Wednesday, November 6, 2013

US GHG Emissions Declining Due to Increases in Natural Gas

According to new data from the Environmental Protection Agency (EPA), greenhouse gas (GHG) emissions are decreasing in the US. However, this is due in large part to increases in natural gas production. Extracting gas, particularly shale gas, releases methane which is a far more potent GHG than carbon dioxide.

Emissions from Power plants are a major component of national GHG totals as they are responsible for approximately 40 percent of US carbon pollution. According to the EPA report, US power plants saw their GHG emissions go down 10 percent between 2010 and 2012 and 6.3 percent between 2011 to 2012.

The report indicates that overall emissions declined by 4.5 percent from 2011 to 2012.

The EPA's Greenhouse Gas Reporting Program collects data from over 8,000 facilities in large emitting industries including power plants, oil and gas production and refining, iron and steel mills, and landfills. This is the third report of its kind from the EPA and it details pollution emissions and trends by industrial sector, greenhouse gas, geographic region, and individual facility.

The report attributes the decrease in emissions to the widespread transition from coal to natural gas for electricity. This report may seem to suggest a positive trend however, there are still very significant problems associated with natural gas. Although the report indicates that methane is also seen minor reductions (3.8 in 2010 to 3.1 in 2012), that number could have been significantly less if the US had not embarked on a nationwide hydraulic fracturing (fracking) blitz.

The proliferation of natural gas not only depends on environmentally destructive fracking, it also emits large quantities of Methane. While conventional gas also releases methane, a far greater amount of methane is released through extracting natural gas from shale. Together, fossil fuel extraction (including oil and coal) represents almost half (41 percent) of all US methane emissions.

Methane, which is one of the most potent GHGs and it is widely understood to be a more destructive GHG than carbon. Methane is more potent because it traps heat far more effectively than carbon. According to the Intergovernmental Panel on Climate Change (IPCC), over a 20-year time horizon, methane is 72 times more potent than carbon.

Approximately 40 percent of atmospheric methane comes from natural sources, while the remaining 60 percent comes from human activities including fossil fuel exploitation, landfills and biomass burning. Atmospheric methane reached a new high of about 1819 parts per billion (ppb) in 2012, or 260 percent of the pre-industrial level, due to increased emissions from anthropogenic sources. 

Although there is significant disparity in the assessments of exactly how much methane leakage we see at gas drilling sites, some estimates put that number at 9 percent or higher.

© 2013, Richard Matthews. All rights reserved.

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