Types of Coal
Introduction
Coal is a fossil fuel that has powered human society for centuries. This sedimentary rock formed from ancient plant remains is rich in carbon and hydrocarbons, making it highly combustible. When burned, coal releases a large amount of energy, which is harnessed to generate electricity, produce steel, and provide heat for industries and homes. Throughout history, coal-fired furnaces have driven locomotives, heated buildings, and fueled factories. For example, during the Industrial Revolution, coal fueled steamships, early power plants, and the sprawling factories of Europe and North America, making it a symbol of industrial progress. Even as renewable energy sources grow, coal continues to supply a significant portion of the world’s electricity and industrial energy needs.
Understanding coal means recognizing that it comes in different varieties or ranks, each with unique properties. This comprehensive guide will explain how coal forms deep underground and how experts classify it. We will explore the four main types of coal—anthracite, bituminous, subbituminous, and lignite—looking at their composition, appearance, and common uses. Along the way, important terms and essential concepts like carbon content, heat value, and moisture will be highlighted to show what sets one type of coal apart from another. By the end of this guide, readers will have a thorough understanding of how each coal type is classified and why these differences matter for energy and industry. For decades, coal was the world’s leading energy source. Even today, it accounts for a large share of electricity generation in many countries, though its overall share is gradually declining as cleaner alternatives grow.
Geologists even named an entire period (the Carboniferous) for coal production, because of the vast swamp forests that became coal beds. In modern terms, known coal reserves are estimated to last around 100 years or more at current consumption rates, though how much will actually be burned depends on climate policies. Because coal is so widespread, it is often at the center of discussions about energy security and sustainable development. No single nation controls the world’s coal supply (unlike oil), which makes coal geopolitically different. However, coal is also increasingly seen as a symbol of the climate challenge, since it is the largest single source of CO₂ emissions from human activities. This guide presents a balanced view by covering both the benefits and challenges of coal. For perspective, modern societies still burn coal in staggering quantities. Around 7 billion tons of coal are consumed globally each year (as of the 2020s), far exceeding annual oil or gas use on an energy-equivalent basis. This scale of consumption helps explain why coal’s role is so important to understand. For anyone interested in energy or climate policy, understanding coal’s details is crucial for making informed decisions.
History of Coal
Coal has been used by humans for a very long time. Archaeologists have found evidence of coal fires in Britain from around 4000 BC. Ancient Chinese and Roman writings mention coal for heating and metalworking. However, these early uses were limited to local areas. The real expansion of coal use began in medieval times. By the 1200s, coal was being mined in England and parts of Europe for blacksmithing and home fires. The fuel was readily available compared to scarce wood in growing cities.
The Industrial Revolution (late 18th and early 19th centuries) marked a turning point for coal. In Britain, coal powered steam engines and became the main fuel of factories and railways. Coal mines expanded to provide fuel for ironworks, textile mills, and early electrical generators. The success of coal in Britain spurred coal mining around the world. In the United States and Germany, coal mining boomed in the 1800s. By the early 20th century, coal was the dominant energy source globally, fueling naval fleets and powering the first electric grids.
In the mid-20th century, oil began to overtake coal in many uses, especially in transportation and general industrial fuel. Natural gas usage also grew, but coal remained essential for electricity and steelmaking. The term “Coal Age” was sometimes used to describe the late 19th and early 20th centuries. Today, the history of coal is remembered in literature and culture: from Charles Dickens’ descriptions of coal smoke to the folk songs of coal miners. Many coal towns and regions still celebrate their heritage with memorials, festivals, and museums, even as they transition to new industries. By the mid-20th century, the downsides of coal had become clear. Episodes like London’s Great Smog of 1952 (caused by coal smoke) led to clean-air laws, and high-profile mining disasters led to stricter safety rules. These developments meant that by the end of the century, coal was no longer viewed only as a symbol of progress but also as a pollutant needing management.
Formation of Coal
Coal begins its journey in a very different form: as peat, a spongy, brown layer of partially decayed plant material. In swampy regions, ferns, trees, and other plants accumulate after death, forming thick beds of peat. Peat itself is combustible and is even used as a fuel in some parts of the world (for example, in Ireland and Finland), but it is not yet coal. Only when peat is deeply buried by more sediment does it begin the transformation into coal. Over many millions of years, the weight of rocks and soil above the peat increases pressure, and warmth from the Earth applies heat. Gradually, this buried peat is squeezed, driving off water and gases. The result is a dense, carbon-rich substance: the lowest rank of coal, called lignite.
This slow transformation process is called coalification. During coalification, the chemistry of the plant matter changes. Carbon atoms become more concentrated as hydrogen and oxygen escape in the form of water and other volatile gases. Organic compounds like cellulose and lignin break down, leaving behind mostly carbon. As heating and pressure continue, coal changes rank. From peat to lignite, then to subbituminous, then bituminous, and finally anthracite, each stage sees the coal become darker, harder, and richer in carbon. Anthracite coal, for example, has very little moisture or volatile content left, whereas lignite still contains much more residual water.
The timeline for coal formation spans tens to hundreds of millions of years. Most of the world’s large coal deposits formed during the Carboniferous period (about 360 to 300 million years ago), when vast swamp forests thrived. Regions that were once lush wetlands, such as the Appalachian basin in North America or the Ruhr region in Europe, are now known for their coal fields. However, coal can form in later geologic periods as well. For instance, some lignite beds in Europe and North America date to the Tertiary period, less than 65 million years ago. The difference in age and the intensity of geologic forces (like tectonic uplift) help explain why some coal became high-grade anthracite while other coal remains at lower ranks. Interestingly, the rate of peat accumulation is relevant for coal formation. It can take thousands of years to form a meter of peat. In some modern wetlands, forests accumulate peat so rapidly that geologists expect significant coal beds millions of years in the future. In places like Indonesia and Finland, peat is cut and used as fuel today, sometimes called “local coal.” However, only after deep burial and geological time will it become proper coal.
Coal Classification and Ranks
Geologists classify coal into ranks based on the degree of transformation it has undergone. In other words, coal rank refers to how much heat and pressure the organic material experienced during its formation. Under higher heat and pressure, coal becomes more metamorphosed: it becomes harder, drier, and richer in carbon. The rank of a coal deposit is often linked to its geologic history. Higher rank coal typically formed under more intense conditions and for longer periods of time.
Several factors determine coal rank. Carbon content is a primary one: higher-rank coals have a greater percentage of carbon. They also contain lower amounts of moisture and volatile compounds (the substances that vaporize during combustion). For example, anthracite, the highest-rank coal, has very high carbon content and very little moisture. Lignite, on the other hand, is low rank and has a high moisture content and less carbon. By examining carbon levels, moisture, and how much heat a coal can produce (its heating value), scientists identify its rank.
In practice, coal is often divided into four main ranks: anthracite, bituminous, subbituminous, and lignite. These ranks form a continuum from highest to lowest. At each stage, the physical appearance and energy content change. For instance, as rank increases, coal generally becomes harder, blacker, and more shiny. Lower-rank coals tend to be brownish and softer. This ranking system helps engineers, miners, and energy producers choose the right coal for the right purpose, since different ranks behave differently when burned or processed. If coalification continued past anthracite under extreme conditions, it could form graphite, which is nearly pure carbon and is used for pencils and electrodes rather than as a fuel. The classification mentioned so far is based mostly on carbon and heating value. Engineers and geologists also consider coal rank along with factors like volatility and ash when choosing coal for a specific application. Various national standards exist: for example, the American ASTM standard explicitly defines four ranks (A through D), while elsewhere terms like “thermal coal” and “metallurgical coal” are used to highlight coal’s intended use in power plants or steelmaking, regardless of rank.
Coal Composition and Quality
Chemically, coal is primarily a carbon-rich material, but it also contains hydrogen, oxygen, nitrogen, sulfur, and mineral matter. The exact composition varies by rank and origin. High-rank coals like anthracite are mostly carbon (70–90%), with very little moisture or volatiles. Lower-rank coals contain more hydrogen and oxygen, often in the form of water and organic compounds. All coals contain some ash-forming minerals that do not burn, which become residue after combustion.
Coal quality is often described by two types of analysis. Proximate analysis measures moisture (water content), volatile matter (gases released when heated), fixed carbon (the solid combustible part), and ash (the inert residue). For instance, a typical lignite might contain 30–40% moisture, 10–20% volatile matter, 10–20% fixed carbon, and 5–10% ash. Anthracite, by contrast, might have 5% moisture, 5% volatile matter, and over 80% fixed carbon. Ultimate analysis measures the elemental content: carbon might be 50–85%, hydrogen 3–6%, oxygen 5–30%, with a few percent of nitrogen and sulfur.
Impurities in coal affect its use. High sulfur content, common in some bituminous coals, leads to sulfur dioxide emissions, which cause acid rain if not controlled. Many power plants burn low-sulfur coal or install scrubbers to remove SO₂ from flue gas. Ash content dictates how much solid waste is produced: low-ash coals are preferred in large boilers to reduce cleanup. Some ash (fly ash) can be captured and reused in cement or concrete. Nitrogen and trace metals in coal can form pollutants like NOₓ and mercury during combustion, so environmental regulations may limit their levels. Another useful way to view coal is by its moisture content. High-moisture coals (like lignite) have lower effective energy. When engineers design combustion systems, they must account for moisture and volatile gases, because water and volatiles lower the flame temperature. Additionally, trace elements in coal (like chlorine or heavy metals) can cause corrosion or toxicity. Coal specialists therefore often test for specific hazardous elements to determine how best to clean or handle the coal.
In industry, coals are often sold in grades based on these quality measures. For example, a power plant might prefer “low-sulfur” coal to reduce emissions, while a steel mill wants coal with good coking properties (high coke yield). Coal brokers and mines routinely analyze each batch and label it with its moisture, ash, sulfur, and heat value. These specs ensure buyers get the right coal for their needs. Thus, “coal quality” is a crucial concept: two coals of the same rank might perform very differently if one has much more ash or sulfur than the other. Another useful distinction is by intended use: for instance, “thermal coal” refers to coals optimized for burning in power plants, while “metallurgical coal” (a type of bituminous) is optimized to form coke for steelmaking. These labels help industries choose the right coal grade even if multiple rank descriptions overlap.
Major Types of Coal
Anthracite (Hard Coal)
Anthracite is the highest-rank coal and is often called “hard coal.” It is black and shiny with a semi-metallic luster. Anthracite typically contains about 86% to 97% carbon by weight. This very high carbon content gives anthracite the highest heating value of any coal. It burns longer and hotter than other coals, and produces very little smoke because most of the volatile compounds have already been driven off in the coalification process. Dry, hard, and brittle, anthracite coal fractures and sparks when struck, rather than crumbling like lower-rank coal.
Because it requires intense heat and pressure to form, anthracite is relatively rare. Most of the world’s anthracite deposits were created from ancient forests over 300 million years ago. In the United States, nearly all anthracite is found in northeastern Pennsylvania (the Anthracite Coal Region). A large portion of global anthracite comes from countries like China, Russia, and Ukraine. Total production of anthracite is small compared to other ranks—often less than 1% of a country’s coal output—because of its rarity.
Anthracite’s clean burn and intense heat make it useful for certain specialized applications. It has been used to heat homes (especially in older stoves and fireplaces) with minimal smoke. More importantly, anthracite is valued in metallurgy and metalworking. In the steel industry, anthracite can be mixed with iron ore in furnaces to provide intense heat without adding impurities. It can also be processed into activated carbon used in filters, and its high carbon content makes it useful in making electrodes and other carbon products.
For perspective, anthracite’s high carbon content translates to a high energy value. It can produce about 30 megajoules (MJ) of heat per kilogram when burned. By contrast, lower-rank coals produce less heat: bituminous coal yields around 24–28 MJ/kg, subbituminous around 18–26 MJ/kg, and lignite often under 20 MJ/kg. These numbers highlight why anthracite burns longer and hotter than other coals.
Bituminous Coal
Bituminous coal is a middle-ranked coal, sitting between subbituminous and anthracite. It is typically black, often with a bright or dull sheen. Bituminous coal can vary in carbon content (roughly 45% to 86% carbon), which means there is a wide range of qualities within this rank. When fresh, blocky bituminous coal often looks shiny, with thin layers that alternate between glistening and matte textures. As a fuel, bituminous coal has a relatively high energy content. It releases considerable heat and is a common choice for power plants. However, because it still contains volatile compounds, burning bituminous coal produces more smoke and pollutants than higher-rank coal.
Bituminous coal is the most widely used rank of coal worldwide. It has extensive reserves in many coal-producing regions, such as the Appalachian Mountains in the United States, parts of Europe, China, India, and Australia. In the US, bituminous coal has historically made up a large share of production. Its abundance and high energy density make it a workhorse of electricity generation. Power plants burn bituminous coal to boil water and run steam turbines, supplying a significant portion of modern electricity. In addition, this coal rank is used to make coke by heating it without air, which is required in steelmaking.
Within bituminous coal, experts often distinguish two broad categories: thermal coal and metallurgical coal (also called coking coal). Thermal bituminous coal is burned for heat and power. It may also be used in cement kilns or industrial boilers. Metallurgical bituminous coal, on the other hand, has special properties for steel production. When metallurgical coal is heated in ovens, it softens, swells, and then re-solidifies into a hard, porous material called coke. Coke from bituminous coal provides the carbon and heat needed in blast furnaces to turn iron ore into steel.
Historically, bituminous coal had other industrial uses. In the 19th and early 20th centuries, coal gasification produced “town gas” for lighting and heating in many cities. Heating bituminous coal in retorts yields a flammable gas mixture (mostly hydrogen and methane) and a thick residue called coal tar. Coal tar contains chemicals that were used to make dyes, disinfectants, and even medicines like aspirin. This process has largely been replaced by natural gas and petroleum, but some chemical plants still produce compounds from coal tar byproducts.
Subbituminous Coal
Subbituminous coal has lower carbon content than bituminous coal, usually around 35% to 45% carbon. It is dark black or sometimes dull brownish in color. Compared to higher ranks, subbituminous coal is softer and contains more moisture. These characteristics give it a lower heating value, meaning it releases less heat per ton than bituminous coal. However, one advantage is that many subbituminous coals have lower sulfur levels. As a result, when burned, they release fewer sulfur dioxide emissions, which makes them relatively cleaner than other types in terms of air pollution.
Subbituminous coal is often found in large, thick beds near the surface. In the United States, the majority of subbituminous coal comes from Wyoming and Montana. In fact, Wyoming’s Powder River Basin is famous for its vast subbituminous coal reserves. Production of this coal is significant: in recent years it has contributed almost half of U.S. coal output. Around the world, subbituminous coal is also mined in Canada, Australia, and parts of Asia. Because its deposits are often close to the surface, it can be mined relatively cheaply. Much of the subbituminous coal is used to generate electricity close to where it is mined, reducing transportation costs.
Power plants burning subbituminous coal can take advantage of its ease of mining and moderate energy content. In large power stations, it is burned to boil water into steam, driving turbines for electricity. Its lower energy density (compared to bituminous) is offset by the abundance and low cost of these deposits. In some regions, subbituminous coal is mixed with bituminous coal or used on its own to meet the needs of the grid. Because of its cleaner burn profile (less sulfur and often less ash), it remains an attractive option where environmental regulations exist. For example, in Australia’s Bowen Basin and Indonesia’s Kalimantan region, huge subbituminous deposits are mined for export. These international shipments of lower-rank coal help meet demand in countries without their own reserves. Global coal prices often depend on supply and demand for these thermal coals.
Lignite (Brown Coal)
Lignite is the lowest rank of coal and is also known as “brown coal.” It has only about 25% to 35% carbon. Lignite is brownish-black and is very soft compared to other coals. It also has the highest moisture content, which means it contains a lot of water. These properties give lignite a very low heating value. When burned, lignite produces less heat per ton than any other rank of coal. Because of its high moisture and crumbly texture, lignite is often weathered and can break apart easily when excavated.
Lignite deposits tend to be relatively young in geologic terms. Large lignite reserves exist in places like North Dakota and Texas in the U.S., as well as in countries like Germany, Russia, Australia, and India. In the U.S., lignite production is much smaller than bituminous or subbituminous, often around 5–10% of total coal output. Lignite is primarily used to generate electricity near where it is mined. Power plants burn lignite close to the mines to avoid long-distance transportation, because shipping this heavy, low-energy coal is not economical. For example, several coal-fired power plants operate on lignite in North Dakota, supplying local power grids. In Europe, countries such as Germany and Poland have sizable lignite industries. Germany’s giant open-pit mines in the Rhineland and Lusatia supply several power plants with coal.
Despite its low energy density, lignite plays a role in power generation because of its abundance in some regions. Plants using lignite often rely on it being cheap and available rather than highly efficient. Lignite itself can even be processed: for example, in North Dakota a plant converts lignite into synthetic natural gas, which can then be sent through pipelines. Lignite generally produces more carbon dioxide per unit of energy than higher-grade coals. As a result, most modern lignite-fired plants have systems to scrub sulfur and other pollutants from the flue gases. Some facilities co-fire lignite with biomass or use advanced boilers to reduce emissions. Overall, while lignite is useful where it is found in abundance, its high emissions and low efficiency mean it is less favored under strict environmental policies. Some companies have responded by briquetting lignite into more user-friendly fuel blocks; for example, certain heat-and-power plants in Europe burn dried lignite briquettes in their boilers.
Coal Mining and Processing
Coal extraction is a major industry worldwide. The most common method is surface mining, which removes soil and rock (overburden) above shallow coal seams. In open-pit and strip mines, powerful excavators or draglines strip away layers of earth to expose the coal. When coal lies under hills or small mountains, a controversial technique called mountaintop removal is sometimes used: blasting away the summit to reach the coal beneath. This allows efficient extraction of near-surface coal, but it dramatically alters the landscape and ecosystems. After the coal is extracted, the leftover material (known as overburden) is piled nearby. In many countries, mining companies must later restore or re-contour the land to reduce environmental impact.
When coal seams are deep underground, miners use underground mining methods. In room-and-pillar mining, a network of rooms is cut into the coal seam, leaving pillars of coal to support the roof. In longwall mining, a massive shearer continuously removes coal along a long panel, with hydraulic supports moving forward to hold up the roof behind it. Modern underground mines employ heavy machinery such as continuous miners, shuttle cars, and roof bolters to cut and haul coal. Miners rely on complex ventilation systems to provide fresh air and to remove dangerous gases. Underground mining is more dangerous and expensive than surface mining, but it allows access to thicker and deeper coal beds.
After extraction, coal often undergoes preparation to improve its quality. Raw coal from the mine may contain soil, rocks, and sulfur. At a coal preparation plant, the coal is crushed and sorted by size. Then it is washed in water and mechanical separators. Because coal has a lower density than rock, dense liquids or jigs can separate the heavier waste. Impurities settle to the bottom, while cleaned coal is collected on top. This washing process reduces ash and sulfur content. The washed coal is dried and then sorted by grade or blended to match the requirements of the buyer. For example, high-volatile coal might be blended with low-volatile coal to achieve a desired quality for power plants or steel mills.
Coal mining has significant environmental and safety implications. Surface mining can destroy habitats and leave large spoil piles and pit lakes if not reclaimed. Underground mines can collapse or flood if not properly managed, and methane gas poses a constant hazard. In some operations, coalbed methane (the natural gas found in coal seams) is captured and used as fuel, which improves safety and provides energy. Many miners have historically suffered from black lung disease due to coal dust inhalation. After mining, land reclamation efforts aim to restore vegetation, and water runoff is treated to remove contaminants. In many regions, abandoned mines continue to affect the environment for decades, highlighting the importance of strict regulations and safety practices. Once mined, coal is often transported by rail, barge, or truck to power plants or ports. Some mines use long conveyor belt systems to move coal efficiently over distance. At the power plant, coal is usually pulverized (ground into a fine powder) before burning, so it can burn more uniformly and completely in the boiler.
Coal in the World
Coal is found on nearly every continent. Large reserves are known in Asia (China, India, Indonesia), North America (United States, Canada), Europe (Russia, Germany, Ukraine, Poland), and Australia. China and the United States have the world’s biggest deposits of coal. In fact, coal reserves are so vast that experts estimate they could power humanity for decades or longer. These reserves are categorized by rank and location; for example, Australia is rich in lignite and subbituminous coal, while the Appalachian and Ural regions have extensive bituminous seams.
A small number of countries dominate coal production and consumption. China is the largest producer and consumer by far, using most of it to fuel power plants. India is second, and together these two countries burn the majority of the world’s coal. Other major producers include the United States, Indonesia, Australia, Russia, and South Africa. Many of these countries export coal: Australia and Indonesia are leading exporters of thermal coal to Asian markets, while the United States and Russia export significant amounts of metallurgical coal. International coal prices can vary based on demand and transportation costs.
Coal production and consumption also affect global economics. For instance, Australia and Indonesia rely heavily on coal exports for revenue. Conversely, major coal importers like Japan and South Korea pay significant costs to secure coal supplies. As a result, coal is not only an energy issue but also an economic one, influencing trade balances and foreign policy. In coal-dependent regions, jobs and local budgets often hinge on mining activity, creating strong political ties to the coal industry. In Europe, coal use and production have fallen sharply in recent years. Countries like the United Kingdom and Germany are closing coal mines and power stations in favor of cleaner energy. In contrast, Poland, the Czech Republic, and others in Eastern Europe still generate a large share of their electricity from coal. Poland in particular has extensive lignite and hard coal mining, and coal has been a cultural and economic cornerstone in regions like Silesia. In South America, Colombia is a major coal exporter, supplying the United States and Europe. Brazil has some coal production for domestic power but also imports coal. In the Middle East, coal is rare; countries like Iran and Turkey have modest reserves, and others rely on imports. Central Asia (Kazakhstan, Uzbekistan) also has coal mines that feed local power plants. In summary, the world’s geography of coal is complex: virtually every region has some coal, but certain countries dominate production and use.
Coal Markets and Economics
Coal is an important commodity traded around the world. The price of coal depends on its type, energy content, and location. Thermal (steam) coal is usually sold by the ton or by its heating value. Major benchmarks include the Newcastle index (Australia) and API2 (Europe). In Asia, coal from Indonesia and Australia sets the tone for market pricing. Metallurgical (coking) coal, used for steelmaking, trades at a premium over thermal coal. Large steelmakers often sign long-term contracts for coking coal, whereas thermal coal prices may be more variable depending on power demand and stockpiles. Global coal prices can fluctuate with economic growth, currency exchange rates, and policy changes in large countries like China.
Transport costs are a key factor in coal economics. Coal is bulky and heavy, so shipping by rail, barge, or sea can add significantly to its delivered cost. Countries rich in coal often build power plants next to mines or along rail lines to minimize transport. For example, China locates many power stations near its coal fields. Australia’s coal is carried in very large bulk carriers to Asia, whereas Japan and the UK must import all their coal by ship or rail. The commodity price plus freight determines a plant’s cost of fuel. Natural gas prices, carbon emission costs, and import duties all influence coal demand. In early 2022, for example, coal demand and prices jumped in Europe and Asia when natural gas and oil prices spiked. Many coal plants that had been idled were restarted to help meet electricity needs. Coal market volatility can be dramatic: periods of economic slowdown or events like the COVID-19 pandemic temporarily reduced coal demand and prices. Conversely, cold winters or industrial booms can spike demand. During late 2021, for example, low wind power and high energy needs caused coal prices in Asia to climb dramatically. Additionally, currency fluctuations matter: coal is typically traded in U.S. dollars, so countries with weaker currencies face higher import costs. Because of this volatility, both coal producers and consumers often enter into multi-year contracts to stabilize supply and prices.
Coal also has logistical considerations: it can be stockpiled for months or years near a power plant, providing a buffer against supply disruptions. Natural gas requires high-pressure storage or pipelines, which is less flexible. Technically, coal-fired generators have large turbines that provide inertia to the electrical grid, aiding stability. In summary, coal is usually the least expensive fuel for countries with big reserves, but it is bulky and polluting to use. Oil and gas burn cleaner but often require expensive infrastructure or imports. Each fuel has trade-offs in cost, availability, and environmental impact.
Coal vs Other Energy Sources
Coal is a solid fossil fuel, whereas petroleum (oil) is a liquid and natural gas is gaseous. All three come from ancient organic matter, but coal forms mainly from land plants, while oil and gas often come from marine organisms. Coal is mined from seams and burned in boilers. Oil and gas are pumped from underground reservoirs; oil is refined into fuels like gasoline or diesel, while natural gas is used directly or converted to electricity in turbines. Coal plants often run continuously to provide baseload power, whereas gas turbines can start up and shut down quickly to meet peak electricity demand.
Coal is often abundant and cheap compared to oil or gas. However, its solid form requires heavy handling and storage. Oil and gas can be transported conveniently in pipelines or tankers. Burning coal also tends to release more pollution per unit of energy: it emits more carbon dioxide, sulfur dioxide, and particulates than oil or especially natural gas. For example, burning coal emits roughly twice the CO₂ per kilowatt-hour as burning natural gas. These environmental differences mean that many power systems have shifted toward gas and renewables where possible, although coal remains important in regions without cheap gas or with large coal reserves. In recent years, renewable energy like wind and solar has become very competitive. New wind or solar projects often cost less per unit of electricity than building new coal plants. This shift is causing many utilities to prefer gas and renewables when adding capacity.
Coal can also be stockpiled easily for months or years near a power plant, providing a buffer against supply disruptions. Natural gas requires high-pressure storage or pipelines, which is less flexible. Technically, coal-fired generators have large turbines that provide inertia to the electrical grid, aiding stability. In summary, coal is usually the least expensive fuel for countries with big reserves, but it is bulky and polluting to use. Oil and gas burn cleaner but often require expensive infrastructure or imports. Each fuel has trade-offs in cost, availability, and environmental impact.
Uses of Coal in Energy and Industry
- Electricity Generation: The largest use of coal is burning it in power plants to generate electricity through steam turbines.
- Steel Production: Coal, in the form of metallurgical coke, is essential in making steel from iron ore in blast furnaces.
- Cement Manufacturing: Coal is burned in cement kilns to produce cement, making up a significant portion of industrial coal use.
- Chemical Products: Coal derivatives like coal tar and syngas provide raw materials for chemicals, fertilizers, and plastics.
- Heating and Other Uses: Historically, coal heated homes and drove steam engines; today it still heats some district heating systems and industrial processes in certain regions.
Today, coal remains one of the world’s most abundant energy resources. It plays an important role in electricity generation, especially in countries with large coal deposits. In power plants, coal is burned to produce steam that drives turbines and generates electricity. Globally, more than one-third of electricity supply comes from coal-fired plants. For example, coal accounts for a majority of electric power in countries like China and India, where demand for electricity is still growing. Even in the United States and Europe, coal plants continue to produce a notable share of electricity (though that share has fallen in recent years).
Another major industrial use for coal is in steel production. About 70–75% of the world’s steel is made using coal in the form of coke. Coke is a nearly pure form of carbon made by heating bituminous coal in the absence of air. In blast furnaces, coke acts as both a fuel and a reducing agent, helping to convert iron ore into iron and steel. Without coal (or coke), modern steelmaking would have to rely on other energy sources, which can be more expensive or technically challenging.
Coal also finds use in cement manufacturing and various chemical processes. In cement plants, coal can be burned to heat kilns and harden cement. Some chemicals and carbon products (like carbon fibers or carbon black) are also derived from coal or its byproducts. Additionally, processes like coal gasification can convert coal into synthetic gas or liquid fuels, which can serve as alternative fuels or chemical feedstocks. These uses are not as large in volume as power generation, but they underscore the versatility of coal as a resource.
Coal is also widely used in combined heat and power (CHP) systems. In a CHP plant, coal is burned to produce electricity, and the waste heat is captured to provide heating or industrial steam. This cogeneration approach can nearly double the fuel efficiency. For example, in Eastern European countries and China, many large CHP plants use coal to serve district heating networks or factories, making more use of the coal’s energy content.
Beyond burning coal directly, industrial processes can transform it. Gasification converts coal into a mixture of carbon monoxide and hydrogen (synthesis gas), which can be cleaned of pollutants and then burned in gas turbines or used to make chemicals. Power plants using this method, called Integrated Gasification Combined Cycle (IGCC), achieve higher efficiencies and make carbon capture easier. Coal can also be liquefied: in coal-to-liquids (CTL) plants, coal is chemically converted into liquid fuels similar to gasoline and diesel. For example, South Africa operates large CTL plants that supply transportation fuel from its coal reserves. These technologies are energy-intensive and expensive, so they are less common, but they demonstrate ways to use coal with potentially lower emissions or to produce valuable products when oil and gas are scarce.
Coal and the Environment
Coal’s environmental impact is significant. When burned in power plants or other furnaces, coal releases carbon dioxide (CO₂), the primary greenhouse gas driving climate change. On a per-unit-of-energy basis, coal emits more CO₂ than most other fossil fuels. For example, lignite can produce over 100 pounds of CO₂ per million BTUs of heat, roughly twice that of natural gas. As a result, coal-fired power stations are major contributors to global CO₂ emissions. In fact, coal accounts for around 20–30% of all energy-related CO₂ emissions, depending on the region. Many countries aim to cut these emissions by switching from coal to cleaner sources.
Burning coal also releases pollutants besides CO₂. Sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) come from coal combustion, leading to smog and acid rain that harm ecosystems and human health. Coal power plants may also emit particulate matter and heavy metals such as mercury and arsenic. Without pollution controls, these emissions can cause respiratory illnesses and contaminate waterways. Modern coal plants typically use scrubbers, filters, and other technologies to trap sulfur and particulates, but such systems increase costs and require maintenance. Coal-fired power plants often require large amounts of water for steam generation and cooling, which can strain water resources in arid regions. This contrasts with solar photovoltaic or wind power, which use minimal water during operation.
Coal mining itself can damage the environment. Surface mining removes soil and vegetation, affecting wildlife and water quality. Mountaintop removal mining in the U.S. Appalachians and open-pit mining in other regions have left visible scars on the landscape. Water runoff from mines can carry silt and metals into rivers, and abandoned mines may leak acid or methane long after closure. Because of these issues, coal mining is tightly regulated in many countries, and land is often reclaimed and reforested after use.
Efforts to reduce coal’s environmental footprint include carbon capture and storage (CCS) technology, which aims to trap CO₂ before it escapes. Some industrial processes also recycle coal byproducts, such as fly ash in concrete. Additionally, programs for emission trading or carbon taxes make coal more expensive relative to cleaner energy. Despite these measures, the easiest way to mitigate coal’s impact is to burn less of it. Consequently, renewable energy sources (solar, wind, hydro) are increasingly replacing coal in many power systems around the world. Many forecasts suggest coal demand may peak in the near future. To meet global climate targets, most existing coal plants would likely need to be retired by mid-century, which is driving policies to transition to cleaner energy sources.