Table Of ContentBiomass, Bioproducts and Biofuels
Jorge M.T.B. Varejão
Department of Exact Science
Agrarian School/CERNAS/I. I. A.
Polytechnic Institute of Coimbra
Portugal
With contribution from
Chapter 7
Ferreira, Joana D., Martins, Clara B.,
Assunção, Mariana F.G. and Santos, Lilia M.A.
Coimbra Collection of Algae (ACOI)
Department of Life Sciences
University of Coimbra, Portugal
R
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First edition published 2022
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Library of Congress Cataloging-in-Publication Data (applied for)
ISBN: 978-0-367-35408-4 (hbk)
ISBN: 978-1-032-12424-7 (pbk)
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DOI: 10.1201/9780429340543
Typeset in Palatino
by Radiant Productions
To Gonçalo and André
Preface
At the beginning of the third decade of the 21st century, Humanity is under
pressure from the scarcity of energy resources, compounded by the great
environmental damage caused to Earth by fossil materials already burned.
The world population approaches 10 billion people, each with the ambition
of a better standard of living that is currently being obtained mainly at
the expense of using even more fossil materials. This has been happening
since the 1970s last century and has led to major climate changes, which are
becoming more evident each year and leading to damage and economic loss
worldwide. The change in the energy supply model is underway, but there is
still sometime before it transforms into a greener version. In the meantime, any
new technology that helps to reduce carbon dioxide emissions is welcome as
it contributes to lessen the gravity of the situation. There placement of electric
cars is a beginning in such an effort and its use is expected to accelerate in the
coming years. However, in some cases, electricity is produced from burning
fossil fuels, annihilating or aggravating the environmental effort. Greener
electricity sources, such as wind, sea waves and all possible renewable energy
sources, are required to solve the problem. Other areas will eventually under
go a longer transition period due to technical difficulties in replacing fossil
fuels, e.g., commercial air travel.
Biomass is a renewable source that can contribute to replacing the use
of fossil materials without contributing to net emissions, since its growth
occurs through the absorption of CO2 from the atmosphere and not through
the subsoil extraction of carbon-based substances. Biomass has the potential
to be converted into liquid fuels, domestic and industrial solvents, plastics,
textile fibers and almost all the goods that modern society requires. However,
this objective will only be effective if the prices of these new raw material
variants are competitive in relation to fossil carbons, which in turn requires a
strong effort in research and some period of evolution.
Biomass exists everywhere, but often in places and terrains that make its
collection difficult or in accessible by machine tools. Obtaining it with human
labour makes the price of any derivative very high and uncompetitive,
with exception for small niches of biomass type, used for example in the
production of specialized foods. Extensive agricultural activity is one of the
main sources of competitive biomass, such as the production of cereals and
the cultivation of sugarcane for the production of sucrose, which collects and
concentrates large quantities of biomass residues in specific locations. Other
Preface v
sources of biomass that may be relevant to use as raw material are forest and
aquatic biomass, such as micro and macroalgae.
A high volume of biomass is already used as a raw material for a wide
range of industries, such as cellulosic pulp factories, preparation of heating
briquettes, oriented strand board (OSB), medium-density fiberboard (MDF),
and particle board (PB), for general use and furniture industry. Most of these
uses increase with population growth, which means that the demand for
terrestrial biomass will expand incoming years.
The ban on burning grain biomass residues, driven by law in many
countries, has led to a strong research effort for the production of liquid fuels
from biomass, namely ethanol—which due to its disinfectant properties is a
highly desirable end-product, as alcohol is now difficult to find due to the
spread of the Covid-19 virus worldwide. Also ethanol can be used as a fuel
in explosion motors.
In Europe, the addition of biodiesel to diesel was introduced in the early
years of this century as a way of reducing carbon particle emissions of the
predominant diesel engines. This policy, instead, has a negative effect on the
environment since its use is beneficial from emissions point of view but has
led to deforestation to expand oil seed crops production. The net result was
greater environmental damage in global terms, which was added to what
was already occurring due to the high demand for vegetable oils for the food
industry. Restrictions on the preparation of biodiesel with lipid coming from
distant sources and the favoring of the conversion of waste frying oils was
later tried as a corrective measure.
Meanwhile, the use of biomass-derived bioproducts, such as xylitol,
microcrystalline cellulose (MCC), carbon fiber-like materials, sugars,
antioxidants, etc., has begin to increase, which means that strategies must be
devised to efficiently process all available biomass with a view to its full use.
Other new sources of biomass such as micro- and macroalgae have started to
gain importance. Microalgae biomass is rich in constituents that can easily be
converted into biofuels and bioproducts, making it a complementary source
to terrestrial biomass.
This book deals with multiple attempts, developed over decades of work,
to use biomass as raw material for obtaining bioproducts and biofuels. Many
of the techniques described are new and have not yet been published. They
can be developed and converted into useful processes. The main objective of
the book is to offer new perspectives on the use of biomass, with a view to
contributing to the reduction of fossil carbon dioxide emissions through the
development of efficient biorefineries.
A work like this rests on the author’s dedication to this field of research
for many years, either through the teaching of subjects in the Biotechnology
Degree course, namely the Biotechnology and Biorefinery unit, or by the
orientation of graduate students’ of the master’s degree, in the scope of the
activities of the institution to which the author belongs—the Escola Superior
Agrária (ESAC) of the Polytechnic Institute of Coimbra (IPC).
vi Biomass, Bioproducts and Biofuels
The contribution of students with their effort to carry out experimental
research work for the preparation of their dissertations, has provided, over
the years, a valuable source of new research possibilities.
Recognition to the research center “Center for Natural Resources,
Environment and Society”, CERNAS (FCT), Environment and Society group,
from which financial support has always been provided for all activities. A
sincere thanks to everyone who contributed over the years to the content
of this book, in particular to Professor Lilia Santos and researcher Mariana
Assunção, authors of Chapter 7; and to all ACOI-Coimbra researchers,
Professor Fernando Simões of ISEC/IPC for his assistance in carrying
out mechanical tests on composite samples, to researchers Célia Ferreira
and Verónica Oliveira for their invaluable contribution, to the staff of the
Chemistry and Biochemistry Laboratory and Solos at ESAC, to Stephanie
Delgado, Sofia Benedettini, Yasheley van Es, Beatriz Sanchez, Luis Breda,
among many others.
June 2020 Coimbra, Portugal
Contents
Preface iv
1. Biomass Structure and Disassembling 1
1. Introduction 1
2. Biomass main components 4
2.1 Cellulose 4
2.1.1 Cellulose allomorphs 8
2.1.2 Amorphous cellulose 12
2.1.3 Gas diffusion and crystallinity studies 13
2.2 Structure of hemicellulose 15
2.2.1 Hemicellulose biosynthesis 17
2.2.2 Xylan 18
2.2.3 Xyloglucan 18
2.2.4 Mannan 19
2.3 Lignin 19
2.4 Minority compounds 22
3. Proposed structure for biomass 22
4. Disassembly of lignocellulosic materials 26
4.1 Physical treatments 26
4.2 Chemical treatments 26
4.2.1 The diluted acid method 27
4.2.2 Concentrated acid method 28
4.2.3 Use of enzymes 29
5. Biomass saccharification/fermentation process 31
5.1 Simultaneous saccharification and fermentation (SSF) 31
5.2 Separate hydrolysis and fermentation (SHF) 32
5.3 Consolidated Bioprocessing System (CBP) 32
6. Prospects for new technologies 33
7. References 34
2. New Uses for Hemicellulose 39
1. Introduction 39
2. Extraction of hemicellulose from biomass in pristine form 39
2.1 Medical and nutritional uses 41
2.2 Other uses 43
viii Biomass, Bioproducts and Biofuels
3. Hydrolytic extraction of hemicellulose 43
4. Fermentation of hemicellulose to ethanol 44
5. Adding a carbon to pentose sugars 45
6. Conversion of hemicellulose to xylitol 47
6.1 Food/nutritional use 47
6.2 Use in personal care 48
6.3 Medical uses 49
6.4 Xylitol obtention 49
6.4.1 Obtaining xylose from biomass 50
6.4.2 Methods of reducing xylose to xylitol 52
6.4.3 Reduction of xylose by chemical/electrochemical 53
methods
6.4.4 Reduction of xylose by biotechnological techniques 54
6.4.5 Finishing techniques in the production of xylitol 55
7. Conversion of hemicellulose to furfural 55
8. References 58
3. Biomass Delignification with Biomimetic Enzyme Systems 63
1. Introduction 63
2. The catalytic cycle of delignification 65
3. Biomimetic systems 68
3.1 Stability of porphyrin ligands to high valence oxo metal 69
complexes
3.2 Immobilization of metalloporphyrin 73
3.3 Preparation of porphyrins 74
3.3.1 Intermediates and by-products in the preparation of 75
porphyrins
3.3.2 Improved methods for preparing porphyrins 77
4. Preparation of a robust delignification catalyst 80
4.1 Preparation of 5,10,15,20-tetrakis 80
(2,6-dichloro-3-sulfatophenyl) porphyrin (TDCPPS)
4.2 Metalation of porphyrin 81
4.3 Construction of an experimental procedure for 82
biomass delignification
5. Analysis of results 85
5.1 Catalyst behavior in the delignification of wood samples 85
5.2 Delignification efficiency 86
5.3 Effect of temperature 88
5.4 Effect of pH value 88
5.5 Severity of conditions 89
5.6 Particle size effects of biomass 90
6. Final notes 90
7. References 91
Contents ix
4. Bioproducts Derived from Lignin Obtained from Micro- and 95
Nanocrystalline Cellulose Preparation
1. Introduction 95
2. Microcrystalline cellulose (MCC) 95
2.1 Preparation of paper pulp 96
2.2 Preparation of MCC from cellulose pulp 97
2.3 Preparation of MCC from straw residues 98
2.3.1 Alkaline thermal delignification 98
2.3.2 Biomass delignification in alkaline conditions 100
assisted by microwave heating
2.3.3 Removal of amorphous cellulose 101
3. Nanocellulose crystals (CNC) and nanocellulose fiber (CFN) 102
4. Antioxidant properties of lignin hydrolysates 104
5. References 109
5. Carbon Fiber Analogues by Fusion of Biomass Polymers 112
1. Introduction 112
2. Charcoals 113
2.1 Bio-oil 115
2.2 Syngas 115
3. From heterogeneous biomass to pure carbon holoforms 116
4. Carbon fiber 117
5. Hydrothermal carbonization (HTC process) 121
6. Carbonization at very low temperature (VLTC) 123
6.1 Very low temperature carbonization (VLTC) of wheat straw 127
6.1.1 Elementary composition 128
6.1.2 Electrical conductivity 129
6.1.3 GC-MS analysis of aqueous intermediate extracts 130
6.1.4 Measurement of the contact angle 131
6.1.5 Scanning electron microscope (SEM) analysis 131
6.1.6 Interpretation of observations 136
7. Preparation of carbonized wheat straw/epoxy resin 139
composites and study of their mechanical properties
8. References 141
6. The Methanol/Sulfuric Acid System for Cellulose 144
Saccharification
1. Introduction 144
2. Saccharification of biomass 145
3. The capacity of the sulfate anion to de-crystallize/hydrolyze 146
cellulose at low concentration in water at high temperature
4. Biomass saccharification with strong acids 147
4.1 Methods of acid impregnation 148
5. Mechanism of decrystallization of cellulose with strong acid 149
