Ameer Randolph
Coal is the most carbon-intensive fossil fuel and the dirtiest fuel overall. It is the most abundant and widely distributed fossil fuel source, and it supplies just over a third of global electricity generation. Coal combustion releases harmful gases such as carbon dioxide, nitrous oxide, sulfur dioxide, and nitrogen oxides, contributing to air pollution and climate change. While clean coal technologies aim to reduce emissions and utilize coal resources without contributing to global warming, the cost and energy intensity of these technologies are high. Natural gas is considered cleaner than coal, but it still has environmental impacts, including the potential for methane leaks and water pollution. Overall, transitioning away from fossil fuels towards nuclear and renewable energy sources is crucial to mitigating climate change and improving human health.
| Characteristics | Values |
|---|---|
| Coal compared to other fossil fuels | Coal is considered the dirtiest fossil fuel, emitting much more greenhouse gas than other sources. |
| Coal's environmental impact | Coal extraction and burning contribute to air and water pollution, including acid rain and the release of harmful substances such as mercury and heavy metals. |
| "Clean coal" technologies | New technologies aim to reduce emissions and increase efficiency, but they are costly and energy-intensive. |
| Global coal demand | Demand is projected to remain high, with emerging economies relying heavily on coal. |
| Alternatives to coal | Natural gas is considered cleaner than coal, but it contributes to climate change through methane leaks. |
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What You'll Learn
Coal is the most carbon-intensive fossil fuel
Burning coal produces about 15 billion tonnes of CO2 each year, contributing to global warming and climate change. Coal-fired power plants are a major source of CO2 emissions, with coal-fired electricity generation meeting about 37% of global electricity needs. In 2022, CO2 emissions from burning coal for energy accounted for about 19% of total US energy-related CO2 emissions and about 55% of total CO2 emissions from the electric power sector.
In addition to CO2, burning coal also releases other harmful emissions such as sulfur dioxide, nitrogen oxides, particulates, mercury, and heavy metals. These emissions contribute to air pollution, smog, respiratory illnesses, and lung disease. Mountaintop removal and valley fill mining methods used to extract coal can also have detrimental effects on the environment, altering landscapes and polluting downstream aquatic wildlife.
Recognizing the environmental impact of coal, efforts are being made to develop "clean coal" technologies to reduce emissions and utilize coal resources sustainably. Carbon capture, utilization, and storage (CCUS) technologies, for example, aim to reduce the carbon footprint of existing coal-fired power plants. However, these technologies are costly and energy-intensive, presenting challenges to their commercialization and widespread adoption.
Transitioning away from coal and other fossil fuels towards nuclear power or renewable energy sources is essential to mitigate climate change and improve human health. Nuclear energy and renewables, such as wind and solar power, have significantly lower death rates and environmental impacts compared to coal and other fossil fuels.
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Clean coal technologies aim to reduce emissions
Coal is the most abundant and widely distributed fossil fuel source in the world. However, burning coal releases over 15 billion tonnes of carbon dioxide (CO2) into the atmosphere each year, most of which comes from power generation. Coal also produces several other principal emissions, including sulfur dioxide, nitrogen oxides, particulates, mercury and other heavy metals, and fly and bottom ash.
Clean coal technologies (CCTs) aim to reduce these emissions and increase the amount of energy obtained per tonne of coal. CCTs are a new generation of energy processes that sharply reduce air emissions and other pollutants from coal-burning power plants. Compared to conventional coal-fired plants, power plants using CCTs can achieve higher conversion efficiencies and, thus, lower CO2 emissions per energy output. While the efficiency and emissions of conventional plants are over 28% and 1.3 t-CO2/MWh, respectively, CCTs can achieve efficiencies above 40% and emissions as low as 0.8 t-CO2/MWh.
There are several CCT methods for reducing emissions. One method is pre-combustion capture, which involves the gasification of coal to form a synthesis gas that can be shifted to produce an H2 and CO2-rich gas mixture. The CO2 can then be captured, separated, transported, and sequestered. Another method is post-combustion capture, which involves capturing CO2 from the exhaust gases of combustion processes. Oxy-fuel combustion is another method, where fossil fuels are burned in a mixture of recirculated flue gas and oxygen, rather than in air, which eliminates nitrogen from the flue gas and enables efficient, low-cost CO2 capture.
Additionally, improvements in pulverized coal combustion (PCC) technology can be achieved through increased temperature and pressure of the steam produced in supercritical (SC) and ultra-supercritical (USC) technologies. SC technology has been developed since the 1980s and typically produces steam with temperatures of 380-540 °C and a pressure of 221 bar. SC plants achieve efficiencies between 37% and 45%, with average CO2 emissions of 0.75-0.83 t/MWh. USC technology has a higher capital cost than subcritical units, but its higher efficiency reduces emissions and fuel costs to about 75% of subcritical plants.
The development and implementation of CCTs are important because, despite being the dirtiest and most dangerous fuel source, coal is still a major source of energy worldwide. In fact, coal accounts for around 60% of the global electricity mix, and about 2000 GWe of coal-fired generation capacity is currently operating globally. While nuclear and renewable energy sources are much cleaner and safer, the reality is that coal is still a critical source of energy for many parts of the world. Therefore, CCTs are necessary to reduce the environmental impacts of coal utilization and transition to a cleaner energy future.
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Coal mining and extraction impact water quality
Coal is the world's most abundant fossil fuel source and is used extensively as fuel in most parts of the world. However, burning coal releases over 15 billion tonnes of carbon dioxide into the atmosphere each year, contributing to global warming and climate change.
While coal is not considered a clean energy source, the term "clean coal" is increasingly being used for supercritical and ultra-supercritical coal-fired plants that do not use carbon capture and sequestration (CCS). These plants emit less CO2 than older plants, but still much more than nuclear or renewable energy sources.
The development of new "clean coal" technologies aims to address the issue of carbon dioxide emissions so that coal can be utilised for future generations without contributing to global warming. However, these technologies are costly and energy-intensive, and the commercialisation of this technology is a challenge.
Coal Mining and Extraction Impact on Water Quality
Coal mining and extraction have significant impacts on water quality, which can persist even after restoration efforts. Here are some ways in which coal mining and extraction affect water quality:
- Surface mining: This method involves clearing forests and removing layers of soil and rock to expose underground coal deposits. The removal of vegetation leaves the soil vulnerable to erosion, and precipitation can carry away loose topsoil into nearby waterways, causing river pollution.
- Mountaintop removal: This destructive form of surface mining uses explosives to remove the tops of mountains. The excess rock and soil are dumped into adjacent river valleys, creating valley fills that permanently bury headwater streams. Over 2,000 miles of headwater streams have been lost due to this practice, resulting in critical losses of wildlife habitat, clean water sources, and natural benefits such as nutrient regulation and flood control.
- Acid mine drainage: When certain substances, such as iron sulfide, are exposed to air and water, they can cause highly acidic water to drain from mines. This process, known as acid mine drainage, can contaminate nearby rivers, lakes, and aquifers with heavy metals like arsenic, copper, and lead.
- Coal washing and storage: After mining, coal is typically washed with water and chemicals to remove impurities. The resulting coal slurry, which contains toxic elements, must be stored properly. Improper storage in improvised ponds can lead to leaks and spills, contaminating rivers and streams with toxic sludge.
- Coal ash disposal: Coal-fired power plants produce over 100 million tons of coal ash annually in the United States. Most of this ash is stored in unlined ponds or pits, allowing heavy metals to escape into nearby waterways and contaminate drinking water sources. Exposure to coal ash has been linked to increased risks of cancer, heart damage, reproductive problems, and neurological disorders.
- Water consumption by coal plants: Coal-fired power plants rely on water for their operation, often sourcing it from nearby rivers or lakes. This can lead to water scarcity and impact aquatic ecosystems. Additionally, hot weather can make water supplies too warm for effective cooling, reducing electricity production when it is needed most.
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Coal releases harmful gases during combustion
Coal is the most carbon-intensive fossil fuel and the largest contributor to carbon dioxide (CO2) emissions from the electric power sector. Burning coal releases harmful gases, including carbon dioxide, sulfur dioxide, nitrogen oxides, particulates, mercury, and other heavy metals.
Sulfur dioxide and nitrogen oxides contribute to acid rain, which has detrimental effects on aquatic ecosystems and drinking water supplies. Acid rain also poses risks to human health, causing respiratory illnesses. Particulates released during coal combustion contribute to smog, haze, respiratory illnesses, and lung disease.
Mercury and other heavy metals emitted during coal burning have been linked to neurological and developmental damage in humans and animals. Additionally, coal-fired power plants produce fly ash and bottom ash, which are residues containing toxic substances.
The environmental impact of coal combustion has led to the development of "clean coal" technologies, aiming to reduce emissions and utilize coal resources sustainably. However, these technologies are costly and energy-intensive, presenting challenges in commercializing them to compete with alternative energy sources.
While natural gas is considered cleaner than coal in terms of certain emissions, it is not without its environmental impacts. Leaks of methane from natural gas pipelines contribute significantly to greenhouse gas emissions, and natural gas production through hydraulic fracturing has negative environmental consequences, including water pollution.
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Coal is more polluting than natural gas
Coal is considered the dirtiest fossil fuel and is far more polluting than natural gas. Burning coal produces about 15 billion tonnes of carbon dioxide each year, contributing massively to global warming. Coal-fired power plants emit not only carbon dioxide but also other toxic gases that negatively impact human health. These gases include nitrogen oxides, which contribute to smog and respiratory illnesses, and sulfur dioxide, which contributes to acid rain and respiratory illnesses. Coal combustion also produces particulates, which contribute to smog, haze, respiratory illnesses, and lung disease. Furthermore, coal mining changes the landscape, leading to deforestation and water quality devastation.
In contrast, natural gas is the cleanest fossil fuel. It emits 50 to 60 percent less carbon dioxide when combusted in a new, efficient natural gas power plant compared to a typical new coal plant. Natural gas produces negligible amounts of sulfur, mercury, and particulates. While natural gas extraction methods like hydraulic fracturing and acidizing create toxic wastewater, and natural gas drilling can lead to deforestation, these are problems associated with the extraction process rather than the fuel itself.
The combustion of natural gas does produce nitrogen oxides, but at much lower levels than gasoline and diesel used for motor vehicles. Every 10,000 US homes powered with natural gas instead of coal avoid the annual emissions of 1,900 tons of nitrogen oxides, 3,900 tons of sulfur dioxide, and 5,200 tons of particulates.
While natural gas is a better alternative to coal, it is still a fossil fuel and contributes to global warming. The development of new "clean coal" technologies is attempting to address the problem of coal's environmental impact so that the world's enormous resources of coal can be utilised for future generations without contributing to global warming. However, these technologies are costly and energy-intensive, and the greatest challenge is bringing the cost down sufficiently for "clean coal" to compete with nuclear power and renewables on the basis of near-zero emissions.
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Frequently asked questions
Clean coal refers to new processing technologies that reduce ash and sulfur levels in coal. These technologies aim to make coal a more viable fuel source for large marine engines, as well as reduce emissions and fuel costs.
No, coal is considered the dirtiest fossil fuel. It emits much more greenhouse gas than other sources, contributing to global climate change.
Natural gas is considered the cleanest fossil fuel. It produces fewer CO2 emissions and lacks significant emissions of nitrogen oxides and sulfur dioxide, which cause acid rain. However, natural gas production through hydraulic fracturing can have negative environmental consequences, and leaks of methane from pipelines may contribute more to climate change than coal.
Coal extraction and burning contribute to water and air pollution, as well as landscape changes. Coal is also the most carbon-intensive fossil fuel, producing over 15 billion tonnes of CO2 annually. Coal combustion releases sulfur dioxide, nitrogen oxides, and particulate matter, which have negative health and environmental impacts.
