Cleanest-Burning Fuels: Reducing Pollution With The Right Choice

Fossil fuels have been the primary source of energy for over a century, powering our cars, businesses, and homes. However, burning fossil fuels like oil, coal, and natural gas has severe environmental and health consequences. With growing awareness of the impact of fossil fuels on climate change and air pollution, there is an urgent need to identify cleaner and more sustainable alternatives. This discussion aims to explore different types of fuels and their pollution levels when burned, seeking to answer the critical question: Which fuel will cause the least pollution when it burns?

Natural gas has lower CO2 emissions relative to its energy content

Natural gas is primarily methane ($CH_4$) with some other impurities. It is the simplest form of hydrocarbon and the cleanest-burning fossil fuel. The amount of CO2 produced when a fuel is burned depends on its carbon content. Natural gas has a higher energy content compared to other fuels, and thus, it has lower CO2 emissions relative to its energy content.

The U.S. Environmental Protection Agency estimates that in 2021, methane emissions from natural gas and petroleum systems and from abandoned oil and natural gas wells were the source of about 33% of total U.S. methane emissions and about 4% of total U.S. greenhouse gas emissions. However, natural gas production and use have some environmental and safety considerations. For example, some natural gas leaks into the atmosphere from oil and natural gas wells, storage tanks, pipelines, and processing plants.

Burning natural gas for energy results in fewer emissions of nearly all types of air pollutants and carbon dioxide (CO2) emissions than burning coal or petroleum products to produce an equal amount of energy. For every 1 million Btu consumed (burned), more than 200 pounds of CO2 are produced from coal and more than 160 pounds of CO2 are produced from fuel oil, while only about 117 pounds of CO2 are produced from natural gas. This has contributed to increased natural gas use for electricity generation and for fleet vehicle fuel in the United States.

Over the past 15 years, the U.S. electricity generation mix has shifted away from coal and toward natural gas and renewables, resulting in lower CO2 emissions from electricity generation. In 2019, the U.S. electric power sector produced 1,724 million metric tons (MMmt) of CO2, 32% less than in 2005. This decrease in CO2 emissions is largely due to the shift from coal to natural gas in the electricity generation mix. In 2005, coal accounted for 50% of U.S. electricity generation, but this share declined to 23% in 2019. On the other hand, natural gas usage increased from 19% of total generation in 2005 to 38% in 2019.

Burning fossil fuels releases harmful nitrogen oxides

Natural gas is the cleanest-burning fossil fuel and the simplest form of hydrocarbon. It is mostly methane with some other impurities. The combustion of other fossil fuels, such as coal, oil, and diesel, releases harmful nitrogen oxides, among other pollutants.

Nitrogen oxides are a group of harmful gases composed of nitrogen and oxygen. They are formed when fossil fuels are burned at high temperatures. Nitrogen dioxide (NO2), a type of nitrogen oxide, is emitted when fossil fuels such as coal, oil, gas, diesel, and methane gas (natural gas) are burned. NO2 is a significant air pollutant and is one of six widespread air pollutants with national air quality standards limiting their levels in outdoor air.

NO2 and other nitrogen oxides contribute to particle pollution and the chemical reactions that create ozone. They also increase the reflectivity of the atmosphere, which has a slight cooling effect. However, the net effect of burning fossil fuels is warming due to the greenhouse effect caused by greenhouse gases. These gases, including carbon dioxide (CO2) and nitrous oxide (N2O), remain in the atmosphere for decades to centuries, intensifying the greenhouse effect and increasing the Earth's average air temperature.

Nitrogen oxides have harmful effects on the lungs and are strongly linked to respiratory illnesses. Scientific evidence suggests that exposure to NO2 may cause asthma in children. Poor air quality caused by nitrogen oxides and other pollutants can lead to emergency department and hospital admissions, particularly for individuals with pre-existing medical conditions and vulnerable subpopulations such as people of color.

To reduce air pollution from nitrogen oxides, it is essential to transition to cleaner energy sources and reduce the burning of fossil fuels. This can be achieved by embracing renewable and sustainable alternatives, such as wind, solar, and hydroelectric power, and improving energy efficiency. Additionally, consolidating driving trips, carpooling, using public transportation, and opting for walking or biking can help minimize nitrogen oxide emissions from vehicles.

Fossil fuel combustion is a leading cause of environmental injustice

Natural gas is the cleanest-burning fossil fuel and the simplest hydrocarbon, with a chemical formula of CH4. However, it is important to note that all fossil fuels, including natural gas, contribute to pollution and climate change when burned.

Fossil fuel combustion is a significant contributor to environmental injustice, particularly impacting the health and future of children. The emissions from burning fossil fuels include toxic air pollutants and carbon dioxide (CO2), which is the most important human-produced climate-altering greenhouse gas. The effects of air pollution and climate change synergize, magnifying the harm to children. Impacts can include impairment of cognitive and behavioral development, respiratory illness, and other chronic diseases, which may be ""seeded" in utero and affect health and functioning throughout life. Fossil fuel combustion disproportionately affects developing fetuses and young children due to their immature defense mechanisms and rapid development. This vulnerability is further exacerbated in low- and middle-income countries, where poverty and lack of resources compound the effects.

Even in high-income countries, low-income communities and communities of color are experiencing the impacts of fossil fuel-related pollution, climate change, and resultant widening inequality and environmental injustice. Fossil fuel combustion contributes to global inequality and environmental injustice by impairing children's health, ability to learn, and potential to contribute to society. This leads to reduced resilience in children and decreased equity in the communities they live in. The World Health Organization (WHO) estimates that children under 5 bear more than 40% of the burden of environmentally related diseases and over 88% of the burden of climate change, despite constituting only 10% of the global population.

The combustion of fossil fuels for electricity production, heating, transportation, and industry is the primary source of air pollution globally. In 2011, fossil fuels represented 82% of total primary energy supply worldwide. The mounting health and economic costs of pollution and climate change from fossil fuel combustion are spurring mitigation efforts and interventions to reduce and prevent further harm. These efforts provide hope for the future, but strong and immediate action is needed to protect future generations from inheriting an unsustainable and unfair world.

Fossil fuels emit toxic air pollutants long before they're burned

Natural gas is the cleanest-burning fossil fuel and the simplest hydrocarbon. It is primarily methane with a few other impurities. It has a higher energy content compared to other fuels and thus has lower carbon dioxide emissions relative to its energy content. However, it is important to note that all combustion of fossil fuels leads to some amount of pollution, and the amount of pollution is intensified by the number of impurities constituting the fuel.

Fossil fuels emit toxic air pollutants long before they are burned. According to a 2017 study, 17.6 million Americans are exposed daily to toxic air pollution from active oil and gas wells, as well as transport and processing facilities. These include benzene, which is linked to childhood leukaemia and blood disorders, and formaldehyde, a cancer-causing chemical. The fracking industry, which involves blasting huge quantities of water mixed with chemicals and sand into wells to extract oil or gas, creates air and water pollution and contaminates drinking water. Mining operations, especially for miners, generate toxic airborne particulate matter and can release giant carbon stores held naturally in the wild. Coal mining washes toxic runoff into streams, rivers, and lakes, and oil spills and leaks during extraction or transport can jeopardize entire freshwater or ocean ecosystems. All drilling, fracking, and mining operations generate enormous volumes of wastewater, which can be laden with heavy metals, radioactive materials, and other pollutants that leak into waterways and contaminate drinking water sources.

Coal is the most carbon-intensive fossil fuel

Natural gas is often considered the cleanest-burning fossil fuel. It is composed mostly of methane with some other impurities, and its chemical formula is CH4. As a result, it has a higher energy content compared to other fuels and lower CO2 emissions relative to its energy content.

On the other hand, coal is the most carbon-intensive fossil fuel. It is a carbon-heavy rock that comes in four main varieties: lignite, sub-bituminous, bituminous, and anthracite. Coal is extracted through underground mining or surface mining (strip mining). The latter removes entire layers of soil and rock to access coal deposits and accounts for about two-thirds of coal sourced in the United States. Nearly all of the coal burned in the United States is sub-bituminous or bituminous, which are middle-of-the-road in terms of carbon content and heat energy produced.

Coal-fired power plants are responsible for a significant portion of harmful emissions. In the United States, they generate 35% of mercury emissions, two-thirds of sulfur dioxide emissions, and most soot in the air. Additionally, the combustion of coal produces sulphur compounds and other impurities, making it a significant contributor to air pollution.

The high carbon content of coal contributes to global warming and ocean acidification. When we burn coal, we don't just meet our energy needs; we also accelerate the current global warming crisis. The ocean has become 30% more acidic since the Industrial Revolution, largely due to coal-burning practices.

Recognizing the environmental impact of coal, several countries have taken steps toward a coal phase-out. Portugal, Belgium, Austria, and Sweden have closed their last remaining coal plants. China has begun operating the Taizhou coal-fired power plant with carbon capture technology, and Germany has advanced its coal phase-out date from 2038 to 2030.

To align with the Paris Agreement and limit global temperature increase to 1.5°C, a transition to renewable energy sources is crucial. All coal-fired power stations must be shut down by 2040 at the latest.

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