Integrating Green Chemistry and
Sustainable Engineering


Scrivener Publishing
100 Cummings Center, Suite 541J
Beverly, MA 01915-6106
Publishers at Scrivener
Martin Scrivener ()
Phillip Carmical ()


Integrating Green Chemistry
and Sustainable Engineering

Shahid-ul-Islam
Department of Textile Technology,
Indian Institute of Technology, Delhi, India


This edition first published 2019 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA
and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA
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Library of Congress Cataloging-in-Publication Data
ISBN 978-1-119-50983-7
Cover image: Pixabay.Com
Cover design by Russell Richardson

Set in size of 11pt and Minion Pro by Exeter Premedia Services Private Ltd., Chennai, India
Printed in the USA


Contents
Preface

xix

1 Third Generation Biofuels: A Promising
Alternate Energy Source
Mushtaq Ahmad Rather and Parveena Bano
1.1 Introduction
1.2 Biofuel Types
1.3 Advantages of Third Generation Biofuels
1.4 Technology of Third Generation Biofuel Production

1.5 Transformation Potential of Algae Into Third Generation
Biofuels
1.6 Recent Developments in Biomass Transformation Into
Third Generation Biofuels by
Hydrothermal Conversion (HTC)
1.7 Conclusion
References
2

Recent Progress in Photocatalytic Water Splitting by
Nanostructured TiO2-Carbon Photocatalysts – Influence
of Interfaces, Morphological Structures and
Experimental Parameters
V. Preethi, M. Mamatha Kumari, N. Ramesh Reddy,
U. Bhargav, K. K. Cheralathan, C. H. Shilpa Chakra and
M. V. Shankar
2.1 Photocatalysis
2.2 Carbon Nanotubes-TiO2 and Other Nanocomposite for
Photocatalytic Water Splitting
2.3 Factors Influencing Liquid-Phase Hydrogen Production
2.3.1 Direct Photolysis and Its Limitations
2.3.2 Need for Reducing Polysulphide Ions Formation

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Contents
2.3.3 Role of Sulphite Ions in Conversion of Photo
Sulphides to Thiosulphate
2.3.4 Influence of Catalyst Dosage
2.3.5 Effect of pH
2.3.6 Effect of Recycle Flow Rates and Reactor
Design on H2 Generation
2.3.7 Dependence of Hydrogen Production on
Volume and Depth of Photolytic Solution
2.3.8 Influence of Light Irradiation on Hydrogen Yield
2.3.9 Sulphur Recovery
2.3.10 Reusability of the Nanophotocatalysts
2.4 Factors Influencing Gas-Phase Photocatalytic

Hydrogen Production
2.4.1 Effect of H2S Gas Concentration
2.4.2 Effect of Gas Flow Rate
2.4.3 Effect of Catalyst Dosage
2.4.4 Effect of Light Irradiation
2.5 Future Prospects
References

3 Heterogeneous Catalytic Conversion of Greenhouse Gas
CO2 to Fuels
Kaisar Ahmad, Firdaus Parveen, Anushree and
Sreedevi Upadhyayula
3.1 Introduction
3.1.1 Greenhouse Gas CO2
3.1.2 Mitigation of CO2 Concentration
3.1.3 Reducing CO2 Emissions
3.1.4 Zero Emissions
3.1.5 Carbon Capture and Storage or Sequestration (CCS)
3.2 Thermodynamics of CO2 Hydrogenation to
Methanol, DME, and Hydrocarbons
3.3 Catalytic Conversion of CO2 to Methanol, DME, and
Hydrocarbons
3.3.1 Effect of Alkali Promotors
3.3.2 Effect of Metal Particle Crystal Phase in CO2
Hydrogenation
3.3.3 Effect of Support
3.4 Mechanism of CO2 Hydrogenation to Methanol, DME, and
Hydrocarbons

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Contents vii
3.4.1 CO2 Hydrogenation to Methanol
3.4.1.1 Formate Route
3.4.1.2 Carboxylate Route
3.4.1.3 RWGS Route
3.4.2 CO2 Hydrogenation to Dimethyl Ether
3.4.3 CO2 Hydrogenation to Hydrocarbons
3.4.3.1 Indirect Conversion of CO2 Into
Hydrocarbons
3.4.3.2 Direct Conversion of CO2 Into
Hydrocarbons
3.5 Challenges and Opportunities in CO2
Hydrogenation Process
References
4 Energy Harvesting: Role of Plasmonic Nanocomopsites
for Energy Efficient Devices
Jaspal Singh, Subhavna Juneja and Anujit Ghosal
4.1 Introduction
4.2 Plasmonic Nanostructures
4.3 Plasmonic Nanocomposites
4.4 Plasmonic Nanocomposites for Energy Harvesting
4.4.1 Plasmonic Nanocomposites for
Photovoltaic Applications
4.4.2 Plasmonic Nanocomposites for Water Purification
4.4.3 Plasmonic Nanocomposites for Hydrogen
Production
4.5 Conclusions
References
5 Catalytic Conversion of Biomass Derived Cellulose to
5-Hydromethyl Furfural

Firdaus Parveen, Kaiser Ahmad and Sreedevi Upadhyayula
5.1 General Overview
5.2 Biomass Conversion Processes
5.3 HMF as a Platform Chemical
5.4 Hydrolysis of Cellulose to Glucose
5.4.1 Hydrolysis of Cellulose to Glucose
Using Liquid Acid
5.4.2 Hydrolysis of Cellulose to Glucose
Using Solid Acid

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Contents
5.4.3 Hydrolysis of Cellulose to Glucose
Using Ionic Liquids
5.4.3.1 Ionic Liquids
5.4.3.2 Cellulose Hydrolysis in Ionic Liquids
Using Mineral Acid as Catalyst
5.4.3.3 Cellulose Hydrolysis in Ionic Liquids
Using Metal Salts as Catalyst
5.4.3.4 Cellulose Hydrolysis in Ionic Liquids
Using Heterogenous Catalyst
5.4.3.5 Cellulose Hydrolysis in Ionic Liquids
Using Ionic Liquids as Catalyst
5.5 Glucose Conversion to 5-Hydroxymethyl Furfural
5.6 Conclusion and Future Prospects
References

6 Raman “Green” Spectroscopy for Ultrasensitive

Analyte Detection
Subhavna Juneja, Anujit Ghosal and Jaydeep Bhattacharya
6.1 Introduction
6.2 Application of Nanotechnology in Medicine
6.2.1 Bio-Imaging
6.2.2 Bio-Sensing and Diagnosis
6.2.3 Targeted Drug Delivery
6.2.4 Food Technology
6.2.5 Regenerative Medicine
6.2.6 Nanomedicine with Emphasis on
Early Disease Detection
6.2.7 Raman and Surface Enhanced Raman
Spectroscopy (SERS)
6.2.7.1 Raman “Green” Spectroscopy
6.3 Conclusion and Future Outlook
References
7 Microwave Synthesized Conducting Polymer-Based Green
Nanocomposites as Smart Promising Materials
Neha Kanwar Rawat and P.K Panda
7.1 Introduction
7.2 Brief Introduction of Conducting Polymers
7.2.1 CPs
7.2.2 Synthesis of Conducting Polymers

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Contents ix
7.3 Microwave Synthesis
7.3.1 Principle of MW Heating
7.3.2 Dielectric Properties
7.3.3 Significance of Tan δ
7.3.4 Advantages of Microwave Over
Conventional Heating

7.4 Literature/Research Present
7.4.1 PANI and Derivatives
7.4.2 PTh and Their Derivatives
7.5 Application of MW synthesized CPs in varying Arena
7.6 Conclusion and outlook
References
8

Biobased Biodegradable Polymers for Ecological
Applications: A Move Towards Manufacturing Sustainable
Biodegradable Plastic Products
Sudhakar Muniyasamy, Kulanthaisamy Mohanrasu,
Abongile Gada, Teboho Clement Mokhena,Asanda Mtibe,
Thulasinathan Boobalan, Vimla Paul and Alagarsamy Arun
8.1 Introduction
8.2 Biodegradable and Compostable Polymer Materials
8.2.1 Defining Biodegradability
8.2.2 Biodegradable Polymers (Fossil or Renewable)
8.3 Biopolymer From Microbial Synthesis and Its Applications
8.3.1 Intracellular Biological Polymers
8.3.1.1 Application of PHAs
8.3.2 Extracellular Polymeric Substances (EPS)
8.3.2.1 Important Properties of EPS
8.4 Chitin
8.4.1 Chitin Recovery
8.4.2 Characterization of Chitin
8.4.3 Applications of Chitin
8.5 Conventional Synthesis of Biopolymers and Its Application
8.5.1 Biorenewable Biopolymers
8.6 End-of-Life of Biopolymer Based Materials and

Composites and Its Applications
8.6.1 Biopolymer Blend
8.6.2 Biocomposites
8.6.2.1 PLA-Natural Fibre Composite
8.6.2.2 PLA Based Composites From Petro
Based Biodegradable Polymer

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Contents
8.6.2.3 PLA-Non-Biodegradable Polymer from
Renewable and Non-Renewable Sources
8.6.2.4 PLA Based Composites from
Renewable Biodegradable Polymer PLA/
microbial Polyester
8.7 Concluding Remarks
References

9 Cashew Nut Shell Liquid (Phenolic Lipid) Based Coatings:
Polymers to Nanocomposites
Fahmina Zafar, Anujit Ghosal, Eram Sharmin and
Nahid Nishat
9.1 Introduction
9.2 CNSL (Col)

9.3 CNSL (Col) Based Polymeric Coatings
9.3.1 CNSL (Col)-Epoxy Coatings
9.3.2 CNSL (Col) Polyamides (CPAs) Coatings
9.3.3 CNSL (Col)-Formaldehyde/ Furfuraldehyde
Coatings
9.3.4 CNSL (Col) phenalkamines coatings
9.3.5 CNSL (Col) Benzoxazine (Bnz) Coatings
9.3.6 Col-Polyol Coatings
9.3.7 CNSL(Col)-Polyurethane (PU) Coatings
9.4 CNSL (Col) Non Isocyanate Polyurethanes (NIPUs)
or Green Coatings
9.5 CNSL (Col) Waterborne and UV Cured Coatings
9.6 CNSL(Col) Based Antifouling/antibacterial Coatings
9.7 CNSL (Col) Based Nanostructured Coatings and
Nanocomposites Coatings
9.8 Conclusions
References
10 Ionic Liquids as Potential Green Solvents Their Interactions
with Surfactants and Antidepressant Drugs
Nisar Ahmad Malik and Ummer Farooq
10.1 Introduction
10.2 Basic Properties of ILs
10.3 Applications of ILs
10.4 Antidepressant Drugs
10.5 Ionic Liquid – Surfactant and Ionic Liquid-Antidepressant
Drug Interaction

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Contents xi

10.6 Conclusions and Perspectives
References
11 Role of Green and Integrated Chemistry in
Sustainable Metallurgy
Sadia Ilyas, Muhammad Farhan and Haq Nawaz Bhatti
11.1 Introduction
11.2 Role of Green and Integrated Chemistry in Sustainbale
Metallurgy of Primary Resources
11.2.1 Role of Integrated Chemistry in Processing of
Sulfide Minerals
11.2.2 Role of Integrated Chemistry in Processing of
Oxide Minerals
11.3 Role of Green and Integrated Chemistry in Sustainable
Metallurgy of Secondrey Resources
11.3.1 Role of Integrated Chemistry in Processing of
Smelter Dust
11.3.2 Role of Integrated Chemistry in Processing of
Converter/Smelter Slags
11.3.3 Role of Integrated Chemistry in Processing of
Spent Catalyst/Lithium Ion Batteries (SC/LIBs)
11.3.4 Role of Integrated Chemistry in Processing of
Waste Electric and Electronic Equipment (WEEEs)
11.3.4.1 Processing of Precious Metals From
WEEEs with Integrated Routes
11.3.4.2 Processing of Rare Earth Elements from
WEEEs with Integrated Routes
11.4 Perspectives on Integrated Chemical and Biological
Routes for Mineral/Material Processing
References
12 Biological Nitrogen Fixation and Biofertilizers as

Ideal Potential Solutions for Sustainable Agriculture
Shymaa Ryhan Bashandy, Mohamed Hemida Abd-Alla
and Magdy Mohamed Khalil Bagy
12.1 Introduction
12.2 Non-Symbiotic Biological Nitrogen Fixation
12.2.1 Factors Affecting Non-Symbiotic N2 Fixation
12.2.1.1 Soil and Environmental Factors
12.3 Symbiotic Biological Nitrogen Fixation
12.3.1 Rhizobia

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Contents
12.3.2 Legumes
12.3.3 Legume - Rhizobium Symbiosis
12.3.4 The Signals From the Host Plants (Flavonoids)
12.3.5 Nod Factors
12.3.6 Molecular Genetics of Nodulation (The Nod Genes)
12.3.7 Nodule Formation
12.3.8 Nitrogen Fixation
12.3.9 Ecological Factors Affecting Signal Exchange
12.4 Plant Growth Promoting Rhizobacteria
12.4.1 Direct Mechanisms of PGPR
12.4.1.1 The Biological N2 Fixation
12.4.1.2 Phosphate Solubilization
12.4.1.3 Potassium Solubilization
12.4.1.4 Iron Chelation (Siderophores Production)
12.4.1.5 Phytohormone Production
12.4.2 Indirect Mechanics of PGPR
12.5 Conclusions and Future Research
References

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13 Natural Products in Adsorption Technology
Ahmet Gürses
13.1 Introduction
13.2 Adsorption and Surface Chemistry
13.3 Characteristics of Adsorbents and Selection of Adsorbent
13.4 Common Processes in Adsorption Technology
13.5 Adsorpbents Used in Adsorption Technology
References

397

14 Role of Microbes in the Bioremediation of Toxic Dyes
Tanvir Arfin, Kamini Sonawane, Piyush Saidankar and

Shraddha Sharma
14.1 Introduction
14.2 Dye
14.3 Classification of Dye
14.4 Dye Colour
14.4.1 Factor
14.5 Techniques for the Removal of Dye
14.6 Decolouration Mechanisms of Microbial
14.7 Biosorption
14.7.1 Merits of Biosorption Process

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Contents xiii
14.7.2 Factors Influences Metal Biosorption
14.8 Consortia of Microorganisms
14.9 Decolourization by Fungi
14.9.1 Factors Affecting Dye Decolourisation by
Fungal Biomass
14.10 Dye Removal by Bacteria
14.10.1 Gram-Positive
14.10.2 Gram-Negative
14.10.3 Bacteria Classification by Shape
14.10.4 Decolourization by Bacteria
14.10.5 Bacterial Strain Used for Dye Removal
14.10.6 Different Bacteria Removes Different Dye
14.11 Algae
14.11.1 Classification of Algae
14.11.2 Microalgae
14.11.3 Effect of Algal Photosynthesis
14.11.4 Algae for Dye Removal
14.12 Conclusion
References
15 Valorization of Wastes for the Remediation of Toxicants
from Industrial Wastewater
Shumaila Kiran, Tahsin Gulzar, Sarosh Iqbal,
Noman Habib, Atya Hassan and Saba Naz
15.1 Introduction
15.2 Toxicants Present in Industrial Waste Water
15.2.1 Heavy Metals
15.2.1.1 Chromium (Cr)
15.2.1.2 Cadmium (Cd)

15.2.1.3 Iron (Fe)
15.2.1.4 Nickel (Ni)
15.2.1.5 Lead (Pb)
15.2.1.6 Copper (Cu)
15.2.1.7 Zinc (Zn)
15.2.1.8 Mercury (Hg)
15.2.1.9 Selenium (Se)
15.2.1.10 Arsenic (As)
15.2.2 Dyes
15.3 Waste Volarization
15.3.1 What is Adsorption?

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Contents
15.3.1.1 Mechanism of Adsorption
15.3.1.2 Types of Adsorption
15.3.2 Types of Wastes
15.3.2.1 Natural Materials
15.3.2.2 Agricultural Wastes
15.3.2.3 Biomass
15.3.2.4 Industrial Wastes

15.6 Conclusion
References

16 Wound Healing Potential of Natural Polymer: Chitosan
“A Wonder Molecule”
Tara Chand Yadav, Amit Kumar Srivastava, Navdeep
Raghuwanshi, Naresh Kumar, Ramasare Prasad and
Vikas Pruthi
16.1 Introduction
16.2 Wound Healing
16.3 Need for Advance Dressing Material
16.4 Chitosan
16.5 Physicochemical Properties of Chitosan
16.5.1 Crystalline Nature
16.5.2 Molecular Weight
16.5.3 Degree of N-Acetylation (DA)
16.5.4 Solubility and Charge Density
16.5.5 Chemical Reactivity
16.5.6 Film-Forming Properties
16.5.7 Ion Binding
16.5.8 Gelling Behavior
16.5.9 Porosity
16.5.10 Biodegradability
16.5.11 Non-Immunogenic Nature
16.5.12 Hemostatic Property
16.6 Wound Healing Applications of Chitosan
16.6.1 Chitosan Hydrogels
16.6.1.1 Physical Hydrogels
16.6.1.2 Chemical Hydrogels
16.6.2 Chitosan as Antimicrobial Agent

16.6.3 Chitosan-Based Natural/ Synthetic Polymer
Scaffolds for Wound Healing

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Contents
16.6.4 Chitosan-Based Composite Scaffolds for
Wound Healing
16.6.5 Chitosan-Based Oil Restrained Scaffolds for
Wound Healing
16.6.6 Chitosan-Plant Extract Based Scaffolds for Wound
Healing
16.6.7 Chitosan Derivatives for Wound Healing
16.6.7.1 Trimethyl Chitosan
16.6.7.2 Toxicity Assessment of Tri-Methyl
Chitosan
16.6.7.3 Role of Trimethyl Chitosan in
Wound Healing
16.6.7.4 Role of Carboxymethyl Chitosan
and Carboxymethyl-Trimethyl Chitosan
16.6.8 Chitosan/Derivatives-Peptides Conjugates for
Wound Healing
16.6.9 Chitosan-Based Commercial Wound
Dressing Bandages
16.7 Conclusion and Future Perspectives

References
17 Nanobiotechnology: Applications of Nanomaterials
in Biological Research
Muhammad Irfan Majeed, Haq Nawaz Bhatti,
Haq Nawaz and Muhammad Kashif
17.1 Introduction
17.2 Classification of Nanomaterials
17.2.1 Liposomes
17.2.2 Superparamagnetic Nanoparticles
17.2.3 Fullerenes: Bucky Balls and Carbon Nanotubes
17.2.4 Dendrimers
17.2.5 Quantum Dots
17.3 Bio-Inspired Green Synthesis of Nanomaterials
17.4 Green Synthesis of Nanomaterials
17.5 Applications of Nanomaterials in Biology Research
17.5.1 Imaging and Labelling
17.5.2 Nano Biosensors
17.5.3 Tissue Engineering
17.5.4 Dentistry
17.5.5 Antimicrobial Therapy
17.5.6 Wound Healing

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Contents
17.5.7 Drug Delivery

17.5.8 Gene Delivery
17.6 Summary
References

18 Biotechnology: Past-to-Future
Tanvir Arfin and Kamini Sonawane
18.1 Introduction
18.2 History
18.3 Global Forum
18.4 Functions of the Global Forum
18.5 Objectives of Biotechnology Development
18.5.1 So What Should be the Objectives While
Considering the Biotechnological Area?
18.6 Categorization of Biotechnology
18.6.1 Ancient Biotechnology
18.6.2 Classical Biotechnology
18.6.3 Modern Biotechnology
18.7 Biotechnology Categories
18.7.1 Green Biotechnology
18.7.2 White Biotechnology
18.7.2.1 Industrial Sustainability
18.7.2.2 Applications
18.7.3 Blue Biotechnology
18.7.3.1 Applications
18.7.4 Red Biotechnology
18.7.5 Environmental Biotechnology
18.7.6 Genetic Engineering
18.8 Need of Biotechnology
18.9 Heal the World
18.10 Fuel The World

18.11 Feed the World
18.12 Health and Medicines
18.13 Future of Biotechnology
18.14 Advantages of Biotechnology
18.15 Opportunities and Risks
18.16 Biotechnology Industry
18.17 Innovation
18.18 Future of Biotechnology
18.19 Conclusion
References

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Contents xvii
19 Biogenic Nanoparticles as Theranostic Agents:
Prospects and Challenges
Navdeep Raghuwanshi, Amit Kumar Srivastava, Tara Chand
Yadav, Sonam Gupta and Vikas Pruthi
19.1 Introduction
19.2 Phytochemicals Stabilized Biogenic Nanoparticles as
Theranostic Agents
19.2.1 Antimicrobial Applications of

Biogenic Nanoparticles
19.2.2 Antioxidants and Anti-Inflammatory Applications
of Biogenic Nanoparticles
19.2.3 Antineoplastic Applications of Biogenic
Nanoparticles
19.2.4 Dermatological Applications of Biogenic
Nanoparticles
19.2.5 Catalytic Applications of Biogenic Nanoparticles
19.2.6 Antidiabetic Applications of Biogenic Nanoparticles
19.2.7 Biosensing Applications of Biogenic Nanoparticles
19.3 Biosurfactants Stabilized Biogenic Nanoparticles as
Theranostic Agent
19.3.1 Antimicrobial Activity of Biosurfactant Stabilized
Metallic Nanoparticles
19.3.1.1 Glycolipid based Nanoparticles
19.3.1.2 Lipopeptide Stabilized Nanoparticles
19.4 Applications of Nanoparticles in Tissue Engineering
19.5 Toxicological Effects of Nanoparticles
19.6 Prospects and Challenges
References
Index

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Preface
Green chemistry and engineering plays a growing role in the chemical
processing industries. Green chemistry and engineering are relatively new
areas focused on minimizing generations of pollution by utilizing alternative feedstocks, developing, selecting, and using less environmentally
harmful solvents, finding new synthesis pathways, improving selectivity
in reactions, generating less waste, avoiding the use of highly toxic compounds, and much more. In an effort to advance the discussion of green
chemistry and engineering, this book contains 19 chapters describing
greener approaches to the design and development of processes and products. The contributors describe the production of third generation biofuels,
sustainable and economic production of hydrogen by water splitting using
solar energy, efficient energy harvesting, mechanisms involved in the conversion of biomass, green nanocomposites, bio-based polymers, ionic liquids as green solvents, sustainable nitrogen fixation, bioremediation, and
much more. The book aims at motivating chemists and engineers, and also
undergraduate, postgraduate, Ph.D students and postdocs to pay attention
to an accute need for the implementation of green chemistry principles
in the field of chemical engineering, biomedical engineering, agriculture,
enviromental enginnering, chemical processing and material sciences.
In conclusion, it is my pleasant duty to thank all the authors for contributing their time and expertise in preparing the informative and in-depth

chapters related to areas of green chemistry and engineering which has
made this book a reality. I would like to express my sincere appreciation to
Martin Scrivener (Scrivener Publishing) for inviting me to put together a
textbook on integrating green chemistry and engineering.
Shahid-ul-Islam
Indian Institute of
Technology Delhi
(IITD), Hauz Khas,
New Delhi, India
November 14, 2018
xix


1
Third Generation Biofuels: A Promising
Alternate Energy Source
Mushtaq Ahmad Rather1,* and Parveena Bano2
1

Associate Professor, Chemical Engineering Department, National Institute of
Technology (NIT) Srinagar Kashmir
2
Assistant Professor, SKUAST-K, Srinagar Kashmir, Shalimar, India

Abstract
Global energy demand is projected to increase by at least 50 % by 2030. Fossil
fuels available at present cannot catch-up the current demand. Continuous use
of fossil fuels for energy purposes has caused devastating effects to our environment due to greenhouse gas emissions. Thus search for ‘clean energy’ or green and
sustainable renewable energy as an alternative to fossil fuels is the need of hour.
Green and sustainable renewable energy sources are important to foster a transition towards more sustainable energy availability. Among the several alternatives

available at present, biofuels have attracted huge attention. Use of biofuels provides
environmental benefits by decreasing the harmful emissions of gases like CO2, SOx
etc. Biofuels have attracted intense debate from a variety of perspectives, including
societal, economic, and environmental. First-generation biofuels are made from
sugars, starch and vegetable oils, so have an impact on the food security. Second
generation biofuels generated from plant material may lead to felling of trees and
shrubs. Biofuels generated from non-food crops like microalgae and macroalgae
are referred to as third generation biofuels, have great potential to meet part of
future global energy demand without making any compromise with human food
security. In the present chapter, we present a review of recent research interests in
the different aspects of production of third generation biofuels by hydrothermal
conversion, one of the thermal conversion routes.
Keywords: Hydrothermal conversion, biofuels, energy, biomass

*Corresponding author:
Shahid-ul-Islam (ed.) Integrating Green Chemistry and Sustainable Engineering, (1–22) © 2019
Scrivener Publishing LLC

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1.1

Integrating Green Chemistry and Sustainable Engineering

Introduction

Fossil fuels have been primary source of energy for centuries now. However

their fast depletion and associated harmful effects on the climate (by
increasing the atmospheric green house gas emissions) , has led to search
for ‘clean energy’. To tackle the problem, environmentally friendly alternate
sources of energy are being harnessed. Some of the options of clean energy
sources available are solar, wind, tidal and biomass. Utilization of biomass
in various transformed forms has proved to be an adequate way-out for
meeting the part of global energy demand [1]. Various forms of biomass in
nature are wood, vegetation, crops, aquatic plants and algae etc. Biomass
can be transformed into a versatile fuel referred to as biofuel, being studied
and implemented universally nowadays. Study of biofuels has transformed
into an area of complex interest and debate from various reasons including
societal, economic, and environmental. Biofuels are renewable fuels, having potential to decrease several harmful emissions such as soot, carbon
monoxide, and carbon dioxide [2]. Among the main biofuel producing
countries in world for transportation, USA and UE have taken lead and
already set specific targets for future.USA has planned to substitute 20% of
road transport fuel with biofuel by 2022, while UE has adopted 10% as a
goal of biofuel for transport energy by 2020 [3].
Green and sustainable renewable energy sources are important to foster
a transition towards more sustainable energy availability. Biomass can be
used to produce and substitute fossil fuels in many choices, to replace the
petrochemical compounds. As oil is processed in a refinery to fuels, and
chemicals; the “biorefinery” concept is equivalent to an oil refinery because
biomass is transformed into various products, ranging from chemicals to
biofuels [4].
Biofuels are made through the conversion of biomass in three different
ways; thermal conversion, chemical conversion and biochemical conversion. The resulting biofuel can be produced in solid, liquid or a gaseous
form.
Microalgae can be converted to biofuels mainly by two routes viz. biochemical fermentation (anaerobic digestion) and thermo chemical processes. Thermochemical processes include gasification, pyrolysis and
hydrothermal processing. Gasification involves the partial controlled oxidation of organic material to syngas. Syngas contains CO, H2 and CO2.
Apart from direct combustion, the other promising application of syngas

is its conversion to synthetic gas which later can be converted to liquid
fuel (GTL), by the Fisher-Tropsch process. Above converts H2 and CO


Third Generation Biofuels

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to straight chain liquid hydrocarbons which are suitable renewable substitute to petroleum derived diesel fuel. Pyrolysis refers to the thermal
decomposition of feedstocks in the absence of air. The process drives off
the moisture and volatiles, improves the handling properties and increases
the carbon content of a fuel. At temperatures up to 300 °C the process is
known as torrefaction which is being increasingly used to process biomass
to a more suitable solid fuel for co-combustion with coal. At higher temperatures the product distribution favours the production of liquid bio oil,
a highly oxygenated, acidic liquid resembling crude oil.
Pyrolysis in the presence of subcritical liquid water is called hydrothermal conversion (HT) [5]. The process generates both solid and liquid
biofuels. The process may be referred to as hydrothermal carbonization
(HTC) or hydrothermal liquefaction (HTL) based up on whether solid or
liquid product respectively, has been emphasized in the generation process. The solid fuel generated in HT conversion is referred to as hydrochar
(biochar) and liquid product as bio-crude or bio oil.
Hydrothermal conversion involves the reaction of biomass in water at
high temperature and pressure with or without the catalyst. The hydrothermal processing of biomass was investigated by Shell research in the
1980s [6]. Hydrothermal processing of lignocellulosic biomass has received
extensive attention over the last two decades for production of solid fuels,
liquid fuels (subcritical conditions) and for gaseous fuels (supercritical
conditions) [7, 8].
A non hydrothermal energy conversion pyrolysis process of biomass
requires its prior drying. Prior drying of biomass necessitates expensive and energy intensive dewatering and drying steps for processing of aquatic weeds and microalgae, which have enormous amounts
of water accompanied with them. An alternative route is to convert the
aquatic biomass into biofuels in the aqueous phase itself, thereby obviating biomass drying. A simple comparison of the enthalpies of liquid

water at 350 °C and water vapor at 50 °C (i.e., drying the biomass) indicates that processing in liquid water saves 921 kJ/kg. Hot compressed
liquid water near its thermodynamic critical point (Tc = 373.95 °C,
Pc = 22.064 MPa) behaves very differently from liquid water at room temperature. As water is heated along its vapor–liquid saturation curve, its
dielectric constant decreases due to the hydrogen bonds between water
molecules being fewer and less persistent. The reduced dielectric constant
enables hot compressed water to solvate small organic molecules, allowing organic reactions to occur in a single fluid phase. Additionally, the ion
product of water increases with temperature up to about 280 °C, but then
decreases as the critical point is approached. This higher ion product leads


Integrating Green Chemistry and Sustainable Engineering

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Inser gas
out

4

5
6
Inser
gas ir

3
1. Reactor
2. Band heater
3. Thermocouple
4. Controller
5. Pressure gauge

6. Strirrer

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Figure 1.1 Schematic diagram of a hydrothermal conversion reactor.

to higher natural levels of hydronium ions in hot compressed water, which
can accelerate the rates of acid-catalyzed hydrolytic decomposition reactions [9]. Hydrothermally processing wet biomass can produce a hydrochar that retains a large proportion of the chemical energy and lipids in
the original biomass. These char-bound lipids can be reacted with alcohol
to produce biodiesel. At same time processing of wet aquatic biomass also
produces crude bio-oil. Figure  1.1 given above presents a general schematic diagram of a hydrothermal conversion reactor used to produce the
third generation biofuels.
Biomass consists primarily of proteins, carbohydrates, and lipids; the
principal role of hydrothermal conversion is to decompose the biomacromolecules into smaller molecules that can then be further treated, if
desired, to produce specific fuels.
The hydrothermal environment promotes the hydrolytic cleavage of ester
linkages in lipids, peptide linkages in proteins, and glycosidic ether linkages
in carbohydrates. These cleavage reactions can be accelerated by catalysts [9].
Cellulose is not soluble in water at standard conditions, but starts dissolving at 180 °C and completely dissolves around 330 °C. Due to amorphous
structure, hemicellulose is easily hydrolyzed in waters at temperatures
above 160 °C to monomers, which could be, at acid water conditions further transformed into chemicals. Lignin is chemically most resistant component of lignocelluloses. Dissolution and hydrolysis to monomers starts
in near and supercritical water [10]. Homogenous catalysts like Na2CO3,
K2CO3, NaOH, KOH, HCOOH, CH3COOH, zeolite have received attention for hydrothermal conversion. Recently some common heterogeneous
catalysts have also been studied [9].


Third Generation Biofuels


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Present chapter gives an exhaustive overview of different biofuel types,
advantages of third generation biofuels and the technology involved in
their production. Further transformation of algae into third generation
biofuels with recent developments in the field of hydrothermal conversion
processing has also been focused.

1.2

Biofuel Types

Green energy is renewable energy that is generated from sources that are
considered environmentally friendly. The term biofuel is referred to as liquid, solid or gaseous fuels predominantly produced from biomass by green
pathways. Biofuel is produced through contemporary biological processes,
such as agriculture and anaerobic digestion, rather than a fuel produced by
geological processes such as those involved in the formation of fossil fuels,
such as coal and petroleum. The biomass can be converted to convenient
energy-containing substances in three different ways: thermal conversion,
chemical conversion, and biochemical conversion. First generation biofuels are made from the sugars and vegetable oils, which are found in arable
crops. Second generation biofuels also known as advanced biofuels are
made from lignocellulosic biomass or woody crops, agricultural residues
or waste, which makes it harder to extract the required fuel. Advanced
biofuels or biofuels produced from lignocellulosic materials made-up only
0.2% of total biofuel production (Year 2010). Third generation biofuels are
the fuels derived from aquatic originated biomass, predominantly in form
of algae, which are being largely focused nowadays.
Biofuels can be produced from non-toxic and biodegradable renewable
resources such as starch, vegetable oils, animal fats, waste biomass and
algal biomasses [11]. According to the recent classification of biofuels by

the European Parliament [12], they are classified as: first-generation biofuels, as those obtained from crops and animal fats, and based on mature
and well-established technologies; second-generation biofuels, as those
mainly obtained from ligno-cellulose biomass (i.e., wood); and third-generation biofuels, “The most accepted definition of third-generation biofuels is ‘fuels that are produced from algae-derived biomass’” [12].
First-generation biofuels include ethanol and biodiesel and are
directly related to a biomass that is more than often edible. Ethanol is
generally produced from the fermentation of C6 sugars (mostly glucose). Only a few different feedstocks, mostly sugarcane or corn, are
actually used for the production of first-generation bioethanol. Other
more marginal feedstock used to produce first-generation bioethanol


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Integrating Green Chemistry and Sustainable Engineering

includes but are not limited to whey, barley, potato wastes, and sugar
beets. Sugar cane is a common feedstock for biofuel production, Brazil
being one of the leading countries for its use. Second-generation biofuels are defined as fuels produced from a wide array of different feedstocks, especially non-edible lignocellulosic biomass. The conversion
process for production of second-generation biofuels is usually done by
two different approaches, “thermo” and “bio” pathways. The “thermo”
approach covers specific processes where biomass is heated with a
minimal amount of oxidizing agent, if any. All processes in that category lead to conversion of biomass into three fractions: solid known
as biochar, liquid referred to as pyrolytic oil or bio-oil, and gas known
as syngas, which is usually composed of carbon monoxide, hydrogen,
short chain alkanes, and carbon dioxide. The “bio” pathway on other
hand is somewhat comparable with a pulping process because, in most
cases, cellulose is first isolated from the lignocellulosic biomass. Many
processes have been considered, including classical pulping processes,
steam explosion, and organosolv processes. Isolation of cellulose is a
technological challenge because it has to produce the highest purity
of cellulose to remove most inhibitors without consuming too much

energy or too many chemicals. The most accepted definition for thirdgeneration biofuels is fuels that would be produced from algal biomass,
which has a very distinctive growth yield as compared with classical
lignocellulosic biomass. Production of biofuels from algae usually relies
on the lipid content of the microorganisms. Usually, species are targeted having high lipid content (around 60% to 70%) and their high
productivity (7.4 g/L/d for Chlorella protothecoides). Lipids obtained
from algae can be processed via transesterification or can be submitted
to hydrogenolysis to produce kerosene grade alkane suitable for use as
drop-in aviation fuels [13].
Biofuel generations from algae is promising as algae can be grown
quickly, are non toxic and biodegradable, and during their growth green
house gas fixation takes place. Also growing algae does not need arable
land, so there is no competition with food or feed crops [14] Algae (both
macro and micro) have been suggested as potential future sources of
renewable energy in transport in Europe [15].

1.3

Advantages of Third Generation Biofuels

The first generation biofuels possess notable economic, environmental and
political concern as the mass production of biofuel requires more arable