Coal facts for kids

Kids Encyclopedia Facts

Quick facts for kids
Coal
Composition
Sedimentary rock
Bituminous coal, the most common coal grade
Primary	carbon
Secondary	hydrogen sulfur oxygen nitrogen

Coal is a dark brown or black sedimentary rock that burns easily. It is found underground in layers of rock known as coal seams. This dark rock is made mostly of carbon. It also contains tiny amounts of other elements like hydrogen, sulfur, oxygen, and nitrogen. Coal is called a fossil fuel. It formed from ancient plants that decayed into peat millions of years ago. Intense underground heat and deep pressure slowly changed this buried material into hard rock.

People burn coal mainly to create heat and energy. Humans have known about coal for thousands of years, but its use exploded during the Industrial Revolution. The invention of the steam engine meant machines needed lots of fuel. Today, power stations burn coal to power generators for electricity. Factories also use coal to make strong metals like iron and steel.

However, using coal brings big challenges. Digging up and burning coal causes damage to nature and human health. It releases harmful smoke, dirt, and greenhouse gas emissions. Coal is the single largest creator of carbon dioxide, a gas that drives climate change. Because of this, leaders around the world are working on an energy transition. Many countries are choosing to phase out coal power and switch to cleaner choices like solar power and wind power.

How coal forms underground over millions of years
- Chemical changes inside the rock
The different types of coal
History of coal use through time
What is inside coal?
How do we use coal today?
The global coal business
How coal harms human health
Environmental impacts of coal
- Impact on world climate
- Burning underground coal seams
Cleaning up the coal industry
Traditions and folklore
Images for kids
Related pages
See also

How coal forms underground over millions of years

Example chemical structure of coal

The natural recipe that turns dead plants into rock is called coalification. Long ago, dense green swamps and giant wetland forests covered warm parts of our planet. When giant trees and ferns died in these soggy places, they sank under water and mud. Because the mud kept out air, it stopped normal oxidation. The rotting plants turned into a thick, spongy layer called peat.

Over millions of years, rivers washed sand and dirt over these prehistoric peat bog areas. The weight of all these new rocks created crushing weight and heat. This deep baking squeezed out water, methane, and gas. What remained was a concentrated rock made almost entirely of pure carbon.

Most of our coal formed during two ancient geologic periods: the Carboniferous and the Permian. Around 300 million years ago, strange lycophyte forests grew across the land. Some scientists believe that early trees developed a tough woody substance called lignin. At that time, tiny microbes and fungi had not yet figured out how to rot this tough wood. As a result, huge piles of fallen wood became buried and turned into rich beds of fossil energy.

Chemical changes inside the rock

Deep inside the Earth, heat causes chemical changes that slowly bake the rock. This natural cooking is called carbonization. Plant matter starts with water and woody tissues made of cellulose and lignin. As heat cooks the buried wood, reactions like dehydration remove moisture. Another step called decarboxylation forces out oxygen and carbon dioxide.

As carbonization continues, the molecules arrange themselves into tighter networks called aromatic compound rings. These rings bunch together into strong flat layers that look like graphene. At the same time, the tiny pores inside the stone shrink, making the coal heavier, harder, and shinier.

The different types of coal

Coastal exposure of the Point Aconi Seam in Nova Scotia

Coal ranking system used by the United States Geological Survey

Geologists rank coal based on how much heat and pressure it endured. Deeper rocks undergo more extreme baking, which increases their metamorphic grade. Higher ranks have more carbon and produce more heat when burned.

Peat is not quite coal yet. It is a soft, wet brown layer of squashed moss and leaves found in bogs.
Lignite is often called brown coal. It is soft, crumbly, and holds lots of moisture. It is the lowest rank of coal and produces lots of smoke.
Sub-bituminous coal is darker and firmer than lignite. Power stations burn it around the world to produce steam.
Bituminous coal is a dense, black stone. It is very common and contains smooth, shiny bands. People use it to power electric stations and make metal.
Anthracite coal is the hardest and highest grade. It looks glossy, feels clean, and burns with a hot, blue flame. It is popular for space heating.
Graphite is an extremely baked form of pure carbon. It does not burn easily, so humans use it inside writing pencils or as a dry lubricant.
Cannel coal is a fine-grained type of coal that catches fire easily and burns with a bright flame.

History of coal use through time

Chinese coal miners in an illustration of the Tiangong Kaiwu encyclopedia, published in 1637

People have used coal for a very long time. Thousands of years ago during the Bronze Age, people in ancient Britain placed shiny coal into ceremonial fires. In China, craftspeople carved lovely dark beads and ornaments out of lignite as early as 4000 BC. By 1000 BC, workers at the famous Fushun mine in China used coal fires to melt and shape copper.

When the explorer Marco Polo visited China during the 13th century, he was amazed to see people burning strange "black stones" that kept burning longer than wood. Across Europe, ancient Romans gathered coal to dry grain and heat rooms in Roman villa buildings. Roman blacksmiths also burned coal to craft weapons and tools out of iron ore.

Coal miner in Britain, 1942

During the Middle Ages, waves washed chunks of black stone onto British beaches. People called this washed-up fuel "seacoal." Soon, surface supplies ran low. Miners began digging deep pits and shafts down into the ground, calling the fuel "pitcoal." By the late 1500s, British cities like London had cut down most nearby forests for firewood. Families turned to coal to heat their fireplaces and cook meals.

The Industrial Revolution changed the world forever. Powerful steam engine machines took over jobs previously done by a water wheel or working horses. Factories, trains, and ships all needed heaps of energy. By 1700, Great Britain mined the vast majority of the world's coal. By the 1900s, a huge network of steam locomotive tracks moved goods and passengers across entire continents.

What is inside coal?

Firewood combusting into coal in a wood-burning stove, 2025

Coal is not a single clean mineral. It is a messy mixture of organic parts and ancient minerals. The best black coal contains mostly carbon, which provides thermal energy when burned. It also contains trapped elements like hydrogen, oxygen, and nitrogen.

Coal also contains minerals that cannot burn. When coal burns completely away, these leftover mineral bits form powdery fly ash and heavier bottom ash. Inside this waste are tiny traces of natural metals, including arsenic, Selenium, and mercury. In nature, these metals stay safely trapped inside solid rock. When coal burns, these harmful elements escape into the air unless caught by special filters. Coal also contains mineral crystals called iron pyrite, which release stinky sulfur smoke when burned.

How do we use coal today?

Most mined coal is burned directly as a fuel to create heat or generate power. A single kilogram of good coal packs roughly 24 megajoules of energy. That concentrated power makes it useful for heavy industries.

Making electricity

Electricity generated from coal around the world

Most coal burned today is called thermal coal. Power plants crush this rock into a fine powder and spray it into a giant furnace boiler. The intense fire boils water into super-hot steam. This pressurized steam rushes through pipes to spin giant blades inside a turbine. The spinning turbine powers an electrical generator that produces the electrical current for homes and schools.

Some modern facilities use a system called coal gasification. Instead of burning the rock directly, they turn the coal into a clean-burning fuel gas called syngas. This gas can run inside a modern gas turbine, creating electricity with less smoke.

Making steel with coke

Coke oven at a smokeless fuel plant in Wales

You cannot build skyscrapers, bridges, or cars without steel. Making steel requires an ultra-pure fuel called coke. Factory workers make coke by baking chunks of metallurgical coal in huge ovens without any oxygen. The heat drives away gases and moisture, leaving behind a hard, grey, porous block of nearly pure carbon.

Workers dump coke into a huge blast furnace alongside raw iron ore. The burning coke creates hot carbon monoxide gas, which strips oxygen atoms away from red hematite ore. This chemical reaction produces molten pig iron, which is later refined into strong, durable steel.

Making chemicals and synthetic fuels

Coal is also a handy raw material for the chemical industry. By gasifying coal into syngas, chemists produce basic ingredients like methanol, pure hydrogen, and ammonia. Companies use these chemicals to manufacture farm fertilizers, plastics, and medicines.

Under special heat and pressure, engineers can transform solid coal into liquid fuels like gasoline and diesel. This process is called coal liquefaction. It allows countries without oil wells to produce liquid transportation fuels, although doing so creates large amounts of greenhouse gases.

The global coal business

Coal miners in the Appalachia region in 1974

Every year, machines and miners dig billions of tonnes of coal out of the Earth. Around half of this coal comes from giant open surface pits, while the rest comes from deep tunnels underground. The coal mining industry employs millions of workers worldwide. Underground mining can be dangerous because tunnels can collapse, and trapped pockets of coalbed methane can ignite if not properly ventilated.

China is the biggest coal producer and consumer in the world, mining almost half of the global supply. India ranks as the second-largest user. Meanwhile, countries like Indonesia and Australia dig up enormous amounts of coal and export it on massive ships to other nations.

How coal harms human health

Deaths caused by fossil fuel pollution compared to clean energy sources

When coal burns, its smokestacks release fine soot and toxic gases. Breathing in dirty air can lead to serious illnesses like asthma and damage human lungs. Tiny airborne dust specks known as PM2.5 particulates are especially dangerous because they can sink deep into the bloodstream.

In the past, burning soft coal inside home fireplaces created dangerous city fogs, like the historic London smog. Today, doctors estimate that coal smoke causes hundreds of thousands of premature illnesses every year across the globe.

Coal miners face health dangers too. Working underground and breathing in fine rock dust for years can cause a lung disease called coalworker's pneumoconiosis, commonly known as "black lung." Modern mines use water sprays and powerful fresh-air fans to protect workers' breathing.

Environmental impacts of coal

Aerial view of the Kingston Fossil Plant coal fly ash slurry spill

Digging up coal changes the local landscape. Surface mining removes forests, soil, and hilltop rocks. It can also disrupt clean groundwater supplies and lower the local water table. Power stations that burn coal produce millions of tons of muddy ash waste. If an ash pond breaks, such as during the Kingston Fossil Plant coal fly ash slurry spill, toxic mud can slide into nearby rivers, harming fish and wildlife.

When coal containing sulfur burns, it releases sulfur dioxide gas into the clouds. This gas mixes with water droplets in the sky to form acid rain. Acid rain can damage trees, dissolve stone statues, and make lake water too acidic for fish to survive.

Impact on world climate

Chart showing the warming influence of greenhouse gases like carbon dioxide

The biggest problem with coal is its role in climate change. Coal contains more carbon than oil or natural gas. When that carbon burns, it joins with oxygen from the air to make billions of tonnes of carbon dioxide gas. Carbon dioxide acts like a warm blanket around our planet, trapping solar heat in the atmosphere. This warming effect changes weather patterns, melts glaciers, and raises ocean levels.

To protect the planet, world leaders signed the Paris Agreement. This international treaty aims to slow down global temperature rise. Achieving this goal requires countries to replace coal power plants with clean, sustainable energy sources.

Burning underground coal seams

Castle Gate Power Plant in Utah

Sometimes, coal layers catch fire beneath the earth. A strike from lightning, a forest brushfire, or even heat from spontaneous combustion can light an exposed coal seam. Once an underground coal-seam fire starts, it can burn out of control for decades because it feeds on surrounding rock layers. The famous Brennender Berg fire in Germany has been burning underground since 1668. These fires crack open the ground above, pour smoke into the air, and waste valuable natural resources.

Cleaning up the coal industry

Emissions controls installed at a coal power plant

Engineers have designed clever tools to reduce the amount of smoke escaping from power plants. Some plants wash crushed rock before burning it, a process called refined coal. Washing cleans away chunks of dirt, rocks, and sulfur-bearing pyrite.

Inside plant smokestacks, workers install chemical scrubbers for flue-gas desulfurization. These scrubbers spray wet limestone mist into the hot gas to trap sulfur before it reaches the clouds. Power plants also use electrostatic precipitators. These tools use static electricity, like a balloon sticking to your hair, to pull dark ash particles out of the smoke.

Scientists are also testing carbon capture and storage systems. This technology traps carbon dioxide gas straight from the smokestack, compresses it, and pumps it deep underground into ancient rock layers. However, building these systems is very expensive and consumes extra energy.

Traditions and folklore

Coal has inspired many cultural traditions. In the United States, coal is honored as the official state mineral of Kentucky, and the state rock of Utah and West Virginia.

A famous holiday tradition says that children who misbehave throughout the year will find a black lump of coal tucked inside their Christmas stocking instead of candy. In Scotland and northern England, people celebrate a warm New Year tradition called first-footing. Visitors bring a gift of coal across the doorstep on New Year's Day to bring good luck and ensure the family home stays warm and cozy all year long.