In April 2012, the U.S. Environmental Protection Agency (EPA) released its 17th annual U.S. greenhouse gas (GHG) emissions inventory, The Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2010. The report shows overall GHG emissions in 2010 increased by 213 million metric tons or 3.2 percent from the previous year, despite the sluggish economy.

According to the inventory, approximately 77 percent of all GHG emissions derive from fossil fuel combustion. When emissions are analyzed on an industry sector basis, about 34 percent of total net GHG emissions (taking GHG emission sinks into consideration) derive from electricity generation, about 27 percent derive from transportation, and about 20 percent derive from industrial activities. Also, early results from the Federal Mandatory GHG Emission Reporting Rule (40 CFR Part 98) indicate that power generation and natural gas and oil production (leading to power generation) are the two largest categories of emitters.

Total emissions of the six main GHGs in 2010 were reported as 6,822 million metric tons of carbon dioxide equivalents, an increase of more than 10 percent compared with the 1990 figure. This change conflicts with the United States’ Kyoto Protocol pledge to reduce GHG emissions by 7 percent from the 1990 baseline by 2012. The Kyoto Protocol pledge is not enforceable because the protocol was never approved by the U.S. Senate, but as a member of the United Nations, the United States must report net GHG emissions to the United Nations Framework Convention on Climate Change.

Other significant GHG contributions listed on the inventory included

• methane emissions from natural gas systems, fermentation, and landfills
• N₂O emissions from agricultural practices
• SF₆ emissions from electrical transmission

These GHGs are important because each has a Global Warming Potential significantly greater than that of CO₂.

The inventory also tracks “sinks” that remove CO₂ emissions from the atmosphere. Compared with 2009, the amount of CO₂ estimated to have been removed from the atmosphere by renewed forests rose by nearly 2 percent in 2010, while the amount of CO₂ removed by cropland in the United States declined.

The EPA will undoubtedly use the information in the recent GHG inventory to develop future policy and, when it develops new rules, will focus attention on those segments most responsible for GHG emissions.

More Information

Click here to download the Executive Summary of the GHG emissions inventory.

About the Author

Marc Karell, P.E., CEM, is the owner of Climate Change & Environmental Services, LLC, a consulting firm specializing in air pollution, climate change, sustainability, and energy services for a wide variety of industrial and corporate clients. CCES and its technical experts develop successful GHG emission reduction programs for companies, buildings, and institutions. Most such strategies have economic benefits and a healthy return on investment.

Photograph: Distillation Columns by David Ritter, Phoenix, Arizona, U.S.A.

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