What Is the Carbon Footprint of Coal Energy? A Life-Cycle Assessment

What Is the Carbon Footprint of Coal Energy? A Life-Cycle Assessment

Grace Smoot

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Coal has been the staple energy source in the world’s energy production since the Industrial Revolution. But considering the growing concern over climate change and our increasing carbon dioxide emissions, we had to ask: What is the carbon footprint of coal energy?

Coal energy has the highest carbon footprint of all energy types. Per kWh produced, coal emits 820 grams of carbon dioxide (CO2) on a life-cycle basis. It directly contributes to climate change and has various negative environmental effects. This is why coal is considered a dirty energy.

Coal is a main global fuel source with vast environmental implications. Keep reading to learn about the overall carbon footprint of coal energy and its carbon footprint throughout its life-cycle. 

How is Coal Energy Defined

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 (GHG) emissions upon combustion. 

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 black or brownish-black sedimentary rock containing energy stored by plants that lived in swampy forests over a hundred million years ago. 

To understand the carbon footprint of coal, it is important to tell you first that 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: Has the highest heating value of all types of coal and contains 86-97% carbon. It is used mainly by the metals industry and accounted for less than 1% of coal mined in the US in 2019.
  • Lignite: Has the lowest energy content of all types of coal due to its high moisture content and contains 25-35% carbon. It is used mainly to generate electricity and accounted for 8% of coal mined in the US in 2019.
  • Subbituminous: Has a lower heating value than bituminous coal and contains 35-45% carbon. It accounted for 44% of total US coal production in 2019.
  • Bituminous: Is the most abundant type of coal found in the US and contains 45-86% carbon. It accounted for 48% of total US coal production in 2019. It is used to generate electricity and acts as fuel and raw material for making cooking coal or in the iron/steel industries.

In 2020, 477 million tonnes (432.7 million tons)  of coal were consumed in the United States (US) alone, which equals 9.2 quadrillion British thermal units (Btu). This represents around 10% of total US energy consumption.  

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 methane, nitrous oxide, and chlorofluorocarbons.

Carbon footprint: the amount of greenhouse gases 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). 

What Is the Overall Carbon Footprint of Coal Energy

Coal is considered dirty energy because of its carbon footprint. On a life-cycle basis, coal emits 820 grams of carbon dioxide (CO2) equivalent per kWh of electricity produced, which is the highest out of all of the fuel types. 

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

And in 2019, the world collectively emitted 14.36 billion tons of CO2 from coal alone, higher than that from all other industries. 

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

Globally, coal demand fell by approximately 7% (500 million tons) between 2018 and 2020, partially because of the COVID-19 pandemic, and partially because of the increased interest in cleaner forms of energy, such as solar and wind power. But this global drop does not take into account regional imbalances

While consumption has decreased in the US and European Union (EU), consumption continued to increase in some Asian countries such as China and India.

Illustration of annual CO2 emissions of coal
Our World in Data: Annual CO₂ emissions from coal

The six largest coal-producing countries (amount per year) in the world are: 

  1. China – 3.7 billion tons (bt)
  2. India – 783 million tons (mt)
  3. United States – 640 mt
  4. Indonesia – 616 mt
  5. Australia – 550 mt
  6. Russia – 430 mt

Because coal remains an important fuel source for the global economy, it is important to understand what its carbon footprint is and how its carbon emissions affect the global climate change process.

To understand the carbon footprint of coal energy, we must assess its life-cycle and each stage’s carbon footprint. This life-cycle assessment (LCA) is a method to evaluate the environmental impacts of products and materials. Over the years, companies have strategically used LCA to research and create more sustainable products. So, let’s have a look at the LCA of coal energy!

The life-cycle stages of coal energyEach stage’s carbon footprint
Building of coal energy CO2 emissions from mining, construction, and transportation
Operating of coal energy CO2 emissions from operating the coal power plant
Building back of coal energy CO2 emissions from shutdown, decommissioning, remediation, and redevelopment

The total carbon footprint of coal would equal the carbon footprint from building + the carbon footprint from operating + the carbon footprint from building back. 

What Is the Carbon Footprint of Building Coal Energy

The carbon footprint of building coal energy includes 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, and building these components requires machinery that emits CO2. The boiler rooms, smokestacks, cooling towers, generators, and turbines are all components with a carbon footprint. 
  • Transportation: Coal is typically transported from mines to power plants by rail, river barge, or truck, all of which run on diesel fuel. Burning one gallon of diesel fuel produces 22.38 pounds of CO2

CO2 emissions at this stage occur when utilizing mining equipment, construction equipment, and vehicles to transport the coal to the power plant. 

What Is the Carbon Footprint of Operating Coal Energy

Coal-fired power plants operate in the following way:

  • 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.

CO2 emissions at this stage occur upon combustion and are also associated with the operation of the mechanical equipment (e.g., turbines and generators). 1 ton (2,000 pounds) of coal has 20.025 million British Thermal Units, the amount of heat required to raise the temperature of one pound of water 1° F. This means that 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. In 2019, the US burned 48% bituminous, 44.1% subbituminous, and 7.5% lignite coal, all of which have different carbon ratios and therefore will produce different amounts of CO2 per ton burned. 

What Is the Carbon Footprint of Building Back Coal Energy

Building back coal energy is a process that consists of four main stages to ensure that the power plant is decommissioned safely and effectively. These stages are:

  • Shutdown: Announcing closing and ceasing power production.
  • Decommissioning: Removing equipment and materials from the power plant, closing or complying with permits as necessary, and demolishing buildings. Typical permits include air pollution control, water withdrawal for cooling, water discharge, hazardous waste storage, fuel storage tanks, and flue gas stack (Federal Aviation Administration). 
  • Remediation: Cleaning up contamination to support new uses. This includes cleaning up coal combustion residuals (CCR), hazardous materials commonly referred to as coal ash. Remediation of coal ash is one of the largest industrial waste streams in the US. Disposal occurs at onsite landfills or surface impoundments (coal ash ponds). Coal ash can also be moved offsite to be recycled into other products. 
  • Redevelopment: Repurposing a new site or repowering for another generation technology or another commercial, industrial, or municipal application. Since coal power plants are usually located on land in or near downtown or around rivers, there is usually access to railroads, roadways, water, sewers, and other infrastructure. 

Coal power plant decommissioning is only loosely regulated. The time for physical decommissioning varies and can overlap with remediation and development. Coal plants have had a historical life expectancy of 46 years, but they can remain in operation from anywhere between 50 and 60 years

CO2 emissions at this final stage occur when utilizing construction equipment to demolish the buildings and construct new buildings in the old power plant’s place. 

Related: Are you interested in how the carbon footprint of coal energy compares to that of the other fossil fuels? Then check out the full article here: What Is the Carbon Footprint of Fossil Fuels? A Life-Cycle Assessment

What Role Does Coal Energy Play in Contributing to Climate Change

Climate change is arguably the most severe, long-term, global impact of coal energy. Every year, approximately 33 billion tonnes (36 billion tons) of CO2 are emitted from burning fossil fuels. 44% (15.8 billion tons) of this comes from coal. The carbon found in coal reacts with oxygen in the air to produce CO2 which, when released into the atmosphere, warms the earth by acting as a heating blanket. And a warmer earth comes with a host of negative side effects. 

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.

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 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 negative impact on the environment. These 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. 
  • 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 carbon dioxide 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

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.

Final Thoughts

We have relied on coal as our primary energy source for over a hundred years, but time is running out to reverse the effects of climate change caused by human CO2 emissions. One way to drastically reduce these emissions is to stop using coal for energy. Its carbon footprint across the building, operating, and building back phases is very high and causes numerous environmental drawbacks. The air and water pollution and toxic waste products could be mitigated if coal were not being used. Our atmosphere and Earth’s biota would all benefit if we reduced coal consumption.

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