U.S. GHG Emissions Drop 4.7 Percent in Transportation Sector in 2008, EIA Reports

U.S. GHG Emissions Drop 4.7 Percent in Transportation Sector in 2008, EIA Reports

By Scott Doggett December 4, 2009

Total U.S. greenhouse-gas emissions in 2008 were 2.2 percent below the 2007 total and 4.7 percent lower for the transportation sector over the same period, according to a just-released report by the U.S. 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, or 2 percent. 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, or 0.1 percent.
• 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 U.S. 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 percent of the total, followed by coal with a 37 percent contribution.

Although coal produces more CO2 per unit of energy, petroleum consumption -- in terms of British thermal units -- made up 44.6 percent of total fossil fuel energy consumption in 2008, as compared with coal's 26.8 percent.

The transportation sector has led all U.S. 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 percent 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.

Scott Doggett:  is an AutoObserver.com Associate Editor.