**2.2 Chemical composition**

Mannai et al. [25, 26] are the first ones to have studied the chemical composition of lignocellulosic fibers from *Opuntia* (Cactaceae) trunk. For comparison purposes, the results of this and other chemical compositions of *Opuntia* cladode studied by Malainine et al. [39] and some lignocellulosic raw materials from plant biomass collected from literature were summarized in **Table 2**.

A lower content of Klason lignin was observed in the *Opuntia* trunk and cladode and does not exceed 5 wt% (as opposed to other plants), indicating that *Opuntia* genus was a non-woody plant. The total holocellulose contents (64 wt%) were


#### **Table 2.**

*Chemical composition (ash; K. lig, Klason lignin; Holocel, holocellulose; and α-cell, α-cellulose) of* Opuntia *(Cactaceae) trunk and other values obtained for cladode and their comparison with several lignocellulosic plants (w/w%).*

*Novel Trend in the Use of* Opuntia *(Cactaceae) Fibers as Potential Feedstock… DOI: http://dx.doi.org/10.5772/intechopen.92112*

similar to that found in *olive trimmings*, hardwood, softwood, vine stems, and some annual plants; and it was clearly higher than those obtained for carrot leaves, amaranth, banana stems, and *Posidonia oceanica* balls; but it was lower than the holocellulose content measured for date palm rachis, rapeseed straw, and Alfa stems. In general, the holocellulose content can provide information about the quality and quantity of the produced pulp and paper [52]. The measured α-cellulose rate was surprisingly higher in the trunk (around 53.6 wt%) than those obtained for cladode (21.6 wt%) and other plants (**Table 2**); it was slightly lower than in *olive trimmings*. Non-wood fibers are handled in ways specific to their composition, and it was also acceptable for papermaking applications and corresponded to paper with enhanced strength [22]. For this reason, the processes used for the delignification of lignocellulosic fibers from *Opuntia* were adapted in very soft conditions to minimize degradation of the fibers and thus maximize pulp yield.

A very small fraction of inorganic compound (5.5 wt%) was observed in the trunk compared to the total mineral amount in the cladode, *Posidonia oceanica balls*, and banana stems; however, it was comparable to the values estimated for date palm rachis; but it was significantly higher than the ash contents measured for rapeseed straw, *olive trimmings*, Alfa stems, *Eucalyptus citriodora* and vine stems, and some annual plants (**Table 3**). The lower fraction of minerals in lignocellulosic fibers from the *Opuntia* trunk presents a major advantage, and the utilized raw material was silica free, which was extremely important for papermaking [25]. The chemical composition of ash was determined with elemental analysis and reported for the first time by Mannai et al. [25]. The resulting proportions, as seen in **Table 3**, are compared with other plants (amaranth, *Astragalus armatus*, date palm rachis, and banana pseudo stems) and have shown that the elemental composition of mineral contents in *Opuntia* can vary considerably from one species to another. A very low fraction of silicon (0.2 wt%) observed for *Opuntia* than those of other raw materials led to good separation after chemical delignification. It is clear that calcium and magnesium are the predominant inorganic materials in the Cactaceae family (18.33 and 16.54 wt%). The high presence of calcium due to the calcium oxalate crystals present naturally in *Opuntia* species [9, 25, 26]. The mineral elements present in this raw material do not present any counterindication for chemical pulping, composite manufacturing, and the area of the extraction of various cellulosic derivatives.


**Table 3.**

*Ash composition of* Opuntia *(Cactaceae) trunk in comparison with data from previously published studies.*

in geometric shape, layer thicknesses, fiber width, pore area distributions, fiber density, and bifurcation of primary fibers. It is worth noting that the flexural properties measured from the peripheral F-N layers are higher than those *O. ficusindica* studied by Greco and Maffezzoli [34] and are lower than those found for *Myrtillocactus geometrizans* studied by Schwager et al. [36]. As expected, the F-N structural and geometric aspects modify the tensile and flexural states in such a way that the maximum elastic modulus shifts in an axial direction. This shift can be explained by the primary fiber orientation, which is axially aligned in most of the regions in the direction of the principal stresses and primary fiber density, on a macroscopic level. Mannai et al. [9] and El Oudiani et al. [38] affirmed and confirmed that the major factors that influence the F-N tenacity and elongation and give good mechanical properties include (i) the hierarchical structure; (ii) the unit cell dimensions (large and thick-wall parenchyma cells, long fiber bundles, and the densely distributed periderm with thick cell edges); and, on a microscopic level, (iii) the degree of crystallinity and (iv) the chemical composition of the fibers.

*Invasive Species - Introduction Pathways, Economic Impact, and Possible Management Options*

Mannai et al. [25, 26] are the first ones to have studied the chemical composition of lignocellulosic fibers from *Opuntia* (Cactaceae) trunk. For comparison purposes, the results of this and other chemical compositions of *Opuntia* cladode studied by Malainine et al. [39] and some lignocellulosic raw materials from plant biomass

A lower content of Klason lignin was observed in the *Opuntia* trunk and cladode and does not exceed 5 wt% (as opposed to other plants), indicating that *Opuntia* genus was a non-woody plant. The total holocellulose contents (64 wt%) were

**Plant Ash K. lig Holocel α-cell** *Opuntia* (Cactaceae) trunk [25] 5.5 4.8 64.5 53.6 *Opuntia* (Cactaceae) cladode [39] 19.6 3.6 — 21.6 Date palm rachis [40] 5 27.2 74.8 45 Carrot leaves [41] — 18.51 52.8 31.5 Rapeseed straw [42] 3.4 16 78.9 41.6 Amaranth [43] 12 13.2 58.4 32 *Olive trimmings* [44] 1 18.9 64.7 59 Softwood [45] — 25–31 65–74 40–45 Harwood [45] — 16–24 67–82 43–47 Alfa [46] 3.7 22.3 68.2 46.1 *Eucalyptus citriodora* [47] 0.8 22.7 — 48.2 *Posidonia oceanica* balls [40] 12 29.8 61.8 40 Vine stem [48] 3.9 28.1 65.4 35 Banana stem [49] 7.1 11.1 43.60 — Annual plants [50, 51] 2–6.2 17–26 52–70 36–46

*Chemical composition (ash; K. lig, Klason lignin; Holocel, holocellulose; and α-cell, α-cellulose) of* Opuntia *(Cactaceae) trunk and other values obtained for cladode and their comparison with several lignocellulosic*

**2.2 Chemical composition**

**Table 2.**

**148**

*plants (w/w%).*

collected from literature were summarized in **Table 2**.
