## 3 Results and Discussion
### Characterization of Cellulose Fibers
#### 3.1.2 Morphological Analysis  
The morphological features of the obtained samples were examined using optical microscopy (Figure 4) and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (EDS) analysis (Figure 5). In the optical image of the untreated grass clippings (Figure 4a), microstructured fibers of various sizes and orientations are evident. The sample exhibits individual, non-woven fibers with high density, and in some areas, fibers are adhered together, forming a complex network of intertwined structures. Following mechanical grinding, alkaline treating (Figure 4b), and bleaching (Figure 4c), visible alterations in the structure and texture of the grass clipping sample are observed in both optical and scanning microscopy images. External fibrillation, resulting from mechanical and chemical-thermal influences, is evident, leading to the destruction of fiber surfaces and the separation of fibrils, observed as \"lint\" on the fiber surfaces [68]. Internal fibrillation causes swelling and hydrating hemicellulose within the fibers, weakening or breaking fiber bonds [69]. The images illustrate a noticeable brightening and homogenization of the sample surface, indicative of removing specific components such as lignin and hemicellulose. Microdispersed fibers of varying lengths and diameters are visible and presented as tangled and unoriented structures. The presence of microdispersed fibers suggests the retention of the fibrous structure of the grass material following all chemical-thermal treatment processes. Following alkaline treatment, the average fiber diameter significantly decreases, typically measuring around 13.5 microns. Subsequent bleaching results in a further reduction in fiber diameter, averaging approximately 4.5 microns. This notable decrease indicates extensive delignification and an increase in cellulose purity. A detailed examination of the morphological and structural features of the untreated grass clippings using SEM images (Figure 5) revealed fragments of various shapes and sizes. Microscopic analysis indicates that these fragments exhibit diverse surface characteristics, with some displaying smooth surfaces while others appear uneven and rough. This structural variation suggests the presence of different types of cells and tissues comprising the grass structure. The microscopic examination reveals that the grass fragments exhibit a porous structure, with microscopic pores and cavities distributed across the sample surface, indicative of the grass's complex internal anatomy. However, the presence of various contaminants, such as waxes, oils, and other impurities, is notable and may fill the porous structure of the grass. To further elucidate the chemical composition of the original sample, EDS spectra were obtained (Figure S1), revealing the mass content of elements as follows: C\(\rightarrow\)57.49 wt.% and O\(\rightarrow\)35.52 wt.%. Additionally, impurities of the following elements were identified: Mg (0.10), Si (3.41), P (0.15), S (0.17), Cl (0.59), K (2.18), and Ca (0.39) wt.%. Following alkaline treatment, the fiber surface becomes more prominent than the untreated samples, as confirmed by the SEM images (Figure 5). A notable reduction in surface defects suggests removing non-cellulosic components and redistributing cellulose chains under the influence of elevated temperatures and chemical reagents. The results show that morphological and structural changes occur in the feedstock after alkaline treatment. Elemental mapping of grass clippings after chemical-thermal treatment, according to the EDS analysis, indicates that the sample primarily comprises C (45.25 wt.%) and O (53.08 wt.%), with minor amounts of Na (0.21), Si (0.67), and Ca (0.79 wt.%). For further insights, the EDS spectra of the sample under investigation are also available (Figure S2). The SEM images of isolated cellulose samples after bleaching show significant alterations in the material's structure (Figure 6).