## 3 L-MMCF Cellulose Feedstock Sources  
L-MMCF are manufactured from high alpha-cellulose feedstock, typically from eucalyptus or beech trees, bamboo, or cotton linters [6; 24]. Researchers have also explored alternative feedstock sources such as industrial hemp (bast and hurd), sugarcane bagasse, kudzu, and corn cobs [7; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50]. Details on the L-MMCF process from traditional L-MMCF feedstocks (e.g., wood, bamboo, cotton linters) are provided here in addition to alternative agriculture feedstocks, specifically industrial hemp stalks, so that the utilisation of the traditional sources, specifically wood, can be contrasted to that of industrial hemp stalks. The economic and environmental implications for the utilisation of alternative feedstocks towards L-MMCF manufacturing are discussed in Section 5.  
Figure 4 illustrates the similarities in the cross section of a mature tree stem vs. an industrial hemp stalk [38; 51]. Both plants have an outer bark [52; 53]. Next comes bast fibre, resembling the inner bark (or phloem) and cambium sections, which is the primary source of alpha cellulose [38; 54; 55]. Hemp hurd, or shive, resembles sapwood, which comprises the vascular tissue of the tree (i.e., xylem or jth) [55]. It is to be noted that hemp stalks are defined as woody in terms of both physical and morphological properties (e.g., density, stiffness) [56; 57; 58; 41].  
L-MMCF manufacturing requires a high percentage of alpha-cellulose (typically greater than 92%) and low hemicellulose and lignin [16; 18]. Knowing the composition of the cellulose for each step of the L-MMCF manufacturing process and parameter requirements (i.e., time, temperature, and pressure), including prehydrolysis and pulping to remove hemicellulose and lignin, respectively, allows for better control of the final dope solution and rheological properties for extrusion. High lignin content can affect dissolution of cellulose in NMMO (i.e., high lignin can result in incomplete dissolution, creating irregularities and contamination in the final product), requiring additional filtration steps prior to fibre spinning. Additionally, high lignin content requires harsher bleaching conditions, which in turn affects the degree of cellulose polymerisation.  
Figure 4: Illustration of the cross-section of (**a**) a mature tree stem (reproduced from [38] with permission from TAPPI); (**b**) hemp fibre stock (reproduced from [51] with permission from Textile Exchange).  
Table 2 provides the alpha-cellulose, hemicellulose, and lignin content of various Kraft pulps. With an alpha-cellulose content of 92-96.2% and a relatively low hemicellulose and lignin content, hemp best fibre appears as a viable feedstock for L-MMCF. Hemp hurd has an alpha-cellulose content of 77.6-89.6%, which may be too low as a lone feedstock for L-MMCF; however, it has been successfully manufactured into L-MMCF in lab-scale tests [26]. There may be opportunities to blend hemp hurd with other higher alpha-cellulose feedstocks to provide interesting organoleptic properties to the final L-MMCF [7]. Additional research on hurd is required to determine its suitability as a L-MMCF feedstock. Alpha cellulose, hemicellulose, and lignin content will be discussed further in Section 4.