Chapter 1: Introduction

The opening of Calder Hall in 1956,¹  the first commercial nuclear power station in Cumbria, England in 1956, a few years after the coronation of the late Queen Elizabeth II in 1953, ushered in a new age of hope for a better future after the destruction caused by the Second World War. However, technological advances that are taken for granted nowadays, such as magnetic resonance imaging (MRI) scanners, wall-mounted colour TV screens, smartphones, the internet, and social media, were not available in the 1950s. The transistor, a solid-state device invented in 1948 and which acts as a switch, had not yet facilitated the miniaturisation of electronic devices so characteristic of the portable devices of the 21st century. The limited range of electrical goods that were available to households included bulky black and white television sets that contained thermionic valves (also known as vacuum valves) which resembled incandescent light bulbs. The valves generated a lot of heat when in use and were fragile. Vacuum valves such as the diode and triode that were invented by John Ambrose Fleming²  and Lee de Forest²  in the first decade of the 20th century facilitated the introduction of radio broadcasting. Thermal nuclear reactors such as the one at Calder Hall that use slow-moving neutrons (i.e., thermal neutrons) for the fission of uranium-235 also produce fissile plutonium-239 that could be used in a country’s nuclear weapons programme.

Coal was a major fuel for electricity generation and domestic heating in the UK and was pivotal for industrial growth within the UK, where it was a critical material for iron production. At the coal industry’s peak³  in 1913 there were 3024 deep mines that produced 292 million tons of coal and employed 1.1 million miners. Trains and ships were mainly coal-powered well into the 20th century. But coal-fired power stations, as well as blast furnaces for steel production and domestic coal fires, poured out emissions containing CO₂, sulfur dioxide and particulate carbon. Economic growth and the standard of living for people in advanced economies increased throughout the 1950s and 1960s. It was anticipated that nuclear power would provide clean, cheap electricity, but little attention was paid as to how to store highly radioactive nuclear waste over a long time period. Plastics did not play an important role in everyday life and recycling of household waste did not take place. With increasing prosperity came an increasing car ownership, while air travel for overseas holidays became popular and affordable from the early 1960s and remains popular today. The effect of CO₂ emissions from vehicles and aircraft on the climate was not a priority among governments. The discovery of North Sea oil and gas in the 1970s began to displace coal for electricity generation and domestic gas-fired central heating.

The latter became common in millions of households and replaced the use of coal for domestic heating. The emissions of CO₂ from the combustion of natural gas, methane, did not attract publicity among the general public, and was not addressed by governments.

The absorption of radiation, e.g., infra-red radiation by molecules depends on the chemical bonds between atoms in the molecule.^4,5  Absorption can take place into vibrational modes or rotational modes of the molecule, and in the case of CO₂ infrared energy is absorbed by vibrational modes. Note that CO₂ is a linear molecule. Molecules in a gas can undergo translational motion either, in a straight line, or zig-zag trajectory following collisions with other molecules or undergo rotational motion as well as vibrational motion. As energy is absorbed into vibrational modes, the molecular motion increases corresponding to an increased temperature of the gas.

In a later chapter, James Clerk Maxwell, and Ludwig Boltzmann, two giants of 19th century science, are mentioned. They are associated with what is known as the Maxwell–Boltzmann distribution. The latter describes the distribution of speeds among the molecules in a gas. Velocities of individual molecules are not described, whereas statistical analysis is carried out for the properties of large numbers of molecules.

Levels of carbon dioxide, CO₂, in the Earth’s atmosphere have been increasing^4,6–8  in recent centuries due to the use of fossil fuels (oil, gas, and coal) to promote industrial growth, for domestic heating and from around the beginning of the 20th century for electricity generation. At the start of the Industrial Revolution, ca. 1750, levels of CO₂ in the atmosphere were approximately 250 ppm. In 1974, this concentration was 332 ppm, while by 2023 it had risen to 420 ppm. CO₂ absorbs infrared radiation (heat) that is reflected from the Earth’s surface, atmosphere, and clouds so that the radiation does not escape into space. This capture of CO₂ is the cause of global warming, that is, an increase in the temperature of the Earth’s atmosphere and which contributes to climate change.

The terms climate change, climate crisis and climate catastrophe have all been used to describe global warming. CO₂ is known as a greenhouse gas, as are methane, CH₄ and nitrous oxide, N₂O. Nitrous oxide has legitimate uses as an anaesthetic and as a propellant in cans of whipped cream as it is soluble in fats. Nitrous oxide is also known as ‘laughing gas’. However, it is also used as a recreational drug where it is known as ‘hippy crack’, and it is common to see small, empty, metallic containers of the gas on pavements in the UK. The UK government has stated its intention to ban the sale of these small cylinders. The sale and possession of nitrous oxide for recreational use was banned in the UK from 8 November 2023. Nitrous oxide has also been produced as a by-product of the manufacture of nylon from adipic acid. Not all greenhouse gases originate from human activities as methane emissions are produced from livestock in their digestive systems. Other greenhouse gases⁷  include CFC-12 (CCl₂F₂), used in liquid coolants and foams, HCFC-12 (CHClF₂), used in liquid coolants, perfluoromethane (CF₆) used in the production of aluminium and sulfur hexafluoride (SF₆) used as a dielectric fluid. However, these four gases have concentrations in the atmosphere in parts per trillion although two of them have long lifetimes. Thus, the lifetimes for perfluoromethane and sulfur hexafluoride are 50 000 years and 3200 years, respectively. None of these greenhouse gases are naturally-occurring.

A phrase often used nowadays is ‘net-zero’ and this can be explained with the following example. If the occupants of a house consume a certain amount of electricity generated from fossil fuels corresponding to the release of a specified amount of CO₂, and solar panels on the outside of the building transfer the same amount of electricity into an electricity grid, then there is an energy balance corresponding to net-zero. In this book, ‘low-carbon economy’ refers to a situation that approaches net-zero.

The manufacture of ammonia involves the chemical reaction between nitrogen, obtained from air and hydrogen that is made by steam reforming of natural gas, that is methane. However, a by-product of steam reforming is the greenhouse gas, CO₂. If in the future hydrogen is obtained by the electrolysis of water, using electricity derived from renewable sources such as solar or wind power, then no emissions of CO₂ will be produced. Hence, this process will be net-zero for carbon emissions. The replacement of coal-fired blast furnaces by electric-arc furnaces can also reduce emissions of CO₂. If the arcs are supplied with electricity generated from renewable sources, then the steel making process can be net-zero. Electric-arc furnaces are supplied by recycled steel from high-quality scrap, but the quality of the steel produced in an electric-arc is not high enough for automotive and aerospace industries. Blast furnaces use coal and iron ore. The use of hydrogen to replace coal as well as carbon capture and storage technology in the steel industry is being explored. If green hydrogen is used, that is, hydrogen obtained by the electrolysis of water using electricity generated from renewable sources, then the resulting green steel policy can be considered a net-zero process, that is, a process with net-zero carbon emissions. If fossil fuel is burned and the resulting CO₂ is captured and stored for example in rock formations under the sea, then this process is net-zero. In plain language, net-zero can be interpreted as meaning no greenhouse gas emissions.

CO₂ has some interesting physical properties.^4,9 

• At atmospheric pressure CO₂ is a gas but when cooled to −78 °C it freezes into a solid known as ‘dry ice’.

• When dry ice is warmed, the solid becomes gaseous again in a process known as sublimation.

• At a pressure of 73 atm and at room temperature CO₂ forms a liquid. The liquid phase remains up to 31 °C, a temperature known as the critical temperature.

• Above the critical temperature in the presence of applied pressure, CO₂ has the properties of both a gas and a liquid and is known as a supercritical fluid.

• Supercritical CO₂ is used to remove caffeine from coffee beans replacing an earlier method for producing decaffeinated coffee with organic solvents.

CO₂ is soluble in water and a figure of 760 cm³ L⁻¹ of water has been suggested.⁴  The solubility increases with pressure, a property utilised for the production of ‘fizzy’ soft drinks and, of importance when discussing global warming, decreases with an increase in temperature. As the Earth’s atmosphere warms up, heat from global warming is absorbed by the oceans. The average global sea surface temperature¹⁰  reached 20.96 °C on 1 August 2023, a record high since the previous record of 20.95 °C on 29 March 2016. A consequence of the increased ocean temperature is that the solubility of CO₂ in the oceans is reduced so that CO₂ is released into the atmosphere. Since the 1980s, the frequency of marine heatwaves¹⁰  has doubled and there is evidence according to the United Nation’s Intergovernmental Panel on Climate Change (IPCC) that this increase is associated with human activity. The IPCC was set-up in 1988 by members of the World Meteorological Organisation and the United Nations Environment Programme to assess the available scientific information on climate change, and the environmental impact that climate change might have.⁴ 

Although global warming is widely discussed in the public domain nowadays, the effect of greenhouse gases such as CO₂ that are released through human activity on damage to the Earth’s climate was publicised some time ago. In 1991 an Atmosphere Temperature Workshop in the USA issued a warning in this area.^4,11  Since that time, governments have funded research into global warming,¹²  in particular through development of models for climate change using ever more powerful computers. This is a fertile area for predictions and controversy that continues to this day, although there is widespread support that climate change is real and happening in the 2020s.

The International Energy Agency (IEA) has indicated that oil and gas operations account for 15% of greenhouse gas emissions from energy because of flaring and venting during oil extraction. Burning oil and gas in transport, industry, and power production account for another 40% of emissions.

As a result of global warming, governments are moving away from the use of fossil fuels and are replacing them with sources of clean energy from renewable sources such as solar, wind, hydroelectric and geothermal. Nuclear power plants such as small modular reactors that do not emit CO₂ are under consideration. The approach to reduce the dependence on fossil fuels is often referred to as decarbonisation. In the latter process, the aim is to eliminate CO₂ emissions from burning fossil fuels and to move from a high-carbon economy to low-carbon economy. As part of decarbonisation, internal combustion engines in new cars that use petrol or diesel will be banned from sale in the UK from 2030 and replaced with electric vehicles. Decarbonisation is associated with the terms ‘sequestration’ and ‘carbon capture’.

Sequestration refers to trapping CO₂ emissions in underground geological formations. It is possible that geological sequestration will take place in sedimentary basins that are porous and consist of layers of silt, clay, and carbonates such as chalk, calcium carbonate. Several approaches have been considered for capturing CO₂ emissions from power plants that burn fossil fuels.

• Post-combustion capture—here, chemical solvents such as organic amines remove CO₂ from flue gases after which the solvent is regenerated. Post-combustion capture units can be retrofitted to existing plants (see Figure 1.1).

• Pre-combustion capture—the fossil fuel is reacted with steam or oxygen to produce synthesis gas, a mixture of carbon monoxide and hydrogen, after which carbon monoxide is reacted with steam to produce CO₂ and hydrogen. The reaction between carbon monoxide with steam is known as the water–gas shift reaction. The CO₂ undergoes sequestration, while hydrogen is used for electricity generation.

• Oxygen combustion—here, fossil fuels are burned in oxygen, rather than air to generate electricity so that flue gases are mainly CO₂ and H₂O. CO₂ can be separated from water vapour.

Participants at the Government’s Committee on Climate Change in Paris in December 2015 aimed to limit a rise in the Earth’s temperature to 1.5 °C above pre-industrial levels by the end of the 21st century, a reduction from a 2 °C rise that had previously been considered necessary to limit global warming. Whether this restriction to a 1.5 °C rise is achieved remains to be seen. Table 1.1 indicates a timeline for events relevant to global warming. CO₂ concentrations in the atmosphere since around the year 1000 remained constant up to the time of the Industrial Revolution as measured from air trapped in ice cores, and then increased rapidly. The increase in the concentration of CO₂ in the atmosphere since the Industrial Revolution is summarised in Table 1.2. While Table 1.3 indicates activities that contribute to greenhouse emissions.

An example of a carbon capture project was announced by UK Prime Minister Rishi Sunak on 31 July 2023. Here, the scheme known as the Acorn Project at Saint Fergus gas terminal, Aberdeenshire in Scotland involves using existing pipelines to transmit CO₂ from industrial sites under pressure so that it is a liquid. The liquid CO₂ would be stored in porous geological rock structures about one mile beneath the seabed.

Carbon mineralisation is being explored as a way of storing CO₂. In Wadi Lawayni,¹³  a remote desert valley in Oman, a region of rock extends hundreds of metres into the air. This rock, peridotite had formed many kilometres below the surface and is part of the Earth’s mantle. Collisions between tectonic plates forced the wall of stone upwards into the air. The rock contains magnesium and calcium bound up in the minerals olivine and pyroxene. When it rains in Wadi Lawayni the water collects in cracks in the rock. CO₂ dissolved in the rainwater reacts with magnesium atoms forming magnesium carbonate veins throughout the rock. It has been estimated that the rocks are absorbing 100 000 tonnes of CO₂ each year that corresponds to about 1 g of CO₂ per m³ of stone. Acidic carbonated rainwater attacks the rock such as basalt, releasing calcium and magnesium ions into the water that react with the dissolved CO₂ over time to form solid carbonates. The Biden administration in the USA has, under the Inflation Reduction Act, provided tax incentives for carbon capture schemes.

Until recently the phrases critical materials and critical minerals were rarely mentioned in the public domain whether in newspapers, radio, television, or other forms of media. More importantly, these phrases were probably largely unknown among the general public. However, the desire of governments to move towards a clean energy future to mitigate the effects of global warming has pushed the availability of critical materials up the political agenda as they are essential to meet net-zero objectives. Many comments are made by campaigners, activists, environmental groups, politicians of all parties, consultants as well as scientists on how to achieve a clean energy future, for example by onshore or offshore wind turbines there seems to be a silence on critical materials, what they are, their worldwide locations and uses. For example, while people are likely to be aware of Li-ion batteries they may know little about the properties and supply of lithium, a very important critical material. The study of critical materials is not just of scientific interest but has geopolitical consequences as they are often located in countries who, at a future time, may be reluctant to export them to certain other countries (see Table 1.4).

Critical materials are important for a country’s national security and economic development,^5,14–16  but also allow it to project economic power in the 21st century. The search for these materials has not been restricted to the current climate crisis and the move towards a clean energy future. In 2004, the U.S. Geological Survey of the Department of the Interior searched areas of war-torn Afghanistan. Geologists were looking for deposits rich in copper, iron, bauxite (aluminium oxide) but prized deposits were lithium and lanthanides. The latter minerals were crucial for the developing area of green technology associated with smartphones and hybrid cars. The value of minerals in Afghanistan was estimated to be $1 trillion. Megan Black¹⁵  has referred to the phrase ‘extractive capitalism’ to secure America’s mineral stronghold in the Cold War in the 1960s. Here, geological prospecting moved from terrestrial searches to the use of satellites in space for aerial photography. Space programmes included the TIROS weather satellite, Gemini-manned orbiting vehicles and secret reconnaissance satellites like CORONA. The Landsat satellites had the capability to view Earth’s resources and the first was launched in 1972.

Sensors on the satellite¹⁵  were particularly suited for geological prospecting, that is imaging mineral deposits on or below the Earth’s surface. For example, multispectral scanners used reflective mirrors that detected possible mineral deposits. Frames or ‘images’ captured an area of approximately one hundred nautical miles. The satellites were operated by NASA, while the collection of images was managed by the Department of the Interior. In summary, Landsat captured geological patterns that might have indicated mineral deposits. Images were sold on a commercial basis to companies with interests in exploration of natural resources. These images revealed lithium deposits in the Salar de Uyuni salt flat of Bolivia. Open mining in this area now known as the ‘lithium triangle’ linking Chile, Bolivia and Argentina originated from this discovery by Landsat.

The height of activity for Landsat in mineral exploitation was the 1970s. However, in the 1980s budgetary criticism and a view that the American taxpayer was unfairly funding the cost of mineral exploration resulted in bringing Landsat under control of the private sector. In the 1990s Landsat was brought under control again for the U.S. government through the National Oceanographic and Atmospheric Administration (NOAA), NASA and the U.S. Geological Survey. Nowadays satellite monitoring is used for monitoring the environment including deforestation in the Amazon basins and climate change. The launch of satellites was initially carried out by national governments.¹⁷  Telstar, that was launched in the late 1950s, was used for transmission of transatlantic telephone calls. There was a very popular piece of instrumental music at the time that was named after the satellite and recorded by The Shadows, a group in the UK. However, in the digital world of the 21st century, companies design and construct rockets, sometimes under contract with governments for launching satellites. The latter can be small minisatellites. In December 2023, a space port for launch of satellites was opened on Unst, a small island off the far north of Scotland. It is intended to launch satellites from Unst in 2024. Note that semiconductors are crucial for construction of small satellites.

Examples of critical materials include:

• Lanthanides^5,16  (various applications)—lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.

• Battery materials—lithium, cobalt, manganese, vanadium and lanthanum.

• Platinum group metals (for fuel cells, vehicle exhaust catalysts, etc.)—platinum, palladium, rhodium, ruthenium, iridium and osmium.

• Electronic devices—tantalum, tin, gallium and germanium.

• Materials for permanent magnets (for wind turbines, starter motors, loudspeakers for smartphones and ear buds)—neodymium alloys containing dysprosium.

Other critical materials are listed in Chapter 5.

Methods other than satellite measurements are being used¹⁸  to detect critical materials by mapping the location and composition of subsurface fluids, particularly near volcanoes. Seismic attenuation measurements highlight the loss of energy through a medium, while seismic anisotropy measures how the speed of the seismic waves varies on the direction and shows how fluids move along faults. Measurements were taken on Uturunku, a dormant volcano in the Bolivian Andes. The volcano sits on the largest body of magma on Earth and is a source of hot metal-rich fluids. Measurements on attenuation and anisotropy were taken from data on over 1300 earthquakes using seismometers near the dormant volcano. The measurements enabled a map to be constructed which indicated whether the underlying crust was partly or fully saturated with fluids. This example illustrates the continuing importance of finding deposits of critical materials.

Many books on science-related areas tend to concentrate on one discipline, for example, chemistry, physics, or geology. In the author’s experience it is not common to come across books on subjects that cover areas which fall within very different disciplines such as geology and chemistry. However, successful exploitation of critical materials is an interdisciplinary area and requires input from fields that initially may not be thought important (see Figure 1.2). This book highlights the requirement for an interdisciplinary approach to activities on critical materials in the 21st century.

CO₂ levels in the Earth’s atmosphere have been increasing since the start of the Industrial Revolution. This increase happened as fossil fuels have been used increasingly for domestic and industrial use, as well as for electricity generation. This gas along with other gases including methane and nitrous oxide are greenhouse gases and contribute to global warming through their absorption of infrared radiation from the Earth. Governments are phasing out the use of fossil fuels and intend to stop using fossil fuels and replace them with sources of renewable energy for power generation. The main sources of renewable energy under investigation are solar (photovoltaic) cells, and turbines and nuclear power. Identification of mineral deposits on or below the Earth’s surface, for example by satellite imagery, can help a country project its economic power in the 21st century. This projection has been called extractive capitalism.

I thank Tracey Salt of TJS Typing Services for preparing the manuscript.