Different fuels emit different amounts of carbon dioxide (CO2) in relation to the energy they produce when burned. To analyze emissions across fuels, compare the amount of CO2 emitted per unit of energy output or heat content. The U.S. Energy Information Administration publishes emissions coefficients for CO2 by type of fuel per unit of volume or mass and per million British thermal units.
The amount of CO2 produced when a fuel is burned is a function of the carbon content of the fuel. The heat content, or the amount of energy produced when a fuel is burned, is mainly determined by the carbon (C) and hydrogen (H) content of the fuel. Heat is produced when C and H combine with oxygen (O) during combustion. Natural gas is primarily methane (CH4), which has a higher energy content compared to other fuels, and thus, it has lower CO2 emissions relative to its energy content. Water and various elements in some fuels, such as sulfur and noncombustible elements, reduce the fuels' heating values and increase CO2 emissions per unit of heat content.
Last updated: June 13, 2023