Coal and Coalbed Gas: Future Directions and Opportunities

By Romeo M. Flores and Tim A. Moore

Coal and Coalbed Gas: Future Directions and Opportunities, Second Edition introduces the latest in coal geology research and the engineering of gas extraction. Importantly, the second edition examines how, over the last 10 years, research has both changed focus and where it is conducted. This shift essentially depicts "a tale of two worlds"—one half (Western Europe, North America) moving away from coal and coalbed gas research and production towards cleaner energy resources, and the other half (Asia–Pacific region, Eastern Europe, South America) increasing both research and usage of coal. These changes are marked by a precipitous fall in coalbed gas production in North America; however, at the same time there has been a significant rise in coal and coalbed gas production in Australia, China, and India. The driver for higher production and its associated research is a quest for affordable energy and economic security that a large resource base brings to any country like Australia’s first large-scale coalbed gas to liquid natural gas projects supplying the demand for cleaner burning LNG to the Asian-Pacific region. Since the last edition of this book, global climate change policies have more forcibly emphasized the impact of methane from coal mines and placed these emissions equal to, or even more harmful than, CO2 emissions from fossil fuels in general. Governmental policies have prioritized capture, use, and storage of CO2, burning coal in new highly efficient low emission power plants, and gas pre-drainage of coal mines. The Organization for Economic Cooperation and Development (OECD) countries and China are also introducing new research into alternative, non-fuel uses for coal, such as carbon fibers, nanocarbons, graphene, soil amendments, and as an unconventional ore for critical elements.

New to this edition: Each chapter is substantially changed from the 1st edition including expanded and new literature citations and reviews, important new data and information, new features and materials, as well as re-organized and re-designed themes. Importantly, three new chapters cover global coal endowment and gas potential, groundwater systems related to coalbed gas production and biogenic gas generation as well as the changing landscape of coal and coalbed gas influenced by global climate change and net-zero carbon greenhouse gas emissions.

FOREWORD

When I reviewed the first edition of this book, my initial thought was, "Do we need another book on coal geology?" and then I read it and realised, "Yes, we need this book" and my students downloaded copies as soon as it was available. So now we come to 2023, and a lot has happened in the past decade. For a different reason we might ask if we still need this book, or even coal geoscientists and engineers, as the world aims for rapid decarbonisation of the energy sector and a reduction of coal as a feedstock for industrial resources, like steel manufacture.

• Language: English
• Publisher: Elsevier Science
• Release date: Jan 24, 2024
• ISBN: 9780323859387

Romeo M. Flores

Dr. Flores served as a Research Scientist in the Energy Resources Center of the U.S. Geological Survey from 1975–2010; Professor and Chair of the Department of Geology at Sul Ross State University, Alpine, Texas 1966–1975; adjunct faculty at several U.S. universities and external PhD examiner for the Université de Liège, University of the Witwatersrand, and University of Natal from 1982–2010; and consulting geologist/advisor to Anadarko CBM Group in Denver, CO, USA, AECOM/BLM CBM hydrostratigraphy-groundwater modelling for Powder River Basin in Fort Collins, CO, USA, Shanxi Lanyan Coalbed Methane Group and Biogenic Gas Laboratory in Jincheng, China. Since 1995 Dr. Flores has served as an Editorial Board Member of International Journal of Coal Geology, edited international special publications, and organized U.S.-international conferences. Dr. Flores has authored/co-authored publications in coal geology, peat-coal depositional environments, sedimentology, stratigraphy, hydrostratigraphy, basin analysis, coal and coalbed gas resources assessment, coalmine methane, and biogenic coalbed gas of the U.S. and other countries. Dr. Flores is the principal author of the Coal and Coalbed Gas: Fueling the Future, 2014, First Edition and forthcoming Chinese (translation) version. Dr. Flores is a recipient of several national and international awards: U.S. Department of Interior Distinguished Service Award, U.S. Geological Survey Meritorious Service Award, , Geological Society of America Gilbert H. Cady Award in Coal Geology, University of the Philippines Alumni Award in Geology, Philippines La Union Province Pammadayaw Award, and University of Canterbury Angus Erskine Fellow Award.

Book preview

9780323859387_FC

Coal and Coalbed Gas

Future Directions and Opportunities

Second Edition

Romeo M. Flores

Gerson Lehrman Group (GLG), Inc., New York, NY, United States

Geo. Sci. Tech Energy Resources, Golden, CO, United States

Tim A. Moore

Cipher Consulting Pty Ltd, Kenmore, QLD, Australia

School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, QLD, Australia

Distinguished Visiting Professor, China University of Mining and Technology, Xuzhou and Beijing, China

Image 1

Table of Contents

Cover image

Title page

Copyright

Dedication

Authors’ biography

Foreword

Preface

Acknowledgments

SI/metric units

Chapter 1 Introduction

Abstract

Overview

Approach to multidiscipline book

Scope and chapter descriptions

Basic principles

Interdisciplinary definition of coal with coalbed gas

A new low-carbon-based world

Coal and coalbed gas impacts and legacies

Re-emergence of coal as a nonfuel feedstock

Perspectives of global CO2 and CH4 emissions

Final insights

References

Chapter 2 Coal as multifaceted energy resources

Abstract

Overview

Petroleum derived from coal

Coal-derived petroleum systems: Global and geologic models

Coal mine gas derived from coal mining

Coal-to-chemicals (CTC)

References

Chapter 3 Global coal endowment and coalbed gas potential

Abstract

Overview

Geologic coal occurrence and distribution

Global coal endowment

Coal resources and coalbed gas potential: Prologue

References

Chapter 4 Peats, peatlands, peat gases, and depositional systems

Abstract

Overview

Peat-to-coal environments

Peatlands: Peat-forming mires

Types of peatlands

Controls on development of peatlands

Evolution of peatlands

Metaphors for peatlands

Peat types: Fibric, hemic, and sapric

Processes of peatification, gasification, and diagenesis

Origin of peat gas: A biogenic generation

Clastic depositional systems and peat-to-coal preservation

Alluvial plain depositional system

Delta plain depositional system

Lacustrine depositional system

Depositional sequence

Peat accumulation: Balancing with accommodation space and depositional sequence

Peat-to-coal transition: An order of magnitude of time

Sumatran peatlands: Microcosm of carbon sinks and riverine systems

Jambi peatlands: Carbon sinks in flux

Jambi peatland riverine systems: Reshaping carbon sinks with avulsion

Peat-to-coal transition: An order of compression

References

Chapter 5 Coal composition and influence on coal gas reservoirs

Abstract

Overview

Macroscopic components of a coal seam

Microscopic components of a coal seam

Organic and inorganic influence on coal reservoir properties

Summary

References

Chapter 6 Burial and the affect on organics and gas reservoirs

Abstract

Overview

Burial of organic material

Burial of inorganic material

Concept of rank and its classification

Using organics to model basin maturity

Affect of burial and coalification on coal reservoir properties

Affect of stress on coal reservoir properties

Summary

References

Chapter 7 Evaluating gas quantities

Abstract

Overview

Geological assurance

Assessing gas resources

Classification systems for gas resources and reserves

Case studies for coalbed gas reservoirs resource assessment

Summary

References

Chapter 8 Producing gas from coal reservoirs

Abstract

Overview

Drilling technologies

Well completion designs

Reservoir stimulation

Role of geology and reservoir character in completion and stimulation design

Development drilling and gas production

Permeability, gas saturation, and gas flow rates

Reservoir modeling

Gas gathering systems

Summary

References

Chapter 9 Groundwater, co-produced water, and biogenic coalbed gas

Abstract

Overview

Assessment of groundwater systems in coal measures

Co-produced water

Biogenic coalbed gas

Scale-up research in interdisciplinary coal hydrology, geology, and biogenic methane

Conclusions

References

Chapter 10 Worldwide coalbed gas development: Revisited

Abstract

Overview

Global coalbed gas development

North America region

Eurasia region

Asia-Pacific region

Summary

References

Chapter 11 Changing landscape of coal: Net-zero carbon emissions

Abstract

Overview

Coal transitions

Path to net-zero carbon emissions: CCUS technologies

Emerging nonfuel use of coal

Shift of coal use to Asia and Southeast Asia

What’s left? Remaking of coal and coalbed gas?

References

Index

Copyright

Elsevier

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Dedication

We dedicate this second edition to our PhD advisor, Dr. John C. Ferm (1925–1999; Hook et al., 2002; https://doi.org/10.1016/S0166-5162(01)00071-4; Hook, 2002; https://doi.org/10.1016/S0166-5162(01)00070-2), an amazing academic mentor who inspired, fostered, and nurtured our passion for coal and the modes in which it is formed, buried, and transformed. John could be brutal in his assessment of our PhD work, applying the Socratic approach, especially for us first-generation students at Louisiana State University. As a fresh PhD graduate trained by the legendary Dr. P.D. Krynine at Pennsylvania State University, John learned nurturing by challenging students in the classroom, field, and research discussions. John’s philosophical method of teaching evolved into gentle guidance and thoughtful questioning to examine concepts and determine their validity, which nurtured later-generation students at the University of South Carolina and University of Kentucky. We think John would be amused that two of his former students, who bookend his university career, have collaborated on a coal book. During John’s time he witnessed many changes in the direction of coal research and he would not be alarmed that coal is fading as a generator of power. John would welcome the challenge of the new research on noncombustible uses of coal as the world navigates net-zero carbon emissions.

Dr. Flores also dedicates this second edition to his family, Lejo and Emily and grandchildren Ellie and Oliver, who have constantly reminded him that the quicker the book is finished, the sooner he can move to a new home next door to them.

Crafting a book like this is time consuming and steals moments from your family. Thus, Dr. Moore wishes to dedicate this work to his son Micah Allen Setianto Moore and his wife Aretha Christie, and he is deeply thankful for their patience, humor, and encouragement throughout the times when he had to seclude himself. He believes that their sacrifice is perhaps greater than his.

Authors’ biography

Dr. Romeo M. Flores

Expert, Gerson Lehrman Group (GLG), Inc., New York, NY, USA; Principal consultant, Geo. Sci. Tech Energy Resources, Golden, CO, USA.

Dr. Flores served as a research scientist in the Energy Resources Center of the US Geological Survey in Denver, Colorado, USA, from 1975 to 2010; professor and chair of the Department of Geology at Sul Ross State University, Alpine, TX, from 1966 to 1975; and adjunct faculty at several US universities and external PhD examiner for the Université de Liège, University of the Witwatersrand, and University of Natal from 1982 to 2010. Consulting geologist/advisor to Anadarko CBM Group in Denver, CO, USA; AECOM/BLM CBM hydrostratigraphy-groundwater modeling for Powder River Basin in Fort Collins, CO, USA; and Shanxi Lanyan Coalbed Methane Group and Biogenic Gas Laboratory in Jincheng, China. Since 1995, Dr. Flores has served as an editorial board member of the International Journal of Coal Geology, edited international special publications, and organized US international conferences. Dr. Flores has authored/coauthored publications in coal geology, peat-coal depositional environments, sedimentology, stratigraphy, hydrostratigraphy, basin analysis, coal and coalbed gas resources assessment, coalmine methane, and biogenic coalbed gas in the United States and other countries. Dr. Flores is the principal author of Coal and Coalbed Gas: Fueling the Future, 2014.

Dr. Flores is a recipient of several national and international awards: the US Department of Interior Distinguished Service Award, the US Geological Survey Meritorious Service Award, the Geological Society of America Gilbert H. Cady Award in Coal Geology, the University of the Philippines Alumni Award in Geology, the Philippines La Union Province Pammadayaw Award, and the University of Canterbury Angus Erskine Fellow Award.

Dr. Tim A. Moore

Managing Director of Cipher Consulting Pty Ltd., Kenmore, Australia; Adjunct Professor, School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, Australia; Distinguished Visiting Professor, China University of Mining and Technology, Xuzhou and Beijing, China.

Since 2010, Dr. Moore has been the managing director of Cipher Consulting, specializing in the understanding of and exploration for organic-rich sediments, including coal, coalbed methane, and shale gas. He holds the positions of Adjunct Professor at the School of Earth and Atmospheric Sciences, Queensland University of Technology, Australia, and as Distinguished Visiting Professor at China University of Mining and Technology. Dr. Moore has also been Principal Advisor—Subsurface for Sinopec Oil and Gas Australia Pty Ltd., Principal Geologist/Asset Geologist for Origin Energy Ltd., Chief Geologist and Senior Advisor for Ephindo Energy Ltd., and Senior Advisor for Dart Energy Ltd. He was Vice President for Technical Services and then Country Manager for Arrow Energy International. He has acted as an expert witness in international arbitrations and civil and criminal cases. He is also on the editorial boards of the International Journal of Coal Geology, the Indonesian Journal on Geoscience, and Mongolian Geoscientist. Dr. Moore has published over 275 papers in international refereed journals, reports, and abstracts.

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Foreword

When I reviewed the first edition of this book, my initial thought was, Do we need another book on coal geology? and then I read it and realized, Yes, we need this book, and my students downloaded copies as soon as they were available. So now we come to 2024, and a lot has happened in the past decade. For a different reason, we might ask if we still need this book, or even coal geoscientists and engineers, as the world aims for rapid decarbonization of the energy sector and a reduction of coal as a feedstock for industrial resources like steel manufacture.

Natural gas is earmarked as a transition fuel to enable the shift to renewables. In some basins, the source of that gas is directly from coalbed gas production or from conventional reservoirs that were charged by coal and terrestrial organic source rocks. Although the transition is escalating, there are projections that coal will remain part of our future, even after 2050, and can also provide alternative nonfuel resources (e.g., critical elements and carbon-based nanomaterials). Between now and then, we’d best ensure that we extract and utilize coal and coalbed gas as efficiently and safely as possible, that we mitigate any environmental and social impact of the process, and that we improve our certainty of predicting the behavior of the material and material impacts. To do this, we need to understand coal as a material and the inherent variability of its quality and behavior as a source rock and host of coalbed gas. One can change the technologies but not the geological ground conditions or coal character of the targeted resource.

The authors have taken on this ambitious endeavor during their careers and have attempted to capture their knowledge gained from first-hand experience in countries around the world and a comprehensive review of published material within this book. At least three generations of knowledge are drawn upon here. Tim Moore was a student of both Romeo Flores and his supervisor John Ferm, who was the Warrior of Gentleness when it came to coal research, teaching, and supervision.

This book also reflects the broad and multidisciplinary aspects of coal geology and coal science and provides the tenets for one to understand different disciplines and how they interact to form an integrated view of the resource—technically, economically, and politically. Each chapter takes the reader through different concepts, first setting the scene by examining the status of coal and coalbed gas in a carbon-conscious world, then looking at the science behind coal as a source of gas and as a reservoir—in its own right. Further reading leads to learning about geological settings and the processes through time that led to present-day endowments around the globe, and this theme continues throughout the book with detailed examples from different countries. Personally, I like the emphasis on the depositional environments that lead to peat accumulation and preservation—it’s all about the ingredients—which leads nicely into the world of coal macerals and minerals and why they matter. Coalification and its role in changing the chemistry and material properties of coal are covered from a reservoir perspective, as is the role of biogenic processes. These have produced some of the enormous gas resources we exploit today and could also provide a future circular economy for neo-biogenic gas. The role of groundwater in this past and potentially future endeavor is presented, along with possible adverse effects where there is unexpected communication with regional and local aquifers and surface assets that detract from environmental and social license. In addition to describing the geology and engineering technologies required to explore for, access, and utilize these resources, the book also provides insights into geostatistical and economic modeling for reserve estimation and challenges as reservoirs become more geologically and politically complex for extraction and, alternatively, for injection and carbon sequestration.

The final chapters revisit and integrate concepts presented in the book in order to examine global gas production and the geographic shifts in production and research that have occurred over the past decade(s). They also show how government and the market play a role, and project future trends. The authors provide discussion points for the outlook of coal as a fuel feedstock in a carbon-constrained world and the ongoing search for options and alternative nonfuel uses of coal while highlighting the important role that coal and coalbed gas still play during the transition period and beyond.

There is much to learn from this book, which is based on decades of observing and interpreting patterns and trends in coal and coal-bearing basins. There is a growing trend toward using machine learning and artificial intelligence to find patterns in data and provide solutions. I’d suggest that domain intelligence, such as that provided in this book, is critical to supervising this process and is required for understanding and validating the outputs upon which many decisions are made and will continue to be made in the future.

So yes, we need this book, and I invite you to read, learn, and form your own ideas. If you find any gaps, write about them.

Joan S. Esterle, Emeritus Professor, The Vale-UQ Chair of Coal Geosciences Program, The University of Queensland, Brisbane, QLD, Australia

Preface

The global coal and coalbed gas landscapes have undergone the most consequential changes among the fossil fuel energy resources, as consumption and demand have precipitously declined since publication in December 2013 of the first edition of Coal and Coalbed Gas: Fueling the Future by Dr. Flores. The 2007–09 Global Financial Crisis, also referred to as the Great Recession, led to prolonged low gas prices lasting through 2020. This event was exacerbated by the ramp-up of shale gas production from 2007–12 in North America, which currently accounts for 78% of all United States dry natural gas. Shale gas production largely replaced coalbed gas. Finally, the 2015 Paris Agreement on global climate change, promulgating drastic reduction of carbon dioxide (CO2) and methane (CH4) greenhouse gas emissions, put more pressure on coal use and coalbed gas production, as renewables gained greater market share. The far-reaching effects of critical global events that redirected and reinvented use of coal and coalbed gas compelled the revision of the first edition into Coal and Coalbed Gas: Future Directions and Opportunities, Second Edition, coauthored by Drs. Flores and Moore. The authors bring a rich educational background, with graduate theses in the coal disciplines earned in 1966 and 1990, respectively, and have lengthy professional experience, having worked on various scientific and technological aspects of coal and coalbed gas in coal basins worldwide since the 1980s. Both have published extensively and are members of editorial boards of international journals (see Authors’ biography page).

The Asia-Pacific region has driven global economic growth, relying on both energy imports as well as increasing use of native coal and coalbed gas resources. The realignment of fossil fuel energy use has changed the directions of and opportunities for coal research and development (R&D) worldwide, as shown by Ruppert et al. in a survey published in 2021 in the International Journal of Coal Geology (https://doi.org/10.1016/j.coal.2021.103710). Inputs from coal geoscientists from academia, government institutions, and industry in North and South America, Europe, Australia, Russia, and Nigeria indicate a sharp decline in research related to coal. In contrast, respondents in China and Indonesia indicate an increase in both interest and research. The survey also identified skill sets such as organic/inorganic geochemistry, petrography, thermal maturity, sedimentary systems/depositional environments, and paleoclimate and paleoecology reconstructions that are keys to understanding the past, present, and future Earth systems. Global events as well as the findings of the Ruppert et al. survey are what has driven the updating, reorganizing, expanding, and restructuring of this new edition.

Updated references reflect the changing research directions in coal and coalbed gas. Three new chapters (Chapters 3, 9, and 11) have been added that address the global coal and coalbed gas endowment despite decline of and disinvestment in coalbed gas production in North America, but its increase in Australia and China (Asia-Pacific region). Chapter 10 has been expanded to examine and evaluate factors controlling the pre- and post-peak coalbed gas production in North America and new opportunities for exploration, development, and production in Australia, China, and India. Global climate change policies are driving a switch from coal to gas as well as causing mine closures; however, new uses of coal are emerging and supporting research. Chapters 2 and 11 introduce new research opportunities in the emerging coal-to-carbon based products and materials (e.g., carbon fibers, nanocarbons/carbon nanotubes, graphite/graphene, and activated carbon), which are applied to advanced or new technologies across many industrial sectors (e.g., aerospace, automotive, medical, wind/solar renewable energy, agricultural, life, sports, construction, etc.).

Chapters 2–8 have been updated with new references and a reorganization. It is hoped that the background information provided here will help to inform and upskill professional geoscientists from many different disciplines. The sedimentary systems/depositional environments, paleoclimate, and paleoecology in Chapters 3 and 4 are highlighted by new interdisciplinary peat and coal research, providing better understanding of CO2 and CH4 sinks in the past and present, and implications for future climate change. Chapter 8 is improved to address coalbed gas drilling to optimize production.

Acknowledgments

The 11 chapters of this new edition have benefited significantly from peer reviews by coal and coalbed gas specialists, hydrologists, engineers, soil scientists, and geologists. Special thanks are due to Lisa Rukstales, who was fastidious in her copyediting and proofreading of 7 chapters. Lisa critically reviewed and edited these chapters in keeping with the scientific content (clarity, flow, and structure), quality, and technical accuracy. Lisa and Flores were colleagues at the U.S. Geological Survey, where she honed her editorial expertise in geologic map editing and technical editing/writing.

We extend our gratitude to the following esteemed colleagues who reviewed the following chapters: Lisa Rukstales and Tim Moore (Chapter 1); Lisa Rukstales, Ralf Littke and Peter Warwick (Chapter 2); Lisa Rukstales, Tim Moore, Ralf Littke, and Michael Friedrich (Chapter 3); Lisa Rukstales, Frank Ethridge and Peter Warwick (Chapter 4); Joan Esterle and Zhongsheng Li (Chapter 5); Yong Qin, Wu Li, and Ofentse M. Moroeng (Chapter 6); Michael Friederich, James Pope, Roman Pausch, and John Hattner (Chapter 7); Peter Roles, Roman Pausch, Xingjin Wang, and Doug Henderson (Chapter 8); Lisa Rukstales, Ryan Morris, Michael Brogan, and Paul Fallgren (Chapter 9); Lisa Rukstales and Peter Warwick (Chapter 10); and Lisa Rukstales, Shifeng Dai, Ned Kruger, and Edward Murphy (Chapter 11).

Appreciation is extended to Lisa Rukstales, Yuewen Xi, and Tao Li for their special assistance producing graphics and figures. Shelley Martin (National Energy Technology Laboratory) and Jeanette Hammann (Geological Society of America) provided literature searches and acquisitions. Brendan Stats (TMK Energy) provided the Mongolia coal mine satellite image on the book cover.

Our deep appreciation also goes to Prof. Joan S. Esterle for writing the Foreword to this book. Prof. Esterle is a widely known author in coal and coalbed gas as well as a researcher into palaeoclimates and palaeoecologies in deep time through analysis of organic material. We were thrilled when she accepted to give her insight into the subjects covered in this book.

SI/metric units

Units: 1 metric tonne = 2204.6 lb; 1 kilocalorie (kcal) = 4.18 kJ = 3.96 Btu; 1 kilojoule (kJ) = 0.24 kcal = 0.95 Btu; 1 British thermal unit (Btu) = 0.25 kcal = 1.05 kJ; 1 kilowatt hour (kWh) = 860 kcal = 3600 kJ = 3412 Btu. Calorific equivalents: 1 ton of oil equivalent = 10 million kilocalories = 42 gigajoules = 40 million Btu of heat; 1.5 tonnes of hard coal = 3 tonnes of lignite = 12 megawatt hours; 1 million tonnes of oil produces 4400 gigawatt hours. Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: F = (1.8 × °C) + 32. Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or micrograms per liter (μg/L). The use of hectare (ha) is for the measurement of small land or water areas. The use of liter (L) is for the measurement of liquids and gases. The prefix milli is used with liter. Metric ton (Mt) is commercial usage with prefixes used.

Modified from U.S. Geological Survey publications.

Chapter 1 Introduction

Abstract

This, the first chapter, overviews the current state of coal and coalbed gas in a carbon-conscious world. The 2008 global economic recession resulting in protracted lowering of natural gas prices, the 2015 Paris Climate Change Agreement, as well as the effects of the 2022 Ukraine-Russia conflict have substantially influenced fossil fuel use. However, coal and, to a lesser degree, coalbed gas are still significant as energy fuel for current use and future development. These policies are driving research by countries into how coal can be utilized in nonfuel, alternative applications. This global awareness of climate change and impacts of fossil fuel use underscores the objectives, scope, vision, and principles of this book.

Keywords

Coal; Coalbed gas; Nonfuel coal; GHG emissions; CCUS; Carbon emissions; Greenhouse; REEs; Gasification; Liquefaction

Overview

The global coal and coalbed gas landscapes have changed since the first edition of Coal and Coalbed Gas: Fueling the Future was published in December 2013 (copyright 2014, Library of Congress ISBN 978-0-121-396972-9). The most consequential changes are decline in thermal coal use, partly because of coal-fired power plants being phased out and replaced by natural gas; falling prices make coal uneconomic while opening the market to natural gas (e.g., conventional natural gas and unconventional shale, tight, and coalbed gases) (Speight, 2019; IEA, 2021a). In advanced economies (e.g., Europe, United States [U.S.]), coal is also being replaced by renewable energy for electric power generation driven by concerns of the effects of greenhouse gas (GHG) emissions on global climate change and moves to limit emissions to net-zero carbon emissions by 2050 as envisioned by the 2015 Paris Agreement (UNFCCC, 2016; IEA, 2021a). Coal-fired electricity generation is disappearing in countries in the European Union and the United States (IEA, 2021a; USEPA, 2021a; USEIA, 2021a, b). The changing landscape of coal use shifting to less carbon intensive natural gas and renewables in the electric power generation sector is indicated by the palpable decrease in carbon dioxide (CO2), which peaked in 2007, from 1990 to 2019 in the U.S. (Fig. 1.1) (USEPA, 2021a). However, during the same period, the relative contribution of CO2 emissions from coal use by the U.S. electric power and industrial economic sectors is much lower (21.1%) than petroleum (45%) and natural gas (33.9%) use by five major fuel-consuming economic sectors (Fig. 1.2) (Boden et al., 2017; USEPA, 2021a; USEIA, 2021c, 2022a,b). The changing landscapes put into human perspective by Freese (2003) proposed coal’s world-changing power, which fueled economies and shaped societies, now threatens it by dangerously warming our global climate.

Fig. 1.1

Fig. 1.1 Histogram chart showing electric power generation and carbon dioxide emissions from 1990 to 2020 in the United States. Electric power generators used fossil fuels (coal, natural gas and petroleum, nuclear, and renewables). Black line is total emissions (right axis). MMT CO 2 Eq. = Million metric tonnes of carbon dioxide equivalents. Adopted from USEPA (2021a).

Fig. 1.2

Fig. 1.2 Histogram chart of the 2009 carbon dioxide emissions from fossil fuel combustion and geothermal by fuel-consuming economy sectors and fuel types. MMT CO 2 Eq. = Million metric tonnes of carbon dioxide equivalents. Adopted from USEPA (2021a).

Despite the landscape changes in coal and coalbed gas in the advanced economies, they remain valued fuel energy resources in developing and emerging economies in the Asia-Pacific region as forecasted in Chapters 1 and 10 in the first edition. As predicted, many countries, especially in the Asia-Pacific region, rely on affordable coal to fuel socioeconomic development, sustain industrial output, and maintain national energy security (IEA, 2021a, b). During the past decade, continued retirement of low-efficiency, subcritical coal-fired power plants in member nations of the Organizations of Economic Cooperation and Development (OECD) saw a decrease in power generation from coal from 20 to 60 Terawatt hours (TWh) in 2018 in Europe and U.S. (Bahar et al., 2019; USEPA, 2021a). Yet, global coal electric power generation increased 3% yearly from 2017 to 2019 remaining firmly in place in the near term as the largest source of power at 38% of overall generation, although this is a slight drop from 2013, but rebounded to >40% in 2020–21 (Bahar et al., 2019; IEA, 2019a, 2021a). USEIA (2021a) projected from 2020 to 2050 reduced coal share of electric power generation of OECD by <10% and non-OECD by about 25% (Fig. 1.3).

Fig. 1.3

Fig. 1.3 Line chart showing historical (2010−20) and projected (2020–50) coal share of electric power generation for the Organizations of Economic Cooperation and Development (OECD) countries and non-OECD countries in the Asia-Pacific region. Modified from USEPA (2021a).

Although there is a call for immediate cessation of coal consumption and production, this does not appear to be the case, especially so in the non-OECD developing and emerging countries (China and India) of the Asia-Pacific region projected from 2020 to 2050 (Fig. 1.4) (USEIA, 2021a). In 2017–18, power generation sourced from coal increased 5% in China, 5% in India, and 8% on average for Southeast Asian countries (e.g., Indonesia, Malaysia, Philippines, Vietnam) (IEA, 2017, 2021a, b; Bahar et al., 2019). Coal demand increased 5%–16% in 2021 in China and India, respectively, driven by post-COVID stimulus (IEA, 2021a). According to BP (2022), coal consumption from 2020 to 2021 increased in China from 82.38 to 86.17 exajoules and in India from 17.40 to 20.09 exajoules. China and India consumed twice the amount of coal as the rest of the world with China accounting for over half of the world’s demand, which is being propped up by the high price of natural gas and Ukraine-Russia conflict (IEA, 2022a). These six Asia-Pacific countries account for 44% of the world’s total population, and like most nations, their continued growth is dependent on affordable electricity generation. If coal reserve is cost-effective, both by being profitable to mine and affordable to consumers, it will remain in high demand in these countries (USEIA, 2021d). According to USEIA (2021b), the price of coal in the U.S. from 2010 to 2020 depends on the end-use sector with feedstock for coke plants the highest average price ($154–$127/short ton) and coal-fired power electricity generation plants the lowest average price ($44–$36/short ton) (Fig. 1.5). Other countries in the Asia-Pacific region as well as East Europe and South America (e.g., Balkans, Brazil, Chile, Mexico, Pakistan, Poland, South Korea, Taiwan) recorded significant imports of coal, and Japan and Thailand are also very close to historical highs of coal imports (IEA, 2017, 2019a). The coal is primarily used for electric power generation and secondarily for industrial use producing coke for steelmaking and other metallurgical applications (Fig. 1.6). For the period 2016–18, Asian countries account for 75% of global metallurgical coal trade driven by demand in China and India (IEA, 2019a; USEIA, 2021a). The global metallurgical coal consumption and production are dominated by China and India from 2020 to 2050, but by 2025, production is forecasted to be overtaken by Australia (Fig. 1.7) (USEIA, 2021a). Thus, although IEA (2019a) predicts an overall collapse in coal-fired electricity generation in the advanced economic countries, coal use shifted to non-OECD Asia-Pacific region and other developing and emerging countries (Figs. 1.3 and 1.4) (IEA, 2021a; USEIA, 2021a). Global coal-fired capacity increased slightly to 20 gigawatt (GW) in 2020 followed by a strong rebound of coal-fired power generation in 2021 driven by rise of natural gas prices in the United States and Europe and greater economic activity in China (IEA, 2021c). According to IEA (2022a), coal consumption worldwide rebounded by 5.8% in 2021 spurred by higher natural gas prices and a recovering global economy from the COVID pandemic accompanied by an increase of carbon dioxide (CO2) emissions by 6%.

Fig. 1.4

Fig. 1.4 Chart showing historical (2010–20) and projected (2020–50) world coal consumption and production for the Organizations of Economic Cooperation and Development (OECD) countries (e.g., United States and Europe) and non-OECD countries in the Asia-Pacific region (e.g., China and India). BST = Billion short ton; BT = Billion tonnes. Modified from USEIA (2021a).

Fig. 1.5

Fig. 1.5 Line chart showing the coal price trends by end-use sectors from 2010 to 2020 in the U.S. End users include electric power (coal-fired power plants), other industrial (combined heat-and-power and small industrial electricity-only plants), commercial/institutional (combined heat-and-power and small industrial electricity-only plants such as hospitals and universities), and coking plants. Adopted from USEIA (2021b).

Fig. 1.6

Fig. 1.6 Histogram chart showing historical (2010–20) and projected (2020–50) world coal consumption and production for thermal and metallurgical uses. BST = Billion short tons; BT = Billion tonnes. Modified from USEIA (2021a).

Fig. 1.7

Fig. 1.7 Histogram charts showing historical (2010–20) and projected (2020–50) world coal consumption and production for metallurgical use by the Organizations of Economic Cooperation and Development (OECD) countries (e.g., United States and Europe) and non-OECD countries in the Asia-Pacific region (e.g., China and India). BST = Billion short tons; BT = Billion tonnes. Modified from USEIA (2021a).

Coalbed gas, also known as coalbed methane (CBM) and coal seam gas (CSG), remains an important unconventional gas (CBM/CSG, shale gas, and tight gas) economically produced from shallow surface wells from unminable coals (Nuccio, 2000; Flores, 2014; USEIA, 2016a; Mastalerz and Drobniak, 2020) and a part of the global demand for natural gas (Fig. 1.8). Coalbed gas is a cheap alternative of conventional natural gas exploited from widely distributed, large coal resources found at shallow depths and used by a wide variety of consumers and industries. The increasing demand for clean energy such as conventional and unconventional gases with the former gas proved reserves determined to be with a shorter life span than the latter gas (Breeze, 2016) is key to the growth of coalbed gas. Coalbed gas is forecasted to increase 1.6% annually through 2022 and beyond (USEIA, 2016a; IEA, 2019a). Coalbed gas production in OECD countries declined or plateaued led by the U.S., which dropped >28 Bcm from peak production of 56 Bcm in 2008 to 2017 and continued dropping to 23 Bcm in 2020 (Cardott et al., 2019; USEIA, 2021e) because of governmental regulations and low gas prices, the latter of which has been driven by an abundant supply shale gas (Fig. 1.9) (USEIA, 2016b; Ahmed and Rezaei-Gomarisa, 2019; IEA, 2019a,b).

Fig. 1.8

Fig. 1.8 Histogram chart showing 2012 and projected 2040 production of conventional (other natural gas) and unconventional (e.g., coalbed, shale, tight gases) gas types in China, Canada, and United States. Coalbed gas (CBM) production in China increases fivefold that of Canada in 2040. The United States decreases in 2040. Tcf = Trillion cubic feet; Tcm = Trillion cubic meters. Modified from USEIA (2016a).

Fig. 1.9

Fig. 1.9 Histogram chart of coalbed gas (CBM) production in the United States, which decreased from 2008 to 2017 and lost >23 Bcm. Bcf = Billion cubic feet; Bcm = Billion cubic meters. Modified from Cardott et al. (2019).

Chapter 9 (Worldwide coalbed gas development) of the first edition of this book described coalbed gas basins in the U.S., which have since matured in terms of production history and depletion of reserves. However, many potential producing coalbed gas basins in non-OECD member countries (e.g., China, India, Indonesia, Mongolia, Colombia, Southern Africa) have not matured, attributable to a lack of exploration and pilot phase developments, although China, in particular, is hindered by low permeability coal reservoirs, which impedes extensive development. Chapter 9 of the first edition also pointed out that commercialization of coalbed gas basins, mainly in OECD countries, was successful despite difficulty in coal reservoir characterization and hampered by environmental, legal, and social regulations from State/Province and Federal governments. Understanding the barriers experienced by OECD countries could help drive growth of coalbed gas development in non-OECD member nations, which may be not as strictly regulated. Another key factor in growth of coalbed gas (including coalmine methane or CMM) is energy security and economic sustainability particularly in countries with coal resources, which rely on natural gas imports that are expensive to sustain. A move from coal utilization for power to coalbed gas, which has a lower carbon footprint, also helps these developing countries comply with climate policies of the 2015 Paris Agreement (UNFCCC, 2016). Within the context of global climate change policies, both OECD and non-OECD countries that are endowed with coal will have to evaluate the economic advantages and prospects of production of gas from coal as a cheaper alternative to conventional natural gas (Kopalek, 2014; Schultz and Adler, 2017).

Since publication of the first edition of this book from 2014 to October 2022, approximately 155 out of 339 (46%) research papers were published in the International Journal of Coal Geology (IJCG) on coalbed gas and coalmine methane in Chinese coal and coal basins (Based on Scopus database of IJCG). Publications during this period mainly focused on coal reservoir characterization (e.g., pore structures/sizes/distribution, fracture systems, permeability, adsorption/diffusion, gas flow). Publications on coalbed methane and coalmine methane in the IJCG peaked to 60 papers in 2014, declined to 17 papers in 2021, and increased to 21 papers in October 2022. According to Luo et al. (2017), most of the research papers published in the IJCG and other international scientific publications after 2011 originated from the academic institutions in China. Active investigations range from coalbed gas basin analysis, exploration, production, coal reservoir characterization, enhanced coalbed gas recovery (using CO2) and/or nitrogen (N2) injections, analysis of formation water (e.g., characterization of groundwater systems) and sandstone-stratigraphic-structural traps for coalbed gas (Luo et al., 2017). This level of research and development (R&D) reflects the importance of coalbed gas in China, which has lagged that of the U.S., Canada, and Australia in the past few decades. The intense R&D on coalbed gas in China reflects the survey of geoscientists worldwide by Ruppert et al. (2021), which found a bright future of coal in China and Indonesia and a bleak future in Western advanced economies with Europe the bleakest.

As of 2013, the U.S. is the largest (62%) producer globally of gas from coal reservoirs followed by Canada (12%) and Australia (11%). About one-third of the Australian exported liquid natural gas (LNG) is sourced from coalbed gas destined for markets in the Asia-Pacific region, primarily China, Japan, and South Korea. The rapid growth of China’s natural gas demand has outpaced growth of the domestic production resulting in the concerted efforts of research and increased exploitation of coalbed gas. China has the fourth largest proved coal reserves in the world but was the top consumer (54.3% share) and producer (50.7% share) of coal in 2020 (BP, 2021). With this high level of resource and mining, much of it in high rank (e.g., anthracite) coal, gas, in the form of CMM, is also a substantial resource (Qin et al., 2018). When CMM and coalbed gas resources are combined, it makes China the largest resource of unconventional gas in the world (Flores et al., 2019). USEIA (2016a) has projected China to produce 113 Bcm of coalbed gas by 2040, which is a fraction of the estimated resource of 37 Tcm.

The expansion of coal use in the Asia-Pacific region offsets the contraction in Western Europe and the U.S. (IEA, 2021a). However, the near-term predicted growth of global coal demand could be affected by several factors including (a) climate change policies and perceptions, (b) phase-outs of coal-fired power generation, (c) lower conventional gas prices, and (d) steady expansion of renewable energy. Undoubtedly, these competing factors will continue to shrink the role of coal power generation especially in countries with advanced economies. However, for any substantial shrinkage of global coal power generation to occur would depend on China, which is estimated to have between 67% and 59% of all global coal generation in the 2018–24 period (IEA, 2019a). China views its ownership and use of coal resources fundamental to ensure economic/energy security. If power generation from coal is to continue in the Asia-Pacific region, it will be essential that it is performed in a manner that is compliant with global climate policies to reduce carbon dioxide (CO2) emissions. This could be done through uptake High-Efficiency Low-Emission (HELE) coal-fired power plants fitted with Carbon Capture, Utilization, and Storage (CCUS) systems. China has already built substantial numbers of ultrasupercritical HELE coal-fired power plants since 2010 (Fig. 1.10) (Li and Yu, 2016; Wiatros-Motyka, 2016; Zhu, 2016; Yu et al., 2019; Cui et al., 2021; Wei et al., 2021). Cui et al. (2021) suggest that for China’s strategy of phase-out of coal power plants to meet the net-zero carbon emissions is to retire subcritical to supercritical plants first by 2045. The ultrasupercritical plants (>600 and 1000 MW) are then retired last by 2055, which make up about 50% of the total 1037 plants in China. It is proposed that the HELE ultrasupercritical plants be fitted with CCUS systems to increase efficiency with each increase of efficiency resulting in 2%–3% reduction of CO2 and other air pollutants (IEA, 2017). To have a realistic impact on emissions, China’s coal consumption must also be combined with CMM predrainage methane capture through advanced drilling technologies (Flores et al., 2019).

Fig. 1.10

Fig. 1.10 Histogram chart showing changes in total capacity of coal-fired power plants in China from 1970 to 2016, which include 51% subcritical, 29% supercritical, and 20% ultrasupercritical units. About 87% were built since 2000 with more HELE (ultrasupercritical units) added to the fleet since 2010. MW = Megawatt. Modified from Wiatros-Motyka (2016).

The synopsis of global sea changes on the development, production, consumption, and utilization of coal and coalbed gas in response to climate change policies has become a driving force in a transformational low-carbon-based world. To attain these goals, however, the world requires multidisciplinary research and development with a wide range of disciplines to provide solutions for sensible use of coal and coalbed gas.

Approach to multidiscipline book

Strategy

The structure of the book is composed of objectives, scope, and vision statements, and these are molded by the scale and complexity of the topics needed to ensure a full understanding of coal and coalbed gas. Finally, the depth and breadth of each topic are guided by the controversy behind coal and coalbed gas as a combustible material and its resulting carbon emissions. To understand coal and coalbed gas, a multidisciplinary approach is required (Fig. 1.11). This book strives to provide a holistic educational approach to coal science and coalbed gas technology, which integrates and utilizes concepts, data, interpretations, techniques, tools, and results from various disciplines to improve the learning process and information transfer.

Fig. 1.11

Fig. 1.11 Flow chart showing the multidisciplinary relationship of coal and coalbed gas to applications in research and development (R&D) in academia and industry, which also apply to governmental activities. The R&D on the materials properties of coal for nonfuel uses are applicable to academia, industry, and government. Adopted from Flores (2014).

The auxiliary strategy is guided by the constraints put on coal use by climate policies (UNFCCC, 2016) in a new low-carbon-based world. Consequently, the book’s full scope covers everything from peat to pipeline, environmental impacts from development to utilization, and global changes affecting coal/coalbed gas consumption to outlook of these resources in a new low-carbon-based world. Most important, the book covers novel innovative nonfuel usage of coal and revisits solutions and progress in technologies to reduce GHG emissions. This inclusive science-technology-environment strategy distinguishes it from other books, which are mainly focused on trends in coal science (e.g., chemistry, petrology, and geology), mining, production, processing, and utilization or coalbed gas engineering and technology (e.g., drilling, power generation, environmental, and production). A distinguishing feature of this book is that it treats these topics as both interdependent and interconnected aspects of energy resources.

Objectives

This book has three objectives that aim to improve and modernize the first edition. The first objective of the book is to update the first edition, primarily to integrate changes that GHG emission and climate change policies have had and may have on the development and utilization of coal and coalbed gas. This objective focuses on new developments on global demand, supply, consumption, and utilization of coal and coalbed gas as affected by politically evolving but mostly more rigorous environmental regulation. Another focus of this initial objective is to assess the novel roles that coal and coalbed gas can play as science (e.g., coal bioconversion, characterization, gasification, liquefaction, methanogenesis, nano-carbon materials, and utilization) and technology (e.g., mining, drilling, power generation systems, and coal-to-chemicals) enable the world to transition into a low-carbon-based world. Already worldwide repositioning of research and development of coal and coalbed gas has focused on addressing drilling, drainage, capture, and utilization technologies to reduce GHG emissions. For coal as a source of gas, this is achieved by bridging the complex interplay of source and reservoir through comprehensive understanding of its biological, chemical, and physical properties, which are co-dependent with gas generation, storage, and flow in the reservoir. Coal is a biologically, chemically, and physically unique unconventional gas reservoir almost totally composed of organic matter, which is different in characteristics by serving as the source of gas compared to conventional natural gas reservoir rocks. Also, gas generated in the coal migrates and is stored in adjoining epiclastics such as porous sandstones (Fig. 1.12). Coals, epiclastics (e.g., mudstones, shales, siltstones, sandstones, and conglomerates), and precipitates (e.g., limestone, chert) (Fig. 1.12) are commonly interbedded in layers of coal-bearing strata, historically referred to as coal measures (Conybeare and Phillips, 1822; White, 1891). Coal measures worldwide consist of abundant, thick, genetically related (e.g., depositional environments) coal-clastic-precipitate strata, which are vertically stacked and laterally juxtaposed making them ideal biogenic coalbed gas-enriched reservoirs for development (Rice and Flores, 1989, 1991; Flores, 2003, 2004; Flores et al., 2004). A final focus of this initial objective is to demonstrate how peat is altered throughout the geological cycle. Over and above being a commodity, coal and coalbed gas give vital clues to our Earth’s history. Understanding the epigenetic and diagenetic stages from peat to coal alteration by heat and pressure informs us about basin form, their tectonics, and paleoclimates (including past CO2, O2, temperature, and rainfall) as well as paleobotany and plant evolution.

Fig. 1.12

Fig. 1.12 Flow chart showing the hierarchy of sedimentary rocks divided into detrital and chemical rocks, which in turn, is subdivided into the clastic, organic, and precipitate types. These rock types make up coal-bearing sedimentary rocks or Coal Measures strata, which compose coal-sandstone reservoirs enriched in coalbed gas. Adopted from Flores (2014).

The second objective is to raise awareness of coal properties, both as a combustible material and a gas reservoir, which starts with knowledge of precursor peat and its depositional systems. Paleogeographic and paleoclimatic conditions influence how much coal and coalbed gas are formed with the results seen as the present geographic distribution. The quantity of coal resources influences the exploitation and development of coalbed gas. The quality of these energy-resource endowments is controlled by depositional and geological settings, which affect coal utilization and coalbed gas recovery. Focusing on quantity and quality of coal and coalbed gas resources highlights certain countries possessing more endowments than other countries. This imbalance creates a comparative advantage for countries with abundant coal and associated coalbed gas resources, which influences industrial and economic opportunities as well as fosters national energy security.

The third objective of the book links the future of coal and coalbed as an essential energy resource with its consumption and utilization having a direct influence on global economic growth and national security but posing challenges through environmental and climate impacts. Resolution of these challenges may be mitigated through deployment of multiple advanced technological pathways toward environment-friendly development appropriate in a new low-carbon-based world. This includes a focus on emerging nonfuel use of coal, which would alleviate GHG emissions. Nonfuel application of coal would satisfy the need for energy security and economic growth in coal resource-rich countries such as China. Refocusing R&D of nonfuel use of coal could advance the world’s new carbon products (e.g., carbon nanotubes, graphene sensors, graphite, carbon nanofibers) (Ye et al., 2013; Powell and Beall, 2015; NCC, 2019). Similarly, extraction of rare earth elements (REEs) found in coal and coal-related byproducts advances nonfuel use of critical minerals in coal resource-rich countries such as the U.S., the supply of which is monopolized by China (NETL, 2018; NCC, 2019).

Scope and chapter descriptions

The scope is encapsulated by the title of the book: Coal and Coalbed Gas. A common definition of coal is: a black to brownish-black, combustible rock composed of high carbon and hydrocarbons contents. The hydrocarbons mainly include coalbed gas in the form of methane. By definition, coal and coalbed gas are mutually inclusive with overlapping characteristics and properties. Thus, the scope is shaped by the interrelationship of coal and coalbed gas, and its organization for presentation in the book is fashioned by their co-dependent and closely linked occurrence as a gas source and reservoir.

The book is divided into 11 chapters and organized in a way to take the reader through the whole life cycle of coal and coalbed gas. Each chapter is peer-reviewed.

(1)This, the first chapter, overviews the current state of coal and coalbed gas in a carbon-conscious world. Since the 2015 Paris Agreement, policies influencing fossil fuels, especially coal and to a lesser though still significant extent, gas, are on current use and future development. These policies are driving research by countries into how coal can be utilized in nonfuel, alternative applications. This global awareness of climate change and impacts of fossil fuel use underscores the objectives, scope, vision, and principles of this book.

(2)Chapter 2 characterizes coal’s multifaceted roles as petroleum sources indicated geologically, paleodepositionally, geochemically, paleobotanically, and paleogeographically. These indications are used worldwide to exploit for generative potential, origin, and economic accumulations of petroleum and coalbed gas in coals and sandstones of coal measures. Coalbed gas is known since 1800 as coal gas, town gas, and water gas, which occurs as coalmine methane (CMM) and abandoned mine methane (AMM) requiring control management. The multifaceted fuel uses of coal and coalbed gas range from gasified to liquefied synfuels. The technologies of coal gasification-based liquid fuels (CTG) and liquefaction-based fuels (CTL) are widely practiced in China and taking a foothold in countries with small economies and no petroleum but rich in coal resources. Synfuels from coal have gained traction in R&D of emerging cleaner energy in response to the net-zero carbon emissions policy.

(3)Chapter 3 covers the geologic settings and geographic occurrences of coal and coalbed gas resources worldwide. Coal-bearing rocks, often referred to as coal measures, are chronostratigraphically partitioned geologically, biologically, biochemically, ecologically, and paleoclimatically. These factors are directly linked to the appearance and evolution of terrestrial plants that comprised the vegetation in peatlands, which are coal precursors. The coal occurrences during the Phanerozoic geologic timescale are episodic peaks of coal packages separated by coal gaps and plant extinctions overprinted by replacements of ancestral gymnosperms by modern angiosperms. The geographic locations of the Paleozoic- and Mesozoic-age coals are mostly in relatively large- to medium-size basins and Cenozoic-age coal in small-size basins. These coal basins are unevenly distributed across major continents, microcontinents, and islands, which controls how countries are endowed with most-to-least coal and coalbed gas reserves/resources. The most endowed countries established the classification systems to assess coal resources.

(4)Chapter 4 examines the depositional environments under which peat forms and how that influences the chemical and physical properties of the resultant coal. The properties of coal, and coalbed gas, all begin with the conditions of the original peat formation and thus have a major influence on how, ultimately, the coal and coalbed gas are later used. The accumulation of peat is governed by biological, ecological, geochemical, hydrological, and physical processes, all of which are influenced by the depositional system that it forms within. Moreover, these processes differ depending on the geographic and climatic setting the peat forms within and finally what the peat is subjected to during burial and coalification.

(5)Chapter 5 presents concepts of coal composition, both in terms of the organics, which are commonly referred to as macerals, and inorganic matter, that is, minerals. Macerals are derived from a variety of sources, including roots, leaves, charcoal, fungi, spores/pollen, and other material from humic decomposition while minerals can be plant-, waterborne-, and airborne-derived material. The proportions of maceral types and inorganic material control combustibility and reservoir properties (porosity, permeability) of coal. Minerals have a generally negative effect on the combustibility of coal and on gas flow in a coal reservoir. The relationship of reservoir properties and macerals is the basis for coal reservoir characterization of different ranks and depths.

(6)Chapter 6 discusses the effects of temperature, pressure, and time on the coalification of peat into coal during burial. Syngenetic and diagenetic processes result in coals of different chemical and physical properties, which in turn control the quality, combustibility, hydrocarbon generation, and types of coalbed gases (biogenic and thermogenic). Coalification influences coalbed gas generation, adsorption capacity, and gas storage as well as gas migration (flow) and entrapment. Hydrocarbons are generated at different stages of coalification with thermogenic gas and oil expulsion formed at high temperature. Biogenic gas is generated during peatification, early-stage burial, as well as post coalification.

(7)Chapter 7 reviews assessment methods for both coal and coalbed gas. An estimate of uncertainty should always be made for any resource and reserve. Uncertainty can be influenced by a number of factors when estimating coal resources including structure, seam continuity, correlation errors, data density, and measurement errors, among other parameters. Assessment methods for coalbed gas also use estimates of coal bed volume in addition to the amount of gas. Again, uncertainty must be estimated for gas resources and reserves. Gas resources are determined through various methods including direct desorption measurements, production data (eventual ultimate recovery or EUR), material balance, or indirectly through application of analog data. Deterministic and probabilistic assessments of gas uncertainty are attached to the estimates. Finally, active and abandoned coal mine methane gases (CMM and AMM) are assessed based mainly on gas production from in-mine boreholes and emissions in coal mines.

(8)Chapter 8 reviews the technology applied to the exploration and development of coal and coalbed gas. Technological improvements in drilling, well completion, stimulation, logging, and gas gathering have advanced the efficiency of coalbed gas. Drilling has evolved from vertical to horizontal gas drainage when gas flow is enough to payback the extra expense. Multiple slant hybrid wells from a single drill pad have also been employed. In addition, completions in multiple seams employing either vertical or horizontal wells are common. Multilateral horizontal wells have also increased recovery of coalbed gas over larger drainage areas. Completion and stimulation technologies, such as hydraulic fracturing, have also been developed that enhance gas flow. A similar trend in technology development has been duplicated in coal mines where in-seam drilling has evolved from short auger drills to long directional horizontal drilling in order to predrain (prior to mining) gas and increase recoverability.

(9)Chapter 9 considers how groundwater systems and their hydrological dynamics (e.g., flows, infiltration, recharge, storage) directly affect generation, distribution, and production of coalbed gas in coal measures. Hydraulic connectivity of coals and related aquifers such as adjoining sandstones controls groundwater withdrawal during coalbed gas production. Large volumes of groundwater are extracted during coalbed gas production, which depletes the groundwater supply in water-risk regions. During mining of coal, groundwater is also extracted and sometimes in such significant proportions that the mine, or group of mines, changes the pressure dynamics of a basin to such an extent that coalbed gas reservoir properties are affected by large-scale drawdowns. These changes can affect coal reservoir properties, gas producibility and recoverability, and thus the economic viability of a play. Whether co-produced groundwater can be managed as either a waste product or put to beneficial use is usually dependent on water quality and quantity, legal and regulatory issues, permitting constraints for discharge and use, local environment and climate, as well as economic considerations. More importantly, groundwater surface meteoric water recharge plumes influence formation of late-stage biogenic coalbed gas in basin margins. As groundwater flows away from the source of recharge, interactions between water, aquifer/aquiclude minerals, and microorganisms change the ionic composition of the groundwater. For example, oxygenated recharge water initially provides sulfates from oxidation of pyrite in the coal, but its abundance changes along the groundwater flow paths, which in turn control methanogenesis. Thus, groundwater is crucial to generation and production of biogenic coalbed gas as well as a key to biostimulation and bioaugmentation of subsurface coals for commercial development of neobiogenic coalbed gas.

(10)Chapter 10 revisits the worldwide coalbed gas production, which increased and peaked from the 1980s to 2008–10, then decreased significantly to the present in the United States (U.S.) and Canada. The U.S. coalbed gas production precipitously declined 58% from 55.7 to 23.2 Bcm through 2008–20 resulting in thousands of abandoned, idled, and orphaned wells. The San Juan, Raton, and Powder River Basins still produce coalbed gas but well below full capacity. Canada’s coalbed gas production peaked at <9 Bcm in 2010 and declined to >7 Bcm in 2014. Low U.S. natural gas prices from $12.69–$1.63/MMBtu through 2008–20, emerging shale gas production from 56 to 805 Bcm through 2007–20, and disinvestments caused the fall of coalbed gas production. These economic factors controlled the upsurge of coalbed gas production from the 1980s to 2008–10. Government directives impaired coalbed gas development in China, India, and Indonesia. Coalbed gas development was setback by global climate change policies targeting net-zero carbon emissions (NZCE) by 2050. The global climate factor is the main driver of the fate of coalbed gas from the present through the 2050