Table 2. Overview of Current Preparation/Synthesis Methods for Nanocellulosic Materials.

type of nanocellulosic	preparation/synthesis methods	refs
CNF/CNCs	acid hydrolysis of cellulose pulp in the presence of either mineral or organic acid	(97) and (98)
	enzymatic hydrolysis employing the cellulose enzyme. Although an environmentally friendly route, it is very expensive
	subcritical water extraction. Also, an environmentally friendly method but nanocellulosics obtained from this method demonstrate instability in suspension
	transition metals catalysis such as Fe(III), Co(II), etc., have been used for effective hydrolysis for obtaining nanocellulosic materials from cellulose pulp, thereby reducing the use of acids
	ionic liquid hydrolysis methodology. Notwithstanding the noteworthy efficiency in using this process for NC production, they, however, come with drawbacks such as toxicity, high-cost implications, and high chemical footprints
	deep eutectic solvents hydrolysis. Similar to ionic liquids; however, it eliminates some noted drawbacks associated with the use of ionic liquids for cellulose pulp hydrolysis which includes lower-cost implications and simplicity
BNC	fermentation process. However, it comes with challenges such as the long cultivation period	(99−101)
	bioreactor process