Fossil fuel emissions

With the exception of CO2, the effluents of fossil fuel combustion devices such as automobile engines and thermoelectric power plants do not seem to have a direct effect on climate change. These pollutants are important, however, because of their deleterious effects upon the environment and human health.

Background

Fossil fuels are combustible geologic deposits of carbon created from plant and animal remains subjected to high temperatures and pressures in the Earth over hundreds of millions of years. Coal, oil, and natural gas are the primary fossil fuels. When any carbon-based fuel is burned, the carbon unites with oxygen in the atmosphere to produce carbon dioxide (CO₂), the main culprit responsible for global warming. In addition, sulfur dioxide, nitrogen oxides, ozone, and are often by-products of fossil fuel combustion. These pollutants detrimentally affect plants, aquatic life, and human respiratory health.

Consumption Modes

In the contemporary United States, 86 percent of all energy consumed is derived from fossil fuels, primarily oil (39 percent), natural gas (24 percent), and coal (23 percent). Some 8 percent comes from nuclear power, with the remaining 6 percent equally divided between wood and hydroelectric plants.

The energy consumed by each U.S. economic sector is as follows: residential and commercial, 35 percent; industry, 23 percent; direct transportation, 27 percent; and transportation-related uses, such as highways and other infrastructure construction, 15 percent. Some 69 percent of the petroleum consumed is for transportation, with another 9 percent for transportation-related uses. Industry accounts for 16 percent of U.S. petroleum consumption, while the residential and commercial sectors account for only 6 percent. Of the 9 percent used for transportation, automobiles consume 40 percent, trucks 33 percent, railroads and buses 3 percent, aircaft 9 percent, water craft 6 percent, and all others 9 percent.

Environmental Impacts

Fossil fuels provide energy when carbon, the backbone of all fossil fuels, unites with oxygen in the air to produce that energy, as well as CO₂—a combustion by-product. Other elements occurring with fossil fuels, most notably sulfur, are also combusted, releasing emissions toxic to plants and animals. Nonnegligible environmental impacts also result from the extraction, processing, transportation, and waste disposal involved with fossil fuels. The two most important ecological impacts of combusting are the effects on climate of CO₂ emissions and the effects on health of particulate matter and the gaseous by-products of combustion.

Coal mining is accomplished through either strip mining or deep mining. Strip mining renders scores of hectares of land unusable unless they are later reclaimed and has led to mudslides when the removed overburdens are piled too high. Deep mining is prone to cave-ins and fires, and virtually all career deep miners eventually succumb to pneumoconiosis (black lung disease). Abandoned mines often leach acidic effluents into local streams, decimating the local ecology and ruining scenic vistas.

Drilling for oil leads to environmental degradation at the drill site, but even more problematic are the minor leaks and major oil spills that occur during transportation of the oil. These accidents have contaminated shorelines and estuaries, fouling beaches and killing waterfowl and aquatic life. Natural gas is prone to drilling accidents as well and is also subject to pipeline leaks during gas transportation.

Public Health Impacts

All fossil fuels emit CO₂, which is a greenhouse gas but not a direct health hazard. In addition, coal typically contains from 1 to 10 percent sulfur and many other trace elements, some of which are radioactive. When sulfur is burned with the coal, it produces sulfur dioxide, which converts to sulfuric acid in the atmosphere. Rain containing the dissolved acid (known as acid rain) will adversely affect forests, and when the acid contaminates bodies of water, fish and aquatic plants are likely to die.

Whenever a carbon-containing fuel is burned, nitrogen oxides are also created; these chemicals react with atmospheric water vapor to create nitric acid, another component of acid rain. In addition, atmospheric nitrogen oxides, as well as sulfur oxides, raise mortality rates and morbidity, particularly among those with respiratory problems. Another gaseous pollutant associated with combusting fossil fuels is ozone, a highly reactive form of oxygen, formed when nitrogen oxides combine with in automotive exhaust. Ozone, in addition to increasing morbidity in those with respiratory problems, detrimentally affects forests and reduces crop yields.

Particulate matter released when fossil fuels are burned causes respiratory illness when particles between 0.2 and 3 microns in size coat the lining deep inside the lungs. For those already burdened by respiratory ailments, increased morbidity is a likely result.

Context

In the past 150 years, the U.S. population has increased by a factor of ten, and the per capita consumption of energy has increased by a factor of five. The United States is thus consuming fifty times the energy it consumed in 1860. Over this time period, the use of wood for fuel has remained relatively constant at about 3 exojoules annually. Water was not harnessed for energy until about 1906, when Niagara Falls became the site of the first plant. After World War II, the available energy from new hydroelectric plants increased to about 3 exojoules, where it has remained.

The use of coal began around 1840 and grew exponentially until 1920, when it reached 15 exojoules per year. Although the rate of increase has slowed, total annual coal use continues to increase; it is about 22 exojoules today. The use of oil, relatively minimal in the nineteenth century, reached 2 exojoules by 1900. With the twentieth century increase in automobiles, annual oil use rapidly increased to 15 exojoules in 1950, 35 exojoules in 1980, and 40 exojoules at the end of the century. Natural gas was used for lighting in the late nineteenth century at an annual rate of about 1 exojoule. As gas was increasingly used for heating, this rate increased to 5 exojoules by 1940 and 17 exojoules by 1960; it leveled off at 35 exojoules per year from 1980 through 2000.

Fossil fuel emissions continued to rise throughout the 2010s and 2020s. By 2023, emissions had reached a record 37.4 billion tonnes (GT). These have been proven to be a significant driver of global climate change. Scientists hope that clean energy programs and the adoption of electric vehicles will reduce these numbers over the coming decades.

Key Concepts

• exo: a prefix indicating 10¹⁸
• fossil fuel: any combustible deposit of carbon of biological origin created over millions of years of geologic history
• ozone: a very reactive form of oxygen consisting of three oxygen atoms bound together loosely
• particulate matter: small particles, such as fly ash and soot, emitted during the combustion of a carbon-based fuel

Bibliography

"As Pollution Increases, World Falls Further Behind Climate Targets." NOAA, 13 Nov., 2024, research.noaa.gov/no-sign-of-fossil-fuel-pollution-peak-as-the-world-falls-further-behind-climate-targets/#:~:text=Emissions%20of%20carbon%20caused%20by,for%20steep%20and%20immediate%20decreases. Accessed 11 Dec. 2024.

Bent, R., L. Orr, and R. Baker, eds. Energy: Science, Policy, and the Pursuit of Sustainability. Washington, D.C.: Island Press, 2002.

Freese, Barbara. Coal: A Human History. New York: Penguin, 2004.

Hyne, Norman J. Nontechnical Guide to Petroleum Geology, Exploration, Drilling, and Production. 2d ed. Tulsa, Okla.: Pennwell, 2001.