Abstract

Nanocrystalline cellulose is a renewable nanomaterial that has gained huge attention for its use in various applications from advanced biomedical material to food packaging material due to its exceptional physical and biological properties, such as high crystallinity degree, large specific surface area, high aspect ratio, high thermal resistance, good mechanical properties, abundance of surface hydroxyl groups, low toxicity, biodegradability, and biocompatibility. However, they still have drawbacks: (1) sources of raw materials and its utilization in the production of nanocomposites and (2) high chemical and energy consumption regarding the isolation of macro-sized fibers to nano-sized fibers. The incorporation of hydrophilic nanocrystalline cellulose within hydrophobic polymer limits the dispersion of nano-sized fibers, thus resulting in low mechanical properties of nanocomposites. Hence, surface modification on nano-sized fiber could be a solution to this problem. This review focuses on the advanced developments in pretreatment, nanocrystalline production and modifications, and its application in food packaging, biomedical materials, pharmaceutical, substitution biomaterials, drug excipient, drug delivery automotive, and nanopaper applications.

Keywords: nanocrystalline cellulose, nanocomposites, surface modification, hydrolysis, agro-waste

## 1. Introduction

During the past decades, huge efforts have been made to improve new chemicals and/or materials and replace broadly used petroleum-based products by utilizing biomass renewable feedstock [1–3]. Biocompatible composites and biodegradable plastics produced from biorenewable resources are regarded as promising biomaterials that could replace petrochemical-based polymers and hence reduce global dependence on nonrenewable sources (i.e., fossil fuels: coal, petroleum, and natural gas) and provide simplified recycling or end-of-life disposal [4–10].

Agro-based industry's function is to increase the value of raw agricultural products through downstream processing so that products are marketable, consumable, and

used to generate income and provide profit to the producer [11]. However, there is waste generated through the process of downstream and upstream of agro-industry. The composition of industrial wastes varies depending on the types of industry as different countries apply various categories for industrial waste which contribute adversely to air, soil, and water quality. This is due to some of the industrial wastes which are neither toxic nor hazardous. For example, organic wastes, such as corncob, sugarcane bagasse, sugar palm (fiber, frond, bunch, trunk), areca nut husk fiber, wheat straw fiber, soy hull fiber, pineapple leaf fiber, oil palm (mesocarp fiber, empty fruit bunch, frond), rubber wood thinning, curaua fiber, banana fiber, water hyacinth fiber, wheat straw, sugar beet fiber, etc. that are produced by agro-based industries are not hazardous in nature and thus have potential for other uses [12–14]. Figure 1 shows the by-products of agro-industry that are used for sources of lignocellulose biomass.

Biomass renewable feedstocks are of great interest due to the possibility of nontoxicity, renewability, and biodegradability as well as sustainability [12–17]. Lignocellulosic can be classified as lower-value biomass (LVB). Lower-value biomass (LVB) in forest or agriculture industry constitutes noncommercial material traditionally left on site following harvesting of crops. However, emerging markets for energy, chemicals, and bioproducts have increased incentives to harvest and utilize this material in some cases [20–25]. Lignocellulosic biomass suppliers do not use any kind of wood indiscriminately due to economic and environmental reasons; they usually used mobilized woody biomass sourced from by-products of forest operations, agriculture, and crops' waste as well as the wood industry waste such as sawmills. Lignocellulosic biomass sector has been developed to work in synergy with other agro-based industry and wood-based industries to give value to non-mobilized and/or low-value biomass such as trunk, fiber, sugar cane bagasse, manure bedding, plant stalks, vines, hulls, leaves, vegetable matter, sawdust, mill

residues, thinnings, low-quality wood, tops, and limbs. Biomass generators do not use high-quality timber or main agricultural products, as using lumber or major crops would make the price of biomass wholly uncompetitive for end consumers. Figure 2 shows the by-products of forest operation that are used for sources of lignocellulose biomass. Natural fibers or lignocellulosic fibers can be classified into two main groups that are wood and non-wood bio-fibers (Figure 3). This review will be focusing on production, processes, modification, and application of

Schematic representation of lignocellulosic agro-waste and by-product of forest classification. Adapted from

By-products of forest operation that are used for sources of lignocellulose biomass. Adapted from Ref. [23].

Production, Processes and Modification of Nanocrystalline Cellulose from Agro-Waste: A Review

DOI: http://dx.doi.org/10.5772/intechopen.87001

http://www.europeanbioenergyday.eu/solid-bioenergy-in-questions-an-asset-to-eu-forests/.

2. Lignocellulosic biomass from agro-waste fiber and forest by-products

Lignocellulosic biomass comprises of three major chemical components that are cellulose, lignin, and hemicellulose [18–21]. The chemical compositions of

nanocrystalline cellulose from agro-waste.

Figure 2.

Figure 3.

Ref. [7].

91

#### Figure 1.

By-products of agro-industry that are used for sources of lignocellulose biomass.

Production, Processes and Modification of Nanocrystalline Cellulose from Agro-Waste: A Review DOI: http://dx.doi.org/10.5772/intechopen.87001

#### Figure 2.

used to generate income and provide profit to the producer [11]. However, there is waste generated through the process of downstream and upstream of agro-industry. The composition of industrial wastes varies depending on the types of industry as different countries apply various categories for industrial waste which contribute adversely to air, soil, and water quality. This is due to some of the industrial wastes which are neither toxic nor hazardous. For example, organic wastes, such as corncob, sugarcane bagasse, sugar palm (fiber, frond, bunch, trunk), areca nut husk fiber, wheat straw fiber, soy hull fiber, pineapple leaf fiber, oil palm (mesocarp fiber, empty fruit bunch, frond), rubber wood thinning, curaua fiber, banana fiber, water hyacinth fiber, wheat straw, sugar beet fiber, etc. that are produced by agro-based industries are not hazardous in nature and thus have potential for other uses [12–14]. Figure 1 shows the by-products of agro-industry that are used for sources of lignocellulose biomass. Biomass renewable feedstocks are of great interest due to the possibility of nontoxicity, renewability, and biodegradability as well as sustainability [12–17]. Lignocellulosic can be classified as lower-value biomass (LVB). Lower-value biomass (LVB) in forest or agriculture industry constitutes noncommercial material traditionally left on site following harvesting of crops. However, emerging markets for energy, chemicals, and bioproducts have increased incentives to harvest and utilize this material in some cases [20–25]. Lignocellulosic biomass suppliers do not use any kind of wood indiscriminately due to economic and environmental reasons; they usually used mobilized woody biomass sourced from by-products of forest operations, agriculture, and crops' waste as well as the wood industry waste such as sawmills. Lignocellulosic biomass sector has been developed to work in synergy with other agro-based industry and wood-based industries to give value to non-mobilized and/or low-value biomass such as trunk, fiber, sugar cane bagasse, manure bedding, plant stalks, vines, hulls, leaves, vegetable matter, sawdust, mill

Nanocrystalline Materials

Figure 1.

90

By-products of agro-industry that are used for sources of lignocellulose biomass.

By-products of forest operation that are used for sources of lignocellulose biomass. Adapted from Ref. [23]. http://www.europeanbioenergyday.eu/solid-bioenergy-in-questions-an-asset-to-eu-forests/.

#### Figure 3.

Schematic representation of lignocellulosic agro-waste and by-product of forest classification. Adapted from Ref. [7].

residues, thinnings, low-quality wood, tops, and limbs. Biomass generators do not use high-quality timber or main agricultural products, as using lumber or major crops would make the price of biomass wholly uncompetitive for end consumers. Figure 2 shows the by-products of forest operation that are used for sources of lignocellulose biomass. Natural fibers or lignocellulosic fibers can be classified into two main groups that are wood and non-wood bio-fibers (Figure 3). This review will be focusing on production, processes, modification, and application of nanocrystalline cellulose from agro-waste.

## 2. Lignocellulosic biomass from agro-waste fiber and forest by-products

Lignocellulosic biomass comprises of three major chemical components that are cellulose, lignin, and hemicellulose [18–21]. The chemical compositions of


Fibers

93

Phoenix dactylifera palm rachis

Kenaf core powder

Water hyacinth fiber

Wheat straw Sugar beet fiber

Mengkuang

Table 1. Chemical composition

 of agro-waste

 fibers and forest by-products

 from different plants and different parts.

 leaves

Holocellulose

Cellulose (wt%)

44.0 80.26

42.8 43.2 0.15 44.95 0.09

37.3 0.6

34.1 1.2 25.40 2.06

34.4 0.2

 24 0.8

 11.23 1.66

 17.67 1.54

22.0 3.1

—

 —

—

2.5 0.02

Hemicellulose

 (wt%)

> 28.0

23.58

20.6

4.1

—

 —

——

14.0

2.5

—

 —

55 48.1 59.56

57.5 35.67

55.1

[44]

Production, Processes and Modification of Nanocrystalline Cellulose from Agro-Waste: A Review

[43]

[42]

DOI: http://dx.doi.org/10.5772/intechopen.87001

[41]

[40]

[39]

 (wt%)

Lignin (wt%)

 Ash (wt%)

 Extractives

 (wt%)

Crystallinity

 (%)

 Ref.


Table 1.

Chemical composition of agro-waste fibers and forest by-products from different plants and different parts.

#### Production, Processes and Modification of Nanocrystalline Cellulose from Agro-Waste: A Review DOI: http://dx.doi.org/10.5772/intechopen.87001

Fibers

92

Sugar palm fiber

Sugar palm frond

Sugar palm bunch

Sugar palm trunk

Wheat straw fiber

Soy hull fiber

Areca nut husk fiber

Helicteres isora plant

Pineapple leaf fiber

Ramie fiber

Oil palm mesocarp fiber (OPMF)

Oil palm empty fruit bunch (OPEFB)

Oil palm frond (OPF) Oil palm empty fruit bunch (OPEFB) fiber

Rubber wood

Curaua fiber Banana fiber Sugarcane bagasse

Kenaf bast Phoenix dactylifera palm leaflet

Holocellulose

Cellulose (wt%)

43.88 66.49 61.76 40.56

43.2

56.4

 0.92

34.18

71

81.27

 2.45

69.83

28.2

37.1

45.0

 40 45

70.2

 0.7

7.5 43.6

63.5

 0.5

33.5

17.6

 1.4

26.0

27.0

6.5

—

12.7

 1.5

 2.2

 0.8

4.0

 1.0

18.3

 0.8

74.9 27.7

27.7

—

 —

7.9

0.01

9.3

 0.9

—

 —

9.6

15.0

76 48.2

50

[39]

[38]

[37]

[36]

 3

20

 2

29

 2

—

2.5

 0.5

 2

23

 2

21

 1

—

2.0

 0.2

 0.6

32.0

 1.4

16.9

 0.4

—

2.3

 1.0

 4.4

39.9

 0.75

18.6

 1.3

—

3.1

 3.4

 0.8

32.7

 4.8

32.4

 4.0

—

6.5

 0.1

12.31

 1.35

9.63

3.98

—

 —

3.46

 0.58

—

 —

 2.6

3.1

 0.5

21

 0.9

—

 —

12.5

 0.72

20.83

31.60

2.34

18.0

 2.5

—

 —

—

 0.15

34.1

 1.2

22.0

 3.1

—

 —

Hemicellulose

 (wt%)

> 7.24

14.73 10.02 21.46

23.48 46.44

2.38

6.30

3.38

2.24

18.89

3.05

2.46

33.24

1.01

2.73

55.8

—

—

—

57.5 59.8

37 38 35.97 55.48 34.3 45.0 54.5

40 46 64

[35]

[34]

[34]

[33]

[33]

[33]

[32]

[31]

[30]

[14]

[29]

[29]

[28]

[28]

[28]

Nanocrystalline Materials

[6]

 (wt%)

Lignin (wt%)

 Ash (wt%)

 Extractives

 (wt%)

Crystallinity

 (%)

 Ref.


(length/diameter), high crystallinity, nanoscale size, high strength and stiffness, low density, and highly negative charge which lead to unique behavior in solutions. The high chemical reactivity of the surface makes NCC customizable for various applications, besides their heat stability which allows high-temperature applications. Moreover, they also have huge surface OH groups which provide active sites for hydrogen bonding through the interlocking with nonpolar matrix

DOI: http://dx.doi.org/10.5772/intechopen.87001

Production, Processes and Modification of Nanocrystalline Cellulose from Agro-Waste: A Review

[4, 7, 10, 45, 46]. Nanocrystalline cellulose can be isolated from cellulose as shown in Figure 4. The nanocellulose can be obtained through two approaches: top-down by the disintegration of plant fiber or bottom-up by biosynthesis [46]. For bottomup biosynthesis approach, fermentation of low-molecular-weight sugars occurred by using bacteria from Acetobacter species. Meanwhile, for the top-down approach, the production of nanocrystalline cellulose is chemically induced via removing amorphous region. The chemical or mechanical treatments or a combination of both treatments involves enzymatic treatment, grinding, high-pressurized homogenization, acid hydrolysis, TEMPO-mediated oxidation, microfluidization, cryocrushing, and high-intensity ultrasonification. Table 3 shows the hydrolysis approaches from

various sources of agro-waste and forest by-product for NCC isolation.

Schematic representation of lignocellulosic agro-waste and by-product of forest classification. Adapted from

Source Process References Acacia mangium H2SO4 hydrolysis [56] Algae H2SO4 hydrolysis [57] Areca nut husk fiber HCl hydrolysis [14] Bacterial cellulose H2SO4 hydrolysis [58] Bamboo H2SO4 hydrolysis [59] Bamboo (Pseudosasa amabilis) H2SO4 hydrolysis [60] Banana fiber H2C2O4 hydrolysis [31] Banana pseudo-stem TEMPO-mediated oxidation, formic acid hydrolysis [61] Cassava bagasse H2SO4 hydrolysis [62]

Figure 4.

Ref. [47].

95

#### Table 2.

Functions and properties of cellulose, hemicellulose, and lignin. Adapted from Refs. [6, 7, 27].

agro-waste fibers are different depending on the type of fiber as summarized in Table 1. Besides that, it can be concluded in Table 1 that the highest cellulose contents are pineapple leaf fibers (81.27%), followed by kenaf core powder (80.26%). Besides that, from Table 1 also we can summarize that the chemical composition of natural fibers is 30–80% cellulose, 7–40% hemicellulose, and 3–33% lignin. Cellulose, hemicellulose, and lignin have their own properties and functionality. Table 2 shows the functional properties of the cellulose, hemicellulose, and lignin. The physical, thermal, and mechanical properties of the natural fibers are diverse between each other as they are mostly depending on cellulose crystallinity. Intra- and intermolecular hydrogen bonding among the cellulose chains affects the packing compactness of cellulose crystallinity. Table 1 shows the chemical composition of natural fibers and their crystallinity. From the abovementioned lignocellulosic, particularly, the hemicellulose and cellulose have promising features such as existing refining agro-forest or agro-waste factories. For centuries, cellulose has been utilized in the form of non-wood plant fibers and wood as building materials, clothing, textile, and paper.

#### 3. Nanocrystalline cellulose

Nanocrystalline cellulose (NCC) has several notable optical, chemical, and electrical properties due to their needlelike shape, high surface area, high aspect ratio

### Production, Processes and Modification of Nanocrystalline Cellulose from Agro-Waste: A Review DOI: http://dx.doi.org/10.5772/intechopen.87001

(length/diameter), high crystallinity, nanoscale size, high strength and stiffness, low density, and highly negative charge which lead to unique behavior in solutions. The high chemical reactivity of the surface makes NCC customizable for various applications, besides their heat stability which allows high-temperature applications. Moreover, they also have huge surface OH groups which provide active sites for hydrogen bonding through the interlocking with nonpolar matrix [4, 7, 10, 45, 46]. Nanocrystalline cellulose can be isolated from cellulose as shown in Figure 4. The nanocellulose can be obtained through two approaches: top-down by the disintegration of plant fiber or bottom-up by biosynthesis [46]. For bottomup biosynthesis approach, fermentation of low-molecular-weight sugars occurred by using bacteria from Acetobacter species. Meanwhile, for the top-down approach, the production of nanocrystalline cellulose is chemically induced via removing amorphous region. The chemical or mechanical treatments or a combination of both treatments involves enzymatic treatment, grinding, high-pressurized homogenization, acid hydrolysis, TEMPO-mediated oxidation, microfluidization, cryocrushing, and high-intensity ultrasonification. Table 3 shows the hydrolysis approaches from various sources of agro-waste and forest by-product for NCC isolation.

#### Figure 4.

agro-waste fibers are different depending on the type of fiber as summarized in Table 1. Besides that, it can be concluded in Table 1 that the highest cellulose contents are pineapple leaf fibers (81.27%), followed by kenaf core powder (80.26%). Besides that, from Table 1 also we can summarize that the chemical composition of natural fibers is 30–80% cellulose, 7–40% hemicellulose, and 3–33% lignin. Cellulose, hemicellulose, and lignin have their own properties and functionality. Table 2 shows the functional properties of the cellulose, hemicellulose, and lignin. The physical, thermal, and mechanical properties of the natural fibers are diverse between each other as they are mostly depending on cellulose crystallinity. Intra- and intermolecular hydrogen bonding among the cellulose chains affects the packing compactness of cellulose crystallinity. Table 1 shows the chemical composition of natural fibers and their crystallinity. From the abovementioned lignocellulosic, particularly, the hemicellulose and cellulose have promising features such as existing refining agro-forest or agro-waste factories. For centuries, cellulose has been utilized in the form of non-wood plant fibers and wood as building materials,

Functions and properties of cellulose, hemicellulose, and lignin. Adapted from Refs. [6, 7, 27].

Cellulose Hemicellulose Lignin

bonds

per polymer

• Responsible for the moisture absorption, biodegradation • Microfibrils are crosslinked together by hemicellulose homopolymers

• Thermal stability occurred from 220 to

315°C

• Hemicellulose is a cell wall polysaccharide that has the capacity to bind strongly to cellulose microfibrils by hydrogen • Lignin is a crosslinked polymer with molecular masses in excess of 10,000 u

• Responsible for UV degradation • Lignin assists and strengthens the attachment of hemicelluloses to microfibrils • Lignin plays a crucial part in conducting water in plant stems

• Thermal stability occurred from 165 to 900°C

• Hemicelluloses consist of short chains—500– 3000 glucose molecules

Structure • Cellulose is assembled

Nanocrystalline Materials

Function • Connecting cells to form tissue • Provide structural support • Provides a strong resistance to stress • Prevents the cell from bursting in hypotonic

solution

400°C)

(occurred from 315 to

Properties • Thermal stability

Table 2.

94

together with pectin fibers, which function to bind the cellulose together to produce tighter cell walls in natural fibers, accounting for their strength providing resistance to lysing in the presence of water • Hemicelluloses consist of long chain—7000– 15,000 glucose molecules per polymer

Nanocrystalline cellulose (NCC) has several notable optical, chemical, and electrical properties due to their needlelike shape, high surface area, high aspect ratio

clothing, textile, and paper.

3. Nanocrystalline cellulose

Schematic representation of lignocellulosic agro-waste and by-product of forest classification. Adapted from Ref. [47].



4. Processes of nanocrystalline cellulose

DOI: http://dx.doi.org/10.5772/intechopen.87001

Available process of extraction approaches from different sources for NCC isolation.

Table 3.

Figure 5.

97

Recently, researchers are exploring the potential utilization of agriculture or forest wastes as NCCs'sources. As a consequence, the various local sources are used to investigate the potential of NCC in certain technologies. The isolation of NCC needs intensive hydrolysis chemical treatment. However, according to the degree of processing and raw material, physical, chemical, enzymatic, and ionic pretreatments are performed before nanocrystalline cellulose synthesis. Figure 5 shows the sources, pretreatments, synthesis, and application of nanocrystalline cellulose. It is good to know that appropriate pretreatments of cellulosic fibers promote the accessibility of hydroxyl group, alter crystallinity, increase the inner surface, and break cellulose hydrogen bonds and hence improved the reactivity of the fibers [6, 7, 10]. Several approaches to diminish cellulosic fibers into nanofibers can be divided into several techniques such as acid hydrolysis, alkali treatment, mechanical treatments, and combination of mechanical and chemical treatments. Common methods for isolate NCC are hydrolysis methods which are a chemical method. Figure 6 shows

Sources, pretreatments, synthesis, and application of nanocrystalline cellulose. Adapted from Refs. [6, 7, 10].

Source Process References Sugarcane bagasse H2SO4 hydrolysis [37] Sago seed shells H2SO4 hydrolysis [93] Tunicate H2SO4 hydrolysis [94] Water hyacinth fiber HCl hydrolysis [48] Wood pulp TEMPO oxidation followed by HCl hydrolysis [95] Wheat straw H2SO4 hydrolysis [96] Valonia ventricosa HCl hydrolysis [97]

Production, Processes and Modification of Nanocrystalline Cellulose from Agro-Waste: A Review

Production, Processes and Modification of Nanocrystalline Cellulose from Agro-Waste: A Review DOI: http://dx.doi.org/10.5772/intechopen.87001


Table 3.

Source Process References Coconut husk H2SO4 hydrolysis [63] Colored cotton H2SO4 hydrolysis [64] Corncob H2SO4 hydrolysis [13] Cotton (cotton wool) H2SO4 hydrolysis [65] Cotton linters HCl hydrolysis [66] Cotton Whatman filter paper H2SO4 hydrolysis [67]

Cotton stalk TEMPO-mediated oxidation and H2SO4 hydrolysis [69] Cotton fiber H2SO4 hydrolysis [70] Curaua fiber H2SO4, H2SO4/HCl, HCl hydrolysis [35] Eucalyptus kraft pulp H2SO4 hydrolysis [71] Grass fibers H2SO4 hydrolysis [72] Grass fibers (Imperata brasiliensis) H2SO4 hydrolysis [73] Groundnut shells H2SO4 hydrolysis [74] Hibiscus sabdariffa fibers Steam explosion H2SO4 hydrolysis [75]

Industrial bioresidue H2SO4 hydrolysis [77] Industrial bioresidue (sludge) H2SO4 hydrolysis [78] Kraft pulp H2SO4 hydrolysis [79] Kenaf core wood H2SO4 hydrolysis [40] MCC H2SO4 hydrolysis [55] Mengkuang leaves H2SO4 hydrolysis [44] Mulberry H2SO4 hydrolysis [80] Oil palm trunk H2SO4 hydrolysis [81]

Phormium tenax (harakeke) fiber H2SO4 hydrolysis [83] Potato peel waste H2SO4 hydrolysis [84] Flax fiber H2SO4 hydrolysis [83] Ramie KOH hydrolysis [85] Ramie H2SO4 hydrolysis [86] Ramie H2SO4 hydrolysis [87] Rice husk H2SO4 hydrolysis [63] Rice straw H2SO4 hydrolysis [88] Sesame husk H2SO4 hydrolysis [89] Sisal fiber H2SO4 hydrolysis [90] Soy hulls H2SO4 hydrolysis [91] Sugar palm fiber H2SO4 hydrolysis [6] Sugar palm frond H2SO4 hydrolysis [92]

Humulus japonicus stem H2SO4 hydrolysis with high-temperature pretreatment

H2SO4 hydrolysis [68]

H2SO4 hydrolysis [82]

[76]

Cotton (Gossypium hirsutum)

Nanocrystalline Materials

Oil palm empty fruit bunch

(OPEFB)

96

linters

Available process of extraction approaches from different sources for NCC isolation.
