Biofuels, production, application and development

250 Pages·2009·1.496 MB·English

by  A H Scragg

Biofuels
Production, Application and
Development
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Biofuels
Production, Application
and Development
A.H. Scragg
CABI is a trading name of CAB International
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Website: www.cabi.org
© A.H. Scragg 2009. All rights reserved. No part of this publication may be reproduced in
any form or by any means, electronically, mechanically, by photocopying, recording or
otherwise, without the prior permission of the copyright owners.
A catalogue record for this book is available from the British Library, London, UK.
Library of Congress Cataloging-in-Publication Data
Scragg, A.H. (Alan H.), 1943-
Biofuels, production, application and development/A.H. Scragg.
p. cm.
Includes bibliographical references and index.
ISBN 978–1–84593–592–4 (alk. paper)
1. Biomass energy. 2. Renewable energy sources. 3. Biomass energy--Environmental aspects.
4. Renewable energy sources--Environmental aspects. I. Title.
HD9502.5.B542S35 2009
333.95′39--dc22
2009012259
ISBN-13: 978 1 84593 592 4
Typeset by SPi, Pondicherry, India.
Printed and bound in the UK by Cambridge University Press, Cambridge.
The paper used for the text pages in this book is FSC certified. The FSC (Forest Stewardship
Council) is an international network to promote responsible management of the world’s
forests.
Contents
Preface vi
Acronyms, Abbreviations and Units viii
1 Energy and Fossil Fuel Use 1
2 Consequences of Burning Fossil Fuel 17
3 Mitigation of Global Warming 34
4 Biological Solid Fuels 62
5 Gaseous Biofuels 81
6 Liquid Biofuels to Replace Petrol 105
7 Liquid Biofuels to Replace Diesel 136
8 The Benefi ts and Defi ciencies of Biofuels 167
References 213
Index 230
v
Preface
Biofuels are energy sources derived from biological materials, which distinguishes
them from other non-fossil fuel energy sources such as wind and wave energy. Biofu-
els can be solid, liquid or gaseous, and all three forms of energy are sustainable and
renewable because they are produced from plants and animals, and therefore can be
replaced in a short time span. In contrast, fossil fuels have taken from 10 to 100
million years to produce and what we are burning is ancient solar energy. In addition,
the energy derived from plant material should be intrinsically carbon-neutral, as the
carbon accumulated in the plants by the fixation of carbon dioxide in photosynthesis
is released when the material is burnt.
At present it is clear that the supply of fossil fuels is finite and a time can be envis-
aged when the supplies of fossil fuels become scarce or even run out. Also the burning
of fossil fuels releases additional carbon dioxide into the atmosphere over and above
that released in the normal carbon cycle. The accumulation of carbon dioxide in the
atmosphere appears to be the major cause of global warming. The consensus suggests
that the long-term effects of global warming will be severe, with drastic changes in
climate and sea levels. At the same time, modern society requires increasing amounts
of energy, most of which is obtained from fossil fuels. Thus, mankind is almost totally
reliant on fossil fuels to provide electricity, heating/cooling and transport fuels. This
reliance can be seen in the effects on countries when oil supplies are interrupted by
wars, embargos and strikes. In 2008, the world suffered from rapid rises in oil prices
which affected the price of many commodities.
Alternative energy supplies are needed, therefore, to provide both power and fuel
for transport. The possible energy sources available are very diverse and include
hydroelectric, nuclear, wind, biological materials and many others. Whatever energy
source is used, it should be sustainable and as carbon-neutral as possible. Biofuels
encompass the contribution that biological materials may make to energy supply and
in particular liquid fuels for transport. Solid biofuels, principally biomass, have been
used for thousands of years to provide heat and for cooking, and are used at present
to generate electricity and in combined heat and power systems. The gaseous biofuel
methane is produced by the anaerobic digestion of sewage, in landfills and is also
used for electricity generation and for heat and power systems. It is the liquid biofuels
that will be used to replace the fossil fuels petrol and diesel, and they have attracted
much attention. At present liquid biofuels can be divided into first-, second- and
third-generation biofuels. The first-generation biofuels consist of ethanol which is
used to either supplement or replace petrol and biodiesel, as a replacement for diesel.
Ethanol is produced from either sugar or starch which is extracted from crops such
as sugarcane, sugarbeet, wheat and maize and can save 30–80% of greenhouse
gas emissions when compared with petrol. Biodiesel is produced from plant oils
vi
and animal fats and can save between 44 and 70% greenhouse gases compared with
diesel. At first glance this situation appears ideal but there are problems with first-
generation biofuel production and supply. One problem is the amount of energy that
is used to produce and convert the crops into biofuels. Another problem is the
amount of biofuels needed to replace fossil transport fuels. In the UK, in 2006 19,918
million t of petrol and 23,989 million t of diesel were used, that is a total of 43,907
million t. To supply this tonnage is a formidable task. For example, to supply the
diesel required in the UK using the oil-seed crop rapeseed, 113% of the agricultural
land would be needed. This is clearly not possible and even at modest levels of diesel
replacement the biofuel crops would compete with food crops. It is this feature that
has brought forward many objections to biofuels, and they have been blamed for
some food shortages; however, in reality food prices are influenced by a number of
factors. Converting sensitive lands such as rainforests to grow biofuel crops has also
engendered justifiable resistance. In addition, crops such as wheat and other starch-
containing crops require considerable processing and energy input, and when inves-
tigated by life-cycle analysis show only marginal gains in energy.
However, the resistance to biofuels need not be the case as the first-generation
biofuels bioethanol and biodiesel were only intended to be used as a 5% addition to
fossil fuels to comply with the EU directives, and to show that fossil fuels could be
replaced. It was clear that any more would compromise food crops. It is the second-
and third-generation biofuels that should replace the bulk of the transport fossil fuels.
The second-generation biofuels are ethanol, produced directly from lignocellulose,
and the gasification of lignocellulose and waste organic materials producing petrol,
diesel, methanol and dimethyl ether. Lignocellulose and organic wastes are available
in large quantities and their use does not compromise food crops. Lignocellulose is
often the discarded portion of food crops such as straw. The third-generation biofuels
are hydrogen, produced either by the gasification of lignocellulose or directly by
microalgae, and biodiesel produced from oil accumulated by microalgae. These
second- and third-generation biofuels should not compromise food crops, but to
bring these fuels into production will require both research and investment. To stop
the use of land areas, such as the rainforests, for first-generation biofuels will prob-
ably require legislation.
Preface vii
Acronyms, Abbreviations and Units
ACC acetyl CoA carboxylase
AGFB atmospheric gasifier fluidized bed
AFC alkaline fuel cell
ATP adenosine triphosphate
Bar measurement of pressure = 100,000 pascal
bbl barrel of oil = 159 litres
BERR Business Enterprise and Regulatory Reform Department
BHT butylated hydroxytoluene
BIGCC biomass integrated gasifier combined cycle
BRI Bioengineering Resources Inc.
BSFC brake specific fuel consumption
BTDC before top dead centre
Bt Bacillus thuringiensis
BTL biomass to liquid
Btu British thermal unit
BOCLE ball on cylinder lubrication evaluator
CA crankshaft angle
CAP common agricultural policy (EU)
CBG compressed biogas
CCGT combined cycle gas turbine
CC & S carbon dioxide capture and storage
CDM clean development mechanism
CFC chlorofluorocarbons
CHP combined heat and power
CNG compressed natural gas
COP Conference of the Parties
cP centipoise (measure of viscosity)
CRGT chemically recuperated gas turbine
cSt centistoke (measure of viscosity)
Defra Department of Food and Agriculture
DC direct current
DDGS distiller’s dried grain with solubles
DICI direct injection compression ignition
DISI direct injection spark ignition
DME dimethyl ether
DMFC direct methanol fuel cell
DNA deoxyribonucleic acid
Dti Department of Trade and Industry
viii
EBB European Biodiesel Board
EGR exhaust gases recycle
EIA Energy Information Administration
EJ exajoules (1018)
EOR enhanced oil recovery
EPA Environmental Protection Agency
ETBE ethyl tertiary butyl ether
EU European Union
EU ETS European Union Emissions Trading Scheme
EU 25 European Union consisting of 25 countries
E85 petrol containing 85% ethanol
E95 petrol containing 95% ethanol
FAME fatty acid methyl esters
FT Fischer–Tropsch process
FT diesel diesel produced by the Fischer–Tropsch process
FTIR Fourier transformed infrared
FT petrol petrol produced by the Fischer–Tropsch process
GHG greenhouse gases
GLC gas liquid chromatography
GTL gas to liquid
Gtoe gigatonne oil equivalent
ha hectares = 10,000 m2
HC hydrocarbons
HFCS high fructose corn syrup
HFRR high frequency reciprocating rig
HGCA Home Grown Cereals Association
ICE internal combustion engine
IEA International Energy Agency
IEE Institute of Electrical Engineers
IFPRI International Food Policy Research Institute
IGCC integrated gasification and combined cycle
IOR increased oil recovery
IPCC International Panel on Climate Change
J joules
JRC Joint Research Centre
kW kilowatt
kWh kilowatt hour
kWht kilowatt hour heat
LCA life-cycle analysis
LHV lower heating value (heat of condensation of water not included)
l litre
LNG liquefied natural gas
LPG liquefied petroleum gases
LTFT low temperature filterability
LULUCF land use, land use change and forestry
MCFC molten carbonate fuel cell
Mha megahectare
Acronyms, Abbreviations and Units ix