Total U.S. greenhouse gas emissions in the United States dropped by 5.8 percent from 2008 to 2009—the largest decline since data collecting began in 1990, according to Emissions of Greenhouse Gases in the United States 2009, a report released today by the U.S. Energy Information Administration (EIA). Since 1990, U.S. GHG emissions have grown at an average annual rate of 0.4 percent.
The decrease in U.S. CO2 emissions in 2009 resulted primarily from three factors: an economy in recession, a particularly hard-hit energy-intensive industries sector and a large drop in natural gas prices that fueled a switch from coal to natural gas in the electric power sector. "The large decline in emissions in 2009 was driven by the economic downturn, combined with an ongoing trend toward a less energy-intensive economy and a decrease in the carbon-intensity of the energy supply," said EIA Administrator Richard Newell.
After rising at an average annual rate of 0.8 percent per year from 1990 to 2008, emissions of energy-related carbon dioxide decreased by 7.1 percent in 2009. A 2.6 percent decline in Gross Domestic Product (GDP) contributed to the decrease. The energy intensity of the U.S. economy, measured as energy consumed per dollar of GDP (Energy/GDP), fell by 2.2 percent in 2009. Carbon dioxide intensity of U.S. energy supply (CO2 per unit of energy) also fell in 2009, caused primarily by an increase in electricity generated by natural gas.
Methane emissions increased by 0.9 percent, while nitrous oxide emissions fell by 1.7 percent in 2009. Based on partial data constituting about 77 percent of the category, combined emissions of HFCs, PFCs and SF6 increased by 4.9 percent.
Energy-related CO2 emissions dominate total U.S. greenhouse gas emissions. Coal is the second-largest fossil fuel contributor, at 35 percent. Although coal produces more CO2 per unit of energy produced than petroleum does, petroleum consumption—in terms of British thermal units (Btu)—made up 45.0 percent of total fossil fuel energy consumption in 2009, as compared with coal's 25 percent. Natural gas, with a carbon intensity that is about 55 percent higher than coal and 75 percent of the carbon intensity of petroleum, accounted for 30 percent of U.S. fossil energy use in 2009 but only 22 percent of total energy-related CO2 emissions.