U.S. Greenhouse Gas Emissions Lower in 2008

WASHINGTON, DC, March 10, 2010 (ENS) – U.S. greenhouse gas emissions fell 2.9 percent from 2008 to 2009, the largest one-year drop on record since government recordkeeping began in 1990, according to the annual Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2008 draft report released Tuesday.

Greenhouse gases contribute to climate warming by forming a blanket in the Earth’s upper atmosphere that keeps the Sun’s heat trapped close to the planet instead of radiating back out into space.

The inventory tracks annual greenhouse gas emissions from 1990 to 2008 at the national level. The six gases covered by this inventory include carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride.

Lower fuel and electricity consumption is responsible for the downward trend in carbon dioxide emissions, according to the analysis produced by the U.S. Environmental Protection Agency in collaboration with experts from other federal agencies.

Electricity demand declined in 2008 in part “due to a significant increase in the cost of fuels used to generate electricity,” the report notes.

In 2008, temperatures were cooler in the United States than in 2007, both in the summer and the winter. This led to an increase in heating related energy demand in the winter, however, much of this increase was offset by a decrease in cooling related electricity demand in the summer, the report says.

Duke Energy’s Zimmer power plant on the Ohio River is the largest single-unit fossil fuel generating unit in the United States. (Photo courtesy Power)

But while greenhouse gas emissions dropped in 2008, overall, emissions have grown by 13.6 percent from 1990 to 2008.

The primary greenhouse gas emitted by human activities in the United States was carbon dioxide, CO2, representing approximately 85.0 percent of total greenhouse gas emissions. The largest source of CO2, and of overall greenhouse gas emissions, was fossil fuel combustion – the burning of coal, oil and gas to generate electricity and power motor vehicles.

Emissions of methane, which have declined by 7.5 percent since 1990, resulted primarily from enteric fermentation associated with domestic livestock, decomposition of wastes in landfills, and natural gas systems. Agricultural soil management and mobile source fuel combustion were the major sources of nitrous oxide emissions.

Ozone depleting substance substitute emissions and emissions of HFC-23 during the production of HCFC-22 were the primary contributors to aggregate hydrofluorocarbons emissions.

perfluorocarbon emissions resulted as a by-product of primary aluminum production and from semiconductor manufacturing, while electrical transmission and distribution systems accounted for most sulfur hexafluoride emissions.

The inventory also calculates carbon dioxide emissions that are removed from the atmosphere by sinks, such as through the uptake of carbon dioxide by forests, vegetation, and soils.

After responding to public comments, the U.S. government will submit the final inventory report to the Secretariat of the United Nations Framework Convention on Climate Change, UNFCCC. The report will fulfill the annual requirement of the UNFCCC international treaty, ratified by the United States in 1992, which sets an overall framework for intergovernmental efforts to tackle the challenge posed by climate change.

For the future, projected improvements in the economy contribute to an expected 1.5 percent increase in CO2 emissions in 2010, the U.S. Energy Information Administration projects.

Increased use of coal in the electric power sector and continued economic growth, combined with the expansion of transportation-related petroleum consumption, lead to a 1.2 percent increase in CO2 emissions in 2011.

However, even with increases in 2010 and 2011, projected CO2 emissions in 2011 are lower than annual emissions from 1999 through 2008, according to the Energy Information Administration, an agency of the U.S. Department of Energy.

Click here for more information on the 2010 Draft U.S. Greenhouse Gas Inventory Report and how to submit public comments. This report will be open for public comment for 30 days after the Federal Register notice is published.

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