The U.S. has a diverse and proven supply of several types of fossil fuels that can be used to power the national grid. Coal, natural gas, and petroleum all have been used to power American homes, heat and cool buildings, and power vehicles for over a century. Since the Industrial Revolution, fossil fuels have been the primary fuels that have powered American industries and allowed for the development of multiple types of products and technologies. Fossil fuels have benefits and drawbacks to their utilization. While fossil fuel energy density makes them highly efficient, each of them comes with a set of drawbacks.

Coal, natural gas, and petroleum are all formed by decomposing biomass from plant and animal matter that has been heated and compressed for expanses of time underground. Coal is a sedimentary rock that is made up of these ancient plant debris and animal remains. Because it is primarily made up of carbon, coal emits large amounts of greenhouse gasses (GHGs), primarily carbon and nitrous oxide. Coal is extremely energy dense, with even the lowest-quality coal able to generate 2.5 kWh of electricity per pound. Reserves of coal in the U.S. stand at 946 trillion pounds, but coal’s emissions have made cleaner-burning fossil fuels like natural gas more appealing.

Natural gas is made up of primarily methane but contains traces of carbon dioxide. Like coal, it is extremely energy dense and natural gas generated 40 percent of electricity in the U.S. in 2020. Natural gas can be extracted from deposits inside sedimentary rock or between rock layers and the U.S. contains about 84 years worth of proven and unproven natural gas. Methane sources from other industries like agriculture can also provide another source of natural gas for more localized energy needs. Natural gas is the cleanest burning fossil fuel, producing barely under a pound of carbon dioxide emissions per kilowatt hour of energy. Innovations in natural gas extraction alongside shale oil extraction have allowed more natural gas and oil to be utilized for energy production.

Petroleum denotes any fuels produced from crude oil or hydrocarbons contained in natural gas. Gasoline is the most commonly recognized petroleum product and it is used to power most vehicles in the U.S. as well as generate power for certain industrial processes. Petroleum is one of the most energy-dense fuels, with a single gallon being able to generate 40 kWh of energy. While petroleum makes up less than one percent of U.S. electricity generation, petroleum’s ability to generate heat at a rate of almost 13 kWh per gallon makes it a reliable source of fuel to heat homes. Due to petroleum’s widespread utilization, emissions from petroleum make up a majority of U.S. and worldwide emissions.

Fossil fuels’ economical energy density and ease of transportation have made them staples of the U.S. energy mix for over a century. However, the large amounts of emissions generated from fossil fuels have allowed for less carbon-intensive energy sources to receive investments. Fossil fuels still have a role to play in fulfilling U.S. energy needs. Innovative technologies like coal scrubbers have allowed coal plants today to pollute much less than in previous iterations. Continuing to make fossil fuels cleaner will ensure they are still able to be a part of the U.S. energy mix.


Written by Roy Mathews, Former Public Policy Associate


The Alliance for Innovation and Infrastructure (Aii) is an independent, national research and educational organization. An innovative think tank, Aii explores the intersection of economics, law, and public policy in the areas of climate, damage prevention, energy, infrastructure, innovation, technology, and transportation.