wherein the solids include carboxylated cellulosic nanofibers (CNFs) with a degree of oxidation (DO) from about 0.5 mmol-g"1-about 2.5 mmol-g"1.

16. The method of claim 14 or 15, wherein step (a) includes removing lipids and / or proteins.

17. The method of one of claims 14-16, wherein step (b) includes using a nitrite promoter of about 1 mM-about 500 mM.

18. The method of one of claims 14-17, wherein the non-plant biomass feedstock is selected from animal manure, cow manure, horse manure, poultry litter, aquatic biomass, shrimp shells, lobster shells, agricultural residues, food-processing waste, eggshells, egg membranes, livestock / animal-processing waste, bones, cartilage, insect biomass, algae,seaweed, mixed food waste, consumer / residential / urban / municipal organic waste, or a mixture thereof.

19. The method of one of claims 14-18, further comprising mechanically reducing a size of the non-plant biomass feedstock to yield a D50 feed diameter < about 2 mm.

20. The method of one of claims 14-19, wherein an atmospheric reactor directs off-gas to an alkaline scrubber or an adsorption column for vapor capture / recycle.

21. The method of one of claims 14-20, wherein a sealed reactor reaches a maximum pressure of about 50 psi-about 160 psi above atmospheric pressure, and the headspace is tuned to control peak pressure and DO.

22. The method of one of claims 14-21, wherein, if the non-plant biomass feedstock includes lipids, then step (c) includes: initially oxidizing the non-plant biomass feedstock to mitigate lipid interference and to form an oxidized mixture, and then carboxylating the oxidized mixture to preserve cellulose backbones in the nonplant biomass feedstock.

23. The method of one of claims 14-22, wherein, if the non-plant biomass feedstock is nitrogen-rich having a total nitrogen content from about 5%-about 35%, the method includes using ammonia scavengers and / or nitrogen -byproduct controllers to limit side reactions.

24. The method of one of claims 14-23, wherein step (e) includes ion-exchange and / or pH-swing neutralization to set carboxylate counter-ions to H+or Ca2+or NH4T25. The method of one of claims 14-24, further comprising low-energy blending and / or high-pressure homogenization to form a hydrogel network.

26. The method of one of claims 14-25, wherein the method is performed for about 3 h-about 5 h with about 50 wt% HNO3at about 50°C to achieve a yield of at least about 30% and a degree of oxidation (DO) of the CNFs of at least about 1.0 mmol-g"1.

27. The method of one of claims 14-25, wherein in an absence of nitrite, the reaction time is at least about 7 h and an acid strength is non-diluted HNO3to achieve a degree of oxidation (DO) of the CNFs of at least about 1.0 mmol-g"1.

28. The method of one of claims 14-27, further comprising collecting the effluent, and neutralizing and / or concentrating the effluent to form a liquid fertilizer, wherein the liquid fertilizer includes nitrate and at least one of K, Ca, Mg, P, or S.

29. The method of claim 28, further comprising colorimetrically verifying presence of nitrate and / or nitrite, wherein a total nitrogen in the liquid fertilizer is about 5 wt%-about 35 wt%.

30. A method of tuning a nitro-oxidation process to a selected feedstock class, the method comprising setting an acid concentration, a nitrite level, a time, a temperature, an agitation, and a moisture to produce carboxylated cellulosic nanofibers (CNFs) having a degree of oxidation (DO) of about 0.5 mmol-g"1-about 2.5 mmol-g"1and to produce effluent; wherein the feedstock class is selected from animal manure, aquatic biomass, agricultural residues, food-processing waste, insect biomass, livestock / animal-processing waste, consumer / residential / urban organic waste, or a mixture thereof.

31. The method of claim 30, wherein, if the feedstock class includes animal manure: the acid concentration is about 50 wt% HNO3, the time is about 3 h-about 9 h, and the temperature is about 50°C, the DO is at least 1.0 mmol-g"1, andnitrate is at least about 8 M in the effluent.

32. The method of claim 30, wherein, if the feedstock class includes the insect biomass, the method includes pre-treating the feedstock class to selectively preserves chitin and includes oxidizing the feedstock to preferentially carboxylate cellulosic fractions.

33. The method of claim 30, wherein, if the feedstock class includes the aquatic biomass, the method includes a lipid-extraction and / or staged-oxidation prior to carboxylation.

34. A nitro-oxidation system comprising:(a) a reactor that is configured for atmospheric or sealed operation with headspace control and that is configured to receive a non-plant biomass feedstock;(b) an acid-metering unit that delivers about 25 wt%-about 70 wt% of HNO3to the reactor so that the HNO3comes into contact with the non-plant biomass feedstock so that a nitro-oxidation process is performed on the non-plant biomass feedstock;(c) an agitator providing about 100 rpm-about 600 rpm;(d) an off-gas train including an alkaline scrubber and / or an adsorption column; and(e) a solid-liquid separator, wherein the system produces the carboxylated cellulosic nanofibers of one of claims 1-10 and an aqueous effluent.

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