| Greenhouse gas emissions in the US economy, 2008. Source: EIA. Click to enlarge. |
Total US greenhouse gas emissions in 2008 were 2.2% below the 2007 total, according to the just-released report by the US Energy Information Administration, Emissions of Greenhouse Gases in the United States 2008.
The decline in total emissions—from 7,209.8 million
metric tons carbon dioxide equivalent (MMTCO2e) in 2007 to 7,052.6 MMTCO2e in 2008—was largely the result of a 177.8-MMTCO2e drop in carbon dioxide emissions. There were small percentage increases in emissions of other greenhouse gases, but their absolute contributions to the change in total emissions were relatively small, with the increase in emissions of those gases being more than offset by the drop in CO2 emissions:
-
14.8 MMTCO2e growth for methane (CH4), or 2%. Methane emissions totaled 737.4 MMTCO2e in 2008. Most of the increase came from coal mining and from
natural gas production and processing. Emissions from petroleum systems decreased. Emissions from stationary combustion—primarily from wood combustion
for residential heating—increased. -
0.4 MMTCO2e growth for nitrous oxide (N2O), or 0.1%.
- 5.3 MMTCO2e growth for the man-made gases with high global warming
potentials (high-GWP gases). The increase resulted
mainly from higher emissions levels for hydrofluorocarbons
(HFCs, up by 5.0 MMTCO2e).
The decrease in US CO2 emissions in 2008 resulted
primarily from three factors, according to the EIA report: higher energy prices—
especially during the summer driving season—that led to a drop in petroleum consumption; economic contraction in three out of four quarters of the year that
resulted in lower energy demand for the year as a whole in all sectors except the commercial sector; and lower demand for electricity along with lower carbon
intensity of electricity supply.
Petroleum remained the largest fossil fuel source for energy-related CO2 emissions, contributing 42% of the total, followed by coal with a 37% contribution. Although coal produces more CO2 per unit of energy, petroleum consumption—in terms of
British thermal units (Btu)—made up 44.6% of total fossil fuel energy consumption in 2008, as compared with coal’s 26.8%.
The transportation sector has led all US end-use sectors in emissions of carbon dioxide since 1999; however, with higher fuel prices and slower economic growth in 2008, emissions from the transportation sector fell by 4.7% from their 2007 level. Transportation sector carbon dioxide emissions in 2008 were 95.6 MMT lower than in 2007 but still 343.2 MMT higher than in 1990.
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