*2.2.2 Fermentation*

Fermentation is a biological process that is commonly facilitated by secretion of enzymes sourced from microorganisms which converts simple sugars to low molecular weight structures such as alcohols and acids. The fermentation of two most common sugars follow the two reactions below:

$$\text{Glucose}: \text{C}\_6\text{H}1\_2\text{O}\_6 \to 2\text{C}\_2\text{H}\_6\text{O} + 2\text{CO}\_2 \tag{1}$$

$$\text{Xylose}: \text{\textbullet C}\_{\text{\textbullet}} \text{H}\_{\text{uo}} \text{O}\_{\text{\textbullet}} \to \text{\textbullet C}\_{\text{z}} \text{H}\_{6} \text{O} + \text{\textbullet CO}\_{z} \tag{2}$$

**13**

**Table 2.**

**Figure 8.**

*Anaerobic digestion process [46].*

presented in **Table 2**.

**SHF** *= Separate hydrolysis and fermentation.* **SSF** *= Simultaneous saccharification and fermentation.* **SSCF** *= Simultaneous saccharification and co-fermentation.*

**CBP** *= Consolidated Bioprocessing.*

*Processes in bio-ethanol production [47].*

*Biomass Conversion Technologies for Bioenergy Generation: An Introduction*

**Process Substrate Pre-treatment Ethanol** 

SHF *Parthenium hysterophorus* L. Acids/alkali 13.6 —

SSF *Miscanthus sacchariflorus* CHEMET with NaOH 69.2 1.24

SSCF Wood chips Steam explosion 32.9 0.34

CBP Corn stover Acid hydrolysis — 0.27

Reed phosphoric

Arundo donax Steam explosion 20.6 0.21 Wheat straw Steam explosion — 0.313

acid-acetone

*Liriodendron tulipifera* Acid-free organosolv 29.9 0.42 Corn stover Steam explosion 25.7 0.36 Miscanthus giganteus Dilute oxalic acid 12.1 0.13 Industrial hemp Steam explosion 21.3 0.30

Wheat straw Steam explosion — 0.7

Reed Liquid hot water 39.4 0.66

**Conc., g/L**

55.5 0.57

**Ethanol Pro., g/L/h**

and fermentation process are carried out either concurrently in the same reactor or separately [47]. The different processes involved for alcohols production are

Conversion of biomass feedstocks through fermentation process is a vital issue because it allows for the production of wide range of substances under mild

*DOI: http://dx.doi.org/10.5772/intechopen.93669*

During fermentation, biomass could be converted into alcohols through biochemical pathways. These pathways involved several schemes in which hydrolysis


#### **Table 1.**

*The biomass yield and methane potential of some selected lignocellulosic biomass [45].*

#### *Biomass Conversion Technologies for Bioenergy Generation: An Introduction DOI: http://dx.doi.org/10.5772/intechopen.93669*

#### **Figure 8.**

*Biotechnological Applications of Biomass*

feedstocks were presented in **Table 1** [45].

biogas has a heating value of about 22,350 KJ/m3

most common sugars follow the two reactions below:

(CH4:CO2:inerts) of 60: 35: 5 (**Figure 8**) [46].

*2.2.2 Fermentation*

The digestion of lignocellulosic biomass anaerobically produces energy rich methane (CH4). The CH4 yield per unit area is usually employed for the determination of energy output of an individual feedstock which significantly varies between species and as well with maturity, location and inputs (such as fertilizer, water etc.) within the same variety (Yang et al., 2013). The Biochemical methane potential (BMP) test is commonly used to evaluate the anaerobic digestibility of a biomass substrate. The biomass yield and CH4 production potentials of some selected

Anaerobic digestion is a process used to produce biogas through biological treatment of biomass. It is performed at temperature ranges between 30 and 35°C, or 50 and 55°C using two stages. The first stage is the breaking down of the complex organics in the biomass by acid-forming bacteria into simpler compounds such as acetic and propionic acids along with volatiles. The second stage is conversion of such acids into CO2 and CH4 commonly called biogas through the use of methane producing bacteria. Usually, both stages of biogas production are performed in a single tank. The produced biogas contains about 60% CH4, 35% CO2, and a mixture of other gases such as H2, NH3, CO, and H2S which account for about 5%. The

Fermentation is a biological process that is commonly facilitated by secretion of enzymes sourced from microorganisms which converts simple sugars to low molecular weight structures such as alcohols and acids. The fermentation of two

During fermentation, biomass could be converted into alcohols through biochemical pathways. These pathways involved several schemes in which hydrolysis

**Biomass Biomass yield (ton wet weight/ha) CH4 potential (Nm3**

Sugar beet 40–70 387–408 Fodder beet 80–120 398–424 Maize 40–60 291–338 Wheat 30–50 351–378 Triticale 28–33 319–335 Sorghum 40–80 286–319 Grass 22–31 286–324 Red clover 17–25 297–347 Sunflower 31–42 231–297 Wheat grain 06–10 371–398

*The biomass yield and methane potential of some selected lignocellulosic biomass [45].*

Glucose : C H1 O 2C H O 2CO 6 26 26 2 → + (1)

Xylose : 3C H O 5C H O 5CO 5 10 5 2 6 → + <sup>2</sup> (2)

for a mixture that contains a ratio

 **CH4/tonVS)**

**12**

**Table 1.**

*Anaerobic digestion process [46].*


**SHF** *= Separate hydrolysis and fermentation.*

**SSF** *= Simultaneous saccharification and fermentation.*

**SSCF** *= Simultaneous saccharification and co-fermentation.*

**CBP** *= Consolidated Bioprocessing.*

#### **Table 2.**

*Processes in bio-ethanol production [47].*

and fermentation process are carried out either concurrently in the same reactor or separately [47]. The different processes involved for alcohols production are presented in **Table 2**.

Conversion of biomass feedstocks through fermentation process is a vital issue because it allows for the production of wide range of substances under mild conditions. The extent of fermentation on organic substances largely depends on composition and structure of the biomass feedstock. Only feedstocks that are not competing with the food items in terms of demand should be selected for biofuel production. Consequently, residues and waste materials from agriculture and forestry were considered as the most interesting sources of biomass.

High hydrolysis ratio is also an important requirement for the effective utilization of monosugars present in lignocellulosic structures. From biochemical perspective, organic substances present in the hydrolyzed solution can be categorized into several groups such as simple and complex carbohydrates, lipids, proteins, and heteropolymers. The potentials for biogas and biohydrogen generation from lignocellulosic biomass is huge due to utilization of different microorganisms in the conversion of cellulose and hemicellulosic fractions of the agricultural and forestry residues [47]. However, a major setback is usually encountered during biofuels production which is the conversion ratio of the polymeric substances into fermentable sugars like hexoses and pentoses due to production of inhibitors along with the desired products. To minimize such inhibitors and maximize hexoses and pentoses production, microbial metabolism in the degradation and saccharification of the biomass cell wall were considered [48, 49].
