Future energy improved sustainable and clean options for our planet

Eight new chapters have been introduced,including topics such as • small nuclear reactors; • electric vehicle revolution; • energy storage, energy from biomass; • solar energy beamed fro

Future Energy Improved, Sustainable and Clean Options for our Planet

Third Edition

Edited by Trevor M Letcher University of Kwazulu-Natal Durban, Kwazulunatal, South Africa Laurel House, Stratton on the Fosse

United Kingdom

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To my grandchildren, Amy and Finn Taylor

Amarjeet Bassi Department of Chemical and Biochemical Engineering, University

of Western Ontario, London, ON, Canada

Vitezslav Benda Czech Technical University in Prague, Faculty of ElectricalEngineering, Prague, Czechia; email: benda@fel.cvut.cz

Hasan Berkem Sonder Cardiff University, Cardiff, United Kingdom

Subhamoy Bhattacharya Surrey Advanced Geotechnical Engineering (SAGE)Laboratory, University of Surrey, Guildford, United Kingdom; email:S.Bhattacharya@surrey.ac.uk

Jeremy Boak Retired, Oklahoma Geological Survey, Mewbourne College of Earthand Energy, University of Oklahoma, Norman, OK, United States; email:jeremyboak@comcast.net

Hans Böhm Energy Institute at the Johannes Kepler University Linz, Linz, Austria

Ray Boswell National Energy Technology Laboratory, Pittsburgh, PA, United States;email: ray.boswell@netl.doe.gov

Christian Breyer Department of Electrical Engineering, LUT University,Lappeenranta, Finland; email: christian.breyer@lut.fi

Carlos Henrique de Brito Cruz São Paulo Research Foundation (FAPESP), SãoPaulo, SP, Brazil; Physics Institute, University of Campinas (UNICAMP), Campinas, SP,Brazil; email: brito@fapesp.br

Liana Cipcigan Cardiff University, Cardiff, United Kingdom

xxi

Timothy Collett United States Geological Survey, Denver, CO, United States

Luís Augusto Barbosa Cortez Center for Energy Planning, University ofCampinas (UNICAMP), Campinas, SP, Brazil

Andrew Crossland Advance Further Energy Ltd, Retford and Infratec, Wellington,New Zealand

Arno de Klerk Department of Chemical and Materials Engineering, University ofAlberta, Edmonton, AB, Canada; email: deklerk@ualberta.ca

Christian Doetsch Fraunhofer-Institut für Umwelt, Sicherheits- und EnergietechnikUMSICHT, Oberhausen, Germany; email: christian.doetsch@umsicht.fraunhofer.de

Steve Hancock XtremeWell Engineering Inc., Calgary, Canada

Nawshad.Haque@csiro.au

Dennis R Hardy NOVA Research Inc., Alexandria, VA, United States

xxii List of Contributors

Yulin Hu Department of Chemical and Biochemical Engineering, University ofWestern Ontario, London, ON, Canada

Paul Jaffe United States Naval Research Laboratory, Washington, DC, United States;email: paul.jaffe@nrl.navy.mil

Kejun Jiang Energy System Analysis Research Center, Energy Research Institute,Beijing, China; email: kjiang@eri.org.cn

Richard.kemp@ukaea.uk

Ånund Killingtveit Department of Civil and Environmental Engineering,Norwegian University of Science and Technology, Trondheim, Norway; email:aanundk@outlook.com

Robert Kleinberg Columbia University Center on Global Energy Policy, New York,

NY, United States; Boston University Institute for Sustainable Energy, Boston, MA,United States

Vinoj Kurian Department of Chemical and Materials Engineering, University ofAlberta, Edmonton, AB, Canada

Sung-Rock Lee KIGAM, Seoul, South Korea

Trevor M Letcher Department of Chemistry, University of KwaZulu-Natal,Durban, KwaZulu-Natal, South Africa; Laurel House, Stratton on the Fosse, UnitedKingdom; email: trevor@letcher.eclipse.co.uk

Johannes Lindorfer Energy Institute at the Johannes Kepler University Linz, Linz,Austria; email: lindorfer@energieinstitut-linz.at

Francis Livens Dalton Nuclear Institute, Manchester University, Manchester, UnitedKingdom

Giorgio Locatelli University of Leeds, School of Civil Engineering, Leeds, Yorkshire,United Kingdom; email: g.locatelli@leeds.ac.uk

Stephan Lux Fraunhofer Institute for Solar Energy Systems ISE, Department ofElectrical Energy Storage, Freiburg, Germany

Maria Mastalerz Indiana Geological and Water Survey, Indiana University,Bloomington, IN, United States; email: mmastale@indiana.edu

List of Contributors xxiii

Mary Helen McCay National Centre for Hydrogen Research, Florida Institute ofTechnology, Melbourne, FL, United States; email: mmccay@fit.edu

Benito Mignacca University of Leeds, School of Civil Engineering, Leeds, Yorkshire,United Kingdom

Pegah Mirzania School of the Built Environment and Architecture, London SouthBank University, London, United Kingdom

University, Melbourne, VIC, Australia; email: gavin.mudd@rmit.edu.au

Stalin Munoz-Vaca School of Engineering, Newcastle University, Newcastle-uponTyne, United Kingdom

Mahendra Pratap Directorate General of Hydrocarbons, Delhi, India

University of Alberta, Edmonton, AB, Canada

xxiv List of Contributors

Daniel Cenk Rosenfeld Energy Institute at the Johannes Kepler University Linz,Linz, Austria

Shahin Sha fiee Department of Mechanical Engineering, Prairie View A&MUniversity, Prairie View, TX, United States

Gláucia Mendes Souza Institute of Chemistry, University of São Paulo (USP), SP,Brazil

Daniel A Vallero Department of Civil and Environmental Engineering, DukeUniversity, Durham, NC, United States; email: dav1@duke.edu

Matthias Vetter Fraunhofer Institute for Solar Energy Systems ISE, Department ofElectrical Energy Storage, Freiburg, Germany; email: matthias.vetter@ise.fraunhofer.de

Nathan Vimalan Surrey Advanced Geotechnical Engineering (SAGE) Laboratory,University of Surrey, Guildford, United Kingdom

Neal Wade School of Engineering, Newcastle University, Newcastle-upon Tyne,United Kingdom

Sara Walker School of Engineering, Newcastle University, Newcastle-upon Tyne,United Kingdom

Jihong Wang University of Warwick, Coventry, United Kingdom

Heather D Willauer Naval Research Laboratory, Materials Science& TechnologyDivision, Washington, DC, United States; email: heather.willauer@nrl.navy.mil

Johannes Wüllner Fraunhofer Institute for Solar Energy Systems ISE, Department

of Electrical Energy Storage, Freiburg, Germany

Chunbao (Charles) Xu Department of Chemical and Biochemical Engineering,University of Western Ontario, London, ON, Canada; email: cxu6@uwo.ca

Koji Yamamoto Japan Oil, Gas, and Metals National Corporation, Tokyo, Japan

List of Contributors xxv

This third edition of Future Energy is a response to the interest shown in the first and secondeditions and to the new developments in the field Eight new chapters have been introduced,including topics such as

• small nuclear reactors;

• electric vehicle revolution;

• energy storage, energy from biomass;

• solar energy beamed from space;

• life-cycle assessment of renewables;

• integration of intermittent renewable energy;

• problems with metals and elements needed to support renewable energy; and

• a global overview of future energy

The new book is divided into nine sections:

• Introduction with a focus on carbon dioxide pollution;

• Fossil fuels (energy sources);

• Nuclear power (energy sources);

• Transport energy (energy sources);

• Energy storage;

• Renewable energy (energy sources);

• New possible energy options;

• Sustainabilty;

• The current situation and the future

Discussions on the energy situation in countries around the world have been restricted

to China as it is the most rapidly developing superpower, and it produces more energy thanany other country on Earth China also produces more carbon dioxide than any other country.The book looks at all types of energy that may be used in the future, including thesustainable types such as solar, wind, tidal, and wave energy Fossil fuel in all its forms, fromcoal, oil, shale oil, methane gas, and methane hydrates, occupies a prominent place in thisbook as these energy sources will be with us for many decades before we have expanded anddeveloped renewable energy forms, built new nuclear fission plants, or possibly evendeveloped new types of energy such as nuclear fusion and space solar power in whichorbiting solar panels collect energy from the sun and beam it back down to Earth using lasers

or microwaves

This book, like the previous editions, has been produced in order to allow the reader tohave a reasonable, logical, and correct understanding and insight into our future energyoptions The final decision as to which energy form should be developed in a country orregion must take into account many factors including sustainability; the general safety and

xxvii

health of the general public; the overall energy requirements of society; the geographicalposition of each region; and above all, the alarming rise in atmospheric carbon dioxide overthe past 50 years, which threatens to change the world’s future climate through globalwarming.

The first edition of this book had its origins in the committee meetings of theInternational Association of Chemical Thermodynamics1, an organization affiliated to theInternational Union of Pure and Applied Chemistry (IUPAC2) IUPAC’s adherence tothe International System of Quantities is reflected in the book with the use of SI unitsthroughout Flexibility and accommodation are ensured for various constituencies byincluding alternate non-SI units that may be more familiar to specific areas The index no-tation is used to remove any ambiguities, for example, billion and trillion are written as 109and 1012, respectively To further remove any ambiguities, the concept of the quantity cal-culus is used It is based on the equation: physical quantity¼ number  unit To give anexample: power¼ 200 W and hence 200 ¼ power/W This is of particular importance in theheadings of tables and the axis labels of graphs One can only plot a number on a graph, andthe axis label reflects this reality

This volume is unique in the genre of books of similar or related titles currently on sale

in that each chapter of Future Energy has been written by an expert scientist or engineer,working in the field Authors have been chosen for their expertise in their respective fields andcome from nineteen countries: Austria, Australia, Brazil, Canada, China, Czech Republic,England, Finland, Germany, Greece, India, Italy, the Netherlands, New Zealand, Norway,Poland, South Africa, the United States, and Wales

A vital concern of future energy options is what is to be done when it appears thatpoliticians misunderstand or ignore and corporations overlook the realities of finite fuelsources and our changing climate? The solution lies in sound scientific data and education Aseducators we believe that only a sustained grassroots movement to educate citizens, politi-cians, and corporate leaders of the world has any hope of success This book is part of thateducation process It presents a nonpolitical and unemotional set of energy options forreaders to consider and arrive at sensible solutions to the problems facing the world today

We hope that not only students, teachers, professors, and researchers of new energy but alsopoliticians, government decision makers, captains of industry, corporate leaders, journalists,editors, and all interested people will read the book, take heed of its contents, and absorb itsunderlying message

I wish to thank all of the seventy-one authors and coauthors for their cooperation, help,and especially for writing their chapters It has been a pleasure working with each and everyone of our authors I thank my wife, Valerie, for all the help she has given me over these longmonths of putting the book together I also wish to thank the staff at Elsevier for their help ingetting this volume together

Trevor M LetcherStratton on the Fosse

Introduction With a Focus on

Atmospheric Carbon Dioxide and Climate Change

Trevor M Letcher1,2

1 DEPARTMENT OF CHEMISTRY, UNIVERSITY OF NATAL, DURBAN, NATAL, SOUTH AFRICA; 2 LAUREL HOUSE, STRATTON ON THE FOSSE, UNITED KINGDOM

KWAZULU-1.1 Introduction

In this introductory chapter, we look at

the driving forces behind the need to consider new forms of energy;

the looming problem of global warming and climate change;

the options for electricity generation and for transport fuel;

the energy situation today;

thermodynamics and sustainable energy,

why solar energy is so very important and

the big question: how can we reduce the stranglehold that fossil fuels have on oureconomy and lives?

The energy choices we make will depend on where we live, the size of our population,and also on the types of energy sources that are available For example, people in Icelandwill consider expanding their renewable sources of geothermal and wind energy,whereas those living in South Africa will certainly consider solar energy, among manyother possibilities

At the same time, account should be taken of the polluting nature of the energysource and it is our responsibility to assure that whatever energy source we utilize, we do

it in an environmentally sound manner And if one cannot steer totally away from fossilfuels, the resultant carbon dioxide and other pollutants should be either sequestered andstored or utilized and not emitted to the atmosphere

© 2020 Elsevier Ltd All rights reserved.

1.2 Why is it important to consider our future energy

options?

1.2.1 Society ’s needs

As the population of the world increases and as developing countries advance, so energyneeds increase The world’s population is increasingeit was 3 billion (3  109) in 1960, 6billion in 2000, 7.6 billion in July 2018, and is expected to reach between 9 billion and 10billion by 2050 The annual rate of population growth reached a peak of 2.2% a1(where

“a” refers to annum) in 1963, but by 2018, it had declined to 1.09% a1[1] The lation is growing at a rate of 83 million people per annum

popu-The expected growth rate in energy demand over the next 20 years is greater than thegrowth rate of the population and this is largely due to increased electricity production

by developing nations The electricity generation is expected to increase from25.1 1015Wh in 2017 to 29.2 1015Wh in 2030, which is equivalent to an averageenergy increase of 1.3% a1 [2] This additional energy supply must be found andpreferably in the form of renewable energy

1.2.2 The need for a sustainable, safe, and nonpolluting energy

source

The present world electrical energy generation is dominated by fossil fuel (seeTable 1.1),which unfortunately is not sustainable in the long term Furthermore, the combustion offossil fuel is a major cause of air pollution The picture is confusing because we are living in

an age with an apparent glut of fossil fuel Coal and conventional gas continue to be tively easy to extract Unconventional gas has experienced a recent boom because of hor-izontal drilling and hydraulic fracturing techniques At the same time, oil is becoming moreand more difficult to extract in spite of new drilling techniques Somehow the strangleholdmust be broken and renewable energy is our only option Even if we could replace fossil fuelfor electricity generation, there is another problem, and that is the need for a sustainable,safe, and nonpolluting liquid fuel for air travel and vehicular transport This is of particularconcern as the transport and production of oil can create serious environmental problems,and names such as Exxon Valdez (1989), Torrey Canyon (1967), Niger Delta (1970e2000),and Deepwater Horizon (2010) have become bywords for environmental disaster

rela-Table 1.1 Total global electrical energy generation percentages for 2015[2]

The total global energy consumption (Table 1.2) paints a similar picture to the globalelectricity generation with the domination of fossil fuel Furthermore, the spread ofenergy types involved has changed little over the past 7 years[3].

With the recent development of shale gas reserves, especially in the United States,there has been a shift in thinking about exploiting fossil fuel The argument is thatburning natural gas (largely methane) is better for the planet than burning coal This istrue because the amount of CO2produced from burning CH4, per unit energy (50 g MJ1)

is less than it is for coal (92 g MJ1) and moreover coal burning produces particulates.But burning CH4still produces CO2:

CH4þ 2O2¼ CO2þ 2H2O

and contributes to climate change

Replacing fossil fuels is going to be a mammoth task At present, energy sources otherthan fossil fuels make up less than 20% of global energy consumption (seeTable 1.3).These include nuclear fission, hydroelectricity, biomass, and renewable sources, such aswind, solar, geothermal

Replacing gasoline, diesel, and aviation fossil fuels is going to be a particularlydifficult task The reality is that we do not yet have an alternative, viable, and convenientenergy source for transport The importance of transport fuel and the magnitude of theproblem are highlighted inTable 1.3, which shows that of all the energy used on Earthtoday, transport makes up 31%

Attempts at replacing gasoline in transport with a renewable fuel derived frombiomass (sugar cane and corn) have had some success but the overall contribution hasbeen relatively small In 2017, biofuels contributed only 4% of the world’s transport fuel,with the ethanol production of the United States and Brazil being the major contributors

[5] A bright light on the horizon is the very recent development of batteries and electricmotors for vehicular transport However, it would only make a difference if the energy torecharge the batteries is made from renewable energy It does not solve the ever-growingneed for aviation fuel

Perhaps the most important driving force in finding new sustainable energy sources islinked to the specter of climate change Climate change and global warming are

Table 1.2 Total global energy consumption percentages for 2017[3]

Chapter 1
Introduction With a Focus on Atmospheric Carbon Dioxide 5

considered to be a result of anthropogenic greenhouse gases with CO2being the mostimportant More details of the relationship of CO2levels and global warming are given in

Section 1.2of this chapter

The level of atmospheric carbon dioxide has been steadily increasing It was 280 partsper million (280 106) (ppm) in preindustrial times, about 315 ppm in 1957 and on 10May 2013, the atmospheric levels of carbon dioxide reached a new high of 400 ppm[6] Itwas 415 ppm on 2 May 2019 at Mauna Loa Observatory[7]

For a few decades now, world leaders and environmentalists have been talking aboutlimiting the average global temperature rise to no more than 2C higher than prein-dustrial temperatures At the rate at which CO2is presently being emitted into the at-mosphere, (6 Gt a1) and at the rate that the average global temperature is increasing(0.2C per decade), this will be passed in less than 60 years from now The rationalebehind this 2C per year increase is that we could possibly live with this level of tem-perature rise, but any further increase might tip the balance, plunging the world intoclimatic feedback loops which will be difficult to stop The predictions of catastrophicdroughts and floods, rising sea levels, melting ice caps and ice sheets, wholesalemigration of populations, loss of biodiversity in the insect, animal and plant kingdoms,serious drop in food production, and overcrowding in cities, will probably accompany atemperature rise of greater than 2C I say “probably” because the truth is that we just donot know It might be that 1.5C increase is too much or that with 2C the changes will benot as severe as predicted The fact is that the current average global temperature isalready 1.0C higher than preindustrial temperatures These predictions should beenough to galvanize governments and societies into finding alternative energy sources

[8,9] The two main feedback loops are the melting of the polar ice caps and the melting

of the permafrost In the first case, the white polar ice caps have for thousands of yearsreflected solar energy back into space A decrease of polar ice results in a greater area ofseawater being exposed to the incoming sunlight which in turn heats the water andraises the overall global temperature In the second case, the melting of the permafrostwill release trapped methane gas from methane hydrates, buried under the permafrost

As methane is 25 time more potent a GHG than is CO2, the result will be a further crease in global temperature

in-The question one may ask is “Why can’t we convert CO2into useful products such asplastics?” The problem with CO2is that it is not easily transformed into other chemicals

It is the most oxidized form of carbon and as a result is thermodynamically very stable

Table 1.3 Energy usage as a percentage[4]

and hence any chemical reaction involving CO2will require a significant input of energy.

In short, it has a large and negative Gibbs energy of formation Perhaps, the only viableway to get rid of it is to collect it and store it

Electricity production is responsible for producing the largest amount of CO2sion (28%) as seen inTable 1.4 It is perhaps with the production of electricity that weshould focus our attention for new sustainable energy sources, free of CO2 pollution.Transport is another major problem as it also produces 28% of all anthropogenic CO2.There are also some other processes which emit significant amounts of CO2that will bevery difficult if not impossible to replace Cement manufacture is one of them; it isresponsible for at least 5% of all anthropogenic CO2[10] It is the heating process (usuallycoal or gas) together with the breakdown of CaCO3that is responsible for those emis-sions during cement manufacturing:

emis-CaCO3¼ CaO þ CO2

1.3 Atmospheric pollution and climate change

The scientific evidence that climate change and global warming are largely due to therise of carbon dioxide in the atmosphere is overwhelming Every science society andevery research organization working in the field of climate change in the world acceptsthe view that global warming is a reality, that it is largely a result of human interventionand that increasing CO2 is perhaps the most important cause of global warming andclimate change Most world governments have now accepted the assessment of theUnited Nations Framework Convention on Climate Change (UNFCCC), defined at theCancun 2010 meeting, that a 2C rise in global mean temperature above the preindus-trial level must be the maximum limit With regard to having a likely chance of meetingthe 2C objective, studies generally indicate the need for global emissions to peak before

2020, with substantial declines in emissions thereafter

Despite its relatively low overall concentration (0.04% by volume or by molecules ofthe atmosphere), CO2is a very important component of the Earth’s atmosphere because

it absorbs infrared radiation at wavelengths of 4.26mm (asymmetric stretching tional mode) and 14.99mm (bending vibrational mode) This infrared radiation is the

vibra-Table 1.4 Global greenhouse gas emission from economic sector (CO2and CH4), in2016

Agriculture (livestock, rice fields soils, forestry land clearing, fires, peat) 9

By https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions.

Chapter 1
Introduction With a Focus on Atmospheric Carbon Dioxide 7

radiation from the Earth reflected back into space after the Earth has been heated by thesun’s energy In this way, CO2is responsible for much of the greenhouse effect that keepsour planet relatively warm (which is good) but also for global warming and climatechange if the CO2concentration rises significantly (which is bad)[12].Without the CO2inthe atmosphere, temperatures on Earth would plummet and life on Earth, would be verydifferent to what it is today.

Water vapor is an even more effective greenhouse gas than CO2 Like CO2 it alsoabsorbs infrared radiation, and in this case, in the range of 12e17 mm Furthermore itsconcentration is much higher than that of CO2(of the order of a 100 times higher), and

H2O probably contributes about 60% of the global warming effect The amount of watervapor in the atmosphere is controlled by the temperature An increase in the CO2concentration of the atmosphere increases the global temperature only slightly but thatchange is enough to increase the amount of water vapor in the air, through evaporationfrom the oceans This increase in water vapor in the air results in a large increase in thegreenhouse effect and the result is global warming It is this effect that has the greatestinfluence on global temperature In a sense, paradoxically, the concentration of CO2acts

as a regulator for the amount of water vapor in the atmosphere and is thus the mining factor in the equilibrium temperature of the Earth

deter-Since the 1950s, the CO2levels in the atmosphere have risen by almost 50%, causing

an increase in the blanketing effect, which in turn has resulted in an increase of 1C inglobal temperature[13] Evidence that the CO2is from human activities is based on therelative ratios of carbon isotopes The relative amount of13C in the atmosphere has beendeclining and this is due to the fact that the ratio of13C in fossil fuel derived CO2is muchlower than in CO2produced from present day decaying plants[14]

Compelling evidence that the increase in CO2 in the atmosphere is the most likelycause of global warming is seen in the superimposed graphs of CO2concentration in theatmosphere and global average temperature as a function of time over the past 130 years

An example of this is to be found in Ref.[15]

Most governments accept the 2C degree moratorium, and that the warming of theEarth is roughly proportional to the amount of CO2 emitted globally, but very little isbeing done to achieve this target It is possible that even this 2C may not be enough toavoid the disastrous and damaging impacts of climate change During the period2000e09, CO2levels have increased at a rate of about 2 ppm a1(2 parts per million perannum) and over the past 5 years this rate has increased to almost 3 ppm a1 Thisdramatic increase is largely attributed to anthropogenic sources

It is not only CO2and H2O that is the responsible for global warming There are otheranthropogenic greenhouse gases such as methane and chlorinated hydrocarbons, tomention two Some are more damaging and more effective as greenhouse gases, permolecule, but at the moment their concentrations are very much lower than that of CO2.The properties of CO2and some other GHGs are given inTable 1.5 [16]

Some of these properties have been calculated by scientists from spectroscopicmeasurements, reaction kinetics and photochemical studies in the laboratory Carbon

8 Future Energy

dioxide has the largest value for radiative forcing although its global warming potential,which is an indication of the potential of each gas for warming the atmosphere and theplanet, is much lower than the values for methane, nitrous oxide or the fluorinatedhydrocarbons However the high concentration of CO2 and its long life in the atmo-sphere makes it the largest contributor to the overall greenhouse effect.

In spite of the evidence presented inTable 1.5, and the evidence of the synchronized

CO2concentration and the global temperature graphs, there has been much debate as towhether our present global warming and climate change could in fact be due to othereffects such as: the variation in the sun’s energy; volcanic activity; changes in the Earth’sorbital characteristics including the Malankovitch cycles; and cosmic ray effects Thefirst of these, relating to possible variations in solar radiation, has been investigated bymany scientists and all agree that this is not the main cause of our present situation[17].Volcanic activity on earth had in the past resulted in short-lived climate changes, butexperts working in the field state that this could not possibly be responsible for ourpresent climate change[18] The Earth’s wobble as it moves around the Sun is anotherpossible contender for inducing climate change However, Lourens and Truter, scientistsworking in this area, have stated that from all the evidence it is most likely that theclimate change that we are currently experiencing is not due to variations of the Earth’sorbital movements[19] Solar activity and cosmic ray bombardment from space is yetanother possible cause of climate change but expert L I Dorman feels that these effectscannot possibly be responsible for our present global warming[20]

Recent work by Macott et al has prompted these researchers to write: “The Earth’sclimate is complex and responds to multiple forcings, including CO2 and solar insola-tion Both of those have changed very slowly over the past 11,000 years But in the last

100 years, the increase in CO2 through increased emissions from human activities hasbeen significant It is the only variable that can best explain the rapid increase in globaltemperature”[21]

It is, however, not possible to obtain an absolute proof that it is CO2that is largelyresponsible for global warming, because we cannot do the definitive experiment; that is

we cannot suddenly stop using fossil fuels And even if we could, it would take at least

Table 1.5 Properties of some greenhouse gases (GHGs) related to Global Warming

Most of the data has been taken from Table 1.2 in Tuckett, R.P.,(2016).The Role of Atmospheric Gases in Global Warming in Climate Change, Observed Impacts on Planet Earth, second ed T.M Letcher (Eds.), pp 375e396, Elsevier, Oxford.

Chapter 1
Introduction With a Focus on Atmospheric Carbon Dioxide 9

100 years to obtain a definitive conclusion because of the long life CO2 has in theatmosphere.

Superimposed on the scenario of global warming, is the effect of global dimming

[17].This effect was especially noticeable between the 1950 and 1980s when it was foundthat the Sun’s energy reaching places on the surface of the Earth was less than in pre-vious years - the reduction being of the order of a few percent It was attributed toaerosol formation and particulates in the atmosphere resulting from the burning of coaland other hydrocarbons These particles reflect the Sun’s rays back into space resulting

in a dimming of the solar radiation It was indeed partially compensating for by globalwarming Since that time, these particulates and pollutants have been reduced by staticprecipitators in chimney stacks with the result that in the 1990s and early 2000s, therewas a brightening effect accompanied by a rise in global average temperature (seeFigure 6 in Ref.[15])

A recent study on the effects of CFCs on global warming by Qing-Bin Lu, of theUniversity of Waterloo, has confirmed that these compounds are serious contenders forthe most potent greenhouse gas Their potency (seeTable 1.5) as GHGs is extremely high(long lifetime and large radiative efficiency), and in spite of their present low concen-trations in the atmosphere should be banned from production as their build-up in theatmosphere could be very damaging to future generations[22]

Before the Industrial Revolution, the natural production of CO2 on Earth was inequilibrium with the CO2 dissolving in the oceans, soils and taken up in plants As aconsequence, the atmospheric CO2concentration remained more or less constant Withthe recent anthropogenic production of CO2in significant quantities, this equilibrium nolonger holds It has been estimated that today about 45% of newly released CO2dissolves

in the oceans (CO2is a soluble gas) contributing to the acidification of the oceans, butthe remainder builds up in the atmosphere [23] As long as we keep emitting CO2 inincreasing quantities into the atmosphere, this concentration will rise Furthermore,evidence shows that much of the CO2entering the atmosphere now remains there for avery long time (between 50 and 200 years)

1.4 What are our options for electricity generation?

Electricity generation is the largest user of energy in the world, and currently mostelectricity is produced from natural gas or coal (seeTables 1.1 and 1.3) Finding energysources that do not involve fossil fuels cannot happen overnight There has to be aphasing in of new energy sources Therefore, we must have well designed short, medium,and long term plans to ensure an adequate supply of energy and at the same timeconsider ways to limit atmospheric CO2emissions and prevent serious global warming

In the short term, natural gas will have to be considered as a stop gap to replace coal

in power stations (see Chapters 2e6) together with a concerted effort to developrenewable sources (Chapters 15e21), build new nuclear power stations (Chapters 7 and

10 Future Energy

8) and begin carbon capture and storage schemes (Chapter 31) The latter will involveinjecting CO2 to sequestering sites In the medium term, we could invest in nuclearfission (see Chapters 7 and 8) to sustain our societies before the long term investmentsinto renewable energy take over This we may hope will be in parallel with nuclear fusion(see Chapter 25).

The following chapters will highlight most of the possible energy options and you, thereader, can add your own short, medium and long term solutions to this major problem.There are other possible options (not included in this book), such as nuclear fusion usingboron and hydrogen (forming helium) Theoretically, this would be ideal as an energysource as the reaction produces no neutrons But there are even more difficulties withthis option than there are with hydrogen fusion; this is largely due to the problem ofgiving the proton enough energy to break through the coulomb barrier of the boronnucleus (it has three positive charges) In hydrogen fusion, the coulomb barrier is farsmaller because the hydrogen has only one positive charge

Another energy option, viz space solar power, has been included for the first time(Chapter 24) This type of energy source involves spreading a vast array of collectors ofthe order of 10 km2, high above the Earth and beaming the energy back to Earth bymicrowave or by laser The major drawback with this technique is the cost of sendinglarge and heavy pieces of equipment into space Its advantage is that freed fromterrestrial limitations of clouds, bad weather, and night time darkness, the space col-lectors could harvest sunlight essentially 24 h a day

Other issues discussed in the following chapters, which are related to energy optionsfor generating electricity include: Energy in China (Chapter 32); environmental impacts(Chapter 27); energy efficient technologies (Chapter 28); the development and viability ofenergy storage (Chapters 12e14) and of carbon dioxide capture and sequestration(Chapter 31)

1.5 What are our options for transport fuel?

Gasoline, diesel and aviation fuel are three very convenient transport fuels There arepossible replacements which are less user-friendly, but for others such as air travel andfor agricultural and mining equipment, there are no viable alternatives

We must again look at short, medium and long term options Liquefied natural gas(LNG) must offer some temporary respite especially for public transport (see Chapter10) In the United States, truckers are moving to cheaper and cleaner LNG In 1997,truckers used 7 Mm3 (7 million cubic meters) of LNG while in 2012 this increased to

33 Mm3[24] Mobil and Exon believe LNG is the critical fuel of the future[25]

Other options include biomass-coal- gas- and waste to liquid fuels (see Chapters 2e6,

9, 10, and 21) Biofuels will never be a major transport fuel as there is just not enoughland in the world to grow plants to make biofuel for all vehicles It can however, be part

of an energy mix to take us into a future of renewable energy Global biofuel production

Chapter 1
Introduction With a Focus on Atmospheric Carbon Dioxide 11

grew from 60 Mtoe 2010 to 81 Mtoe in 2017 at an annual increase of about 3%[26] In

2012 biofuels provide around 4% of the world’s fuel for transport In Brazil, biofuelprovides 23% of all transport fuel, compared with 4% in the United States and 3% inthe European Union[15,27] The US is the largest producer in the world producing 37Mtoe in 2017; Brazil and South America, 23 Mtoe; and Europe (mainly Germany) 12Mtoe[27]

Other solutions include: move to public transport; hydrogen (see Chapter 22); fuelcells (see Chapter 23); and lithium ion battery operated vehicles (Chapter 11) Thesebatteries must, however, be charged using electricity derived from nuclear or renewableenergy, otherwise the whole concept of moving away from fossil fuel is defeated There isalso a nagging doubt that the amount of electricity required to charge all cars is perhapstoo great for any national grid

1.6 Thermodynamics and sustainable energy

We can learn a lot from thermodynamics when it comes to sustainable energy In linkingthermodynamics to sustainability energy, it is necessary to first define sustainability interms of conserving energy In today’s world we are living in a most unsustainable way;depleting our natural resources of minerals (one example involves rare earth metals);fossil fuels; and biota which includes trees, vegetation and the fish in the sea.Furthermore, we are depleting our soil of nutrients through unsustainable farmingpractices All of these actions compromise future generations In short, we are living avery unsustainable life

Sustainability of the environment implies causing little or no damage to the ronment to make it possible for our civilization to continue for a long time The energy

envi-we are currently using is not sustainable as there is a limit on the amount of coal, oil andgas in the earth’s crust Furthermore, the use of fossil fuels results in an increase of the

CO2level in the atmosphere

To be sustainable, we must not let the resources of the earth change from theequilibrium levels which have sustained the biota on planet earth for thousands of years.This refers in particular, to the gaseous mix of our atmosphere

The Second Law of Thermodynamics tells us that in a closed system (no interchange

of matter and energy with the outside world) the change of energy from one form toanother involves an increase of entropy As a result, in the end, the system runs down Inother words, sustainability is not possible in a closed system when energy is inter-changed Fortunately, planet earth is not a closed system and energy does enter thesystem via the sun

To help maintain a sustainable system on Earth it is the incoming energy, the sun’senergy, which must be harnessed, not the energy systems inherent in the Earth Thesun’s energy is the only sustainable energy we have to work with We can harness it in

a number of ways: using solar cells to convert the sun’s energy into electricity, and

12 Future Energy

wind energy to generate electricity The latter is indeed a secondary effect resultingfrom the sun’s energy.

The dilemma facing our civilization should thus be: how can we best harness thesun’s energy to create a sustainable life on earth? There are many ways of doing this andsome are discussed in this volume A few examples include:

growing trees and harvesting the wood to make electricity (efficiency less than 1%)

extracting chemicals from plants for plastic manufacture, pharmaceutical ture etc

manufac-
use solar cells (efficiencies between 1% and 20%)

use wind energy to generate power

develop permaculture,

develop new hydroelectric power systems

Sustainability on earth refers not only to future energy but must take into accountissues such as material recycling, reusing and reducing

1.7 The energy situation in the world today

Emissions from burning fossil fuels with a contribution from cement manufacture areresponsible for almost 90% of the increase in atmospheric CO2since preindustrial times.The other emissions result from land clearances, agriculture, waste and deforestation(seeTable 1.4)

The concentrations of CO2 and methane have risen from (280e415) ppm (106) and(700e1850) ppb (109), respectively, since preindustrial times to July 2018 [7,28] Bothconcentrations are very likely much higher than any time over the past 650000 years Theimportant issue is that the recent rate of change is dramatic and unprecedented; in-creases in CO2concentration have not exceeded 30 ppm over a period of 1000 yearseyetnow, the CO2concentration has risen by over 30 ppm in just the past 17 years[28].The percentage of renewable energy in the world is still relatively small and the USEnergy Information Administration, (EIA) and British Petroleum estimates (see

Table 1.2) that in 2017 about 14% of world marketed energy consumption is fromrenewable energy sources (hydropower, biomass, biofuels, wind, geothermal, and solar).The percentage of renewable energy used in electricity generation in the world increased

by 6.3% on the year 2017 and has been estimated by the International Energy Agency and

by the US Energy Information Administration to be 21.5% in 2015% and 25% in 2017thanks mainly to wind, solar and hydropower additions[29,30] The rate of increase isabout 0.2% a1[30]

In spite of new renewable schemes coming on stream all around the world, thepercentage of the total global energy which is renewable is small at 14% for the year 2017(seeTable 1.2) We do not appear to be making much headway with renewable sources.Coal, oil and natural gas continue to be the main energy suppliers and the levels of CO2

Chapter 1
Introduction With a Focus on Atmospheric Carbon Dioxide 13

continue to rise at an increasing rate Why is it so difficult to change the balance betweenrenewable sources and fossil fuels? One answer is that developing nations, especially inAsia, are rapidly expanding their electricity generation by building many new coal-firedpower stations In many cases, the coal is sourced from Western countries that havereplaced their own coal-fired power stations with cleaner natural gas This is particularlytrue of the United States and Australia In 2016, the United States exported 63 Mt of coalbut in 2017 this had increased to 79 Mt Japan, China, India and South Korea were themain importers of this coal[31].

In 2010, Australia exported 148 Mt thermal coal; two years later this had risen to

163 Mt and in 2017 Australia exported a record amount of 200 Mt In 2017 metallurgicalcoal export from Australia also reached an all time high with exports totaling 172 Mt[32].The driving force of this increasing coal export is profit from fossil fuels mining with

no thought of the resulting rising global CO2 levels In many cases, these and otherWestern countries are purchasing products from factories using the electricity from coal-fired power stations, and at the same time proud of their own record of reducing CO2

emissions Another answer is that big companies are now so powerful that governmentskowtow to them One example was recently highlighted by Professor James Hansen, aprominent US climate scientist, who said that major international oil companies werebuying off governments, and accused the Canadian government of acting as theindustry’s tar sands salesman in its attempt to persuade European nations to accept oilfrom Canada’s tar sands, the mining of which has an appalling environmental record.The Canadian tar sands are the third biggest oil reserve in the world[33]

Yet another answer to the question is the human reluctance to change, which appears

to come from a deep-seated feeling that the status quo should be maintained at all costs

J K Galbraith summed it up with the statement “Faced with the choice of changingone’s mind and with proving there is no need to do so, almost everyone gets busy withthe proof.”[34]

It will take strong governments round the world to change people’s habits and move

to renewable forms of energy This could change soon and might indeed be due tolectures given by the brave young school girl from Sweden - Greta Thunberg[35]

1.8 How can we reduce the stranglehold of fossil fuels?

With over 80% of global energy coming from fossil fuel, the change toward renewablesources will be very slow Fossil fuels are cheaper than any other fuel at present andmoney appears to dictate the markets However, fossil fuels will probably not run outwhile humans are still on the planet If we did mine all the coal and pump out all the oiland gas, the global CO2levels would rise to levels that would result in a huge rise inglobal temperatures, which in turn would cause total chaos and havoc in the world withhardship, misery and disaster to billions of people It MUST never be allowed to happen.Before it is too late, governments around the world must stand by the agreements they

14 Future Energy

have been made in COP meetings such as in HyderabadeCOP11 (2012) andCancuneCOP13 (2016).

Some possible lines of action are:

Reducing our reliance on cars and encouraging public transport;

Kick-starting renewable sources by imposing stiff taxes on the suppliers and users

of fossil fuels and fossil fuel generated electricity and let the markets dictate the rection It is possible that renewable energy will only be important in our societywhen it becomes cheaper than fossil fuel;

di-
Opposing the idea that profit should be the only driving force behind investments;

Encouraging research and development into renewable forms of energy;

Encouraging solar heaters and PVs by legislation especially in the case of newbuildings;

Taxing heavily imported products made in factories using fossil fuel for electricitygeneration;

Preparing the public to accept a reduction in power, and cheap flights, and goodsmade in countries using fossil fuel;

Electing leaders to overcome the present double standards of governments;

Selecting renewable energy sources that are most appropriate to the local

environment;

Compelling governments to accept the loss of the present huge fossil fuel tax nues It will require a massive amount of public pressure to push governments intoaccepting such schemes It is difficult for governments especially when pressurized

reve-by huge oil companies Four of the top 10 Fortune500 companies are indeed oilcompanies - China National Petroleum (rated fourth), Royal Dutch Shell (fifth),British Petroleum (eighth) and Exxon Mobil (rated ninth), each with a revenues ofbetween $250e350 billion US dollars which is larger than the GDP of many coun-tries EU countries[36];

Accompanying all products made from electricity generated from burning fossilfuel and especially coal, should be the warning (similar to those used in cigarettepackets) that the indiscriminate use of such products is endangering our preciousplanet

A final issue relates to collaboration What is the point of reducing the carbon lutants in one country when another is making no effort and continues burning coal? Is itlikely that the next UNFCCC (COP25) conference in Santiago will achieve anything? Let

pol-us all hope that it will

[3] https://www.bp.com/content/dam/bp/en/corporate/pdf/energy-economics/statistical-review/ bp-stats-review-2018-full-report.pdf

[4] T.M Letcher, Introduction, in: T.M Letcher (Ed.), Future Energy: Improved, Sustainable and Clean Options for Our Planet, Elsevier, Oxford, 2014, p 5.

[5] https://www.iea.org/etp/tracking2017/transportbiofuels

[6] http://www.esrl.noaa.gov/news/2013/CO2400.html

[7] https://www.co2.earth/daily-co2

[8] Climate change (2007) e impacts, adaptation and vulnerability Contribution of the Working Group

II to the 4th Assessment, Report of the IPPC, editors M Parry et al, pp 58, Cambridge University Press, Cambridge.

[14] K Wagener, Total anthropogenic CO 2 production during the period 1800 e1935 from carbon-13 measurements in tree rings, Radiation and Environmental Biophysics 15 (2) (1978) 101 e111 [15] R.P Tuckett, in: T.M Letcher (Ed.), The Role of Atmospheric Gases in Global Warming in Climate Change, Observed Impacts on Planet Earth, second ed., Elsevier, Oxford, 2016, pp 382 e383 [16] R.P Tuckett, in: T.M Letcher (Ed.), The Role of Atmospheric Gases in Global Warming in Climate Change, Observed Impacts on Planet Earth, second ed., Elsevier, Oxford, 2016, pp 375 e396 [17] S Cohen, The role of widespread surface solar radiation trends, in: T.M Letcher (Ed.), Climate Change: Observed Impacts on Planet Earth, second ed., Elsevier, Oxford, 2016, pp 491 e508 [18] G Stenchikov, The role of volcanic activity in climate and global change, in: T.M Letcher (Ed.), Climate Change, Observed Impacts on Planet Earth, second ed., Elsevier, Oxford, 2016, pp.

[22] Q.-B Lu, Cosmic-ray-driven reaction and greenhouse effect of halogenated molecules, International Journal of Modern Physics B 27 (2013) 1350073 https://doi.org/10.1142/S0217979213500732

[34] J.K Galbraith, Economics, Peace and Laughter, The New American Library/Signet, New York, 1971,

The demand for coal surged in the Industrial Revolution as a result of the invention ofthe steam engine by James Watt in the 18th century[1] Coal was used to produce gas forgas lights before the modern electric era when coal was used for electricity generation.The first coal-fired power station was developed by Thomas Edison in New York City in

1882 Thermal coal was burned in pulverized coal combustion systems to produce pressure steam, which was passed into a turbine to generate electricity In the 1960s,petroleum overtook coal as the largest source of primary energy because of the hugegrowth in the transportation sector World primary energy consumption increased by2.2% in 2017, the highest since 2013[2] In 2017, coal’s share in primary energy supplyfor the whole world was 27.6% [2] Fig 2.1 shows the shares of total primary energyconsumption by major fuels such as oil, coal, and natural gas The dependency on coaldecreased from 2011 and is now compensated by natural gas and renewables Oilcontinues to be the major supplier of primary energy, accounting for 34.2%

high-Coal continues to be the backbone of the electricity generation, providing about38.1% of the world’s electricity needs in 2017[2].Fig 2.1shows the dominance of coalover the next highest fossil fuel and natural gas (23.2%) Other major contributors to theelectricity sector include hydroelectricity (15.9%) and nuclear power It is important tonote the decrease in oil consumption for electricity generation and the steady increase ofrenewable electricity over the last decade However, coal still holds a very strong position

in electricity generation[2]

Some coals are high-rank coalsdmore mature, characterized by high calorific valueand high C/H ratiodwhereas, others are low-rank coals mostly known as lignite

© 2020 Elsevier Ltd All rights reserved.

characterized by high moisture content and low calorific value Both types of coals aremuch better distributed around the globe when compared with oil and gas, which isconcentrated in only a number of regions around the world[3] The reserves and pro-duction of these coals are discussed inSections 2.1.1 and 2.1.2.

Some coals, known as metallurgical coals, are used in iron production for reducingiron ore to metallic iron in blast furnace These coals have specific properties that help inproducing metallurgical coke Also, coal has been used for the manufacture of chemicalsfor many centuries Coals to chemicals or to liquid fuels are currently limited to only asmall fraction of total coal utilization South Africa and China are the leaders in thisendeavor This chapter concentrates mainly on the use of coal for power generation In

Sections 2.2.1 and 2.2.2, various types or ranks of coal are discussed Operational as well

as environmental issues of coal, as utilized for electricity generation, are discussed in

Section 2.3 In Section 2.4, the different advanced technologies used to overcome theproblems discussed inSection 2.3are discussed Future directions of coal consumptionand conclusions are given inSections 2.5 and 2.6, respectively

2.1.1 Coal reserves and distribution

Coal exploration activities to discover coal reserves include creating a geological map ofthe area, carrying out geochemical and geophysical surveys and exploration drilling Themining operation only begins if the coal can be economically recovered As per the BPstatistical review, the world coal reserves are estimated to be 1035
109t (1035 billiontonnes) [2] The major coal reserves are found in India, China, Russia, and the United

22 Future Energy

States.Fig 2.2shows the proven coal reserves between 1997 and 2017 The Asia Pacificholds the most reserves (41% of total), which are split mainly between Australia, China,and India The US remains the largest single reserve holder (24.2% of total).Table 2.1

shows the availability of coal as a source of energy for the long term compared with otherfuels such as oil and natural gas The reserves-to-production ratio (R/P) for coal is muchhigher than for oil and gas as shown in Table 2.1 [2,4] As per the current productionrates, the proven coal reserves are sufficient to meet 137 years of global coal production.R/P for coal in different regions give an indication of how long the coal resource will last

if the current production rate continues at different regions of the world TheCommonwealth of Independent States countries top the list with about 397 years ofreserves North America has about 335 years more for the extraction of coal at the cur-rent rate The consumer-centered Asia Pacific has about 80 years of reserves left

2.1.2 Current extraction trend and use

World coal production increased by 3.1% in 2017 after falling for 3 years The trendchanged in 2017 with a total production of 7549 Mt as per IEA Key Statistics 2018 Coal ismade up of thermal coal, coking coal, and lignite, and the data for the last 3 years aretabulated inTable 2.2 About 75% of the total coal produced is steam coal

FIGURE 2.2 Distribution of proven reserves in 1997 and 2017 Data from BP Statistical Review of World Energy 2018.

Table 2.1 Reserves-to-production ratios for oil, coal, and natural gas, 2017

data[2,4]

Chapter 2  Coal: Past, Present, and Future Sustainable Use 23

The People’s Republic of China is the world’s leading coal producer since 1985, and in

2017, China produced 3.376
109t (3.376 billion tonnes) of coal, which is roughly 45% ofthe total coal production in the world The second and third top producers are India andthe United States Production in the United States increased by 6.3% compared with

2016 levels The top 10 coal producers and the respective quantities are shown inFig 2.3.Out of major producers of coal, Indonesia tops the list of net exporters by exportingalmost 80% of their production Australia, once the top exporter, is the second largestexporter with a significant portion (76%) of coal exported Despite being the top pro-ducers of coal, China and India continue to be the top net importers of coal, with 263and 207 Mt of net imports to China and India, respectively[4]

Coal is mainly used for the electricity generation and commercial heatingdin 2016,this took up 65.3% of the primary coal usage globally Other sectors of usage for coalinclude iron and steel production, cement manufacturing, and as a feedstock for liquidfuel In OECD countries, the coal share for electricity and commercial heating increase to82.4% Coking coal is an essential element in blast furnace steel production Non-OECDcountries account for 82.9% of the total coking coal consumption Fig 2.4 shows thecountry rankings for the coal-fired power generation for 2016 China tops the list with

4242 TWh with almost 60% of the coal demand in China used for power generation.Coal will continue to be a major energy supplier for the world for at least the next two

to three decades However, increased competition from other fuel resources, shift tocleaner energy, and climate change mitigation plans are the challenges for the coalsector Different steps for sustainable use of coal include improvement of the coal

Table 2.2 Total world coal production (Mt)[5]

702 501 488 387 257 175 127 106 700

People's Republic of…

United States Indonesia South Africa Poland Rest of the world

Million Tonnes FIGURE 2.3 Top coal-producing countries (2017 provisional data) [4]

24 Future Energy

quality, deployment of higher efficiency and lower emission technologies, and ment in CO2capture and storage.

invest-2.2 Coal classification and characterization

2.2.1 Coal classi fication

The four types of coal include peat, lignite (or brown coal), bituminous (or hard coal),and anthracite The coal is classified in terms of the change it has undergone from peat

to anthracite The quality of coal is determined by the temperature, pressure, and length

of time of formation Peat and lignite have low organic maturity compared with othercoals If the effects of temperature and pressure continued for many more millions ofyears, the lignite would gradually be transformed to an intermediate stage betweenlignite and bituminous called subbituminous Bituminous coal and anthracite are thefurther improved stages of coal formation Fig 2.5 shows the modified Van Krevelen

050010001500200025003000350040004500

Coal Lignite Peat

Biomass

Anthracite

FIGURE 2.5 Classi fication of solid fuels by O/C and H/C ratios [6]

Chapter 2  Coal: Past, Present, and Future Sustainable Use 25

diagram explaining the degree of coalification[6] The direction of coalification is fromplant material or biomass to anthracite Both O/C and H/C values are low for anthraciteand high for biomass and peat The lower the O/C and H/C ratios, the greater the energycontent of the fuel; this is a result of the higher energy contained in carbonecarbonbonds compared with carboneoxygen and carbonehydrogen bonds.

Lignite and subbituminous coals are called low-rank coals, which are softer and havehigher moisture content compared with that of higher rank coals Anthracite and bitu-minous coals are called higher rank coals, which are harder and have higher carbon/energy content compared with that of low-rank coals.Fig 2.6 shows different types ofcoals, their distribution, and main uses Almost 47% of the coal available in coal reservescontains low-rank coals[1] Bituminous coal is the most important type of coal and can

be subdivided into thermal and metallurgical coals Thermal coal is also known as steamcoal, which is mainly used for power generation and metallurgical or coking coals areused for the manufacture of iron and steel

2.2.2 Coal characterization/properties

Coal is a highly heterogeneous material both in organic matter as well as in mineralsassociated with the coal matrix This is due to the heterogeneity in original plant matterand surroundings during deposition history The heterogeneity in coal matrix, even at

FIGURE 2.6 Different types of coals and its reserve percentages and end uses [1]

26 Future Energy

less than a millimeter scale, is clearly shown inFig 2.7 Coal consists of several maceraltypes and minerals with varying physical and chemical structures The dark part with lowreflectivity known as vitrinite maceral has higher hydrogen content The shiny part ofhigh reflectivity known as inertinite maceral has higher carbon content The very brightparts of the particle are the mineral grains in the coal particles.

Different components of coal in Fig 2.7 correspond to different reflectivity; an dicator of different C/H ratio These components are termed macerals and includeliptinite, vitrinite, and inertinite Reflectivity in general increases with coalification/maturity of coal with time and climate conditions of the coal deposit The rank of thecoal is related to the vitrinite reflectancedthis is usually determined by manual opticalpetrography[7]

in-Coal is conventionally characterized by proximate analysis, ultimate analysis, calorificvalue, and ash analysis Proximate analysis gives information concerning the moisture,ash, volatile matter, and fixed carbon content The volatile content of the coal gives anindication of the ignition properties of the coal The moisture content reduces the effi-ciency/net calorific value of coal during combustion The calorific value is primarily usedfor coal trading and determining the price of coal Ash analysis of coal is importantbecause over 90% of the operational problems during coal combustion are due to the ashcontent Ash content and its composition are reflected in ash deposition problems inboilers The ratio of acidic oxides to basic oxides is responsible for fouling and slagging inboilers or gasifiers

The inorganic matter in coal is made up of three componentsdinherent inorganicelements associated with plant matter, salts, which are a result of the aqueous sur-rounding during deposition, and extraneous/discrete minerals This inorganic matterforms ash during combustion, and the ash analysis is usually obtained by X-ray

FIGURE 2.7 Heterogeneous nature of organic matter in pulverized coal sample (63e90 mm) [8] Reprinted with permission from Copyright Elsevier 2017.

Chapter 2  Coal: Past, Present, and Future Sustainable Use 27

fluorescence or inductively coupled plasma-mass spectrometry (ICP-MS) This part ofthe coal is responsible for more than 90% of the operational problems such as slagging,fouling, and ash deposition.

There have been recent developments in digital automated methods for izing the heterogeneity Automated reflectogram (AR) technique and computer-controlled scanning electron microscopy (CCSEM) are two advanced microscopicanalytical techniques used to obtain detailed information on the organic matrix of coaland mineral data, respectively[7] AR is capable of providing information concerningorganic matter This can be used for assessing the ignition, characteristics, and inorganic(mineral) constituents of coal, an indication of heterogeneity in the organic component.CCSEM gives detailed information about the distribution of mineral matter in coal andmineralecoal association at the individual particle level along with the mineral grain sizedistribution It also provides details of minerals included in the coal matrix

character-CCSEM and AR are good for solving boiler problems Advanced analytical techniques

as described above are used to predict the conversion behavior of coal and to solveoperational issues faced during the combustion of coal

2.3 Issues with coal utilization

Direct utilization of coal in power generation is associated with several problems, whichare broadly classified into operational and environmental, as shown in Fig 2.8 The

FIGURE 2.8 Coal combustion, its associated problems, and coal cleaning as a solution to address various issues.

28 Future Energy

operational problems are mainly related to carbon conversion and ash deposition such

as slagging, fouling, and corrosion The coal rank and type and combustion technologyinfluence the carbon conversion leading to energy loss in terms of unburnt carbon Ashdeposition is related to the mineral matter and other inorganic matter in coal Theenvironmental issues include the emissions of sulfur oxides, nitrogen oxides, particulatematter, and toxic elements such as mercury

Coal contains minerals, which during combustion are mostly transformed to ash andrejected as slag or fly ash from the boiler The ash in the boiler can cause ash deposition

in high-temperature regions (slagging) and in low-temperature regions (fouling),resulting in decreased heat transfer and reduced steam generation Some inorganiccomponents such as chlorine and sulfur cause corrosion to equipment Sulfur, chlorine,and other trace and toxic elements present in coal also cause environmental problemsonce emitted into the atmosphere The impact of coal on the environment depends notonly on the coal grade but also on how it is utilized Coal can be utilized either directly orafter cleaning The direct utilization of coal extracted from a mine is associated withproblems related to ash deposition, corrosion, fouling, heat transfer, and emission ofpollutants: particulate matter (PM), NOx, SOx, trace elements The use of high-grade coal

or coal after upgrading (where minerals and trace elements contained are removedbefore combustion) reduces the operational and environmental issues occurring duringcoal utilization The details will be discussed in the following sections

2.3.1 Operational issues

The operational issues during coal combustion are mainly related to the impurities/mineral matters contained in coal Mineral matter and other inorganics in coal influencethe ash character and deposition behavior in boiler During coal combustion, mineralmatters are left behind and its quantity and properties are of serious concern to anyfacility The ash causes fouling and corrosion to the equipment and treatment units.High ash content in coal leads to higher amount of bottom ash and fly ash rejection,which needs additional work to collect, dispose, or utilize In addition, the coal ash canclog the pores of catalysts used for gas cleaning and conditioning

The inorganic matter in coal may be present in three different forms: water-solublesalts, organically bound elements, and discrete mineral grains[8] The inorganic mat-ter interaction during coal combustion takes place in two steps Firstly, the inorganicmatter evaporates from coal, enters into flue gas stream, and may interact with discreteparticles Secondly, these discrete ash particles may come in contact with heat transfersurface or onto the existing slag layer on the boiler wall Ash analysis and ash fusiontemperatures have been used to assess these issues for different coals; however, CCSEManalysis can predict/simulate the ash deposition more accurately

Most of the high-grade coals have already been mined and used in the past to copewith the operational issues Low-grade coal reserves are associated with the issuesshown inFig 2.8

Chapter 2  Coal: Past, Present, and Future Sustainable Use 29

There are operational issues such as ignition problems and unburnt carbon that can

be linked to the volatile matter content and rank of coal, respectively Low volatile matter

in coal makes the coal difficult to ignite, and higher content of inertinite leads to higheramount of unburnt carbon

2.3.2 Environmental issues

The environment is affected negatively in every steps of coal extraction, transportation,storage, utilization, and postutilization Environmental issues related to coal combustionare multifaceted and post a question mark on the sustainable use of coal These issuescan broadly be classified into (i) gaseous emission, (ii) particulates and trace/toxic ele-ments emission, (iii) greenhouse gas (GHG) emissions, (iv) wastewater, and (v) solidwaste These are discussed briefly in the following sections

2.3.2.1 Gaseous emission

Coal combustion releases air pollutants into the atmosphere with the major pollutantsbeing NOx, SOx, and acid gases NOx, which is mainly composed of NO2and NO formsfrom nitrogen present in coal and from the thermal reaction of N2 and O2 at hightemperatures in the flame NO and NO2are precursors of secondary pollutants such asacid rain and form photochemical smog and ground-level ozone NOx also contains

N2O, which is a GHG that causes global warming All the S present in coal, bothorganically associated with coal and present in the form of pyrites, gets oxidized duringcombustion and converted to SO2 In the presence of excess amount of oxygen andhigher temperaturew800C, SO2 is further oxidized to SO3 SO2contributes to acidifi-cation, whereas SO3 causes corrosion in the facility and effects human health onceemitted into the atmosphere

2.3.2.2 Particulates and trace/toxic elements emission

During coal combustion, a large proportion of inorganic matter is collected as ash(bottom ash or fly ash), and a very small part of it is released into the atmospheredepending on the particulate control devices used and their collection efficiency Fineparticulates with diameters of less than 10mm (PM10) and less than 2.5mm (PM2.5) have adeleterious effect on human health The particulate and trace element emissions limit isbecoming more and more stringent around the world[9,10] The control of particulates

in developed countries is satisfactory as defined by the local regulatory requirements andalso the technology being used However, in developing and in countries in transition,particulate emission is of great environmental concern

Coal contains a wide variety of elements Trace elements are those whose trations in coal are below 100 ppm The trace element concentration in coals depends onrank of coal and the associated geology [11] Trace element concentration may varysignificantly within the coal and even from the same seam Trace element emissionduring coal combustion is affected by their occurrence modes: organic (chemical-,physical-, bound) and inorganic (physical bound, discrete minerals) in coal In general,most trace elements are associated with the mineral matter in the coal

concen-30 Future Energy

The physical and chemical properties of trace elements may alter depending on themining, transportation, handling, and storage before combustion The emission speciesand quantity during coal combustion depend on the form of the trace element, theconcentration in coal, combustion temperature, atmosphere (oxidizing, reducing),halogen concentration, flue gas components, and the control device used together withthe collection efficiency For example, metals having higher boiling point (e.g., As, Be, Cd,

Cr, Co, Mn, Ni, Pb, and Sb) first evaporate during combustion and condense back onto thesurface of fine particulate as the temperature decreases The particulates bound to metalswith high boiling points can be removed using particulate control devices, whereas metalswith relatively lower boiling point such as Hg and Se are mostly distributed in the gaseousphase, which are able to pass through pollution control devices and are emitted into theatmosphere Trace elements such as Hg, As, and Se are of great concern because theycause damage to the environment and to human health[12]

2.3.2.3 Greenhouse gas emissions

The share of coal in total primary energy supply is 28%, but it accounted for 45% of theglobal CO2emission in 2015[13]: the global CO2emissions being 32.3 GtCO2currently[13].The carbon content in coal is the highest among fossil fuels Combustion of coal releasesGHGs such as CO2 In addition, there are some contribution from coal utilization such as

CH4 during mining and N2O during combustion [14,15] CH4 and N2O are of greaterconcern because of their higher global warming potential The global warming potentialvalues for CH4and N2O relative to CO2are 28 and 265, respectively[16] In 2019, the globalatmospheric concentration of CO2reached 414 ppm (see Chapter 1 of this volume), which

is about 40% higher than in the mid-1800s concentration of 280 ppm The CO2 in theatmosphere has increased by an average growth rate of 2 ppm per year over the last

10 years This increasing trend of CO2in the atmosphere is a serious concern because thiscan lead to extreme weather events, changes the rainfall pattern, affects agroecosystem,affects biodiversity, increases human diseases, and increased mortality rate[17]

2.3.2.4 Wastewater

Water pollution is common in areas near to coal mines[18,19], and particular pollutant

is sulfur Coal power plants use water for steam production, cooling, and flue gascleaning (in wet devices), which generates wastewater The coal power plant may pollutethe nearby waterbodies or the underground water by releasing hot water and pollutedwater (with chemicals and pollutants during flue gas cleaning) and contaminantsleaching from fly ash disposal ponds[20,21] Coal combustion residues, which typicallyhave high concentrations of toxic elements, are usually disposed of in ash ponds orlandfill, which causes ground water pollution due to leaching[20,22]

utilization on economics and environment can be reduced by using the coal combustionby-products in construction materials Not all the coal combustion products are wasted;some are used beneficially, such as fly ash in cement kiln to produce clinker The unusedby-products containing higher concentration of toxic chemicals create the problem Themajor environmental concern for coal combustion waste disposal is leaching of toxicpollutants, present in fly ash, into the waterbodies[21,22].

2.4 Clean coal technologies

Coal can be sustainably utilized if we can reduce the pollutant emissions significantlyand bring down the GHG emissions The emission limits are becoming more stringentover time The control technologies for the pollutants, other than GHG emissions, arewell established to satisfy current legislation Coal can be sustainably utilized making use

of high efficiency low emission (HELE) technologies and carbon capture and storage(CCS) technologies Technologies for mitigation of GHG emissions are expensive and arestill at a demonstration phase

The issues (operational and environmental) related to coal utilization as discussedabove can be addressed in three ways:

(a) precombustion coal upgrading: mineral impurities and moisture in coal are

removed before combustion,

(b) high-efficiency combustion technologies: to increase efficiency and reduce thepollutants formation such as supercritical (SC) and ultrasupercritical (USC)

boilers, integrated gasification combined cycle (IGCC), and integrated gasificationfuel cell (IGFC),

(c) postcombustion cleaning: mainly controlling pollutants in flue gas

These technologies are discussed in the following sections

To resolve the operational and environmental problems related to coal combustion,several clean coal technologies have been utilized, which mainly involves coal dew-atering, demineralization, and removal of harmful constituents such as sulfur andmercury Basically, coal cleaning is a process by which impurities contained in coal arediscarded to improve its quality Coal cleaning can be classified into physical andchemical cleaning Coal cleaning will be discussed briefly in four sections: (i) wetbeneficiation/coal washing, (ii) dry beneficiation, (iii) drying of lignites and subbitu-minous, and (iv) preparation of ultraclean coal (UCC)

2.4.1.1 Wet beneficiation/coal washing

Currently, the wet coal beneficiation process is the predominant method for coalupgrading The wet beneficiation processes include heavy media separation, cyclone

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