What is Coal: Definition, Composition, Types, Uses and Environmental Impact

Coal has been around for a long time. People have been using it for more than two centuries to power factories, cities and trains and to make steel. Even today, with solar and wind energy growing fast, coal is still widely used around the world for electricity and industry. So it helps to know what coal actually is, where it comes from, what it's made of and what problems it causes.

Table of Contents

• Definition
• Composition
• Types of Coal
• Uses of Coal
• Environmental Impact

Definition

Coal is a hard, black rock that can burn. It forms from dead plants and other organic material that got buried under soil and rock millions of years ago. Over time, heat and pressure turned all that organic stuff into a solid material packed with carbon. It's called a fossil fuel because it basically stores energy from the sun that ancient plants absorbed long ago.

Composition

Coal is mostly carbon, but it also has hydrogen, sulphur, oxygen, nitrogen and some minerals mixed in. The amount of carbon in coal, usually somewhere between 45% and 90%, decides how much energy it gives out when burned. More carbon means more energy and cleaner burning. Other things like moisture, ash and gases also affect how good or bad a particular coal sample is.

Types of Coal

Coal comes in different grades depending on how much it has changed over time. The more it has transformed under heat and pressure, the better the quality.

Peat

Peat is the starting point. It's not really coal yet. It's basically wet, partially rotted plant matter. It has very little carbon and a lot of moisture, so it doesn't burn well at all.

Lignite (Brown Coal)

This is the lowest grade of actual coal. It has about 25–35% carbon, feels soft and breaks apart easily and doesn't give out much energy when burned.

Sub-Bituminous Coal

A step up from lignite, this type has 35–45% carbon. It's mainly used to generate electricity and gives off less sulphur than the next grade up.

Bituminous Coal

This is the most common type of coal. It has 45–86% carbon and is used both for making electricity and for producing steel. The kind used in steel-making is called metallurgical or coking coal.

Anthracite

This is the best quality coal, with 86–97% carbon. It burns very cleanly with almost no smoke. It's rare and costs more than other types, so it's mostly used in specific industrial processes and for heating homes.

Uses of Coal

The main use of coal is to generate electricity. Power plants burn coal to heat water, create steam and spin turbines that produce electricity. Around the world, coal still makes up about 35–40% of electricity, especially in China, India, the US and parts of Southeast Asia. Coal is also essential for making steel. When it's heated without air, it turns into coke, which is then used in blast furnaces to extract iron from ore. On top of that, coal produces chemicals like coal tar, ammonia and benzene, which go into making medicines, dyes, fertilisers and synthetic fabrics. Activated carbon made from coal is used to clean water and purify air.

Environmental Impact

Coal is the biggest single source of CO2 emissions in the world, which makes it a major driver of climate change. When coal burns, it also releases sulphur dioxide, nitrogen oxides, mercury and fine particles, all of which are bad for air quality, human health and nature. Sulphur dioxide and nitrogen oxides mix with moisture in the air and come down as acid rain, which harms forests, rivers and buildings. Mining coal tears up land, pollutes groundwater and forces people out of their homes. The ash left behind after burning coal contains toxic metals and is difficult to dispose of safely. All of this has pushed many countries to move toward cleaner energy. But how fast that's happening depends a lot on each country's economy and circumstances.