Coal Burning: Primary Pollutants And Their Impact

The combustion of coal is a significant source of air pollution worldwide, releasing a variety of toxic pollutants that are harmful to both human health and the environment. These pollutants are primarily released directly into the environment from their sources, and they can lead to health issues, environmental damage, and contribute to global warming and climate change. So, what are the primary pollutants that come from burning coal, and what effects do they have?

Carbon Monoxide

The combustion of coal, particularly in power plants, is a major source of carbon monoxide emissions. In 2014, US coal power plants emitted approximately 576,185 tons of carbon monoxide, contributing to air pollution and endangering public health. To address this issue, pollution control measures have been implemented, but many plants still lack adequate controls to mitigate carbon monoxide emissions effectively.

Additionally, the burning of charcoal, often used as cooking fuel, generates significant amounts of carbon monoxide. This has led to poisoning incidents, especially in enclosed areas with insufficient ventilation. To prevent carbon monoxide poisoning, it is crucial to avoid burning charcoal or coal indoors or in poorly ventilated spaces.

To mitigate the environmental and health impacts of carbon monoxide from coal combustion, various measures have been implemented. These include the development of carbon capture and storage technologies, which aim to capture CO2 emissions and store them underground. While these technologies show promise, they are still expensive and face challenges in scaling up to address the issue comprehensively.

Nitrogen Oxide

There are two major types of nitrogen oxides: NO and NO2. The combustion of coal produces both thermal and fuel nitrogen oxides. Thermal NOx is produced when atmospheric nitrogen and oxygen recombine under high temperatures to form NO. Fuel NOx is produced when coal and oil are burned to generate electricity.

To reduce nitrogen oxide emissions, a Low NOx burner can be used during combustion. This burner uses staged combustion to burn fuel at the right air-fuel ratio, reducing the amount of nitrogen oxide released. After combustion, selective catalytic reduction or selective non-catalytic reduction processes can further reduce nitrogen oxide emissions. Catalytic reduction involves injecting ammonia into a reactor through which flue gas flows, resulting in the formation of nitrogen and water vapour. Non-catalytic reduction is a similar process that occurs at a higher temperature and uses urea instead of ammonia.

Sulfur Dioxide

Coal-fired power plants are the largest human-caused source of sulfur dioxide emissions. In 2010, experts stated that they believed sulfur dioxide pollution from coal-fired power plants was slowly killing vegetation across Texas, specifically in Central Texas, near a power plant operated by the Lower Colorado River Authority. The deaths of pecan trees, oaks, elms, and willows have been documented, and pecan growers in the area believe the plant's sulfur dioxide emissions are to blame.

The main health effect of sulfur dioxide is the impairment of the upper respiratory system. High concentrations of sulfur dioxide can affect breathing, cause respiratory illnesses, and aggravate existing heart and lung diseases. Sulfur dioxide also contributes to acid rain, which causes environmental damage.

To reduce sulfur dioxide emissions, power plants use flue gas desulfurization equipment, also known as scrubbers, to clean sulfur from the smoke before it exits their smokestacks. The coal industry and the U.S. government have also cooperated to develop technologies that can remove impurities from coal and make coal more energy-efficient, reducing the amount of coal burned per unit of useful energy produced. Additionally, the EPA has implemented rules to reduce emissions of sulfur dioxide and pollutants that form sulfur oxides, helping state and local governments meet national air quality standards.

Particulate Matter

In 2014, US coal power plants emitted 197,286 tons of small airborne particles, measured as 10 micrometers or less in diameter. Particulate matter can irritate the small airways in the lungs, leading to increased problems with asthma, chronic bronchitis, airway obstruction, and gas exchange. Studies have also found a correlation between coal-related particulate matter and an increased risk of stroke.

In 2011, the American Lung Association released a report titled "Toxic Air: The Case for Cleaning Up Coal-fired Power Plants," which highlighted that coal-fired power plants produce more hazardous air pollution in the United States than any other industrial pollution source. The report estimated that particulate matter pollution from power plants kills approximately 13,000 people annually.

To address the issue of particulate matter from coal-fired power plants, electrostatic precipitators or baghouses are used to remove particulates and heavy metals from the smoke. Additionally, scrubbers, or flue gas desulfurization equipment, are employed to clean the smoke before it exits the smokestacks. While these technologies have helped reduce particulate matter emissions, the urgency to transition to cleaner energy sources remains to further mitigate the health risks associated with coal-fired power plants.

Mercury

The dangers of mercury pollution from coal-fired power plants have been recognised, and efforts have been made to reduce emissions. The U.S. Environmental Protection Agency (EPA) implemented the Mercury and Air Toxics Standards in 2012, which significantly reduced mercury pollution. However, the enforcement of these standards has been inconsistent, and many power plants continue to emit dangerous levels of mercury.

To address this issue, the Biden administration is working to revive mercury limits for coal-fired power plants. Additionally, scientists are researching methods to reduce mercury emissions, such as carbon capture, selective mining, coal washing, and post-combustion removal of mercury from stack emissions.

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