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 Reducing non-CO2 GHG Emissions

While carbon dioxide (CO2) is the primary anthropogenic GHG emission, other GHGs are significant in quantity. During 2006, DOE reports that approximately 83 percent of total U.S. GHG emissions consisted of CO2 from the combustion and nonfuel use of fossil fuels. Other gases - methane, nitrous oxide, HFCs, PFCs, and SF6 - amounted to more than 1.1 billion tons of CO2-equivalent emissions in 2005.  These other gases - particularly methane and SF6 - offer many opportunities for reduction by the electric power industry.

Methane (CH4) is a potent greenhouse gas, having over 20 times the global warming potential (GWP) of carbon dioxide. Methane is emitted from a variety of natural and human-influenced sources. Human-influenced sources include landfills, natural gas and petroleum systems, agricultural activities, coal mining, stationary and mobile combustion, wastewater treatment, and certain industrial process.

Methane emissions account for approximately ten percent of total U.S. anthropogenic GHG emissions, second only to carbon dioxide. The five primary sources of methane emissions - landfills, livestock management, natural gas systems, coal mining, and manure management - together account for about 95 percent of U.S. methane emissions.

Sulfur hexafluoride (SF6) is a highly potent greenhouse gas used in the power industry for insulation and current interruption in electric transmission and distribution equipment. The physical quantities that are emitted are small, fewer than 1,000 tons per year. However, the GHG effect of these emissions is large, as the global warming potential of SF6 is 23,900 times greater than CO2. Because of this extremely high GWP, one pound of SF6 has the same global warming impact of 11 tons of CO2.  The U.S. emissions of SF6 is less than the equivalent of 20 million metric tons of CO2, less than one percent of total U.S. GHG emissions. Most of this is from the electric power industry.

Unlike CO2, where most emissions can be viewed as a co-product of combustion or calcination; most sources of methane and SF6 emissions are incidental emissions, being either accidental releases or related to variable biological or geological processes. The emissions are generally dispersed and the processes will often vary with site-specific conditions. In general, where emissions are a co-product of a specific activity such as fossil fuel burning, measurements can typically be made with a high degree of precision. Incidental emissions such as most methane and SF6 sources are, in contrast, variably related to an activity’s inputs, and are often spread out over time.

The management and use of methane and SF6 can significantly reduce the overall emission of greenhouse gases. Studies by U.S. EPA indicate that there are many actions that can be taken to reduce these emissions at little or no cost. There are a variety of ways that utilities can participate – either directly or indirectly – in reducing emissions of these greenhouse gases, including:

The Resource Guide pages to the left, identified as "Related topics in this section", discuss each of these methane and SF6 reduction activities in turn. The resources identified below are more applicable to methane management in general.

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Resources and links specific to individual topics within this section are listed separately for that topic’s web page. The Resource links shown below are more cross-cutting, and relate to non-CO2 greenhouse gases in general. Additional resources are provided for the specific topic areas indicated by the link bar on the left of this page.

Environmental Protection Agency, “Methane”
http://www.epa.gov/methane/index.html

Many companies in the U.S. are working with EPA in voluntary efforts to reduce emissions by implementing cost-effective management methods and technologies. This Home Page provides links to more information on methane and EPA's related activities, including science, emissions, mitigation costs, and voluntary programs.

Environmental Protection Agency, “Methane to Markets Partnership”
http://www.epa.gov/methanetomarkets/

The international Methane to Markets Partnership, launched in November 2004, committed the United States and 13 other countries to advancing cost-effective, near-term methane recovery and use as a clean energy source. The Partnership focuses on methane recovery and use opportunities in the agriculture (animal waste management), coal mine, landfill, and oil and gas system sectors. Since its launch, the Partnership has added multiple Partner Governments and private and non-government participants who work collaboratively to implement projects around the globe. Public and private sector organizations around the world are now working together with government agencies to facilitate methane reduction projects in agriculture, coal mines, landfills and oil and gas systems. This collaboration is yielding important benefits, including enhanced economic growth and energy security, improved air quality and industrial safety, and reduced greenhouse gas (GHG) emissions.

Environmental Protection Agency, “Opportunities to Reduce Anthropogenic Methane Emissions in the United States. 1993 Report to Congress," EPA 430-R-93-0012
http://www.epa.gov/nonCO2/reports/options2toc.html and
http://www.epa.gov/nonCO2/reports/order.html

A Table of Contents and Order Form are presented; only hard copies are available. Reports will be sent via U.S. Mail. Alternatively, reports can be ordered by phone at 1-800-STAR-YES.

Environmental Protection Agency, "Report on U.S. Methane Emissions 1990-2020: Inventories, Projections, and Opportunities for Reductions," EPA 430-R-99-013, September 1999
http://www.epa.gov/methane/projections.html

This report addresses the historical emissions of CH4 and presents EPA's forecast of emissions through 2020 for landfills, natural gas and oil systems, coal mines, manure management and enteric fermentation. The report also estimates the costs of reducing CH4 emissions from landfills, natural gas systems, coal mines and manure management.

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