Now it's time to have a more in-depth look at major energy sources and to think about the benefits and costs or challenges that each brings to the party. Let's start off with a dominant energy sources today: fossil fuels. When we think of fossils, we usually think about beautifully preserved shells or bones like the spectacular 505 million-year-old trilobite fossil in this slide. But there are other kinds of fossils, too. Fossil fuels are actually fossils. The remains of ancient life buried over time up to thousands of meters below the Earth's surface. But instead of shells or bones, fossil fuels are the remains of soft tissues. Everything from microscopic organisms to flesh and organs of animals, to leaves and wood from trees. Some of the fossil fuels we burn today originated as life more than 500 million years ago while other fossil fuels are forming deep beneath our feet, as we speak. The type of fossil material and as history of burial determine what type of fossil fuel is formed. Wood and other plant material from ancient forests and swamps over time can be buried under a few meters of soil and sediment. There they decay slowly under the right conditions over thousands of years to form peat, partly decayed vegetation that is like compacted soil. Peat is the most basic fossil fuel, as the fossilized material has not really changed that much over time compared to coal, oil, and gas. Peatlands cover enormous areas of the Earth's surface, millions of square kilometers. Where conditions are right, peat can be excavated and cut into blocks, perfect for use as a fuel. Peat was an important energy source hundreds of years ago in places like Great Britain. But relatively little peat is burnt today, having been replaced largely by coal, oil, and gas. In historical times, peat bogs were great places to preserve things as the air couldn't get at them. Archaeologists have found foodstuffs like butter in peat bogs, as well as mummified human remains. With further burial between layers of sediment and rock to depths of hundreds to thousands of meters over periods of millions of years, peat is compressed and heated until it becomes coal. First lignite or brown coal, then bituminous coal, which is the coal we often use for power generation. Finally, given enough time and pressure, to anthracite, a combustible sedimentary rock composed mostly of carbon. Let's turn to lakes and oceans, where organisms die and sink to the bottom, becoming buried and sediment just as wood does in the coal swamp. In the ocean, the fossil material is made primarily of soft plant and animal tissues, everything from algae and microscopic plankton to large fish. Soft tissues are chemically different from wood. They have less carbon and are richer in hydrogen, so they experience different transformations when buried beneath the Earth's surface over time. Time, heat, and pressure turn soft tissue fossil material into oil, a huge range of chemical compounds rich in carbon and hydrogen. We also use the terms petroleum and hydrocarbons. We can extract oil from deep beneath the surface and refine it into a variety of useful materials that serve as both energy sources and industrial feedstocks. We'll talk about that in the next lesson. As more time goes by and the soft tissue fossils are buried more deeply, heat and pressure actually refine them further, splitting the hydrocarbon molecules into the simplest hydrocarbon, one carbon atom and four hydrogen atoms. This is methane, which we call natural gas. There's so much to say about natural gas, and we'll talk about that in a couple of lessons. But for the remainder of this lesson, let's focus on coal. Coal was the energy source that rapidly advanced the Industrial Revolution, beginning in the 18th century. For the first time in human history, a compact and efficient energy source could create heat to generate steam, which was used to power steam engines of all kinds. Steam engine-powered locomotives revolutionized land transportation and steam-powered ships gradually replaced sailing vessels for commerce and war at sea. The concept of energy density and the ease of handling and harnessing the different sources of energy really became clear during the Industrial Revolution. We'll be talking about energy density in terms of today's energy transition later in the course. Let's go back to the Sankey diagram we looked at earlier and talk about coal. Coal is a critically important source of energy throughout modern society. It's the number 1 fuel for generating electricity worldwide. Another large part of our coal supply flows directly through to manufacturing, where it's essential for making electricity, iron and steel, and cement. Modern civilization could not exist without these, and for the moment, they all rely on coal. Coals that have been subjected to only modest burial depths are less pure lower-grade coals. Lignite and bituminous coal, they don't burn as hot as pure coals and they produce more pollution, but they are very abundant and supply enough heat for generating electricity. We call them thermal coal. Thermal coal moves by conveyor belt into the generating station where it is pulverized and burned to produce heat for boilers that create steam to drive a turbine generator that creates electricity. This process is similar to gas-fired generators or nuclear power generators, just using different heat sources to produce the steam to turn the turbines. This map by the International Energy Agency represents trade and thermal coal globally in 2019. The thickness of the arrows represent the volumes of coal traded. Major coal mining centers are in Australia, Russia, Indonesia, and the Americas. While each producing center burn some of its own thermal coal, much of it goes to power generation in China, India, Southeast Asia, and Europe. Here we see the locations of over 13,000 coal-fired power generation units in the world today. Many of them in North America and Europe, but an increasing number in Asia. The International Energy Agency's Coal 2020 report documents rapid ongoing construction of coal-fired generation in Asia, particularly in China, even as coal-fired plant shut down elsewhere, primarily in Europe and North America. Given that coal-fired generators can have a lifespan of 50 years or more, it's safe to say that coal will continue to be an important electrical generation fuel for many years to come. Coals that had been buried deeper in the Earth for longer periods of time are denser, pure, and generate much more heat than thermal coals. They also burn cleaner, producing less pollution and ash. The geological name for these coals is anthracite. They are scarcer and more valuable than thermal coals and in the trade, they are referred to as metallurgical coals. The metallurgical coal trade is significantly different from the thermal coal trade. North America, Australia, Russia, and Mongolia are major producers of metallurgical coal. It is used both domestically and exported to steel-making centers in Japan, China, India, and Europe. Looking at thermal and metallurgical coals together, world demand increased dramatically up until about 2014 and then leveled off. Obviously, China lead this massive increase in consumption. But as China's share is no longer growing rapidly, we see more growth in India and other Asian nations, even when consumption falls in North America and Europe. Even COVID-19 caused only a temporary downturn in coal consumption, which is forecast to remain high through 2024. With that background, let's compare the positives and negatives, the benefits and the costs of using coal. We'll repeat this exercise for every energy source as we proceed through the course. First, the positives or benefits. This chart of world energy sources shows that coal is a dominant energy source in the world today, primarily in generating electricity and in heavy industry. We know how to find and produce it. We've already built power plants, steel mills, and cement plants to burn coal. Coal is very energy-dense. It packs a lot of energy into a small package. So we can build a thermal coal-generating station at a convenient location near to where the power is consumed. Because transporting the energy-dense coal is cheap, we can easily store coal in large piles at the generating station so that people and industries can access the fuel they want on-demand at any time, which is what we mean by dispatchable. Coal energy is always there when we need it. What about the negative aspects of coal? Well, number 1 is greenhouse gas emissions. Burning coal creates carbon dioxide or CO_2. The greenhouse gas that we're most concerned about has an agent of accelerating climate change. This chart shows that brown coal, lignite, and hard metallurgical coal, anthracite, both emit a lot of CO_2 when burnt to produce electricity. We know that the concentration of CO_2 in the atmosphere has risen dramatically in past decades as we use more and more fossil fuels. Coal mining also releases methane, another potent greenhouse gas or GHG. Concerns about GHG emissions has led many high-income nations, particularly in North America and Europe, to limit trade, block construction of new coal-fired generation, and shut down existing coal power plants. Then there's the issue of pollution. Besides CO_2, burning coal produces smoke and ash, which contain very small particles to create smog and present health hazards. Gases other than CO_2, such as nitrogen oxides and sulfur dioxide, are products of burning and they're toxic and hazardous as well. Even with technological advances reducing pollution from coal-fired generating stations, it's difficult to reduce a noxious gas output. Besides air pollution, there are other pollution and environmental issues associated with coal extraction, including contamination of surface and groundwaters. The negative effects of pollution are well-documented and air pollution from burning fossil fuels causes many early deaths each year. Coal mining, whether conducted underground or in large open pit mines, has a host of environmental issues. Surface water bodies and shallow groundwater can be contaminated by seepage of toxic materials such as selenium from mine sites. The beauty and integrity of landscapes can be damaged, particularly where mining occurs in mountainous areas, such as here in Southern British Columbia. Many technological advances today in coal production, transportation, and use are focused on reducing environmental impacts, particularly GHG emissions. Coal mines must adhere to stricter standards on release of pollutants such as selenium. Coal-fired generating stations must adopt measures to reduce pollution. But the key issue is the demand for coal. This map from Carbon Brief shows us coal-fired power generation currently operating and planned in the near future. Many coal-fired plants that have been closed recently or are planned for closure in the near future as in the UK and Alberta are not shown. But what is remarkable is the number of stations under construction or being planned. A great deal of new coal-fired capacity is coming on stream in Asia and Africa, but also in the Middle East, Europe, and Australia. As well, the demand for metallurgical coal for industrial applications continues to grow, interrupted only by the 2020 pandemic-related downturn. Next lesson, we'll examine the second major fossil fuel: oil.
