Air Pollution: Power Generation's Dark Side

Burning fossil fuels to generate power is a major cause of air pollution. Fossil fuels include coal, natural gas, and petroleum-based fuels such as diesel and heavy fuel. In 2022, about 35% of the world's electricity came from burning coal, a significant source of harmful air pollutants. Coal-fired power plants emit nitrogen oxides, sulphur dioxide, particulate matter, and mercury, which have detrimental effects on both human health and the environment. Nitrogen oxides contribute to ground-level ozone and fine particle pollution, aggravating heart and lung diseases and causing respiratory issues. Sulphur dioxide causes acid rain, which is harmful to plants, aquatic life, and can worsen respiratory and heart conditions. Particulate matter results in haze and, coupled with ozone, contributes to asthma and chronic bronchitis. Mercury is a potent neurotoxin, affecting the nervous system and brain functions, particularly in children.

Other fossil fuels also contribute to air pollution. Natural gas (methane) and oil power plants emit significant air pollutants, and oil and gas exploration, drilling, storage, and transportation can create additional air pollution issues.

To reduce air pollution from power generation, a transition to clean, renewable, and non-combustion sources of electricity is critical. Sources such as solar, wind, geothermal, and tidal power are zero-emission sources that can dramatically reduce health risks and premature deaths associated with air pollution and climate change.

Coal-fired power plants

Mercury, a toxic heavy metal emitted during coal burning, can damage the nervous, digestive, and immune systems and poses a serious threat to child development. Just 1/70th of a teaspoon of mercury deposited in a 25-acre lake can contaminate the fish to unsafe levels for consumption. In 2014, US coal power plants emitted 45,676 pounds of mercury, according to the Environmental Protection Agency's National Emissions Inventory.

Sulfur dioxide (SO2) is produced when sulfur in coal reacts with oxygen. SO2 combines with other molecules in the atmosphere to form small, acidic particulates that can penetrate human lungs. It is linked to asthma, bronchitis, smog, and acid rain, which damages crops, ecosystems, and water sources. US coal power plants released over 3.1 million tons of SO2 into the atmosphere in 2014.

Nitrogen oxides (NOx) are visible as smog and irritate the lungs, exacerbating asthma and making people more susceptible to chronic respiratory diseases. US coal power plants emitted more than 1.5 million tons of NOx in 2014.

Particulate matter, often referred to as soot, is the ashy grey substance in coal smoke. It is linked to chronic bronchitis, aggravated asthma, cardiovascular issues such as heart attacks, and premature death. US coal power plants emitted 197,286 tons of small airborne particles (10 micrometers or less in diameter) in 2014.

Additionally, coal-fired power plants released other harmful pollutants in 2014, including 41.2 tons of lead, 9,332 pounds of cadmium, 576,185 tons of carbon monoxide, 22,124 tons of volatile organic compounds (VOCs), and 77,108 pounds of arsenic.

The impact of coal-fired power plants on human health and the environment is significant, and it is crucial to implement measures to reduce these harmful emissions and protect public health and the planet.

Burning fossil fuels

One of the primary emissions from burning fossil fuels is carbon dioxide (CO2), a greenhouse gas. Greenhouse gases trap heat in the Earth's atmosphere, leading to global warming and climate change. According to the Intergovernmental Panel on Climate Change (IPCC), emissions from fossil fuels are the dominant cause of global warming. In 2018, 89% of global CO2 emissions came from fossil fuels and industry. The average global temperature has already increased by 1°C, and warming above 1.5°C risks further sea-level rise, extreme weather, biodiversity loss, species extinction, food scarcity, and worsening health and poverty for millions worldwide.

In addition to CO2, the combustion of fossil fuels releases other harmful substances, including carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter (PM), and heavy metals such as mercury. These pollutants have detrimental effects on both the environment and human health. For example, SO2 causes acid rain, which is harmful to plants and aquatic life, and it also exacerbates respiratory illnesses and heart diseases, particularly in children and the elderly. NOx contributes to ground-level ozone, which irritates and damages the lungs. PM, including ash and soot, leads to hazy conditions and contributes to asthma and chronic bronchitis, with fine PM also believed to cause emphysema and lung cancer.

The health impacts of burning fossil fuels are significant. According to recent research, air pollution from fossil fuels is responsible for about one in five deaths worldwide, or approximately 8.7 million deaths in 2018. This makes fossil fuel pollution a deadlier global health risk than HIV, tuberculosis, and malaria combined. The health consequences of air pollution disproportionately affect certain demographics, including children, older individuals, people on low incomes, and people of colour, who typically reside in urban areas that experience the worst impacts.

Transitioning from fossil fuels to renewable and alternative energy sources is crucial for mitigating the health and environmental impacts of air pollution. By reducing emissions of harmful substances, we can not only address climate change but also significantly reduce the number of premature deaths attributed to air pollution from fossil fuels.

Nitrogen oxide emissions

Nitrogen oxides (NOx) are produced in combustion processes, mostly by the direct combination of atmospheric oxygen and nitrogen in flames. NOx gases are usually produced from the reaction between nitrogen and oxygen during the combustion of fuels, such as hydrocarbons, especially at high temperatures. Power plants that burn fossil fuels are a significant source of NOx emissions. In 2015, coal-fired power plants contributed to about 34% of NOx emissions in India. In the US, thermal power plants generated about 26.6% of total NOx emissions in 2010.

NOx emissions from electricity generation in the UK were fairly constant from 1970 onwards until 1990. The increased use of gas in electricity generation in the early 1990s, along with more modern power stations, led to a significant reduction in NOx emissions from the sector until 2000. However, since 2006, coal use and the total amount of fuel used in electricity generation have substantially decreased.

NOx gases contribute to the formation of smog, acid rain, and ground-level ozone. They can irritate and damage the lungs and are associated with increased respiratory-related hospitalizations, increased susceptibility to respiratory infections, and increased frequency of respiratory symptoms. NOx emissions have been linked to increased mortality, especially in children and the elderly.

To reduce NOx emissions from power plants, various control measures can be implemented. These include the use of low NOx burners during the combustion phase or selective catalytic and non-catalytic converters during the post-combustion phase. Additionally, burning low-sulfur-content coal, co-firing wood chips with coal, and pretreating and processing coal can help reduce NOx emissions. Implementing flue gas desulfurization systems, state-of-the-art flue gas treatment, local emission limits, and phasing out the most polluting power plants can also effectively reduce NOx emissions.

Sulphur dioxide emissions

Sulphur dioxide (SO2) is a colourless, foul-smelling toxic gas and air pollutant. It is emitted by the burning of fossil fuels, such as coal, petroleum oil, or diesel, and other materials that contain sulphur. Power plants, commercial and institutional boilers, internal combustion engines, and vehicles are some of the largest sources of SO2 emissions.

Health Effects

SO2 can irritate the skin and mucous membranes of the eyes, nose, throat, and lungs. It can cause inflammation and irritation of the respiratory system, particularly during heavy physical activity. High concentrations of SO2 can affect lung function, worsen asthma attacks, and exacerbate heart disease. It also increases the risk of hospital admissions or emergency room visits, especially among children, older adults, and people with asthma. Longer exposures at high levels can aggravate existing heart and lung conditions.

Environmental Effects

SO2 contributes to air pollution by forming secondary pollutants, such as sulfate aerosols, particulate matter, and acid rain. Acid rain can damage trees and plants, inhibit plant growth, and harm sensitive ecosystems and waterways. SO2 also contributes to the formation of thick haze and smog, which can reduce visibility and affect air quality.

Reducing SO2 Emissions

SO2 emissions have been declining due to federal regulations and the transition to cleaner fuels. Power plants have implemented various methods to reduce SO2 emissions, including burning low-sulfur-content coal, co-firing wood chips with coal, and pretreating and processing coal to reduce undesirable compounds. Additionally, pollution control devices such as bag-houses, electrostatic precipitators, and wet scrubbers are used to treat combustion gases and remove particulate matter.

SO2 Emissions from Power Generation

Power plants that burn fossil fuels, particularly coal, are a significant source of SO2 emissions. In 2015, coal-fired power plants contributed to about 49% of SO2 emissions in India. Similarly, in the United States, about 62% of electricity generation in 2022 came from fossil fuels, and coal-fired power plants remain one of the biggest sources of SO2 emissions.

Mercury emissions

Mercury is a dangerous heavy metal that poses risks to both human and animal health. Power plants are a significant source of mercury emissions, with coal-fired power plants being the primary contributor. The combustion of coal releases mercury into the atmosphere, and it is estimated that power plants account for 42% of total mercury emissions in the United States. Additionally, biomass, which is considered a renewable fuel, also contributes to mercury emissions. The issue of mercury emissions from power plants has gained significant attention due to its adverse effects on human health, with studies indicating that about 6% of American women of child-bearing age have blood mercury levels that increase the risk of adverse effects on children they might bear.

To address this issue, the Environmental Protection Agency (EPA) in the United States has implemented regulations to control mercury emissions from coal-fired power plants. However, the effectiveness of these regulations has been contested, with critics arguing that power plants significantly contribute to mercury emissions in local hotspots and that reducing these emissions would considerably reduce risks. The EPA has promulgated "cap-and-trade" standards that rely on co-benefits from sulfur dioxide and nitrogen oxide controls, rather than stringent plant-specific requirements. This approach aims to minimize costs for electric utilities, but it has faced legal challenges from multiple states arguing for more stringent standards.

Mercury removal methods and technologies exist, such as activated carbon injection and the use of scrubbers and selective catalytic reduction. However, the energy industry, including power plants, remains the second-largest anthropogenic source of mercury pollution worldwide. The mitigation of mercury emissions is gaining attention, and further research is needed to quantify the impact of mercury emissions on the environment and human health.

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