Table of Contents
- What is coal?
- Who has coal?
- What is coal used for?
- How harmful is coal to the environment?
- What is the outlook for coal?
1. What is coal?
Coal is a combustible black or brownish-black sedimentary rock composed mostly of carbon and hydrocarbons. Coal is compressed plants that lived hundreds of millions of years ago. For millions of years, a layer of dead plants at the bottom of the swamps was covered by layers of water and dirt, trapping the energy of the dead plants. The heat and pressure from the top layers helped the plant remains turn into what we today call coal. The carbon and hydrocarbons in these plants is what gives coal its energy.
Source: National Energy Education Development Project (public domain)
A. Types of coal
Coal is classified into four main types, or ranks (anthracite, bituminous, subbituminous, and lignite), depending on the amounts and types of carbon it contains and on the amount of heat energy it can produce. The rank of a deposit of coal depends on the pressure and heat acting on the plant debris as it sank deeper and deeper over millions of years. For the most part, the higher ranks of coal contain more heat-producing energy.
Anthracite contains 86-97% carbon, and generally has a heating value slightly higher than bituminous coal. It accounts for less than 0.5% of the coal mined in the United States.
All of the anthracite mines in the United States are located in northeastern Pennsylvania.
Bituminous coal contains 45-86% carbon. Bituminous coal was formed under high heat and pressure. Bituminous coal in the United States is between 100 to 300 million years old. It is the most abundant rank of coal found in the United States, accounting for about half of U.S. coal production. Bituminous coal is used to generate electricity and is an important fuel and raw material for the steel and iron industries.
West Virginia, Kentucky, and Pennsylvania are the largest producers of bituminous coal.
Subbituminous coal has a lower heating value than bituminous coal. Subbituminous coal typically contains 35-45% carbon. Most subbituminous coal in the United States is at least 100 million years old. About 44% of the coal produced in the United States is subbituminous.
Wyoming is the leading source of subbituminous coal.Wyoming is the leading source of subbituminous coal.
Lignite is the lowest rank of coal with the lowest energy content. Lignite coal deposits tend to be relatively young coal deposits that were not subjected to extreme heat or pressure, containing 25%-35% carbon. Lignite is crumbly and has high moisture content. There are 20 lignite mines in the United States, producing about 7% of U.S. coal.
Most lignite is mined in Texas and North Dakota. Lignite is mainly burned at power plants to generate electricity.
2. Who has coal?
The United States is home to the largest estimated recoverable reserves of coal in the world. In fact, we have enough coal to last more than 200 years, based on current production levels. Coal is produced in 25 states spread across three coal-producing regions. In 2011, approximately 72% of production originated in five states: Wyoming, West Virginia, Kentucky, Pennsylvania, and Texas.
In the U.S. coal is mainly found in three large regions, the Appalachian Coal Region, the Interior Coal Region, and Western Coal Region (includes the Powder River Basin).
Appalachian Coal Region:
- More than one-third of the coal produced in the United States comes from the Appalachian Coal Region.
- West Virginia is the largest coal-producing state in the region, and the second largest coal-producing state in the United States.
- Coal mined in the Appalachian coal region is primarily used for steam generation for electricity, metal production, and for export.
Interior Coal Region:
- Texas is the largest coal producer in the Interior Coal Region, accounting for almost one-third of the region’s coal production.
- This region has mid-sized surface mines.
Western Coal Region:
- Over half of the coal produced in the United States is produced in the Western Coal Region.
- Wyoming is the largest regional coal producer, as well as the largest coal-producing state in the nation. Nine of the top ten producing coal mines in the United States are located in Wyoming.
- This region has many large surface mines.
- Some of the largest coal mines in the world are in the Western Coal Region.
Outside of the U.S., Russia, China, Australia and India have the largest proved recoverable coal reserves.
- How large are U.S. coal reserves?
- From what country does the U.S. import the most coal?
- To what country does the U.S. export the most coal?
3. What is coal used for?
About 93% of the coal consumed in the United States is used in the electric power sector. The remaining coal is used as a basic energy source in many industries including steel, cement, and paper. The major uses of coal are:
For electric power
Coal is used to create about 37% of all electricity generated in the United States. Power plants burn coal to make steam. The steam turns turbines (machines for generating rotary mechanical power) that generate electricity.
In addition to companies in the electric power sector, industries and businesses with their own power plants use coal to generate electricity.
Coal is also used to make steel. Coal is baked in hot furnaces to make coke, which is used to smelt iron ore into iron needed for making steel. It is the very high temperatures created from the use of coke that gives steel the strength and flexibility for things like bridges, buildings, and automobiles.
The concrete and paper industries also use large amounts of coal.
4. How harmful is coal to the environment?
Although coal is abundant and fairly inexpensive relative to other sources of electricity, its use produces several types of emissions that harm the environment. Coal emits sulfur dioxide, nitrogen oxide, and heavy metals (such as mercury and arsenic) and acid gases (such as hydrogen chloride), which have been linked to acid rain, smog, and health issues. Coal also emits carbon dioxide, a greenhouse gas. In 2011, coal accounted for 34% of the energy-related carbon dioxide emissions in the United States. Coal mining can also have a negative impact on ecosystems and water quality, and alter landscapes and scenic views.
5. What is the outlook for coal?
The “natural gas revoluton” in the U.S. has decreased the demand for coal as natural gas has become a cheaper alternative for generating electricity. With decreased demand for U.S. coal at home, coal companies have turned instead to the international market and been increasingly exporting coal to Asia and Europe where prices have not slumped.
- Animated global map – coal consumption growth
- Recent coal articles
- Fuel Competition in Power Generation
- Quarterly Coal Report
- Coal Projections Through 2035
- Energy Explained: Coal
- Energy Explained: Electricity in the United States
- Clean Coal Technology Compendium (NETL)
**The information on this website was obtained from various pages of the U.S. Department of Energy website (www.energy.gov) and the U.S. Environmental Protection Agency website (www.epa.gov). The data on this website was obtained from various pages of the U.S. Energy Information Administration website (www.eia.gov.). Please consult those websites for further information.