Coal

Coal is a combustible black or brownish-black sedimentary rock, formed as layers called coal seams. It is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. It is a fossil fuel, formed when plants decay into peat which is converted into coal by the heat and pressure of deep burial over millions of years. Vast deposits formed from wetlands called coal forests that covered much of the tropics during the late Carboniferous and early Permian.

Coal is used primarily as a fuel. While coal has been known and used for thousands of years, its usage was limited until the Industrial Revolution. With the invention of the steam engine, coal consumption increased. In 2020, coal supplied about a quarter of the world's primary energy and over a third of its electricity. Some iron and steel-making and other industrial processes burn coal.

The extraction and burning of coal damages the environment and human health, causing premature death and illness, and is the largest source of carbon dioxide contributing to climate change. Over fifteen billion tonnes of carbon dioxide were emitted by burning coal in 2024, which was more than a quarter of total global greenhouse gas emissions. As part of worldwide energy transition, many countries have reduced or eliminated their use of coal power. The United Nations Secretary General asked governments to stop building new coal plants by 2020.

A record amount of coal was burnt in 2024, but consumption is expected to peak before 2030. To meet the Paris Agreement target of keeping global warming below 2 °C (3.6 °F) coal use needs to halve from 2020 to 2030, and "phasing down" coal was agreed upon in the Glasgow Climate Pact.

The largest consumer and importer of coal is China, which mines almost half the world's coal, followed by India with about a tenth. Indonesia and Australia export the most, followed by Russia.

Etymology

The word for coal has ancient roots. It began as col in Old English, coming from an even older language called Proto-Germanic. This word is related to similar words in other old languages, such as kole in Old Frisian, cole in Middle Dutch, and kohle in modern German.

Formation of coal

The process of turning dead plants into coal is called coalification. Long ago, Earth had thick forests in wet, low-lying areas. When plants died in these places, they were protected from breaking down by layers of mud or water. This allowed them to turn into peat, which is like the first step in making coal.

Over millions of years, these peat layers were buried deeper and deeper under sand and mud. The heat and pressure from this burial changed the peat into coal. The type of coal that formed depended on how much heat and pressure were applied. Lighter, softer coal called lignite formed with less heat and pressure, while harder, denser coal like anthracite coal needed more. Most of the world's coal formed during a time called the Carboniferous period, when the climate and land conditions were just right for making lots of coal.

History

Further information: History of coal mining

People have used coal for thousands of years. The oldest known use of coal was found in a place called Ostrava, Petřkovice, from around 25,000–23,000 years ago. In China, people began using coal around 4000 BC to make ornaments, and later to smelt copper. Famous traveler Marco Polo described coal in the 13th century as “black stones … which burn like logs.”

In Europe, early uses of coal date back to the Bronze Age around 3000–2000 BC in Britain, where it was used in funeral fires. The Romans used coal in places like England and Wales for heating and metalworking. By the 13th century, coal, sometimes called “seacoal,” was being shipped to London for building and other uses. As easier-to-reach coal ran out, people began mining underground.

The Industrial Revolution saw coal become a key energy source, powering steam engines. Britain was a major coal producer, and coal remained important for industry through the 19th and 20th centuries.

Composition

Coal is made from many different organic materials and comes in several types. Younger coals, like brown coal and lignite, are not completely black. The two main black types are bituminous coal, which is more common, and anthracite, which has the most carbon. Anthracite has the highest energy value, followed by bituminous coal, lignite, and brown coal. Some anthracite contains pure carbon in the form of graphite.

Bituminous coal is mostly made of carbon, with smaller amounts of hydrogen, oxygen, nitrogen, and sulfur. These elements come from the plants that formed the coal long ago. Coal also contains ash, which is made of minerals that do not burn. The amount of sulfur in coal can vary, and when coal is burned, it can release certain gases. Some sulfur can be removed before burning by special processes. Other small parts of coal include trace minerals, which can become a problem when the coal is burned.

Uses

Most coal is used as fuel. In 2017, coal provided 27.6% of the world's energy, with Asia using nearly three-quarters of it. Coal has a lot of energy; it takes about 325 kilograms of coal to power a 100-watt lightbulb for a whole year in a power plant with 40% efficiency.

Electricity generation

In 2022, 68% of global coal use was for making electricity. Coal burned in power stations, called thermal coal, is turned into steam that spins turbines to create electricity. Some newer plants use a process called integrated gasification combined cycle (IGCC), which burns coal more efficiently and creates less pollution.

Coke

Main article: Coke (fuel)

Coke is made from coal by heating it without air. It is very important for making steel because it helps turn iron ore into iron. Coke is grey, hard, and can produce a lot of heat.

Production of chemicals

Chemicals have been made from coal since the 1940s. Coal can be turned into syngas, a mix of gases, which is used to make many everyday products like plastics and fertilizers. This process needs a lot of water.

Liquefaction

Coal can be turned into liquid fuels like gasoline or diesel through processes that add hydrogen or change its structure. This usually creates more carbon dioxide than making fuel from oil.

Gasification

Coal gasification turns coal into syngas, which can be used to make electricity or turned into fuels like gasoline. This process mixes coal with oxygen and steam under heat and pressure.

Coal industry

Main pages: Category:Coal companies, Coal mining, Coal by country, Coal industry in China, Coal industry in Pakistan, Coal industry in India, and Coal companies of Australia

Coal is dug up from the earth in places called mines. About 8,000 million tons of coal are taken out each year, and most of it comes from deep underground mines. Coal can be used to make electricity, and some special kinds are used to help make metal.

Countries like China and India dig up lots of coal. Indonesia sends the most coal to other countries, followed by Australia and Russia. People buy and sell coal like other goods, and its price can change a lot. Some places are starting to use more wind and sun power instead of coal.

Damage to human health

Using coal as fuel can cause many health problems. When coal is burned, it releases harmful substances into the air, such as nitrogen oxides, sulfur dioxide, and tiny particles that can get deep into our lungs. These can lead to serious health issues like asthma, heart problems, and even lung cancer.

Coal mining and processing also pollute water and air, which affects the health of people living nearby. For example, breathing in coal dust can cause a disease called "black lung," where the lungs become damaged from the dust. In addition, coal plants produce waste called coal ash, which contains harmful materials that can hurt people and the environment.

Damage to the environment

Main article: Environmental impact of the coal industry

Coal mining and burning coal harm the environment in several ways. Mining can change the level and acidity of groundwater and water tables. Spills from power plants can pollute land and water and damage homes. Power plants that burn coal also use a lot of water, which can affect rivers and other land uses, especially in dry areas like the Thar Desert in Pakistan.

Burning coal releases sulfur dioxide, which can lead to acid rain. This rain can harm plants, animals, and water systems. Old coal mines can also cause problems, like the land sinking above tunnels or starting fires that burn for many years.

Climate change

The biggest long-term effect of using coal is that it releases carbon dioxide, a gas that causes climate change. Coal power plants were the biggest source of growth in global carbon dioxide emissions in 2018. For every unit of electricity made, coal releases about twice as much carbon dioxide as natural gas. To stop the world from warming too much, many coal power plants will need to close early.

Underground fires

Thousands of coal fires burn around the world. These fires can be hard to find and stop. They can make the ground sink, release dangerous gases, and start wildfires. Coal can catch fire on its own or from lightning strikes, and once it starts burning, it can continue until it runs out of oxygen.

Pollution mitigation and carbon capture

There are ways to lessen the harm that comes from burning coal for energy. These methods help protect both people and the environment.

One way is to treat the coal before it is burned. This can remove extra water and some harmful substances, making the coal burn better and produce fewer bad gases.

Another way is to clean the gases after the coal is burned. Special machines can catch many of the harmful gases and particles that come out of coal power plants.

Carbon capture and storage is a method that catches a gas called carbon dioxide from coal power plants and puts it deep underground where it cannot hurt the air. However, many plans to use this method have not worked out well because of cost and other challenges. Even with these helpful technologies, coal still causes a lot of harm to the environment.

Economics

In 2018, about US$80 billion was used to keep coal mines running, but not to start new ones. Over time, coal and oil might cost the world a lot of money each year. Some places, like India and the US, could be hurt a lot by these costs.

China makes the most coal and uses it for about 60% of its energy. However, many of China's coal power stations are not making money. Air pollution from storing and handling coal costs the US about $200 for every extra ton stored. Cutting air pollution helps both people and the economy.

Politics

Some countries, like China, India, Indonesia, Vietnam, Turkey, and Bangladesh, have been building or helping to build new power plants that burn coal. This has led to criticism from other countries, especially those affected by climate change, such as Vanuatu and Fiji. These islands worry about rising sea levels and erosion. In 2021, the G7 countries agreed to stop giving direct government support for new coal power plants around the world.

The efforts to reduce coal use are linked to the goals of the Paris Agreement to protect the environment and limit climate change.

Cultural usage

Coal is the official state mineral of Kentucky, and the official state rock of Utah and West Virginia. These US states have a long history connected to coal mining.

In some traditions, children who do not behave well might get a lump of coal instead of gifts from Santa Claus when they wake up on Christmas morning with their stockings ready. In Scotland, it is a special custom to give coal as a gift on New Year's Day as part of first-footing. This brings good luck and warmth for the year ahead.