Energy and Climate Change

An Introduction to Geological Controls, Interventions and Mitigations

Michael Stephenson

• Publisher: Elsevier
• Year: 2018
• Print ISBN: 9780128120217
• eBook ISBN: 9780128120224
• Topic: Physical Sciences
• Subtopic: Environmental Science

Energy and Climate Change: An Introduction to Geological Controls, Interventions and Mitigations examines the Earth system science context of the formation and use of fossil fuel resources, and the implications for climate change. It also examines the historical and economic trends of fossil fuel usage and the ways in which these have begun to affect the natural system (i.e., the start of the Anthropocene). Finally, the book examines the effects we might expect in the future looking at evidence from the "deep time" past, and looks at ways to mitigate climate change by using negative emissions technology (e.g. bioenergy and carbon capture and storage, BECCS), but also by adapting to perhaps a higher than "two degree world," particularly in the most vulnerable, developing countries. Energy and Climate Change is an essential resource for geoscientists, climate scientists, environmental scientists, and students; as well as policy makers, energy professionals, energy statisticians, energy historians and economists. - Provides an overarching narrative linking Earth system science with an integrated approach to energy and climate change - Includes a unique breadth of coverage from modern to "deep time" climate change; from resource geology to economics; from climate change mitigation to adaptation; and from the industrial revolution to the Anthropocene - Readable, accessible, and well-illustrated, giving the reader a clear overview of the topic

Chapter 1

The Carbon Cycle, Fossil Fuels and Climate Change

Abstract

Geological science offers a unique way of looking at the relationship between energy and climate change. The neatest way to see this connection is through the carbon cycle—the path that carbon takes through the atmosphere, biosphere and geosphere—and to see the limits to that cycle, and the controls on its rate and character that are subject to natural fundamental laws. These laws can be modelled through the new discipline of Earth system science, revealing the extent to which life in all its forms interacts with other big forces to change the world. This is best illustrated in how the carbon cycle is at the centre of the tension between our use of energy and the atmosphere, and the geological generation of much of the fossil fuels we use to generate power. Carbon leaves the atmosphere largely through the engine of life, including biological pumps operating in the ocean. In a permanent form below the surface of the Earth, essentially as fossil fuels like coal, gas and oil, this carbon can do no harm. Of course, carbon can also leave the rocks and get back into the atmosphere. For example, carbon dioxide is released during the metamorphism of carbonate rocks when they are subducted into the Earth's mantle, or by volcanoes. But it is humankind's intervention in the carbon cycle, a short cut within this large geological part of the carbon cycle, which is causing the problem: the burning of fossil fuels.

Keywords

Carbon cycle; Carbon sequestration; Climate change; Earth system science; fossil fuel combustion; fossil fuel formation

Contents

• The Carbon Cycle
• How Fossil Fuels are Formed
  • Coal
  • Oil and Natural Gas
  • Methane Hydrates
• Carbonate Rocks
• How Fossil Fuel Formation and Combustion Change Climate
  • Geological Sequestration and Climate
  • Combustion and Climate Change
• Summary
• Bibliography

A lot of us are now familiar with the famous photograph taken of the Earth on February 14, 1990 by the Voyager 1 space probe from a distance of 6 billion kilometres. In the photograph, the Earth appears as a pale blue dot against the blackness of space. During a lecture at Cornell University in 1994, the cosmologist Carl Sagan showed the image to the audience and contemplated the deeper meaning of the pale blue dot, in relation to the ultimate negligibility of humankind against the vastness of space. But the pale blue dot also helps us to realise the physical, chemical and biological boundaries that limit our planet. Most of the processes that I talk about in this book have limits, rates and thresholds that are governed by a system. The science of this is called Earth system science. It is fairly new and it is very interdisciplinary, using elements of geology, physics, chemistry, biology and mathematics.

One of the most interesting early findings of Earth system science is the extent to which life in all its forms interacts with other big forces to change the world. In a sense, the tension between our use of energy and the atmosphere and the geological generation of much of the fossil fuels we use is one of the best demonstrations of the way in which life interacts with other big forces, as I hope you will see. This is a unique geological way of looking at the problem of energy and climate change.

The Carbon Cycle

Geologists were amongst the first to recognise that life has had a powerful role in shaping the Earth. James Hutton, one of the founders of geology, described the Earth as ‘…not just a machine but also an organised body, as it has a regenerative power…’ The Russian geologist Vladimir Ivanovich Vernadsky was one of the first geologists to hypothesise that life is a geological force that shapes the Earth, suggesting that the oxygen, nitrogen and carbon dioxide in the Earth's atmosphere result from biological processes. During the 1920s he published works arguing that living organisms could reshape the planets as surely as any physical force.

At the heart of climate change and energy is the carbon cycle, which involves exchange of carbon between ‘stores’ or accumulations in the atmosphere, terrestrial biosphere, oceans, and the subsurface of the Earth (Fig. 1.1). The rates of exchange and the sizes of the stores are instrumental in the ability of the Earth to sustain life. The carbon cycle also interacts with other very large cycles of oxygen, water, phosphorous and nitrogen in complicated ways that are difficult to model and predict.

Fig. 1.1 The carbon cycle. On the left side photosynthesis creates organic matter that collects in sediments (carbon burial or capture). This carbon can remain out of the atmosphere for a very long period locked away in rocks for millions of years. But eventually the carbon can be returned through weathering of exposed rock. It can also—through subduction at plate tectonic boundaries—become part of the mantle. The mantle might return it through volcanoes. (From Berner, R., 2003. The long-term carbon cycle, fossil fuels and atmospheric composition. Nature 426, 323–326.)

In a book purely about climate change, the main parts of the carbon cycle story would be concerned with the first three of the stores: the atmosphere, terrestrial biosphere, and oceans, but in this book the addition of energy means we need to look at one in detail: the deep Earth, which supplies human society with most of its energy and fuel.

Broadly this last part of the carbon cycle is geological rather than atmospheric or biological. It is distinct in that it operates over very long periods—millions or tens of millions of years. These time periods may seem academic to human society, but in fact are the periods that are needed to accumulate carbon such as coal, gas or oil—and in the long run also affect the amount of carbon dioxide in the atmosphere and therefore climate.

Though the immediate non-geological exchange of carbon is most important to climate change on human timescales, most of the Earth's carbon is actually stored below the surface (Table 1.1); and a lot of this resulted from living things at the surface, either directly or indirectly. Eighty percent of this is limestone (sedimentary carbonate), from sedimentation from seawater of calcium carbonate or shells, and the rest is organic matter from buried dead organisms. We will look at the way that carbon makes its way from the ‘living world’ into the rock in the next section.

Table 1.1

Stores of Earth carbon. The big stores are in the lithosphere (the rocks)—sedimentary carbonates and kerogen

Pool	Quantity (gigatons)
Atmosphere	720
Oceans (total)	38,400
Total inorganic	37,400
Total organic	1000
Surface layer	670
Deep layer	36,730
Lithosphere
Sedimentary carbonates	> 60,000,000
Kerogens	15,000,000
Terrestrial biosphere (total)	2000
Living biomass	600–1000
Dead biomass	1200
Aquatic biosphere	1–2
Fossil fuels (total)	4130
Coal	3510
Oil	230
Gas	140
Other (peat)	250

Source: Wikipedia retrieved July 2017.

But before that we need to investigate the surface parts of the carbon cycle. The exchange of carbon between the atmosphere and the land is largely a biological process with plants photosynthesising to make carbon compounds, and aerobic respiration releasing it again—though fires can also do this. The exchange between the atmosphere and the sea involves chemical processes such as dissolution and marine photosynthesis working as solubility and biological ‘pumps’ that take carbon from the atmosphere mostly to the deep ocean. Marine animals that produce shells also extract carbon from seawater to allow calcium carbonate to lock up carbon in the long term. Also long term is the process of silicate weathering on land where rocks containing silicates take up carbon dioxide to produce calcium carbonate and SiO₂.

Carbon can leave the rocks in several ways. Carbon dioxide is released during the metamorphosis of carbonate rocks when they are subducted into the Earth's mantle. This carbon dioxide can be released into the atmosphere and ocean through volcanoes. It can also be removed from rocks by humans through the burning of fossil fuels.

How Fossil Fuels are Formed

As I have already indicated, fossil fuels are forms of organic carbon in sedimentary rocks, mainly coal, oil and natural gas.

It is hard to overemphasise the importance of fossil fuels in modern energy. A quick eyeball of Fig. 1.2 shows the dominance of fossil fuels (coal, oil, natural gas) in primary energy consumption in the world, mainly in transport, heating homes and for generating electricity. Fig. 1.3 shows the importance of fossil fuels in electricity generation alone worldwide. The right-hand side shows that, though t...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Quotation
• Preface
• Acknowledgements
• Note to the Reader
• Chapter 1: The Carbon Cycle, Fossil Fuels and Climate Change
• Chapter 2: Natural Global Warming: Climate Change in ‘Deep Time’
• Chapter 3: Artificial Global Warming: The ‘Fossil Economy’
• Chapter 4: The Coming Industrial Revolution? Fossil Fuels and Developing Countries
• Chapter 5: Geology and the Reduction of Emissions
• Chapter 6: Climate Change Adaptation: Geological Aspects
• Chapter 7: Feedbacks and Tipping Points
• Chapter 8: The Geological Macroscope
• Chapter 9: Energy and Climate Change: Geological Controls, Interventions, and Mitigations
• Glossary
• Conversion Table
• Index