An Eco‐Efficient and Sustainable Strategy for Fabricating High‐Strength Agricultural Fibers

ABSTRACT

High‐value utilization of renewable biomass resources is of great significance for achieving ecological and societal sustainability. It remains highly desirable to convert agricultural residues into high‐performance regenerated cellulose fibers in a green and scalable manner. However, the fabrication of superior agricultural regenerated fibers is demanding due to the inherent anti‐depolymerization structure and low degree of polymerization of agricultural cellulose. Here, we demonstrated a recyclable and eco‐efficient process enabling the selective extraction of cellulose from agricultural residues using a novel acid deep eutectic solvent system, and proposed a stretch‐induced alignment and spatial confinement strategy to realize scalable fabrication of high‐strength and high‐toughness regenerated fibers. The deep eutectic solvent presented efficient delignification and tailoring capacity for agricultural residue, yielding cellulose with a high purity of 91.2% and a crystallinity of 72.6%. The resultant fibers addressed the intrinsic limitations of agricultural cellulose through the formation of aligned nanofibril structures and densified hydrogen‐bonding networks, exhibiting a tensile strength of 852 MPa and a toughness of 110 MJ m⁻³. This work establishes a foundational pathway for producing high‐performance bio‐based fibers derived from agricultural residues, advancing sustainable materials innovation and circular bioeconomy development.

A recyclable and eco‐efficient process enabling the selective extraction of cellulose from agricultural residues using a deep eutectic solvent system, and a generalizable structure‐programming strategy through the formation of aligned nanofibril structures and densified hydrogen‐bonding networks for fabricating regenerated cellulose fibers is developed, exhibiting an excellent tensile strength of 852 MPa and a prominent toughness of 110 MJ m⁻³.

1. Introduction

Regenerated cellulose fibers, as bio‐based alternatives to conventional fossil‐fuel‐derived synthetic fibers, have undergone unprecedented progress over the past decade, propelled by the sustainable development strategies and initiatives [1, 2]. As a type of artificial fiber, regenerated cellulose fibers, produced from natural cellulose through dissolution‐regeneration processes, present unparalleled advantages over synthetic fibers, including renewable feedstocks, biodegradability, excellent moisture absorption and breathability, softness and skin‐friendliness, and so on, enabling them to occupy a substantial and growing share of the global fiber market [3, 4]. However, the conventional viscose process has been questioned due to the extensive reliance on hazardous chemicals such as carbon disulfide, which poses serious environmental and occupational health risks, leading to restrictions in several developed countries [5, 6, 7]. As an ideal alternative, the Lyocell process employs an eco‐friendly N‐methylmorpholine‐N‐oxide (NMMO) aqueous solution with a closed‐loop solvent recovery rate exceeding 99%. Moreover, Lyocell fibers possess superior properties like high strength and high wet modulus, positioning them as a preferred material for sustainable textile innovation [8].

The production of Lyocell fibers faces two major challenges including the optimization of cellulose pulp preparation process and the modulation of fiber performance during formation [9]. The current pulp predominantly relies on imported wood pulp and cotton linters pulp, which are constrained by long growth cycles and limited land resources. Consequently, agricultural residues characterized by high yield, low cost, and abundant cellulose content have emerged as promising alternative feedstocks to overcome the raw material bottleneck. However, efficient cellulose separation from agricultural residues remains a challenge due to their intrinsic natural anti‐depolymerization barriers and highly heterogeneous composition [10]. Mainstream pulping technologies, such as the kraft process [11], alkali‐oxygen method [12], and mechanical grinding treatment [13], are confronted with the dual technical dilemmas of heavy contamination, high processing costs, and compromised cellulose quality. Therefore, exploring cellulose separation routes that simultaneously achieve environmental friendliness, economic feasibility, and process efficiency to realize clean and mild fractionation of agricultural residues has risen as a research frontier and critical technological breakthrough pathway for the field of biomass refining [14]. Due to strong hydrogen‐bonding interactions, deep eutectic solvent (DES) enables gentle and efficient extraction of cellulose without structural damage by selectively decomposing lignin and hemicellulose [15]. Furthermore, the separation ability of DES can be more easily regulated owing to the tailoring capability based on the solvent components and molar ratio [16], further enhancing adaptability across diverse biomass feedstocks. Nevertheless, cellulose extracted from agricultural residues (Agro‐cellulose) generally exhibits a relatively low degree of polymerization, which is unfavorable for the mechanical properties of regenerated fibers. The improvement of orientation can boost tensile strength and modulus of prepared fibers by facilitating stress transfer along aligned cellulose chains [17]. To this end, a stretch‐induced alignment strategy with green process and low‐energy consumption was employed to maintain a highly oriented molecular structure during fiber formation [18, 19]. Meanwhile, the formation of nanoscale crystallites of the obtained regenerated fibers was introduced, governed by constrained crystallization kinetics during the coagulation process [20, 21]. Then, the nanofibril structure was achieved by minimizing the distance between cellulose chains through spatial confinement treatment, leading to an enhancement of mechanical properties via densified hydrogen bonding networks [22, 23]. By synergistically optimizing orientation and interior nanostructure, regenerated cellulose fibers derived from agricultural residues (Agro‐RCFs) can accomplish advanced mechanical performance while retaining biodegradability and renewability, thereby bridging the performance gap of biomass fibers for high‐value applications.

In this work, we develop a recyclable and high‐yield approach for the selective separation of Agro‐cellulose and present a scalable and whole‐green strategy for fabricating Agro‐RCFs with superior strength and toughness (Figure 1). Specifically, a carboxylic acid‐based DES was employed to extract cellulose from agricultural residues by disrupting the ester bonds within lignin and the glycosidic bonds in lignin‐carbohydrate complexes (LCCs) through competitive hydrogen bonding. The resultant Agro‐cellulose exhibited an elevated crystallinity of 72.6% and optimal α‐cellulose content of 91.2%. Agro‐RCFs were fabricated through a dry‐jet wet spinning process with the dissolution of an eco‐friendly NMMO aqueous solution, which demonstrated a highly ordered hierarchical orientation and nanofibril crystalline structure via stretch‐induced alignment, controlled crystallization, and spatial confinement, achieving a tensile strength of 852 MPa, toughness of 110 MJ m⁻³, and specific work of rupture of 109 KJ m⁻². This study proposes a simple, sustainable, and scalable pathway for producing high‐performance regenerated cellulose fibers from agricultural residues, offering a considerable promise route for the valorization of low‐value biomass and the advancement of sustainable materials manufacturing.

FIGURE 1.

Fabrication mechanism of Agro‐RCFs. Schematic illustration of the separation of Agro‐cellulose using an acid DES and the spinning processes of Agro‐RCFs with nanofibril structure.

2. Results and Discussion

2.1. Separation Mechanism and Properties Analysis of Agro‐Cellulose

The available separation of biomass components constitutes a primary constraint in biomass valorization. Here, we demonstrate an efficient method for the extraction of Agro‐cellulose, enabling the selective cleavage of intercomponent linkages while preserving the native cellulose structure, where a carboxylic acid‐based DES was synthesized, comprising choline chloride (ChCl) as the hydrogen bond acceptor (HBA) and acetic acid (AA) as the hydrogen bond donor (HBD), as shown in Figure S1. To elucidate the delignification mechanism of this DES system, a β–O–4 linked lignin dimer, 2‐(2‐methoxyphenoxy)‐1‐(3,4‐dimethoxyphenyl) propane‐1,3‐diol (PG), was employed as a model compound [24], and the cleavage pathway of PG‐LCC was roughly described in Figure 2a. Chloride ions facilitated the scission of β–O–4 ether bonds within PG‐LCC, obtaining phenolic compounds and glycosidic intermediates, which dominated the ChCl‐based DES treatment process [25]. The glycosidic bonds of these intermediates were subsequently cleaved, generating carbohydrates and guaiacyl units of lignin, mainly attributed to the proton‐induced activation of acidic sites. Additionally, the introduction of protons promoted the formation of new π–π stacking interactions between protonated DES and the aromatic rings of lignin, thus weakening the intrinsic π–π interactions within lignin [26] (Figure S2). The characteristic structural motifs of herbaceous lignin and its structural units are illustrated in Figure S3. Concurrently, molecular dynamics (MD) simulations were conducted to further validate the chemical reactions involved in the DES delignification process (preliminary model and dynamic evolution process were shown in Figures S4 and S5, respectively). The results demonstrated that lignin underwent internal cleavage, and the linkages between lignin and carbohydrates were disrupted, thereby establishing a foundation for cellulose extraction (Figure S6). The quantitative changes in the initial PG‐LCC and the end products of carbohydrates and guaiacyl observed during the MD simulation served as direct indicators for the delignification process (Figure 2b). Meanwhile, the number of β–O–4 ether and glycosidic bonds were quantitatively determined (Figure 2c), and the number values of other typical bonds were also calculated in Figures S7 and S8. This cracking method had already occurred at the initial stage and directly facilitated the prompt generation of phenolic compounds. In the middle and late stages of this DES system, sufficient free protons could significantly enhance the fragmentation efficiency of lignin via forming hydrogen bonds with α–OH in lignin, resulting in a growth in the quantity of guaiacyl (Figures S9 and S10). These results collectively demonstrate that acidic HBDs could promote the disruption efficiency of PG‐LCC and enhance the cleavage of lignin‐carbohydrate bonds [27]. The simulation findings aligned well with the observed biomass separation phenomenon. 2D‐HSQC NMR spectra of DES‐derived lignin fractions presented two distinct regions, the side‐chain (Figure 2d) and aromatic signals (Figure 2e), and the corresponding lignin substructures were shown in Figure S11. The lower number of β–O–4 linkages supported the hypothesis of their cleavage during DES treatment [28, 29]. Furthermore, the degradation of carbon‐carbon linkages (such as β–β and β–5) and the recondensation phenomenon of syringyl (S) and guaiacyl (G) units also contributed to the high delignification efficiency.

FIGURE 2.

Reaction mechanism of the DES system and chemical structures of Agro‐cellulose. (a) Schematic illustration of the cleavage process of PG‐LCC. (b) The number of PG‐LCC, glucose, guaiacyl, and HBA/HBD molecules varies with the time step. (c) Number of β─O─4 bonds and glycosidic bonds vary with the time step. (d), (e) 2D HSQC‐NMR spectra of DES lignin fractions, showing aromatic and side‐chain regions. (f) Chemical component content. (g) The component content of cellulose, hemicellulose, and lignin in the C‐2 sample with different reaction times. (h) XRD spectra. (i, j) XRD curve fitting of raw and DES‐treated corncob (C‐2 sample). (k) FT‐IR analysis. (l) DP value. (m) Weight loss ratio and α‐cellulose content of the C‐2 sample at different DES reuse cycles.

To evaluate the extraction efficiency, the effects of six critical parameters, including the types of HBA and HBD, the types of agricultural residues, reaction times, reaction temperature, molar ratio of HBA and HBD, as well as liquor ratio, were systematically investigated in view of the indexes for examining weight loss ratio (Figure S12). Cellulose separation yielded excellent results at 140°C for 4 h using DES synthesized with ChCl and AA at 1:2 molar ratio. However, agricultural residues showed complicated structure, miscellaneous ingredients, and robust integration between components, and thus a single‐step DES process yielded cellulose substance containing α‐cellulose of 76.5% and impurities of 23.5%, unable to meet the requirements of high‐quality cellulose (Figure 2f). The presence of non‐cellulosic components hindered dissolution and spinning performance. To address this limitation, an environmentally‐friendly and recyclable Soxhlet extraction pretreatment using water and ethanol was implemented to remove dirt, waxes, and extractable oily matters, eliminating approximately 30% of polysaccharide components, and increasing the spatial distance between carbohydrates and lignin (Figure S13). Following this, the pretreated biomass was subjected to a DES treatment, and the results showed that the subsequent delignification step produced Agro‐cellulose with a α‐cellulose content of 87.4%, accompanied by nearly complete hemicellulose removal (from 25%) and a reduction of lignin content from 31% to 3%. Dynamic monitoring of DES treatment of the C‐2 sample (Figure 2g) revealed that non‐cellulosic decomposition predominated in the early stage, consistent with simulation results (dynamic monitoring of the C‐1 sample in Figure S14). A two‐step DES process further increased cellulose purity to 91.2%. However, prolonged acid exposure reduced crystallinity and degree of polymerization (DP) of the obtained cellulose, resulting in partial damage to the cellulose framework and limiting its spinnability.

The traces of cellulose separation were also examined though morphologies evolution (Figure S15). As treatment intensity increased, non‐cellulosic components progressively detached from the surface of cellulose, gradually exposing larger cellulose lamellae. The two‐step DES treatment, however, caused a notable destruction of the crystalline structure in the C‐3 sample, leading to a flocculent morphology, which was further validated by subsequent XRD and DP analyses. The enhancement of peaks corresponding to α‐cellulose in the XRD spectrum confirms the effective removal of the amorphous phases via the DES treatment (Figure 2h). XRD patterns exhibited distinct diffraction peaks at 2θ = 15.6°, and 22.6°, corresponding to the (110) and (200) crystallographic planes of cellulose I, respectively (Figures 2i,j and S16). Also, the integrated area of the amorphous region gradually decreased with increasing treatment intensity. Additionally, the major intensity peak of the C‐3 sample at 2θ = 22.6° became slightly soft due to the damage of the cellulose crystalline structure. The obtained cellulose substance exhibited a clear increase in crystallinity to 68.0%, 72.6%, and 69.5% for the C‐1, C‐2, and C‐3 samples, respectively (Figure S17). The structural integrity of obtained cellulose was confirmed though FTIR spectra (Figure 2k and Table S1), as identified by exhibiting characteristic peaks of the cellulose backbone structure, primarily including the stretching vibration of –OH around 3420 cm⁻¹, the symmetric bending vibrations of –CH₂ in the range of approximately 1320 cm⁻¹ to 1420 cm⁻¹, and the stretching vibration of C–O–C near 1064 cm⁻¹. Also, absorption bands associated with lignin (Figure S18) have disappeared after effective delignification. The C‐2 sample, subjected to Soxhlet extraction followed by DES treatment, exhibited the optimal DP value of 596 (Figure 2l), whereas C‐3 showed a substantial decline due to over‐degradation under extended acid exposure, consistent with XRD results. The removal of the amorphous frictions improved the thermal stability of biomass (Figure S19). Importantly, the DES system exhibited strong recyclability, maintaining high extraction efficiency over five reuse cycles (Figures 2m and S20). Although a slight decline in α‐cellulose content was observed due to the accumulation of dissolved impurities, the extracted Agro‐cellulose from the fifth cycle still met the purity requirements for the subsequent spinning process. This confirms the economic and environmental viability of the DES process for large‐scale cellulose separation.

2.2. Dissolution‐Regeneration Mechanism and Structural Evolution of Agro‐RCFs

The fabrication of Agro‐RCFs involves two key stages, namely dissolution and regeneration of cellulose. Cellulose dissolution in NMMO is a physical process in which the low‐concentration NMMO aqueous solution initially penetrates the amorphous regions of cellulose, causing swelling (Figure S21). As the molar ratio of NMMO to water molecules approaches approximately 1:1, the highly polar N─O bond of NMMO facilitates the formation of new hydrogen bonds with hydroxyl groups on cellulose [30], thereby disrupting the original hydrogen‐bonding network of cellulose (Figure S22). The dissolution of cellulose is achieved when the interchain hydrogen bonds become completely disrupted [31]. MD simulations were employed to investigate the dissolution kinetics of cellulose bundles in NMMO aqueous solution and the conformational changes of cellulose molecular chains during dissolution [32]. A cellulose bundle composed of seven glucose single chains with a degree of polymerization of 8 was built in Figure S23. The cellulose bundle underwent positive dissolution in the initial phase, steady dissolution followed by an accelerated dissolution phase, with complete dissolution achieved by 230 ns (Figure 3a). The temporal evolution of intra‐ and intermolecular hydrogen bonds (Figure 3b) directly reflected the progression of dissolution, consistent with the dynamic process. The number of hydrogen bonds between cellulose and NMMO increased, whereas those among cellulose chains decreased (Figure S24), confirming the replacement of native hydrogen bonds by NMMO coordination. The disappearance of visible cellulose and appearance of dispersed polymer chains further verified the dissolution (Figure S25). A small residue observed in the C‐1 sample after 3 h was attributed to trace lignin impurities. Radial distribution functions (RDFs) analysis revealed that the primary interaction site of NMMO with cellulose was the oxygen atom [33] (Figure S26). Water molecules additionally boosted dissolution through cooperative hydrogen bonding within the NMMO monohydrate. The rise in root‐mean‐square deviation (RMSD) values of the cellulose bundle initiated at about 75 ns in a stepwise manner and reached a high value at 300 ns, reflecting progressive chain diffusion and molecular dispersion (Figure S27). The regeneration stage proceeded via a reverse substitution mechanism, in which NMMO molecules were sequentially replaced by water, leading to the reformation of intermolecular and intramolecular hydrogen bonds between cellulose chains as water was removed during the dehydration process [34]. MD simulation of the regeneration process showed that dissolved cellulose chains initially exhibit a disordered, dispersed state and subsequently aggregate and precipitate through solvent‐nonsolvent double diffusion during water penetration (Figure 3c). The hydrogen‐bond evolution (Figure 3d) demonstrated dynamic reorganization and eventual stabilization of a new hydrogen‐bond network among cellulose chains. Correspondingly, the number of inter‐chain hydrogen bonds progressively increased, and the interactions between cellulose and NMMO gradually diminished (Figure S28). The antiparallel alignment of cellulose chains in regenerated cellulose induced hydrogen‐bond redistribution and lattice reconstruction, thus exhibiting lower energy requirements, tighter interchain packing, and enhanced structural stability [35] (Figure S29).

FIGURE 3.

Mechanism of cellulose dissolution and regeneration and chemical structures of Agro‐RCFs. (a,c) Time evolution of Agro‐cellulose dissolution and regeneration processes. (b,d) Evolution of the number of hydrogen bonds during dissolution and regeneration. (e,f) Morphologies of Agro‐RCFs from the C‐2 sample by dry‐jet wet spinning and wet spinning. (g) Solid‐state ¹³C NMR spectra of natural and regenerated Agro‐cellulose. (h) XRD patterns of Agro‐RCFs. (i) Comparison of crystallinity index. (j) Rheological behavior analysis of spinning solution. (k,l) Stress‐strain curves and corresponding comparison of tensile strength, elongation, and toughness of corncob‐derived Agro‐RCFs with different cellulose substances and spinning technologies. (m,n) Stress‐strain curves and corresponding comparison of tensile strength, elongation, and toughness of corncob‐derived Agro‐RCFs with different cellulose concentration.

The surface morphology of Agro‐RCFs produced from dry‐jet wet spinning and wet spinning exhibited clear differences, as illustrated in Figures 3e,f and S30. Agro‐RCFs obtained via dry‐jet wet spinning displayed smooth and compact surfaces, whereas those from wet spinning exhibited distinct regular prismatic stripes, likely originating from rapid diffusion of NMMO molecules bound to cellulose chains during fiber formation. In the Agro‐RCFs fabrication process, cellulose underwent a crystalline phase transition from cellulose I to cellulose II [36] (Figure S31). The NMR spectra of natural Agro‐cellulose and regenerated Agro‐cellulose clearly confirmed this configuration transformation [37] (Figure 3g). The characteristic crystalline polymorph of cellulose II of regenerated Agro‐cellulose was further corroborated by the XRD analysis in Figure 3h. The obtained Agro‐RCFs exhibited variations in crystallinity index (Figure 3i), with fibers derived from the C‐2 sample reaching 68.2%, significantly higher than others, attributed to nearly complete lignin removal and retention of the cellulose integrity. Since metal ions could accelerate the decomposition of NMMO, the DES strategy provided an additional advantage in efficiently removing metallic impurities [38] (Figure S32). Meanwhile, carboxyl groups introduced from the HBD during DES extraction enhanced cellulose solubility in NMMO [39] (Figure S33). Moreover, the intrinsic quality of Agro‐cellulose was a decisive determinant for fiber performance. The higher the purity and the lower the DP of cellulose, the lower the viscosity of the spinning dope, thereby promoting spinnability [40] (Figure 3j). While increased Agro‐cellulose purity generally enhanced the mechanical performance of the fibers, an excessively low DP compromised these properties despite high purity levels. Consistent with this, Agro‐RCFs derived from the C‐2 sample exhibited superior tenacity than those from C‐3 (Figure 3k and Table S2). Compared with the mechanical properties of the obtained Agro‐RCFs from the two spinning technologies, the fiber produced by dry‐jet wet spinning demonstrated higher tenacity and modulus but slightly lower elasticity than those from wet spinning (Figure 3l). This underscored the positive influence of the dry‐jet wet spinning process on the orientation and crystallization of cellulose chains. Furthermore, partial retention of hemicellulose promoted the formation of additional hydrogen bonds between cellulose macromolecules and improved plastic connectivity in amorphous regions, which facilitated energy dissipation and external forces absorption, resulting in higher toughness (Figure S34). Additionally, fiber properties were sensitive to the cellulose concentration in the spinning solution (Figure S35). Within a certain range, the higher the concentration, the greater the mechanical properties. As shown in Figure 3m,n, Agro‐RCFs prepared from a 7 wt% cellulose concentration proved optimal mechanical performance, with tensile strength of 196 MPa and toughness of 22 MJ m⁻³. However, excessively high concentrations restricted cellulose solubility and rose viscosity, negatively affecting fiber performance. These findings highlight the necessity of co‐optimizing both cellulose quality, molecular characteristics, and spinning parameters to achieve high‐performance Agro‐RCFs.

2.3. Structure‐Programmed Design of Agro‐RCFs with Nanofibril Structure

While Agro‐RCFs have been successfully fabricated, their mechanical performance remains comparable only to that of viscose fibers, failing to meet the requirements for advanced structural and functional applications. Reported studies indicate that the precise control of regeneration conditions enabling the construction of nanofibril architectures and the enhancement of molecular orientation can substantially strengthen cellulose fibers [41]. However, achieving such well‐ordered nanofibril structures through an energy‐efficient, universal, and scalable strategy remains a grand challenge. Here, we proposed a simple yet versatile approach for designing hierarchically structured regenerated fibers via space‐induced alignment of nanofibrils, avoiding excessive time and energy consumption as well as cumbersome postprocessing. Cellulose chains existed as extended worm‐like conformations in NMMO aqueous solution, and easily arranged in parallel to form nanoscale fibrils [21]. During the spinning process, the spinning solution passed through a trumpet‐shaped inlet into a preforming channel, where the cellulose molecular chains initially underwent shear‐induced alignment and subsequently developed radial orientation along a flow path. Furthermore, under followed drafting forces, the cellulose chains were further straightened in the air gap before entering the coagulation bath, where preliminary fiber formation occurred [18] (Figure 4a). A 20 wt% NMMO aqueous solution was employed instead of lower‐concentration NMMO solutions to decelerate the regeneration kinetics. Under stretch‐induced alignment, the cellulose molecular chains adopted a more radial distribution, reducing interchain distances and strengthening hydrogen bonding. Upon drying, spatially confined aggregation ultimately led to the formation of a nanofibril network, endowing the Agro‐RCFs with exceptional mechanical strength and toughness (Figures 4b and S36). The novel Agro‐RCFs exhibited excellent mechanical performance compared with other reported biomass‐derived regenerated fibers, as shown in Figure 4c and Table S3.

FIGURE 4.

Synthetic mechanism, chemical structure, and mechanical properties of pre‐stretched Agro‐RCFs. (a) Schematic representation of the spinning process. (b) Schematic illustration of the pre‐stretching strategy for fabricating anisotropic nanofibril‐structured Agro‐RCFs. (c) Comparison of the mechanical properties of regenerated cellulose fibers derived from common biomass sources. (d) Cross‐sectional schematic diagram and corresponding SEM images of Agro‐RCFs. (e) TEM image of exfoliated nanofibrils from stretched Agro‐RCFs after mechanical disintegration. Azimuthal‐integrated intensity distribution curves of (f) 2D WAXD patterns and (h) 2D SAXS patterns. The degree of orientation and corresponding intensity profiles from (g) 2D WAXD and (i) 2D SAXS. (j) XRD pattern and (k) corresponding crystallinity index of Agro‐RCFs at different drawing ratios. (l) Comparison of fiber diameters under various drawing ratios. (m, n) Stress‐strain curves and corresponding comparison of tensile strength, elongation, and toughness of Agro‐RCFs under different drawing ratios.

To investigate the mechanism underlying the remarkable reinforcement of nanofibril‐structured fibers, morphological and structural analyses were conducted. Compared with common Agro‐RCFs, pre‐stretched Agro‐RCFs demonstrated the formation of densely packed fibrillar bundles aggregating with preferential orientation and nanoscale compartmentalization, as verified by cross‐section SEM imaging (Figure 4d). The observed high degree of alignment originated from shear‐induced sliding and rearrangement of cellulose molecule chains during drawing. The successful exfoliation of nanoscale fibrils from Agro‐RCFs directly verifies the existence of a hierarchical nanofibrillar architecture (Figure 4e and S37). Agro‐RCFs with different drawing ratios were fabricated from the C‐2 sample (Figure S38). The ordered structures of Agro‐RCFs at different drawing ratios were elucidated with wide‐angle X‐ray diffracting techniques (WAXD) and small‐angle X‐ray scattering techniques (SAXS) [23]. Agro‐RCFs without the stretching process showed weak equatorial arcs and faint longitudinal features in the 2D WAXD and SAXS patterns along the (110) scattering plane, respectively (Figure S39). In contrast, stretched Agro‐RCFs displayed sharper equatorial reflections in WAXD and elongated meridional features in SAXS, indicating heightened anisotropy arising from nanofibril alignment. Herman's orientation parameter (fc) provides a quantitative measure for molecular orientation based on the azimuthally integrated intensity distribution curves of X‐ray scattering patterns (Figure 4f,h). As the drawing strain increased from 1× to 20×, the fc values of Agro‐RCFs exhibited a progressive rise from 0.66 to 0.82 according to WAXD results and from 0.76 to 0.85 based on SAXS measurements (Figure 4g,i). The elevated fc values observed in heavily strained Agro‐RCFs validated the establishment of a long‐range oriented nanofibril network aligned parallel to the stretching axis [41]. Meanwhile, the Agro‐RCFs displayed distinct birefringent colors under crossed polarizers (Figure S40), revealing their intrinsic anisotropic ultrastructure. These findings strongly supported the effectiveness of the preorientation strategy combined with air‐drying densification for stabilizing oriented nanofibril architecture in the final Agro‐RCFs. Consistently, SAXS intensity profiles of stretched Agro‐RCFs showed smooth scattering curves free of aggregation or interparticle interference, further verifying uniform nanofibril dispersion [42] (Figure S41). XRD analysis confirmed Agro‐RCFs possessing a typical cellulose II crystalline structure with a monoclinic unit cell (Figure 4j). The characteristic reflections ($\overline{1}10$), (110), and (020) were located on the equator, and (002) was located on the meridian, while the non‐(hk0) reflections appeared at the off‐axis positions, which indicated that the crystalline structure was preferred to orient along the fiber axis. Increasing the draw ratio resulted in an obvious reduction in fiber diameter, as well as a slight enhancement in crystallinity (Figure 4k,l). Meanwhile, the crystallite sizes calculated from the Scherrer equation increased from 2.42 to 3.55 nm, indicating the development of larger coherent cellulose crystalline domains (Figure S42). Consequently, the optimally drawn Agro‐RCFs demonstrated remarkable mechanical performance and flexibility. The tensile strength of Agro‐RCFs was significantly enhanced from 188 MPa to 852 MPa as the drawing ratio rose from 1× to 20×, showing a 353% improvement (Figure 4m,n, and Table S4). Notably, even at moderate draw ratios of 5× and 10×, strength increases of 153% and 191% were achieved, respectively. These results demonstrated that hierarchical nanofibril alignment and hydrogen‐bond densification synergistically translate molecular orientation into macroscopic toughness, further enabling remarkable mechanical stability, aqueous resistance, and thermal robustness (Figure S43). The outstanding strength and practical applications of Agro‐RCFs make them strong candidates for advanced sustainable applications, providing a high‐value route for the efficient utilization of agricultural residues and supporting the transition toward a circular bioeconomy.

2.4. System Assessment of Universality and Environmental Viability

This study presents a reliable, scalable, and universally applicable strategy for manufacturing high‐value Agro‐RCFs. Through a multi‐stage gradient purification technology, efficient cellulose extraction was achieved from diverse agricultural residues, including rice straw, wheat straw, rice husk, corn stover, and peanut shell, followed by successful dissolution and spinning into Lyocell fibers with the stretch‐induced alignment and spatial confinement strategy (Figures 5a,b and S44). Consistent with the aforementioned separation method, DES was applied for delignification, effectively removing over 70% of lignin and more than 90% of hemicellulose while preserving cellulose integrity (Figure 5c). The extracted Agro‐cellulose exhibited excellent properties, with purity exceeding 85% and DP over 350 (Figure 5d). Among the displayed agricultural residues, Agro‐cellulose derived from corn stover demonstrated more desirable performance, achieving a DP of 520 and crystallinity of 62% (Figures S45 and S46). The extracted cellulose was converted into regenerated fibers through NMMO dissolution and the dry‐jet wet spinning technology (Figure S47). After 20‐fold stretching, the tensile strength and work of fracture of Agro‐RCFs simultaneously enhanced by approximately 6–8 times and 10–20 times, respectively, demonstrating the significant reinforcing effect of stretch‐induced nanofibril alignment and hydrogen‐bond densification (Figure S48). Agro‐RCFs derived from wheat straw exhibited the highest tensile strength, whereas Agro‐RCFs derived from peanut shell showed superior elongation property (Figure 5e,f). However, compared with Agro‐RCFs derived from corncob, the mechanical performance of fibers from extended agricultural residues still had certain gaps, primarily attributed to the significant variations in the chemical components among biomass resources, such as the high ash content of 15%–20% in rice husk [43]. The successful transformation of heterogeneous agricultural wastes into high‐quality regenerated cellulose fibers not only provides an efficient pathway for biomass valorization but also mitigates agricultural pollution and resource underutilization, thereby embodying the core principles of the circular bioeconomy. The demonstrated material adaptability and process scalability position this approach as a promising platform for sustainable biomass refinement within the textile sector.

FIGURE 5.

The universality and environmental impacts of Agro‐RCFs production. (a) Morphology of extracted Agro‐cellulose. (b) Morphology of corresponding Agro‐RCFs. (c) Component content of cellulose, hemicellulose, and lignin in raw biomass and extracted Agro‐cellulose. (d) DP value analysis of raw biomass and Agro‐cellulose. (e, f) Stress‐strain curves and corresponding comparison of tensile strength, elongation, and toughness of Agro‐RCFs. (g) Contribution analysis results per kg of Agro‐RCFs. (h–r) Environmental impacts of Agro‐RCFs compared to viscose fiber from wood pulp and lyocell fiber from cotton linter pulp (per cm³ MPa⁻¹).

To quantitatively evaluate the environmental impacts of Agro‐RCF production, a comprehensive cradle‐to‐gate life cycle assessment (LCA) was executed [44]. The whole process of Agro‐cellulose extraction and Agro‐RCFs fabrication was designed to be simplified and environmentally benign, minimizing reagent use and energy consumption, which inherently contributed to a lower overall footprint. The assessment revealed that Agro‐RCFs exhibited markedly lower environmental impacts across multiple categories, including Marine Aquatic Toxicity Potential (MATEP), Abiotic Depletion Potential for Fossil Resources (ADP‐Fossil), Freshwater Aquatic Toxicity Potential (FATEP), Global Warming Potential (GWP), Human Toxicity Potential (HTP), Terrestrial Ecotoxicity Potential (TEP), Acidification Potential (AP), Eutrophication Potential (EP), Photochemical Ozone Creation Potential (POCP), Abiotic Depletion Potential (ADP), and Ozone Depletion Potential (ODP) [45, 46]. Water utilization in the spinning stage was a great contributor to exceeding 70% ODP, HTP, TEP, and MATEP, ethanol consumption in extraction accounted for a large proportion of EP, AP, and POCP, and electricity use represented more than 30% to ADP and FATEP (Figures 5g and S49a). Meanwhile, a life cycle impact assessment (LCIA) was meticulously conducted in comparison to viscose fibers derived from wood pulp (V‐W) and Lyocell fibers derived from cotton linter pulp (LC‐C) (Figures 5h–r and S49b–l). The detailed process and material losses for each production pathway are summarized in Figures S50–S52 and Tables S5–S7. Across all environmental categories, Agro‐RCFs production process consistently demonstrated the lowest impacts, which underscored the substantial environmental advantages over existing viscose and Lyocell technologies (Tables S8 and S9). Furthermore, the economic feasibility of industrial‐scale production of Agro‐RCFs was further ascertained through a comprehensive cost assessment analysis (Table S10) [47, 48]. Results indicated Agro‐RCFs had a clear economic superiority, with production costs significantly lower than those of industrial viscose and Lyocell fibers by 72.09% and 66.43%, respectively (Figure S53). Interestingly, the contribution of water and ethanol to the total production costs represented 21.96% and 26.80%, respectively, making the material expenses the main cost factors (Figure S54). Hence, enhanced recycling and recovery of solvent and water would lead to an additional cost reduction of approximately 50%. Collectively, these findings highlight that the key ecological and economic benefits of Agro‐RCFs production lie in its superior recyclability and closed‐loop solvent recovery. This process not only complies with the principles of green chemistry but also advances the efficient utilization of renewable biomass resources. Accordingly, Agro‐RCFs emerge as a cost‐effective, environmentally sustainable, and industrially viable alternative to traditional fibers, establishing a viable pathway for sustainable fiber production within the circular bioeconomy.

3. Conclusions

This study establishes a scalable and environmentally benign route for the high‐value utilization of agricultural residues through the fabrication of high‐performance Agro‐RCFs. The DES system efficiently extracted Agro‐cellulose with an α‐cellulose content of 91.2% and a crystallinity of 72.6%, confirming its strong delignification and structural preservation capabilities. Moreover, the DES exhibited excellent recyclability, maintaining extraction efficiency over five consecutive reuse cycles, thereby underscoring both its economic and environmental feasibility. The resultant Agro‐RCFs, produced via a dry‐jet wet spinning process under shear flow and stretch‐induced alignment, developed a hierarchical nanofibril structure that endows the fibers with exceptional mechanical performance, achieving tensile strength exceeding 852 MPa and toughness reaching 110 MJ m⁻³. Beyond eliminating the use of toxic reagents and preventing hazardous emissions, this approach establishes full‐process sustainability. The proposed strategy not only bridges the performance gap between bio‐based and synthetic fibers but also provides a practical solution for the universal and circular utilization of low‐value biomass. With its scalability, resource efficiency, and environmental compatibility, this method holds considerable promise for the application of Agro‐RCFs in sustainable textiles, biomedical materials, industrial reinforcements, and emerging flexible and aerospace devices, advancing the development of a low‐carbon and circular bioeconomy.

4. Experimental Section

Experimental details are available in the Supporting Information.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Supporting File 1: adma74131‐sup‐0001‐SuppMat.docx.

Supporting File 2: adma74131‐sup‐0002‐VideoS1.mp4.

Supporting File 3: adma74131‐sup‐0003‐VideoS2.mp4.

Supporting File 4: adma74131‐sup‐0004‐VideoS3.mp4.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.