Coal Energy Explained: All You Need to Know

Coal Energy Explained: All You Need to Know

Grace Smoot

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Coal has been and still is our largest source of electricity generation. But it is also our largest single source of carbon dioxide (CO2) emissions, which wreaks havoc on our environment. So, we had to ask: What is coal energy really, and how does it contribute to climate change?

Coal energy is created when coal is combusted in coal-fired power plants. Per kWh produced, coal energy emits 820 grams of CO2 on a life-cycle basis. It contributes to climate change and produces toxic waste products that degrade the planet.

Keep reading to find out all about what coal energy is, its global capacity, its carbon footprint, its environmental benefits and drawbacks, and how it can contribute to climate change.

The Big Picture of Coal Energy

Coal is one of the most important primary fossil fuels used for domestic energy generation and overseas transport. It is one of the cheapest for its energy content but also contributes to climate change via the release of greenhouse gas emissions (GHGs) upon combustion. 

How Is Coal Energy Defined

Coal is one of the three main fossil fuels (coal, oil, and natural gas). It is formed when plant and animal remains gradually build up on the earth’s surface and the ocean floor, mixing with sand, silt, and calcium carbonate. Under immense heat and pressure, some of these remains are converted into coal.

Coal: a combustible black or dark brown rock consisting mainly of carbonized plant matter, found mainly in underground deposits and widely used as fuel.”

Cambridge Dictionary

Coal energy is produced via the combustion of these pressurized plant and animal remains. The heat created upon combustion creates steam which spins a turbine and spins a generator to produce electricity.

What Are the Different Types of Coal Energy 

Not all coal is the same. In fact, there are 4 main types, or ranks, of coal depending on the type and amount of carbon the coal contains and the amount of heat energy the coal can produce:

  • Anthracite: The highest rank of coal. A hard, brittle, and black lustrous coal that is often referred to as hard coal because it contains the highest concentration of coal (86-97%) out of all coal ranks.
  • Bituminous: A middle rank of coal. It has a 45-65% carbon content and is typically used for electricity generation and steel making because it has a high heating (Btu) value.
  • Subbituminous: A middle rank of coal. It has a 35-45% carbon content and is typically used in electricity generation because it has a low-to-moderate heating value.
  • Lignite: The lowest grade of coal, also referred to as brown coal. It contains the least concentration of carbon (25-35%), has a high moisture concentration, has a low heating value, and is typically used in electricity generation.

Bituminous coal is produced the most, followed by subbituminous, lignite, and lastly anthracite.

Illustration of coal production by type from 1990 until 2020
International Energy Association: Coal production by type, World 1990-2020

Coal energy contributes directly to climate change, so let’s have a closer look at it next.

What coal energy isCoal energy is produced via the combustion of black or brownish-black sedimentary rock containing energy stored by plants that lived in swampy forests over a hundred million years ago.
What the different types coal energy areThe four ranks of coal are anthracite, bituminous, subbituminous, and lignite.
How coal energy worksCoal energy works by combusting coal in a power plant. This generates heat which turns water into steam, rotates turbines, and drives generators to produce electricity. 
The global capacity of coal energyCoal is a finite resource, and if we continue to use it at our current rate we can expect to run out of coal in approximately 100 years.
The carbon footprint of coal energyOn a life-cycle basis, coal emits 820 grams of carbon dioxide (CO2) equivalent per kWh of electricity produced.
The environmental benefits of coal energyAlthough coal does not benefit the environment, there are various methods to possibly mitigate its environmental impact.
The environmental drawbacks of coal energyBurning coal adds to the total level of CO2 in our atmosphere and expedites global warming. It also causes air and water pollution and creates toxic waste products which can leach into the environment.
Coal energy and climate changeCoal energy contributes to climate change by exacerbating temperature rise, sea-level rise, ice melting, and ocean acidification.

How Does Coal Energy Work

In general, coal energy works by combusting coal in coal-fired power plants to produce steam which turns a turbine and spins a generator to produce electricity.

How Does Coal Energy Actually Produce Energy

The process of generating coal energy begins with mining the coal, constructing the power plant, and transporting the coal from the mines to the power plant. 

  • Mining: The mining industry generates between 1.9 billion and 5.1 billion tons of CO2 annually, with an additional 400 million tons coming from power consumption. 
  • Construction: A coal-fired power plant has many components, including boiler rooms, smokestacks, cooling towers, generators, and turbines.
  • Transportation: Coal is typically transported from mines to power plants by rail, river barge, or truck.

Once the coal is mined and transported to a coal-fired power plant, it can be converted into energy via the following process:

  • Coal is mined into a fine powder before being blown into the combustion chamber of a boiler, where it is incinerated. 
  • The hot gases and heat energy convert water into steam. 
  • The steam is then passed into a turbine where it rotates the blades at a high speed. 
  • The blades then turn a generator which generates the electricity. 
  • Once the steam passes through the turbine it is condensed back into water and returned to the boiler chamber to be re-heated.
Illustration of how a coal-fired power plant works
APSense: How a Coal-Fired Power Plant Works

Coal plants have had a historical life expectancy of 46 years, but they can remain in operation from anywhere between 50 and 60 years

What Is the Global Capacity of Coal Energy

Fossil fuel consumption began with the Industrial Revolution, and consumption has increased exponentially over the past 70 years. The type of fuel we consume has shifted from solely coal, to coal and oil, and lastly to coal, oil, and NG. 

China is the world’s largest coal producer, consumer, and importer of coal. There are over 1,100 operational coal-fired power plants in China that account for for over 50% of global coal production and nearly 1/3rd of global coal consumption

Illustration of coal consumption in 2021
Our World in Data: Coal Consumption

The COVID-19 pandemic caused a temporary 4.8% decrease in global coal consumption. However, consumption rebounded 6.3% in 2021 and is predicted to return to all-time highs in 2022. 

Although the exact date at which we will run out of coal is unknown, if we continue to use it at our current rate we can expect to run out of coal in approximately 100 years. The resource is finite, and finding substitute energy sources will be necessary to sustain the global economy in the future. 

What Is the Carbon Footprint of Coal Energy

The carbon footprint is one of the ways we measure the effects of human-induced global climate change. It primarily focuses on the greenhouse gas (GHG) emissions associated with consumption, but also includes other emissions such as CH4, nitrous oxide, and chlorofluorocarbons.

Carbon footprint: the amount of greenhouse gasses and specifically carbon dioxide emitted by something (such as a person’s activities or a product’s manufacture and transport) during a given period

Merriam Webster

Basically, it is the amount of carbon emitted by an activity or an organization. This includes GHG emissions from fuel that we burn directly (e.g., heating a home, driving a car) and GHG emissions from manufacturing the products that we use (e.g., power plants, factories, and landfills). 

On a life-cycle basis, coal emits 820 grams of CO2 equivalent per kWh of electricity produced, which is second only to oil. 

Coal is the most polluting fossil fuel. Because it has a higher percentage of carbon than oil and natural gas (NG), it generates more CO2 per unit of energy than they do. Coal emits approximately 210 pounds (lbs) of CO2 per million British thermal units (Btu) compared to 160 for oil and 117 for NG.

Related: Are you interested in more about the carbon footprint of fossil fuel energy? Check it out in this article here: “What Is the Carbon Footprint of Fossil Fuel Energy?

Have a look at the illustration below to see the average life-cycle CO2 equivalent emissions of different energy sources and how they compare to coal.

Illustration of CO2 equivalent per energy source
World Nuclear Association: Average life-cycle CO2 equivalent emissions

When discussing the carbon footprint of coal energy, we must take into account carbon emissions across the energy’s building, operating, and building back phases.

The life-cycle stages of coal energyEach stage’s carbon footprint
Building of coal energyMining, construction, and transportation
Operating of coal energyOperation of the coal power plant
Building back of coal energyShutdown, decommissioning, remediation, and redevelopment

The world collectively emitted 13.98 billion tons of CO2 from coal in 2020, higher than that from all other industries. 

Illustration of CO2 emissions by fuel line
Our World in Data: CO2 emissions by fuel type, World

1 ton of coal creates 2.086 tons (4,172 lbs) of CO2 when it is burned. This number varies based on the type of coal that is being burned. Because coal consumption makes up a large part of our electricity generation and emits so much carbon, it is important to understand what its carbon footprint is and how its carbon emissions affect the global climate change process.

Related: Are you interested in more about the carbon footprint of coal energy? Check it out in this article here: “What Is the Carbon Footprint of Coal Energy?

How Environmentally Friendly Is Coal Energy

Coal is the world’s most abundant and cheapest fossil fuel source, but the combustion of coal produces over nearly 14 billion tons of CO2 emissions every year, which contributes significantly to global climate change.

Environmentally friendly: (of products) not harming the environment.”

Cambridge Dictionary

Coal is considered a dirty fuel source because of its high rate of CO2 emissions, toxic heavy metals, and other chemicals that contribute to global climate change. Because of this, the environmental benefits are scarce, and the environmental drawbacks are abundant. 

What Are The Environmental Benefits of Coal Energy

Although coal does not benefit the environment, there are ways to possibly mitigate its environmental impact. Various methods to do so include:

  • Carbon capture: Separating CO2 from coal emissions and recovering it in a concentrated stream for later injection underground (sequestration). This method is difficult, expensive, would increase the fuel needs of a power plant, and would likely double the price of electricity. 

Burning coal without adding to atmospheric CO2 levels and releasing toxic materials is a major challenge. There are ways to reduce the environmental impact, but they are often expensive and difficult to implement. 

What Are The Environmental Drawbacks of Coal Energy

The main disadvantage of coal energy is its significant contribution to climate change and global warming.

  • Atmospheric CO2: Levels of CO2 in our atmosphere have increased as a result of human emissions since the beginning of the Industrial Revolution in 1750. Emissions increased steadily to 5 billion tons per year in the mid-20th century before increasing exponentially to more than 35 billion tons per year at the end of the 20th century. The global average amount of CO2 in the atmosphere was about 280 parts per million (ppm) in 1750 but today registers at over 400 ppm. By the end of the 21st century, this number is expected to exceed 900 ppm. Burning coal adds to this total, which in turn amplifies the greenhouse effect and causes global warming. 
  • Global warming: This phenomenon occurs when CO2 and other air pollutants absorb sunlight and solar radiation in the atmosphere, trapping the heat and acting as an insulator for the planet. Since the Industrial Revolution, Earth’s temperature has risen a little more than 1 degree Celsius (C), or 2 degrees Fahrenheit (F). Between 1880-1980 the global temperature rose by 0.07C every 10 years. This rate has more than doubled since 1981, with a current global annual temperature rise of 0.18C, or 0.32F, for every 10 years. Experts claim that to avoid a future plagued by rising sea levels, acidified oceans, loss of biodiversity, more frequent and severe weather events, and other environmental disasters brought on by the hotter temperatures, we must limit global warming to 1.5C by 2040

Other environmental drawbacks include:

  • Air pollution: Burning coal releases numerous pollutants including mercury, lead, sulfur dioxide, nitrogen oxides, particulates, and other heavy metals. These cause numerous health problems including asthma, breathing difficulties, brain damage, heart problems, cancer, neurological disorders, and premature death. The US EPA does set pollutant limits, but many plants do not possess the necessary pollution control installed. 
  • Water pollution: A byproduct of coal energy production is the leftover coal ash residue that contaminates ponds, lakes, landfills, and other sites that could eventually lead to the contamination of waterways and drinking water supplies. Another concern is acid rock drainage from coal mines, the destruction of mountaintop streams and valleys by mountaintop removal mining, and the reliance of coal plants on local water supplies. 
  • Waste products: Coal contains large amounts of toxic heavy metals and chemicals that, if not contained properly in reservoirs, can leach into surface and groundwater supplies and cause problems such as cancer, birth defects, reproductive disorders, neurological damage, learning disabilities, and kidney disease. 

The easiest way to mitigate the environmental impact of coal is to simply not rely on it in the first place. Coal-burning power plants release toxic chemicals and heavy metals, produce coal ash, and contribute directly to global warming. 

How Does Coal Energy Contribute to Climate Change

Coal has powered our businesses, cars, and lights for over a century. But when burned it release large amounts of carbon and other GHGs, which directly contribute to climate change.

Climate change is arguably the most severe, long-term, global impact of fossil fuel combustion. Every year, approximately 33 bt of CO2 are emitted from burning fossil fuels. 44% (14.5 bt) of this comes from coal. The stored carbon found in coal reacts with oxygen in the air to produce CO2

CO2 emissions contribute to climate change in the following ways:

  • Melting of sea ice: Since 1979 arctic sea ice has declined by 30%. Sea ice plays a major role in regulating the earth’s climate by reflecting sunlight into space and providing habitat for animal species. If all of the glaciers on Earth melted, sea levels would rise by approximately 70 feet, effectively flooding out every coastal city on the planet. 
  • Changing precipitation patterns: Extreme weather events (e.g., hurricanes, floods, droughts) are becoming more common and more intense. Storm-affected areas will experience increased precipitation and flooding whereas areas located further from storm tracks will experience decreased precipitation and droughts.
  • Ocean acidification: The ocean absorbs 30% of the CO2 released into the atmosphere, which decreases the pH (increases the acidity) of the ocean. In the past 200 years, the pH of oceans has decreased by 0.1 pH units, which translates to a 30% increase in acidity. Aquatic life unable to adjust to this rapid acidification will die off. A prime example of this is coral bleaching, where coral expel the algae (zooxanthellae) living in their tissues as a result of changes in temperature, light, or nutrients. 

The more we reduce CO2 emissions, the more we slow the rate of temperature rise, sea-level rise, ice melting, and ocean acidification. When these rates are slowed, the earth’s biodiversity does not have to struggle to adapt to temperature and pH changes. People will not be displaced due to the flooding of coastal areas. And icebergs will continue to provide climate regulation. 

To help keep global temperature rise below 1.5C, as outlined in the Paris Agreement, we must shift at least 80% of our electricity generation to low carbon sources. To become net zero by 2050, we must also shut down 870 GW of coal capacity globally, or approximately 11% of all coal power capacity.

Final Thoughts

Coal energy is produced when the ancient remains of pressurized plants and animals (i.e. coal) is combusted in coal-fired power plants. The process creates steam which turns a turbine and spins a generator to produce electricity. We have relied on coal as a main source of energy for decades, but if we continue to use this finite resource at current rates we can expect to deplete it in approximately 100 years.

Coal is considered a dirty energy because of its high level of CO2 emissions when combusted and its ability to pollute our atmosphere, land, and water. It directly contributes to and exacerbates climate change. Our health and our planet’s health would be improved if we did not use coal as a source of energy. 

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