A U.S. Energy Information Administration (EIA) analysis of the carbon intensity of energy use for the five major energy-consuming sectors in the U.S. reveals the transportation sector produced the most carbon dioxide (CO2) per unit of primary energy consumed in 2016. Emissions approached 70 kilograms CO2 per million British thermal units (kg CO2/MMBtu).
The industrial sector produced the least, with emissions of 44 kg CO2/MMBtu. The relatively low carbon intensity for this segment of the economy is the result of several factors. The pulp and paper industry, which accounts for approximately 7% of total delivered industrial energy consumption, is a large consumer of biogenic material. EIA’s calculation of carbon intensities uses the convention that emissions from biomass combustion do not count as net energy-related CO2 emissions because biogenic fuels are produced as part of a natural cycle that absorbs carbon dioxide from the atmosphere during the growth phase. The same consideration applies to the use of biogenic fuels in other sectors, such as wood heating in the residential sector and ethanol consumption in the transportation sector.
About 15% of the industrial sector’s fossil fuel use captures some carbon in the form of plastics and other non-energy products. This carbon is not included in the emissions total for the sector since it is not emitted into the atmosphere in the form of CO2.
The electric power sector, previously one of the more carbon-intensive sectors, produced 48 kg CO2/MMBtu in 2016 after averaging near 60 kg CO2/MMBtu for decades. This intensity is slightly lower than that of natural gas, which produces 53 kg CO2/MMBtu, indicating that the combustion-weighted average of all fuels used to produce electricity in the United States (coal, natural gas, petroleum, nuclear, renewables) is now lower than the carbon intensity of natural gas. The carbon intensity decline is attributed to a shift away from coal-fired electricity generation toward less-carbon-intensive natural gas and carbon-free renewable energy forms, such as wind and solar.
After averaging near 60 kg CO2/MMBtu for decades, the electric power sector’s carbon intensity fell to 48 kg CO2/MMBtu in 2016. This intensity is slightly lower than that of natural gas, which produces 53 kg CO2/MMBtu. In other words, the combustion-weighted average of all fuels used to produce electricity in the United States (coal, natural gas, petroleum, nuclear, renewables) is now lower than the carbon intensity of natural gas.
In previous years, including the indirect emissions associated with electricity production tended to increase a sector’s carbon intensity. However, as the electric power sector’s carbon intensity declined, this was no longer the case for the commercial sector starting in 2012 or for the residential sector starting in 2015. Only in the industrial sector is it still the case that including indirect emissions from the electric power sector raises the carbon intensity of overall energy use.