U.S. Energy-Related Carbon Dioxide Emissions, 2018
Introduction
U.S. energy-related carbon dioxide (CO2) emissions increased in 2018. Weather was one driver of this increase: the winter months were colder and the summer months were warmer than in 2017. In addition, U.S. transportation-related emissions continue to rise with gross domestic product (GDP), which has been a trend since 2012.
This analysis examines economic trends and changes in fuel mix that influence energy-related CO2 emissions in the United States. As a result, most of the CO2 emissions being discussed are the result of fossil fuel combustion or their use in the petrochemical and related industries.
In the short term, energy-related CO2 emissions are influenced by factors such as weather, fuel prices, and disruptions in electricity generation.
In the long term, CO2 emissions are influenced by
Policies to encourage renewable energy
Reduced costs and improved efficiency of new technologies
Demand-side efficiency gains such as vehicle miles per gallon or appliance efficiencies
Economic trends such as the changing profile of U.S. manufacturing industries
Overview
U.S. energy-related CO2 emissions increased 2.7% (139 million metric tons) in 2018
Real U.S. gross domestic product (GDP) increased 2.9% in 2018, up 0.6% from growth in 2017.
Energy‐related CO2 emissions in the United States increased by 2.7% (139 million metric tons [MMmt]) from 5,130 MMmt in 2017 to 5,269 MMmt in 2018, but they were 730 MMmt (12%) lower than 2005 levels.
The overall carbon intensity (CO2/GDP) of the U.S. economy declined 0.1% in 2018 compared with a 2.9% decline in 2017. This 0.1% decline resulted from a 0.6% increase in energy intensity (British thermal units [Btu]/GDP) offset by a 0.8% decline in the carbon intensity (CO2/Btu) of the energy consumed. Increases in weather-related and transportation energy demand were factors in the energy intensity increase.
Source: U.S. Energy Information Administration, Monthly Energy Review, October 2019, Table 11.1, Carbon Dioxide Emissions from Energy Consumption by Source.
Note: Unless otherwise indicated, all data in this analysis refer to EIA’s October 2019 Monthly Energy Review. Non-energy uses that both emit and capture carbon are included under the term energy-related CO2 because fossil fuels are used primarily as energy inputs. CO2 refers to carbon dioxide.
In 2018, U.S. energy‐related CO2 emissions were 222 MMmt higher when compared with the average 2007–2017 trend
One way to disaggregate the factors that combine into total U.S. energy-related CO2 emissions is an equation known as the Kaya identity. The Kaya identity relates percentage changes in energy-related CO2 emissions to changes in four factors: energy intensity, per capita GDP, carbon intensity, and population.
U.S. CO2 emissions for 2018 appear to be 4.4%, or 222 MMmt higher than if components of the Kaya identity (shown in Figure 2) matched their previous decade (2007–2017) trend rates.
Largely due to weather and transportation demand in 2018, U.S. energy intensity increased by 0.6% compared with a 1.6% average decline in the previous decade, which led to 2018 U.S. CO2 emissions that were 117 MMmt higher than if the trend of the previous decade had continued.
As a result of relatively strong economic growth, U.S. GDP per capita grew by 2.2% from 2017 to 2018, compared with the previous decade’s average annual growth rate of 0.6%. Higher U.S. GDP per capita growth in 2018 put upward pressure on CO2 emissions, adding about 84 MMmt compared with what the previous decade’s average trend would have predicted.
In 2018, the carbon intensity of U.S. energy consumption declined by 0.8%, a lower rate than the previous decade’s average annual decline of 1.4%. As a result, 2018 U.S. CO2 emissions were 33 MMmt greater than what they would have been if the previous decade’s trend had continued.
Slower population growth of 0.6% in the United States, compared with the previous decade’s average of 0.8%, resulted in 12 MMmt lower 2018 CO2 emissions than would have been predicted with the previous decade’s trend.
Sources: U.S. Energy Information Administration, Monthly Energy Review, October 2019, Table 11.1, Carbon Dioxide Emissions from Energy Consumption by Source. U.S. Bureau of Economic Analysis, Current-Dollar and "real" Gross Domestic Product. U.S. Bureau of Census, U.S. Population 2017. See details on the Kaya Identity. See page 17 for the methodology of this analysis.
Note: GDP refers to gross domestic product, and CO2 refers to carbon dioxide.
Fuels
Weather conditions influenced the U.S. energy-related CO2 emissions increase in 2018
Energy‐related CO2 emissions in the United States increased by 2.7% (139 MMmt) from 5,130 MMmt in 2017 to 5,269 MMmt in 2018. From 2009 to 2018, total energy-related CO2 emissions declined by 2% (123 MMmt).
U.S. natural gas CO2 emissions increased every year from 2009 to 2016, declined 1.3% (20MMmt) in 2017, and then increased 10.2% (151 MMmt) in 2018. Because natural gas is the primary heating fuel in much of the country, the colder winter temperatures drove greater use of natural gas and a corresponding increase in CO2 in 2018. In addition, the natural gas share of U.S. electricity generation has been growing. The total generation-related natural gas CO2 emissions increased an average of 5.6% per year from 2009 to 2016. Economy-wide, natural gas CO2 emissions surpassed total emissions from coal in 2015. Between 2009 and 2018, natural gas emissions increased 32% (391 MMmt).
Figure 3 shows that U.S. CO2 emissions from coal declined by 33% (617 MMmt) in 2018 compared with 2009. The graph also shows CO2 emissions from petroleum and other liquids have increased by 5% (102 MMmt) in 2018 compared with 2009 levels.
Source: U.S. Energy Information Administration, Monthly Energy Review, October 2019, Table 11.1 Carbon Dioxide Emissions from Energy Consumption by Source.
Note: CO2 refers to carbon dioxide.
End Use Sectors
In 2018, CO2 emissions increased in all U.S. end-use sectors
Emissions from the residential and commercial sectors in the United States, defined collectively as the buildings sector, led the growth in emissions at 95 MMmt (5.2%). This growth was mostly the result of colder winter and warmer summer weather in 2018 compared with 2017. U.S. residential sector emissions are more influenced by weather, and they increased by 70 MMmt (7.4%) while commercial sector emissions rose 25 MMmt (2.8%).
Transportation-related CO2 emissions have been increasing steadily in the United States since 2012 because of a recovering economy and moderate fuel prices. Energy-related CO2 from the U.S. transportation sector increased by 28 MMmt (1.5%) and is now 8% higher than 2012 levels.
CO2 emissions from the U.S. industrial sector have been declining, but they increased by 16 MMmt (1.1%) in 2018 as a result of a growing economy.
Source: U.S. Energy Information Administration, Monthly Energy Review, October 2019, Table 11.2 Carbon Dioxide Emissions from Energy Consumption: Residential Sector; Table 11.3 Carbon Dioxide Emissions from Energy Consumption: Commercial Sector; Table 11.4 Carbon Dioxide Emissions from Energy Consumption: Industrial Sector; Table 11.5 Carbon Dioxide Emissions from Energy Consumption: Transportation Sector.
Note: CO2 refers to carbon dioxide.