**2.2. Physical and chemical compositions of sugarcane**

Physically, sugarcane is constituted by four fractions, whose relative magnitude depends on the agro industrial process: fiber, non-soluble solids, soluble solids and water. The fiber is composed of the whole organic solid fraction, non-soluble in water, originally found in the cane's stalk, and characterized by its marked heterogeneity from the morphological point of view. The non-soluble solids, or the fraction that cannot be dissolved in water, are constitut‐ ed mainly by inorganic substances (rocks, soil and extraneous materials) and it is greatly in‐ fluenced by the conditions of the agricultural cane processing and harvesting type. Soluble solids, fraction that can be dissolved in water, are composed basically of sucrose as well as other small chemical components such as waxes [17].

**Component (%) Reference**

[23]2 Brazil

**Component (%) Reference**

[22]2\* Brazil

[16]1\* Brazil

[24]3\* Brazil

Cellulose 41.1 38.8 45.0 45.5 43.0 43.1 39.6

Hemicellulose 22.7 26.0 25.8 27.0 24.0 31.1 29.7

Lignin 31.4 32.4# 19.1 21.1 20.0 11.4 24.7

Ash 2.4 2.8 1.0 2.2 - 5.5 4.1

Extractives 6.8 - 9.1 4.6 - - 14.3

Others - - - - - 8.5 -

Extracting solvents: 1dichloromethane, ethanol: toluene (1:2), ethanol, hot water; 2none; 3water and ethanol; 4ethanol;

**Table 1.** Chemical composition (% w/w, dry basis) of Brazilian and worldwide sugarcane bagasse samples reported in

Cellulose 36.1 34.4 36.1 33.6 33.3 45.0

Hemicellulose 28.3 18.4 26.9 28.9 27.4 25.0

Lignin 26.2 40.7 26.2 31.8# 26.1 18.0

Ash 2.1 11.7 2.1 5.7 2.6 -

Extractives 5.3 11.5 5.3 - - -

Others - - - - 10.6 -

Extracting solvents: 1ethanol; 2dichloromethane, ethanol: toluene (1:2), ethanol, hot water; 3water; 4none; 5none;

**Table 2.** Chemical composition (% w/w, dry basis) of Brazilian and Indian sugarcane straw samples reported in the

[29]3\* Brazil

[23]4 Brazil [30]5 Brazil [15]6 India

[25]4\* Brazil

[26]5\* India

Bioconversion of Hemicellulose from Sugarcane Biomass Into Sustainable Products

[27]6 Cube

http://dx.doi.org/10.5772/53832

[28]7\* USA

19

[22]1\* Brazil

\*Extractives-free basis; #Lignin and others

\*Extractives-free basis; #Lignin and others

5none; 6none; 7not described

the literature

6none

literature

Bagasse and straw (trash), which are the focus of second generation ethanol production, are lignocellulosic materials chemically composed by cellulose, hemicelluloses and lignin. According to some works in the literature, sugarcane bagasse of the Brazilian territory is quantitatively composed by 38.8-45.5% cellulose, 22.7-27.0% hemicellulose and 19.1-32.4% lignin (Table 1). Non-structural components of biomass namely ashes (1.0-2.8%) and ex‐ tractives (4.6-9.1%) are the other substances that are part of the chemical compositional of bagasse. The ash content of bagasse is lower than the others crop residues, like rice straw and wheat straw (with approximately 17.5 and 11.0% of this compound, respec‐ tively) and the bagasse is considered a rich solar energy reservoir due to its high yields and annual regeneration capacity (about 80 t/ha) in comparison with others agricultural residues, like wheat, grasses and tree (1, 2 and 20 t/ha, respectively) [3]. The bagasse al‐ so can be used as a raw material for cultivation of microorganisms for the production of value-added products such as xylitol and ethanol. Due to these and others advantages the bagasse is not only a sub-product of sugar industry, but it is a co-product with high added-value [3].

As can be seen in the Table 1, the chemical compositions of sugarcane bagasse samples var‐ ied widely. In fact, it is impossible to compare the composition of samples from different ori‐ gins, performed by different laboratories and that do not use the same methods. Furthermore, factors like plant genetics, growth environment and processing conditions also influence the compositional analysis [18].

The large variation in the values of chemical components also is observed for the sugarcane straw, that it is composed approximately by 33.3-36.1% cellulose, 18.4-28.9% hemicellulose, 26.1-40.7% lignin (Table 2). Ashes (2.1-11.7%) and extractives (5.3-11.5%) are also present on the sugarcane straw composition.

When mechanically harvested, and depending on the harvesting technology applied, the range of straw that is collected and transported to the mill together with the stalks is 24% to 95% of the total trash available [19]. The amount of trash from sugarcane harvesting de‐ pends on several factors such as: harvesting system, topping, height, cane variety, age of crop (stage of cut), climate, soil and others. The average stalks yield per hectare was estimat‐ ed to 83.23 tons/ha over an average of 5 seasons (cuts), resulting average availability of trash of 11.98 tons/ha (dry basis) [20].


\*Extractives-free basis; #Lignin and others

**2.2. Physical and chemical compositions of sugarcane**

other small chemical components such as waxes [17].

added-value [3].

influence the compositional analysis [18].

the sugarcane straw composition.

of 11.98 tons/ha (dry basis) [20].

Physically, sugarcane is constituted by four fractions, whose relative magnitude depends on the agro industrial process: fiber, non-soluble solids, soluble solids and water. The fiber is composed of the whole organic solid fraction, non-soluble in water, originally found in the cane's stalk, and characterized by its marked heterogeneity from the morphological point of view. The non-soluble solids, or the fraction that cannot be dissolved in water, are constitut‐ ed mainly by inorganic substances (rocks, soil and extraneous materials) and it is greatly in‐ fluenced by the conditions of the agricultural cane processing and harvesting type. Soluble solids, fraction that can be dissolved in water, are composed basically of sucrose as well as

18 Sustainable Degradation of Lignocellulosic Biomass - Techniques, Applications and Commercialization

Bagasse and straw (trash), which are the focus of second generation ethanol production, are lignocellulosic materials chemically composed by cellulose, hemicelluloses and lignin. According to some works in the literature, sugarcane bagasse of the Brazilian territory is quantitatively composed by 38.8-45.5% cellulose, 22.7-27.0% hemicellulose and 19.1-32.4% lignin (Table 1). Non-structural components of biomass namely ashes (1.0-2.8%) and ex‐ tractives (4.6-9.1%) are the other substances that are part of the chemical compositional of bagasse. The ash content of bagasse is lower than the others crop residues, like rice straw and wheat straw (with approximately 17.5 and 11.0% of this compound, respec‐ tively) and the bagasse is considered a rich solar energy reservoir due to its high yields and annual regeneration capacity (about 80 t/ha) in comparison with others agricultural residues, like wheat, grasses and tree (1, 2 and 20 t/ha, respectively) [3]. The bagasse al‐ so can be used as a raw material for cultivation of microorganisms for the production of value-added products such as xylitol and ethanol. Due to these and others advantages the bagasse is not only a sub-product of sugar industry, but it is a co-product with high

As can be seen in the Table 1, the chemical compositions of sugarcane bagasse samples var‐ ied widely. In fact, it is impossible to compare the composition of samples from different ori‐ gins, performed by different laboratories and that do not use the same methods. Furthermore, factors like plant genetics, growth environment and processing conditions also

The large variation in the values of chemical components also is observed for the sugarcane straw, that it is composed approximately by 33.3-36.1% cellulose, 18.4-28.9% hemicellulose, 26.1-40.7% lignin (Table 2). Ashes (2.1-11.7%) and extractives (5.3-11.5%) are also present on

When mechanically harvested, and depending on the harvesting technology applied, the range of straw that is collected and transported to the mill together with the stalks is 24% to 95% of the total trash available [19]. The amount of trash from sugarcane harvesting de‐ pends on several factors such as: harvesting system, topping, height, cane variety, age of crop (stage of cut), climate, soil and others. The average stalks yield per hectare was estimat‐ ed to 83.23 tons/ha over an average of 5 seasons (cuts), resulting average availability of trash Extracting solvents: 1dichloromethane, ethanol: toluene (1:2), ethanol, hot water; 2none; 3water and ethanol; 4ethanol; 5none; 6none; 7not described

**Table 1.** Chemical composition (% w/w, dry basis) of Brazilian and worldwide sugarcane bagasse samples reported in the literature


\*Extractives-free basis; #Lignin and others

Extracting solvents: 1ethanol; 2dichloromethane, ethanol: toluene (1:2), ethanol, hot water; 3water; 4none; 5none; 6none

**Table 2.** Chemical composition (% w/w, dry basis) of Brazilian and Indian sugarcane straw samples reported in the literature

From the technological viewpoint, sugars that are present in the cellulosic (glucose) and hemicellulosic (xylose, arabinose, glucose, mannose and galactose) fractions representing the substrates that can be used in fermentative process for production of some sustaina‐ ble products such as xylitol, butanediol, single cell protein, ethanol and xylitol. However, the close association between the three major fractions (cellulose, hemicellulose and lig‐ nin) of the lignocelulosic materials, like bagasse and straw, causes difficulties for the re‐ covery of these substrates in the form of monomers with high purity. Therefore, to use these three constituents it is required a selective separation of each fraction by pretreat‐ ment techniques, delignification and hydrolysis, involving the breakdown of hemicellu‐ lose-lignin-cellulose complex [21].

*Process Advantages Disadvantages*








Milling

Pyrolysis

Steam Ex‐ plosion or hydrother‐ mal

Ammonia Fiber Ex‐ plosion (AFEX)

CO2 Explo‐ sion

Acid Pre‐ treatment

Alkaline Pretreat‐ ment

ball milling provides the reduction of parti‐ cles size and breaks down the structure of lignocellulosic materials

treatment with temper‐ atures higher than 300ºC

structure compounds breakdown by heat ad‐ dition in form of steam and forces by the mois‐ ture expansion

expose the lignocellulo‐ sic material with am‐ monia to high temperature and pres‐ sure followed by a fast pressure release

formation of carbonic acid and increase the hydrolysis rate of sub‐ strates

dilute-acid hydrolysis of the lignocellulosic ma‐ terial

delignification process employing bases such as sodium hydroxide, calcium hydroxide (lime), etc

Physical Pretreatments








Chemical Pretreatments

X

Physic-Chemical Pretreatments

*Solubilized Fraction*

Bioconversion of Hemicellulose from Sugarcane Biomass Into Sustainable Products

*Hemicel. Cel. Lignin*

Alteration in structure [23]

X [40]

X

X

X X

X X

*References*

21

http://dx.doi.org/10.5772/53832

[39]

[41] [42]

[38] [40]

[40] [43]

[10] [24] [35]

[40] [44]
