Molly Ayala
Coal is a sedimentary deposit composed predominantly of carbon that is readily combustible. It is formed from plant remains that have been compacted, hardened, chemically altered, and metamorphosed by heat. Coal is primarily used as fuel to generate electric power, especially in the United States, where it accounted for about 19.5% of electricity generation in 2022. Coal is burned to heat water, creating steam, which then spins a turbine to produce electricity. Globally, coal supplies over one-third of electricity generation and plays a crucial role in industries such as iron and steel production.
| Characteristics | Values |
|---|---|
| How is coal used to generate electricity? | Coal is burned to heat water, creating steam. The steam then spins a turbine to produce electricity. |
| How much coal is used to generate electricity? | Coal supplies over one-third of global electricity generation. In 2022, coal accounted for about 19.5% of U.S. electricity generation. In 2019, about 23% of all electricity in the U.S. was generated by coal-fired power plants. In Britain, only 1.6% of electricity was generated by coal in the last two years. |
| Why is coal used for electricity generation? | Coal is a sedimentary deposit composed predominantly of carbon that is readily combustible. It is also the most carbon-intensive fossil fuel. |
| What type of coal is used for electricity generation? | Bituminous coal, subbituminous coal, or lignite. |
| Where is coal found? | The biggest coal deposit by volume is the Powder River Basin in Wyoming and Montana, which is estimated to have 1.07 trillion short tons of coal resources. |
| What are the issues with using coal for electricity generation? | Burning coal produces carbon dioxide and methane, which are harmful greenhouse gases. |
| What are the alternatives to using coal for electricity generation? | New innovations and technologies such as stability pathfinders and inertia measurement tools are being introduced to manage the electricity system without relying on coal. Carbon capture technology is also being explored as a way to reduce emissions from coal-fired power plants. |
| What are the trends in coal use for electricity generation? | Coal use for electricity generation is decreasing in most advanced economies and is expected to peak in emerging economies by 2027. |
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What You'll Learn
How coal generates electricity
Coal is a fossil fuel and a sedimentary deposit, composed predominantly of carbon. It is formed from plant remains that have been compacted, hardened, chemically altered, and metamorphosed by heat. Coal is readily combustible, and when burned, it reacts with oxygen in the air, turning all the stored solar energy into thermal energy, which is then released as heat.
Coal has been used to generate electricity since Thomas Edison’s Holborn Viaduct coal plant started generating electricity for public use in 1882. The plant burned coal to provide energy to light 1,000 lamps in the City of London. The principle of how coal generates electricity remains the same today. Coal is burned to heat water, creating steam. This steam then spins a turbine to produce electricity.
In coal-fired power plants, bituminous coal, subbituminous coal, or lignite is burned to heat boilers to about 1,000 degrees Fahrenheit to create high-pressure steam. The steam is piped to the turbines at pressures of more than 1,800 pounds per square inch. The turbines are connected to generators and spin them at 3,600 revolutions per minute to make alternating current (AC) electricity at 20,000 volts. The steam is then cooled, condensed back into water, and returned to the boiler to start the process over.
In pulverised coal combustion (PCC) systems, the coal is milled into a fine powder, increasing its surface area and allowing it to burn more quickly. The powdered coal is blown into the combustion chamber of a boiler, where it is burned at high temperatures. The hot gases and heat energy produced convert water in tubes lining the boiler into steam. The high-pressure steam turns a turbine, which generates electricity. After passing through the turbine, the steam is condensed and returned to the boiler to be heated again.
In IGCC systems, coal is not burned directly but is reacted with oxygen and steam to produce syngas, which is composed mainly of hydrogen and carbon monoxide. This syngas is then cleaned of impurities and burned in a gas turbine to generate electricity and produce steam for a steam power cycle.
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Coal's future as an energy source
Coal is a sedimentary rock formed from compacted and chemically altered plant remains over millions of years. It is composed predominantly of carbon and is readily combustible, making it useful for generating electricity. In coal-fired power plants, coal is burned to heat water and produce steam, which drives a turbine to generate electricity.
Coal is currently the most abundant source of electricity worldwide, providing more than 36% of global electricity. However, there is a growing trend towards phasing out coal-fired power plants due to their contribution to greenhouse gas emissions and climate change. For instance, in 2020, Britain had significant periods of coal-free electricity generation, and by October 2024, it plans to phase out coal completely from its power mix. Other countries in the European Union, such as Portugal, Belgium, Austria, Sweden, and Slovakia, have also taken steps towards decommissioning coal plants.
Despite the shift away from coal, it remains crucial in providing affordable and reliable electricity, especially in developing regions. Coal-fired power plants offer constant power that is available on demand, making them essential in alleviating energy poverty. Approximately 860 million people globally lack access to electricity, and coal has played a significant role in providing access to electricity for 1.7 billion people between 1990 and 2010.
As the world transitions to cleaner energy sources, the future of coal as an energy source is uncertain. In the United States, there are concerns about the reliability and affordability of moving away from coal to renewables. However, the retirement of coal power plants is being addressed through job relocation programs and the development of alternative energy sources, such as CCUS (carbon capture, utilization, and storage) and renewable energy technologies. Additionally, the abundance of coal reserves worldwide, estimated at 132 years of production in 2018, highlights the need for commercially viable technological pathways to zero emissions.
In summary, coal currently plays a significant role in global electricity generation, but its future is uncertain due to environmental concerns and the emergence of alternative energy sources. Ensuring a just transition away from coal, addressing energy security concerns, and developing viable technologies for coal utilization will be crucial in shaping coal's future as an energy source.
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Coal's role in industrial processes
Coal is a combustible black or brownish-black sedimentary rock with a high carbon content. It is formed from plant remains that have been compacted, hardened, chemically altered, and metamorphosed by heat over millions of years. Coal is classified into four main types, or "ranks", based on the coalification process: anthracite, bituminous, subbituminous, and lignite. The rank of coal depends on the amount of pressure and heat that acted on the plants over time, as well as the types and amounts of carbon it contains.
Coal is primarily used as a fuel for generating electricity, especially in the United States, where it accounted for about 23% of all electricity production in 2019. In coal-fired power plants, bituminous coal, subbituminous coal, or lignite is burned to heat water and create steam, which drives a turbine to produce electricity. This process releases thermal energy and greenhouse gases such as carbon dioxide and methane. Coal-fired power plants are also used to provide stability to the electricity system due to the heavy spinning turbines that sync with the grid's frequency.
In addition to electricity generation, coal plays a crucial role in industrial processes, particularly in the iron and steel industries. Metallurgical coal, also known as "'metcoal" or "coking coal", accounts for 10-15% of global coal use. It is used to make coke, which is a key component in the production of iron and steel. Certain types of bituminous coal, which contain high carbon content and low moisture, ash, sulfur, and phosphorus content, are suitable for steelmaking.
Coal is also used in cement production, carbon fibers and foams, medicines, tars, synthetic petroleum-based fuels, and home and commercial heating. Additionally, coal can be converted into synthetic fuels equivalent to gasoline or diesel through hydrogenation or carbonization processes. However, coal liquefaction emits more carbon dioxide than liquid fuel production from crude oil.
Historically, coal played a significant role in the Industrial Revolution, as the invention of the steam engine led to increased coal consumption. In 1700, Britain mined five-sixths of the world's coal, and by 1947, the country had 750,000 miners. While coal usage has declined in some advanced economies, it is still in high demand in emerging economies with rising electricity and industrial needs, such as China, India, Indonesia, and Vietnam.
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The environmental impact of coal
Coal is a sedimentary deposit composed predominantly of carbon. It is formed from plant remains that have been compacted, hardened, chemically altered, and metamorphosed by heat. Coal is readily combustible and has been used as a fuel source for electricity generation for over a century.
However, coal has significant environmental impacts, both in its mining and its use. The process of coal mining can be extremely disruptive to the environment, as it often involves removing large amounts of topsoil and rock to access coal seams. This can lead to erosion, habitat loss, and pollution. In 2022, surface mines (also called strip mines) were the source of about 63% of the coal mined in the United States. These mines involve clearing forests and stripping away the earth, leaving behind land that is incapable of supporting wildlife. Mountaintop removal and valley fill mining have affected large areas of the Appalachian Mountains in West Virginia and Kentucky, changing the landscape and polluting downstream waterways.
The burning of coal for electricity generation also has environmental consequences. Coal is a fossil fuel, and when burned, it reacts with oxygen in the air, turning stored solar energy into thermal energy and releasing greenhouse gases such as carbon dioxide, nitrogen oxide, sulfur dioxide, and methane. In 2022, CO2 emissions from burning coal for energy accounted for about 19% of total U.S. energy-related CO2 emissions and 55% of total CO2 emissions from the electric power sector. Coal combustion also emits fly ash particles, which contribute to air pollution and can damage the environment if not properly stored.
To mitigate the environmental impacts of coal, various methods are being explored, such as carbon capture, which separates and stores CO2 underground. Additionally, the reuse and recycling of waste produced from burning coal can reduce the environmental effects of coal consumption. As the world transitions to renewable energy sources, the environmental harms of coal mining and combustion are expected to decrease.
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Different types of coal
Coal is a fossil fuel that is essentially the altered remains of prehistoric vegetation. There are four main types of coal, each with different characteristics and uses. The type of coal depends on the types and amounts of carbon it contains and the amount of heat energy it can produce.
The first type of coal is anthracite, which is the highest rank of coal. It is a hard, brittle, and black lustrous coal, often referred to as hard coal. Anthracite contains 86%–97% carbon and generally has the highest heating value of all ranks of coal. It is the oldest type of coal, having formed from biomass that was buried 350 million years ago. Anthracite is used for space heating as it is one of the cleanest types of coal to burn, producing less smoke than other types.
The second type of coal is bituminous coal, which is the second-highest quality of coal. It contains 45%–86% carbon and is the most abundant type of coal. Bituminous coal is used to generate electricity and is important for making coking coal used in the iron and steel industry.
The third type of coal is subbituminous coal, which is black in colour and mainly dull. It contains 35% to 45% carbon and has a lower heating value than bituminous coal. Subbituminous coal is used primarily as fuel for steam-electric power generation.
The fourth type of coal is lignite, also known as brown coal, which is the lowest rank and lowest quality of coal. It contains 25%–35% carbon and has the lowest energy content of all coal ranks. Lignite is crumbly and has a high moisture content, which contributes to its low heating value. Lignite is used almost exclusively as fuel for electric power generation.
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Frequently asked questions
Coal is a sedimentary deposit composed predominantly of carbon that is readily combustible. Coal is burned to heat water, creating steam. The steam then spins a turbine to produce electricity.
Coal supplies over one-third of global electricity generation. In 2022, coal accounted for about 19.5% of U.S. electricity generation. In 2019, about 23% of all electricity in the United States was generated by coal-fired power plants.
Coal is formed from plant remains that have been compacted, hardened, chemically altered, and metamorphosed by heat. The biggest coal deposit by volume is the Powder River Basin in Wyoming and Montana, which was estimated to have 1.07 trillion short tons of in-place coal resources.
Coal use was once common in the industrial, transportation, residential, and commercial sectors. While coal is being gradually replaced in most countries, it is still crucial for iron and steel production. In 2022, global coal-fired generation reached an all-time high, with CO2 emissions from coal-fired power plants also reaching record levels.
To reduce emissions, governments and the coal industry are developing and deploying less polluting technologies, such as carbon capture, utilisation, and storage (CCUS). In Britain, coal will be phased out of the power mix by October 2024, with new innovations and technologies being introduced to manage the electricity system.
