Preface

The rapid increase in global energy demand has resulted in shortages of fossil fuel supply. Biogas is the most profitable bioenergy generated from first-, second-, and third-generation waste biomass, is the best suitable alternative to fossil fuel, and is cost effective. Biogas consists of approximately 60–65% methane, 25–30% carbon dioxide, and a small amount of toxic gases, etc. Organic waste management via anaerobic digestion is the most commonly preferred technique. During this process the anaerobic microbes play a vital role in conversion of organic waste into biogas. To enhance biogas production, pretreatment prior to anaerobic digestion results in achieving a positive energy yield. Developing a proper system to recover biogas from organic waste will reduce global warming issues. This book intends to provide a comparative overview of a recent update in biogas production, processing, and its application in various sectors. In addition, this book contains several scientific discussions regarding microbes involved in biogas production, processing, and recent technologies for sustainable development. The book provides in-depth information about anaerobic digestion to researchers and graduate students. The editor sincerely thanks all the contributors, whose efforts have brought this book to fruition.

**II**

**Section 4**

**Section 5**

Biogas for Clean Energy

*by Mario Toledo Torres*

*by Adeola Suhud Shote*

Biogas Processing

*and Norwahyu Jusoh*

**Section 6**

*by Demsew Mitiku Teferra and Wondwosen Wubu*

Biofuel: An Environmental Friendly Fuel

Biofuel Development in Sub-Saharan Africa

Non-Catalytic Reforming of Biogas in Porous Media Combustion

Biogas **147**

**Chapter 7 149**

**Chapter 8 169**

Application of Anaerobic Digestion **183**

**Chapter 9 185**

**Chapter 10 199**

Case Study **219**

**Chapter 11 221**

Experimental Study of CO2 Plasticization in Polysulfone Membrane for

*by Olatunde Samuel Dahunsi, Ayoola Shoyombo and Omololu Fagbiele*

*by Serene Sow Mun Lock, Kok Keong Lau, Azmi Mohd Shariff, Yin Fong Yeong* 

**Dr. J. Rajesh Banu** Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India

**1**

Section 1

Introduction

Section 1 Introduction

**3**

shown below:

**Chapter 1**

**1. Introduction**

Introductory Chapter: An

encounter the energy demand and global warming impacts.

other waste processing technologies.

anaerobic degradation of organic waste.

According to the International Energy Agency Report 2018, the global energy demands (GED) elevated 2.1% from the previous year. However, 70% of GED was met through oil, coal and fossil fuel. Among these, fossil fuel accounts for 81% of total energy demand (TED). The percentage of fossil fuel remains unchanged for the past three decades. Exploitation of fossil fuel extended the emission of carbon dioxide (CO2) to 32.5 GT (gigatonnes) in the year 2017. Surplus emission of greenhouse gases (GHG) into the atmosphere is the major contributor for global warming and climate change. On considering, the profile of GHG emission researchers comes out with innovative ideas to minimize the emission. Nowadays, researchers and policymakers are working together to recognize alternative energy source to

Anaerobic digestion (AD) process is the cost-effective and emerging technology to derive biogas from various liquids and solid wastes. AD process is more suitable for valorization of high-strength organic waste under both mesophilic (30–40°C) and thermophilic (50–60°C) conditions. AD process is otherwise termed as biomethanation or biochemical degradation. AD process is a more environmentalfriendly, energy-yielding and more efficient bioenergy production method than

AD process dominant by anaerobic microbes, which plays major role in conversion of organic rich waste biomass into two valuable products such as methane and nutrient rich digested/effluent. Anaerobic breakdown of complex organic waste biomass follows four major steps, and these are (i) hydrolysis, (ii) acidogenesis, (iii) acetogenesis and (iv) methanogenesis. **Figure 1** represents the pathway of

Among them, hydrolysis is the rate-limiting and first step of AD process. During hydrolysis, complex organics (C6H10O4) such as protein, carbohydrate and fat are converted into simple digestible amino acids, monosaccharides and fatty acids. Eq. (1) shows that the reaction occurs during hydrolysis phase; enzymes convert the complex organic substrate into simple monomers (C6H12O6) and hydrogen (H2) as

C6H10O4 + 2H2O → C6H12O6 + H2 (1)

Hydrolysis is a very slow process when compared with other steps involved in AD process. Inadequate hydrolysis of organic waste affects the efficiency of AD. In order to increase the rate of hydrolysis, many researchers have adopted various pretreatment methods. Banu and Kavitha [1] have reviewed in detail regarding various

pretreatment methods and their effects on anaerobic digestion.

Overview of Biogas

*J. Rajesh Banu and R. Yukesh Kannah*

### **Chapter 1**

## Introductory Chapter: An Overview of Biogas

*J. Rajesh Banu and R. Yukesh Kannah*

### **1. Introduction**

According to the International Energy Agency Report 2018, the global energy demands (GED) elevated 2.1% from the previous year. However, 70% of GED was met through oil, coal and fossil fuel. Among these, fossil fuel accounts for 81% of total energy demand (TED). The percentage of fossil fuel remains unchanged for the past three decades. Exploitation of fossil fuel extended the emission of carbon dioxide (CO2) to 32.5 GT (gigatonnes) in the year 2017. Surplus emission of greenhouse gases (GHG) into the atmosphere is the major contributor for global warming and climate change. On considering, the profile of GHG emission researchers comes out with innovative ideas to minimize the emission. Nowadays, researchers and policymakers are working together to recognize alternative energy source to encounter the energy demand and global warming impacts.

Anaerobic digestion (AD) process is the cost-effective and emerging technology to derive biogas from various liquids and solid wastes. AD process is more suitable for valorization of high-strength organic waste under both mesophilic (30–40°C) and thermophilic (50–60°C) conditions. AD process is otherwise termed as biomethanation or biochemical degradation. AD process is a more environmentalfriendly, energy-yielding and more efficient bioenergy production method than other waste processing technologies.

AD process dominant by anaerobic microbes, which plays major role in conversion of organic rich waste biomass into two valuable products such as methane and nutrient rich digested/effluent. Anaerobic breakdown of complex organic waste biomass follows four major steps, and these are (i) hydrolysis, (ii) acidogenesis, (iii) acetogenesis and (iv) methanogenesis. **Figure 1** represents the pathway of anaerobic degradation of organic waste.

Among them, hydrolysis is the rate-limiting and first step of AD process. During hydrolysis, complex organics (C6H10O4) such as protein, carbohydrate and fat are converted into simple digestible amino acids, monosaccharides and fatty acids. Eq. (1) shows that the reaction occurs during hydrolysis phase; enzymes convert the complex organic substrate into simple monomers (C6H12O6) and hydrogen (H2) as shown below:

$$\rm{C}\_{6}H\_{10}O\_{4} + 2H\_{2}O \rightarrow \rm{C}\_{6}H\_{12}O\_{6} + H\_{2} \tag{1}$$

Hydrolysis is a very slow process when compared with other steps involved in AD process. Inadequate hydrolysis of organic waste affects the efficiency of AD. In order to increase the rate of hydrolysis, many researchers have adopted various pretreatment methods. Banu and Kavitha [1] have reviewed in detail regarding various pretreatment methods and their effects on anaerobic digestion.

Pretreatment enhances the digestibility of organic substrate, and it is broadly classified into five major groups. They are physical, chemical, biological, mechanical and combinative pretreatments. **Figure 2** shows pretreatment methods and their classification. Physical pretreatment is further classified into two: thermal [2] microwave [3] and freezing and thaw [4] pretreatments. Chemical pretreatment is further classified into two: alkaline [5] and acidic [6] pretreatments. Biological pretreatment is further classified into two: enzyme [7] and fungal [8] pretreatments. Mechanical pretreatment is further classified into two: high-pressure homogenizer [9] and ultrasonic [10] pretreatments. Combinative pretreatment such as thermo-chemo-sonic [11], thermo-chemo-disperser [12], thermo-chemoozone [13] and hydrothermal [14] pretreatment, etc. Many researchers have experimentally proven the positive effect of pretreatment on hydrolysis and subsequent biogas production [15].

Acidogenesis is the second step involved in AD process; in this step, acidogenic microbes are responsible for conversion of hydrolyzed organics into ethanol (C2H5OH), acetate (CH3COO¯), hydrogen (H2), carbon dioxide (CO2) and other acids (propionic, formic, lactic, butyric, succinic acids). In some cases, amino acids cause formation of ammonia. Eqs. (2)–(4) show that the reaction occurs during acidogenesis phase as shown below:

$$\text{C}\_6\text{H}\_{12}\text{O}\_6 \leftrightarrow \text{ 2CH}\_3\text{CH}\_2\text{OH} + \text{2CO}\_2\tag{2}$$

$$\text{C}\_6\text{H}\_{12}\text{O}\_6 + 2\text{H}\_2 \leftrightarrow 2\text{CH}\_3\text{CH}\_2\text{COOH} + 2\text{H}\_2\text{O} \tag{3}$$

$$\text{C}\_6\text{H}\_{12}\text{O}\_6 \rightarrow \text{ 3CH}\_3\text{CH}\_2\text{OH} \tag{4}$$

**5**

**Figure 2.**

*Pretreatment methods and their classification.*

*Introductory Chapter: An Overview of Biogas DOI: http://dx.doi.org/10.5772/intechopen.82198*

Acetogenesis is the third step involved in AD process. In this step, acetogenic microbes are responsible for conversion of long-chain fatty acid, volatile fatty acid and alcohols into acetic acid (CH3COOH), hydrogen (H2) and carbon dioxide *Anaerobic Digestion*

**Figure 1.**

Pretreatment enhances the digestibility of organic substrate, and it is broadly classified into five major groups. They are physical, chemical, biological, mechanical and combinative pretreatments. **Figure 2** shows pretreatment methods and their classification. Physical pretreatment is further classified into two: thermal [2] microwave [3] and freezing and thaw [4] pretreatments. Chemical pretreatment is further classified into two: alkaline [5] and acidic [6] pretreatments. Biological pretreatment is further classified into two: enzyme [7] and fungal [8] pretreatments. Mechanical pretreatment is further classified into two: high-pressure homogenizer [9] and ultrasonic [10] pretreatments. Combinative pretreatment such as thermo-chemo-sonic [11], thermo-chemo-disperser [12], thermo-chemoozone [13] and hydrothermal [14] pretreatment, etc. Many researchers have experimentally proven the positive effect of pretreatment on hydrolysis and subsequent

Acidogenesis is the second step involved in AD process; in this step, acidogenic

C6H12O6 ↔ 2CH3CH2OH + 2CO2 (2)

C6H12O6 + 2H2 ↔ 2CH3CH2COOH + 2H2O (3)

C6H12O6 → 3CH3CH2OH (4)

Acetogenesis is the third step involved in AD process. In this step, acetogenic microbes are responsible for conversion of long-chain fatty acid, volatile fatty acid and alcohols into acetic acid (CH3COOH), hydrogen (H2) and carbon dioxide

microbes are responsible for conversion of hydrolyzed organics into ethanol (C2H5OH), acetate (CH3COO¯), hydrogen (H2), carbon dioxide (CO2) and other acids (propionic, formic, lactic, butyric, succinic acids). In some cases, amino acids cause formation of ammonia. Eqs. (2)–(4) show that the reaction occurs during

**4**

biogas production [15].

acidogenesis phase as shown below:

*Pathway of anaerobic degradation of organic waste.*

(CO2). Eqs. (5)–(7) show that the reaction occurs during acetogenesis phase as shown below:

$$\text{CH}\_3\text{CH}\_2\text{COO}^- + \text{3H}\_2\text{O} \leftrightarrow \text{CH}\_3\text{COO}^- + \text{H}^+ + \text{HCO}\_3^- + \text{3H}\_2\tag{5}$$

$$\text{C}\_6\text{H}\_{12}\text{O}\_6 + 2\text{H}\_2\text{O} \quad \leftrightarrow \text{ 2CH}\_3\text{COOH} + 2\text{CO}\_2 + 4\text{H}\_2\tag{6}$$

$$\text{CH}\_3\text{CH}\_2\text{OH} + 2\text{H}\_2\text{O} \rightarrow \text{CH}\_3\text{COO}^- + 3\text{H}\_2 + \text{H}^+\tag{7}$$

During this conversion process, the concentration of biological and chemical oxygen demand in the medium gets reduced. On the other hand, the hydrogen partial pressure is generated due to the presence of hydrogen gas inside the reactor. Methanogenic microbes, present in the digester, consume accumulated hydrogen gas.

Methanogenesis is the final step of anaerobic degradation of organic waste. In this step, methanogenic microbes are responsible for converting the acetic acid and hydrogen into methane (CH4) gas and carbon dioxide (CO2). Eqs. (8)–(10) show that the reaction occurs during methanogenesis phase as shown below:

$$\text{CH}\_3\text{COOH} \rightarrow \text{CH}\_4\text{+CO}\_2\tag{8}$$

$$\text{CO}\_2 + 4\text{H}\_2 \rightarrow \text{CH}\_4 + 2\text{H}\_2\text{O} \tag{9}$$

**7**

**Author details**

India

provided the original work is properly cited.

J. Rajesh Banu\* and R. Yukesh Kannah

\*Address all correspondence to: rajeshces@gmail.com

*Introductory Chapter: An Overview of Biogas DOI: http://dx.doi.org/10.5772/intechopen.82198*

China, Bangladesh, Pakistan, Sri Lanka and Nepal) and Africa (Burkina Faso, Ethiopia, Tanzania, Kenya and Uganda) are very successful in the operation of domestic scale digester. In Asia, approximately 47.876 million of domestic scale digesters were effectively operated to meet their daily needs. In that, China holds first place and accounts for 43 million domestic scale digester, India 4.75 million, Nepal 330,000, Bangladesh 36,000, Sri Lanka 6000 and Pakistan 4000. Similarly, Africa holds 60,000 domestic scale digesters, in that Kenya leads first place and accounts for 16,419, Ethiopia 13,584, Tanzania 13,037, Uganda 6504 and Burkina Faso 7518. Produced biogas was utilized for cooking and lighting purposes.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Department of Civil Engineering, Anna University Regional Campus, Tirunelveli,

$$\text{2CH}\_3\text{CH}\_2\text{OH} + \text{CO}\_2 \rightarrow \text{CH}\_4 + \text{2CH}\_3\text{COOH} \tag{10}$$

Methane-enriched biogas can be a promising source to displace the use of conventional fossil fuel. Biogas acts as a flexible energy source, which can be used for various applications like power, heat, transport and feedstock for chemical production. Biogas is the most significant product of (AD) process, and it comprises 60–70% of methane (CH4) gas, 25–35% of carbon dioxide (CO2) and remaining 5–10% of other corrosive gases. Biogas was more suitable to replace the demand of conventional fuel. Biogas has a calorific value of 6.0–6.5 kWh/m3 , which varies according to the percentage of biomethane content in the biogas. In addition to this, AD process indirectly reduces the cost of energy and fuel production. On the other hand, anaerobically digested residues have market value due to its nutrient content. It can be used as bio-fertilizer for agriculture crop production. AD process is termed as a golden process to eliminate the emission of GHG and reduce global warming issues.

According to the World Bioenergy Association 2017 report, the global biomethane production was approximately 35 billion m3 of methane. Overall, global biogas production was 1.28 EJ in the year 2014. Developed countries like the United States and Europe are the major contributors of biogas production throughout the world. Among them Europe is the world's largest biomethane producer. Around 18 billion m3 of biomethane was produced in the year 2015; it was half of the global biogas production. The produced biomethane was utilized for generation heat, electricity and transportation (vehicle fuel). Nearly 50% of total biogas was utilized for heat generation, and around 697 biomethane filling stations were employed in Europe [16]. Developing countries in Asia (India,

*Introductory Chapter: An Overview of Biogas DOI: http://dx.doi.org/10.5772/intechopen.82198*

*Anaerobic Digestion*

shown below:

hydrogen gas.

(CO2). Eqs. (5)–(7) show that the reaction occurs during acetogenesis phase as

C6H12O6 + 2H2O ↔ 2CH3COOH + 2CO2 + 4H2 (6)

CH3CH2OH + 2H2O → CH3COO<sup>−</sup> + 3H2 + H<sup>+</sup> (7)

During this conversion process, the concentration of biological and chemical oxygen demand in the medium gets reduced. On the other hand, the hydrogen partial pressure is generated due to the presence of hydrogen gas inside the reactor. Methanogenic microbes, present in the digester, consume accumulated

Methanogenesis is the final step of anaerobic degradation of organic waste. In this step, methanogenic microbes are responsible for converting the acetic acid and hydrogen into methane (CH4) gas and carbon dioxide (CO2). Eqs. (8)–(10) show

CH3COOH → CH4 + CO2 (8)

CO2 + 4H2 → CH4 + 2H2O (9)

2CH3CH2OH + CO2 → CH4 + 2CH3COOH (10)

according to the percentage of biomethane content in the biogas. In addition to this, AD process indirectly reduces the cost of energy and fuel production. On the other hand, anaerobically digested residues have market value due to its nutrient content. It can be used as bio-fertilizer for agriculture crop production. AD process is termed as a golden process to eliminate the emission of GHG and reduce global warming

According to the World Bioenergy Association 2017 report, the global

global biogas production was 1.28 EJ in the year 2014. Developed countries like the United States and Europe are the major contributors of biogas production throughout the world. Among them Europe is the world's largest biomethane

was half of the global biogas production. The produced biomethane was utilized for generation heat, electricity and transportation (vehicle fuel). Nearly 50% of total biogas was utilized for heat generation, and around 697 biomethane filling stations were employed in Europe [16]. Developing countries in Asia (India,

Methane-enriched biogas can be a promising source to displace the use of conventional fossil fuel. Biogas acts as a flexible energy source, which can be used for various applications like power, heat, transport and feedstock for chemical production. Biogas is the most significant product of (AD) process, and it comprises 60–70% of methane (CH4) gas, 25–35% of carbon dioxide (CO2) and remaining 5–10% of other corrosive gases. Biogas was more suitable to replace the demand

of conventional fuel. Biogas has a calorific value of 6.0–6.5 kWh/m3

biomethane production was approximately 35 billion m3

producer. Around 18 billion m3

that the reaction occurs during methanogenesis phase as shown below:

<sup>−</sup> + 3H2 (5)

, which varies

of methane. Overall,

of biomethane was produced in the year 2015; it

CH3CH2COO− + 3H2O ↔ CH3COO− + H<sup>+</sup> + HCO3

**6**

issues.

China, Bangladesh, Pakistan, Sri Lanka and Nepal) and Africa (Burkina Faso, Ethiopia, Tanzania, Kenya and Uganda) are very successful in the operation of domestic scale digester. In Asia, approximately 47.876 million of domestic scale digesters were effectively operated to meet their daily needs. In that, China holds first place and accounts for 43 million domestic scale digester, India 4.75 million, Nepal 330,000, Bangladesh 36,000, Sri Lanka 6000 and Pakistan 4000. Similarly, Africa holds 60,000 domestic scale digesters, in that Kenya leads first place and accounts for 16,419, Ethiopia 13,584, Tanzania 13,037, Uganda 6504 and Burkina Faso 7518. Produced biogas was utilized for cooking and lighting purposes.

### **Author details**

J. Rajesh Banu\* and R. Yukesh Kannah Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India

\*Address all correspondence to: rajeshces@gmail.com

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **References**

[1] Banu JR, Kavitha S. In: Singh L, Kalia VC, editors. Various Sludge Pretreatments: Their Impact on Biogas Generation BT—Waste Biomass Management—A Holistic Approach. Cham: Springer International Publishing; 2017. pp. 39-71

[2] Raj SE, Banu JR, Kaliappan S, Yeom I-T, Adish Kumar S. Effects of side-stream, low temperature phosphorus recovery on the performance of anaerobic/anoxic/ oxic systems integrated with sludge pretreatment. Bioresource Technology. 2013;**140**:376-384

[3] Kavitha S, Rajesh Banu J, Kumar G, Kaliappan S, Yeom IT. Profitable ultrasonic assisted microwave disintegration of sludge biomass: Modelling of biomethanation and energy parameter analysis. Bioresource Technology. 2018;**254**:203-213

[4] Zhang X, Chen M, Huang Y. Isothermal drying kinetics of municipal sewage sludge coupled with additives and freeze–thaw pretreatment. Journal of Thermal Analysis and Calorimetry. 2017;**128**:1195-1205

[5] Banu JR, Do Khac U, Kumar SA, Ick-Tae Y, Kaliappan S. A novel method of sludge pretreatment using the combination of alkalis. Journal of Environmental Biology. 2012;**33**:249

[6] Devlin DC, Esteves SRR, Dinsdale RM, Guwy AJ. The effect of acid pretreatment on the anaerobic digestion and dewatering of waste activated sludge. Bioresource Technology. 2011;**102**:4076-4082

[7] Kavitha S, Preethi J, Rajesh Banu J, Yeom IT. Low temperature thermochemical mediated energy and economically efficient biological disintegration of sludge: Simulation

and prediction studies for anaerobic biodegradation. Chemical Engineering Journal. 2017;**317**:481-492

[8] Cheng X-Y, Liu C-Z. Fungal pretreatment enhances hydrogen production via thermophilic fermentation of cornstalk. Applied Energy. 2012;**91**:1-6

[9] Fang W, Zhang P, Shang R, Ye J, Wu Y, Zhang H, et al. Effect of high pressure homogenization on anaerobic digestion of the sludge pretreated by combined alkaline and high pressure homogenization. Desalination and Water Treatment. 2017;**62**:168-174

[10] Divyalakshmi P, Murugan D, Sivarajan M, Sivasamy A, Saravanan P, Rai CL. Effect of ultrasonic pretreatment on secondary sludge and anaerobic biomass to enhance biogas production. Journal of Material Cycles and Waste Management. 2018;**20**:481-488

[11] Kavitha S, Yukesh Kannah R, Yeom IT, Do K-U, Banu JR. Combined thermo-chemo-sonic disintegration of waste activated sludge for biogas production. Bioresource Technology. 2015;**197**:383-392

[12] Kavitha S, Jayashree C, Kumar SA, Kaliappan S, Banu JR. Enhancing the functional and economical efficiency of a novel combined thermo chemical disperser disintegration of waste activated sludge for biogas production. Bioresource Technology. 2014;**173**:32-41

[13] Kannah RY, Kavitha S, Rajesh Banu J, Yeom IT, Johnson M. Synergetic effect of combined pretreatment for energy efficient biogas generation. Bioresource Technology. 2017;**232**:235-246

[14] Li C, Wang X, Zhang G, Li J, Li Z, Yu G, et al. A process combining

**9**

*Introductory Chapter: An Overview of Biogas DOI: http://dx.doi.org/10.5772/intechopen.82198*

hydrothermal pretreatment, anaerobic digestion and pyrolysis for sewage sludge dewatering and co-production of biogas and biochar: Pilot-scale verification. Bioresource Technology.

[15] Kavitha S, Rajesh Banu J, Subitha G, Ushani U, Yeom IT. Impact of thermo-chemo-sonic pretreatment in solubilizing waste activated sludge for biogas production: Energetic analysis and economic assessment. Bioresource

Technology. 2016;**219**:479-486

[16] Scarlat N, Dallemand J-F, Fahl F. Biogas: Developments and perspectives in Europe. Renewable

Energy. 2018;**129**:457-472

2018;**254**:187-193

*Introductory Chapter: An Overview of Biogas DOI: http://dx.doi.org/10.5772/intechopen.82198*

hydrothermal pretreatment, anaerobic digestion and pyrolysis for sewage sludge dewatering and co-production of biogas and biochar: Pilot-scale verification. Bioresource Technology. 2018;**254**:187-193

[15] Kavitha S, Rajesh Banu J, Subitha G, Ushani U, Yeom IT. Impact of thermo-chemo-sonic pretreatment in solubilizing waste activated sludge for biogas production: Energetic analysis and economic assessment. Bioresource Technology. 2016;**219**:479-486

[16] Scarlat N, Dallemand J-F, Fahl F. Biogas: Developments and perspectives in Europe. Renewable Energy. 2018;**129**:457-472

**8**

*Anaerobic Digestion*

**References**

2013;**140**:376-384

[1] Banu JR, Kavitha S. In: Singh L, Kalia VC, editors. Various Sludge Pretreatments: Their Impact on Biogas Generation BT—Waste Biomass Management—A Holistic Approach. Cham: Springer International Publishing; 2017. pp. 39-71

and prediction studies for anaerobic biodegradation. Chemical Engineering

Journal. 2017;**317**:481-492

Energy. 2012;**91**:1-6

2018;**20**:481-488

2015;**197**:383-392

[8] Cheng X-Y, Liu C-Z. Fungal pretreatment enhances hydrogen production via thermophilic fermentation of cornstalk. Applied

[9] Fang W, Zhang P, Shang R, Ye J, Wu Y, Zhang H, et al. Effect of high pressure homogenization on anaerobic digestion of the sludge pretreated by combined alkaline and high pressure homogenization. Desalination and Water Treatment. 2017;**62**:168-174

[10] Divyalakshmi P, Murugan D, Sivarajan M, Sivasamy A, Saravanan P, Rai CL. Effect of ultrasonic pretreatment on secondary sludge and anaerobic biomass to enhance biogas production. Journal of Material Cycles and Waste Management.

[11] Kavitha S, Yukesh Kannah R, Yeom IT, Do K-U, Banu JR. Combined thermo-chemo-sonic disintegration of waste activated sludge for biogas production. Bioresource Technology.

[12] Kavitha S, Jayashree C, Kumar SA, Kaliappan S, Banu JR. Enhancing the functional and economical efficiency of a novel combined thermo chemical disperser disintegration of waste activated sludge for biogas production. Bioresource Technology. 2014;**173**:32-41

[13] Kannah RY, Kavitha S, Rajesh Banu J, Yeom IT, Johnson M. Synergetic effect of combined pretreatment for energy efficient biogas generation. Bioresource

[14] Li C, Wang X, Zhang G, Li J, Li Z, Yu G, et al. A process combining

Technology. 2017;**232**:235-246

[2] Raj SE, Banu JR, Kaliappan S, Yeom I-T, Adish Kumar S. Effects of side-stream, low temperature phosphorus recovery on the performance of anaerobic/anoxic/ oxic systems integrated with sludge pretreatment. Bioresource Technology.

[3] Kavitha S, Rajesh Banu J, Kumar G, Kaliappan S, Yeom IT. Profitable ultrasonic assisted microwave disintegration of sludge biomass: Modelling of biomethanation and energy parameter analysis. Bioresource

Technology. 2018;**254**:203-213

[4] Zhang X, Chen M, Huang Y.

2017;**128**:1195-1205

2011;**102**:4076-4082

[7] Kavitha S, Preethi J, Rajesh Banu J, Yeom IT. Low temperature thermochemical mediated energy and economically efficient biological disintegration of sludge: Simulation

Isothermal drying kinetics of municipal sewage sludge coupled with additives and freeze–thaw pretreatment. Journal of Thermal Analysis and Calorimetry.

[5] Banu JR, Do Khac U, Kumar SA, Ick-Tae Y, Kaliappan S. A novel method of sludge pretreatment using the combination of alkalis. Journal of Environmental Biology. 2012;**33**:249

[6] Devlin DC, Esteves SRR, Dinsdale RM, Guwy AJ. The effect of acid

pretreatment on the anaerobic digestion and dewatering of waste activated sludge. Bioresource Technology.

**11**

Section 2

Anaerobic Digestion
