Oil
Crude oil, or petroleum (literally “rock oil” in Latin), is a liquid fossil fuel made up mostly of hydrocarbons (hydrogen and carbon compounds). Oil can be found in underground reservoirs; in the cracks, crevices, and pores of sedimentary rock; or in tar sands near the earth’s surface. It’s accessed by drilling, on land or at sea, or by strip mining in the case of tar sands oil and oil shale. Once extracted, oil is transported to refineries via supertanker, train, truck, or pipeline to be transformed into usable fuels such as gasoline, propane, kerosene, and jet fuel—as well as products such as plastics and paint.
According to the EIA, petroleum products supply about 35 percent of U.S. energy needs, with the transportation sector consuming the most. U.S. oil consumption in 2016 was 10 percent below the record high of 2005 and only 3 percent higher than during the 1973-74 embargo by the Organization of the Petroleum Exporting Countries (OPEC)—despite the U.S. economy tripling in size in the decades since. Demand for oil plummeted during the first two years of the COVID-19 pandemic, but it has now risen to its highest point since 2019. This is partly due to the volatile global market amid Russia’s invasion of Ukraine. Still, U.S. consumption of petroleum products is forecast to decrease, at least through 2038, as fuel efficiency standards lead to cleaner-running vehicles. Continued strengthening of clean car and fuel economy standards remains critical for reducing oil consumption.
On the production side, the United States has experienced a decade-long upswing. Production growth is due in large part to advancements in horizontal drilling and hydraulic fracturing, technologies that have created a boom in U.S. shale oil and natural gas extraction. While horizontal drilling enables producers to drill down and outward—thus reaching more oil or gas from a single well—hydraulic fracturing (also known as fracking) is designed to extract oil or natural gas from unyielding rock, including shale and other formations. Fracking involves blasting huge quantities of water mixed with chemicals and sand deep into a well, at pressures high enough to fracture rock and enable the oil or gas to escape. This controversial method of extraction creates a host of environmental and health problems, including air and water pollution.
Coal
Coal is a solid, carbon-heavy rock that comes in four main varieties, differentiated largely by carbon content: lignite, sub-bituminous, bituminous, and anthracite. Nearly all of the coal burned in the United States is sub-bituminous or bituminous. Found in abundance in states, including Kentucky, Pennsylvania, West Virginia, and Wyoming, these coal types are middle of the pack in terms of carbon content and the heat energy they can produce. Regardless of variety, however, all coal is dirty. Indeed, in terms of emissions, it’s the most carbon-intensive fossil fuel we can burn.
Coal is extracted via two methods: Underground mining uses heavy machinery to cut coal from deep underground deposits, while surface mining (also known as strip mining) removes entire layers of soil and rock to access coal deposits below. Strip mining accounts for about two-thirds of coal sourced in the United States. Although both forms of mining are detrimental to the environment, strip mining is particularly destructive, uprooting and polluting entire ecosystems.
Coal and the power plants that burn it account for less than a third of U.S. electricity generation, down from more than half in 2008. Cleaner, cheaper alternatives—including natural gas, renewables like solar and wind, and energy-efficient technologies—make coal far less economically attractive and demand for coal has fallen steadily since 2014. Today, coal-fired power plants continue to close, despite the former Trump administration’s promises of a revived industry. At the moment, market fluctuations amid the war in Ukraine have resulted in a sudden uptick in coal consumption, especially in its competition with fracked (natural) gas, but that is expected to be temporary as market forces propel alternative energy sources forward.
Fracked (natural) gas
Composed mostly of methane, fracked gas is generally considered either conventional or unconventional, depending on where it’s found underground. Conventional gas is located in porous and permeable rock beds or mixed into oil reservoirs and can be accessed via standard drilling. Unconventional gas is essentially any form of gas that is too difficult or expensive to extract via regular drilling, requiring a special stimulation technique, such as fracking.
In the United States, the development and refinement of processes like fracking have helped make the country the world’s top producer of gas since 2009—and the biggest consumer of it too. Abundant in the United States, gas produces 38 percent of U.S. energy needs and is the largest source of energy for electricity. Forecasts suggest it will become an even greater part of the U.S. energy mix, threatening to exacerbate air and water pollution.